Blimey. You lot should get together and design something contemporary.
Are we saying a preamp is not just a preamp and the design needs to be matched to the following stages? i.e. if you made a pedal that took the normal channel Blackface preamp and plugged into the bright channel, it wouldn't just 'work'?
It's not a vintage DR by the way, just a recent AB763 build but I was trying to avoid major changes like a PPIMV for example.
Edited by Chip after realizing I had "heard" sarcasm where none was intended. I apologize for my mistake.Huh? No one said "you shouldn't try this" or "we aren't interested in thinking outside the box here." Please consider the following comments as constructive criticism.In the first place, the concept I threw out is a significant departure from an AB763 and the cumulative gain hitting the phase inverter would be a LOT higher than the Vibrato channel (let alone the Normal channel). No, I haven't built it but it might be fun to try. You
may be able to implement it in an existing AB763 layout without too much ugliness. Depends on your specific layout.
Secondly, I've been coming to grips with the fact that the entire circuit really should be designed
as a whole. In fact, it appears to be better to start at the power amp and work "backwards" through the circuit. You need to know what signal level the power tube(s) require before you can design the PI/driver stage. Then you'll know what signal level range is acceptable for the PI/driver and so on, working your way back to the input jack. So "No", "
a preamp is not just a preamp". For the change I threw together, you would need to experiment with the 1.5meg resistor
to get a signal level which works for you in your amp.
Third, the initial question wasn't "
can we design a preamp with 5 gain stages and reverb?" It was "can I do
X to a Deluxe Reverb?" If you are starting with Fender's AB763 layout, cascading 5 gain stages may be problematic due to layout problems. The layout simply wasn't designed for a high gain amp. Personally, I've had interference and cross-talk problems with several Blackface Fender builds using Hoffman's layout as a starting point, and that's "better" than the vintage Fender layout IMHO. The reverb recovery stage is especially sensitive and suceptible to squealing, etc. And the change you proposed could be more complicated than adding a PPIMV depending upon your existing layout.
Fourth, have you paid any attention to the Little Wing, HoSo56, or Tweed Overdrive Special circuits which guys here have worked out? Those are really cool, contemporary designs from my perspective.AX84.com offers several preamps and several poweramps which are designed to be (more or less) mix & match. There are also several complete amp designs like the SEL which has 4 cascaded gain stages IIRC. Plenty of gain there. They have layouts which are proven to work with the gain levels of the respective circuits. There's some really neat design work going on over there as well.
Everybody here asks questions - that's what the forum is here for. However, asking a question and then getting a bit testy when you don't like the responses can be annoying. Especially when I took the time to think up an alternative which might work OK and draw up the proposed modification.My response
is intended to be helpful
, not just critical. I hope my attempt is successful.
Chip
Topic: Cascading gain stages on AB763. Any issues with that? (Read 7721 times)