Tube Amp Archive

Rather than convert a disappointing stock HRD into another amp, I instead cleaned it up and made a few changes and what we have now is the best sounding 'hot' amp on the floor. The ic capacitors really are garbage, and replacing all those with MKP or MKSs and the small ceramics with silver micas mak...

It's the phase on the power tube filaments that matters since they are essentially humbucking when properly phased... since the preamps tube filaments aren't running in a push pull fashion, phase doesn't really matter there... that being said, I've always tried to wire them in phase anyway... So ar...

Its always intrigued me why the Princeton Reverb AA1164 used the center tap to ground and the two 100Ω resistors to earth off the heater legs.

One thing I did do was to make sure all the pre-amp heater wires were correctly phased. My AA1164 is dead quiet

A great build story Bigbear - but just a note of caution on stepdown transformers: I'm in a similar position to you here in Aus with 240v wall voltage. Stepdowns are great because you can get an accurate 110V, unlike many of our friends in the US at present. But the problem is that most stepdown tra...

We have 30+ amps in the studio, and over the years the popularity/best comments go as follows: 1. 5E3 deluxe (P12R) 2. Brown Vibroverb 6G16 (2 x C10Q) 3. BF Princeton Reverb AA1164 (C10R) 4. 1964 JMI AC30 TB (2 x Vox silver bulldog) 5. Matchless Lightning (2 x 12) 6. Marshall 1962 JTM45 Bluesbreaker...

Those .01, .01 and .02 caps control the vibrato speed, and are usually ceramic in the older silverface amps. A common problem in the blackface amps is the speed is too fast, so if you dont like the speed range, you change the first .01 cap to a .02 to slow it down. I replace them with NOS ceramics (...

I have a Marshall TSL2000 602 which had the same popping issue. Fixed it by correctly connecting the power supply PCB spade connectors to the board, some had become reversed when being taken apart. In particular, the connections from the power socket to the board (live to fuse W2) then fuse to PT (W...

A little bit off topic, but I am experimenting with the coupling caps in a single-ended champ style amp (see schematic). The issue is the same - 0.1uf coupling caps and their effect on tone and gain. The amp tone is a bit muddy, especially at high volumes. I have changed the 0.1 coupling cap in the ...

Another way to change the character of your amp without altering the fundamentals of the sound is to change types of capacitor in the pre-amp (not the value) especially right at the front end. Silver micas for small coupling caps or treble tone stack cap can sharpen the tone up a lot, and high quali...

Yes, you are right Bob-I. Fiddling with the channel coupling resistor is probably not the best thing to do, except that some models like the Fender 30 have a pull-on boost that drops this resistor value to increase the gain. The channel is coupled with the 3.3m/10pf pair, and the boost effectively d...

I have added the Diaz Vibroverb cathode mod to a number of blackface amps with great success. I add a 2-way toggle switch to the back panel, one setting is stock, the other is Diaz mod just like the CS Vibroverb RI. I only add the cathode switching, and not the channel and tremelo disconnect. The mo...

Great discussion! I modify the return reverb mixing resistor, be it 3.3M or 470k, to get the right amount of reverb in the blended signal. On some amps the reverb is too passive for my liking even at full on. An interesting point is that the Fender brown Vibroverb had spectacular reverb that went on...

Are the voltages upstream of the plate resistor in line with the schematic? Have you disconnected and checked the 10k and 1k 1W power resistors? These components do a lot of work in these amps and can change value over time, although they usually drift higher. The first thing I do in these amps (I h...

Another way to increase gain on this channel is to add in the Cesar Diaz Vibroverb RI switchable gain on both cathodes of the normal channel pre-amp tube V3a and V3b. You need a DPDT switch and mount this on the back panel, then just copy the Vibroverb circuitry. The Diaz mod also switches out the t...

Here's an answer to your original question from another angle. I'm not an Xpress guy either, but choice of caps makes a BIG DIFFERENCE in the tone of Fender and Marshall amps. In vintage Fender tweed/BF/SF amps, you can replace the coupling and tone stack caps with polypropylene caps without colouri...