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Anyone Tube Roll with the ZMA yet? (Read 72695 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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Carlsbad
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Re: Anyone Tube Roll with the ZMA yet?
Reply #768 - 10/07/22 at 13:24:53
 
After listening to the VR90s for a while and going back and forth, I decided I like the OA3s that Steve recommends the best.  Been back in the amp for quite a while now.  

So after lots of tube rolling I've decided I like the TS 7581A best in the power position.   On the input tube I'm using the red tipped 6N5P NOS Russian tubes and for the driver I'm using my favorite old WE 396A with an adapter.  

Jerry
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Carlsbad
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Re: Anyone Tube Roll with the ZMA yet?
Reply #769 - 10/12/22 at 04:39:02
 
Another update.  Got another pair of WE 396 and have them in both driver and input locations.  superb.
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Carlsbad
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Re: Anyone Tube Roll with the ZMA yet?
Reply #770 - 11/01/22 at 03:22:14
 
Anybody tried 350Bs with the ZMA?  What are your results?

thanks,
Jerry
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GroovySauce
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Re: Anyone Tube Roll with the ZMA yet?
Reply #771 - 11/01/22 at 15:06:53
 
350b are no longer made AFAIK. The ones I've seen for sale have been $600+ per tube. TubeDepot.com is selling Wester Electric 350b for $1,150 each, almost $4,400 for a quad!

I have not tried them and don't have any plans too.

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Carlsbad
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Re: Anyone Tube Roll with the ZMA yet?
Reply #772 - 11/01/22 at 19:05:49
 
Groovysauce,  I see from the tubes included with your Torii for sale that you aren't afraid to roll some tubes.  

I too think the WE 350Bs are too expensive.  However, Valve Art made some modern copies.  The more I read about them, the more I see people warning off of them.  However, often such internet wisdom comes from people with original 350Bs for sale. They won't sell if the Valve Art tubes get good reviews.  

Also expensive is the RCA 6L6GC but the GE version is affordable.  

I've been using new tubes.  I have upgraded all my digital system.  The amp is sounding wonderful and I think it is now time to explore NOS.  I'm using WE396 input and driver tubes--have experience with this tube in other amps--and am very happy.  

Welcome any advice you have.
Jerry
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Carlsbad
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Re: Anyone Tube Roll with the ZMA yet?
Reply #773 - 11/03/22 at 13:43:50
 
Update on tubes.  I have made a lot of upgrades to my system since I did most of my tube testing.  my entire digital front end has been upgraded, my amp has seen a few upgrades including some new wiring inside and eliminating the fuse (power strainer) in the input.  Not sure I had my PS Audio PP10 at the time I tested tubes.  Here is the list:

TS 7581A--the tubes I've been listening to for months, love them.
TS 7027A--oops, bad tube now fills one channel with static not tested.
Mullard el34   Bland
Golden lion KT66  Good but missing dynamic midrange and highs
TS KT66--the tubes supplied with the amp, the ones i had when i started buying tubes.  i remember them as good.  with the upgrades they are amaing.  the music keeps jumping out at me.  vocals and saxophone are right in the room with me.  Highs are strong.  bass perfect. I guess it makes sense since the amp was built around these tubes.  I wish they made a little more light.  the 7581A tubes look awesome in low light while listening.  Amp light is balanced between the input tubes, power tubes, and regulators.

Ooops, just realized I forgot to test the russian tubes again (whatever the 6l6 equivalent is which I have a set of.

Tubes on my list to try:

GE 6l6GC
807, preferably mullard but a nice set
sylvania 5933

Jerry
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Carlsbad
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Re: Anyone Tube Roll with the ZMA yet?
Reply #774 - 11/23/22 at 12:58:10
 
Any body tried 350B?  Tube looks very compatible except the heater current is higher at 1.6A. Anybody know if the ZMA heater circuit will supply the higher current?  

http://www.tubezone.net/pdf/we350b.pdf

Tube looks like it would be fun to try if the heater current works.

Jerry
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Carlsbad
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Re: Anyone Tube Roll with the ZMA yet?
Reply #775 - 01/07/23 at 17:25:35
 
Ok.  This thread has become Carlsbad's tube log but that's ok. I hope my comments will help someone some day.  

Jan 2023 update.

I tried the russian 6P3S and they have become my favorite tube.  Excellent clarity with no harshness.  Great bass.  tremendous image.  

I went back to the original KT66 which came with the amp and they are a close second and might be preferred by some.  It is no surprise that the tube that Steve designed the amp around is excellent.  I tried Gold Lion KT66s for quite a while, thinking they were an obvious upgrade and it wan't until I put the originals back in that I realized they are not.

I tried the 6P3S-a, an upgraded tube for longevity and found it slightly lower in fidelity, probably a tradeoff so I recommend not bothering. The tube isn't bad, but isn't quite as good.

I tried the 807s and sylvania 5933s.  Found both to be interesting. looked great, but not as good a sound.  I listened to both for several days.  So they weren't horrible.

I figured out the 350B wouldn't work.

I'm currently using russian SG2S in the rectifier and I think they are slightly superior to the sylvania NOS OA3s but not a lot. I think any tube in the power supply is important and I'm going to watch for other options here.

In the input and driver positions I have WE 396 which is an old favorite of mine.  The russian red tipped 6P23P is very close.  

Finally, as I've been tube rolling I've been upgrading my digital front end (I listen almost exclusively digital).  It would have made tube rolling much easier and less expensive if I'd done that first.  A few tips:  never stream wirelessly.  Get a good streamer. other options drop more bits.  Use silver plated conductors for all digital cables.  Buy the best DAC you can afford.  FPGA is a good thing.

Jerry

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Re: Anyone Tube Roll with the ZMA yet?
Reply #776 - 09/01/23 at 11:34:45
 
Installed a new quad of Tube Audio Doctor (TAD) 7027A's in the ZMA this morning. The Gold Lion KT77's simply don't have much staying power in my amp, even though they sound exquisite.

I like the tonality of the TAD's over the new production Tung-Sol 7027A's. A bit more recessed and 3 dimensional IMHO. Nice tight bass response with my Caintuck Audio Magnum F-15's too.

Matched quads are available from Stew-Mac for $220. A bargain these days. I got over two years of listening out of the last TAD quad.

HK
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Re: Anyone Tube Roll with the ZMA yet?
Reply #777 - 09/08/23 at 15:11:09
 
Man I love it when new tubes hit the magic zone. ~50 hours later that little switch came on.😊

HK
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Re: Anyone Tube Roll with the ZMA yet?
Reply #778 - 01/26/24 at 19:49:11
 
I have read through quite a bit of this thread but decided it's probably faster to just ask:

I just picked up a quad of KR Audio KT88s. They sound VERY nice. Surprisingly, I am able to bias them at Steve's recommended 50 mA. I am not unhappy with how they sound at this bias. However, I've read here that 64 mA is "correct" for KT88s in the ZMA. Is there any risk or benefit to running them at 50 mA instead? It seems like doing so will help preserve the life of the tubes and other components.
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Carlsbad
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Re: Anyone Tube Roll with the ZMA yet?
Reply #779 - 01/26/24 at 19:54:54
 
I ran my ZMA (I no longer have it) with most tubes biased toward the low side.  Some like to bias right at the top of the range but never found it to provide sonic benefits.  two significant benefits:

1.  No redplating.  Tube are happy and not on the edge at a lower bias current so you have a much lower probablility of redplating.
2.  Your power transformers will run cooler.  The power transformers on the ZMA run warm.  I instrumented mine and they never got close to operating limits but I did enjoy keeping them a bit cooler.  I tend to leave my amp on all day so the warm transformers and warm tubes tend to warm up the entire amp.

Finally, I never found the KT88s to be one of my favorite tubes with the ZMA.

Jerry
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Re: Anyone Tube Roll with the ZMA yet?
Reply #780 - 01/26/24 at 20:35:15
 
Cool. Thanks for the info!
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