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    5f4? Project idea - would like some guidance

    hi, I have a couple of old Symphonic 6l6 tube amps that came out of an old console. I'm looking for a guitar amp to build and it seems like the 5f4 is a close match for the transformer set with a couple of exceptions. 1 is lack of a separate bias tap. I think I can do this off the main...
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    What is this for?

    I could use some help with this . . . Someone added this resistor (it's 5.7 ohms 10W) inline with the O/T primary center tap and the B+. The amp is a JMF Spectra 60T - 2x6L6. What would be the rationale for this? Should I pull it? thanks in advance.
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    Output Transformer Wire color codes advice

    I have a JMF Spectra 60T amp I'm trying to get into shape (it had various oddball "mods" done before I got it). One has to do with the speaker taps. In any event, the OT has 3 taps: One is Yellow - which I think is 8 ohms since that's the one that was being used with the 8 ohm speaker, one is...
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    has anyone ever used one of these for a guitar amp build?

    it seems like the transformers would be a great starting point . . . . especially at this price. heathkit AA-181
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    NUOAD (New uncommon old amp day)

    I picked up this amp on impulse. The seller didn't know what it was, but said it had a 7591 power tube which drew my interest. Since noone was bidding on it, got it for $100 including shipping. After a lot of looking I figured out it's a Multivox Premier Bass Combo. It needed some of work to...
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    Tolex (Naugahyde) for speaker grill?? Hmmmm
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    cathode resistor on Gibson GA-20RVT Output tubes

    I have a quick question on cathode bias on the 6BQ5's on this amp. Is there any reason I shouldn't run with a 210 ohm cathode resistor? I haven't seen any 6BQ5 amps with more than a 150 ohm, while 6V6 amps run 200+ ohm resistors all the time. The schematic calls for a 130ohm resistor -...
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    Center Tap Volume Pot?? What does this do?

    My Gibson GA-20RVT has center taps on the volume pot's (not the wiper) with a .01uF cap to ground. What does this do?
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    Need Reverb Driver help

    The reverb died on my Gibson GA20RVT, and I tracked the issue down to the driver transformer. The only replacement I have been able to find cost $55 which I prefer not to spend. I read on DYIAudio, that you can use a SE output transformer as a sub, and since I had one on hand, I put it in as...
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    At last: Finished amp re-build/conversion

    I started this last July when I brought my sister’s ‘65/’66 vintage amp (Gregory Gemini 700) home from Ca to repair it. This amp uses the 50c5/35w4/12au6/12av7 tube combination without a power transformer; however the prior owner added an isolation transformer, and other oddball mods...
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    New JJ EL84's - loud buzz. What's up

    I'd appreciate some input from some experts on this issue. What's going on with the new JJ's? I just finished building a new single ended EL84 amp (Kalamazoo 2), and was using an old used (but very strong) RCA EL84 for all of my testing. I have everything checked out, and the amp sounds...
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    Advice needed with solving oscillation in Kalamazoo 2 Build

    I've been planning this build for a couple of months, and finally found time to do some construction. I've worked through a number of bugs and have one (or 2?) significant issue I'm stuck on - serious oscillation that I've isolated to the power tube. Coincidentally, I'm puzzled by the fact...
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    where can I install a Tremolo Strength Pot in a Kalamazoo 2?

    I'm trying to avoid too much trial and error on this. Per my previous thread I have an amp chassis that I'm building a Kalamazoo 2 circuit into. Since the control panel includes a strength pot, I'd like to use it. My thought was it should go between the cathodes of V1a and V2a. Is this a bad...
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    need assist on Kalamazoo 2 PT voltage concern

    I have a question about initial test voltage on my Kalamazoo build. I installed the Power supply and wanted to do a quick test. Using a 250-0-250 Hammond PT, with the filaments and all secondary's connected, a 6x4 rectifier installed. When I do an initial power on using a variac at about 25-...
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    please recommend a good SE EL84 circuit

    I have a vintage amp (Gregory Gemini 700) that uses the 50c5/35w4/12au6/12av7 tube combination without a power transformer. I want to strip it down and install a SE EL84 circuit. I'm looking for circuit suggestions. The control panel has Volume/Tone/Speed/Intensity on it so I want a circuit...
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    Got Shocked last night! What is your test protocol?

    I recently picked up a mid-60's Gibson GA-20rvt amp. The first thing I always do with vintage amps is tear them down, clean them up, recap, checkup, install 3 prong cord if one isn't already there. I always test for voltage on the chassis by attaching a jumper to the chassis with a 1000 ohm...
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    Why my amp pics up greater amount of guitar noise than other amps.

    I have a Gibson GA-5 that I refurbished and it's great except for one issue that puzzles me. While it's dead quiet at idle with no instrument plugged in (except a little bit of hiss when the tone pot is at 10), once there's a guitar plugged in, there's a greater amount of pickup hum than I...
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    Gibson GA5 Crestline owners - Cabinet Rattle?

    I have a 60's vintage Gibson GA5 I recently refurbished, and it sounds awsome, except that I have a rattle that occurs at low frequency. It's worst on the Low G and A (3rd - 5th Fret on the low E string). I've traced the problem to the cabinet but I can't find a single joint that's the issue...
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    2 halves of a Super Reverb???

    hmmm . . . WTF? (no affiliation or interest)
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    What do I have? Capacitors in series with reversed polarity

    I have a Polytone Mini s12L amp I'm trying to clean/tune up. While looking at the preamp board I found two small electrolytic caps installed with the + side of each connected to the board, the - sides connected to each other. They are polarized 10uF/35V caps, and the location where they are...
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    quick question: blues jr reverb

    My question in net is: just how much reverb do these things produce? Background: I have a Blues Jr and one thing nags at me - the reverb is very underwhelming. It's a 2003 cream board, and while playing with it today I noticed little reverb even at the wide open setting. After trying a...
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    need advice re: tone stack fix - Blues Jr content

    I have a Blues Jr with a bad Treble Pot. The bass and mid pots seem to be fine, but they have less effect on the tone than I would expect. Is it likely that the bad treble pot effects the function of the bass/mid tone? I'm ordering a new treble pot today or tomorrow and am debating on...
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    Deal Alert - Peavey Special 150 $100!

    anyone in DC Metro who doesn't already have way too many amps (like me) - check this out. A great deal on a great SS amp: Peavey Special 150 I don't know the seller and have no interest in the sale - - -
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    Blues Jr Master Volume non-functional

    I just acquired this am and it sounds great. It's a 2003 cream board I bout on ebay - needed a little work. One issue remaining is that the Master Volume is non functional. That is it has no effect completely off or wide open the volume is the same. I did some basic checks on the Pot (in...
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    Is the SFPR more sensitive to what guitar than other Fender amps

    I have a 72 Pro Reverb. It's been fully recapped (electrolytics - all signal caps are stock), and I'm running Jensen c12ns in it. It sounds great with hollow body guitars with humbuckers, and with single coil Strats. But it sounds awful with solid body guitars with hot humbuckers (les paul...