Hello,
I'm new to this forum.
I have built two ACA 1.8 that sound wonderful, thank you Nelson Pass.
I have a problem that I can not solve myself.
Version is 1.8, each amp works perfectly fine in stereo and in Mono RCA Bridged but one Chanel doesn't work in Mono RCA Parallel.
I really don't know where is the problem, I've triple checked the circuits and connections.
Maybe someone has already had this problem.
I'm sending pictures of the faulty side (not working in Mono RCA Parallel and working fine in Stereo and Mono RCA Bridged).
Thank you very much if someone can help
I'm new to this forum.
I have built two ACA 1.8 that sound wonderful, thank you Nelson Pass.
I have a problem that I can not solve myself.
Version is 1.8, each amp works perfectly fine in stereo and in Mono RCA Bridged but one Chanel doesn't work in Mono RCA Parallel.
I really don't know where is the problem, I've triple checked the circuits and connections.
Maybe someone has already had this problem.
I'm sending pictures of the faulty side (not working in Mono RCA Parallel and working fine in Stereo and Mono RCA Bridged).
Thank you very much if someone can help
Yes of course, I have swapped everything around the bad amp (which is perfectly fine on « Stereo mode » and « RCA bridged »), cables, speakers and check it’s entrance volume
Okay. A bit of off the top of head thinking.
I've mulled over the pictures and nothing looks out of place. And you have a working example to compare against.
Working in Stereo suggests that the speaker wiring and input wiring is good for the central switch position, but that throws up an anomaly for Balanced Bridged (XLR) mode. (I assume your pre amp has a balanced output and you are not using XLR to RCA cables?) The only difference is two short wires from the XLR socket to the RCA sockets...
Parallel mode just links the two inputs together at the switch. (I see the speaker link.) You can use either left or right RCA and either Red and Black speaker outputs. The switch cannot be shorted to ground or you will get no output from either channel... You could try the original Parallel method - link the Black speaker terminals and pop a paper clip into XLR pin/sockets 2 and 3 to short the RCAs together, then the switch is central.
I've mulled over the pictures and nothing looks out of place. And you have a working example to compare against.
Working in Stereo suggests that the speaker wiring and input wiring is good for the central switch position, but that throws up an anomaly for Balanced Bridged (XLR) mode. (I assume your pre amp has a balanced output and you are not using XLR to RCA cables?) The only difference is two short wires from the XLR socket to the RCA sockets...
Parallel mode just links the two inputs together at the switch. (I see the speaker link.) You can use either left or right RCA and either Red and Black speaker outputs. The switch cannot be shorted to ground or you will get no output from either channel... You could try the original Parallel method - link the Black speaker terminals and pop a paper clip into XLR pin/sockets 2 and 3 to short the RCAs together, then the switch is central.
Thank you for trying to help me.
I'm on a business trip till Monday. I will have to wait for next week to be able to continue to try to find out by following your advices.
I really wonder if the switch would not be the problem. One way to find could be to exchange it with the working one unit.
I'm on a business trip till Monday. I will have to wait for next week to be able to continue to try to find out by following your advices.
I really wonder if the switch would not be the problem. One way to find could be to exchange it with the working one unit.
Congratulation, your amp looks beautifull.
I understand that on my pictures it is a bit complicated to track the connections and I'm sorry for that. But believe me, I have tracked them very carefully and the best I can. Actually in the real world (as opposed to pictures) it is not so difficult.
But obviously there is something wrong that is not so obvious.
Anyway if I can solve the problem, I will post how I did it. This might be useful to others.
I understand that on my pictures it is a bit complicated to track the connections and I'm sorry for that. But believe me, I have tracked them very carefully and the best I can. Actually in the real world (as opposed to pictures) it is not so difficult.
But obviously there is something wrong that is not so obvious.
Anyway if I can solve the problem, I will post how I did it. This might be useful to others.
Thank you once again for your help and the time you spend reading my problems.
I should have done something wrong but I'm really searching still.
I have three new points to expose, maybe that could give useful information on how to help me :
1.
When trying to run in mono RCA parallel, if I plug as advised : R and L in "inputs A" I don't get any sound from the "bad" amp.
But if I plug the input in "input B" of the "bad" amp I got sound out of it! Although I have continuity (I triple checked) with the switch down through the inputs !! I really don"t get it
2.
When running in RCA Bridged I have a -4db (average) level coming out from the "bad amp".
I've checked with white nose, and I've switched both amps to make sure it doesn't come from the room or something else, that difference comes from the "bad amp"
3. Ultimate point : I broke during assembly one ZTX450 and I had to buy a new one from a different provider (I leave in Europe). Could that have an impact on something? I don't think so, but I'm trying to give as many information as I can.
Thank you very much for your help.
I should have done something wrong but I'm really searching still.
I have three new points to expose, maybe that could give useful information on how to help me :
1.
When trying to run in mono RCA parallel, if I plug as advised : R and L in "inputs A" I don't get any sound from the "bad" amp.
But if I plug the input in "input B" of the "bad" amp I got sound out of it! Although I have continuity (I triple checked) with the switch down through the inputs !! I really don"t get it
2.
When running in RCA Bridged I have a -4db (average) level coming out from the "bad amp".
I've checked with white nose, and I've switched both amps to make sure it doesn't come from the room or something else, that difference comes from the "bad amp"
3. Ultimate point : I broke during assembly one ZTX450 and I had to buy a new one from a different provider (I leave in Europe). Could that have an impact on something? I don't think so, but I'm trying to give as many information as I can.
Thank you very much for your help.
Yes I'm getting the exact same level on both chanels when the "bad" amps is playing in stereo. Sorry I had not understood your question.
In the mean time I've discovered a new thing. I don't know if this is relevant :
When playing in mono RCA parallel, as mentioned to be able to get music from the "bad" amp I need to plug the input B (instead of A as shown in manuals). But if change the input "on the fly" while the music is playing from input B to A the music starts to play from the "bad amp" for 0,5 second and then stops. I don't know if that could help ...
I have checked once again all the connections, solderings this morning and resistors values.
I'm a bit lost.
So we use the same description can we use Red RCA channel & White RCA channel.
Can we recap a little. I'm more than a little confused. (In fact it is difficult to draw any logical reasons for the symptoms described...)
Are you saying that in Parallel mode, if you use the White RCA input you only get output from the White channel? But if you use the Red RCA input you get output from both channels or just the Red channel?
And to add to my confusion, how are you determining that one channel is not working?
Then for no other reason than it would eliminate or condemn the switch why not un-solder the Red and White wires from the central tags. Now try a shorting link, paper clip or similar, between pins 2 and 3 in the XLR socket. (That links the red and white RCAs together in place of the switch.) Now try parallel mode, do you get output from both channels? If so remove the link and directly solder the red and white wires together, away from the switch and test again, now what do you get?
''I'm a bit lost.'' you are not alone...
Can we recap a little. I'm more than a little confused. (In fact it is difficult to draw any logical reasons for the symptoms described...)
Are you saying that in Parallel mode, if you use the White RCA input you only get output from the White channel? But if you use the Red RCA input you get output from both channels or just the Red channel?
And to add to my confusion, how are you determining that one channel is not working?
Then for no other reason than it would eliminate or condemn the switch why not un-solder the Red and White wires from the central tags. Now try a shorting link, paper clip or similar, between pins 2 and 3 in the XLR socket. (That links the red and white RCAs together in place of the switch.) Now try parallel mode, do you get output from both channels? If so remove the link and directly solder the red and white wires together, away from the switch and test again, now what do you get?
''I'm a bit lost.'' you are not alone...
Sure
In RCA parallel mode we have the good amp connected to the left speaker, the bad to the right.
We left on the side the good amp. So we are only talking of the bad amp that has to inputs Red RCA and White RCA
It is solved.
I would like to express a big thank to Alan4411 who by his support help me understand a bit better what the issues could be help me isolate the PCB from where the problem should come.
I have resoldered everything on that PCB and everything is working like ini the manuals now.
I obviously have done a bad soldering.
Thank you very much for your support Alan.
Vincent
I would like to express a big thank to Alan4411 who by his support help me understand a bit better what the issues could be help me isolate the PCB from where the problem should come.
I have resoldered everything on that PCB and everything is working like ini the manuals now.
I obviously have done a bad soldering.
Thank you very much for your support Alan.
Vincent
Further to my gain 'issues' with thanks to the post above I did some tests. I have 11.5db gain from the ACA so all is well there.
Did a tests and some double checks into my system. DCG3 is definitely set to 2x so I shall try reverting back to the default 3.
And also my DAC (Miro AD1862) I believe I set quite low aswell with a 1.4k R on the output giving 1.4Vp.
Did a test via Spotify a 1k tone and I was getting 650mv from the DCG3 at full tilt.
Hasn't been as issue before but all my other amps are 25 to 28db gain, so it looks like I have some room to give the ACA a bit more breathing room.!
Did a tests and some double checks into my system. DCG3 is definitely set to 2x so I shall try reverting back to the default 3.
And also my DAC (Miro AD1862) I believe I set quite low aswell with a 1.4k R on the output giving 1.4Vp.
Did a test via Spotify a 1k tone and I was getting 650mv from the DCG3 at full tilt.
Hasn't been as issue before but all my other amps are 25 to 28db gain, so it looks like I have some room to give the ACA a bit more breathing room.!
Anyone ever tried putting 100uF polypropylene power film caps across the O/P Electrolytics of their amp camp amp ?
I just did and it's a very nice improvement. I am using these:
https://uk.farnell.com/kemet/c4aqlb...l/dp/2846473?st=capacitors+100uf+polyprolyene
but Panasonic also make some good ones.
Had been using 100uF polyester film caps which were better than no bypass but PP is the way to go.
I just did and it's a very nice improvement. I am using these:
https://uk.farnell.com/kemet/c4aqlb...l/dp/2846473?st=capacitors+100uf+polyprolyene
but Panasonic also make some good ones.
Had been using 100uF polyester film caps which were better than no bypass but PP is the way to go.
While I have not tried this with my ACA builds, I have done very similar things with several of the alternate VFET (lottery) amp front end cards. With smaller values for the electrolytics, I used 1 uF film caps in parallel. Same idea and worked quite well. Polypropylene or polycarbonate tend to sound the best.