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EQUIPMENT FORUMS >> ZMA >> Static out of left speaker
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Message started by Jeff of Arabica on 08/03/17 at 07:23:26

Title: Static out of left speaker
Post by Jeff of Arabica on 08/03/17 at 07:23:26

So, as I was setting up the Tape Tour rig this evening to do some inaugural evening listening with the SVHS rig, my system developed a rather audible static/crackling noise out of the left speaker. When I looked at the bias gauges, I can see the needle of the left-most gauge twitch as the static noise presented itself.

The noise was heard while my system was powered up and idling with no music playing. It was intermittent. But when the static is sounding, the needle of the far left bias gauge twitches.

My first guess is a bad output tube. But then I wondered if a bad input tube could also be the culprit? Tomorrow I will do some tube switching to see if I can isolate it to the output or input but figured I would throw it out here in the event someone can advise.

Title: Re: Static out of left speaker
Post by stone_of_tone on 08/03/17 at 16:43:43

You're on it.

1) Output, input or inverter...doubt it's a regulator tube/they run so efficiently.

2) ....could be a resistor(s) issue....like I had?

Title: Re: Static out of left speaker
Post by stone_of_tone on 08/03/17 at 16:51:14

https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1486669840

My situation....and the Zen Master knocked it out of the park with perfection.....I swear it sounds even better now....seasoned/further in.

Title: Re: Static out of left speaker
Post by Lonely Raven on 08/03/17 at 17:01:21

Agreed - I'm not sure how much the Input or Phase Inverter would cause the meters to jump, so I'm leaning towards power tubes.

Title: Re: Static out of left speaker
Post by Archie on 08/03/17 at 17:04:40

Jeff,

I had noise problems with input tubes that I eventually replaced. I hope it's only that. I'm still interested if new meters can be DIY if it turns out to be that. If you talk to Steve can you ask him?

Title: Re: Static out of left speaker
Post by Jeff of Arabica on 08/03/17 at 17:38:02

I will ask about the meters if I get Steve involved, or if he happens to see this post. I had followed Stone's problem as it was happening and was thinking the same. If I could DIY the meter swap, I would purchase the new ones.

Just swapped the two left output tubes, had it on for 20 minutes. No noise and no meter movement. Although it took a couple hours last night before it randomly started so this afternoon, when I can listening and power it up longer, I will see if it reappears.

Title: Re: Static out of left speaker
Post by Jeff of Arabica on 08/04/17 at 02:59:06

I just completed a tube swapping regimen and the needle movement remained on the A14 (far left) bias gauge and the noise persisted on the left speaker.

First I swapped the two left KT66 tubes (A9 and A10). I then swapped the A12 and B12 input tubes, and lastly, the A11 and B11 inverter tubes.

Despite all of the tube swaps, the static/crackling noise remained on the left speaker and the needle twitching remained on bias gauge A14.

Stone, I am thinking you may be right on the faulty gauge resistor on gauge A14. Just sent an email to Steve for advice.

Thanks for the input guys. Ill keep you posted.

And Archie, I did ask about being able to DIY replace all the bias gauges without the requirement of soldering.

Title: Re: Static out of left speaker
Post by Archie on 08/04/17 at 16:03:43

Cool. I do have lights in my meters and it'd be nice to retain them even though one side hasn't really worked in a couple years! The lights could make it not quite DIY though. I'd lose the lights if it meant not sending the amp in for service.

Title: Re: Static out of left speaker
Post by Archie on 08/09/17 at 18:22:33

I just saw Steve's post that you are sending him your ZMA. Does that mean the meters are definitely NOT a DIY?

Title: Re: Static out of left speaker
Post by Jeff of Arabica on 08/10/17 at 01:41:54

Archie,
DIY not an option with bias gauge upgrade/replacement. Not sure why but my assumption is it has to do with calibration. I opened her up and seemed a bolt on replacement so there is obviously a step(s) involved beyond mere swapping that is not apparent to the naked eye.

Title: Re: Static out of left speaker
Post by Archie on 08/10/17 at 16:28:24

I was hoping that the gauges were bench calibrated. Steve told me that the screws on the front were for zeroing the needle -- which I've done. I guess I'll cross that bridge IF I come to it. I don't relish the idea of paying shipping for this beast both ways. At least I've got the Pelican case if it came to that.

Title: Re: Static out of left speaker
Post by Jeff of Arabica on 08/10/17 at 16:51:16

Yeah, not sure why exactly, but if truly interested I would send an email to Steve directly to better understand why he recommends it come back. I didn't mind as much as I am having him do a few other minor upgrades for me. That said, it was $50 one way to ship and $100 with insurance (from SoCal).

Oh, and Pelican case a HUGE plus when having to ship this beast!! Makes it 10X easier/safer.

Title: Re: Static out of left speaker
Post by Archie on 08/10/17 at 23:53:36

$100 one way is a lot less than what Steve charged when I bought mine and I'm in CO (currently shows $146). What else is he doing? I asked him about balanced inputs once and he said a ZBIT was a better option.

Title: Re: Static out of left speaker
Post by Jeff of Arabica on 08/11/17 at 02:25:22

Archie,
I use my corporate account for shipping so I do get a pretty good rate with all the carriers.

I ordered a ZBIT and it is now being tested so should ship soon. I am going to add it to my PS Audio DirectStream DAC. I thought about the balanced inputs too, but I have several sources, so need my Zen Switch Box which is of course RCA only.

My ZMA is being upgraded to a stepped attenuator (better contact than standard potentiometer), silver RCA's, and silver speaker binding posts.

Title: Re: Static out of left speaker
Post by Acetone on 08/11/17 at 16:31:53

JoA, Hope ZMA work is a quick turn around for you. If I ever have to send in my Zen amp I plan to upgrade to UFO trans & Stepped attu. But do not want to part with the amp if not absolutely necessary!

Title: Re: Static out of left speaker
Post by vyokyong on 09/11/17 at 03:10:22

Hi Jeff,

Yes, my ZMA has some left speakers problem as your description. "The noise was heard while my system was powered up and idling with no music playing. It was intermittent. But when the static is sounding, the needle of the far left bias gauge twitches." The loudness of left speaker is little less than right speakers. It is more obvious when there is only vocal sound in music.
However it became worst when there is no sound on left speakers any more. But when I turn off ZMA, there will be sound come out of left speakers for 30-60 seconds and phrase out. I record video and sent to Steve. He said that he cannot think of any causes to be happened like that. He send me circuit scheme in order to send ZMA to be repaired at local audio tube amp shop here in Vietnam. It happened in Dec 2016 but I have not repaired ZMA yet and have not played ZMA since then.

However I just read Jeff case and Stone of tone case in forum. Then I suspect my ZMA case may be meters as below case.

Hi Larry,

Amp tested perfectly fine, however the meters did not. Two of the meters had lost their calibration causing them to read faulty. Starting in Jan 1st 2017 all the meters in Decware amplifiers are being disassembled and fully rebuilt by Decware before being installed into the amps. Part of the rebuild process includes tighter calibration and an upgraded resistor which can handle many times the current over a stock one. This results in better sound, which is why we have incorporated it into all new Decware amplifiers that use meters.

I sent e-mail to Steve for my case as above. He recommends to send all 4 meters of my ZMA to him to check. If there is problem as above, he will rebuild and re-calibration all 4 meters and send them back to me.

Thanks for Jeff to write e-mail to me asking me of my ZMA so that reminding me to read the forum and found out some problem case which may solve my ZMA case also.

I will report back when there is any progress of my ZMA case.