Silverface Fender Pro Reverb Problems- Rectifiers- Tubes

[Reeltarded]

The zener dropping string will do it all for a few dollars, too cheap not to try. Way less intrusive, yah.

[caveing]

Hey, thanks for the input guys!

the zener diode is the cheapest I know... I dont know about less intrusive, conisdering I should probably drop it what more than 40v as the listed voltage off the plates is 437v on the schematic.

wouldnt that get hot as hell?
and wouldnt the correct transformer for my desired rectifier be a bit more natural? maybe i could indulge in some mercury magnetics mojo? (not really)

I'm just playing devil's advocate here

Also if I got a new transformer, wouldnt I then be able to use a vvr to adjust headroom or use different rectifiers like switch between SS and GZ34?

I'll take that recommendation to just do the zener drop...
anyone else care to voice an opinion here?

Thanks!

[caveing]

oh yeh... and can anyone confirm that the early silverface power transformers are different than the blackface? even though they both have the same model number!

is this info correct?

[billyz]

Yes, They are different. The Later Silverfaced ones are designed for the 5u4 and run high with a GZ34. I see quite few siverfaced amps with very high volts and they are running GZ34's when I install the correct 5u4 the voltages come right into spec( considering the natural variances and modern AC ( usually higher than 117VAC ) .

A good PT should run you about $100 . Mercury has several specifically for lower voltages . They are a bit more, but I like them.

Z

[caveing]

Yes, They are different. The Later Silverfaced ones are designed for the 5u4 and run high with a GZ34. I see quite few siverfaced amps with very high volts and they are running GZ34's when I install the correct 5u4 the voltages come right into spec( considering the natural variances and modern AC ( usually higher than 117VAC ) .

A good PT should run you about $100 . Mercury has several specifically for lower voltages . They are a bit more, but I like them.

Z

Word- I'm pretty underversed in transformers... but arent mercury's a lot more expensive than that? And wouldnt spending on a mercury be better for the output tx?

besides that stuff- I guess I need to know what to look for in a transformer... i looked last night and saw that mercury had some power tx's with different voltages.

what voltage would I need for my particular situation? I guess I'd need a true blackface pro reverb power tx to run the GZ34 properly? right? Or maybe even a little lower so I could possibly run an SS rectifier without getting too high?

Anyone tell me what particular numbers or options I'd look for? I'd be more interested in something that wouldnt cost as much like a heyboer, but i know mercury has quite a few options available.

Thanks so much!

And sorry for making this simple matter such a long topic!

[billyz]

Mercury mags will run you more than that. But you can find others for less. If you want to run with SS diodes and maintain about 450vdc you might consider a MM lower voltage PT. or resort to a zener diode string off the center tap( you need to account for the heat though).

[caveing]

So I just realized that when I only plug in v1 and the PI preamp tubes (and just use the normal channel) I do not get the crackles and pops! I also found a source of some of the microphonic sounds- a brand new accutronics reverb tank as well as my reverb recovery tube. So the crackle must not be in the phase inverter, power section, 1st tone stack and gain stage, pots, jacks, switches...

My bright switch did decide to do its crazy tone generator thing... When I start playing loud on the vibrato channel and I kick up the bright switch (i normally dont use it, so I hadnt considered it as a possibility) it sometimes starts to distort like its feeding back real bad, and I get this awesome nasty sound, and then it turns into a wave generator type of sound that I can control the pitch of with my volume knob. as I turn the volume up it gets higher pitched (IIRC) and when I turn it down it gets lower in pitch... Could this be the source of my rice krispies? I suppose I can just disconnect it, right?

Also, as I mentioned above I replaced the 1st input jack of my vib channel's mixer resistor with a 2k resistor, but I left the 2nd inputs resistor at the stock 68k... could this be it? I used a new metal film resistor...

And the final difference- I used polystyrene caps in the reverb channels treble tone stack 250pf cap and all the 500pf reverb coupling cap (?)... they are rated at 500v, but they also have pretty dang thin leads. I do like the way they sound better than silver mica's (quite a bit better actually) could those thin leads be doing it?

I resoldered all the preamp tube pins (or solder joints or whatever), and i've been checking every connection... I cant find anything with my poke test...I've replaced and tested tons of components at this point or I wouldnt be asking here... just kinda sick of doing it... I'm thinking its something new that's causing the problem though at this point.

Any direction possibly? I'll be working on it in the meantime.

Also looking for info on the differences between the power transformers between early silverface and late blackface and wondering what transformers would be a good fit for my particular issue? Maybe an article that explains transformers and how they work in amp circuits... that'd be really helpful.

I'm also interested in anyone that has used a VVR in a fixed bias amp or a fender bf or sf in particular. Do these work well as a type of master volume? It'd be cool to have as I am possibly moving to an apartment in the near future. saving tube life and getting good tone at low volume would be killer!

Thanks a bunch for all the help! You guys have been awesome!

[rp]

You should listen to Billy and use a 5U4GC, zeners or new PTs seem like an awful lot of trouble to just get back to where a 5U4G takes you. A zener is used when you have no other choice, it adds heat and is just something else to fail and NOS 5U4s are cheap. I'd spend the dough of a MM PT on NOS tubes, especially RCA or GE outputs.

I did exactly what you did to a SF Super Rev long ago when I though filling it with Holcos and MIT caps was genius insight - sounded like dog poo for guitar but turned into a nice funky bass amp. I sold it to a friend cheap. Wish I could go back and set it right with what I've come to learn, which is:

With old Fenders shotgunning the CCs with CFs or MFs skews the tone and makes them bright, cold and hard.

Replacing the coupling caps w/ fancy modern hifi caps reveals to much of something and also skews the tone - stick to good enough 150s or 6PS, the later a little clearer, brighter (can't say about Sozos / Jupitors). Some stock SF amps sound really great so those brown or blue turds aren't really the problem.

If you want it to sound like a BF you need BF voltages, don't use a 5AR4. I can't say if rectifiers have tone and the 5U4G isn't true BF, but I do know that the wrong voltages affect tone.

Replacing all the disc caps in the Vib and Rev stages with films screws up both the tone and the vib and rev sounds. I stubbornly kept doing this and always hated the results. Stick with discs, in fact if the rev and vib sound good from the start leave the original discs.

BTW for a BF conversion the orig Fender wiring layouts were actually a precise guide for the assemblers on how to dress the wires, if you follow the BF layout you can likely pull all the extra SF junk and have a quiet stable amp without the need to run a ton of shielded wire. That is, don't just use shielded wire everywhere unless you need to, that stuff robs tone.

[rp]

Also, A VVR or master will not get you to bdrm level on a 50W amp, there is nothing in the world you can do to make a Pro Rev playable in an apt. unless you live in a squat, but then someone can always unplug you from the streetlight I've yet to try a VVR, but been reading old posts and have yet to hear about the results in an amp with Rev and Vib, I would ask up on this. For an apt even a Champ is too much. Buy some little SS practice amp off Craigslist, and for days when no one's around build a 5F1 Champ and rock out. Don't bother building a 5W amp with a master just use a distortion pedal.

[caveing]

You should listen to Billy and use a 5U4GC, zeners or new PTs seem like an awful lot of trouble to just get back to where a 5U4G takes you. A zener is used when you have no other choice, it adds heat and is just something else to fail and NOS 5U4s are cheap. I'd spend the dough of a MM PT on NOS tubes, especially RCA or GE outputs.

I did exactly what you did to a SF Super Rev long ago when I though filling it with Holcos and MIT caps was genius insight - sounded like dog poo for guitar but turned into a nice funky bass amp. I sold it to a friend cheap. Wish I could go back and set it right with what I've come to learn, which is:

With Fenders shotgunning the CCs with CFs or MFs skews the tone and makes them bright, cold and hard.

Replacing the coupling caps w/ fancy modern hifi caps reveals to much of something and also skews the tone - stick to good enough 150s or 6PS, the later a little clearer, brighter (can't say about Sozos / Jupitors). Some stock SF amps sound really great so those brown or blue turds aren't really the problem.

If you want it to sound like a BF you need BF voltages, don't use a 5AR4. I can't say if rectifiers have tone and the 5U4G isn't true BF, but I do know that the wrong voltages affect tone.

Replacing all the disc caps in the Vib and Rev stages with films screws up both the tone and the vib and rev sounds. I stubbornly kept doing this and always hated the results. Stick with discs, in fact if the rev and vib sound good from the start leave the original discs.

BTW for a BF conversion the orig Fender wiring layouts were actually a precise guide for the assemblers on how to dress the wires, if you follow the BF layout you can likely pull all the extra SF junk and have a quiet stable amp without the need to run a ton of shielded wire. That is, don't just use shielded wire everywhere unless you need to, that stuff robs tone.

i'm going to have to disagree completely with you there. Maybe you're thinking of polyprop caps... I used mallory 150's and orange drop 225's (which are the same material composition as mallory 150's and the coveted blue molded caps) The resistors I used are not your typical metal films, they arent as warm (or muffled) as carbon comps, but they arent blue metal films or Audiophile grade... they're basically upgraded versions of the dale rn series... they made a huge improvement in tone.

I know exactly what you did in your experience. You replaced a bunch of components and then were not immediately satisfied. Right when I replaced all these components in my amp- the amp was bright as hell, sterile, cutting, gross. I actually replaced the silver mica's I had installed with polystyrene caps (which are the BEST dielectric according to engineers- at least from what i've read) and they did smooth out the harsh treble of the silver mica's quite a bit. But the real tone improvement came from giving these components time to settle in. (I used tantulum caps in the cathode bypass positions and apparently these, especially, need time to really sound correct)

a 5u4 rectifier sounds completely different than a gz34 or SS. and while yes it will be an easy fix... it might not be what I'm going after (as I've stated above)... If you took the time to read the whole topic you would see that there is a difference between blackface and silverface transformers... and while my circuit is now identical to a blackface amp, the power tx is not the same AND a 5u4 rectifier is not the same. So how does putting a 5u4 rectifier and a different voltage power tx give me an amp closest to blackface? It's pretty obvious what would get the true blackface tone to me.

I am going to try ALL of these method... starting with the 5u4. And I appreciate your opinion on getting to the better place quickly! I really could have used that info a few months ago!!! Instead of reading dozens of posts stating that fenders are fine with 500v+.

I am huge believer in component materials... I have done quite a bit of experimenting in amps and in pedals. It DOES make a difference in pedals... I agree completely about modern components like metal films and polypropelene capacitors in vintage circuits...sometimes... it depends on the circuit, component, and definitely a "break in time" Trust me, I've gone through great time and lengths to build a proper sounding MXR dist + clone... sourcing nos 1uf tantulum caps and nos 50v .01uf ceramic caps... those things sound horrid with modern components... but they're also made to sound... honestly... bad... or at least not hi-fi or full range. A fender bf or SF tube amp on the other hand is a pretty clean amp- it really does well with new components. I havent given em the time I have in this BF- but I did give modern components in a 5e3 build about 10 hours playing before I switched back to carbon comps.

You really should give modern carbon film resistors a chance... They are pretty much the ultimate tube amp resistor. The detail from the lack of noise in my amp may not agree with the sloppier players though- it sure has caused me to refine my pick attack (and my choice of pick!)

Try the orange drop 225's out (well I'm not saying I can tell the difference between those and mallory 150's), but try some DALE RN's or PRP metal films... give em some time, you might just like em. it is tough to get through that first 20 hours or more- they can be sterile and cold as hell frozen over. Definitely do me a favor and throw those ceramics for some nice polystyrene's... you wont be disappointed.

Another thing to note about this post is my original posts- I dont know if I stated i was going for a super clear hi-fi sound verbatim, but that is what I'm going for with this amp. Hence the desire for the SS rectifier. I want punchy, dynamics, and clarity!

On another note, I seem to remember reading somewhere that a 5u4 would increase touch sensitivity? Or was it getting my plate voltages lowered would increase dynamics and touch sensitivity? I thought an rectifier with less sag would increase touch sensitivity... keeping in mind the ultralinear sunn amps. Funny that I get into this now, now I've got the itch to build an ultralinear tx Sunn 100s and I'm thinking I might wanna put some superbly inneficient speakers in this thing and get that derek trucks distorted super reverb tone. while keeping a sunn or hiwatt build for my punchy dynamic tones... I'm on here because I have truly found a lot of fun in the experimental in this stuff. Back when I would pay to have this kind of stuff done I would go through forums and see the arguments about carbon comps and component choice and wonder who could be right-- then I would wonder why SO MANY companies made new products trying to improve upon old electronic compositions. There is definitely a reason.

If you wanna try a great modern carbon film at a decent price- try the Takman 1W carbon films in your next tube amp build or modification. Those are totally worth the extra money, IMO

[Phil_S]

Try the orange drop 225's out (well I'm not saying I can tell the difference between those and mallory 150's), but try some DALE RN's or PRP metal films... give em some time, you might just like em. it is tough to get through that first 20 hours or more- they can be sterile and cold as hell frozen over. Definitely do me a favor and throw those ceramics for some nice polystyrene's... you wont be disappointed.

I don't mean to be argumentative here. I've seen this assertion before.

It seems counter intuitive to me that caps can "break in." Maybe I'm just uninformed, but I am having difficulty understanding what changes in the cap in the first 20 hours. I keep thinking that 20 hours is long enough for your ears to adjust to the tone, after which the amp starts to sound good.

IMO, what really needs to go on here is for someone to conduct a double blind study with several amps. (LOL, good luck getting it funded.) Tests required should be both subjective (listening) and objective (o-scope, cutting open broken in caps, other measurements) looking for observable differences or changes. I am convinced, if you really hear it, you really can measure it. Until we see such tests, it's going to be hard for me to break from the notion that you are simply getting used to what you hear.

I'm not challenging the assertion that caps of different make and material sound different. That seems totally logical to me.

[caveing]

Try the orange drop 225's out (well I'm not saying I can tell the difference between those and mallory 150's), but try some DALE RN's or PRP metal films... give em some time, you might just like em. it is tough to get through that first 20 hours or more- they can be sterile and cold as hell frozen over. Definitely do me a favor and throw those ceramics for some nice polystyrene's... you wont be disappointed.

I don't mean to be argumentative here. I've seen this assertion before.

It seems counter intuitive to me that caps can "break in." Maybe I'm just uninformed, but I am having difficulty understanding what changes in the cap in the first 20 hours. I keep thinking that 20 hours is long enough for your ears to adjust to the tone, after which the amp starts to sound good.

IMO, what really needs to go on here is for someone to conduct a double blind study with several amps. (LOL, good luck getting it funded.) Tests required should be both subjective (listening) and objective (o-scope, cutting open broken in caps, other measurements) looking for observable differences or changes. I am convinced, if you really hear it, you really can measure it. Until we see such tests, it's going to be hard for me to break from the notion that you are simply getting used to what you hear.

I'm not challenging the assertion that caps of different make and material sound different. That seems totally logical to me.

I wasnt being argumentative, just challenging that point of view. and to challenge my own, I'm going to switch out my resistors to carbon comps just for fun, but not before I record a video demo. once i get the rest of the amp sorted out. if you're fan of carbon comps- I really do urge you to try the takman carbon films I recommended, they really are something else. and they will bring your noise down enough to really show a difference!

Just as a side note- I am now under the imrpession that the cathode bypass caps in a fender blackface circuit can affect the tone tremondously... not value but capacitor compositon. of course I'm comparing electrolytics switched for solid leaded tantulums. They really change the feel of the amp, it's similar to the difference between a GZ34 rectifier and the SS rectifier- quicker response to my attack, faster transients, or something like that. haha

I completely agree with you on most of your ideas. But I do not agree that I just got used to the sound of the amp definitely part of it, but usually I like an amp at first and start hating it the more I hear it and the harder I listen. I actually really didnt want to like it as a lot of people do. I wanted the magic to be in the old components. the change happened almost overnight. I might even have before and after videos. But of course I have changed tubes since the new parts were put in, a change of speakers (to a widely considered brighter, cleaner, more sterile speaker), etc. But the tantulum capacitors definitely changed in tone. I'm not talking a slight change here, but a rather large significant shift in frequencies. I'd be surprised if it wasn't measurable.

[caveing]

I feel like this amp is gonna be the amp that I play and keep forever, so before people tell me not to do stuff and leave it vintage... dont worry about it. it's not a blackface...

Can anyone out there point me in the direction of...
1.) Converting to EL34's


(just kidding)

1.) I've heard the cathode resistor on the 12at7reverb driver tube is too low a value and tends to burn the tube in there. I have burnt up the resistor (and apprently someone before me did as well!) I put a 1watt in there, should I go to a higher resistnace (currently 2.2k 1 watt)...

2.) I've also read that its a good idea to decouple the shared cathode bypass cap and resistor of v1 and v2. If I do this can anyone tell me appropriate values for the v2 one that will be on the board and the new v1 cap and resistor value? What does this actually do... reduce bleeding? If I do this can I still put reverb on both channels and get them in phase?

3.) I've seen a couple different ways to put reverb on both channels... Should I avoid this? ANyone got apreffered method?

4.) I really do like the way a 12at7 sounds in my reverb channel (which I'm using as a clean channel- and planning on putting .022uf caps in the normal channel) Anyways- is there anything I could do to lower preamp gain, or make the amp more suited for a 12at7 tube in first position (i've tried a couple 5751's, while I like em, I do like a 12at7 better.

Or is there a preffered 12at7 tube... or should I use a 12ay7, 12au7, or something else? I really am not a big fan of fender preamp gain at all... fender bf power tube gain is another story. I got a few ways that I get it. like 5751 or 12at7 in first position with 12ax7 in phase inverter. I have the tremolo disconnect mod. Would the negative feedback switched out hit the power tubes or preamp tubes with the different frequency response? would that be recommended for what i'm digging?

I know this is a bunch of TGP type questions. I've been experimenting with this stuff for a while, just wondering if anyone else has and has been completely satisfied with anything (like a certain 12at7 in v1/v2?) or a way to keep the preamp clean while having the power amp kickin?

Thanks a bunch!

[renshen1957]

Also, A VVR or master will not get you to bdrm level on a 50W amp, there is nothing in the world you can do to make a Pro Rev playable in an apt. unless you live in a squat, but then someone can always unplug you from the streetlight I've yet to try a VVR, but been reading old posts and have yet to hear about the results in an amp with Rev and Vib, I would ask up on this. For an apt even a Champ is too much. Buy some little SS practice amp off Craigslist, and for days when no one's around build a 5F1 Champ and rock out. Don't bother building a 5W amp with a master just use a distortion pedal.

Hi,

I had no problem with playing a Twin Reverb at bedroom level after the addition of London Power Power Scaling for fixed bias amps; I did add a "drive compensator" (Master Volume) to dial in how much power tube distortion (if any) I chose. There is methodology to compensate for vibrato; and a fix for Tremolos. Best to ask KOC over at the Powerscaling.com forum. I will start a 50 watt soon from plans (including the power scaling circuit) which has been around since 2004.

Best Regards,

Steve

[caveing]

Also, A VVR or master will not get you to bdrm level on a 50W amp, there is nothing in the world you can do to make a Pro Rev playable in an apt. unless you live in a squat, but then someone can always unplug you from the streetlight I've yet to try a VVR, but been reading old posts and have yet to hear about the results in an amp with Rev and Vib, I would ask up on this. For an apt even a Champ is too much. Buy some little SS practice amp off Craigslist, and for days when no one's around build a 5F1 Champ and rock out. Don't bother building a 5W amp with a master just use a distortion pedal.

i guess youd be happy not to live in my apartment. had a full band in one. i dont know why people think early SF pro reverbs are that loud... they really arent. with the inefficient output tx, 5u4, and some people putting 5881's in em. they sound great at low volumes.