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How to make a RCA output for subwoofer on Reisong A10

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R

RV1938

Member
Joined 2021
#1
Hello
I need your help please, I bought my first tube amplifier the reisong A10

But there is not output rca signal to connect a subwoofer.
The tubes technologie is new for me...

Importants things I need:
-the output volume of the rca must vary in the same time of the speaker volume. This will make a 2.1 system.
-Important things is the stereo I don't want to make a bridge in the input signal....Respect the dual mono mode / stereo mode

Could you tell me if I'm right if do this please ? maybe some coupling capacitors must be introduce ? I don"t want to destroy somethings.

modify.jpg



I join you just a part "preamp stage" of the schematics of the amp I found on google

preamp stage .png



I hope you could help me please, I thank you 🙂
 
#2
That's the idea. However, it would work best with a 10k volume control instead of the present 100k control.
There will be some reduction of channel separation due to the passive summing circuit connecting the two channels.

What sources do you have? If they are not tube sources, a 10k volume control would work better for this purpose.
Also use 10k resistors instead of 1k resistors for the summing circuit.
 
#3
Thank for the answer rayma, but I have'nt not other potentiometer, it's the original 100k.....
I have no tube source. I have rca signal from tv.
But if I use 1k in my schematics the signal will be bridge? and reduce the diaphonie ?
If I buy and change the original with a 10k, Do I need to change the 470k ?
And do I need to put coupling capacitor or not ?
Thanks
 
#4
You can try it with the 1k resistors, and see if you hear any problem with the channel separation.
There will be some reduction, but with TV that should be ok.

The 470k should stay in place in any case.
No coupling capacitor is needed, since the TV will have one at its output.
 
#5
I thank you, in fact I use tv to listen music so channel separation is really important, Otherwise I can try directly with a 2k resistors ?
what is the maximum value I can use without having problem of low output volume ?
Thanks
 
#7
it's an SVS home subwoofer, I search an see differents schematics other people use two 10k resistors and I also found a circuit with on AOP 5532 to bridge the signal, maybe it's the best way to avoid problem of channel separation ?
 
#16
RV1938 said:
the input capacitors C1 and C2 + resistors avoid the problem or return the signals and block it
Click to expand...

No, the capacitors are only required due to the single supply. And there is no decoupling for the noninverting input.

See the circuit in post #8 for a proven dual supply circuit that will work, and work well.
I do not understand why you are looking for other circuits, when the circuit in post #8 is appropriate.
 
#19
RV1938 said:
Could you tell me if I'm right if do this please ? maybe some coupling capacitors must be introduce ? I don"t want to destroy somethings.

View attachment 1100952
Click to expand...

This will work just fine if you increase the value of the mixing R's quite a lot, maybe starting with 1M Ohms each. Modern subwoofers will have an input impedance around 10K Ohms, so there is appreciable loss in the passive mixer. If 1M Ohms each does give enough signal, with the subwoofer's gain turned wide open (don't worry, it's just a gain control), reduce that value to 1/2M Ohm and try again.

Your design goal is to have the largest possible resistor value (to maintain channel isolation) with just enough summed signal to drive your sub. Ideally, you'd grab this from a lower impedance location, but your choice above will work fine and with minimal complication. Well worth trying first, at least.

All good fortune,
Chris
 
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