The Amp Garage

The bias is connected to the oscilator circuit. Just trying to understand what is happening here and why.

Does it make sense to tie the input lug (from bias board) and the output lug (wiper to the 220Ks) together just in case the pot ever failed? Particularly on a build, where the parts are probably coming from china? I realize old fenders rarely fail, just wondering if this even makes sense. I feel lik...

Should I remove the 220K, change the 2200pF to 500pF, get rid of the snubber and get rid of the bright cap? If yes, should I also change the 1500Ohm to 820 Ohm? I would try those one at a time, except leave the 1k5 cathode resistor on the recovery stage. The value has been doubled since it is no lo...

Could someone tell me how to calculate the frequency response of the reverb driver? It has a 2200µF cathod resister with a 25/70 (what I had on hand, but should be a 25/25) in parallel. It has a 220K resister in series with a 2200pF cap going to the grid. Perhaps I should change that to the DR stock...

The 47k resistors aren’t dropping any gain. That is part of the original circuit. I changed that to 100k. Thanks for pointing out that I forgot to fix that. I’ll make the adjustmnt on the schematic. - ok, fixed. https://www.dropbox.com/scl/fi/zxs6uyi9zdto1cv3nxmos/deluxereverb_ii-Tiger-Audio-Inc-MO...

Thank you for the response! I just logged in here to tell you all that I made an error with the 22K tail resister, which needed to be 18K to go with the 4.7K. When I changed the PI to BF standard, I just made all of it BF including the 820, but then I decided I wanted the presence control to work s...

https://www.dropbox.com/scl/fi/zxs6uyi9zdto1cv3nxmos/deluxereverb_ii-Tiger-Audio-Inc-MODIFIED-copy.tiff?rlkey=jmpe2u4aly5w47c4dgrkg0z5e&dl=0 EDIT: Updated the schematic to 18K tail resister which is what it needs to be with this presence/ NFB circuit. Prescence now works right and the NFB mod also w...

You are right, its a mechanical issue. I tracked down that the grid wire on V4B was very microphonic for one thing. I lifted it and the thump was reduced. I replaced the wire, although I only had solid core cloth covered white. I may go ahead and put the old one back because I don’t think there was ...

Plugged the guitar back in and it went away instantly. The leaf switch on your input jack(s) is dirty and not closing like it should, thus the hum when no plug is inserted. I am going to run a file over that. It happened when the guitar was still plugged in though and with the volume all the way do...

Lots of things can cause crackles. Could be a tube, dirt, noisy resistor, bad solder joint, loose connection, etc, etc.. Gotta poke around to find out; chopstick is your friend. If you haven't already, I would start with cleaning and tightening pots, jacks, and tube sockets. The wax on those boards...

I changed to a 5AR4 and re-biased to 20mA, slightly less than 70% and the tone of the amp is actually a little nicer, but the sound on the video is still there. Additionally, I now have an audible hum that I did not hear before with the 5U4GB. Unplugged the guitar, moved the volume and tones all the...

Turned it to 7 on the Vol and it still does that.

I recapped this 77 non-pull boost. I used 16µF F&Ts. I moved the standby switch after the first 2 caps. I changed the cathode bypass for V3 to the AB763 (and most other model DR) value. I am using a 5U4GB but I changed the 2.2K dropping resister to 10k as I want the sag. I have not changed the 330Ks...

The PRII is the same exact amp with a proper sized enclosure. Don't think I've worked on a super champ, so maybe production amps are different from the schematic, but they don't appear to be the same amp. Similar, but not the same. Princeton V Deluxe Paralleling the V1 makes the amp very mid heavy....

Could parallel the input triodes like the deluxe reverb II. Lots of switching options. Paralleling the V1 makes the amp very mid heavy. I split the V1 on my Concert and DRII and they both sound a lot better. I may reduce the cathode bypass for the lead side of V1 to get more gain for the lead chann...