GK1 Tubes

stvnharr · « **on:** 28 Oct 2005, 06:29 pm »

Not exactly a new topic, but it's been several months I believe since anyone posted anything about tube rolling experiences in their GK1. Just curious if anyone has anything new or of interest in this regard. There are a lot of inexpensive and expensive NOS 6922, 6DJ8 and 7308's. There are even a few 6ES8's around for 20+USD.
Anyone admit to trying 50USD or 100USD tubes in their GK-1?
Just curious, that's all.

cmscott6 · « **Reply #1 on:** 29 Oct 2005, 12:32 am »

I haven't rolled any new ones lately, but I'm still standing by my NOS GE 6ES8. Boxes are stamped Made in Great Britain, and I'm not enough of a tube manufacturer junkie to know who made the tubes originally, but they sound great.

Tried some NOS RCA's as well as some newer GE's and none were close to the Made in GB's: great imaging, and (IMO) not much coloration. By this I mean high's are very crisp and clear (the other tubes seemed to dampen and muddy the high's). Granted, I didn't give the other tubes hours and hours to burn in, but hey, the whole exercise was fun, and I got really lucky - getting the tubes from a surplus place for a few bucks per.

Anybody else tryin' anything?

Chris

dcs · « **Reply #2 on:** 29 Oct 2005, 11:03 pm »

No big bucks here, but I swapped out the supplied National ECC189s which were getting very noisy for a pair of Siemens 7308s. I had a quick go with a pair of drop in relacement Mullard ECC189s, and a pair of Mullard ECC88s but found the Siemens to be clearer and more transparent.

However, I didn't spend a great deal of time burning the others in - the sound of the Siemens was immediately appealing.

I guess with winter coming up I might get around to playing around with the other tubes - anyone have any other recommendations?
Cheers,
Dave

AKSA · « **Reply #3 on:** 30 Oct 2005, 01:40 am »

Steven, Chris, Dave,

Tube rolling is fun with the GK1, but the best of them by consensus amongst a few cognoscenti here in Melbourne is the gold pin Siemens 7308, a masterly performer.

But all of them are pretty good since the tube is not used in a gain situation, but as a cathode follower, where microphonics and other tube nasties are not evident.

Cheers,

Hugh

stvnharr · « **Reply #4 on:** 30 Oct 2005, 03:13 am »

I went browsing thru the old posts here to get refreshed, mostly of what the tube does in the GK-1.
In browsing thru some of the "better" tube vendors I find there is a lot of variation in the tube types. Thus, there is not just one Siemens 7308, but they all have gold pins, otherwise they are fakes. There's also a lot of variation in price. Of course the pricier ones are mostly profit as the market will bear it. Yet, what's the point in buying something cheap if it's lesser performing?
There seems to be even more "choices" in the 6922's. And not everyone believes the 7308 is automatically better than the 6922.
Anyway it's all been interesting reading.

stvnharr · « **Reply #5 on:** 30 Oct 2005, 04:37 pm »

Quote from: AKSA

But all of them are pretty good since the tube is not used in a gain situation, but as a cathode follower, where microphonics and other tube nasties are not evident.

Does this mean that one does not necessarily need the lowest in microphonics here, such as in the super premium price tubes.
Kevin at Upscale uses 3 grades. Would Dac/driver grade (half the price) be suitable for the GK-1 application?

In the Aksa tradition of wise spending of dollars.............

AKSA · « **Reply #6 on:** 30 Oct 2005, 09:09 pm »

Steven,

I would agree with your suggestion. Use the cheaper option.

Cheers,

Hugh

fred · « **Reply #7 on:** 22 Nov 2005, 11:11 pm »

Stvnharr - Did you ever give this a try? If so, we're interested in the results.

stvnharr · « **Reply #8 on:** 23 Nov 2005, 03:23 pm »

Fred,
I did purchase a pair of 7308's from Andy Bowman at Vintage Tube Services, but haven't received them yet. I'll make a post here when I get the tubes and have some time with them in the GK-1. Might be awhile however.

JoshK · « **Reply #9 on:** 23 Nov 2005, 03:46 pm »

Would the 6N1P russian tube work? Its pretty cheap and easy to come by and many in the DIY realm seem to love it. Its supposedly very close to the 6DJ8 but a slightly higher heater current requirement.

pabiz · « **Reply #10 on:** 24 Nov 2005, 10:31 am »

hey friends
I'm writing from ITALY,very cold winter this year,so I enjoy myself with my lovely AKSA gear (gk1 +AKSA 55 nirvana+).
I tried some tube rolling too,the original 6es8,a pair of 6922 ElectroHarmonix,and a pair of Philips ecc88 SQ.
I can say this:

1-original 6es8,nothing to say we know them very emotional but little less precise than 6922.
2-6922 ElectroHarmonix very very precise but 0 emotion
3-NoS Philips SQ best choice very very good emotional engaging live effect.

my classified

1° nos Philips ecc88 SQ
2° original 6es8
3° 6922 ElectroHarmonix

This is my experience in my house with my ears,I hope this helps.
I woul like to try the Siemens 7308 gold-pin too but it's very very expensive tubes and I prefer to buy cd.

bye bye evrybody

Paolo Bizai

nareshn · « **Reply #11 on:** 11 Dec 2005, 05:08 pm »

I have seen the answer in some posts but unable to find the same.
Request reply.
When do the GK1 tubes need replacement considering 2hrs
of usage everyday?

AKSA · « **Reply #12 on:** 11 Dec 2005, 09:03 pm »

Hi Naresh,

The GK1 tubes are run at 8.5mA; the tube will stand 15mA in continuous commercial use and up to 22mA peak. Dissipation is 780mW; max for the 6ES8 per section is 1.8W. I have also slightly reduced filament voltage to 6V for increased life. The tube is thus run at around 43% of allowable dissipation, and should last around 15 years at 2 hours per day.

I'm hoping to be around when the reports of this outstanding life come rolling in.......

Cheers,

Hugh

stvnharr · « **Reply #13 on:** 27 Jan 2006, 06:10 am »

Hi all,
I have at last been able to install the NOS 7308 tubes in my GK-1, listen, and do a comparison to the stock 6ES8 tubes. I’ve had two comparative listens, one by myself, and one with another listener, Listener B shall we say. The system consisted of a Marantz 8260 sacd player, Aksa 55N+ amplifier, Osborn Titan Reference speakers, Critical Q subwoofer, and my diy cables. My listening habits are mostly classical sacd’s with a few others mixed in. For these comparative listens I used just two pieces of music, so as not to confuse one musical memory, and require note taking; the first few minutes of Rachmaninov’s Third Symphony on a fine new Exton Japanese recording, and a familiar (to me anyway) song from blues singer guitarist Eric Bibb, an sacd from a 10 year old Opus 3 recording, with only the singer, his guitar, and a bass player.
Both sessions were conducted the same way, back and forth between tubes and selections until differences/opinions were fully formed. With the second listener, no mention of which tube was in the GK-1 at any given time until the session was complete.
The differences between tubes were consistent to me in both sessions. Listener B and myself both heard essentially the same differences between tubes, though there was some difference.

7308
Me – bigger sound on orchestra strings and the orchestra as a whole
much better bass and bigger sound presentation on the blues singer

Listener B – smearing of string sound, though slightly larger presentation,
tube bloom on the orchestra
smearing of leading edge to notes, and stereo image better bass on the blues tune

6ES8
Me- smaller sound on orchestral strings and orchestra as a whole
smaller sound presentation on blues song with a little less bass
clean lines to notes, somewhat solid state like in presentation

Listener B – clean sound to the strings on the orchestra with no smearing
much clearer stereo image with the blues singer, with a clean, clear leading edge to the notes

In the end we both agreed that the stock tube gave a somewhat solid state like presentation to the music while the NOS tube gave a bit of tube bloom to the sound.

I preferred the NOS tube, and Listener B preferred the Stock Tube.

Listener B was the GK-1 designer. And I don’t find it surprising that he chose the stock tube as preference.

Myself, I’ve come to enjoy the sound with the nos tubes. Since 90+% of my listening is to classical music, I’m not really concerned with leading edges and such, preferring the small bit of tube bloom with the nos tubes.

In the end it really does all come down to personal preference, irregardless of all else.

As for the NOS tubes, these were a pair of 1964 Amperex USA that I purchased from Andy Bowman at www.vintagetubeservices.com. Andy’s price of $130 plus shipping was cheaper than the dac grade Siemen’s Rohre 1980’s 7308’s from Upscale Audio, and WAY less than the other tube vendors of NOS tubes, where these Amperex tubes are often listed at $300-400 per pair.

For the money, I dunno, could have bought quite a few discs and enjoyed them just as much. But sometimes curiosity and doability overcome everything else.

jules · « **Reply #14 on:** 31 Jan 2006, 12:11 am »

thanks for the report stvnharr,

given the cost of tubes it's great to be able to learn from your experience. It would be something of a disaster to spend say $500 on a range of tubes to find that you didn't like them.

On the other hand it would be intriguing to be able to create a "tunable" AKSA using the options of a choice of tubes and maybe a choice of GK-1 pre-amp in or passive, stepped attenuator, pre-amp (suggestion from Rhythm Willie a while back).

jules

DSK · « **Reply #15 on:** 31 Jan 2006, 04:01 am »

Stvnharr, the 'bigger presentation & soundstage' you heard from the NOS Amperex 7308's is similar to what I heard from the NOS Siemens 7308's (details here http://www.audiocircle.com/index.php?topic=7379&postdays=0&postorder=asc&start=20) in my modded GK-1 a couple of years back. Fortunately, they are still going strong

stvnharr · « **Reply #16 on:** 31 Jan 2006, 04:10 am »

Quote from: jules

thanks for the report stvnharr,

given the cost of tubes it's great to be able to learn from your experience. It would be something of a disaster to spend say $500 on a range of tubes to find that you didn't like them.

On the other hand it would be intriguing to be able to create a "tunable" AKSA using the options of a choice of tubes and maybe a choice of GK-1 pre-amp in or passive, stepped attenuator, pre-amp (suggestion from Rhythm Willie a while back).

jules

Jules,
I'd have to say that spending the "normal" amount of money on NOS tubes, the 300-400 USD that they go for is definitely NOT good value. I'm not even sure that what I spent was really good value. It's just that I wanted to do it, and it was the cheapest way to get the 7308 tubes and be sure that they would work. Andy told me that 80-90% of the 7308 tubes are complete duds, with the highest failure rate of nearly any NOS tube.

If you wire a "sub out" from the attentuator and bypass the tubed output stage, that is a passive w/gain stage and it is easy to compare the sound of the output stage to, well, essentially a passive.
But it's the tubed output stage of the GK-1 that is the real feature of the product.

Steve

JoshK · « **Reply #17 on:** 11 Feb 2006, 01:28 am »

sorry for the ad, but I got a quad of 6ES8 that I decided I won't be using.... I need to look up the brand, but I think it was RCA iirc. I will offer them at what I paid less shipping.

stvnharr · « **Reply #18 on:** 12 Feb 2006, 11:19 pm »

Quote from: DSK

Stvnharr, the 'bigger presentation & soundstage' you heard from the NOS Amperex 7308's is similar to what I heard from the NOS Siemens 7308's (details here http://www.audiocircle.com/index.php?topic=7379&postdays=0&postorder=asc&start=20) in my modded GK-1 a couple of years back. Fortunately, they are still going strong

I'd like to think that most working 7308's are close enough in spec to give similar results, despite what some may say about the various brands and years.
With that in mind, perhaps a value conscious way to go with these can be had from Andy at vintage tube services with his Japanese Matsushita tubes. He has plenty of them, and I don't think they are terribly expensive. But you have to call him to find out.

ginger · « **Reply #19 on:** 13 Feb 2006, 02:51 am »

Gingers "Opinion" based upon tube theory.
The 6ES8 (ECC189) and all their variants are different from 6N1P,6922,6DJ8,ECC88 variants in that the 6ES8 (ECC189) is a VARIABLE Mu tube. At the operating point (8mA) the mu of both types is very similar. The differences will become apparent when you start swinging significant output signal voltage. As the current in the tubes drop on positive signal excursions the mu of the 6ES8 drops. This results in asymmetrical distortion. Asymmetrical distortion is 2nd harmonic distortion. Most of this is corrected by the fact that the output stage is a cathode follower with nearly 100% negative feedback. That is the 6ES8 is adding a small amount of signal level dependent 2nd harmonic distortion. The higher the signal level the higher the 2H distortion. (Its like a unidirectional compressor).

That is why the 6ES8 (ECC189) seems to add that little something.
AND
Its why the 6N1P/6922/6DJ8/ECC88 sound a bit more detailed but at the expense of that "something".

I ran modern production JJ Electronics ECC88 for awhile and was initially seduced by the detail and dynamics. After extended listening however I am back with the original ECC189.

Preference will be heavily dependent on the sound of your power amp (how much 2H it already has) and the signal level required by it to produce your normal listening level.

Cheers,
Ginger