Elekit TU-8200R amplifier - anybody built or heard one?

[Gruesome]

PSA: When using the headphone output of the TU-8200R for test signal output, it's important to keep track of the power dumped into the 3.3 Ohm 1/2 W resistors that make up the headphone shunt. The amp can produce more than the 2 W per channel (into 13.2 Ohm) that these resistors can take.

 

[Gruesome]

First attempt to measure signals from the TU-8200R with my Analog Discovery 2 USB scope and waveform generator.
1 kHz 100 mV amplitude in, 4 V amplitude out at speaker terminal (amp set to ultralinear mode, output switch to low impedance, terminated into 8 Ohm 50 W resistor). This is with the 8200R volume turned all the way up. So the maximum gain is 32 dB. Output power is 1 W [(4/sqrt2)^2/8= 8/8 = 1 ].

From earlier measurements with the Focusrite Scarlett Solo I know we should see several percent of harmonics, with the third dominating.
FFT of the right channel speaker output and 6L6GC tube grid shows this:

The output looks as expected, but the 2nd dominates at the grid.
Apparently either the 6L6GC or the output transformer makes some of the second harmonic disappear, and adds just a little bit of third.

 

[Jim Creek]

Remember, when assembling this kit always wear pants when soldering.

 

[knave101]

I own two of the TU-8200 dx. The first one I upgraded several capacitors, but couldn't tell any difference. The second I got has Lundhahl transformers. I love them both and use them for my Recording studio to drive small studio monitors and my mastering headphones. I love these amps. To be honest I really can't tell a difference between the stock output transformers and the Lundahl. I also have upgraded the tubes in one to vintage RCA 6L6 and clear top RCA 12au7. Again, I can't tell the difference between those and the stock EH tubes.

I have multiple vintage tube amps...several upgraded Dynaco ST-70, and several Heathkits (W5M, AA10, and UA-2), all with upgraded capacitors. Again, the TU-8200 beats them all for ease of use, and sound. Plus, it operates at multiple input voltages (you have to re-solder). Love these!

 

[Gruesome]

Thanks, Knave, very interesting about the inaudible differences! I got the Lundahls, but I have no idea what the standard transformers sound or measure like. Apparently I can hear sub-percent addition of harmonics in a single sine wave, but with music I seem to need more before it becomes really noticeable, at least according to the PKharmonics audio plugin.
One of these days I will start measuring again, the scope hookup loops are still soldered to my TU-8200R...

 

[knave101]

Interesting Gruesome. It is possible they’re different sounding. But not enough for me to worry about. 35 years ago I started collecting tubes and have tons to choose from. I’ve never found a difference enough to make me think that I need to pay a 300 for an an old 12ax7. I use the telefunken and amperex in my top amps, just to use them before it’s time for me to say adios.

Another problem with old amps is the modern wall voltage is too much for them. Such that I have them all running on bucking transformers. None is more sensitive to voltage than the W5M. Wall voltage is way too much for that amp and the voltages exceed my EL cap ratings.

If I were to say which amp is a close second to the tu-8200. I’d say the HealthKit UA-2. But the headphone Jack on the 8200 is why I need it. I do most mixing and setup via headphone prior to final mix. My headphones are stellar.:..beyerdynamic DT 1990 pro open back mastering phones. These truly show the wonder of the 8200 amp

 

[Gruesome]

The only tube I owned before buying this kit was an old photomultiplier tube.
I agree regarding the usefulness and implementation neatness of the headphone output with the four 1/2 Watt 3.3 Ohm resistors hanging from the main output. If there is a special 'sound'/coloration/distortion deficiency to the TU-8200R, be it from the main tubes or the output transformer, or the interaction of the two, the headphone output should preserve it.
I upgraded mine to 1 Watt resistors, after crisping up the 1/2 Watt ones while measuring distortion at higher power levels.

Another general question about the 8200(R): has anybody created a Spice simulation model for this amplifier?

 

[snaimpally]

I bought a used (pre-built) 8500 preamp as a front end for my Buckeye amp and am thinking of getting the 8200. Elekit states that the frequency response is 12Hz - 50kHz (-3dB). Ken Rockwell measured frequency response as half a db down at 16 Hz and at 20 kHz. Those are pretty good numbers and show it is well designed.

 

[EVDavis]

VK displaying his wares, circa 2017. I think he knows at least three languages.
View attachment 286649

Hey, I'll bet that is my preamp. The actual preamp. He was nice to me and sold me a few of his older well used items he was not using at his shows anymore several years back. Very nice man.

 

[EVDavis]

I built the TU-8500 preamp and enjoy it. I would love to see Amir test it, but I don't want to mail it.

I find the phono stage isn't to my liking but the rest of it is fine.

 

[Ricardus]

I find the phono stage isn't to my liking but the rest of it is fine.

I'm building an ESP06 in case I want a different flavor.

 

[JeffS7444]

I upgraded mine to 1 Watt resistors, after crisping up the 1/2 Watt ones while measuring distortion at higher power levels.

Better that those resistors should burn, rather than the voice coils of your headphones! This might be a good application for carbon-film resistors.