The Stax Thread III

[JimL11]

I can't compare but per dollar people really like the t1. If you want to get the most value buy one that needs to be recapped and do jiml s ccs mod at the same time.

Actually, a lot of people like the unmodified T1 for the Lambda series headphones, but they are old enough (mid-1990s or before) that they all probably need to be recapped for best reliability. My sample had GE tubes (probably original) and they were still tested good so tubes last a long time with those amps. The CCS mod makes it even better but it where it really makes a difference is with the harder to drive Stax phones like the SR007. In fact I prefer the CCS modded T1 to an SRM727 with global feedback mod that I had at the same time. I sold that, but still have the T1. However, note that I prefer tubes to solid state for electrostatic headphones and speakers

 

[SeaWo|f]

Yea that's very true the unmodified t1 is good for L series.

I was thinking of ccs as a while your in there sort of thing. Then it's done if you upgrade to omega series or added value if you sell for a different amp.

 

[Zoide]

There's an SRM-3 I could get at a good price for my upcoming L700, but it's had several owners and the only thing the seller knows is that it's at most 24 years old...

I'm guessing I should hold off and look for something recapped (or perhaps even settle for a cheap used SRM-252S)?

Thanks

 

[batfier]

I looked at the Highend Amp website, which includes schematics of their designs. They do have an advantage over the Stax amps in that they include a regulated power supply, however, the Alpha Centauri amp uses resistor loaded output stages, similar to the Stax SRM-T1, which means that a lot of their output power is burned up in the resistors. The KGST, which would be the equivalent of the Alpha Centauri, uses the more powerful 6S4A output tubes, but also uses constant current loads which burn up essentially no signal current, which more than doubles their effective power compared to plate resistor loads. To get some idea of the subjective effect of this circuit change, look at spritzer's comments about what a similar modification did to the sound of the Stax T1. The KGST also uses a regulated power supply.

The Canopus and Capella designs suffer from the same defect as the Alpha Centauri - they use tube amplification throughout but also have plate resistor outputs. By comparison, the SRX Plus, based on a 1968 Stax DIY circuit, also uses tube amplification throughout but uses constant current output loads which results in it having more effective output power despite using the less powerful 6SN7GTA/B output tubes.

The new Inexxon Sirius High Precision Amp meant by karlgerman is "Fully symmetrically constructed purely transistor-based DC amplifier" https://www.inexxon.com/online-shop/inexxon-sirius-verstärker-amp/, so no tubes at all.

Not sure, but because of the name, it might be based on the orginial Sirius design http://www.high-amp.de/html/transistor_v4_eng.html

At least it looks well made.

 

[JimL11]

The new Inexxon Sirius High Precision Amp meant by karlgerman is "Fully symmetrically constructed purely transistor-based DC amplifier" https://www.inexxon.com/online-shop/inexxon-sirius-verstärker-amp/, so no tubes at all.

Not sure, but because of the name, it might be based on the orginial Sirius design http://www.high-amp.de/html/transistor_v4_eng.html

At least it looks well made.

Can't really tell from the Inexxon website whether that is the same design as the high-amp Sirius design. The High-Amp design looks OK - all balanced differential stages with constant current (CC) output loads, although the circuit description is wrong in saying the output impedance is very high because of the CC loads. In fact the output impedance is determined by the emitter followers in the outputs, which have a low impedance. However, it lacks the 5.1 kilohm output safety resistors which Stax uses in all their recent amps (as do all the Gilmore amps, and the SRX Plus), so this is a negative in my opinion. I find it curious that the high-amp Alpha Centauri amp doesn't use the same constant current output loads that the Sirius has - the AC is already a hybrid design so it's not as if there aren't solid state elements in it already, and the use of CC loads would more than double its effective power output while decreasing distortion at the same time.

The other issue with the Alpha Centauri is that the output tubes are run at 400 volts and 5.3 watts plate dissipation per tube. However, the standard 6SN7GT tubes have maximum plate voltage ratings of 300 volts ,and maximum plate dissipation of 5 watts per tube. That means the output tubes MUST be 6SN7GTA or GTB, which have higher voltage and wattage ratings (450 volts and 7.5 watts total plate dissipation). Using non-A or B tubes as outputs is just asking for trouble.

Finally, the V5 power supply does have a 5 megohm safety resistor on the bias supply (good) but it uses an un-necessarily large final capacitor of 1 uf, in contrast to the 0.1 uf capacitor in the Stax and Gilmore bias supplies.

 

[JimL11]

A correction to a previous post, apparently the SRM-353X circuit resembles the SRM-717 rather than the SRM323. However, according to spritzer, the 353 is on the bright side, whereas the 717 was on the warm side.

 

[Pahani]

How do the SRM-252S and SRM-353X compare to older amps such as the SRM-1 Mk2, SRM-3, and SRM-323S?

I'm looking for an amp to pair with SR-L700s.

Thanks

I'm fortunate to own 252S, SRM-1 Mk2, and 353X presently. Paired with my L700.

SRM-1 is a noticeable increase in detail over 252S, but (at least my example) sounds a touch bright to my ears. Now, would you notice it if you didn't have other amps to compare it to? I'm guessing not.
353X retains the detail increase over the 252S, but sounds richer and fuller to me compared to SRM-1. I'm not a critical listener in any way, so can't elaborate more than that.

Hope this helps!

 

[Zoide]

I'm fortunate to own 252S, SRM-1 Mk2, and 353X presently. Paired with my L700.

SRM-1 is a noticeable increase in detail over 252S, but (at least my example) sounds a touch bright to my ears. Now, would you notice it if you didn't have other amps to compare it to? I'm guessing not.
353X retains the detail increase over the 252S, but sounds richer and fuller to me compared to SRM-1. I'm not a critical listener in any way, so can't elaborate more than that.

Hope this helps!

It does help, thanks!

I'm close to pulling the trigger on a used SRM-353X (demo model). It better be worth the 2X cost versus the SRM-252S though, because what started as a potential ~600 euro adventure (buying a used L300 + 252S) is potentially turning into a 1800 euro financial craziness (used L700 + used 353X) :O

 

[JimL11]

Whoops, another correction, meant to say that spritzer thinks the 353 (not the 323) is on the bright side. Sorry about that.

 

[Zoide]

Whoops, another correction, meant to say that spritzer thinks the 353 (not the 323) is on the bright side. Sorry about that.

LOL make up your mind, man!

 

[Hubert481]

Whoops, another correction, meant to say that spritzer thinks the 353 (not the 323) is on the bright side. Sorry about that.

Could you give a link therefore - thanks

 

[JimL11]

LOL make up your mind, man!

No change of mind, just a simple typo.

Could you give a link therefore - thanks

PM sent.

 

[gtrx333]

Hi, just acquired a user srs-005smk2 set. I have a question about powering the energiser. I am in the UK and have realised he power adapter for this is 100v outputting to 12v 500ma dc. Now can I use a 12w 4a adapter from 220v?

 

[Eich1eeF]

Hi, just acquired a user srs-005smk2 set. I have a question about powering the energiser. I am in the UK and have realised he power adapter for this is 100v outputting to 12v 500ma dc. Now can I use a 12w 4a adapter from 220v?

Theoretically, you could, but STAX power supplies have positive on the outside of the plug, which is rather unusual. Thus you may have to cut and re-solder the plug. Also, if your power supply is unregulated, it may output a somewhat higher voltage when not sufficiently loaded.

 

[gtrx333]

Thanks for the reply. Sounds too risky to me. I'll look into getting a step down transformer