Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: rutledj on October 01, 2019, 07:13:12 pm
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So I've built the Princeton reverb based on the layout here on Hoffman's site. Everything works great. So what's the problem? Every time I build a Fender style circuit (blackface deluxe reverb, this princeton reverb), they never have any breakup or overdrive sound. They stay clean all the way up. I've listed some of the voltages below. Do they seem normal?
A 423
B 410
C 331
D 255
V1-1 178
V1-6 168
V3-1 168
V3-6 167
All the cathodes around 1.3v
Power tube grid voltage: -40v
Using classictone transformers, Warehouse ET65 12" speaker.
Even if the speaker doesn't break up, shouldn't there be some preamp or power amp distortion?
Thanks,
Rut
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What voltage do you measure on pins 8 of the 6V6s? Should be roughly 25mv to 35mV. The lower this voltage the cleaner the amp will sound. Try setting the bias to give about 30mV and you should get some breakup.
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take the NFB off, it's for sisys :icon_biggrin:
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take the NFB off, it's for sisys :icon_biggrin:
:l2:
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What guutar and what pickups are you using?
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They stay clean all the way up.
Awesome! How cool is that!
With respect, Tubenit
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+1
I've not worked on many Fenders that liked to get as dirty as other amps, that said they seem to take pedals well enough to get it there. Clean is a GREAT starting point for OD n grungy grinds
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If regular audio 10 or 15% taper pots are used for volume and treb, then they will require much higher settings than users may expect.
Use linear pots (or have fun sourcing vintage Fender spec 35% audio taper) if having to set these controls at ‘8’ or more leaves you uneasy.
But vintage spec single coil PUs may not be able to achieve much overdrive even with controls at max.
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Maybe it is the pu's. I'm using a strat with 69 pickups.
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A simple clean booster pedal may be what you need. Or the classic Tube Screamer.
You could add a clean booster stage at the input of the amp. I’ve done that with a small pcb mounted directly to the input jack.
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Hello. This is my first post, and I am a novice tube builder, but have had 36 years of tube amp experience from Fender to Marshall, but my favorite is the Vox. I digress.
I think the Princeton Reverb is most likely my favorite Fender amplifier. They take to pedals well, and I know we all like the natural saturation our tubes give us, and this can be achieved. One way is to use the EP gain boost pedal. This pedal does color the sound some, but it drives the power tubes hard. Another is the classic Tube Screamer. My choice would be a Behringer TO800 for $23. It is exactly like the OG TS. Another affordable option is the Soul Food from Electro-Harmonix. A Klon clone that works great as a clean boost or has a great gain stage as well. I generally run the TO800 in front of the Soul Food. There are lots of options for pedals that will make a Princeton Reverb sound very bluesy and not loose its full rich tone. Another pedal that is completely awesome is "The Dane". If you haven't heard it, check it out. I am not affiliated with any company, but just saying what is available without tearing into your amp. The Dane has a wonderful breakup with a high output clean boost each can be used independent or together. Here is the kicker. The Dane also allows you to add back your low end as you see fit to keep that full rich tone without having the mid range completely run the mix.
Again. Thanks fellow amp enthusiast for such an information forum. I look forward to answering what I can, and asking a lot of questions when my new build comes up. Good luck to the OP.
P.S.
The Negative feed back loop could be setup with a linear pot to allow for various effectiveness. To me when this is done it kinda sounds like you're re-biasing the amp cold *(like a British Amp)* to get more breakup at lower volumes, or you can have it full i.e. sounds like a balanced or warm bias that doesn't breakup very much. If my termonoly is way off feel free to correct me. I am sure ya will :)..
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Every time I build a Fender style circuit (blackface deluxe reverb, this princeton reverb), they never have any breakup.
If you’re talking multiple amps you’re likely not making the same build error over and over. It sounds like maybe you just don’t like Fender circuits (not stock, anyway). AFAIK the Princeton Reverb is prized for its clean tone, no one really mentions its overdrive...