TU-8200 Compatible Power Tubes

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, Thanks
Will play with the modes if I can. Saw adaptors on ebay that are said to convert a tube running in pentode mode to triode mode. Or just blows up the thing.

I guess you tweaked the amp to be able to use ecc83?
Far beyond my capabilities.
But I appreciate ecc83 tubes, running in my phono.


Hi Sandor,



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.



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".
 
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Hi Paczeltf, Thanks
Will play with the modes if I can. Saw adaptors on ebay that are said to convert a tube running in pentode mode to triode mode. Or just blows up the thing.

This type of adaptor may cause oscillations. I would skip on this.

I guess you tweaked the amp to be able to use ecc83?

Nope. Just read through the thread that I opened.
 
Thanks Paczeltf. I notice I missed a whole lot info I went through now a couple of times. I repect the knowledge and all experiment.

May I ask these for my understanding:

- What impedance range of a headphone you think fits, without the modification you suggest in your spreadsheet? Is that like 90 ohm plus, or even higher? My current headphone has 70 ohm nominal impedance. Thinking to buy a Senn HD 650 (300 ohms) at some point.
Btw have you received any inputs since, re weather the unit in TU 8200 R with adjutable headphone impedance is available separately thus can be installed for Tu 8200?
- Your mod of C22, does help to reduce hum for all headphones or just those above / outside the impedance range you determine in prior point?
- Your mods in the spreadsheet, can you think whether the different modes benefit differently from these? Or, all modifications are beneficial for the UL, triode and the pentode modes, too?
- Your mods in the spreadsheet, they are to do all or none, right (except the ones you indicate as are optional)?


Any advice or thought is appreciated.

Thanks
Sandor




This type of adaptor may cause oscillations. I would skip on this.



Nope. Just read through the thread that I opened.
 
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- What impedance range of a headphone you think fits, without the modification you suggest in your spreadsheet? Is that like 90 ohm plus, or even higher? My current headphone has 70 ohm nominal impedance. Thinking to buy a Senn HD 650 (300 ohms) at some point.

It depends on the phones. Some tolerate high output impedance, some don't. Focal Clear, for instance, do not, which is something I expected after reading the review in a well known magazine. High impedance Sennheisers usually like being driven like that.

Btw have you received any inputs since, re weather the unit in TU 8200 R with adjutable headphone impedance is available separately thus can be installed for Tu 8200?

Please ask Victor, but my understanding is that no upgrade kit is available.
Also note that even though the output level on the revised model is jumper-selectable, the output impedance is still high. (I explained this in another thread btw.)

- Your mod of C22, does help to reduce hum for all headphones or just those above / outside the impedance range you determine in prior point?

Any phones.

- Your mods in the spreadsheet, can you think whether the different modes benefit differently from these? Or, all modifications are beneficial for the UL, triode and the pentode modes, too?

The changes are irrespective of the chosen mode and all of them should benefit.

- Your mods in the spreadsheet, they are to do all or none, right (except the ones you indicate as are optional)?

C22 is the most important one especially in case of 50Hz mains frequency. D7/R64 are also mandatory if you want to try a driver tube with higher heater current.
 
Finally, got the adaptors for the 807, they sound fantastic with a Aikido (Broskie 6SN7) preamp and Altecs. Surprisingly quieter than the Mullard EL34s.

I hear the Haltron's are rebadged Brimar's, any idea ?
 

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I do not know.
As googled: Hytron Radio and Electronics was a Salem, Massachusetts based company that manufactured TV's as well as radio and TV tubes. It was purchased by CBS from 2 brothers, Bruce and Lloyd Coffin, when CBS tried it's hand at manufacturing (like RCA). The products Hytron produced were not "top line" and they shut down the TV manufacturing plant in Long Island City NY in July 1956. CBS/Hytron stop making tubes in 1961.
 
Hi, my experience:
I've been using NOS Philips QE06/50 (807) with great success, with Tungsram e80cc. To my ears, combines the clarity and transparency, linearity, dynamics by Tungsram with a more "classic" old school tube sound I associate with the Philips here.

I prefer this combo vs. Philips e80cc, Philips 807, sounding too sweet and a bit muddy to my ears, losing some details, losing some of the highs, and with looser bass; the lower midrange and upper bass however raised. Latter I may use with my 40 years old Stax Lambda, to dope these ranges but as I switch back to Tungsram e80cc, I miss little from the doping if any, but appreciate the full range presentation of Tungsram.

Tried NOS RCA 807 - just too bright for me, and feels like listening to a mosaic, not the whole thing. But the tubes need more time to break in possibly.
Tried Mullard NOS QE06/50 (807), a somewhat dark sound I got, but robust, will listen to it in 8-10 years (but before go back to RCA 807) and guess will open up, will enjoy in my old days :)
 
Old thread I know

I can’t get past a very strong buzzing when I fire up the 807 tubes with adapters on this tu 8200 amp, does amp need to have a certain setting to use them? Just wondering why everyone else gets to listen to these tubes and I don’t—buzzing stays strong so I just switched it back off, and went back to 6L6. Any ideas let me know
 
What happens if you put back the stock 6L6GC tubes? If buzzing does not disappear then the 807 or some other tube that you tried must be defective and killed the FETs in the power supply.
Never got to the bottom of it, 6l6 tubes played well. Resold the Raytheon 807tubes with my story. I couldn’t find anyone with a tube tester in my location. Never had the guts to try another 807 in it, but now I do again… due to the nice 807 prices. Wonder if the China made adapters had anything to do with it? Is there a known good adapter to buy?

Love this amp, too much fun with a pair of really old really big university speakers

Sorry for delay, got into the thick of it
 
Hi, my experience:
I've been using NOS Philips QE06/50 (807) with great success, with Tungsram e80cc. To my ears, combines the clarity and transparency, linearity, dynamics by Tungsram with a more "classic" old school tube sound I associate with the Philips here.

I prefer this combo vs. Philips e80cc, Philips 807, sounding too sweet and a bit muddy to my ears, losing some details, losing some of the highs, and with looser bass; the lower midrange and upper bass however raised. Latter I may use with my 40 years old Stax Lambda, to dope these ranges but as I switch back to Tungsram e80cc, I miss little from the doping if any, but appreciate the full range presentation of Tungsram.

Tried NOS RCA 807 - just too bright for me, and feels like listening to a mosaic, not the whole thing. But the tubes need more time to break in possibly.
Tried Mullard NOS QE06/50 (807), a somewhat dark sound I got, but robust, will listen to it in 8-10 years (but before go back to RCA 807) and guess will open up, will enjoy in my old days :)
Hello SandorS,

I also asked the question in the TU 8200R topic, but it seems more relevant here based on what I have read:

I am currently using Wenstinghouse 807 tubes.

At the 9 o'clock position of the volume control, my 89dB sensitivity monitors (Fyne F500) sound perfectly and with great sound (in fact, loud) in Pentode and UL mode.
There is no trace of the distortion, so much so that there is no audible distortion when the volume is turned up to 12 o'clock.(and the source is on max)

At the same time, when listening to these 807 tubes after switching to Triode mode, serious distortion is already experienced at the same 9 o'clock volume position.
Either I have to turn down the source or the amplifier itself.

I think several people have tried and like to use the 807 in their TU 8200 amplifier, so I would like to ask them if they have experienced something similar?


With other tubes, e.g. 6L6, 6550C I did not experience this distortion in the same conditions when switching between different modes (UL->Triode).
 
Hello gotan,

I have not experienced the symptoms you describe. Have been using 807s for like 2 years now, say an hour a day. Tried different produces.
My speakers are more sensitive on paper, 94 dB.

An idea, possibly it's the low wattage this amp provides in triode mode that you experience. Paczeltf calculated/measured and got like 1.4 watts or 1.9 watts as performance with reasonable distortion.

I really need to turn up the volume to 2 o' clock or above to hear disturbing distortion.

If I use a preamp or a source with a high output level, as the Elekit has high gain, the volume knob at 12 is that loud that my wife runs in to say turn it down. No distortion from the amp though.

Kind regards
Sandor
 
Hello Sándor,

thank you for your answer!
Since then, I have gained several experiences:

-the Westinghouse pair begins to distort roughly at the 10 o'clock position in SE mode.

Since then, I managed to acquire wonderful Tungsram black anode pieces (3 pieces) and a "pair" of them play music perfectly, without any distortion, in SE mode, even with an extreme volume level turned up to 12 hours.
At the same time, if I replace one of the pairs for the third piece, the distortion can already be heard around 9-10 o'clock.

I've also tried the Russian G-807s, I have two pairs, a '71 and a '78, both of which hum and hum in SE mode, while these tubes also sound absolutely flawless in UL mode, even loud!
So something is "wrong" with SE mode with 807 because only my Tungrams can jump.

In UL, they are all super good.
 
Hello Sándor,

you mentioned that you have been using the 807s for years, I read earlier that the Philips version is the "best" for you. How do you use them? (if I remember correctly, the jumper was soldered into UL or Pentode mode on your pcb "by default".)

Yesterday I tried all the Russian G-807 tubes again, and also the third Tungsram 807 in Triode mode. (again, all of tubes woriking well in UL or Pentode)
To my greatest surprise, none of them "buzzed" or hummed now. And they also played with more or less success in Trioda. The Russians started to distort audibly a little before 9 o'clock, the third piece of the Tungram is much closer to the other, approx. It held up to 10 o'clock, just like the Westinghouses without distortion.
My clear winners are the Tungsram 2 good valves, they hold up well in Triode too.