Hi fellas,
Thanks for your help again as always.
Since the last post I have aimed to isolate all outputs by using a 3D printed back plate instead of the aluminum one to avoid all possibility of accidental contacts.
So far so good, I'm testing the unit now. In case it was my mods that were impacting things before, I am running the amps stock, without the replacement capacitors or resistors.
However I have noticed that in bass heavy songs, the right speaker seems to be distorting at the bassier parts.
Could this be related to the guage of cable I am using?
From input plug to EMI filter: 1.5mm thick
From EMI to Power Supply input: 1.5mm thick
From Power Supply to each amp board: 1mm thick
From amp board to speaker terminals: 1mm thick
From RCA Inputs to 10k pot and from pot to amp board: 0.75mm.
Could it be that the power supply isn't supplying enough juice to the amp boards? It is a 24V 3A power supply..
Or could the problem be somewhere else in the chain? I can only hear the distortion on bass beats and on the right speaker. Might the problem be resolved when I add the large input caps and change the board to class ABD?
Thanks again for all your help! I can feel I'm almost there!
Thanks for your help again as always.
Since the last post I have aimed to isolate all outputs by using a 3D printed back plate instead of the aluminum one to avoid all possibility of accidental contacts.
So far so good, I'm testing the unit now. In case it was my mods that were impacting things before, I am running the amps stock, without the replacement capacitors or resistors.
However I have noticed that in bass heavy songs, the right speaker seems to be distorting at the bassier parts.
Could this be related to the guage of cable I am using?
From input plug to EMI filter: 1.5mm thick
From EMI to Power Supply input: 1.5mm thick
From Power Supply to each amp board: 1mm thick
From amp board to speaker terminals: 1mm thick
From RCA Inputs to 10k pot and from pot to amp board: 0.75mm.
Could it be that the power supply isn't supplying enough juice to the amp boards? It is a 24V 3A power supply..
Or could the problem be somewhere else in the chain? I can only hear the distortion on bass beats and on the right speaker. Might the problem be resolved when I add the large input caps and change the board to class ABD?
Thanks again for all your help! I can feel I'm almost there!
Flip the outputs to make sure the speakers are not faulty.
And is the power supply adequate?
That is common if the power supply sags under load.
As a stop gap, put huge caps on the DC rails. See what happens, see the voltage with an analog meter, if it fluctuates too much, your supply is at fault.
Digital meters will not respond as fast as analog meters.
The other posters have pointed out other possible faults, this is an addition.
And is the power supply adequate?
That is common if the power supply sags under load.
As a stop gap, put huge caps on the DC rails. See what happens, see the voltage with an analog meter, if it fluctuates too much, your supply is at fault.
Digital meters will not respond as fast as analog meters.
The other posters have pointed out other possible faults, this is an addition.
It could be a bad speaker / crossover.
The amp, if at fault, could be checked as outlined in other posts.
And a bad tiny electrolytic in the input stage could cause weird random issues.
At first glance, the power supply looks puny.
When does this happen?
At how much percent power?
Power fault will be less at lower volumes, that is a clue.
Overheating chip amp, or typical no name faulty chip amp are also possible culprits.
The amp, if at fault, could be checked as outlined in other posts.
And a bad tiny electrolytic in the input stage could cause weird random issues.
At first glance, the power supply looks puny.
When does this happen?
At how much percent power?
Power fault will be less at lower volumes, that is a clue.
Overheating chip amp, or typical no name faulty chip amp are also possible culprits.
Hi guys,
Thanks for the help so far.
I have rebuilt the amp, but have a strange issue, or at least more info on the static noise increasing.
So I hooked it up just before after performing the ABD mod, and interestingly everything started out crystal clear but then static noise started increasing again.
I had a poke around the amp and then was shocked at how hot the 2x 2W resistors that are part of the mod got.
I let it rest for a tic and then turned it on, and again, the noise increased as the resistors increased in temperature.
They are quite large resistors, and running parallel would mean they should be able to cope with 4w of power total I would think.
Does anyone have any clues as to what might be happening there? Why would the resistors be getting so hot? What can I do other than get larger resistors to replace them with?
Thanks in advance for any help offered!
Thanks for the help so far.
I have rebuilt the amp, but have a strange issue, or at least more info on the static noise increasing.
So I hooked it up just before after performing the ABD mod, and interestingly everything started out crystal clear but then static noise started increasing again.
I had a poke around the amp and then was shocked at how hot the 2x 2W resistors that are part of the mod got.
I let it rest for a tic and then turned it on, and again, the noise increased as the resistors increased in temperature.
They are quite large resistors, and running parallel would mean they should be able to cope with 4w of power total I would think.
Does anyone have any clues as to what might be happening there? Why would the resistors be getting so hot? What can I do other than get larger resistors to replace them with?
Thanks in advance for any help offered!
Interesting adventure.
I at one point experimented heavily with the Cheap Ali express Junk amps Must have bought 2 dozen of the things over a couple of years .
Even dutifully did ALL of the 'forum' improvement of the month to each.
ALL proved as worthless/ineffective.. grrr..
Eventually trash binned the lot in frustration .
Finally built a wee 1875 amp using 1st world genuine parts. And a dual rail traditional (torroid) power supply... 3 years later it's working 'Fine'.
No it's not the worlds best amp but it has good clean sounds and it's proven reliable .
You could do FAR worse... I certainly did.
I at one point experimented heavily with the Cheap Ali express Junk amps Must have bought 2 dozen of the things over a couple of years .
Even dutifully did ALL of the 'forum' improvement of the month to each.
ALL proved as worthless/ineffective.. grrr..
Eventually trash binned the lot in frustration .
Finally built a wee 1875 amp using 1st world genuine parts. And a dual rail traditional (torroid) power supply... 3 years later it's working 'Fine'.
No it's not the worlds best amp but it has good clean sounds and it's proven reliable .
You could do FAR worse... I certainly did.
Speaking of processors, what happens if you connect one of those high sensitivity horns to a "quiet" AVR? This is my perpetual quest for understanding how products with S/N or SINAD at like 97 dB into a 107 dB horn should play at like 10 dB and be inaudible. But that's not true and hiss is a problem. Yeah SINAD isn't residual noise, and come to think of it my math is off because if the amp is say 100W then the S/N would be 77 dBW and the horn output 40 dB. I guess that IS audible in a quiet room? And forget the AVR or indeed most processors?
I think the answer to your quest is here:
https://audiosciencereview.com/forum/index.php?threads/minidsp-flex-htx.49512/post-1906197
I'm taking the opportunity to test the math that I got from the post linked above. I could be making mistakes, but I it seems to correlate to what I've experienced.
As an arbitrarily chosen example, the Emotiva MR1L 9.2 channel AVR, they say it is greater than 105dB signal to noise, max output voltage is 6v. I'm getting 33.7µV "residual noise". That is kind of loud, but probably fine for lower sensitivity speakers.
Emotiva don't rate the gain of the amplifier section, but all the Emotiva amplifiers appear to be 29dB gain, so I assume the AVR amplifier section is the same. So 33.7µV * 29dB = 949µV.
Then the amplifier appears to be rated at 85µV, so combining 95 and 949 is 952µV. And 952µV into 107dB sensitivity driver is approx 37dB @ 1 meter. This will be quite audible!
This scenario would be quite similar to my recent experience. I had a DSP unit that had similar residual noise to what is estimated above, plus an amp with 29dB gain with similar noise. The hissing from my horns was audible even with a -20dB L-Pad. I upgraded to a much quieter DSP unit, and my system became almost silent. Now I can barely hear a hiss if I put my ear up to the horn.
One important lesson I learned is that the amplifier gain matters as much or more than the noise produced by the source, and the amp's residual noise may not matter very much if at all.