How about the series resistor in the input
that form a filter for HF
together with a small cap that goes to ground.
Can sometimes be like 1-2.2kohm and 0.1-1nF
And the zener(s) that set the reference voltage for
the input transistors' current source(s)
Are the caps there okay?
that form a filter for HF
together with a small cap that goes to ground.
Can sometimes be like 1-2.2kohm and 0.1-1nF
And the zener(s) that set the reference voltage for
the input transistors' current source(s)
Are the caps there okay?
Hmm, the input is direct coupled. However, I'll look at the input network. I think the circuitry is all fine since both channels sound alike and the quality of the music is actually very good. It's just that the gain is so darn high. I think I'll make a front end specifically for this amp though. The one I'm using is the one in my
Harman/Kardon HK A402 amp. It's designed with preamp outputs and main amp inputs so i'm just feeding the preamp outs into the sanyo. The reason is that the HK front end sounds so sweet and clean.
Harman/Kardon HK A402 amp. It's designed with preamp outputs and main amp inputs so i'm just feeding the preamp outs into the sanyo. The reason is that the HK front end sounds so sweet and clean.
seems the noise is only with open input, so that is no problem
Harman/Kardon products often sounds very good 😉
Harman/Kardon products often sounds very good 😉
Open input
No cable from source connected to input, and input not short circuited to ground.
I do not know if that is the correct term used.
But that is what my brain associates to.
No cable from source connected to input, and input not short circuited to ground.
I do not know if that is the correct term used.
But that is what my brain associates to.
When I do that the noise actually quits completely. It seems to be that the noise is coming from the HK. I know how stupid that sounds since HK's are so nice. Also, my HK never hisses when it's own amplifier is connected to the preamp....
Weird.
Weird.
Some sort of mismatch.
How high is input impedance of Sanyo?
It can also be how the 2 devices' grounds are connected together.
How high is input impedance of Sanyo?
It can also be how the 2 devices' grounds are connected together.
The input impedance on the sanyo is very verr high. Probably in the 50k range. I konw the output impedance on my HK is quite low and capable of driving high amounts of current.
Hissing
Duo,
There might be a large series input resistor on the Sanyo. If that is 50K it is more like a noise generator. Open-circuit there is no noise because one end of the resistor floats. Short circuited the noise will have a reference and it gets in the amp. Same with the HK connected: the "noise generator" is grounded through the HK output impedance which is probably quite low.
Just speculating really, but see if you can figure out the input circuitry of the Sanyo. This series resistor, if it's there, may have had a function in the original setup but maybe you can just delete it.
Jan Didden
Duo,
There might be a large series input resistor on the Sanyo. If that is 50K it is more like a noise generator. Open-circuit there is no noise because one end of the resistor floats. Short circuited the noise will have a reference and it gets in the amp. Same with the HK connected: the "noise generator" is grounded through the HK output impedance which is probably quite low.
Just speculating really, but see if you can figure out the input circuitry of the Sanyo. This series resistor, if it's there, may have had a function in the original setup but maybe you can just delete it.
Jan Didden
That's a good idea. The circuitry in the amp is quite easy to determine since the design is quite basic...
I'll see how the input network is connected and see what I can do. I see your point since that HK front end is very low impedance. Almost like usin Emitter Coupled Logic in a computer monitor which is high current and fast switching with very low slew rate. I could probably put a 600 to 2k ohm resistor in there instead and the loading would be perfect.
Thanks, I think that might be the solution.
DUo....
I'll see how the input network is connected and see what I can do. I see your point since that HK front end is very low impedance. Almost like usin Emitter Coupled Logic in a computer monitor which is high current and fast switching with very low slew rate. I could probably put a 600 to 2k ohm resistor in there instead and the loading would be perfect.
Thanks, I think that might be the solution.
DUo....
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