Feedback Loop help

KevinLee · 30th November 2002, 11:58 PM

Hello Everyone,

I have a Rotel RA930AX integrated amplifier. I have completed numerous upgrades such as:

-discreet bridge built with soft recovery diodes.

-bypassed all tone controls and hardwired with Nordost cable from input to volume control. (now only one source can be used).

-replaced all applicable caps with Elna Cerafine.

-added 22000uf Elna Cerafine caps to power supply.

-Changed op-amp to AD827.

-Replaced all resistors with Roederstein metal film.

-Paralled .1UF Solen and .01 Teflon(russian) cap in power supply.

-Removed plastic covers from all caps including the 22000uf ones and put a damping material on the caps.

-Replaced speaker outputs with better Vampire units (hard wired to board with Nordost cable. Also replaced RCA inputs.

That is about the extent of the upgrades so far.

I plan on upgrading the volume control.

What I want help with is identifying which components are in the feedback loop. I want to replace these components with better resistors/capacitors.

Does anybody have a schematic and can help me identify them?.

I am not too good with circuit topology.

Also, what would be the next logical upgrade to do to this amp.

Thanks for reading all this.

Cheers
KevinLee

halojoy · 1st December 2002, 12:16 AM

Feedback always comes from the output.
Usually before the output relay
and between the output transistors.
But I guess you can not see the bottom side of the circuit.
So a schematic would be best.

KevinLee · 1st December 2002, 12:23 AM

Thanks Halajoy.

My amp does not have relays.

I can trace the circuit if you can help me with what I am looking for.

KevinLee

halojoy · 1st December 2002, 01:36 AM

From the output point,
there should be 1 or two small resistors going
in direction to the input transistors.
Often is a small capacitor right beside the resistor.
They are in parallell.

It can also be a track that goes halfway from the output
back towards the input.
and then the resistor/cap is closer to the input.
The input is mostly one or two pairs of transistors,
with close body contact to eachother.

KevinLee · 1st December 2002, 01:39 AM

Thanks again halajoy!

I will check it out and let you know how I made out.

KevinLee

30th November 2002, 11:58 PM	#1
KevinLee diyAudio Member Join Date: Oct 2002 Location: Winnipeg MB Canada	Feedback Loop help Hello Everyone, I have a Rotel RA930AX integrated amplifier. I have completed numerous upgrades such as: -discreet bridge built with soft recovery diodes. -bypassed all tone controls and hardwired with Nordost cable from input to volume control. (now only one source can be used). -replaced all applicable caps with Elna Cerafine. -added 22000uf Elna Cerafine caps to power supply. -Changed op-amp to AD827. -Replaced all resistors with Roederstein metal film. -Paralled .1UF Solen and .01 Teflon(russian) cap in power supply. -Removed plastic covers from all caps including the 22000uf ones and put a damping material on the caps. -Replaced speaker outputs with better Vampire units (hard wired to board with Nordost cable. Also replaced RCA inputs. That is about the extent of the upgrades so far. I plan on upgrading the volume control. What I want help with is identifying which components are in the feedback loop. I want to replace these components with better resistors/capacitors. Does anybody have a schematic and can help me identify them?. I am not too good with circuit topology. Also, what would be the next logical upgrade to do to this amp. Thanks for reading all this. Cheers KevinLee

1st December 2002, 12:16 AM	#2
halojoy On Hiatus Join Date: Nov 2002	Feedback localisation Feedback always comes from the output. Usually before the output relay and between the output transistors. But I guess you can not see the bottom side of the circuit. So a schematic would be best.

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1st December 2002, 12:23 AM	#3
KevinLee diyAudio Member Join Date: Oct 2002 Location: Winnipeg MB Canada	Thanks Halajoy. My amp does not have relays. I can trace the circuit if you can help me with what I am looking for. KevinLee

1st December 2002, 01:36 AM	#4
halojoy On Hiatus Join Date: Nov 2002	From the output point, there should be 1 or two small resistors going in direction to the input transistors. Often is a small capacitor right beside the resistor. They are in parallell. It can also be a track that goes halfway from the output back towards the input. and then the resistor/cap is closer to the input. The input is mostly one or two pairs of transistors, with close body contact to eachother.

1st December 2002, 01:39 AM	#5
KevinLee diyAudio Member Join Date: Oct 2002 Location: Winnipeg MB Canada	Thanks again halajoy! I will check it out and let you know how I made out. KevinLee

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