Hello folks,
here is a re-design of pcb of Rockola PA amp.
let me know your comments.. let me also know replacements of trannies.
I have tried to make it more convenient to build.
I am posting input circuit... output stage is coming up...
I will try to link the design, here or next post..
regards
prasi
here is a re-design of pcb of Rockola PA amp.
let me know your comments.. let me also know replacements of trannies.
I have tried to make it more convenient to build.
I am posting input circuit... output stage is coming up...
I will try to link the design, here or next post..
regards
prasi
Attachments
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Q6 thru 9
Dont need to be such high current
low gain transistors.
Bandwidth and low gain not suited for
a gain stage. They are relatively difficult
for the differential input to drive.
Current mirror in differential is good idea.
But the high current needed to drive second
gain stage is high. So instability would be a issue.
With too high differential current with mirror.
Needs degen and likely lower current.
And that is possibly if 2nd gain stage was easier
to drive. need different transistor.
likely works as shown but to make stable
C5 C6 made very high and C7 and C8
added with high value. should not be needed.
looking at such high values for
C5 and C6 for the amp to be stable.
Much to high, slew rate be very very bad.
The overall concept is there.
And this is very fun topology to use.
But overall design needs improvement.
And different transistor choices.
Overall feedback gain of amp is very high.
and compensation capacitors all very
high.
So overall amp and DC operating points
likely not ideal to have a happy amp.
And other methods have been used to make
up for it.
Dont need to be such high current
low gain transistors.
Bandwidth and low gain not suited for
a gain stage. They are relatively difficult
for the differential input to drive.
Current mirror in differential is good idea.
But the high current needed to drive second
gain stage is high. So instability would be a issue.
With too high differential current with mirror.
Needs degen and likely lower current.
And that is possibly if 2nd gain stage was easier
to drive. need different transistor.
likely works as shown but to make stable
C5 C6 made very high and C7 and C8
added with high value. should not be needed.
looking at such high values for
C5 and C6 for the amp to be stable.
Much to high, slew rate be very very bad.
The overall concept is there.
And this is very fun topology to use.
But overall design needs improvement.
And different transistor choices.
Overall feedback gain of amp is very high.
and compensation capacitors all very
high.
So overall amp and DC operating points
likely not ideal to have a happy amp.
And other methods have been used to make
up for it.
A connection with the jukeboxes of the same name?
https://fr.wikipedia.org/wiki/Rock-Ola_Manufacturing
https://fr.wikipedia.org/wiki/Rock-Ola_Manufacturing