Elekit TU-879S Stereo Tube Amplifier Kit

[hilldweller]

https://tubedepot.com/products/elekit-t ... lifier-kit

Any thoughts or similarities? Looks Clementineish ?
Soon to be gone!

[DeathRex]

Would like to know what the output transformer is.

[EWBrown]

OPTs look small and cheap,

[TomMcNally]

Nice looking little amp, not sure it's worth $ 600.

Words of wisdom from the manual !

Vacuum tubes are made of glass. Please handle with care. A metallic black haze visible in the inner wall of the glass indicates it is a sealed vacuum tube. If this turns white, the vacuum has leaked and can no longer be used. All vacuum tubes have been examined to ensure quality. Some may have a minor scratch that does not affect the function of the tube.

[Geek]

Nice looking little amp, not sure it's worth $ 600.

Got one on the bench right now getting un-fubared from a few mis-wirings... no, it is not IMO worth $600 unless they are assembled and tested.

Cheers!

[dcriner]

Seems that most everything is to be mounted on printed ckt boards. Solid-state power supply.

The power rating is just 8.5W per channel, which maybe explains the small output xfmrs?

[Geek]

The power rating is just 8.5W per channel, which maybe explains the small output xfmrs?

That's in pentode mode. A 6L6 in triode does about 1.5W. And regardless of output, DC bias is DC bias on the iron as it's class-A.

When I fix it, I'm going to spec it and see what it does.

[EWBrown]

FWIW the power transformer HV secondary is 260VAC, which is then rectified through a 4-diode FWB, generating B+ of approximately 325VDC.

They were selling the original Japanese R-core power transformers for these amps, at a fairly low price, it has a 100VAC primary, but it will operate very nicely under full rated current load with 120VAC powerline input, and the 6.3VAC filament winding will output 7.5VAC, and the HV winding 312 VAC. I ran it fully loaded for several hours, and the tranny barely got warm.
(I bought four of them, at the time, and posted testing results about these trannies, about 9 months ago).

They are still available: https://tubedepot.com/products/r-core-2 ... ransformer



FWB Rectify the filament and it will deliver close to 8VDC, which would work very nicely with 8BQ5s and 8CG7s, 8FQ7s or 8GU7s, for a nice SE amp, or a single PP monoblock.

PDF file describes this trannie: https://d1sjrnpi226dnf.cloudfront.net/s ... 1382030195

My earlier posting, copied from the ZeeBee posting of Fri Apr 26, 2013 3:19 pm

viewtopic.php?f=19&t=4999&hilit=877

The R-Core power trannie looks similar to the PT-877 which was on sale from Tube Depot a few months ago, which has 6.3VAC @ 3A and 260VAC @ 200 mA
secondaries, and 100VAC primary. (these were intended for use in Japan, where 100VAC is a normal line voltage)

They tested it with 120VAC on the primary, and got 7.56VAC and 312 VAC, loaded at the rated currents.
I bought four of them (they were cheap) and used a tapped autotransformer to test one at 100VAC,
and loaded the 260VAC winding with a 40W, 230V light bulb (about 180 mA at 260VAC), and the 6.3 VAC winding with a 6AS7 filament(2.5A)
the transformer just barely got warm, even after several hours' continuous operation.

I figured, use it on 120VAC with 8BQ5s and 8CG7s (or 8SN7), in a modified Clementine or Budgie SE design. The filament voltage might be a tad(about 5%) low,
but it is still within operating specs for these "series filament" tubes... 8SN7s do exist, though they are not really "common", I have a few "Zenith" branded ones.
Lower gain then the original 12AX7 / ECC83s, but then, that's what preamps or line stages are for

[Geek]

You can squeak a little more voltage out of the filament winding by using low drop schottky rectifiers to give you 8V.

And if you want to play with minature pre tubes, you can series 4EJ7, 4CB6, 4AU6, etc.

I love R-cores and if the Int'l Priority shipping didn't double the price of the thing, I'd grab a bunch.

Cheers!

[EWBrown]

Also the compactron duodecars 4HA7 and 4HC7, basically a 4.2V version of half a 12AX7 and half a 12AU7. Or at least pretty darn close...

/ed B

[Geek]

Whelp, fixed the TU-879S and I'm listening to it now.

Colour me surprised!

4.5W/channel from 20Hz to 45KHz (-3dB) before compression/clipping.

A very nice multimedia/personal amp for beside your computer or for making a headphone adapter for.

Sounds on par with low-NFB 6L6 amps, but it's not fatiguing like most. Neutral on the mids with reserved highs. Bass is a little floppy, but whaddya expect from a teeny cathode and high Rp of a 6L6 and low NFB (no, I didn't meadure the decibels and don't want to take the dang thing apart again, LOL!)

Cheers!

[EWBrown]

A glimpse inside this amplifier:

http://www.vkmusic.ca/TU-879S_point.htm