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Stax SRM-T8000

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14 hours ago, justin said:

I would consider the SRM-353X instead of those

Although if @zoide has single-ended sources I'm not sure there is any advantage to the 353 over the 323, other than that new amplifier smell. 😀

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5 hours ago, JimL said:

Although if @zoide has single-ended sources I'm not sure there is any advantage to the 353 over the 323, other than that new amplifier smell. 😀

Justin told me that the 353X is a re-worked SRM717, so it should sound very decent right?  

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The circuitry is similar (as with the D-50) but Stax always fucks with it in some way.  The 717 was too warm for its own good and the 353X is a bit too bright for me.  Easy to fix but outside the scope for most people. 

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2 hours ago, purk said:

Justin told me that the 353X is a re-worked SRM717, so it should sound very decent right?  

Ah, did not realize that, thought the 323 and 353 had similar circuits. Oh, well, live and learn.

1 hour ago, spritzer said:

The circuitry is similar (as with the D-50) but Stax always fucks with it in some way.  The 717 was too warm for its own good and the 353X is a bit too bright for me.  Easy to fix but outside the scope for most people. 

Is this a biasing issue?

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At its core, yes.  They are running at much lower power with those tiny TO220 heatsinks and to be honest...pretty bad output transistors.  KSC5502's with Cob of 20pf.  Long gone are the days of 2.2pf... 

Stax also just fucks with the circuits for some reason.  I once did a board for the 323S and just tweaked the circuit a little bit but with massive changes to the better. 

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The 323 had a p-channel jfet as the input, +/-350v power supplies, 2sa1968 as the current source for the drivers etc.

The 353 is a srm717 with all of the extra transistors removed. Very similar to kgss. D50 is identical to 353 running at slightly lower power and lower voltage. Current source is resistors on both.

T8000 also uses resistors for the current source.

seems that stax has run out of 2sa1968.

d10 uses apex opamps with a power supply of +/-175, not great for large voltage swings.

stax may be forced into using parts in the future that it does not want to use for some reason.

Edited by kevin gilmore
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Wait, so the top-of-the-line T8000 uses a cheap tail resistor on the input instead of a current source? Are they at least running it from B- to make it as big as possible? Are they also using resistors instead of current sources elsewhere in the circuit? I think I'll stick with my old T1 with CCS output loads.

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guess you did not look at the schematics. i'm talking about the current sources at the top of the gain stage before the output stage.

main difference between 717 and 727 was 2sa1968 current sources (and local vs global feedback)

srm353, T8000,D50 are back to being all resistors.

and the german copy of the srm323 also uses resistors because of the 400v power supplies.

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Wow, I'm still trying to wrap my head around all of this.

Right now I'm assuming that the SRM-252S won't do justice to the SR-L700, so I'm considering the following:

1) SRM-323S (would hope to win an auction that ends tomorrow for at most 450 euros)

2) SRM-353X (could get a demo model for 800 euros)

3) SRM-600 Limited (a friend is asking his friend if he can sell it to me for a good price... no idea yet)

If you were in my place, what would you do? :)

Thanks

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11 minutes ago, Pars said:

Build a Carbon... done.

I have neither the money nor the skills to build a Carbon.

That is why I am asking for advice to choose among the SRM-323S, SRM-353X, and SRM-600 Limited (or some other reasonable option I haven't considered).

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4 hours ago, Mach3 said:

SRM-600 Limited would be my pick. SRM-353X is too lean sounding.

Unfortunately, the SRM-600 Limited that I was considering already got sold.

It's interesting that don't find the SRM-353X appropriate, since it's often recommended (though very expensive).

What about the cheaper SRM-323S? Is it really just an SRM-353X with unbalanced inputs (soundwise)?

Thanks

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On 10/18/2018 at 12:06 PM, kevin gilmore said:

guess you did not look at the schematics. i'm talking about the current sources at the top of the gain stage before the output stage.

main difference between 717 and 727 was 2sa1968 current sources (and local vs global feedback)

srm353, T8000,D50 are back to being all resistors.

and the german copy of the srm323 also uses resistors because of the 400v power supplies.

Actually, I did a long time ago and commented on that, but totally forgot, my bad. By the German copy of the SRM323 are you referring to the Highend Amp Sirius by chance?

6 hours ago, Zoide said:

Unfortunately, the SRM-600 Limited that I was considering already got sold.

It's interesting that don't find the SRM-353X appropriate, since it's often recommended (though very expensive).

What about the cheaper SRM-323S? Is it really just an SRM-353X with unbalanced inputs (soundwise)?

Thanks

You could also consider the SRM-T1 series, which many people think is a nice match for any Lambda series phone - although they are old enough to need replacement of electrolytic caps, which you can do yourself if you know how to desolder and solder, or any electronics technician should be able to do it for you if you don't. The SRM006T is basically the updated T1 series, although I have seen a couple comments that the T1 sounds a bit better.  See comments further up the page about the difference between the SRM 323 and 353.

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40 minutes ago, JimL said:

You could also consider the SRM-T1 series, which many people think is a nice match for any Lambda series phone - although they are old enough to need replacement of electrolytic caps, which you can do yourself if you know how to desolder and solder, or any electronics technician should be able to do it for you if you don't. The SRM006T is basically the updated T1 series, although I have seen a couple comments that the T1 sounds a bit better.  See comments further up the page about the difference between the SRM 323 and 353.

Thanks for the advice! I really appreciate your patience with my questions as this forum doesn't seem to be very beginner-friendly (e.g., https://www.head-case.org/forums/topic/11746-stax-srm-006t-plus-kimik-or-new-srm-323s/).

As you mentioned, the T1 is very old, and I'd rather not have to mess with recapping and such. I did find a used SRM-006T for 675, which sounds tempting, but after reading about the dangers of electrocution while rebiasing tube amps, etc. I think I better stick with solid state ':D

I'll probably go for a ~ 450 bid on a used SRM-323S auction that ends today. Other than that, the cheapest SRM-353X I've found is an 800 demo model that would seriously stretch my budget.

EDIT: I just realized my posts in this thread have been very off-topic. To link them back to the thread: I'd love to get the T-8000, but I find it totally unaffordable, and probably overkill for the SR-L700 anyway.

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6 minutes ago, Zoide said:

Thanks for the advice! I really appreciate your patience with my questions as this forum doesn't seem to be very beginner-friendly (e.g., https://www.head-case.org/forums/topic/11746-stax-srm-006t-plus-kimik-or-new-srm-323s/).

It's not and not designed or intended to be so.  If you find that's not for you, that's ok.  If you decide to stick around I'd recommend growing some thicker skin and taking stock of where you are.  If you want audio advice this probably isn't the place to look.  Just being honest.

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Just now, n_maher said:

It's not and not designed or intended to be so.  If you find that's not for you, that's ok.  If you decide to stick around I'd recommend growing some thicker skin and taking stock of where you are.  If you want audio advice this probably isn't the place to look.  Just being honest.

I didn't know that, thanks for the explanation. I'll lurk here and post somewhere else.

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Lets bring the discussion back on topic.

I tried a demo unit of T8000 in a headphone store in Jakarta. I am surprised that they have one as demo unit because to be honest not too many people could afford one around here. They also have L700, 007 and 009 as demo units. No 009S yet. Maybe next year.

Sound-wise..  I couldn't really describe it but to me it sounds plain. I tried it mostly with a 007, and I expect more from the current top of the line Stax amplifier. I expected it to be somewhat close to what we get from Dr Gilmore's designed amps. I still can't grasp what's stopping Stax from selling an amp with the same level of performance as Hawaiis or Carbons.

 

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It is a very different animal to design something with whatever parts we want or making something in the hundreds or thousands with a reliable supply of parts.  That being said, Stax does do a lot of stupid shit and they seem to be getting worse.  Bad decisions galore and with the new stuff made in China, assembly has gone down the drain. 

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