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Tube Rolling Results for Current MT (Read 3353 times)
P K
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Tube Rolling Results for Current MT
12/15/13 at 22:07:41
 
MY FAVORITES BELOW,

Any Comments?

Amperex NOS 7062 Made in USA (RCA NOS 12au7 from Decware, that came with amp and Siemens 12au7 from Upscale Audio, both a close second).

EZ 80 (NOS Tungsram), per other posts, to go with the Amperex NOS 7062 (a NOS EZ 81 Mullard a tie or a close second (stock JJ EZ 81 do not last very long)

New Tung-Sol 6V6GT from Decware, came with amp OR for a warmer, full bodied sound, along with a more relaxed upper-end sound (but with less detail), a New- Tube Amp Doctor 6V6GT-STR from Cyroset.

The TAD 6V6GT-STR is preferred for long listening sessions as it is less fatiguing.
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« Last Edit: 12/16/13 at 15:30:52 by P K »  
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grinnell
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Re: Tube Rolling Results for Current MT
Reply #1 - 12/16/13 at 20:22:49
 
I have had some great results from some 40's RCA 6v6g st.  got some bass punch and nice extended range.  I agree about the Amperex 7062 good tubes.

I tried some Art Valve 350's, very nice sound sweet airy but light on the bass.

got some OC3's b/c i liked the blue glow  not much tone change from the stock OA3's
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P K
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Re: Tube Rolling Results for Current MT
Reply #2 - 12/17/13 at 03:34:21
 
The Valve Art 350B may be the next tube I try.

I notice that Tung Sol has a 6L6-G or the 6L6-GC-STR reissue.

I wonder how they compare to the 350B?

Also I have seen a lot of new production 6L6 tubes from various russian and chinese tube companies, do any stand out?
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Fireblade
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Re: Tube Rolling Results for Current MT
Reply #3 - 12/17/13 at 17:12:21
 
I've been very happy with my preferred driver tube these days, Philips SQ 7062. These have the ideal combination of openness, warmth and intermediate gain which do not  drive fast and sensitive output tubes (like the current production Tung-Sols), into sibilance on very high frequency passages. As opposed to 12AT7's, these drivers need an open, big sounding output tube to sound their best though.

So far my first choice combo for the M-T is the Phillips SQ 7062 paired with the excellent RCA 6V6 G ST (1940's production, big, coke shape).

The next preferred pairing is Brimar 12AT7 along with said G ST's.

On third place, the Brimars with the Russian Reflektor Plant black glass 6V6's. The usually dark but sweet sounding Russians need to be opened by a powerful, commanding driver, and the Brimars are just the ticket.

The Tung-Sol 6V6's are good tubes but can be ridden to far on high frequency passages by 12AT7's in the M-T. My Phillips SQ 7062's do not show special synergy with these (like with my G ST's), although the combination sounds fine nevertheless.

In all the above suggested combos, I use the RFT EZ80 rectifier rather than the stock JJ EZ81 (not only due to reliability issues).

Some time ago, I decided to skip any output tube outside the 6V6 family due to potentially excessive stress on the circuit and because IMO the original voicing enhances the 6V6. YMMV.

My next test will be a pair of 6414's paired with my tour de force RCA's G ST's. I've heard good things about these drivers and according to the literature, these are very similar to the 7062's.

In general, I prefer to go for drivers offering an intermediate gain between 12 AU7's and 12AT7's, as the former are somewhat dull-sounding in the M-T, whereas the latter tend to be edgy in the high frequency ranges.

The 6V6 G ST's sound big, with wider soundstage, PRAT and transparency, and as has been mentioned here, its bass is better than the rest of my other combos with the ubiquitous OA3's in place. My OD3's, on the other hand, flatten that sound, killing some of the presentation depth.

Yet, the biggest sound improvement from my system came from the installation of 7 DIY absorption pannels, critically placed in the room. There's no question reflections kill the soundstage and naturalness of the sound, and increases listening fatigue. Today, at close to near field, my system behaves neatly and timbres and imaging are again in focus, while bass lines are deeper and well defined (as opposed to boomy).

My system uses an active subwoofer with a crossover at 65Hz and thanks to the absorption pannels now the bass really enhances the nice low-mids, mids and highs of the DM945's when placed on monitor stands and away from walls.

Interested in anyone's experiences with 6414's and the corresponding best output tube pairing.
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« Last Edit: 12/17/13 at 22:27:04 by Fireblade »  

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P K
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Re: Tube Rolling Results for Current MT
Reply #4 - 12/21/13 at 16:05:37
 
I can currently recommend three low cost, but big upgrades.

New Valve Art 350b to replace the 6V6GT

A NOS 12AU7  to replace the stock JJ 12AU7 (I was lucky that my Mini Torii stock tube was a NOS RCA 12AU7 (I did obtained a stock JJ 12AU7 for a comparison). Cost from $20.00 per pair to $100.00+ per pair).

Try to replace the stock JJ EZ81 for a NOS EFT, Mullard or Amperex (you may just wait for the JJ EZ81 to fail, it will not take very long).  NOS EFT EZ81 on ebay for $25.00 per pair
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« Last Edit: 01/06/14 at 13:41:54 by P K »  
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Rivieraranch
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Re: Tube Rolling Results for Current MT
Reply #5 - 12/21/13 at 22:09:26
 
Jim McShane sells the RFT EZ81.
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P K
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Re: Tube Rolling Results for Current MT
Reply #6 - 12/22/13 at 02:46:11
 
An Alternative to upgrading the 12AU7 and the EZ81 is to switch to:

7062 (for the 12AU7)  and an

EZ80 (for the EZ81).

I have been using a pair of Amperex NOS 7062  and a pair of NOS Tungsram EZ80's (until I cracked one of the EZ80's).

I switch back to the NOS RCA 12AU7 and the NOS Mullard EZ81 (the quality from this combination is close to the 7062/EZ80).
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« Last Edit: 12/22/13 at 02:47:38 by P K »  
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Fireblade
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Re: Tube Rolling Results for Current MT
Reply #7 - 12/22/13 at 14:09:34
 
From Brent Jessee's summary on the 350 B tube:

"For most applications calling for a 7581, KT66, or 6L6GC these tubes will work fine and sound great. They do have different filament current draw specs and other slight differences, so you should always check with the amp manufacturer, dealer, or a tech before subbing these tubes in place of the stock tubes."

The 350's (A & B) seem to be considered the best sounding in this tube family. I just wonder if we can use the KT66's safely in the Mini Torii and if the amp's voicing is consistent with their characteristics ... I assume the latter holds as per the recommendations.

Individual good tubes may or may not be special, depending on the accompanying complement set. SQ 7062's are not that special if paired with Tung-Sol, JJ or Reflektor Plant 6V6's, in my experience. YMMV.
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P K
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Posts: 138
Re: Tube Rolling Results for Current MT
Reply #8 - 12/22/13 at 18:01:27
 
When using the Valve Art 350b,

Which combo is best?

12AU7/EZ81

or

7062/EZ80

Let me know your opinions
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« Last Edit: 12/22/13 at 18:01:47 by P K »  
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seikosha
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Re: Tube Rolling Results for Current MT
Reply #9 - 12/23/13 at 12:02:58
 
Hi PK,

Can you describe the sound differences you get with the substitutions that you recommended?

Thanks,

Pete
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P K
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Posts: 138
Re: Tube Rolling Results for Current MT
Reply #10 - 12/23/13 at 15:00:33
 
The Valve Art 350b provides:

A deep soundstage, airy sound, this is the first time i was able to hear this type of detail.

A wide soundstage with music coming from the far left and far right beyond the placement of the speakers,

and most important the high or upper end of the sound range is much more mellow, yet offers a high level of detail.

Others report  "a very nice sound sweet airy but light on the bass".

"Light on the Bass" has not been an issue for me.
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« Last Edit: 12/23/13 at 15:06:55 by P K »  
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grinnell
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Re: Tube Rolling Results for Current MT
Reply #11 - 12/23/13 at 15:52:55
 
Hi Others here Smiley

I found the difference btw the RCA 6v6g st and the VA350's to mainly one of bass.  Your description of the 350's is right on, we differ only the lower end.  The 6v6g's just seem to have more punch in relationship to the 350's

It may be that i'm new to low watt and more used to bigger pumpier tubes like kt88's and el34's
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MT w/ 1940's RCA 6v6g st
Ref 3A de Capos
VPI HW-19 mk iv
Mac Tuna MR-67
MH 25.2 CDP
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P K
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Re: Tube Rolling Results for Current MT
Reply #12 - 12/23/13 at 16:37:10
 
I forgot to mentioned that the RCA NOS 12AU7 sounds better than the new production JJ's.

The overall sound is just better.  It can be argued that a NOS 12AU7 tube will typically sound better then new production (due to better materials and more skilled workers (glass blowing is an art?).

The sound is more open and smoother, or a sweeter sound, with the NOS RCA 12AU7 (since it was supplied to me as a stock M-T  tube by Decware, maybe Steve D. would like to comment).

The JJ 12AU7 is a more sterile, dryer, one dimensional sound in my system.
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P K
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Re: Tube Rolling Results for Current MT
Reply #13 - 12/23/13 at 16:40:09
 
Grinnell,

Can you tell me where to find the 1940's RCA 6V6G ST coke bottle tubes and how much should the cost be.

Thanks,

PK
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« Last Edit: 12/23/13 at 16:50:03 by P K »  
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Fireblade
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Re: Tube Rolling Results for Current MT
Reply #14 - 12/24/13 at 01:41:45
 
In case you are interested, I bought the RCA G ST's from Brent Jesse ($50.00 matched pair). When later I asked him for an additional pair as back-up, he said he was out of them. He said he will make a buying trip early January and he'll probably get them, so I'm holding my order of those plus the 6414's which seem to be another good driver alternative.

I absolutely agree with Grinnel's description of the G ST's and so far the 7062's seem to make the best out of them. Although there could be 12AU7's with some special synergy, I have not been lucky with reasonably priced 12AU7's in the Mini Torii.

Good 12AT7's paired with darker (warm) sounding 6V6's are another good combination IMHO.
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