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Old 4th March 2020, 04:51 PM   #61
Spencer Brandsen is offline Spencer Brandsen  Netherlands
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Thanks a lot, Mr. Kung. : )
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Old 21st May 2020, 08:56 PM   #62
HarryY is offline HarryY  United States
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Some thoughts on Elekit TU-8200DX
This is one mod I would suggest that everyone do.

I have been very pleases with how much better my TU-8200 sounds now
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Old 28th May 2020, 03:13 PM   #63
Badchile is offline Badchile  United States
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I have to say the improvements by pazceltf are top notch and if you are considering implementing them, go ahead and do so as the difference is significant. In addition to the mods suggested in the spreadsheet, I also implemented a few other items on my two year old TU-8200.

1) Upgraded the stock volume pot to an Alps R27 50k. This is about a $20 change and well worth it over the stock volume pot, however, it does require cutting the board and wiring in eight jumpers. I used the cut leads from the coupling capacitor upgrade, which are fairly rigid and therefore difficult to get proper alignment (at least for me). Took a few hours to get everything lined up and installed, but again, worth it. If you do this, solder the 8 jumpers to the main part of Unit 3 first, then bend to insert the cut part that the volume pot solders to, then insert the volume pot onto its board, check the alignment with the face plate, then solder the board to the jumpers, recheck alignment, then solder the volume pot to the board, using this opportunity to make small alignment changes. The Alps pot has better channel balance and smoother operation and seemed to remove a veil over the sound.

2a) I upgraded all resistors except R43 and R44 to PRP9372 metal film at 50ppm, 1% tolerance. Did it help? I really felt like it did. Was it worth desoldering and re-soldering all resisters? Probably not. Did it give me something to do during the pandemic lockdown? Definitely.

2b) R43 and R44 got Jantzen Audio Superes 5W at 1% tolerance. Those are big resistors but will fit.

3) Replaced C17 and C18 (3300pF) in the negative feedback circuit with WIMA FKP 02 series film capacitors at 5% tolerance.

4) Replaced C19 and C20 (0.22uF) in the speaker impedance selection circuit with Vishay BC 2% tolerance MKP416 capacitors.

5) As Digikey was out of stock on 2.0A through-hole bridge rectifiers I installed a 1.5A (DB157) in place of the stock 1.0A DB107 at location D5. I also ordered a SMD DB207 and tried to bend pins and trim to make a through hole before giving up and dropping in the DB157.

6) I replaced the 1uF, 50V capacitors at C15, C16, and C21 with WIMA MKS 02 series film capacitors (10% tolerance).

7) The remaining 10uF, 400V capacitors not upgraded as part of paczeltf's recommended upgrades were replaced with the same series Nichicon capacitors but the 450V versions. These have a higher ESR, I tossed them in just as an experiment and didn't bother changing back. The original capacitors in that location are rated for 1000 hours so it might have been an improvement as my amp is over two years old and probably was close to 1000 hours.

8) Replaced C13 and C14 (along with C33, C34, and C35) with the same 220uF, 16V SEPC OS-CON aluminum poly caps as the DX upgrade. I did not do the increased capacitance of C13, C14, and C33 recommended by paczeltf as I was lazy.

9) Played around with Cerafines and Simlic II's (both from Elna) in a number of positions before settling on the OS-CONs or film capacitors listed above. I don't have any of the Cerafines or Simlic IIs in the amp currently.

10) I did not short R64, leaving in as the only original resistor in the amp for that very reason.

11) Pay attention to the physical space requirements listed by paczeltf. You are not going to mount a 30mm diameter capacitor at C22, and a 25mm diameter is a tight fit. Fun fact, though, you can use jumpers to mount a 30mm diameter cap at C22 and lay it on its side in the case if you really want to try a 470uF capacitor at that location. I can't tell the difference between 270uF/20% and 470uF/20% so I switched back to a board mounted 270uF.

12) Finally, I run JJ ECC802S variants of the 12AU7 tubes. I like these even more than a couple pairs of RCA cleartops I have sitting around. For power tubes I keep going back to the JJ 6L6GC.

13) I had the jumper soldered in on the ultralinear mode just for fun...and then took it out so I could swap modes easier. Don't bother with soldering in a jumper for the mode selection, I saw no change in the audio quality associated with the soldering.

So...at this point I'm pretty well set considering that between the resistors and capacitors there is exactly one original (R64).

What I would have done differently:

1) Not sure what I was thinking on C17 and C18 as I placed those going straight up, I should have bent the leads flat and laid those on their side given the width of R35 and R36. My bad.

2) Ordered the 330uF version of the capacitor for C22 instead of the 270uF. Per the above, a 30mm diameter capacitor will not fit.

3) I really liked the Cerafines in the locations I installed before I tried the OS-CONS or film caps, so if you have those sitting around give them a shot. The Simlic IIs were nice as well but are physically larger - if you go that route make sure you really seat them well.

4) Ordered the TU-8600S when it was available on pre-order. Not that I really need another amp, but I'm looking forward to another build. If I get one I'll probably replace most the stock parts in that amp too....

Last edited by Badchile; 28th May 2020 at 03:34 PM.
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