System feedback coming thru speakers.....help

This may not be a cure for you, but it was for me. With your amp/pre-amp properly grounded using the 3 prong plugs try adding the 'cheater plug' to the PC of the CD/DVD player. I have an oversensitive integrated that for reasons I haven't yet figured out the only way I can keep it quiet is by using the cheaters on the input source power cords. The only difference from your problem (only :-) is that the hum is constant.

Give it a try. Only takes a few seconds.

So, you believe it might be bad tubes?

Seems like a reasonable bet to me. If it is a bad tube, it would figure to be either V5 or V6 (both are 12AU7's), since the other tubes are not involved when line-level sources (CD/DVD or cassette) are being used.

Since V4 is also a 12AU7, but only supports phono playback, you might try swapping it with V5 and V6 (one at a time). If either of those substitutions fixes the problem when one of the line-level sources is being used, you've found the bad tube!

Regards,
-- Al

Ok, the plot thickens. When I just hooked up my nakamichi dragon directly to my SA 400 amp, it still does the same problem. Ugh!!! Tried different interconnects as well. It sounds like a bad (distant) radio station when I play a tape.....static, woofer noise, etc.
Could it be the amp?
I know it's NOT the speakers. I tried another set of speakers in this system earlier in the week and they did the same thing, but they work fine back in my mini system in the kitchen.

May e it's time I go back to a boom box! :)

Hi Jdvorak,

The "good news" is this is not a subtle problem that comes and goes...it is fairly black and white. Which hopefully means you've got a real problem that is identifiable by an audiotech.

Sounds like it is not your preamp.

1. Try calling Ed at CJ (Sonograph is CJ, no?) He is amazing, helpful and knowledgable.

2. What happens if you swap out the amp? Do you think you can try even tiny one you can borrow from local store?

3. Do you think it actually is radio? i have heard of some radio, rfi feedback sneaking thru somehow...RFI blocks and stuff should help but this seems like a huge 'sneaking'.

The sonic character of your noise sounds to me like "popcorn" noise. This is a bad semiconductor or tube, and if it happens with the Nak connected directly to the power amp, my vote is it's in the Nak. If it were in the power amp, you would hear it continually, irrespective of what is connected.

So to clarify, disconnect everything from the power amp, put a shorting plug (if you have one) across the power amp's RCA inputs, and listen. If its gone, reconnect the Nak and re-test. If its back, its the NAK. Do one more final test. Remove the Nak from the power amp and listen again with the input open. If it's back, then it could be a defective device in the input stages of the power amp. This is not likely because the Nak probably has a low enough source impedance (so it would be like the shorting plug).