System feedback coming thru speakers.....help

When some tube equipment powers up, it draws quite a lot of power. Is it possible w v. old electrical system, that this is causing power surges, which may be blowing fuses? I am assuming that the CJ tech gave you the proper fuse values...but you never know. Or maybe he just assumed you had the manual that gave you the proper values. I suppose its also possible that someone else put wrong fuse values in and that's why those fuses were blown in the first place...I'm assuming from your OP that you recently acquired the amp and had just put it into service when the problem developed.

Jdvorak, get another amp to try or take your amp in for repair.

By any chance have some or all of the fuses that have blown been Radio Shack "slow blow" fuses? I've seen a number of posts here in the past indicating that those fuses often tend to act more like "fast blows" than "slow blows."

Regards,
-- Al

I have replaced fuses.....it had happened once more but now seems to be fine. for now.

have you replaced your fuses to see if it happens again?

it does now. :)
really......should I just move back to a boom box? :)

How do you turn on your system? Amp turns on last...amp goes off first, right?

ok, one more question. I've blown a few fuses now ont he amp.....wondering if there is "dirty" power, and/or do I need a line conditioner/filter of some sort. anyone have any knowledge/experience in this area?

Fantastic!!! Very glad was able to help...he really is THE MAN! Enjoy!!!

PROBLEM SOLVED!!!!!!!
Well, I finally spoke with Ed at CJ earlier this week and we took off the cover of the amp together (as the fuses are internal on the Sonagraph SA400). Sure enough, 2 of the 4 fuses were blown. once replaced, all is well.

I want to personally thank each and every one of you for your input, advice and direction in helping me solve my issue. Your direction allowed me to go to Ed with pinpoint accuracy on where "we" collectively thought the issue might be.
There is nothing more satisfying now than sitting in front of my system and listening, feeling the stresses of the day wash away. I truly love being a lover of music, the arts.....as a product of them growing up, and even a music major in college (before switching to business and finding my career in healthcare sales/leadership), music has always been core and foundational in my life. It is good to be us!
Thank you again, fellow Audiogoners!

Sincerely,

Jason Dvorak

Tbg,

I hear you...i'm no techie, so just trying eliminate variable's the 'simple man's way'.

Lloydelee21, as improbable as it seems that an amp in both channels would do this with any input but not without, I think this is the only obvious test.

Have you swapped out the amp? is there a small one you an borrow?

Dhl93449, it is constant. no matter what the source. I wonder if it isn't actually the amp, as it happens with CD, nak, 2nd CD/DVD, no matter what.

I have a call into Ed at CJ too.

thx!

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).

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'.

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! :)

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

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.

Great idea, Almarg! I'm flying back home from biz tonight. I will try in am with dragon.
So, you believe it might be bad tubes?

Note for all: It's not just a "hum". It's a thumping coupled with a static-ie feedback.

Try different preamp, or try to see if you can plug the DVD source directly into your amp temporarily...some DVD players have a built-in internal volume control...usually terrible but it should work.

Or try the cassette deck straight into the amp. It has a level control on the front panel.

Regarding the references to feedback and hum, as I indicated earlier I don't think this is a feedback problem or a hum, ground loop, or grounding problem, based on the sonic descriptions that have been provided. My guess at this point is that it is simply a preamp problem.

Regards,
-- Al

And when you do plug in either of 2 sources...from either of 2 plug outlets...into any of your preamp inputs...there is hum which gets louder with volume. And the feedback hum is in both speakers...and also in a replacement set of speakers using the same 'problem setup'.

- not amp or speakers,
- probably not grounding which does not vary with volume
- Normally, 'feedback' occurs when you are outputting sound, and there is a microphone picking it up and feeding back into the same system. i assume there is no microphone input in your CJ preamp
- is it the interconnect?
- is it possible there is a problem with preamp...but you cannot tell if there is no source attached because (as you said, if u plug in source, turn volume down, feedback goes away).

Try different preamp, or try to see if you can plug the DVD source directly into your amp temporarily...some DVD players have a built-in internal volume control...usually terrible but it should work.

Lloydelee21, correct. nothing. no hum, no nothing.

HI Jdvorak,

i believe you said when you plugged in just the pre and the amp...with no source plugged or connnected...you could turn the preamp volume way up and there was no noise.

Is this correct?

wow, you ALL are amazing! thank you for your advice thus far.

UPDATE: Still not solved, but here is what I have done.
i found a grounded outlet in the house near a brand new washer/dryer my landlord recently had installed. pretty sure it's grounded, it has 3 prong.
I ran an extension cord from my strip to that outlet, still just using the amp, pre and 1 source.....still an issue. I changed source components, I also changed interconnects.....still an issue.
If I turn volume all the way off with the CD player playing, the noise goes away......but when I turn volume up, the noise/static/"pops" present. the louder I turn it, the louder the noises get.
My electrician is coming tonight, but I think less and less that it's the power source....although another grounded outlet is needed in this place! :)
could it be the tubes? i have no idea how good/old/hours there are on them. I do know that the !2AU7's are in correct place.....but not certain if they are all good or not.

Hi TPG,

To Jdvorak's credit, the process you descrive is exactly what he has done. He has so far determined there is complete silence with the volume on the preamp loud with teh amp on...providing there is no source connected.

So it appears to be the source of the interconnect. So he needs to connect a new source thru the same interconnect and see. If no noise, it is the source. If noise, it could be the interconnects.

Jdvorak? Any news?

A p.s. to my previous post. Looking at the information on your preamp at the CJ website, although I realize you said that the tube types at locations 4, 5, and 6 are correct, just to be sure I'll mention that if a 12AX7 or 5751 were placed at the V5 and/or V6 locations, instead of the 12AU7's that are supposed to be there, it might result in the symptoms you have described.

Also, it can be inferred from that information that V1, V2, V3, and V4 are all only relevant to the phono input, not to the line-level inputs (where the CD/DVD player should be connected, of course).

Regards,
-- Al

Lloydelee21, the standard procedure is to disconnect everything except the amp to the speaker wires. Turn on the amp. Do you have any noise? If you have noise with just the amp on, it is your wiring in the house. If not connect the preamp to the amp. Turn on the preamp and then the amp. Any noise? If so, it is your preamp or the interconnect wires. If not, connect one source and turn everything on. If there is noise, it is either that source or the interconnects to the preamp. If not, add the second source and turn everything on. If noise is present, it is that source or the interconnects to the preamp.

Actually, I think it is just a cold solder joint in which ever component you identify as the culprit above.

I've plugged the DVD into a different source on the pre amp......same results.

What you should try is a different source component, such as the cassette deck. Connecting the same source into a different input of the preamp doesn't prove very much.

I made mention Arlie's of it sounding "fine" at lower level......not the case......just at low volumes more difficult to hear the static/thumps.

That's different. Given that, I agree with Lloyd that the problem is upstream (ahead) of the volume control in the preamp. Meaning that it is being caused by either the CD/DVD player, the interconnect cable between it and the preamp, or by preamp circuitry (or tubes) that are "ahead" of the volume control.

I've included the preamp circuitry that is ahead of the volume control on that list of suspects, even though no symptoms appear when nothing is connected to the preamp inputs, because it is possible that a problem in that circuitry might not manifest itself under zero-signal conditions.

Regards,
-- Al

If the preamp can make the sound smaller or bigger...but the preamp and amp are silent with no source attached to it no matter how loud you turn the preamp...then it has to be source. And is probably not grounding. i did not think grounding would get louder and softer with volume.

Might be your source or your cable in between your source and preamp. Try a different cable. If same, then try another dvd player. Hope the electrician can help.

Ok, update: Yes, I am using a 3 to 2 "cheater" plug/reducer right now. My electrician friend is coming over tomorrow night to look into my electrical scenario. Not pleasant to say the least.
I did open up the pre amp. It looks like tubes 4,5 and 6 are all in correct spot, as I can clearly read the white lettering on the signifying the model. Tubes 1-3 unfortunately are illegible. I did, however, place them in the spots as was indicated on the tube boxes that came with the PV 11 when I purchased it. I have the entire system (just amp, pre and cd/DVD) out in middle of room. No crossed wires, no other issues. I've tried other cables, I've plugged the DVD into a different source on the pre amp......same results.
I made mention Arlie's of it sounding "fine" at lower level......not the case......just at low volumes more difficult to hear the static/thumps.

How close is your turntable to the components of your rig & what's the room config. Back in the 70's I had a smallish room & the turntable wasn't isolated enought from the amp/spkrs & perhaps vibration was the culprit & I experienced the same - at least that's what I surmised at the time it & more space & isolation of each piece solved the issue. happy listening!

A 3-prong to 2-prong adapter will probably still provide a ground, if its metal grounding tab or grounding wire is connected to the screw that holds the faceplate of the outlet in place, and provided that the wiring within the walls is enclosed in metal conduit. If you have a multimeter, or a neon-bulb AC tester, you can verify that by checking for the presence of 120 (or so) volts AC between the AC hot pin of the outlet and that ground screw.

From your description of the symptoms, I don't think that AC grounding or feedback have anything to do with the problem. And the fact that it works OK at very low volumes would seem to say that the problem is NOT upstream of the volume control (meaning that it is not being caused by the source component or its interconnect cables, or by preamp circuitry that is ahead of the volume control). Although it would probably be worthwhile to double-check that by trying a different source component, such as the cassette deck.

Some things to consider:

Are you certain that the new biwire cables are connected correctly, and that there are no shorts in the connections or in the cables themselves?

Are you sure that when you heard reasonable sound at low volume settings that you were getting normal stereo separation? It's conceivable to me that a short between channels could produce reasonable sound at low volumes, except that it would be mono, while causing the symptoms you described at higher volumes.

Along the lines of one of Lloyd's comments, but specifically with respect to the power amp, I would consider the possibility that the amp's input jacks may have been dislodged as you were connecting things, such that they lost their connection to the amp's circuit ground.

And, yes, it does seem conceivable to me that a defective tube, or the wrong tube type, or a tube placed in the wrong socket, could account for what you are describing.

Regards,
-- Al

All great advice, thx! yes, renting......just moved out of house that we built 6 years ago, so been a bit spoiled on actually 21st century technology, vs. NINETEENTH!!!! :) I have a call into my electrician today to get addressed, either way. Will do further isolation testing tonight as well to see if I can figure this out. so frustrating, but I think you are both on the right track for me. Thank you so much! Jason

+1 on getting your equipment into a grounded socket. I'd do that pronto.

If you are renting, I'd talk to your landlord. Having safe electricity is a pretty reasonable request. If you own, then I'd spring for an electrician to give you some grounded outlets.

To make sure i got it right...pre amp (on), amp (on), DVD (connected but off), turntable (disconnected and off)...no buzz no matter how loud you turn it up. That's GOOD. Once you put the DVD on, you get noise? If so, it seems to be either: a) the power strip, b) the connection between the DVD and the preamp (ie, the cable or the actual RCA in-jacks in your preamp...try different onces), or c) the actual DVD player itself. Try to avoid the 3-2 reducer on the end of the strip...it means you have no ground. that could be part of your problem?

If your amp and preamp run thru power strip just fine...plug DVD player separately into wall direct and see what happens.

I should have mentioned in my previous post- BE SURE to shut off your circuit before doing this or hire a qualified electrician if in doubt.

Sounds like you have a "cheater plug" between your power strip and outlet. I would get rid of that. You can have a standard grounded 3 prong outlet installed in place of that 2 prong. You would run a "ground leg" from the ground terminal of the new outlet to the steel electrical box via a grounding screw to the threaded hole in the back of that box. Since the cabling is probably BX, it would be self grounded to the main panel box.

All great points, Lloydelee21! I actually did some additional reading on here late last night and did some of your suggestions early this AM.
So, when having just the amp and pre hooked up and turned on (CD/DVD still connected but now turned on) there is no feedback, even turning volume up on pre.
everything else is disconnected from pre, as well as power. I also disconnected tv power, etc from system.
I DO have a power strip in place as the outlets are all two prong in this house. SO, I have to have a "3 to 2" reducer on the end of the power strip.
still getting same thing! ugh! if volume just barely turned on, music is fine. but as you turn it up to even 9 o'clock, the woofer starts to "pop" and there is static coming from mid and tweeter......both speakers!

I am not certain how old tubes were with pre amp, but I just put them in, and they (I believe) were well labeled for placement (I never put tubes into a pre before).

additional thoughts?

Hi Jason,

Wow...sorry to hear...and lots in your description to 'chase down'. Lets start with the basics...discconect the turntable. there is lots that can happen there we should isolate. Does the system still have weak signal and feedback without being hooked up to the turntable or the turntable even being plugged in? (ie, thru the DVD player)?

If you turn the DVD player off, and just have the preamp and amp on...do you stll get feedback/static? If yes, then it is somewhere in your preamp or amp. Turn your system off...turn back on just the amp. Still any static? If not, it could be the pre or the cable inbetween pre and amp. If yes, it could be the amp...or the wiring in your house.

If you can try to do a few of these 'easier' isolations tests...and post them back, maybe some of us can help.

good luck.