No, I have never populated that position in any MyRef Build. (four V1.2 and two V1.3 boards/PCBs) It's my understanding that using Blackgates impacts the the need for that piece.
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Hmm, I changed the input design when I direct coupled it, so there is no telling which right thing I did solved the issue. Probably I could try swapping C9 R10 on the RevC board and see what happens.
C1 is the input DC blocking capacitor.
If your Source equipment does not have DC blocking incorporated them you must use C1 here.
If you choose not to then you are relying on the DC detect and protect to activate.
The DC blocker also affects the source resistance seen by the input.
Omitting the DC blocker will change the output offset.
McBob, you are playing with fire.
If your Source equipment does not have DC blocking incorporated them you must use C1 here.
If you choose not to then you are relying on the DC detect and protect to activate.
The DC blocker also affects the source resistance seen by the input.
Omitting the DC blocker will change the output offset.
McBob, you are playing with fire.
Amdrew,
I appreciate your comment but can you go a little deeper. Some of these amps have been in operation for almost two years. What should I be looking for? What damage could occur to what particular component?
I appreciate your comment but can you go a little deeper. Some of these amps have been in operation for almost two years. What should I be looking for? What damage could occur to what particular component?
Soon,
I have some V1.3 PCBs. All part assembled.
The two that came with a kit of all components did not not work. Some of the components were faulty. I did eventually order up replacements to get the RevC amplifiers working, but by then I had moved on.
Just this past week I have returned to RevC and yesterday got the first operating. The DC detect does not seem to detect -ve output offset. I shall investigate further. But reports should not appear in this FE Thread.
The main reason for returning to RevC was to finalise my suggestions for modifying the relay circuit to operate properly. That is now done.
I have some V1.3 PCBs. All part assembled.
The two that came with a kit of all components did not not work. Some of the components were faulty. I did eventually order up replacements to get the RevC amplifiers working, but by then I had moved on.
Just this past week I have returned to RevC and yesterday got the first operating. The DC detect does not seem to detect -ve output offset. I shall investigate further. But reports should not appear in this FE Thread.
The main reason for returning to RevC was to finalise my suggestions for modifying the relay circuit to operate properly. That is now done.
There is one thing I should mention about my builds. The heat sink on R3 is attached with double sided thermal tape as used with CPUs. I documented that during the initial build series of posts. I remember a discussion about the heat transfer there being critical to the operation of neighboring components. Though the FEs sound great - could that have an impact on the general temps of the amps?
a change in output offset when you connect the source equipment.
Can the output offset ever get to a level that could damage a speaker?
Will you know that the speaker is about to be damaged, quickly enough to take action?
O.K Andrew, I hear what you are saying. In the near future I'll set up a V1.2 with C21 installed to determine if the trade-off between sound quality and the extra measure of safety is worth the gamble.
Thanks.
Thanks.
Hi Andrew,
typo? You probably meant C13, right?
C13 is the input DC blocking cap.
C21 is simply C9 bypass... it's absolutely not needed.
You're already using Audyn True Copper as input DC blocking capacitor (C13)... 😉
It's probably so.
I guess Bob detached the bulky coupling cap to permit a clearer view of other components.
Combine the two things and the misanderstanding is served... 😉
Sorry for the confusion. Yes, C13 is the DC blocking cap on the input. It is also the High Pass Filter and that should determine the LF roll off of the amplifier, not relying on the NFB cap to do that roll off of the LF response.
Bob!
In the one of the posted pictures it's clear that you have C21 installed! 😱
It explains your problems and listening impressions...
Oh Man! I hate that hero to zero in thirty seconds thing - and right in front of the entire universe. 
There is a feeble explanation but I won't bore you with it. I guess that's why we post pictures.
Dario, you could have just whispered this in an email and I would have had time to fabricate a very convincing lie.
Back to the soldering station.
Edit: I guess I should explain my mistake so others don't get caught. In all the previous builds C21 was a through hole component and I paid attention to leave it out. With the switch to surface mount items, I overly concentrated on clean and effective soldering of those little pieces. This shouldn't be a problem for builders who are starting out with mixed components. "Hard to teach an old DIYer new tricks" That doesn't excuse my inattention, but it might prevent a similar problem down the road.
There is a feeble explanation but I won't bore you with it. I guess that's why we post pictures.Dario, you could have just whispered this in an email and I would have had time to fabricate a very convincing lie.
Back to the soldering station.
Edit: I guess I should explain my mistake so others don't get caught. In all the previous builds C21 was a through hole component and I paid attention to leave it out. With the switch to surface mount items, I overly concentrated on clean and effective soldering of those little pieces. This shouldn't be a problem for builders who are starting out with mixed components. "Hard to teach an old DIYer new tricks" That doesn't excuse my inattention, but it might prevent a similar problem down the road.
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Oh Man! I hate that hero to zero in thirty seconds thing - and right in front of the entire universe.
No problem... s**t happens... 😉
Dario, you could have just whispered this in an email and I would have had time to fabricate a very convincing lie.
😀
Probably I should... but the surprise was so big that I've posted without thinking...sorry 🙂
PS (not related)
It's incredible the amount of tiny details you find to fix when checking carefully gerbers...
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But then... why didn't the Blackgates fail with C21 installed as has been so often mentioned on the threads? Houston we have a mystery.
They don't fail, they perform worse. 😉
After removing C21s you'll probably hear an improvement in sound coeherence and soundstage.
Great. Good to know. I would have expected sparks and that stinky green smoke. I'll put things in order and report back.
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