Absolutely right Patrick, although one mostly sees
Panasonic parts in his amps. Being good solid components, they dont count as being exotic. You dont see outragously expensive parts in Pass amps. As usual, its the circuit that sings, not the parts
You can go for expensive audiophile parts throughout and end up with an amp that costs 1/2 a million, sounding a fraction better (with a little good will ) than one costing 2K$.I am not saying that you should skimp on quality, just that its plain crazy to spend several hundreds of $ on a single cap.
Good solid quality standard parts, is the way forward.
Steen
Chasing the hum out of my aleph-x
Dear aleph-x builders, maybe one of you can help me with a problem I cannot solve despite reading all your posts.
I recently finsihed a pair of low power aleph-x monoblocks, they both worked at once and sound amazing! Best amps I have built, even compared to my zen V9!
Specs are: 14.3 V rail voltage, one rectifier bridge per channel, CRC filter with 3x 22mF, 0.2 ohm resisitor (5x 1R) followed by 2x22mF caps. 4 IRFP044 per channel, bias is 4A per side, current source set around 50%, relative offset around 20mV. I guess it is a typical low power configuration.
The problem is that one of the channels has a slight hum coming out of my 96db efficient speaker, while the other monoblock is absolutely quiet. By exhanging transformers, power supply, rectifiers and output boards between the two monoblocks I narrowed down the problem to the mainboard of the humming channel.
Here comes the strange thing that puzzles me: When I look at the output of the humming channel I see the following: The there is 100Hz oscillation only at the + output (measured to ground), the - output on the humming monoblock looks just like the + and - outputs of the silent channel. (+ output is the bottom trace and - output the top trace in the picture below). Amplitude of the oscillation is around 20mV.
How can it be that PS noise shows up only on one side (the + in my case) of the output?
Any suggestions for troubleshooting?
Thanks for any ideas.
Dear aleph-x builders, maybe one of you can help me with a problem I cannot solve despite reading all your posts.
I recently finsihed a pair of low power aleph-x monoblocks, they both worked at once and sound amazing! Best amps I have built, even compared to my zen V9!
Specs are: 14.3 V rail voltage, one rectifier bridge per channel, CRC filter with 3x 22mF, 0.2 ohm resisitor (5x 1R) followed by 2x22mF caps. 4 IRFP044 per channel, bias is 4A per side, current source set around 50%, relative offset around 20mV. I guess it is a typical low power configuration.
The problem is that one of the channels has a slight hum coming out of my 96db efficient speaker, while the other monoblock is absolutely quiet. By exhanging transformers, power supply, rectifiers and output boards between the two monoblocks I narrowed down the problem to the mainboard of the humming channel.
Here comes the strange thing that puzzles me: When I look at the output of the humming channel I see the following: The there is 100Hz oscillation only at the + output (measured to ground), the - output on the humming monoblock looks just like the + and - outputs of the silent channel. (+ output is the bottom trace and - output the top trace in the picture below). Amplitude of the oscillation is around 20mV.
How can it be that PS noise shows up only on one side (the + in my case) of the output?
Any suggestions for troubleshooting?
Thanks for any ideas.
Attachments
Re: Re: Re: Chasing the hum out of my aleph-x
remember-that's X.....twisted in phases and feedbacks
but-also mea culpa,I didn't meant just on input CCS,but also on LTP
you have problem;
just heat your Iron and go for it ;
when you find what is ,I'm sure that you'll laugh .
probably nobody from forum can't tell you what is fer sure.
you can start from output current source(s),if you wish
1001meier said:
remember-that's X.....twisted in phases and feedbacks
but-also mea culpa,I didn't meant just on input CCS,but also on LTP
you have problem;
just heat your Iron and go for it ;
when you find what is ,I'm sure that you'll laugh .
probably nobody from forum can't tell you what is fer sure.
you can start from output current source(s),if you wish
Blues said:
Hi Allan,
this is exactly what I have been doing the past few days. In the attached diagram I indicated with red circles the noisy region and green squares the quiet parts. It looks like noise enters after the feedback capacitor (C4)/ resistor (R30). I already changed Q8 without improvement.
So it seems like the CCS is the source of trouble?
Great forum, glad to get all this feedback and hope it will help others!
Attachments
flg said:I don't see the McMillan R's in that schemo???
2.2K would possibly be the value??? Post #134???
even if I didn't make any X yet,I'm not sure that lack of McMillan's can be culprit for that ripple;
without them DC behavior of circuit is certainly degraded ........in any case-that's first Gray's schematic,from era without McMillans....
I'm pretty sure that meier have them in place..........
I'm still with bad solder point ,or defective bjt or output mosfet ,as culprit for his problems......
he will tell us,I hope....when he find what is........
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