New build: Princeton Reverb with mods - advice wanted!

[klooon]

Well spotted - the recovery stage should be going to the green ground if that is where I took the supply from, but I can't remember. In the amp I'm pretty sure I had it going to the correct return point tho. My bad.

I have re-drawn the schematic to correct the grounding error. (Klooon - if you keep this up, you'll definitely be kept on when the going gets tough. :-)

Thanks for checking! I will update the layout and schematic accordingly. Now it's time to start building ;-) All the components are in and I will start with making the eyelet board. Keep you all posted.

[klooon]

Here are the newly updated schematic


and layout

[klooon]

Again some modifications/corrections to the schematic and layout:
- I will not use the 1R resistors to bias in the fixed bias situation. I will use the actual plate current instead (from the plate voltage and OT primary impedances.)
- the polarity of the bias diode is now correct.
- position of the NFB pot is now between the 2k7 and jack tip (instead of between the 2k7 and junction 47R, 1k5 and 25uF)
- from the tremolo intensity pot there should be a 0.1uF instead of the 0.01uF. I have changed one 0.01 in a double value for lower trem speed.
- I will use isolated jacks all around, except for the two guitar input jacks.

Updated schematic v011:


Updated layout v009:



Here are some first pictures of the building process:

[klooon]

More progress...

[klooon]

Finally, the amp is finished and works absolutely fine!!

Here is the final layout (I reversed the pot wiring for the Mid pot and the Negative Feedback pot):


And here are some build pics:

[klooon]

Some technical data:

Fixed Bias:
Plate Voltage: 405VDC (@6V6 pin3); with the resistance between the OT CT and 6V6 plates of 186.5Ohm and 213.8Ohm and their respective voltages of 3.5 and 4.0VDC, the plate currents are 18.7 and 18.8mA. The plate dissipation of each tube is then around 7.6Watts (=0.0187*405), about 55% of the maximum power dissipation of the JJ 6V6GT.

Cathode Bias:
Plate Voltage: 347VDC. The cathode resistor voltage is 24VDC. Multiplying the current per tube (0.5*24VDC/329R) by the plate voltage minus the cathode resistor voltage, this gives 11.8 W which should be okay I think?


And the sound? Amazing!! From the cleans to the overdriven sound!

Mid pot gives a nice boost not only in mids, but also to your overall volume perception. This is really the sound I was looking for, more to the Tweed amps that I have built. Really, really great! The ToneStack bypass switch is doing actually the same as the mid pot fully open, but with even more dB coming through (or cutting less signal). Soundwise not so different from the mid pot, IMO. The fat switch is usable in this situation (“fat off”), but also without the ‘fat cut’ the sound is also fine. Nothing gets really muddy/bassy…

The Negative Feedback knob is really nice. Turning it clockwise you dail out the negative feedback, you get a slight increase in volume and the sound gets way more lively, more harmonics, which I like a lot, especially for the cleans.

The added dwell knob is useful as well, especially at higher reverb intensity settings otherwise it’s really like your sitting in a small tank and echoes all the way over. As I built it in a head, the positioning of the reverb tank is very important the black output should be as far as possible from the PT as it will pick up an enormeous hum otherwise.

Tremolo is extremely nice is Fixed Bias. Lush and it only wobbles if you let the notes decay. In Cathode bias the maximum intensity setting is just enough to produce a nice and noticeable wobble.

Switching between cathode and fixed bias is giving slight differences; in cathode mode a bit lower volume and less defined bass, a bit more muddy/raw which might come handy. Also the bypass cap switch in cathode bias mode is slightly noticeable. With the bypass cap disabled, the sound is a tad rawer. But I have to play more to fully experience these (small) differences. The first time I plugged in, I could hardly hear any differences.

So overall I am incredible happy with this build. Thanks to all the forum members that helped so much during this build process, for inspiration and guidance!! Really great!!!

[überfuzz]

Dude, you ever heard about the 24 h rule? You'll get a forum warning if you don't post sound examples within 24 h from finishing the amp.

[Justin Thomas]

Justin

[überfuzz]

Time is ticking... soon we have serious forum felony.

Seriously though, your design/build looks very interesting.

[klooon]

Time is ticking... soon we have serious forum felony.

Seriously though, your design/build looks very interesting.

I just finished this before going on holiday. I will post the clips when I am back!!

[klooon]

Time is ticking... soon we have serious forum felony.

Seriously though, your design/build looks very interesting.

I just finished this before going on holiday. I will post the clips when I am back!!

[klooon]

OK, finally some sound bites!!

DIY Princeton Reverb AA1164+ 001 - YouTube
DIY Princeton Reverb AA1164+ 002a - YouTube
DIY Princeton Reverb AA1164+ 002b - YouTube
DIY Princeton Reverb AA1164+ 003a - YouTube
DIY Princeton Reverb AA1164+ 003b - YouTube

[tubeswell]

Sounds mighty

[Audiotexan]

Very impressive Klooon! =)

[pietro_moog]

hi. i was thinking about building the same amp (fixed bias only. not sure about the reverb) does the tremolo work? is it safe with that transistor?
would you call it a dramatic improvement over the stock one?