TU-8200 Compatible Power Tubes

Hello,

I just purchased the TU-8200DX kit, and although it hasn't even arrived yet, I've started going through my tube stash pulling out all of the 6L6GC tubes I have as well as their relatives. I haven't been able to locate a list of all of the compatible tubes for this amp, other than what is advertised by Elekit (6L6GC, KT66, KT88, EL34, etc.). Sounds like the voltages in the 8200 are too high for the original 6L6 metal base 6L6G varieties, however can someone confirm whether or not the following can be safely used (regardless of pentode, triode or UL modes)?

  • 5881/6L6WGB
  • 807 (with adapter)
  • 6BG6 (with adapter)
  • 7581

Any others that I'm not thinking about? Has anyone measured the plate and screen voltages applied to the power tubes in the TU-8200?

Thanks for your help!
 
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Hello, I just purchased the TU-8200DX kit
(...) Has anyone measured the plate and screen voltages applied to the power tubes in the TU-8200?

Hi,

If your kit has been shipped then I assume you have already received the manual in email or have downloaded it from somewhere.

The schematics are on page 19 with many reference points and related voltages.

Here is the list of approximate working conditions that you should expect from the power tube without signal. Note that the FETs in the power supply are used for filtering but like in most tube amps, none of the voltages are regulated so they depend on your line voltage.

Ua = 260 V
Ug2 = 260-270 V depending on mode
Ia = 71-75 mA (plate dissipation = 18.5-20 W)
Ig2 = 3 mA (with 6L6GC)

The usual limiting values are anode dissipation, screen grid voltage and heater current. GLG6B is on the edge with 2 parameters out of these 3 so it should not be used.

Also note that the protection circuit prevents damage from control grid issues (when the tube cannot be biased) but not from screen grid (or plate) shorts so be careful with old tubes. Victor already mentioned that this will be addressed in the new release.

Some design parameters suggest that the amp is optimized for 6L6GC in UL mode.
 
Thank you, all, for the very helpful info on specs and power tube options. Sounds like I have a number of suitable options on hand for rolling power tubes, should I ever find the need.

I haven't received the amp yet, but it has shipped from the supplier. That said, I haven't been emailed with any sort of manual. Was the supplier supposed to email me an English language version or something?
 
Hi Spencer, this amp was in my cycling “pain cave” so I didn’t do any critical listening unfortunately. They definitely had a robust character, “thick” if you will which I enjoyed, but I didn’t compare them to other tubes so that could be the character of the amp! Sorry I can’t be more informative!
 
Hi Ron, Informative enough, thank you. I have the Tung Sol 7581A tubes in my TU-8200 running now for 66 hours and they dó sound more robust and 'thick' than the stock JJ 6L6GC. Some say they need 100 to 150 hours to break in. We'll see. But I like them already. Powerful, detailed, controlled, spatial and never harsh. Excellent tubes. Bargain.
 
EL84 usage? Elekit TU-8200 dx

Hi Paczeltf,

I have basic questions I'm afraid.

Can EL84 moreover E84L tube be used anyhow with TU-8200 please?

Understand pins are different but that can be solved with an adapter.
I'm unsure about current limitations and further specs.
I enclose a data sheet of Siemens E84L. If you can help reading the thing.

Can a YellowJacket adapter be a solution?

These claim to allow to convert E84 to 6l6 type of thing including gc. There are many types that convert voltage, drop power, bypass the bias of the amp etc, and any combination, seemingly.

Link
Detailed Information | Yellow Jackets


Appreciate your insight, expertize.

Thanks much
Sandor

Hi,

If your kit has been shipped then I assume you have already received the manual in email or have downloaded it from somewhere.

The schematics are on page 19 with many reference points and related voltages.

Here is the list of approximate working conditions that you should expect from the power tube without signal. Note that the FETs in the power supply are used for filtering but like in most tube amps, none of the voltages are regulated so they depend on your line voltage.

Ua = 260 V
Ug2 = 260-270 V depending on mode
Ia = 71-75 mA (plate dissipation = 18.5-20 W)
Ig2 = 3 mA (with 6L6GC)

The usual limiting values are anode dissipation, screen grid voltage and heater current. GLG6B is on the edge with 2 parameters out of these 3 so it should not be used.

Also note that the protection circuit prevents damage from control grid issues (when the tube cannot be biased) but not from screen grid (or plate) shorts so be careful with old tubes. Victor already mentioned that this will be addressed in the new release.

Some design parameters suggest that the amp is optimized for 6L6GC in UL mode.
 

Attachments

  • E84L-Siemens.pdf
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Thanks Ferenc

By the way, may I ask what tubes you've considered to use and which if these you finf a good match sonically?

It appears that, 6l6gc may fit technically best, being a 6l6gc amp primarily, also that the output transformer might drop voltage should a EL34 or KT-88 be used.
My candidate is KT66 and maybe KT77.

I do not know if upgrading the transformers would help usage of the further tubes, but I'm thinking any tube including 6l6gc would benefit of it. Not sure why a 6.0 volt one is used as opposed to more standard 6.3.
Have you considered or made such update if I may?

Many thanks

Sandor
 
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If you look at the above mentioned thread that I opened then you will see some comments on the 6V heater voltage. It is actually not that bad, if you use it with the stock configuration then the heater voltages will be above 6V.

The KT66 is a more linear beam tetrode than the 6L6GC. I enjoyed the TAD KT66 that I had bought for a try but finally returned to RCA 6L6GC (7581A) as it sounds more organic.
 
Thanks a lot paczeltf for the many details.

I would need to find a service to make updates in the amp, not my area of expertize at all.
I purchased my one assembled, think the only upgrade made was of capacitors.

The sound is somewhat too coloured and sweety for my taste, similar to your and some others' view.

I tried EL34 tubes too, with mixed result sonically and technically.
KT77 Saratov made is just breaking in, good initial results; between EL34 and 6l6gc, around half way. Way more bass, air and just a bit less mids. So is fine for my taste, sonically.

I'll try Shuguang Black Treasure KT66, if anyone interested can report back. I try to get sustainable source of spare tubes for the power ouput. I run NOS ecc82 Telefunken that I can only recommend, made it a different amp.
I give a try to 6550 GE ones soon, too.

Sandor
 
Hi PaczeltF,

Thanks - I played with the tubes in the preamp section and you may be right. Sounds a good idea to look at whether actually it's me creating issues in case I change a setup. Still some sweetness comes from the power tube section as I hear, or just from the whole somehow.
If I need to choose between somewhat sweety sound vs what JJ Ecc82s give, a clean but lifeless sound, I choose the first.
Is Tungsram ecc82 a linear sounding tube if I may?

I noticed my TU-8200 has no jumpers inside that'd allow to change modes UL, triode and pentode. I asked the local shop I purchased from and got confirmed they soldered the pentode mode, for some reason. Gosh.
Think will bring back to fix it. And why the pentode, if any?

I also noticed that TU-8800 looks to allow UL or triode mode.
For my education, what does UL really do? Can it really blend the good from pentode and triode modes?
The Elekit manual just says it's meant to be an intermediate mode between the two other. And sonically, can one say UL is more close to either the pentode mode or the triode?

I enjoy writing irrelevant things in a thread it does not fit to.

Well I connected my Benz Ace MC via an all valve phono stage to the TU-8200. Wow. Welcome music.

Thanks a lot.

Sandor
 
Hi PaczeltF,

Thanks - I played with the tubes in the preamp section and you may be right. Sounds a good idea to look at whether actually it's me creating issues in case I change a setup. Still some sweetness comes from the power tube section as I hear, or just from the whole somehow.
If I need to choose between somewhat sweety sound vs what JJ Ecc82s give, a clean but lifeless sound, I choose the first.
Is Tungsram ecc82 a linear sounding tube if I may?

I noticed my TU-8200 has no jumpers inside that'd allow to change modes UL, triode and pentode. I asked the local shop I purchased from and got confirmed they soldered the pentode mode, for some reason. Gosh.
Think will bring back to fix it. And why the pentode, if any?

I also noticed that TU-8800 looks to allow UL or triode mode.
For my education, what does UL really do? Can it really blend the good from pentode and triode modes?
The Elekit manual just says it's meant to be an intermediate mode between the two other. And sonically, can one say UL is more close to either the pentode mode or the triode?

I enjoy writing irrelevant things in a thread it does not fit to. :D

Well I connected my Benz Ace MC via an all valve phono stage to the TU-8200. Wow. Welcome music.

Thanks a lot.

Sandor
 
Member
Joined 2018
Paid Member
Hi Sandor,

Is Tungsram ecc82 a linear sounding tube if I may?

The Tungsram sounds much better than the stock Chinese 12AU7 that came with my amp, but I doubt that is because better linearity. All ECC82 types of tubes share the same specifications. You need to go with a different tube family for better linearity, which is what I did.

For my education, what does UL really do? Can it really blend the good from pentode and triode modes?

All these modes relate to the extent of the modulation of screen grid voltage with the output signal, which creates a local negative feedback in the power tube section.

In pentode mode, the screen grid is connected to a fixed voltage with no feedback, in case of the TU-8200 it is the power supply voltage (B+). This gives the highest output power (well this is why tetrodes were invented), but also the highest output impedance and distortion in general.

In triode mode, the screen grid is connected to the anode giving 100% modulation. This will result in a triode-like characteristics with better linearity and lower output impedance, but the power drops more than 50%.

The so-called "Ultralinear mode" was invented trying to do some experiments with partial feedback rather than calculations. It turned out that about 40% modulation on the screen grid coming from an intermediate tap of the output transformer gives almost as much power as pentode mode with distortion figures being close to the triode mode. This is the preferred mode in TU-8200 as well.

There is a lot of information available on the net, search for "ultralinear mode plate characteristics".
 
Hi PaczeltF,

I noticed my TU-8200 has no jumpers inside that'd allow to change modes UL, triode and pentode. I asked the local shop I purchased from and got confirmed they soldered the pentode mode, for some reason. Gosh.
Think will bring back to fix it. And why the pentode, if any?

I also noticed that TU-8800 looks to allow UL or triode mode.
For my education, what does UL really do? Can it really blend the good from pentode and triode modes?
The Elekit manual just says it's meant to be an intermediate mode between the two other. And sonically, can one say UL is more close to either the pentode mode or the triode?

I enjoy writing irrelevant things in a thread it does not fit to.

Well I connected my Benz Ace MC via an all valve phono stage to the TU-8200. Wow. Welcome music.

Thanks a lot.

Sandor
I have had my Tu-8200 for several years now, I much prefer the Pentode mode and that's all I every use now. Considered soldering it in because the jumper seems so flimsy, but it works fine, so I left it adjustable. I have rolled many tubes (KT88, KT77, EL34, 6l6GC, KT66, 6550, 6ca7, 7581A). They all sound great to my ear. My favorites are the KT77, 6ca7, and what I'm stuck on now is the 7581A (6l6GC on steroids). Tube rolling is a blast, have fun!
 
Hi PaczeltF,

I noticed my TU-8200 has no jumpers inside that'd allow to change modes UL, triode and pentode. I asked the local shop I purchased from and got confirmed they soldered the pentode mode, for some reason. Gosh.
Think will bring back to fix it. And why the pentode, if any?

I also noticed that TU-8800 looks to allow UL or triode mode.
For my education, what does UL really do? Can it really blend the good from pentode and triode modes?
The Elekit manual just says it's meant to be an intermediate mode between the two other. And sonically, can one say UL is more close to either the pentode mode or the triode?

I enjoy writing irrelevant things in a thread it does not fit to.

Well I connected my Benz Ace MC via an all valve phono stage to the TU-8200. Wow. Welcome music.

Thanks a lot.

Sandor
I have had my Tu-8200 for several years now, I much prefer the Pentode mode and that's all I every use now. Considered soldering it in because the jumper seems so flimsy, but it works fine, so I left it adjustable. I have rolled many tubes (KT88, KT77, EL34, 6l6GC, KT66, 6550, 6ca7, 7581A). They all sound great to my ear. My favorites are the KT77, 6ca7, and what I'm stuck on now is the 7581A (6l6GC on steroids). Tube rolling is a blast, have fun!