[harris4crna]

Where can I hear the BHSE? I am going to hold off for a bit. I will be here in Japan for another year. I am a little curious where the T8K goes from here.

 

[paradoxper]

Commission yourself a build. Be it a T8000DR or Carbon or Blue Hawaii or whatever.

I suppose as a commercial offering this is the second best deal around.

I also suppose that is some success conceding to the BHSE (a play on their T2 design) while beating out the competition.

 

[Ali-Pacha]

Looks like T8000 is voiced on the warm side...not surprising though :
- 717 as well as modded 727 are warm, and T8000 looks like a 727 (maybe with a bit more power ?) with tube preamp. BTW, stock 727 is so warm it has something (really) bloated in the bass, with kinda compressed dynamics / metallic tone in the high mids
- Lots of people consider 009 as bright cans...so good idea to deal with this issue through amping

From my point of view, 009 may easily sound bright :
- they have something energetic around 1-2 khz that lots of people may dislike, even when most of them "tolerate" something brighter to my ears but with a peak higher in frequency (HD800, Utopia, Beyer, ortho with "treble wall", etc...)
- from lower Stax SS amps (under 717/727), 009 may sound bright because these amps keep a slight metallic tone without the warmth of 717/727. An they don't have the control to tame the energy around 1-2 khz. 009 are close to the old Lambda Signature in that extent, but not as harsh as x0x Lambdas. OTH, Stax tube amps are well liked with 009 by people who don't care that much about dynamics / impact
- from BHSE with stock tubes (Mullard re-issue and Shuguang Treasures), you have terrific control, impactful bass and dynamics, but something a bit thin in this extreme openness with 009, like a vasoconstrictor for ears. NOS tubes were discussed, but Mesa Boogie STR447 are also a great choice to give some melowness, moar bass, and still keeping the openness of the BHSE. 007 lovers may obviously have kinda different opinion.

I think SR-L700 are the "best" voicing today, the kind of signature Stax wants for their house-sound (even if ol' zealots are grumpy through "before was better" motto) and that pleases most of headphones hobbyists today.

2 cents

Ali

 

[kevin gilmore]

t8000 brand new in the box never opened has arrived.

special security screws on the top, ultra miniature metric 6 sided spline

relatively easy to convert voltages once you get rid of the goop

forum won't let me upload pictures, probably due to the size, pictures posted elsewhere.

very hard to tube roll due to limited servo range

power supplies are +/-350v, so same as T1,717,727,007t,006t etc

higher output stage bias current, about 10ma

 

[catscratch]

I like the voicing of the L700, save for the bump at 1-2khz. I guess that's what audiophiles call an "ah" coloration, and it sticks out a little bit. Not too badly though. The bass could use more extension and less mid/upper bass emphasis but again it's not bad.

On the (off)topic of the 717 - how does the 009 do with the 717? I agree about the 717's warmth, though there's also a slight edge to its highs that better amps don't have. But heretical thoughts have entered into my mind after owning and liking the L700 (maybe even as much as the 007!), so I have to tentatively inquire about the 009 and whether it will (gasp) fit into my current rig.

T8000 seems interesting but at that much of an investment I'd probably just try to build a GG or KGSSHV Carbon and try not to electrocute myself in the process.

 

[Whitigir]

I like the voicing of the L700, save for the bump at 1-2khz. I guess that's what audiophiles call an "ah" coloration, and it sticks out a little bit. Not too badly though. The bass could use more extension and less mid/upper bass emphasis but again it's not bad.

On the (off)topic of the 717 - how does the 009 do with the 717? I agree about the 717's warmth, though there's also a slight edge to its highs that better amps don't have. But heretical thoughts have entered into my mind after owning and liking the L700 (maybe even as much as the 007!), so I have to tentatively inquire about the 009 and whether it will (gasp) fit into my current rig.

T8000 seems interesting but at that much of an investment I'd probably just try to build a GG or KGSSHV Carbon and try not to electrocute myself in the process.

To build your own Carbon or GG is a much much better choice

 

[JimL11]

Preliminary schematic of T8000, courtesy of Kevin Gilmore.

 

[JimL11]

second try.

 

[Whitigir]

Here, I will help you, and unless KG notify me to take it off, otherwise it will stay
KG mentioned that resistors are in the wrong values and he will correct it later

Again, courtesy of Kevin Gilmore findings. All thanks to KG

*update* please refer to this post for newest scheme
https://www.head-fi.org/f/threads/i...t8000-head-fi-tv.845544/page-10#post-13586003

 

[JimL11]

OK, well it doesn't seem to allow me to do it. Preliminary circuit analysis, 6DJ8 input diff amp with current source on the tail for improved AC balance, intermediate section similar topology to all the Stax amps since the T1, driver appears to be cascoded diff amp, however with resistor loads (similar to the SRM717) instead of current source loads as used in the SRM727, into output stage, which consists of Darlington pair emitter followers into Darlington pair current source load. There is overall negative feedback back to the input - R40-43, unlike the SRM-727.

 

[JimL11]

Thanks, Whitigir.

 

[kevin gilmore]

I upgraded the schematic, posted over there. The front end runs at +100v, not a shunt supply.

dishwasher went nuclear for the 5th time in 5 years, and is now in the trash, never buy kitchenaid again, whirlpool sucks.
now back to our regularly scheduled reverse engineering program.

I did get to listen to the amp for several hours last night.

first, its dead silent, probably due to DC filaments and carefully selected tubes.
a T2 this is definitely NOT. its a bit warmer than the 717, but very high frequencys still a bit rough.
it is built nice, definitely in the style of stax of the past. Thick thermal washers and thermal design in general far superior
to the original T2 and 727. you pretty much have to build it this way if you are going to use power surface mount parts.

the expansion slot is stupid, no decent r2r dac is ever going to fit in that slot. a phono preamp would work.

completely silent torroid transformer is an about time addition.

high voltage power supply is not regulated.

no cut wires on the transformer, so universal voltage is relatively easy.

tube rolling is a bad idea, and there are 4 adjustments per channel, servo is tricky.
6922 tubes ONLY! and the best idea would be to match them on a quality tube tester especially section to section.
and burning in the tubes on a test fixture a really good idea. Not sure if the circuitry especially the current source at the
top of the tubes can handle a tube short.

6922 runs at about 90V, it would be more linear at twice that voltage but then a number of the other parts have to change due to increased power requirements.

 

[Whitigir]

Updated T8k Scheme from Kg

 

[JimL11]

tube rolling is a bad idea, and there are 4 adjustments per channel, servo is tricky.
6922 tubes ONLY! and the best idea would be to match them on a quality tube tester especially section to section.
and burning in the tubes on a test fixture a really good idea. Not sure if the circuitry especially the current source at the
top of the tubes can handle a tube short.

So, no user serviceable parts.

 

[paulchiu]

Are you certain you cannot roll the T8000 pre amp tubes?

So, no user serviceable parts.