Hi all, I'm interested in an Aleph 3 DIY power amplifier, but someone told me to check (and I don't know how because I don't have the possibility to listen to it on my chain) that it doesn't suffer from a slight hum at 100 Hz in the absence of signal , a problem which, again in his opinion, is very common for pure class A amplifiers.
Has anyone who owns or has built the Aleph 3 or other pure class A amplifiers ever actually encountered the problem of slight hum at 100Hz with no signal?
Or could this be a problem that only this person had on one occasion?
Thank you very much
Has anyone who owns or has built the Aleph 3 or other pure class A amplifiers ever actually encountered the problem of slight hum at 100Hz with no signal?
Or could this be a problem that only this person had on one occasion?
Thank you very much
In my AlephX there is no hum with a CRCRC capacitor bank.
I also updraded it with a dual bridge rectifier to eliminate the tiny bit of hum.
Hugo
I also updraded it with a dual bridge rectifier to eliminate the tiny bit of hum.
Hugo
Please, forgive my ignorance but, what's a CRCRC bank, how is it made? Is it the typology suggested in DIY Aleph 3 scheme or it was you to implement that in your gear?
And, before of this and the dual rectifier bridge, in the original version, did you have some hum, even tiny? Have you been able to listen to in normal listening position with no signal?
Thank you.
And, before of this and the dual rectifier bridge, in the original version, did you have some hum, even tiny? Have you been able to listen to in normal listening position with no signal?
Thank you.
Here, you can see that after the rectifier there are 3 banks of large 2200µF capacitors with resistors in between.
Adding these resistors greatly reduces ripple. That's a C (cap) R (resistor) C (cap) and so on, bank.
There was some slight hum in the original AlephX. Nelson's tip to add a dual bridge solved it almost completely.
And with almost, I mean really really quit unless, at night, when all is silent, you push your ear into the speaker cone.
I tend to sleep at night 🙂
A dual bridge can only be made if the transformer has dual secondaries.
While I don't have the depth of technical knowledge of many on this forum, I have played w/ a lot of equipment and never heard this to be an issue of Class A.
A properly designed and constructed Class A amp should not hum. However if the amp is used to drive extremely sensitive speakers (100dB+), and especially if the amp is also single ended, perhaps there may be some audible noise. But that can be taken care of with additional power supply filtration.
The OP mentioned that the amp is a DIY Aleph 3. The DIY aspect may or may not be an issue. The only way to find out is to open it up and find out how it was built.
The OP mentioned that the amp is a DIY Aleph 3. The DIY aspect may or may not be an issue. The only way to find out is to open it up and find out how it was built.
Netlist.... that is not a power supply for the Aleph 3. Appreciate it shows the principal but with a 1.2A bias those 10 ohm resistors between the caps would be dropping 12 volts each not to mention how much power they would take. I have a clone of a well known class A amp, single supply rail and single ended. It does have a small residual hum, very annoying. It has dual supplies with individual rectifiers and increasing the value of the smoothing caps made virtually no difference. I put up with it because it sounds so good.
If increasing the capacitor value did not make a difference, then there were other issues. Single ended Class A amplifiers can be quiet.
If you post pictures of the internals of your amplifier, perhaps there may be visible clues as to the cause of the hum.
I have single ended Class A amplifiers with 103dB speakers and I hear no hum.
If your speakers are very sensitive, a CLC power supply would be quieter than a CRC power supply. I have CLC supplies in my DIY single ended Class A amplifiers.
If you post pictures of the internals of your amplifier, perhaps there may be visible clues as to the cause of the hum.
I have single ended Class A amplifiers with 103dB speakers and I hear no hum.
If your speakers are very sensitive, a CLC power supply would be quieter than a CRC power supply. I have CLC supplies in my DIY single ended Class A amplifiers.
Hello andreaemme,
hello totally analogue,
perhaps you know this text/article from Andrew C. Russell? Could help you to understand, how many reasons
hum or noise can have in an amp.
If it is 50 / 60 Hz (or a multiple... 100/120Hz, 200/240Hz,), I would try a groundloopbreaker and I would check how your grounding is arranged in your amp. One possibility.
But first read this:
https://hifisonix.com/wp-content/uploads/2021/04/Dual-Mono-Wiring.pdf
https://hifisonix.com/wp-content/uploads/2021/04/Reducing-Loop-Area-in-Audio-Amplifiers.pdf
Cheers
Dirk
hello totally analogue,
perhaps you know this text/article from Andrew C. Russell? Could help you to understand, how many reasons
hum or noise can have in an amp.
If it is 50 / 60 Hz (or a multiple... 100/120Hz, 200/240Hz,), I would try a groundloopbreaker and I would check how your grounding is arranged in your amp. One possibility.
But first read this:
https://hifisonix.com/wp-content/uploads/2021/04/Dual-Mono-Wiring.pdf
https://hifisonix.com/wp-content/uploads/2021/04/Reducing-Loop-Area-in-Audio-Amplifiers.pdf
Cheers
Dirk
Correct, it was indeed just the show the principle.
Thanks for clarifying this.
Hugo
Hello! I apologize for my ghosting.... some commitments kept me away longer than expected. I investigated, from some photos of the amplifier in question I can clearly see that the filtering stage includes capacitors and resistors and that the rectifier bridge is double, yet the owner himself tells me that in fact a bit of 100 Hz hum can be heard in absence of signal but which is not at all annoying and should be considered normal. I don't know how much because I couldn't try it but in the end I preferred to abandon the idea of buying it, I'll never know if it was due to a something wrong or unexpected in assembly.
I thank everyone for their valuable contribution.
I thank everyone for their valuable contribution.
Back in the 60s and 70s, yes I'm an oldy, hum was a given. Circuit design and build of amplifiers has improved enormously over the intervening decades and the issues with hum seem to have been gripped. Even my Prima Luna tube amp is completely quiet with no signal. That said I have a copy of classic 70s class A amp and one of it's features is residual hum. As you describe it is very low level and can only be heard when you are right in front of the speakers. At the listening position its fine. I improved it slightly by uprating the mains transformer but as I said its a given with that design and no way does it distract from the listening experience.
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