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Anyone Tube Roll with the ZMA yet? (Read 356322 times)
Archie
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Re: Anyone Tube Roll with the ZMA yet?
Reply #750 - 12/13/21 at 17:35:16
 
I'd love to try some KT77s but my tube budget is currently limited to known tubes.

If you have a ZMA it does a pretty good job as a "tube tester."  I sparked one of my 7581As and it was on the side that was requiring a lot of bias offset to bring the pair together.  

The way you describe "dry bass" suggests to me that I don't have that problem, generally.  Although, that could be why I never really liked KT66s in my amp.  (I always attributed it to relative mid range lack.)
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__Jon__
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Re: Anyone Tube Roll with the ZMA yet?
Reply #751 - 12/22/21 at 06:17:41
 
I also found the new production kt66s somewhat recessed in the midrange, both in the ZMA and my lampizator DAC (which has a tube buffer). It was like female vocalists were a couple steps back from the band. Perhaps interestingly, I tried a pair of lightly used NOS GEC KT66s in the DAC and everything was noticeably better. Not the absolute best midrange but very good and it did so many other things remarkably well. Too expensive to consider in the ZMA though.

I’m also really happy with the 7027as but sometimes get an itch to change things. I plan to try the new production Gold Lion KT77s in the next couple months. Will post with thoughts if and when.
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Archie
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Re: Anyone Tube Roll with the ZMA yet?
Reply #752 - 12/22/21 at 06:28:00
 
I've liked pretty much every tube I've tried better than KT66s.  Never had anything other than new Tung-Sol and Gold Lion though.
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HockessinKid
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Re: Anyone Tube Roll with the ZMA yet?
Reply #753 - 02/18/22 at 13:05:45
 
Yikes, sporadic noisy right channel this week in my system. Started switching positions with KT77 power tubes in the ZMA thinking they were the culprit. Wrong!

This morning really high static sound coming from the right channel, ugh. Quickly powered down the whole system. After checking my tubes, I noticed a discoloration on the top getter in my right channel Sylvania OA3 voltage regulator tube. Went from steel gray to brown copper with some dark discoloration of the glass outside the getter.

I think I was moments away from a flash bang total tube failure. Thankfully I have several back up NOS pairs. Anyway, just a note for ZMA owners to keep an eye out on your voltage regulator tubes. I'm guessing these had 6,000 - 7,000 hours on them. Whew!

HK

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NormD
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Re: Anyone Tube Roll with the ZMA yet?
Reply #754 - 03/14/22 at 00:58:01
 
I was going through my tube collection looking to thin the herd. I came across a matched quad of RFT EL34’s. These are by far the the best tubes I’ve tried. Noticeably better in midrange clarity than the GL KT77’s. I have plenty of bass and treble with my Sopra 2 speakers. For some reason I had put them aside a few years ago - likely before the 25th anniversary mods and definitely before I went to 6N5P red tips for the input stage.
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HockessinKid
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Re: Anyone Tube Roll with the ZMA yet?
Reply #755 - 07/08/22 at 14:31:29
 
Well the quad of Gold Lion KT77 tubes only lasted 7 months, 😭. Two tubes started getting noisy then flashed up and died this morning.

I've put my quad of TAD 7027A tubes back in this morning. The cost of GL KT77's has doubled with the Russian shipping embargo, so I'll wait until prices become more reasonable before I spring for another set.

HK
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Carlsbad
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Re: Anyone Tube Roll with the ZMA yet?
Reply #756 - 07/19/22 at 05:29:56
 
Well I've, over several days, read this entire thread.  Very informative.  I wish it were as active as it once was.  

I have some Tung Sol 7581As on order.  I just removed my GL KT66s and am listening to Russian 6P3S quad.  Nice tubes, great sounstage, maybe a bit shy on bass.   Looking for some 7027As.  Unfortunately I bought my ZMA at just the wrong time tube wise.  Some amazing tube prices mentioned in this thread.  Some amazing in a different manner prices out there now.

On input and inverter tubes, it seems very hard to find any of the recommended tubes, Telefunken, Tungsram, Mullard and Ediswan.  There is a seller in the ukraine that has some tungsrams but his photos show them in the same packaging as several other bulk tubes he carries so I wonder if they are Chinese knockoffs.

Finally, it seems member stone_of_tone was posting enthusiasticly in early 2019 and then just quit posting.  His last post talked about tube rolling and working 31.5 hours over the next 3 days.  I hope he is ok.  I enjoyed his comments.

Jerry
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Carlsbad
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Re: Anyone Tube Roll with the ZMA yet?
Reply #757 - 08/01/22 at 23:25:01
 
Purple/blue voltage regulator tubes?  Steve has a beautiful photo of a VR90 style regulator tube that glows blue on the ZMA page.  Anybody know what specific tube it is?  

I know it is (at least must be) and argon tube since argon glows that color.  Neon glows orange which is what we see in the normal OA3's we use.

I've bought several older argon tubes.  None glow much at all and none sound as good as the standard OA3s.

I'd enjoy trying the tube pictured if anyone knows what it is.  

https://www.decwareproducts.com/zma
Scroll down about 8 pages.

thanks,
Jerry
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Lon
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Re: Anyone Tube Roll with the ZMA yet?
Reply #758 - 08/01/22 at 23:37:43
 
A VR90 is a 0B3 tube. I use that tube in place of 0A3 myself--in my system with my other tubes that sounds best. Most of mine glow a lavender/purple color--haven't seen one that glows blue.
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Carlsbad
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Re: Anyone Tube Roll with the ZMA yet?
Reply #759 - 08/02/22 at 01:23:43
 
Lon,
What manufacture tube are you using?  Do you have a source?  thanks, Jerry
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Lon
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Re: Anyone Tube Roll with the ZMA yet?
Reply #760 - 08/02/22 at 01:48:50
 
At the moment I am using Sylvania, "bottle-shape" type. I also use RCA and Westinghouse -- all three work really well with my Monoblocks. I get tubes from eBay.
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Carlsbad
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Re: Anyone Tube Roll with the ZMA yet?
Reply #761 - 08/02/22 at 12:31:31
 
Thanks Lon.
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__Jon__
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Re: Anyone Tube Roll with the ZMA yet?
Reply #762 - 08/02/22 at 18:56:33
 
And in case some don't remember, you can't change the OA3 tubes to OB3 or OC3 in the ZMA like you can in some of the other Decware offerings. I haven't personally seen any Argon OA3 tubes but I only have 50 or so  :P. When searching for these types of tubes remember to search with a "Zero" at the start as well as the letter "O." They are listed variably.
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HockessinKid
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Re: Anyone Tube Roll with the ZMA yet?
Reply #763 - 08/03/22 at 13:49:43
 
Just scored another quad, w/ less than 50 hours, of Gold Lion KT77's for a screaming deal. Should have them back in the ZMA shortly. Looking forward to getting that sound back.

HK

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Carlsbad
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Re: Anyone Tube Roll with the ZMA yet?
Reply #764 - 08/03/22 at 22:15:29
 
HK,
What are you biasing the KT77s at?  50mA is about 20W on a 25W rated tube which isn't terribly conservative but isn't aggressive either.  You should get pretty good life at 50mA.  Jerry
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Carlsbad
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Re: Anyone Tube Roll with the ZMA yet?
Reply #765 - 08/05/22 at 13:49:29
 
Jon
I want to politely challenge (because I don't really know) your statement that you can't use the VR90 in the ZMA.  On the ZMA page Steve has a photo of one and the following words:

"This beautiful tube is a variant of the OA3 regulator tube. It is a VR90 which drops the voltage to the input stage by around 15 volts.  This can be just enough to tickle your exotic N.O.S. 6922 or 7DJ8 inputs tubes into a new level of nirvana.  There are actually three of these tubes you can work with that will give you three different sounds."

So I think Steve is saying that raising the voltage from 75 to 90 is ok.  It doesn't change any of the gain settings.  But I would like to know for sure.

I have to admit that I interpreted this to mean that the VR90 was interchangeable with the OA3, i.e., they are both 90 v regulator tubes.  I ordered a couple and tried them.  Didn't like the sound as much.  I blamed it on poor quality used VR90s that I was able to find.  I just bought a few more old VR90s and I'll try them soon.  

But I haven't found anything that can sound as good as the true NOS sylvannia OA3s that the amp is supplied with.

Jerry
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Carlsbad
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Re: Anyone Tube Roll with the ZMA yet?
Reply #766 - 08/05/22 at 18:22:53
 
Update to above post.  Just today I received in the mail some true, sealed-in-the-box NOS sylvania VR-90s dated 1954 (2 years older than me).  I put them in and they sound great, not sure if better than the OA3s but I'll do some A/B testing on them later.  May take a while since my A/B tests are usually hours long, not minutes.

So I would really like confirmation that VR-90s are good.  Am I shortening the life of some of the tubes?  If so, which ones? I'm going to go try to figure out what components are using the regulated voltage.

But right now, things are sounding extremely nice.

Jerry
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GroovySauce
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Re: Anyone Tube Roll with the ZMA yet?
Reply #767 - 08/06/22 at 13:41:29
 
VR (Voltage Regulator) tubes drop voltage.

From Wikipedia.com:

Octal-based tubes, 5–40 mA current:
* 0A3 – 75 volts
* 0B3 – 90 volts
* 0C3 – 105 volts (best regulation of these four)
* 0D3 – 150 volts
Miniature tubes, 5–30 mA current:
* 0A2 – 150 volts
* 0B2 – 108 volts (best regulation of these three)
* 0C2 – 72 volts

So a 400v amp with a 0A3 is 325v to the tubes it's connected to. ZMA 0A3 powers the input tubes. I don't know if the 0A3 on the ZMA or Torii MKV power the inverter tubes or not.
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