Forums - Possible circuit path issue

DAKO

Verified Member

Posts: 23

Possible circuit path issue
03/08/20 at 04:16:45

Hello fellow audiophiles,
I may have a possible issue with my ZMA but wanted to get any smart forum members and possibly Steve's opinion before I make any drastic assumptions. My issue is with the B10 output tube/circuit. It appears that this tube does not glow as bright as the other 3 KT66's in the amp. I first suspected a failing tube, but I replaced it with a spare and the spare tube acts the same way. Another thing I have noticed is that I cannot seem to get the image centered. Right channel seems to be slightly out. This could be my room that is also causing the imaging issue. I have a very small room with some acoustic challenges. I am going to attempt to upload some pics I took so everyone can see the difference between the tubes.

I was going to send the amp in for the 25th anniversary upgrade later this year, but may have to accelerate that plan if this is truly a legitimate issue.

If anyone can advise on what this might be, I would appreciate it.

Thanks
Dave

Back to top

IMG_0324.JPG

Decware ZMA
Omega Super 8 XRS
Omega 8” sub in a CAM enclosure
Esoteric K-07
PI Audio UberBuss
Acoustic Zen Speaker cables
Decware IC's
ELF gold IC’s (current)
Decware Power cables
TimberNation Rack
Mapleshade Speaker platforms
Mapleshape isolation and H

IP Logged

Jeff of Arabica

Seasoned Member

Name the greatest of
all inventors...
Accident.

Posts: 968

Re: Possible circuit path issue
Reply #1 - 03/08/20 at 08:33:19

Dako,

On occasion tube can appear brighter than another even in a matched set. This can simply be a matter of one heater being more exposed than the other causing it to cast off more light. Tubes are not perfect devices and there will be variances, which is normal. Even if tubes test equal, the filament height differences can cause one tube to visibly glow brighter than the other, yet perform equally.

I would swap the left tube with the right tube and see if the brighter glowing tube still glows brighter, or not, when swapped. That should be step one.

How are the bias meters reading? Do you find the "dialing in" to be more difficult on the right side compared to the left?

Are they balancing ok?

Back to top

Canary Audio Grand Reference Monos//ZMA//Zen Ultra//Taboo MKIII//Waversa DAC3//ModWright Oppo UDP-205// PS Audio P20//Canary Audio MC-10//Van den Hul Colibri "Stradivarius"//FFYX T1803 TT//SonoruS Reel-to-Reel & tube playback preamp//Tannoy Westminster Speakers

IP Logged

DAKO

Verified Member

Posts: 23

Re: Possible circuit path issue
Reply #2 - 03/08/20 at 13:58:14

Jeff,
I have already swapped the tube with another known good tube but will move from left to right as well. I am not seeing any issues with basing and all meters are reporting fine and with no erratic activity.

I am also going swap the IC's at the amp and see if the imaging issue I am noticing moves from the right side to left. If I can move the trouble that should pretty well narrow it down.

Will report my findings once I try the steps above.

Thanks for your input.

Dave

Back to top

Decware ZMA
Omega Super 8 XRS
Omega 8” sub in a CAM enclosure
Esoteric K-07
PI Audio UberBuss
Acoustic Zen Speaker cables
Decware IC's
ELF gold IC’s (current)
Decware Power cables
TimberNation Rack
Mapleshade Speaker platforms
Mapleshape isolation and H

IP Logged

Archie Seasoned Member Posts: 2731	Re: Possible circuit path issue Reply #3 - 03/08/20 at 18:33:55 Have you tried swapping the other tubes while keeping the power tubes in their same place?
Back to top	ZLC Technics 1200G TT w/ Ortofon Jubilee MC cart ZMC1 ZP3 (25th A Mods) ZR2 (25th A Mods) CSP3 (25th A mods) ZMA (25th A mods) Homemade Big Betsy Speakers (F15s) Silver Cabling DIY Isolation platforms under amps & TT. IP Logged

DAKO

Verified Member

Posts: 23

Re: Possible circuit path issue
Reply #4 - 03/08/20 at 23:53:49

Hi Archie,
I have not swapped any other tubes at the moment other than moving the output tube from right side to left side. I have swapped the left and right channel ICs between left and right and swapped them back. The issue seems to remain with the tube I moved from right to left. I need more time to analyze. I will also swap the other tubes and see if one of them is causing an issue. I have a full set of used tubes here that are probably good enough for this test. It may be a few days until I report back.

Thanks for your suggestion.

Back to top

Decware ZMA
Omega Super 8 XRS
Omega 8” sub in a CAM enclosure
Esoteric K-07
PI Audio UberBuss
Acoustic Zen Speaker cables
Decware IC's
ELF gold IC’s (current)
Decware Power cables
TimberNation Rack
Mapleshade Speaker platforms
Mapleshape isolation and H

IP Logged

Archie

Seasoned Member

Posts: 2731

Re: Possible circuit path issue
Reply #5 - 03/09/20 at 01:22:55

Quote:

I first suspected a failing tube, but I replaced it with a spare and the spare tube acts the same way.

This confuses me a bit. Does this mean that whatever tube you put in this socket is dim? That's how I originally read it. (Or is the same tube dim in a different position?) That's why I suggested swapping around the other tubes. It might change the channel imbalance as well. I've had that too but I'm pretty sure it was a tube issue. I use my CSP3 to balance things in that case.

You can use your meters to check relative tube strength too. Steve explained the process somewhere but it involves swinging the bias to the extremes and seeing the range of each tube. I think a weak tube would have lower a min/max.

Back to top

ZLC
Technics 1200G TT w/ Ortofon Jubilee MC cart
ZMC1
ZP3 (25th A Mods)
ZR2 (25th A Mods)
CSP3 (25th A mods)
ZMA (25th A mods)
Homemade Big Betsy Speakers (F15s)
Silver Cabling
DIY Isolation platforms under amps & TT.

IP Logged

DAKO

Verified Member

Posts: 23

Re: Possible circuit path issue
Reply #6 - 03/09/20 at 02:46:35

Archie,
That was my original observation but I think now that is not the case. I just swapped out what I also suspected to be a possible weakening KT66 with a 2nd spare I had and it seems to be better. It will take some more listening/analyzing to come to final determination. But for right now, I am certain this is not an issue with the amp itself. Like I mentioned in my original post, I have a tough room and that could certainly contribute to the issue. It may also be some of the discs I am listening to.

As for right now, I will keep listening and evaluating and report any issues.

Thanks for everyone's input!!!!!

Dave

Back to top

Decware ZMA
Omega Super 8 XRS
Omega 8” sub in a CAM enclosure
Esoteric K-07
PI Audio UberBuss
Acoustic Zen Speaker cables
Decware IC's
ELF gold IC’s (current)
Decware Power cables
TimberNation Rack
Mapleshade Speaker platforms
Mapleshape isolation and H

IP Logged

DAKO

Verified Member

Posts: 23

Re: Possible circuit path issue
Reply #7 - 06/06/20 at 13:38:29

Hi All,
Quick update on this issue. Sorry for the long delay between posts. What I found out was, that when I removed the absorption panels flanking the left and right of my equipment stand on the front wall, the balance was perfect. Not sure why, but I do have a small almost square room which has been a challenge to say the least. After some analysis with a friend who has a great ear, the room is sounding fantastic. Well, as fantastic as an almost square room can.

Back to top

Decware ZMA
Omega Super 8 XRS
Omega 8” sub in a CAM enclosure
Esoteric K-07
PI Audio UberBuss
Acoustic Zen Speaker cables
Decware IC's
ELF gold IC’s (current)
Decware Power cables
TimberNation Rack
Mapleshade Speaker platforms
Mapleshape isolation and H

IP Logged