• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Hammond AO-35 HiFi Conversion Help

R9 and R15 are the input and feedback resistors in a shunt feedback system, making pin 7 of V2 a 'virtual ground' or summing node. Closed-loop gain would be exactly proportional to the ratio of those two resistors if open-loop gain was infinite, but I'm sure this example falls far short of that.
 
Kinda thought so. I think if that were sitting on my bench the feedback structure would get changed to bring the feedback into the cathode of the voltage amp like most things do.
 
BinaryMike said:
I think you will get a lot closer to the results you're looking for if you lift C4 out of circuit and apply input to the grid of V1B. Overall gain should be about right for hi-fi applications. C5 should be deleted as well, because it's surely rolling off the high end. In this way, you will be leaving feedback as designed around the power amp section.
Click to expand...

I want to make sure that I understand this part. I would apply my input signal to the top of R6? I could essentially remove everything before R6?

When I remove C5, am I just clipping that capacitor out of the circuit and stopping there? Or do I need to replace the cap with a wire.

Thanks!
 
gadget73 said:
Kinda thought so. I think if that were sitting on my bench the feedback structure would get changed to bring the feedback into the cathode of the voltage amp like most things do.
Click to expand...

Once I have done some of this initial work, bypassing the input stage and testing without C5, perhaps I could explore this.
 
Good ones will get to 20kc without much drop. You'll see it drop down from there. If I do a full frequency test at low power, I'll run it out to 100kc just because the generator will go out that far. Normally it drops pretty sharp much past 20kc, and thats a good thing. If you get big spikes and resonance in the ultrasonic region it can make for an unstable amplifier. Nobody needs high frequency oscillation fed to the speaker.
 
So, @punkzter, how did this turn out? Were you able to complete it? Was it worth your time? I have a brother in law with two of these amps that he's willing to give to me.
 
You must log in or register to reply here.
Back
Top Bottom