Carver hologram and Yamaha Amp "Buzz"

[jbeckva]

I mentioned this in another thread, but I think it warrants more info and investigation. I have a CT-6 preamp (actually two of 'em but both do the same thing). The carver sonic holography effect works great, except when I have the M-80 Yamaha hooked up. With that, I get a really loud "buzz" on the outputs.

What is also noteworthy - the "buzz" bleeds back into any other amp that I have being driven by splitting off the preamp outputs into two sets.

It's been suggested that it could be a power supply cap issue, but .. hmmm.. I have replaced all of the major caps in the power supply on the Yamaha (remember the two big 48K's I have strapped to the backside??.. I also recapped the remainder of them in a separate maintenance action).

Also.. without the sonic holography turned on, the M-80 is dead quiet. No noise at all. The inputs also go right into FET's ... so where might this odd feedback/buzz be originating? Why is it also bled back through the inputs to other amps I have powered up?

Good questions eh?

 

[laatsch55]

Very good questions, gonna have to be answered by a better hand than I.

 

[Pure_Brew]

My stab in the dark is that if the M80 is direct coupled, then it will be sensitive to any direct-current coming off the preamp outputs multiplying the effect when another circuit is engaged. That is if it's leaking.

Other amps that are not direct coupled, may be more immune to the effect. I wonder if you could hook up a scope to the output of the amp, or the output of the preamp upon engagement vs disengagement of the SH, and post a pic of the results?

Maybe just take a voltmeter and check for voltage differences?

I may be entirely wrong lol. I know my amp will multiply and direct current at the preamp level by a factor of 30! I don't know if that will only cause a speaker issue or maybe even something in the chain too.

 

[jbeckva]

Odd thing tho.. the NAD I'm using also is direct coupled. So it's like there's something in the hologram processing that is being reflected back from the pre to the Yamaha and back..

 

[Pure_Brew]

What model NAD?

 

[jbeckva]

2400PE. It has a LAB input that is DC'd instead of a cap coupling.

 

[Pure_Brew]

Um, if you disconnect the RCA input from the back of the M80, turn everything including the M80 without that connection, with the holo engaged, still quiet?

 

[Pure_Brew]

Or try not splitting the output and go just Yammy?

 

[jbeckva]

If I leave the Yammy off but still split with the NAD, no buzz on the holo. If I hook up the Yammy alone, buzz on the holo.

If I turn on the Yammy with it split and before the Yammy's protect goes off, I hear it out of the NAD. If I keep the holo off, even with both amps on, no probs. So it would seem that the holo just doesn't like the Yammy? Question is .. why's that?

 

[laatsch55]

What freq is the buzz??