Onkyo A-8800 (1989) need advice for mod and lower the sensitivity

RuslanK35

Member
2019-06-21 1:51 am
Hello. I need your opinion about way to modifications the amplifier Onkyo A-8800.
First of all, I would like to know you opinions, what is the best way to reduce the sensitivity of the amplifier? I deleted many unnecessary for me elements and boards from Onkyo, including the volume control. I want to adjust the volume using the external DAC. Until I dont made the dac DIY, the source is the iPhone. But I have a problem: overly sensitive input without an amplifier volume control. Only two volume stage in iPhone is already loud. Second problem: hissing from the speakers began to be heard. Even with the sound source disconnected from the Onkyo amplifier. This is a tip. I replaced the wire going from the CD input directly to the amplifier board with a shielded one, this helped and removed almost all the background noise, but a bit of it remained. If I'm right, this is due to input sensitivity.With out volume control resistor the amplifier feels the smallest values of Interference and amplifies them into noise
At the Russian-language forum, I was offered two solutions:
a. Put an input divider on the resistors.
b. Change the values ​​of the resistors in the in the negative feedback circuit (R507 R509) to reduce the gain.
My knowledge is not enough to understand which of the options is preferable. I would ask for your advice.
My second question about ways to modification this amplifier for better sound. I have already removed from it everything that I do not need (noted in the photo with red crosses). Replaced all electrolytic capacitors with better ones. But since I am a beginner, I cannot understand:
a. Which capacitors are loop-through in the amplifier circuit? I would like to know what would remove electrolytic capacitors from the signal path and put film or jumpers.
b. Do I need to change the diode bridge? And does it make sense to shunt large electrolytic capacitors at the input with film?
c. On photo I mark by green marker the JL102. if I not mistake, JL102 is the power for the phono corrector board? if so, all capacitors marked green are not need for me, since I completely removed the board with the phono stage? I ask because I want to remove all the capacitors that became unnecessary after my modifications of the Onkyo. I remember what I removed: the DAC board, the entire board with an input selector, the volume control with the tone control board, the board with a phono stage. The input signal is sent from RCA (CD IN) directly to the P501.
Thank you.
 
Hello. I need your opinion about way to modifications the amplifier Onkyo A-8800.
First of all, I would like to know you opinions, what is the best way to reduce the sensitivity of the amplifier? I deleted many unnecessary for me elements and boards from Onkyo, including the volume control. I want to adjust the volume using the external DAC. Until I dont made the dac DIY, the source is the iPhone. But I have a problem: overly sensitive input without an amplifier volume control. Only two volume stage in iPhone is already loud. Second problem: hissing from the speakers began to be heard. Even with the sound source disconnected from the Onkyo amplifier. This is a tip. I replaced the wire going from the CD input directly to the amplifier board with a shielded one, this helped and removed almost all the background noise, but a bit of it remained. If I'm right, this is due to input sensitivity.With out volume control resistor the amplifier feels the smallest values of Interference and amplifies them into noise
At the Russian-language forum, I was offered two solutions:
a. Put an input divider on the resistors.
b. Change the values ​​of the resistors in the in the negative feedback circuit (R507 R509) to reduce the gain.
My knowledge is not enough to understand which of the options is preferable. I would ask for your advice.
My second question about ways to modification this amplifier for better sound. I have already removed from it everything that I do not need (noted in the photo with red crosses). Replaced all electrolytic capacitors with better ones. But since I am a beginner, I cannot understand:
a. Which capacitors are loop-through in the amplifier circuit? I would like to know what would remove electrolytic capacitors from the signal path and put film or jumpers.
b. Do I need to change the diode bridge? And does it make sense to shunt large electrolytic capacitors at the input with film?
c. On photo I mark by green marker the JL102. if I not mistake, JL102 is the power for the phono corrector board? if so, all capacitors marked green are not need for me, since I completely removed the board with the phono stage? I ask because I want to remove all the capacitors that became unnecessary after my modifications of the Onkyo. I remember what I removed: the DAC board, the entire board with an input selector, the volume control with the tone control board, the board with a phono stage. The input signal is sent from RCA (CD IN) directly to the P501.
Thank you.


Too bad you took out the volume control ... The easiest way to turn down the sensitivity is to simply turn down the volume.

If you want to control the volume from your dac... go for it. No need to mod your amp to do it.
 
Hello. I need your opinion about way to modifications the amplifier Onkyo A-8800. First of all, I would like to know you opinions, what is the best way to reduce the sensitivity of the amplifier? I deleted many unnecessary for me elements and boards from Onkyo, including the volume control.
Bad choice
With out volume control resistor the amplifier feels the smallest values of Interference and amplifies them into noise
Exactly where are you feeding in the audio?
At the Russian-language forum, I was offered two solutions:a. Put an input divider on the resistors.
That would be equivalent to turning down the volume control. Depending on where you are feeding the audio in, you would want to reduce the value of R501 (the 1M) to, perhaps 10K, and increase the other R501 (1K) to perhaps 10K. If it is still too sensitive, increase the R501 that was 1K further, maybe as high as 100K. It's something you will need to experiment with.
b. Change the values ​​of the resistors in the in the negative feedback circuit (R507 R509) to reduce the gain.
Not unless you are an audio engineer and can do the calculations to confirm the amplifier is still stable.
My knowledge is not enough to understand which of the options is preferable. I would ask for your advice.
You really should have left it alone. The parts you 'removed' gain you nothing.
My second question about ways to modification this amplifier for better sound.
I have already removed from it everything that I do not need (noted in the photo with red crosses).
Dangerous and useless action.
Replaced all electrolytic capacitors with better ones. But since I am a beginner, I cannot understand:
If you are a beginner and cannot understand, how do you know you replaced the capacitors with 'better ones'?
a. Which capacitors are loop-through in the amplifier circuit? I would like to know what would remove electrolytic capacitors from the signal path and put film or jumpers.
The old saying is "If it isn't broke, don't fix it. You are only looking for more problems.
b. Do I need to change the diode bridge? And does it make sense to shunt large electrolytic capacitors at the input with film?
No, and no.
c. On photo I mark by green marker the JL102. if I not mistake, JL102 is the power for the phono corrector board? if so, all capacitors marked green are not need for me, since I completely removed the board with the phono stage? I ask because I want to remove all the capacitors that became unnecessary after my modifications of the Onkyo. I remember what I removed: the DAC board, the entire board with an input selector, the volume control with the tone control board, the board with a phono stage. The input signal is sent from RCA (CD IN) directly to the P501.
Thank you.
All I can say is "Good Luck".