Roland KC350 - Tapping into power amp question

[Danny Troy]

I know very little about electronics, and thought I'd ask the question here, before I fry my amp.

I want to bypass the Roland's preamp and access the power amp directly. I use a 12 channel mixer mounted permanently to the side of the Roland amp, and plug the output of the mixer into a channel on the Roland. I know this isn't ideal, as the signal is traveling through two preamps. I actually did this mod on a Behringer amp, and it worked out fine. That said, this is a much more expensive amp, and I don't want to chance screwing it up!

The schematic shows CN4 from the preamp to the CN9 connector on the amp, with 4 leads. Am I correct in assuming the white lead is the positive and one of the blacks is the ground. Would tapping into the leads at this connector give me what I want, or is CN4/CN9 not the right connectors? Thanks for any help....

[Enzo]

Hi, and welcome. We like to help, but good form would be to post or link the schematic. I'll see if I can find one in the meantime. Otherwise we have no idea what connector does what or what each wire does.

I found a photo. On the rear is the "stereo link" jacks. The IN one is an input to the power amp, so no work needs to be done, the amp already has what you want.


On the other hand, if the way you have been doing it sounds OK, then it IS OK. The fact it goes through more preamp circuits is irrelevant. What matters is results.

[Danny Troy]

Hi, and welcome. We like to help, but good form would be to post or link the schematic..

No problem. I actually found the link to the schematic in this forum. http://music-electronics-forum.com/a...c-550-copy.zip

I'm not familiar with how to decipher schematics, but my hunch seems to be correct. Since I posted the question, I unplugged the 4-pin connector at the power amp and tried the signal from the preamp, using the white and black leads, to another power amp. I got good audio output. I didn't try using another preamp into the power amp. I'll try that tomorrow.

Funny how the Roland is pretty much an exact copy of the Behringer (or more likely the other way around) in it's parts layout. Whether I will get cleaner audio skipping the preamp in the Roland remains to be seen. Worth a try, I guess.

[Enzo]

Did you follow my suggestion? The "stereo link" jacks would be labelled the FX loop in any other amplifier. The send is the preamp out, the return is the power amp in. There is no need to go inside the amp to do any of the routing you propose. But to answer your question, yes you could bust into the wires to accomplish it if you desire.

I was a bit surprised to find the return comes in before teh master volume and EQ, but no harm in that. Gives you extra EQ control and a . well, master volume.


Now that you mention it, I do have it in my schematic files.

[Danny Troy]

Yes, in a pinch that would work, but it's still going through some circuitry. I was thinking accessing the power amp directly might give the cleanest signal. In case anyone else wants to see what the manual says concerning "stereo link", here it is:

You can make each unit's equalizer (LOW, MIDDLE and HIGH
knobs), SHAPE switch, VOLUME knob, and MAIN (R) and
SUB (L) settings independently.
Basically, they should be set to the same positions, but you can
adjust each one as necessary to suit the needs of a particular
setup.

UPDATE: I just did an A-B comparison using the channel input vs. the stereo link in. The stereo link in does sound better and I will make life simple and use it this way. Thanks for the suggestion Enzo....