[Muffinhead]

The stock T1 is indeed marginal for the SR007 (although Ken Kessler at Hi FI News reviewed the SR007 with both the T1 and the 007t), but that has more to do with the design of the output stage than its intrinsic power. As @Muffinhead has found, the modded T1 with constant current output loads does a significantly better job of driving the SR007, even though it has EXACTLY the same standing output current/power as the stock design.

Is it as good as a KGSSHV/KGST level amp? No, but it gets you a good part of the way there.

I have wondered. % wise how does the modded T1 stack up against the competition?

 

[JimL11]

I have wondered. % wise how does the modded T1 stack up against the competition?

There are very few modded T1's out there for comparison as far as I know. I haven't formally compared it to anything but it doesn't match a KGST or BHSE although it wasn't embarrassed by them either.

 

[Sorrodje]

@JimL11 and what about SRX+ vs modded SRM-T1 ?

 

[astrostar59]

There are very few modded T1's out there for comparison as far as I know. I haven't formally compared it to anything but it doesn't match a KGST or BHSE although it wasn't embarrassed by them either.

I can't vouch for the old T1 modded, what / how much was it modded? But I can say my SRM-717 was WAY WAY behind the KGSShv, and later even more so v the Carbon or BHSE IMO, on both the 007s and the 009s. The SRM-007 did not seem as good as the 717 either, midrange ok, but outside of that mid band was weak and off the mark. I lost interest in Stax amps beyond that point, though admit is was on bog standard Stax amps, not modded units. Sorry, I don't want to dampened Stax amps, but if possible I would major on the KG DIY units if possible, used or from a decent builder. On the smaller Stax HPs maybe not as critical, though I have heard good things about the L700 on the Carbon.....

 

[JimL11]

A friend compared the modded T1 and SRX-Plus with a maxed out KGST (GRHV supply and Belleson LV regs), using SR007 MK 2.9 with port mod. He felt the T1 had a slightly U-shaped response compared to the KGST and SRX Plus. The latter two were very close with the SRX Plus sounding slightly more liquid.

 

[astrostar59]

Interesting info JimL11.
Have you any pics of the modded unit?

My findings on the 2 Stax amps were everything sounded thin and harsh, the bass was lumpy and slow, the treble edgy and false sounding. The 727 also clearly ran out of current mighty quick as at loud listening (not crazy, just bit louder than relaxed level) the signature changed and sounded tipped up on my 007 MK2s. So maybe the T1 modded has more current, better output stage, more of everything required to sound that much better than the later Stax amps? But if we go that modded, what not just get a KG amp and have done with it.

 

[statfi]

There are very few modded T1's out there for comparison

Muffinhead, Congratulations on the successful completion of an epic journey. I still have the T1 that my BHSE replaced in my system. Is there a single document that describes the upgrade, should I decide to execute it?

 

[Muffinhead]

Muffinhead, Congratulations on the successful completion of an epic journey. I still have the T1 that my BHSE replaced in my system. Is there a single document that describes the upgrade, should I decide to execute it?

Yes, there's an article in audioxpress that details the upgrade. You can purchase it for $10 or so. If you're not skilled at DIY like me, rhe upgrade can take a while to do. It took me a full month, but YMMV. Ask JimL11 more about it cuz it's his mod.

 

[JimL11]

Interesting info JimL11.
Have you any pics of the modded unit?

My findings on the 2 Stax amps were everything sounded thin and harsh, the bass was lumpy and slow, the treble edgy and false sounding. The 727 also clearly ran out of current mighty quick as at loud listening (not crazy, just bit louder than relaxed level) the signature changed and sounded tipped up on my 007 MK2s. So maybe the T1 modded has more current, better output stage, more of everything required to sound that much better than the later Stax amps? But if we go that modded, what not just get a KG amp and have done with it.

The stock T1 has output resistor loads, so by Ohm's law, for every signal voltage, you have a corresponding signal current that has to go to the resistor. The mod consists of replacing the resistor loads by constant current loads. This relieves the output tubes of having to burn up signal current in the resistors, so 99+% of the current is available for the feedback resistors and the headphones. Among other things, this increases the maximum voltage drive to the same as the Stax solid state amps.

The T1 actually has less standing current than the Stax solid state amps, which also have constant current loads, but those loads are less efficient, so do burn up some signal current. With the stock 727, you are also hearing the deleterious effects of the lack of global feedback.

The KG amps have the same design constant current loads as the T1 mod, but use higher standing currents and also have regulated power supplies, so they are superior in design. A modded T1 is most similar to a KGDT without PS regulation, which is just a KGST but using 6CG7 tubes instead of 6S4A tubes.

The primary advantage of the T1 mod is cost - a used T1 runs in the $400-700 range, and parts cost for the mod (and capacitor replacement) is around $100, plus it is easier to build than a complete DIY KG amp. And of course a fully built KG amp is more expensive than a DIY. So if someone wants to have an SR007 based system on a budget and is willing/able to do some DIY work, a modded T1 could be the way to go.

 

[JimL11]

For some reason the pic didn't show up. Here it is. The constant current loads are on the aluminum heatsink, which is mounted where the output resistors used to be.

 

[ahmedie]

legendary omega on auction ... 2000$ and going up!!
https://page.auctions.yahoo.co.jp/jp/auction/b294416976

auction closed at 8,000$ ... just wow

 

[DJ The Rocket]

. It is one to know how to do something, it's another to be able to teach it to an amateur.

My dad used to say if you can't teach it, then you don't really understand it

 

[DJ The Rocket]

I lost interest in Stax amps beyond that point, though admit is was on bog standard Stax amps, not modded units.

Correct me if I'm wrong, but aren't all or most of Mr. Gilmore's designs a mixing and matching of cloned Stax designs? I.E. the output stage from one amp, combined with the power supply from another one, etc.

 

[SeaWo|f]

It has gone both ways, he has taken and modified stuff that they have come up with and they have licensed things he has come up with..

 

[AudioThief]

I have purchased the stax 007. I was not aware if the color differences, do I thought this was a mk2,5 but my pair has champagne housing with brown pads, whicj I believe is.mk1.

Unfortunately his t1 amp was not working after the repair. Which means I need a new amp. There is a srm 1 pro, a 727 and a 313 on the domestic used market. Any of these a noticable step up from my lowly 252s, or should ai aim higher?,