To use a differential input I think I would use one of the opamp circuits you can find in Self or other reference, rather than a transformer. You are likely to get much better response and distortion with a decent opamp than a transformer. However, if you are concerned about large DC offsets on the signal, or other hazards, the transformer might be a better bet.
You can always try tying the ground and signal together at the amp input, but that will remove many of the balanced system advantages.
You can always try tying the ground and signal together at the amp input, but that will remove many of the balanced system advantages.
I have this in the works, just in Prototype stage ATM but its completely transparent.
Does that negate the need to make the amp balanced then? You can always make them single ended, and if you have balanced inputs you add this on?
@Jacruzer787 to my understanding, If your preamp is fully balanced including the signal output (true XLR?!), then you can feed the balanced signal to two amp-modules working together on each their own polarity. If you are not sure about this connection, an opamp-circuit or a transformer is required to invert the signal before the poweramplifier.
@fireanimal nice work, Again! 🙂
@fireanimal nice work, Again! 🙂
Thanks.
Also on running the amps bridged with out of phase input signals. This is not straight forward, and has yet to be tested. First off the rail voltages would need to be lowered to keep all devices within their SOA. Each amplifier board would see half the normal impedance, so if your speakers are 4ohm for example each channel sees them as 2ohm. Depending on Output devices, EF3-3 or EF3-4 you would be looking at rail voltages between 30 to 40 V +/-
The input buffer is fully balanced and outputs a single ended signal to the amplifier, #1 reason for this is to complete eliminate ground loops amongst others.
Also on running the amps bridged with out of phase input signals. This is not straight forward, and has yet to be tested. First off the rail voltages would need to be lowered to keep all devices within their SOA. Each amplifier board would see half the normal impedance, so if your speakers are 4ohm for example each channel sees them as 2ohm. Depending on Output devices, EF3-3 or EF3-4 you would be looking at rail voltages between 30 to 40 V +/-
The input buffer is fully balanced and outputs a single ended signal to the amplifier, #1 reason for this is to complete eliminate ground loops amongst others.
@fireanimal You make a good point about controlling the voltage for a bridged amplifier. You get twice the current at any given voltage, so there could be SOA concerns. It's a good way to use those 24 volt transformers.
Update on my repair...
Took out D112 and D114. Measuring outside the board D112 was ok, D114 shorted. Replaced both, powered up.
Now TP106 to - supply shows 19V!!
So obviously something else has gone as well. Shold I replace Q106 next or any other ideas? Can't see any damages on components or board itself.
All diodes light as they should.
My second output board and both IPS are working as expected.
I was also looking for a board layout tracks picture. Has that been posted? Don't see it in the dropbox folder.
Thanks
Took out D112 and D114. Measuring outside the board D112 was ok, D114 shorted. Replaced both, powered up.
Now TP106 to - supply shows 19V!!
So obviously something else has gone as well. Shold I replace Q106 next or any other ideas? Can't see any damages on components or board itself.
All diodes light as they should.
My second output board and both IPS are working as expected.
I was also looking for a board layout tracks picture. Has that been posted? Don't see it in the dropbox folder.
Thanks
Maybe you can try removing Q106 and test it. Replace it if you have others on hand just to be sure.
You may also want to test / replace Q102.
Note: you can run the board without Q101 and or Q102 installed. Just short the collector & emitter pads on the pcb.
This may help you narrow down the problem.
Yes, Q106 was original short
https://www.diyaudio.com/community/...he-wolverine-build-thread.385920/post-7463182
Thanks for the tip @stuartmp , I'll start with your suggestion.
The only transistor I found laying around is a BD140. Could that be used?
https://www.diyaudio.com/community/...he-wolverine-build-thread.385920/post-7463182
Thanks for the tip @stuartmp , I'll start with your suggestion.
The only transistor I found laying around is a BD140. Could that be used?
Providing the negative rail voltage minus the ~ 0.5 voltage drop over D116/R113 is present at the collector of Q102, then Q106 should have no influence on the voltage at TP106. The circuit around Q102 is a simple regulator consisting of one emitter follower that takes its reverence from R103/R104. During normal operation the diodes D102/D112/D114 will not conduct.
Can't recommend that but....
The BD140 for the Predriver. Vce breakdown is only 80V. Rail at +/-64V is ~128Vpp so its not a good idea long term. But if you keep the input shorted you should be ok for a DC validation test only. Then you can order a new predriver. It may also help you track down another issue so you can order all your parts at once. Ensure the input remains shorted.
Well done, you can now move forward and only place one order for parts. What did you have in for Q106 2SA1381E ?
Actually not sure what i have in Q105,Q106. It's not TTx004B as they are with unisolated heatsink.
Bought the complete kit from fireanimal - and now its mounted with nut so can't see the complete marking.
Perhaps I misunderstood you, the predrivers Q105,106 seem to work fine. The damage from the short was on Q102 and D114.
Bought the complete kit from fireanimal - and now its mounted with nut so can't see the complete marking.
Perhaps I misunderstood you, the predrivers Q105,106 seem to work fine. The damage from the short was on Q102 and D114.