[OctavianH]

If you use that kind of board with long wires attached they become antennas for noise pickup as well. Especially grid wires for the input tubes are extremely sensitive. You could use shielded wires of course to get around that problem.

I never thought too much about it. I only wanted to exemplify a kind of "adjustable adapter" which can be a useful tool for the tube roller.

By the way guys, in order to show my tube collection that I make no discrimination, I just bought a pair of gay tubes. Yes! My tubes can have what sexual orientation they like.
More exactly: a pair of 6L6GAY! Now the black or grey coated tubes which always tell me that I always prefer clear glass have nothing more to say. I hardly wait to receive them.

 

[SonicTrance]

I never thought too much about it. I only wanted to exemplify a kind of "adjustable adapter" which can be a useful tool for the tube roller.

By the way guys, in order to show my tube collection that I make no discrimination, I just bought a pair of gay tubes. Yes! My tubes can have what sexual orientation they like.
More exactly: a pair of 6L6GAY! Now the black or grey coated tubes which always tell me that I always prefer clear glass have nothing more to say. I hardly wait to receive them.

I needed a laugh today. Thank you!

 

[hpamdr]

If you use that kind of board with long wires attached they become antennas for noise pickup as well. Especially grid wires for the input tubes are extremely sensitive. You could use shielded wires of course to get around that problem.

You are more than right, this can be only a temporary test. To prevent antenna effect you can cover the "in air" adapter with tube in a metallic can once placed on the amp. This works only if you have enough space on the amplifier and with single tube unless you have big metallic box...

@OctavianH you can use beer can once opened and add insulating tape to the bottom to protect the amp.

@OctavianH @SonicTrance :: I think that a big warning should be put on top of this thread about possible damage can occurs to the amp if wrong tube is placed or wrong adapter is used.. In case of short circuit, you an blow capacitor or worse. I think Tomas can sentence it in better way.

 

[OctavianH]

@OctavianH @SonicTrance :: I think that a big warning should be put on top of this thread about possible damage can occurs to the amp if wrong tube is placed or wrong adapter is used.. In case of short circuit, you an blow capacitor or worse. I think Tomas can sentence it in better way.

I put a warning about tube rolling in the 3rd post. Also with signs. I will, of course, add more if necessary.

Brrr, I grabbed also a pair of Sylvania 5932 for 50 EUR. My mother always told me not to play with Ebay.

 

[hpamdr]

I missed the warning on post 3...

Clarification needed:

• Situation of Melz 6H12C

• 6n12s could be used in input stage but not in output. But it could be on the limiting value 4ma by triode at 200V with -15V on the grid. I would personally avoid it and keep it for OTL as output tube.

• Situation of 6F6G
• Situation of EL35 (probably not)
• Situation of 5881
• Situation of 5932 (more powerful 6L6)

• All seems to be OK for me. The EL35 is almost the same as EL5 and EL36, infinity will have no issue at all to bias. @SonicTrance With eternity this should be OK but we need to get the right voltages and limits to bias at 20mA ..

 

[OctavianH]

@hpamdr And I also think 6CA7 should be fine as output for both Infinity/Eternity. What do you think?

 

[DecentLevi]

Hi folks, I just pick up a Elekit 8200. So will be rolling KT88, 6L6G, EL34, KT77, KT66, EL12 spez.

UT gets an ELkit amp? I wouldn't expect it any other way ... this is of course coming from UntilThen,#1 fan and master trailblazer of all EL tubes on Head-Fi. How could I ever forget your unwavering proclaim of the good old EL3N, followed by EL11, 12, Spez,... then H1 broke out the EL32, EL38, 39, now we know the 34, 36, etc. Good tubes indeed.

 

[UntilThen]

DL, I don't want to derail this thread but you can hop over to the Elekit 8200 thread for my impression of this Japanese marvel kit. Drives speaker and headphones. In addition to a lot of NOS tubes I'm getting - the sum total is many times more than the price of the amp... and I'm getting a matching TU-8500 which is a preamp and phono stage to partner the TU-8200. 8w in ultranlinear mode and 8.2w in pentode mode and 4w in triode mode.

Getting GEC KT66, Philips Miniwatt EL34 / 6CA7 xf2, GEC KT77, Tung Sol NOS 6550, Radiotron 807 D^D, and a whole lot more.... finally I'll leave the best and most expensive to the last - GEC KT88 at AUD $1100 a pair.

 

[DecentLevi]

Wow UT, do you prefer the ELkit more than the Ultrasonic Oblivion or the Alo Audio Studio Six amp? Amazing sounding collection. You should be able to use most with a future Ultrasonic Eternity amp should you get one too.

Also guys, in case anyone missed it on the 2359Glenn thread, they've discovered a tube class called 6J7. It's a pentode and the successor of 6C5. It's compatible in a 6J5 socket (as two single tubes with two adapters), or 6SN7 socket (as two dual tubes in a single adapter).

These 6J7's actually work with an EL32 adapter including with the same top connection; in the above mentioned tube sockets. I verified this with adapter maker @Deyan and another user. Further I was told these can also work as output tubes in the KT66/EL34 socket with the same EL32 adapter, in single mode. I'm not sure if the grid bias would be of concern or not though when using as an output tube. As you can see there's both metal 6J7 and ST (curved) versions called 6J7G, going way back to the era of curvey tubes that not only look beautiful but many sounding more organic and rich in general.

metal 6J7

ST / curved 6J7G - many versions of these

 

[DecentLevi]

Yes! I'll make it easy for you and say that all output tubes, except for the EL32 @ 40mA, should run @ 50mA.
...
You can measure yourself with the DMM set to at least 300VDC. Put black probe in black banana jack and red probe in pin 3 of the output tube socket. You count the pins counter clockwise from the guidepin. When the voltage is down to a couple of volts you're fine.

Hope that helps.

Wow Tomas I get what your saying but it seems surprising. Do you mean to say that out of all the output tube types I listed for my amp I will set everything at the same 50mA grid voltage adjustment except for the EL32 at 40mA? I really want to ensure these are all set to the most optimal operating point so I don't mind fine tuning to to more exact bias amounts, if you have more precise recommendations.

Also all the input tubes I wanted to use are the same at 4mA so no adjustment needed?

So pin 3 for my KT66 socket would be at the black arrow above, right? And facing towards me this would be in reverse.

 

[UntilThen]

Wow UT, do you prefer the ELkit more than the Ultrasonic Oblivion or the Alo Audio Studio Six amp?

Those 3 amps are very unique in their own ways. These days I don't say outright that one is definitely better than the other. I've sold off my Studio Six btw. Oblivion is still with me but Elekit 8200 is exciting in being able to roll all those big tubes with auto bias and sound great.

 

[UntilThen]

UT gets an ELkit amp? I wouldn't expect it any other way

After you read all the glowing reviews, you will know why I'm impressed with what I heard.
https://www.head-fi.org/threads/elekit-300b-amp-kit.869957/post-14049028

 

[SonicTrance]

Do you mean to say that out of all the output tube types I listed for my amp I will set everything at the same 50mA grid voltage adjustment except for the EL32 at 40mA?

You need to understand the tube curves, Levi. The mA meters on the amp will measure plate current. We always want the plate current the same at 50mA with the exception of the EL32 at 40mA. The plate voltage is fixed at 200V. To reach the 50mA plate current we set the grid voltage. That voltage will be very different for different tubes.

Here's two examples:
This is the 6V6 tube. As you can see I've drawn red lines from 200Va and 50mA Ia. Those lines intersect at about -7Vg (look at the grid curves!). So to get 50mA of plate current for the 6V6 you set the grid voltage to -7V with the help of your external DMM connected at the measuring points on the amp.


Here we have the KT88. Plate voltage is still same of course at 200V. We still want our 50mA Ia. This time the red lines intersect at about -19Vg. So to use the KT88 you set the grid voltage to -19V.


If you would insert the KT88 with the grid voltage set to -7V (setting for the 6V6), how much current would it draw? About 180mA! Bad things would happen at that point, lol! It's important you understand this.

Also all the input tubes I wanted to use are the same at 4mA so no adjustment needed?

Adjustments are needed just the same as the output stage. It all about the curves! Study them!

Btw, just to make things more complicated you can also use the 6SL7/ECC35 in the input stage! This will need to be run at 3mA instead of 4mA

 

[OctavianH]

@SonicTrance A protection mechanism to limit the current to a max value (i.e. 50mA on the example above) cannot be done?
(and not fuses)

 

[SonicTrance]

@SonicTrance A protection mechanism to limit the current to a max value (i.e. 50mA on the example above) cannot be done?
(and not fuses)

Why not fuses? I can fuse the output and input tube cathodes. Output tubes at 125mA combined and input tubes at 10mA combined. Can have the fuses on back panel. I guess it's a good idea.