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From 5963, 12AT7, 7062, 12AU7, 6414 & counting (Read 1771 times)
Fireblade
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From 5963, 12AT7, 7062, 12AU7, 6414 & counting
02/15/14 at 21:03:24
 
I received my two driver pairs and tested the RCA Black Plate 12AT7 first. Initially, bass was all over the place, with only 2 hours burn-in, but then it started to gradually become cohesive and synergistic.

The following observations stem from their coupling with RCA 6V6 G ST's (big boys). Consider these preliminary due to insufficient burn-in:

Now bass is more evident and powerful, deeper and tighter. The tube is quite balanced (neutral) and never creates glaring or harshness or sibilance (as the Brimar 12AT7's do sometimes with the big boys).

I also find them smooth, not a hint of edging in extreme frequencies, but not rolled off either, just smooth as silk. A driver that controls the music flow just about right, no excesses, no dullness. No wonder Steve voiced the amp with this driver's specs.

The G ST's do not sound as big/wide with the 12AU7's as they do with SQ 7062's, but this is related to the decreased gain. In no way are the RCA drivers laid back or dull sounding (as my stock 5963's), but they just do not push those big boys so hard. In this respect, I still prefer the SQ 7062's due to its dynamics but it is still to early to tell.

I need to burn them further and then do the same with the GE 6414's, another promising driver alternative. Then, I'll roll each and every one of my output tubes with both new drivers and sort of rank the hot combinations.

Just plain fun!
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« Last Edit: 02/15/14 at 21:18:09 by Fireblade »  

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P K
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Re: From 5963, 12AT7, 7062, 12AU7, 6414 & counting
Reply #1 - 02/18/14 at 15:38:52
 
If the MT was voiced or designed around a 12au7 then why should a much higher output 12at7 work better?

Maybe it is like adding Zstage in front of the MT?

I know the 7062's output is between the 12au7 and 12at7, may be a better match with less gain?

I have tried an orange label made in the USA NOS Amperex 7062 (date code 84-38) with good results. Do you know of other 7062's with better sound (may be a Phillips SQ)?

I have a high end turntable and cart. as well as a high end DAC and transport.

I find I need a different 12au7 tube for each application to achieve the magic sound that make tubes special.

For a Grado Reference1 low output cart. I use a NOS long black plate RCA 12au7.

However I will be trying out a Soundsmith Zephyr cart. in the near future (may be the Soundsmith phono cart. will work better with different tubes than the Grado).

PS Audio DAC and Transport I use a Mullard halo getter NOS 12au7 tube (with the max. neg feedback on the MT (to tame a harsh high end).

I am searching for a one tube solution, I might try a Cifte 12AU7 (1962 Vintage). I have already tried a Siemens with interesting results.

Has anyone tried a Cifte 12au7 (1962)?

I will be interested to hear your final results for a RCA Black Plate 12AT7 as my favorite tubes for playing LP's is the RCA Black Plate 12AU7.
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« Last Edit: 02/22/14 at 23:00:41 by P K »  
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Fireblade
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Re: From 5963, 12AT7, 7062, 12AU7, 6414 & counting
Reply #2 - 02/19/14 at 01:08:40
 
My apologies, your message made me realize I had a typo there: It is a pair of RCA 12AU7 Black Plates I'm burning in now, with good results.

Of course, the Phillips SQ 7062 does wonders when coupled with the right output tube, in my case the G ST's.

If the amp sounds too warm and dark given the tube complement and your specific speakers, for example, a good 12AT7 can open up the sound and bring up more transparency, air and neutrality. It has to be the right 12AT7, of course.

I experienced the described effect even using the OA3's (their contribution tends to exacerbate the Reflektor's excessive warmth) along with Russian Reflektor 6V6's in the setup. The latter are quite tough to open up, but when they do, the warmth is just ideal, IMHO. The Brimar 12AT7 pushed the Russian tubes to their best. Unfortunately all other 6V6's in my humble stable do not withstand the Brimars that nicely, with some sibilance or high frequency ringing.

The described setup stood invincible in my system until I tried the 7062's and G ST's together ... Synergy!

I haven't had the time to burn the 12AU7's much more yet and I still need to cook the GE 6414's ... I'll report on both drivers' subjective findings in time.

BTW, congrats on the amazing range of tubes you have had in your tube-rolling experiment. We'll keep an eye for further updates.


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« Last Edit: 02/19/14 at 01:12:44 by Fireblade »  

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P K
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Re: From 5963, 12AT7, 7062, 12AU7, 6414 & counting
Reply #3 - 02/19/14 at 15:17:28
 
I really like the RCA Black Plates 12au7 tubes in the Mini Torii.

Please let me know how they contrast and compare against the Phillips SQ 7062 tubes.

Thanks,

P K
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Fireblade
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A.L.Tennyson

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Re: From 5963, 12AT7, 7062, 12AU7, 6414 & counting
Reply #4 - 02/19/14 at 22:15:12
 
No problem. I just need more time to make sure I'm giving them enough burn-in time.

BTW, the SQ 7062's are impressive in my system but only with the G ST's. Otherwise, they sound good but nothing special. I have hopes for either the RCA or GE drivers to become special with most of my 6V6's, but we'll see.

I'm guessing I will end up with different synergistic couples among 6V6's and drivers. For example, Brimar 12AT7 + Reflektor 6V6; SQ 7062 + G ST; hopefully RCA 12AU7 + Tung-Sol 6V6, and so on.
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« Last Edit: 02/19/14 at 22:15:37 by Fireblade »  

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P K
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Re: From 5963, 12AT7, 7062, 12AU7, 6414 & counting
Reply #5 - 02/19/14 at 22:51:45
 
I have read on various posts and forums that the Valve Art 350b tubes sound similar to the RCA 6v6g st, thus my interest in the Phillips SQ 7062 tube.

My 1984 vintage Amperex 7062 tubes sound good, but not special with the 350b tubes.

Any guidance would be appreciated.

P K
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Fireblade
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A.L.Tennyson

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Re: From 5963, 12AT7, 7062, 12AU7, 6414 & counting
Reply #6 - 02/20/14 at 17:37:22
 
The Phillips SQ 7062 (SQ stands for Special Quality) that I have come from Brent Jessee.

If the G ST and the 350 B provide similar sound quality, then I would stick to the G ST as it is less demanding on the amp in the long run (350 B is almost a 6L6, with higher current requirements than the 6V6).

$0.02
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P K
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Re: From 5963, 12AT7, 7062, 12AU7, 6414 & counting
Reply #7 - 02/22/14 at 15:53:08
 
One last 12au7 observation.

I have switch from a Grado low output Reference1 (a terrific cartridge for $1,500.00) to a SoundSmith VPI Zephyr ($999 and made for the VPI Unipivot arm, I am using a Hadcock 242 Unipivot).

The Zephyr tracks just a little bit better than the Grado, but is brighter (sometimes good, other times not).

The interesting thing is the Grado likes NOS RCA 12au7 Blackplate tubes, the SoundSmith Zephyr likes Mullard Blackburn 12au7 tubes. These are the authentic Mullard Blackburn plant tubes made in 60's with "Gf2/B3J5" and "Gf2/B8E5"etched codes.

This is a good thing for my system as my PS Audio DAC and Transport also sounds best with the Mullard Blackburn 12au7 tubes (no more swapping of the 12au7 for playing LPs).
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Fireblade
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A.L.Tennyson

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Re: From 5963, 12AT7, 7062, 12AU7, 6414 & counting
Reply #8 - 02/23/14 at 00:26:29
 
Interesting. I guess those Mullards sound just great!

I've completed (just about) the burn-in of my new RCA 12AU7 Black Plates, and after careful listening I have several observations for anyone who may care to try these:

1. Best low-mids and base of all the drivers I've tried so far.
2. Excellent midrange. Smooth, natural, thick, neutral.
3. Slightly recessed in the high frequencies. Is like applying a treble cut-off. This minor roll-off helps in high pitch passages but I feel in general it misses some important information (textures, limits) in just that top frequency band.

All in all I prefer the SQ 7062's for the mid and high frequencies and the RCA for the mid and low frequencies.

The middle bands are different with each type, but both offer satisfaction. The RCA is smoother and rich with body, the 7062's are more open, airy, fast and detail-retrieving, but less smooth.

Depending on the recording characteristics, one would be better than the other. Both are very good options.

These observations are only using the Big Boys (G ST). YMMV

Next, I'll burn the new GE 6414's and see what these offer.
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« Last Edit: 02/23/14 at 14:22:27 by Fireblade »  

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Fireblade
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A.L.Tennyson

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Re: From 5963, 12AT7, 7062, 12AU7, 6414 & counting
Reply #9 - 03/01/14 at 17:42:20
 
This is my back-of-the-envelop approach to driver tube-rolling in the Mini-Torii, based on my limited rolling experience.

Of course, it only reflects my specific listening conditions and my subjective appraisal, as well as my own conception of the 'big picture' involved in this topic:

https://www.flickr.com/photos/119088875@N07/12859245294/


I expect the area inside the red frame to be the most rewarding (to my tastes), and so the possible number of available tube alternatives can be narrowed down when one knows what to look for while keeping the rest of the tube complement fixed.

I haven't finished evaluating the GE 6414 yet, but I'm getting close. So far, it is brighter and edgier than the RCA 12AU7 BP it replaced recently, but part of that may be insufficient 'cooking'.

Update: Today the GE 6414's seemed ready to be pushed, and so I tested them carefully ... No more brightness, still a little edgy in the highs.

It comes second to both the Phillips SQ 7062 and the RCA 12AU7 BP, depending on the recording. Not a bad tube at all though. It is open and pretty neutral, but lags behind the 7062 in texture and the 12AU7 in smoothness and warmth. Highs do not extend as much as with the 7062 but goes higher than the 12AU7.

All in all, a good general purpose driver alternative in the Mini with the described setup.
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« Last Edit: 03/01/14 at 22:46:38 by Fireblade »  

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P K
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Re: From 5963, 12AT7, 7062, 12AU7, 6414 & counting
Reply #10 - 03/02/14 at 15:58:22
 
I really like your chart, can you identify the other 6v6 tubes shown as blue lines.  For example which one was the warmest?

Thanks,

P K
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Fireblade
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Knowledge comes, but
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A.L.Tennyson

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Re: From 5963, 12AT7, 7062, 12AU7, 6414 & counting
Reply #11 - 03/02/14 at 21:11:42
 
Thanks, P K.

The warmest 6V6 I know is the Russian Reflektor Plant 6V6, Black Glass. In fact, it needs a commanding driver with relatively high gain to achieve the best it can be, and become the warmest sounding yet still detail retrieving tube it is known for.

In my case, I pair it with Brimar 12AT7, an otherwise edgy and powerful sounding driver that needs a hard/dark output tube to excel. Other 6V6's tend to overdo the highs and to 'ring' when paired with these, especially in high-pitched passages. Only exception being the Big Boys, which can take almost anything and keep their composure.

As far as the Gain-based model chart, it is a rough simplification of what I expect the big picture to be. I don't have the required data (i.e., grading of each 6V6 vs driver combination as per perceived tone), but with the limited sampling I've experienced, I'm definitely guessing this is the general way it can be conceived.

Of course, the curves are most probably exponential (convex in this case) and not linear, but without data the straight line will suffice for a ball park assessment, which is the general object here. For example, I've noticed high sensitivity to gain changes in lower gain tubes and more robust behavior on high gain drivers facing gain changes (typical exponential behavior).

The family of 6V6's depicted in the chart are assumptions stemming from the expected differences in design and components' quality across 6V6's, not real curves. The only true one (as per my results so far) is with the Big Boys.

What's important though, is that I expect the general relationship to remain the same across all 6V6's as the way my setup would react as a function of Gain and Perceived Tone (i.e., some 6V6's would be relatively more robust in their response, while others would react faster to those changes), but the general slope of the curve would stay the same.

For example, I just finished evaluating the GE 6414 and though it belongs to the red framed group in the chart, given its lower relative gain (42 Mu) vis vis the SQ 7062 (48 Mu) it is not such a surprise I tend to like the latter more.

This is still a rough draft, but I think I'm heading in the right direction, just need to get more samples. This rough model will never be statistically significant as per the myriad of designs and quality components possible out there. This is no problem, as we do not intend other than to narrow the alternatives and increase the probabilities of nailing it sooner than later in a trial-and-error sequence.

Of course, there are differences in drivers too, I suppose, not only gain-derived, but so far the 12AY7 family seems to be predictably at the eye of the hurricane in my setup.

As a reminder, technically this only applies with the set of tubes described, in my Mini Torii, under my listening conditions. Yet, I suspect the model is way more robust than that, though.
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« Last Edit: 03/02/14 at 21:56:05 by Fireblade »  

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