Custom Vibrolux Reverb - Mark Moyer Mods

My tubes and parts have shipped...amp is disassembled, chassis upside down with 15" speaker baffle plugged in, leaning against the wall. I really want to go through these tube changes first. Last time I did it, I used Sovtek 5751's and the JJ/Tesla ECC81's in the pre-amp slots. What I read, however, is "short plate" 5751's or 6201's are just inherently quiet (made for hi-fi ap's), with the Sovtek 5751 being better used elsewhere than the pre-amp. It's a well-made rugged tube, probably best as the reverb driver. The ECC81's I'll slip into the phase inverter. Currently, have Sovtek 6L6WXT+ for power tubes, and I have a pair of matched Winged C's 6L6 standing by...

Quote:

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Originally Posted by twangmeisternyc

Surfcaster,

$28.50 @www.MojoMusicalSupply.com - for the 3 spring long delay tank...less than one of those fancy tubes you are using! ;-)

Not sure what the gain is on a 6201 (60%?), but a Sovtek 5751 (70%) might give you some boost as a V3 reverb driver. Surely, the Reverb cap mod is a half-way point to add some more tone.

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no no no... believe me 28.5$ is more than i usually pay for a preamp tube. if i don't remember badly i paid 15-20€ for 5 NOS 6201. Last tube i have bought :

http://cgi.ebay.es/ws/eBayISAPI.dll?...m=310007722515

IMO you don't have to pay lots of money for "matched 12AX7's" or "superclean logos" etc. i think this things are for collectors. what i do is have 2 or 3 trustful sellers, and be patient. when the tube arrives i take it to my tech for testing. sometimes a tube is bad, but in the global result it is a nice and cheap way to find tubes. since today i have had good luck... cross fingers!

Just an update...

You can get a CVR Service Manual @

http://www.schematicheaven.com/fende...lux_manual.pdf

And the 63 Vibroverb Owner's Manual @

http://media.musicalplanet.com/pdf/FEN302.PDF


In the parts list it describes component types and values. I made a mistake or two ordering my parts... but for mods I do not plan to do at first. Mainly on types of components..type of resistor, type of capacitor, etc. Look that document over well. Check wattage and voltage, etc. Also, R23 is listed on the Parts List at 18k ohms, ...but in my unit it is 47k ohm. R23, which takes both pre-amp tube anodes to ground, is also listed as METAL OXIDE type, 1 Watt. R37, in the NFB loop circuit, is listed as "FILM", not following the code, so, maybe it was supposed to be METAL FILM, 1 Watt. In my unit R23 and R37 look essentially the same, METAL OXIDE type. As a comment, if R23 were at 18k ohms, this pre-amp would have run REAL HOT!

Second, the Fender folks emailed me a '63 Vibroverb Reissue schematic and layout drawing. I thought they would want me to send a $10 check and letter as described on the website Support section...but I've had email and phone chats with them in the past regarding past and future purchases, I am probably in the database...nice gesture on their part.

Third, initial review of the 63 Vibroverb has the Reverb Cap, C16 listed as 3300pf (.0033uf) 400V. On the CVR parts list, this component is a 500pF, 1000V ceramic disc type, not a Silver Mica. I think Ceramic Disc is fine here as that Silver Mica is tough to find.

I am pondering whether one must change to BRIGHT ONLY Reverb to switch to the .0033uF capacitor for it to have full benefit. The circuit changes seem to be independent enough of that capacitor change, one 1/2W 220K ohm (R11) resistor going to 300V "X", the other, R35, 1/4W 220k ohm connecting the NORMAL channel back into the circuit ahead of the phase inverter. Both are a long way from the Reverb circuit mechanics. Would be nice to have someone else chime in on that question. Also, I think a value somewhere in between 500pF and 3300pF might be just fine if the effect is too much.

Fourth, the C20 shunting capacitor on the 63VV schematic is listed as 100pF, 1000V.

Fifth, The C11 BRIGHT channel filter cap @ 47pF, Ceramic Disc, 1000V is also a bit of an oddity in the marketplace should you wish to order a spare.

Sixth, the footswitch grounding scheme change must be from other older Fender amps...the CVR and 63 VV are the same on the schematic.

Seventh, over on the other forum, someone just had several of the mods completed and thought they were great.

http://www.fenderforum.com/forum.htm..._number=661747

Finally, I received my JAN-Philips 5751 tubes today, more on those soon.

I started the mod's yesterday...

First, let me say if I get yet another cut on a finger or thumb from struggling with getting the chassis out, I probably will need to give up guitar playing... ;-)

Lots of burrs all over, ... a bit surprised by that. Additionally, lots of hang-ups with the tolex and RF foil under the top panel board.

I went through a long series of tube changes. Where I ended up was V1,V2 Jan-Philips 5751, V3 Sovtek 5751, V4 Tungsol 12AX7, V5 the original Fender GT 12AX7, V6 JJ/Tesla ECC81, and V7, V8 Sovtek 6L6WXT+. As a final comment about doing the tubes, those Jan-Philips 5751's were almost impossible to get in, really buggers...

Where in the past when I de-gained the pre-amp with the Sovtek 5751 or the JJ/Tesla ECC81's, and did not notice much idle hiss reduction...I'd say the Jan-Phillips did give a proportional noise improvement. Also, adding the JJ/Telsa on the phase inverter helped again. Using the Sovtek 5751 for the Reverb Driver added a lot more than it's gain difference. Reverb really perked up. I would also say my Vibrato sounded better, not so much the chugging - more the smooth swirling.

My Jensen C15N speaker baffle is a lot deeper and a lot brighter than the original Jensen 2-10 Alnicos. I'd say BRIGHT channel using the Alnico's might even be less than the NORMAL channel with the Ceramic 15. Reverb on the C15N was actually very good, especially when perpendicular to the unit. In such a small apartment space, when directly in front of the unit I think the reverb cancels out, just the geometry of the walls makes it feel faint.

When it came time to make the footswitch ground mod, I was using the 2-10 Alnicos. I snipped the gray wire, leaving about a 1/4 inch, stripped and tinned the lead, and then secured it to V4 pin 2 along with the green wire. Not a big deal. I did notice that the popping when depressing the footswitches was less noticeable, I wouldn't say the pop had disappeared.

I did, however, get into a bit of Reverb Feedback during that session, most likely due to the placement of the loose tank in the unit, the effect of the Alnicos,... lots of potential reasons. In any case I could not go over 7.5, where before I could go to 10. I need to put the C15N baffle back in to see if the effect is recreated. I doubt the footswitch mod had a thing to do with it unless that 1/4" piece of wire I left standing became a super transmitter antennae.

I also had torn out a fair amount of the RF foil which I repaired with several layers aluminum foil and clear 3M high quality packing tape. I trimmed out and the reglued any unworthy tolex that was snagging the chassis, too. Sliding the chassis back in was much easier.

I received my components...and as expected a few of the resistors I'll need to reorder.

More as it happens...

I did a bit more today, switching speakers, tubes, etc. I mounted the reverb tank properly, ran the cables better, etc. Still having a bit of a reverb squeal as I approach "10". It came and went a bit, too. There were times "10" was fine.

My power here today was pretty terrible, we get a recurring buzz/transient fairly regularly that I have never figured out. It affects our phone, too...quite audible. Not sure if it is the building, pumps/fans/equipment cycling on and off, or if it is straight from ConEd. Maybe that is as much of it as anything else.

I would describe the Vibrato footswitch pop as being less, and now maybe the Reverb footswitch pop is equal where before it was negligible.

I plan to switch the footswitch ground back as original, and see what that does...

My notes are underlined and bold below:

Quote:

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Originally Posted by twangmeisternyc

Second, the Fender folks emailed me a '63 Vibroverb Reissue schematic and layout drawing. I thought they would want me to send a $10 check and letter as described on the website Support section...but I've had email and phone chats with them in the past regarding past and future purchases, I am probably in the database...nice gesture on their part.
Could you send me a copy of the 63 Vibroverb Reissue schematic?? I'd love to see it.

Third, initial review of the 63 Vibroverb has the Reverb Cap, C16 listed as 3300pf (.0033uf) 400V. On the CVR parts list, this component is a 500pF, 1000V ceramic disc type, not a Silver Mica. I think Ceramic Disc is fine here as that Silver Mica is tough to find.
The idea behind using a Silver Mica is that it will sound better. Try both, you will probably notice a big difference.

Silver Mica 33pf

Fourth, the C20 shunting capacitor on the 63VV schematic is listed as 100pF, 1000V.
I don't think it matters. Someone else mentioned that its not likely to have 1000v running anywhere through this amp. 500v should be fine. Has worked for me so far.

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Quote:

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Originally Posted by twangmeisternyc

I did a bit more today, switching speakers, tubes, etc. I mounted the reverb tank properly, ran the cables better, etc. Still having a bit of a reverb squeal as I approach "10". It came and went a bit, too. There were times "10" was fine.

My power here today was pretty terrible, we get a recurring buzz/transient fairly regularly that I have never figured out. It affects our phone, too...quite audible. Not sure if it is the building, pumps/fans/equipment cycling on and off, or if it is straight from ConEd. Maybe that is as much of it as anything else.

I would describe the Vibrato footswitch pop as being less, and now maybe the Reverb footswitch pop is equal where before it was negligible.

I plan to switch the footswitch ground back as original, and see what that does...

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I switched my footswitch ground back to the PCB connection. I think the CVR that Mark Moyer worked on was an early model (1995-97) and had some slight differences from the CVRs being built now.

Check your Silver Mica info, it's .0033uF (3300pf). Right now I have a Ceramic disc and an Orange Drop to try. When I went looking, only Cornell Dubilier made a Silver Mica at that 3300pf, and the only places to purchase were more main line OEM suppliers with $300 minimum buys. It was also a non-stocked item. I'll keep looking.

And, those higher Voltage ratings are just a safety factor. Some caps get really pounded...just like the Reverb Driver tube gets pounded.

Also, I found a link that described designing solid-state reverb circuits, and in the article it gives a range of cap values. Right now, the CVR is 500pf, which is a low value by similar measures. This article describes 1500 to 10000pf (once you do the math), as the working range.

http://sound.westhost.com/project34.htm

Lower values give that Classic Fender booming Reverb sound. Higher values are supposed to give an added "shimmer" like Stevie Ray Vaughn.

The .0033uF (3300pF) is in the lower of that working range, and is common to a lot of Fender spring reverb amps.

I'll switch the ground on the footswitch back and give it a another listen. I think the schematics are probably correct. Both are the same, and Mark's note describes his scheme as being from "earlier Reverb" amps.

My issue as delivered with the CVR was if I left Reverb on, and switched off Vibrato, I got a fairly noticeable pop. If I turned reverb off first, not so much. The mod is a pop either way, just less noticeable.

Oops, yeah I looked at that wrong. Here is the actual cap that I used to replace the ceramic disc in C16:

Orange Drop .0033uf

I hear orange drop caps are known for their great tone. However, I have no idea if they are preferred for use in a reverb circuit. Either way it sounds great to me and it hasnt blown up or anything.... yet. :)

Orange Drops are used a lot,...they start to have issues at very high frequencies. Silver Mica are the most suitable. Ceramic do high frequencies well, but drift, vary, etc. more so than the other two.


http://thetubestore.com/parts.html

These folks have values either side of that 3300pf. Nice guys, I order my tubes there.

Deleted, added above

Interesting. I may order a few different ones and try them out.

I returned the footswitch ground back to the printed circuit board, and it seems the reverb feedback issue is better, more tolerant. I did everything without plugging in a guitar, but I did enough switching and swapping and plugging and unplugging yesterday to say without all that the factory grounding scheme may be a bit more stable.

There is more resistance to ground going to the V4 pin2, it is fixed/static, but in the factory scheme it passes through the REVERB potentiometer itself, and depending where one has it dialed up to, more so through the C16 capacitor. The pop in the mod is consistent, as one would expect it to be...in the factory scheme it varies depending on where the knob is set.

The REVERB pot is linear reverse, so when one dials higher it become less resistant, giving more reverb, and at maximum, there is both the pot and the 82k ohm resistor to ground for the footswitch. So, at the highest settings, the footswitch ground is completely through the pot.

Maybe the ground to the V4 pin2 is just more microphonic...

I'll give this all another go at some point.

As another footnote, I made no effort to put the tube holders over the tubes during all these tests, and I did have the 5751 in as the reverb driver. It has more gain. I was getting feedback yesterday with an AT7 so I do not think it was the critical path.

Also, when de-gaining the pre-amp with 5751 or ECC81's max volume is about 7, after that you begin to oversaturate the tube. The amp was designed to deliver more power than the 5751 or ECC81 can use.

i keep looking at this thread everyday as it is very interesting. i have no time now to do the mods as i am restoring a ruined SG that has been given to me. maybe i will start next week while i let the glue curing her neck.

anyway, and for the pop when disconnecting the tremolo, i remember mine had a very noticeable one. let me tell you that i had to convert my amp from 120V to the 230V we have in Spain. my tech did the new trafo and that pop was even louder! but he discovered that the 120V trafo had a capacitor embebed in the coil doing antiparasitics so he started playing with the values of the cap till most of the hum and the whole tremolo pop were dissapeared.

this afternoon i have been rehearsing with the amp... i love this amp men! i almost doubt it can improve with the mods... and i forgot to check the reverb tank! let see next thursday.

Just another update....

Been playing all my various guitars these past couple days. I really like the tube changes. Whether NORMAL or BRIGHT, 2-10 AlNiCo or 1-15 Ceramic, with or w/o REVERB or TREMELO...everything sounds better.

It's still the honeymoon, of course, but the de-gained pre-amp matched to the pumped up REVERB is great, and however/whatever with the de-gained phase inverter...the TREMELO just has that dreamy thing going on. I changed the Fender GT 12AX7 for a Tung-Sol as the Tube Oscillator when I was testing the Reverb Feedback on Sunday morning...so that is the only other change since those notes.

I need to grab a few tools this weekend to start working the other mods, I have them in storage at my father's house. Next is the Reverb Capacitor. This will be curious as the Reverb right now sounds pretty good.

I re-ordered the 82k, 47k, 39k, and 6.8k 1W MOS resistors, and along with ... some of those "addictive" NOS GE tubes, the 5751 and the 6201.

I have the footswitch ground back to factory schematic, no real issues if I remember to turn reverb off first before tremelo when both are on...

One last thing, there is an additional fuse on the PCB board not well listed on either the CVR schematic or parts list. It is a 5*20mm 10A 250V fast blow. Do your units have this fuse, too?

Yes, mine has that fuse too.

Could you give me a list of all the tubes you have tried at this point and up to your current setup? I'm ordering tubes tomorrow - currently using all of the original tubes except for V3 I have a mullard 12at7 nos that has worked out nicely.

As delivered it was all Fender GT, except as I recall, there was another AT7 in the Phase Inverter. I bought my unit "new", with a warranty, etc....but it was a special price, obviously a returned open box unit. My unit uses the WHITE bias GT 6L6B's and those were Sovtek 5881WXT production.

I bought a bunch of Tung Sol's 12AX7, the JJ/Tesla ECC81, and the Sovtek 5751 based on my internet searches, reading stuff, etc. Also, a bought a matched pair of the Sovtek 6L6WXT+ and the 6L6 Winged C's. All these tubes were for a point-to-point retro-fab Princeton Reverb high power amp I had ordered. However, I rejected it, sent it back...and had a pile of tubes!

For the CVR, I had been running Tung Sol's in both pre amps, the Fender AT7 for the Reverb Driver, then Fender AX7 through to the power tubes. I had the Sovtek WXT+ bottles I had ordered in for those, and those were screened for their bias at the vendor.

As I mentioned a while back...I've tried the JJ and the Sovtek 5751 as preamp tubes and reverb drivers, not sure I had ever used either for a phase inverter...

Now, thinking about, such a high gain pre-amp with those Tung Sol's would have been what I was hearing...an amp ready to SCREAM!

Right now, I have the Jan-Philips 5751 in for both preamps, a Sovtek 5751 in for the reverb driver, a Tung Sol AX7 in for reverb recovery and tremelo oscillator, and a JJ ECC81 in for the phase inverter. I have left the Sovtek WXT+ in for power tubes.

We need to keep in mind, once the NFB loop mod is done, the power to the pre amp tubes changes...so, the effect of de-gaining the front end will be different.

Hey Fezzy,

I re-read some of your earlier posts...it seems you changed the Reverb capacitor before separating the two channels. Did you notice any added hiss from doing that?

I think that 500pF value on the CVR was probably chosen to keep any added hiss (from having reverb in both channels, both channels wired together) from becoming a "sonic hiss machine". What do you recall?

Otherwise, that .0033uF cap is standard fair for lots of the 60's era spring reverb models...

Nope, I dont remember any added hiss at that point. The only noticeable change was the 'thickness' of the reverb.

For tubes, I'm going to go with the Tungsol 12AX7 mostly and I'll order a couple of the Jan-Phillips 5751 so I can try out the degaining trick and see which I like better. The Sovtek 6L6WXT+ sound like the way to go for this amp.I'll post another update once I try out some different tube combinations.

Also, I'm gong to order a pair of Weber 10F125 speakers. I'm really excited about getting those in the amp. Currently, I have the stock Jensen P10R (25w 8ohm) that came with the amp. They sound good at low-medium volumes but when really pushing the amp they sound so damn muddy-ish I can't imagine anyone enjoying that sound. They just dont seem to handle low end very well at all.

What speakers are you guys using?

Also, I found on another thread a guy using a combination of Weber F150 + A125. That seems like a great way to take care of the super high-end and pretty deep low-end. Thoughts / Suggestions?

Most like the Weber line of speakers. The one you selected is a ferrite, so that is a big difference right there. Those Eminence Ragun Cajun's show up in a lot of threads, too.

My other baffle is a Jensen C15N 4ohm 15" Ferrite Ceramic...very 60's in its design. Definitely, higher highs and lower lows, real clear...my guess is it may only start to push a bit at loud volumes...not sure it would break up at 40 Watts...

That mismatch between speakers was used a lot back in the day. Trying to remember which makers actually did that right from the factory - not as uncommon as you might think at first glance.

Also, remember to wire the pair pos-pos, neg-neg when you are switching things all around - if not, you get the cancel out effect with one starting forward and the other going backwards when you strike a note. Take a digi picture first!

Quote:

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Originally Posted by twangmeisternyc

Also, remember to wire the pair pos-pos, neg-neg when you are switching things all around - if not, you get the cancel out effect with one starting forward and the other going backwards when you strike a note.

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Will do. I once wired a 4x12 cabinet incorrectly so the speakers where out of phase with each other. It feels like your brain is being ripped apart from the inside. Haha :)

All my parts and tubes arrived in the mail this afternoon. Ordered a couple other caps for the reverb circuit, too, a 1000pF and a 2200pF ceramic disc.

Need to go get my multimeter and strippers, some wire, and also try to find those small fuses so I have a spare. More on the mod's next week.

Can you post a clip of your amps with the mods done?

There's a guy on the local craigslist selling one of these that I might be able to make a trade for (and perhaps eventually trade for a DRRI). My biggest complaint about the Vibrolux was the hiss when the tremolo was on.

Thanks!

I have no means to post sound clips...nor do I think you could make any determination from one.

Hey Fezzy,

I was able to collect all my stuff this weekend, and was also fortunate that my dad had some 3M aluminized foil just like the RF shielding seen across the underside of the top of the cabinet.

Those 5*20mm, 10A, 250V fuses aren't easily found retail...but this link should be helpful if you want to order spares.

http://www.alliedelec.com/Search/Sea...BA1C006928E17F

There is no minimum order...I placed mine this morning, will be a couple days before I expect to receive via USPS mail.

That fuse is a funny rating, too. It must be taking into account a maximum failure of the power tubes/transformers as well as adding the power from the tray of storage capacitors.

KCWM - your best bet would be to play one for yourself. In the end its just another good sounding fender amp. Everyone has different playing styles so what sounds good to me might sound lame to you and so on. Definitely not a good idea to buy a piece of equipment because someone else sounds good through it. :)

Thanks for the link twangmeister! I was looking for one of those fuses over the weekend and had absolutely no luck. How are the other mods coming along?

I'll get onto the Reverb Cap next...hopefully tomorrow.

I need to stare at the schematic again regarding splitting the two channels. I need Reverb on the Normal channel for some of my guitars...not ready to give Normal up yet.

Jumpering the Bright cap in and out is a possible solution, but I think there may be an elegant way to jumper the Reverb instead between channels with a switch.

We'll see. As we both know, in a live playing room environment, none of this really matters. The idle hiss is a non-issue short of a quiet setting, mic-ing, or recording...

What is nice about the concept of the amp is that you can get both the tubes to go over-the-top, as well as the speakers...so, those nuances are part of the sound in just a single combo.

What we are doing is steering things a bit for different situations. I have 3 acoustics with piezos, and 3 electrics...every one with a different pick-up and a different sound...so, my ideal plan is to know all the permutations...96 of them. Changing the tubes around last week changed my settings...still working through those new combinations.

Fezzy, I can't play one with the mods done. Of course, I can play one WITHOUT the mods, but I've already done that...so it'd serve no purpose.

I've played on a CVR and made the, apparently, controversial statement that it sounded better than the DRRI. But, it was noisy. If the mods are made to reduce the hiss, I'd like to hear clips of it.

I'm not asking people to sound good. I just want to hear the difference the mods make. The memory of the hiss is still familar.

hi guys. i am not sure but i have understood that 5x20 250V 10A is a difficult fuse to found for you. is it right? if it is so, you will only need to give me a shipping address, as this is the most common type of fuse here in Spain. i will gladly send to you as many as you need.

I got on to the Reverb C16 capacitor mod this early afternoon. Took a bunch of photos, wrote down wire colors and connections for all the "fast-on" spade connectors, etc. Those "fast-ons" were really tight...I had to loosen those I needed to unplug first with a small screwdriver...too tight to just yank off.

7 screws to release the PCB...all the Vol, Treb, Bass, Reverb, Speed, Intensity pots...1 ground wire screw. I only needed to release 3 of the "fast-on" wires to have enough access to remove and replace the cap.

I used a Ceramic disc 3300pF, 3000V capacitor.

So far, I have only tried just my little 1916 Gibson L1 with a piezo...LOTS more reverb, no real added hiss compared to the other 500pF capacitor. Sounds great. Need to work through all the other guitars now...

Thanks for the offer Surfcaster...I think this source I found should be OK...they sent a shipping notice this morning for the 5*20mm 10A 250V fuses

The Byrdland sounds great, too. The depth of the Reverb compared to factory tubes and capacitor is an order of magnitude better. I think the higher gain Sovtek 5751 as the reverb driver is helping a lot.

Have now played all but my old Epi Emperor through the 2-10 AlNiCo's, it's out for a new nut and a little fretwork. Only the Gretsch sounds a little in need of something...not bad, but the TV Jones pups and those unique controls might have liked the higher gain pre-amp. I'll try it first when I go through the same progression with the C15N baffle.

The Gretsch sounds great through the C15N, must have been the way I tested before...

My next step is the shunting capacitor, C20, I'll get on to that over the weekend. I'm hearing a little something, whatever a "parasitic" is, more so just a ringing that seems to want to lead to a feedback moment - but, doesn't. I think from Mark's description that C20 is fairly benign...more so some command and control element...we'll see. ;-)

5*20mm 10A, 250V fuses came late yesterday...I think now I have a lifetime supply of most everything ever needed to manage a CVR, mod a CVR, OR EVEN MAKE A CVR. ;-)

Thanks for all of the updates twangmeister! I'd like to see some of your pictures just for comparison purposes. Sorry I havent posted in a while. I'm waiting on my tube order to come in.

Also, I've experienced that ringing you are talking about. It went away about 2 weeks ago so I never had a chance to try and track down the cause.

I put the next mods on hold this weekend as I decided to sell something on Craiglist for which I needed the amp to function. I also wanted to get the Epiphone back from the shop and give it a run through with the new set up.

I spent a lot of time comparing the two schematics in the interim, hoping to see an easy way to separate the channels, and make reverb selectable to either. While it is certainly do-able...I'm seeing a few limitations. The easiest is to work the Moyer mod with a DPDT switch for the reverb lead...and at the same time disable the other channel completely. So, it is a BRIGHT channel reverb only, and the NORMAL without...or...NORMAL with reverb and BRIGHT disabled. I am still staring at it, but I think that is the safest. I do not want it to be so complex I cannot even remember! There are a few spots that switch can be mounted, it doesn't need to be all that big.

Also, the C20 shunting cap, and the R23 resistor both would seem to help reduce the idle hiss if I foregoe the Moyer reverb mod. C20 adds a little "river" between and ahead of the two 6L6's that allows a balance of power on the very low spectrum should one side get well ahead of the other. R23 determines how revved-up the pre-amp gets, as well as affects the mix ratio with the reverb. Higher ohms should add headroom and more reverb as I see it.

I like what I am hearing right now, and I do not want to be tearing this thing apart 6 times just because I can. My guess is the integrity of the assembly was conceived with only a couple interventions into the PCB and other components in its lifetime...it is not built like a 50's RCA TV.

Only other note is I put a GE NOS 6201 in for the Reverb driver, essentially bringing the gain back down to factory settings...it's a little warmer than the Sovtek 5751. I also put a GE NOS 5751 in the NORMAL channel pre-amp...still comparing that to the JAN-Philips 5751.

I did what I thought was an interesting test this morning. I went through a series of tube movements for V1 and V2, listening for idle hiss and then giving full volume. What I wanted to discern was where the noise comes from. One might think that without a pre-amp tube it in, a channel wouldn't even make a whisper. WRONG!

The end of the story is the BRIGHT channel is relatively quiet, and the NORMAL channel is the majority of the hiss. From the schematic, the fact that the NORMAL channel V1B socket 6 gets powered via the V2B socket 6 by a jumper, and not straight from the PCB board via the "X" source voltage used in the Vibroverb and the Moyer mod seems to be it. That jumper wire, and the relatively low resistance through R22 and R23 appears to be the noise.

I think the GE NOS 5751 is quieter and a more full tone in the NORMAL pre-amp. Somebody on another board suggested it...I agree.

Hey Fezzy,

I was laughing out loud at myself yesterday...it's like 15 degrees F outside, wind howling, both radiators full blast, my room humidifier full blast...I can barely hear myself play at my regular settings, yet, I'm trying to reduce the idle hiss to a church mouse squeak!

I'm going to do the R23 and C20 mods next...more on those soon.

I did the C20 shunt using a 100pF, 3000V Ceramic disc capacitor, and changed the R23 value to 82k ohms 1W Metal Oxide resistor this morning.

Results so far are what I expected...feels more de-gained, reverb is stronger. I'm using the 2-10 AlNiCo's right now, and have tried the Strat Plus and the Byrdland...both aren't quite as shrill in the BRIGHT channel, so, maybe I would also comment that some of those "overtones" or "parasitics" are more tame.

I had to release a few more of the "fast-on" connectors to be able to get to C20...and I am a little surprised at how light gauge all of the input jack and potentiometer wires are...they look very easy to break, and just from being bent over a couple times like how they act while disassembling and reassembling the chassis.

I'm going to play my CVR like this for a while...since I cannot really go to higher volumes in my apartment, and I'll wait until I get more space to "turn it up" before proceding on any other mods.

I'll add more comments as I have them...

I've ordered a bunch of tubes today. When those get here I'll post updates on my different combinations and results.

All of those white wires that run from the main board to the daughter pot boards I've broken and had to resolder. Since I know I'll be taking this thing apart very soon to install the bias pot I'm going to replace nearly all of the original wires with some good solid silver core wire with cloth wrapping. I can't believe how crappy the stock wire is in these amps. Its pretty amazing. Some of the wires will pop off if you look at them wrong. lol

Recently I've been playing the amp at loud volumes and have come across a few weird static sounds here and there... Not sure what it is yet but I'll take a good look around next time I take it apart.

More updates soon! Keep us updated on your progress twangmeister.

I am a happy camper. I put everything back together properly this morning as if from the factory. I think I addressed my initial peeves...understanding the REV/VIB foot pedal "pop", the idle hiss, and the quality and amount of reverb. Three interventions, and it still all works!

Trying to keep the volume down for the "neighbors" has always been a priority, but I can gauge the component and tube changes pretty well. A lot of times I play with just the guitar volume slightly on, and the amp volume at say 2.5 to 3...and that gives one kind of sound. But the more full, chimey sound certainly comes the other way...guitar volume full open, and the amp volume "at maybe" 1. Very full and resonant, and I know it gets better if I let it go higher.

The Strat Plus with the Gold Lace sensors is just loving this new set-up. The 2-10 AlNiCo's are much happier with the de-gained circuitry and tube selections. I have more reverb at 3.5 than I did before at 10. Those in-between, position 2 and 4, pickup positions cannot be any more fun...clean, true, nice rock-a-billy/bakersfield tone. And really, really quiet.

I've opt-ed for the guitar volume to be at about 80%, leaving a little bit of something if I need it, then having the amp volume set as loud as I think the people "upstairs" can tolerate!

IT SOUNDS GREAT!

Quote:

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Originally Posted by twangmeisternyc

The Strat Plus with the Gold Lace sensors is just loving this new set-up. The 2-10 AlNiCo's are much happier with the de-gained circuitry and tube selections. I have more reverb at 3.5 than I did before at 10. Those in-between, position 2 and 4, pickup positions cannot be any more fun...clean, true, nice rock-a-billy/bakersfield tone. And really, really quiet.

I've opt-ed for the guitar volume to be at about 80%, leaving a little bit of something if I need it, then having the amp volume set as loud as I think the people "upstairs" can tolerate!

IT SOUNDS GREAT!

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hi twangmeisternyc. you seem sooo happy with the result of your work. as i told you, it is a bit difficult for me not losing at some point because i can't understand the whole sense of some phrases in english. would you do a little summary of the mods you have finally done to your amp? thanks!

Let me try to make it easy...

1) I tried the footswitch ground mod, but then returned to the factory way. So, I did not use this mod.

2) I changed C16, the "reverb cap", to 3300pF, 3000V ceramic disc from the factory value of 500pF, 1000V ceramic disc. This made for a lot more reverb, and a lot more depth of sound. 3300pF is the standard value in most of the early 60's Fender spring reverb amps.

3) I added C20, the capacitor shunt between the two Power Tubes, using a 100pF, 3000V ceramic disc capacitor. This believe this change allows for over flow exchange of power on the low frequencies between the two tubes, preventing one tube from working too hard when the other is available to do more.

4) I changed R23, the primary resistor measuring power to the pre-amp tubes to 82k ohms 1W Metal Oxide type from the factory setting of 47k ohms 1W Metal Oxide type. This change reduces the power to those tubes, essentially de-gaining the pre-amp.

My tube selections are as follows:

V1- GE NOS (jan) 5751
V2- Jan-Phillips 5751
V3- GE NOS (jan) 6201
V4- Tung Sol 12AX7
V5- Tung Sol 12AX7
V6- JJ/Tesla ECC81
V7, V8- Sovtek 6L6WXT+

Quote:

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Originally Posted by CzarSketch

oh and as for the '63 vibroverb, this basically converts it to that. there are a few other differences but not many. enjoy your VV!

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uh... that GZ34 is a pretty substantial difference.

Quote:

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Originally Posted by twangmeisternyc

Let .

3) I added C20, the capacitor shunt between the two Power Tubes, using a 100pF, 3000V ceramic disc capacitor. This believe this change allows for over flow exchange of power on the low frequencies between the two tubes, preventing one tube from working too hard when the other is available to do more.

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This is just to prevent parasitic oscillation on the output stage. Doesnt have anything to do with how hard the tubes are working. Too high a value here and you'll lose high end.

I got my new tubes in and tried a ton of different combinations. Here is what I ended up with and am pretty content with at this point.

V1: Jan Phillips 5751
V2: Tung-Sol 12AX7
V3: Mullard 12AT7WA
V4: RCA 12AX7
V5: RCA 12AX7
V6: RCA 12AX7
V7, V8: TAD 6L6WGC-STR

I decided to change R23 back to 47k. The added headroom from Moyer's suggested mod is not beneficial to me and I think the amp sounds better when the preamp is hotter.

I've yet to install a bias pot. I will soon probably but Mark Moyers description of how to do it doesnt make a lot of sense to me. I've read it 10 times and its still confusing.

I've been playing my old 1916 L1 Gibson and the 1940 Epi Emperor a lot the last couple days through my new LR Baggs Para Acoustic DI and into the -6db Normal input. It has taken a little while to dial in the best settings...but, wow, they both sound great.

Reverb at about 3, 2-10 AlNiCo's, gain set low, a little more presence on the Gibson than on the Epi, a little more bass on the Epi versus a little more treble on the Gibson...it's like a concert hall sound. Every nuance, real clean.

As said before, its nice to know we have flexibility..and when you want it "hot", that's available...and when you want it soft, that's available, too. And even if it is just a tube change.

I really like the way the Strat Plus sounds, too...played that for about an hour yesterday. The Gretsch in this set-up with the 2-10's likes the straight up open pickup settings the best..and the plain strings with the rocking bar bridge... it jangles a bit more.

Not sure why I say that..I think the Gretsch likes the higher efficiency ceramic magnet set-up on the 1-15 baffle. I need to switch back over and give that some more time.

Just like before when I said it...the Gretsch likes the C15N baffle a lot more in the new arrangement. More distinct sound variations on the tone switch, and less of the plain string jangle...back to more the "attenuated-muted-yearning" coming of the rocking bar bridge. I get less reverb at the same settings using the Gretsch as well. Still trying to figure that one....

The Strat Plus always liked the 2-10 AlNiCo's better...but now the difference is even greater. It sounds rather crappy with the 1-15...noisy, thin, yeeetch!

I plan to order the extension cabinet this next week to make my Vibro-Lux STACK. I think that best before I start cranking the volume higher, making more mods, ...plus it will be a lot easier to switch between speakers.

I think I am starting to wear out the grill cloth on the corners every time I switch using my current method two baffle set-up. And I want to hear the two speaker sets in combo...bass of the 1-15 hovering the floor, the 2-10's angled back into the ceiling. And I want to hear it all really LOUD!!!

Put on order from Mojotone...hopefully here by mid next month.

Hey Fezzy,

My extension cabinet order from Mojotone has shipped, once I get back from holiday I'll get you a couple pics of my "Vibrolux Stack". Knowing that when I use both the 2-10 AlNiCo's, and the 1-15 Ferrite in tandem I'll be at 2 ohms...I figured de-gaining the pre-amp by putting R23 at 82K ohms would be a good thing. I hope this comes together...been planning for over a year now.

Mojotone did a great job...just really clean, well thought out work. Working through the wiring connections, etc., need to finish a couple speaker cables...

Also, looking for a nifty way to rock the CVR back a bit w/o using the tilt back legs... probably a couple small black rubber wedge wheel chocks or door stops, maybe a rack...

UPS did try to spoil everything by gouging deep into the shipping carton, but "this time" I got lucky... I guess.

Hey Fezzy...you still checking these posts? Tried to send you a few pics, ... your email addy failed.

TUKI covers on order...very, very pleased with the combined extension cabinet sound. Clean and true, quiet...

hey twangmeisternyc,

Would love to see some pics. Send to fezzyis@gmail.com

Glad to hear your rig is working well!!