Author Topic: Your favorite 12AU7?  (Read 1299 times)

Offline rpf

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Re: Your favorite 12AU7?
« Reply #15 on: April 23, 2021, 06:26:15 AM »
I'm late to the party but Ive tried a lot of 12AU7s in both two sections of my amp (Cronus Magnum: pre-amp and drivers) and in a few DACs.

I agree that the RCA or Raytheon black plates are superb and the best value out there. I never cared for the RCA clear-tops: too bright on top. The Sylvanias I tried were similar but with a bit more body. NOS Tung Sol were thick sounding as were Tungsram, with the latter being better balanced. NOS Mullards (12AU7 & CV4003) are very full bodied: they are the best tubes for the drivers of my amp but not the best anywhere else although they were good everywhere. I found Amperex one of the best all around: very smooth and refined.

The finest NOS 12AU7s I've heard - with one exception - are the Radiotechniques 6189 from 1956 or 1965: balanced, extended on both ends, full bodied but refined. The one exception was a very rare Mullard Paul Mah brought over to my house to try. It might have been a 10M but I think it might have been something even rarer. It was old and it was head and shoulders above everything else I've ever heard: it just had everything, with a tonal accuracy, spaciousness, and three dimensionality that was unbelievable. Unfortunately he was never able to secure another one from his English connection.

New production I've tried include Mullard, Tung Sol, EH, JJ, Shuguang (not Psvane). All sounded good initially, with the exception of the EH, but showed significant deficits upon extended listening. The re-issued Genalex were the best new production I've heard - pretty well balanced but not up to the better NOS in tonal accuracy or refinement.
« Last Edit: April 23, 2021, 10:47:00 AM by rpf »
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Offline Brap

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Re: Your favorite 12AU7?
« Reply #16 on: April 23, 2021, 06:33:26 AM »
Thanks rpf.  So I have put a good 100 hours on the Amperex and to me with my VTA ST-70, the 1960's clear top RCA's sound the best.  Again, I only got one as the center driver., sides are still RCA. The Amperex just was not as detailed , hard to explain but it felt like there were brackets ( ) around the imaging / soundstage where the RCA's expanded things.  Crazy hobby in search of nirvana.
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Offline rpf

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Re: Your favorite 12AU7?
« Reply #17 on: April 23, 2021, 06:46:20 AM »
The RCA clear top is known to be synergistic with the original and modified Dynas. I think it's the tube the original Dynas came with though I couldn't say for certain. Lucky you as they're still inexpensive!   :thumb:
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Offline spinblackcircle

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Re: Your favorite 12AU7?
« Reply #18 on: April 23, 2021, 09:01:33 AM »
Whats your favorite sounding 12AU7?

After spending more money than I ever care to admit on vintage 12au7 and 12ax7 tubes, in the end I found that my favorites were two new production tubes.

For anything sensitive to noise, the Gold Lions were a great compromise, they have more of what I consider a vintage sound and are super quiet.

For magical midrange and soundstage, TJ Full Music 12AU7.  I loved these tubes but they were too noisy to be used in a phono stage.  No issues in my Rogue 88 amp driver stage.

Best "All Around" tube for me was the Mullard CV4003 but they weren't so expensive when I bought them, I think I got a NOS matched pair for $100-120 and would no way pay today's prices for them, I'd circle back to the Gold Lions for $70.

Offline rollo

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Re: Your favorite 12AU7?
« Reply #19 on: April 23, 2021, 11:38:48 AM »
  Another concern with NOS is supply of such. When you find the tube of choice get several to keep that sound.

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Offline toobluvr

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Re: Your favorite 12AU7?
« Reply #20 on: April 23, 2021, 04:54:47 PM »
The RCA clear top is known to be synergistic with the original and modified Dynas. I think it's the tube the original Dynas came with though I couldn't say for certain. Lucky you as they're still inexpensive!   :thumb:


Interesting you say that, Rob.....

I don't know much about it, but I got impulsive and just bought a Dynaco ST-70 rebuilt by master Chris Keller in NC and he included RCA cleartops.  To say I'm impressed is an understatement.  He is known for his work on vintage tube gear -- Dyna, Fisher, Scott, Pilot, etc. -- and his restoration of this amp is impeccable.  It is like brand new, even the case.  His passion and expertise are obvious.   :thumb:

Very fair pricing considering how much they sell for used and beat up.

This is the one I bought:

https://www.usaudiomart.com/details/649729466-dynaco-st-70-totally-restored-and-upgraded/
« Last Edit: April 23, 2021, 04:57:24 PM by toobluvr »
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Offline Nick B

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Re: Your favorite 12AU7?
« Reply #21 on: April 23, 2021, 08:56:16 PM »
The RCA clear top is known to be synergistic with the original and modified Dynas. I think it's the tube the original Dynas came with though I couldn't say for certain. Lucky you as they're still inexpensive!   :thumb:


Interesting you say that, Rob.....

I don't know much about it, but I got impulsive and just bought a Dynaco ST-70 rebuilt by master Chris Keller in NC and he included RCA cleartops.  To say I'm impressed is an understatement.  He is known for his work on vintage tube gear -- Dyna, Fisher, Scott, Pilot, etc. -- and his restoration of this amp is impeccable.  It is like brand new, even the case.  His passion and expertise are obvious.   :thumb:

Very fair pricing considering how much they sell for used and beat up.

This is the one I bought:

https://www.usaudiomart.com/details/649729466-dynaco-st-70-totally-restored-and-upgraded/

That is beautiful workmanship! Quite nicer looking than most of the ST 70s Iíve seen. Have you had an ST 70 before?

Just found this....
http://glowinthedarkaudio.com/chris-keller-st70.html
« Last Edit: April 23, 2021, 09:02:34 PM by Nick B »
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Offline toobluvr

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Re: Your favorite 12AU7?
« Reply #22 on: April 24, 2021, 07:06:17 AM »
It's my first ST-70.

I've been emailing with Chris -- super nice helpful guy who goes above and beyond to make sure his customers are satisfied -- and I asked him about that amp, and how nice it was with RCA connectors in the rear.

His reply:

Uggh, that pic on Glowinthedark is terrible.  That guy sent it to me for some work and it was a mess.  Someone did all kinds of barn jobs on it - a half assed paint job, chopped up the chassis, the wiring was all messed up.  The power tranny was shot.  I wanted to redo the whole thing for him properly, but he just wanted a couple of things done and get it running.  If I'd have known he was going to post that pic and attribute it to me, I would have passed on that job!   Then the thing followed me.  A  guy in Texas bought it off his site and contacted me to see if he could send it to me for an overhaul. LOL  I ended up stripping it completely down and doing it properly, much like yours.  The Texan loved it.
As for the RCA's, they can have a tendency to pick up a little hum off the tranny's when located back there.  At least folks with high efficient speakers tell me that.  What I do have are right angle RCA adaptors that allow the cables to swing around the side.  See pic attached.  I should have put some in your box.  You want a pair?  I have plenty.


Really great to know a competent and reliable tube tech these days.  He tells me that Roy Mottram over at VTA / Tubes4Hifi is swamped with work and he asked Chris to help with some builds, and also help sorting out some technical issues that customers were having.  Even wants him to buy into the business -- apparently Roy wants to slow down.   He's got that kinda respect in the industry.
« Last Edit: April 24, 2021, 07:14:27 AM by toobluvr »
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Offline Nick B

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Re: Your favorite 12AU7?
« Reply #23 on: April 24, 2021, 02:07:00 PM »
It's my first ST-70.

I've been emailing with Chris -- super nice helpful guy who goes above and beyond to make sure his customers are satisfied -- and I asked him about that amp, and how nice it was with RCA connectors in the rear.

His reply:

Uggh, that pic on Glowinthedark is terrible.  That guy sent it to me for some work and it was a mess.  Someone did all kinds of barn jobs on it - a half assed paint job, chopped up the chassis, the wiring was all messed up.  The power tranny was shot.  I wanted to redo the whole thing for him properly, but he just wanted a couple of things done and get it running.  If I'd have known he was going to post that pic and attribute it to me, I would have passed on that job!   Then the thing followed me.  A  guy in Texas bought it off his site and contacted me to see if he could send it to me for an overhaul. LOL  I ended up stripping it completely down and doing it properly, much like yours.  The Texan loved it.
As for the RCA's, they can have a tendency to pick up a little hum off the tranny's when located back there.  At least folks with high efficient speakers tell me that.  What I do have are right angle RCA adaptors that allow the cables to swing around the side.  See pic attached.  I should have put some in your box.  You want a pair?  I have plenty.


Really great to know a competent and reliable tube tech these days.  He tells me that Roy Mottram over at VTA / Tubes4Hifi is swamped with work and he asked Chris to help with some builds, and also help sorting out some technical issues that customers were having.  Even wants him to buy into the business -- apparently Roy wants to slow down.   He's got that kinda respect in the industry.

Well, that explains some of those pics. Were it me, I wouldnít have posted them. In the Audio Mart ad, the quality really shows. As to those rcaís being in the back, it looks better that way, I donít think Iíve ever had efficient speakers anyway.

You will, of course, post your impressions, right!?
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Offline rpf

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Re: Your favorite 12AU7?
« Reply #24 on: April 24, 2021, 04:31:30 PM »
The RCA clear top is known to be synergistic with the original and modified Dynas. I think it's the tube the original Dynas came with though I couldn't say for certain. Lucky you as they're still inexpensive!   :thumb:


Interesting you say that, Rob.....

I don't know much about it, but I got impulsive and just bought a Dynaco ST-70 rebuilt by master Chris Keller in NC and he included RCA cleartops.  To say I'm impressed is an understatement.  He is known for his work on vintage tube gear -- Dyna, Fisher, Scott, Pilot, etc. -- and his restoration of this amp is impeccable.  It is like brand new, even the case.  His passion and expertise are obvious.   :thumb:

Very fair pricing considering how much they sell for used and beat up.

This is the one I bought:

https://www.usaudiomart.com/details/649729466-dynaco-st-70-totally-restored-and-upgraded/

Hey John,

Yes, that is a beautiful piece - and yes, the price is more than reasonable for that level of upgrade and finish.

Review please! How does it compare to the Dodd Mono 120s you had? They were the only EL34 based amps I've ever heard that were extended on both top and bottom (unfortunately I've never heard the big Manley or Cary EL34 mono-blocks).

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Offline toobluvr

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Re: Your favorite 12AU7?
« Reply #25 on: April 24, 2021, 05:19:16 PM »
Hi Rob......

Didn't buy the Dynaco for my Sunny H2W10 speakers, just not enough juice.  No way they will measure up to the Dodd grunt.
 
Looking back on it, never should have sold those Dodd monos.  With that 120wpc of el34 goodness, best my Sunnys ever sounded in my place.  Those amps were ballsy!  At 92db and a fairly flat curve the Sunnys are easy to drive, but for some reason they need some power to really gel and come alive.  At shows they were usually paired with very high quality SS beasts like Behold.  I did try powerful SS and class D on them, but just not for me.  I prefer tubes, and powerful tubes are pricey.

Been 12 years with the Sunnys....an eternity for me.  Great great speaker IMO, but not the best for low level listening --  they need to be goosed a bit to come alive.  Impressive once you play them like that.  But my life has changed -- no more house, I'm in an apartment now, gotta keep it down a bit.   Now I need a speaker that still performs at low SPL.  Also want high efficiency for the wide amp universe it provides, and all the great low power tube amps you can buy very reasonably for say 800 to 1400 used.

I don't know what came over me, but I went a little overboard in the past few weeks and bought two pair of speakers that fit the bill:  Klipsch Forte IV and Zu Dirty Weeekends Mk2.   That's the reason for the Dynaco purchase.   Years ago when still a somewhat young man    :rofl:      I owned Coincidents and Silverline speakers.  Remember fondly the great music I got from my low power tubes :   300B, 845,  el84, el34, etc.  So I'm looking forward to getting back on that track for some really sweet low level late night magic.

The Dynaco was an impulse I probably should have ignored.  I already have two very decent low-ish power amps I should have tried first, and then moved on if I needed to.  Oh well.......I hadn't bought any gear in a long time, blame it on pent- up demand.     :roll:

Should be fun.  In addition to the ST-70 I have a Baldwin Organ Super amp rebuilt by Will Vincent (6l6 power tubes, 20wpc) , and an SET amp built by a CJ tech in his basement (6as7 power tube, about 10 wpc)

Later.....
John

PS:  sorry for the thread hi-jack!
« Last Edit: April 24, 2021, 06:20:55 PM by toobluvr »
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Offline S Clark

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Re: Your favorite 12AU7?
« Reply #26 on: April 24, 2021, 08:28:06 PM »

 
Looking back on it, never should have sold those Dodd monos....
This isn't the first time I've read this comment about the Dodd 120's. 
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Offline rpf

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Re: Your favorite 12AU7?
« Reply #27 on: April 24, 2021, 10:13:51 PM »

 
Looking back on it, never should have sold those Dodd monos....
This isn't the first time I've read this comment about the Dodd 120's.

Yes, I should have bought them off John when he sold them.  :drool:  :duh  :rofl:

John, try to find some Reflecktor 6P3S-E for your 6L6 amp if it can take them (should be able to if it can handle 6L6GCs). The best of the 6L6/KT66 family I've heard (including RCA black plates & Sylvania 6L6GCs & Shuguang & Genalex re-issue KT66s). Fantastic tubes, they've been my favorite power tube for several years now.

Another apology for an off topic post.     But tubes!
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Offline P.I.

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Re: Your favorite 12AU7?
« Reply #28 on: April 24, 2021, 10:18:51 PM »

 
Looking back on it, never should have sold those Dodd monos....
This isn't the first time I've read this comment about the Dodd 120's.
Yep.  The Dodds were amazing amps.  Headroom for days...

I'm on my third and hopefully final rebuild of one of my ST 70 amps.  I'm using the VTA input boards and heavy duty power transformer.  Pretty much the only things original are the output transformers.  As usual I couldn't help myself and cryoed the output transformers.  There were interesting changes in electrical parameters when I did this.  I'll know soon about  about the audible results.

Depending upon how it turns out my plan is to do the same mods on the other one I have and then have vertical bi-wire pairs of amps.

I love me some tubes goodness!  :thumb:
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Offline Nick B

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Re: Your favorite 12AU7?
« Reply #29 on: April 24, 2021, 10:27:44 PM »
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