Tube substitues for the GK-1

raygun · « **on:** 12 Jan 2004, 08:00 am »

Hi guys, I know the the GK-1 uses the 6ES8 tubes.

Can I use equivelant such as the 6DJ8, 6GM8 and 6DG8 instead?

Will they have any effects on output impedance and voltage gain, etc?

Or require any component change to optimise their usage?

Thanks for any answers.

cheers

AKSA · « **Reply #1 on:** 12 Jan 2004, 09:27 am »

Hi Raygun,

Although listed as an equivalent, the 6GM8 was designed for car radio applications and has only 2.6mA/V transconductance, a maximum plate voltage of just 30V and 0.6W plate dissipation. It is unsuited to the GK-1 because the 6ES8 has far higher tranconductance, and the plate voltage is set at 92V and dissipation at just under 0.8W per section making the low voltage tubes entirely unsuitable. The ECC86 and 6DG8 are almost identical to the 6GM8, being used in the same automotive, low voltage application.

You can use the 6DJ8, however it will deliver a slightly less engaging sound. Like any tube circuit, you can change the presentation by tube rolling with different types and brands, but only within the limitations set by the principal electrical parameters of the 6ES8.

Cheers,

Hugh

cmscott6 · « **Reply #2 on:** 12 Jan 2004, 02:10 pm »

Hey Raygun,

I tried 6DJ8's from a friend, and I can echo Hugh's comments about loss of engagement in the sound: it really felt like those tubes took all of the magic (depth of image, clarity) straight out of the GK-1.

I've had some fun just switching types of 6ES8. My hands-down favorite is a couple of GE "Made in Great Britain" ones from the fifties: wonderful, deep image to the music, clear highs and balanced lows. Older Sylvania tubes sounded pretty good, too. Good luck!

raygun · « **Reply #3 on:** 13 Jan 2004, 02:16 am »

Thanks for the replies guys.

So the plate voltage is set at 92V and dissipation at just under 0.8W per section?

What is the operating voltage?

I'm looking forward to acquiring a GK-1 in a months time.

cheers

AKSA · « **Reply #4 on:** 13 Jan 2004, 06:11 am »

Raygun,

That's it; 92V appears across the tube!

Cheers,

Hugh

raygun · « **Reply #5 on:** 13 Jan 2004, 06:32 am »

arghh... sorry Hugh, I meant to ask whats the operating current.

I'm asking for a buddy who has no internet access. He's interested in the GK-1 as well.

Theoratically, how long will the tubes last?

Cheers

AKSA · « **Reply #6 on:** 13 Jan 2004, 06:44 am »

Raygun,

The tubes run around 9mA, and should last at least 5 and up to 15 years in normal operation. The plate current is rated in constant commercial operation to 15mA. In fact tube life will be primarily influenced by how many times the filaments are switched on; filaments are savaged by turn-on surges, typically ten times the steady-state current.

Cheers,

Hugh

JohnR · « **Reply #7 on:** 13 Jan 2004, 07:21 am »

Hugh, could an NTC thermistor in series with the filament help tube life?

AKSA · « **Reply #8 on:** 13 Jan 2004, 07:35 am »

John,

Yes, in fact any resistor if the secondary of the filament transformer is rated at higher voltage.

However, it probably isn't necessary; study the commercial tube industry and you will find it was very rarely ever done.

Cheers,

Hugh

JohnR · « **Reply #9 on:** 13 Jan 2004, 07:40 am »

Ah yes. So if one rectifies the filament supply and then uses a dropping resistor, then one's tubes are "protected" to some degree already

Cool

AKSA · « **Reply #10 on:** 13 Jan 2004, 07:52 am »

John,

I don't recommend using DC on the filaments.

It creates voltage gradients across the cathode, very small, but sufficient to make the music sound a little 'flat'.

Cheers,

Hugh

raygun · « **Reply #11 on:** 13 Jan 2004, 08:53 am »

The 6922 should last longer due to its higher specs.

Anyone tried it in the GK-1 and care to comment on its performance?

cheers

AKSA · « **Reply #12 on:** 13 Jan 2004, 09:48 am »

I defer to others who have tried it........

Steve, you there?

Cheers,

Hugh

blizzard · « **Reply #13 on:** 13 Jan 2004, 01:48 pm »

Hi All,
I have just tried a JAN Philips 6922 in place of the stock 6ES8 in the GK-1. My initial feeling was that the music became more detailed but with more sibilance. However, after going back and forth a number of times, I now feel that the stock 6ES8 sounded much better. I felt that the 6922 maintained the 6ES8's engagement and 3-D spatial characteristics. But, it was just way too harsh. Which killed it for me. After even a short period of time it became unlistenably tiring. Initially, I had felt that maybe after some break-in the tube might sweeten up. And, with it's added detail migh even best the 6ES8. But, it just has way too far to go.
I would like to emphasize that the differences were very obvious. Even after a long break between blind listening tests, you could tell which tube was in place. The 6ES8 was much sweeter. Hugh has done an outstanding job of dialing in this tube for the GK-1.
Of course, these are my impressions in my system. And, I only compared the two tubes. Others set-ups and/or tubes may yield different results.
Good Luck,
Steve

JohnR · « **Reply #14 on:** 13 Jan 2004, 10:59 pm »

Quote from: AKSA

I don't recommend using DC on the filaments.

It creates voltage gradients across the cathode, very small, but sufficient to make the music sound a little 'flat'.

Even with indirectly heated filaments?

Crikey... well that's an interesting piece of information, I will have to try an experiment. Thank you

T-Bone · « **Reply #15 on:** 13 Jan 2004, 11:32 pm »

Anyone try the National 6ES8 made in England?

Occam · « **Reply #16 on:** 14 Jan 2004, 01:06 am »

Quote from: T-Bone

Anyone try the National 6ES8 made in England?

Aren't you a lucky dog..... Those aren't manufactured by National, but rather National is the Richardson house brand, and that 6ES8 was probably manufactured under the Phillips umbrealla, by Mullard or Valvo.

I've used them in a TLP and they're lovely. As are the 'Nationals' made by Tungsram, which are recognizeable by that 'Made in Hungary'. And you'll find that most of the US branded are similarly manufactured by Phillips. I've heard that the bestest are Telefunkens, but I'm too cheap.

The trick is to generally ignore the brand label (at least for the 6ES8s) and look at the manufacturing code. For where and what to look for, visit here, and to satisfy your most obscessive desires (what, where, when) -
http://www.cs.helsinki.fi/u/oheinone/valves/pvm-coding.html

T-Bone · « **Reply #17 on:** 14 Jan 2004, 02:22 pm »

I bought 10 of these on a wim from a guy up in Canada some time ago for about $3 bucks each. Unfortunately I'm not the "valve" detective that some of you guys are. The information you provided mentioned a mfg code etched in the glass. It's probably there but I couldn't find it. You can't expect much from a blind old truck driver with no teeth that's deaf in one ear and can't hear out of the other.

Anyway here are a few photos of the "valve" suspect in question. There is a final photo to be posted that will show a mfg insignia. As soon as my camera's batteries are recharged I'll post it.
http://f1.pg.photos.yahoo.com/ph/kizer57/album?.dir=/Valves

ginger · « **Reply #18 on:** 16 Jan 2004, 06:11 am »

I substituted some modern production JJ Tesla ECC88 (6DJ8) for theECC189 (6ES8) on the work bench and very carefully measure all operating voltages and currents.

The ECC88 (6DJ8) goes in without any requirement to change any circuitry or component values.

My experience was as others have stated above. The ECC88 loses a little engagement provided by the ECC189 most noticable at high output levels.

This is as you might expect - the ECC189 is a variable mu tube, that is at smaller tube currents the mu drops off compared with the ECC88. This happens on the negative signal excursions. That is we are applying asymmetrical distortion and asymmetric distortion means 2nd Harmonic Distortion - the euphonic (warm) stuff.

Cheers,
Ginger

andyr · « **Reply #19 on:** 16 Jan 2004, 07:12 am »

Quote from: T-Bone

.... I...

T-bone, I see you listen to Dire Straits. Good man! I think I like the first album best - i've got a Jap pressing which sounds pretty nice, I reckon.

Regards,

Andy