Yes, thank you, but than I'll have 10k at the preamp output parallel to 100k(R13) at the MyRef input, and I'm not sure is that going to influence the performance as the input impedance of MyRef is going to be changed... Maybe I could waste the 10k at the preamp output and have 100K at the input to act as a discharge path for the output cap as well as to set the input impedance?
We are talking about ~250VDC or more before preamp output cap...
We are talking about ~250VDC or more before preamp output cap...
It should be fine, but to be on the safe side:
1) Disconnect preamp from MyRefC
2) Lift 10k.
3) Add a 100K resistor to ground at output.
4) Check DC.
Of course you should check DC at preamp's power on and power-off. There shouldn't be any DC, or the cap is leaking.
the output resistor takes cap leakage to ground when the interconnect is not connected.
The leakage should be tiny.
A 1M0 or 2M2 resistor will do that job as long as you have not used an electrolytic nor leaky paper.
Similarly, the grounding resistor at the input before the DC blocking cap only has a job to do when the interconnect is not connected. It too can be 1M0 or 2M2.
When the interconnect is connected, these two grounding resistors are effectively in parallel, giving 500k or 1M1 of extra load to the cabling and transmitter/receiver.
The bigger the better for these resistors.
If you can guarantee that the interconnect cannot be disconnected then both resistors can be made of infinite value (the higher the better). This applies when the transmitter and receiver are soldered together.
Further, DC blocking is only required once in a single transmit/receive connection. Allow one of the DC blockers to be bypassed when you know that the other can do the job alone.
The leakage should be tiny.
A 1M0 or 2M2 resistor will do that job as long as you have not used an electrolytic nor leaky paper.
Similarly, the grounding resistor at the input before the DC blocking cap only has a job to do when the interconnect is not connected. It too can be 1M0 or 2M2.
When the interconnect is connected, these two grounding resistors are effectively in parallel, giving 500k or 1M1 of extra load to the cabling and transmitter/receiver.
The bigger the better for these resistors.
If you can guarantee that the interconnect cannot be disconnected then both resistors can be made of infinite value (the higher the better). This applies when the transmitter and receiver are soldered together.
Further, DC blocking is only required once in a single transmit/receive connection. Allow one of the DC blockers to be bypassed when you know that the other can do the job alone.
That resitors is part of the topology of the improved howland current pump.
It's necessary and it's value is critical, 0.2R is probably too low.
"Throw away your pre-amp."
That is easy enough, thank you
.
I just realized that I asked the question, a wrong way.
What is the best value for the input pot, bearing in mind that my amp is DC coupled?
I see the values of 10k - 22k- 50k- 100k mentioned, but could not find any data DC coupled design specific. I think 100k is obvious choice but wanted to hear another opinion.
Thank you
That is easy enough, thank you
. I just realized that I asked the question, a wrong way.
What is the best value for the input pot, bearing in mind that my amp is DC coupled?
I see the values of 10k - 22k- 50k- 100k mentioned, but could not find any data DC coupled design specific. I think 100k is obvious choice but wanted to hear another opinion.
Thank you
Hi
After about a week of good sound and no problems at all from the first power on, my amp developed strange sibilance effect. I use audio grade parts, like PRP,Takman, Nichicon etc. Tried to increase C9 to 1000uF(C1 2.2uF/ R13 100k) and a different capmaker, but sibilance stayed.
Now, one channel does not work (relay will not click) and I killed 3pcs of LM 318 so far.
If I take out LM 318 there are no voltages on its socket pins apart from +/-12VDC(pin4 -vdc, pin7+vdc) as it should be. With 318 taken out amp will power on relay will click and there is no DC on the output. If I put LM 318 in the socket there will be various +/- voltages around 12V on all of it's pins that are used and there is ~-25VDC at the output pin of the 3886.
No smoke, no heat, at all. I made a simple circuit on the proto board and it showed me that any 318 is dead after I put it in the socket and power on the amp. I'm not sure if 3886 is dead I can't see anything wrong with the voltages its showing with 318 taken out (no DC on the output).Only thing that is strange, its mute pin is getting less than a volt. I've spent several hours staring at the board, no shorts, wrong value parts, lifted pads etc- the amp was working about 10 hours per a day, moderate power, for a week or so- hard that I misswired something. I use TF chip with HUGE HS. Any ideas? Dead 3886?
Thank you
After about a week of good sound and no problems at all from the first power on, my amp developed strange sibilance effect. I use audio grade parts, like PRP,Takman, Nichicon etc. Tried to increase C9 to 1000uF(C1 2.2uF/ R13 100k) and a different capmaker, but sibilance stayed.
Now, one channel does not work (relay will not click) and I killed 3pcs of LM 318 so far.
If I take out LM 318 there are no voltages on its socket pins apart from +/-12VDC(pin4 -vdc, pin7+vdc) as it should be. With 318 taken out amp will power on relay will click and there is no DC on the output. If I put LM 318 in the socket there will be various +/- voltages around 12V on all of it's pins that are used and there is ~-25VDC at the output pin of the 3886.
No smoke, no heat, at all. I made a simple circuit on the proto board and it showed me that any 318 is dead after I put it in the socket and power on the amp. I'm not sure if 3886 is dead I can't see anything wrong with the voltages its showing with 318 taken out (no DC on the output).Only thing that is strange, its mute pin is getting less than a volt. I've spent several hours staring at the board, no shorts, wrong value parts, lifted pads etc- the amp was working about 10 hours per a day, moderate power, for a week or so- hard that I misswired something. I use TF chip with HUGE HS. Any ideas? Dead 3886?
Thank you
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