[Number9]

Quote:

 
These mods don't alter the PSU in either amp so the voltage swing is the same as stock. 

 
Thank-you, but now I'm confused in understanding what is really at play with the 007T mod. I thought the tube swap for 6S4A's was to improve voltage swing. 
 

 

[kevin gilmore]

The 6s4 mod improves the distortion characteristics of higher amplitude voltage swings.
The sound difference is significant. A lot less constriction and compression.

 

[spritzer]

The 6CG7's are only rated at 330V but asked to work at 700VDC.  This puts a lot of strain on the tubes when they are asked to swing higher voltage (i.e. higher volume levels).  The 6S4A is rated at 550V with very high peak voltage levels so it's far more comfortable at these voltages. 

 

[Number9]

Its funny, I had read numerous mentions about the mod, but I was entirely left with the impression it was about increasing voltage swing. 
 
Thank-you gentlemen, that clarifies things.

 

[forbigger]

anyone heard this DAC before ?
 
http://app.audiogon.com/listings/da-converters-stax-x2-t-2013-02-05-digital-england
 
Does it command the asking price ? Just curious anyway........

 

[yawg]

Quote:

Its funny, I had read numerous mentions about the mod, but I was entirely left with the impression it was about increasing voltage swing. 
 
Thank-you gentlemen, that clarifies things.

It is about voltage swing - or not? The voltage swing of the tubes. With the alternative tubes the amp can realize more of the voltage swing potential of the PSU and deliver improved dynamics.
 
I have a T1S and am also very interested in this mod. All Stax cans will make good use of every little bit of extra clean power you will feed them IMHO.
 
Does the mod fit into the original enclosure?

 

[yawg]

Quote:

anyone heard this DAC before ?
 
http://app.audiogon.com/listings/da-converters-stax-x2-t-2013-02-05-digital-england
 
Does it command the asking price ? Just curious anyway........

Considering what people pay for the 009 this looks like a steal.

 

[autoteleology]

Quote:

anyone heard this DAC before ?
 
http://app.audiogon.com/listings/da-converters-stax-x2-t-2013-02-05-digital-england
 
Does it command the asking price ? Just curious anyway........

 
Found a picture of it by chance in this review:
 
http://www.6moons.com/audioreviews/stax/stax.html

 

[spritzer]

Quote:

It is about voltage swing - or not? The voltage swing of the tubes. With the alternative tubes the amp can realize more of the voltage swing potential of the PSU and deliver improved dynamics.
 
I have a T1S and am also very interested in this mod. All Stax cans will make good use of every little bit of extra clean power you will feed them IMHO.

 
Voltage swing is a crap measurement at the best of times as it tells us pretty much nothing, least of which how that voltage swing translates into the load the amp is trying to drive.  It's just a maximum rating but doesn't tell us anything about the quality of the output at these levels. 
 
The T1S only has two tubes so the 6S4A won't work.  You can swap in the ECC99 but it uses more heater current and you need to rewire the socket and change the plate resistors. 

 

[kkqewl]

Hi,
 
 
I have recently tried the ECC99 mod on my SRM-T1 and all went well until I tried to set the bias,  on left side I was able to get it under one volt but on the right side a get a reading of 400 volts bias and 380 volts for the offset !!
 
I have rebiased this unit numerous times with the stock tubes in it and never had any issues ?
 
I have rechecked my work with the pictures provided by those on this site and i can't find any errors, is it possible I have a different version T1 ,   The serial number is B8335 for this unit. here are some pictures.
 

 

 
Any help would be appreciated     

 

[yawg]

Quote:

 
Voltage swing is a crap measurement at the best of times as it tells us pretty much nothing, least of which how that voltage swing translates into the load the amp is trying to drive.  It's just a maximum rating but doesn't tell us anything about the quality of the output at these levels. 
 
The T1S only has two tubes so the 6S4A won't work.  You can swap in the ECC99 but it uses more heater current and you need to rewire the socket and change the plate resistors. 

I read a bit on the ECC99 and "equivalents" on the German tubes forum and the "consent" was that the E192CC was even better than the ECC99. Wrong?

 

[spritzer]

Quote:

Hi,
 
 
I have recently tried the ECC99 mod on my SRM-T1 and all went well until I tried to set the bias,  on left side I was able to get it under one volt but on the right side a get a reading of 400 volts bias and 380 volts for the offset !!
 
I have rebiased this unit numerous times with the stock tubes in it and never had any issues ?
 
I have rechecked my work with the pictures provided by those on this site and i can't find any errors, is it possible I have a different version T1 ,   The serial number is B8335 for this unit. here are some pictures.
 

 

 
Any help would be appreciated     

 
The pics are too small for me to see any detail but changing the plate resistors to 30K units and disconnecting/rewiring the filaments is all you need to do.  Something is very wrong to give these results so shorted plate resistors, shorted tubes both spring to mind. 
 
Quote:

I read a bit on the ECC99 and "equivalents" on the German tubes forum and the "consent" was that the E192CC was even better than the ECC99. Wrong?

 
E182CC?  It may be slightly better for some uses but here it's worse than the stock 6CG7. 

 

[yawg]

Quote:

 
E182CC?  It may be slightly better for some uses but here it's worse than the stock 6CG7. 

Thanks spritzer. I just found out that the only factory that makes the ECC99 is JJ. I have zero trust in JJ as all the triodes I tried from JJ sounded the worst of all contenders I tried in the same spots in my tube gear (DAC, pre- and power amps). They all had the same signature: bloated mids, treble rolloff and muddy bass. The types I tried were 6922, [size=small]12AX7 and [/size][size=small]12AU7.[/size]
 
[size=small]If there is no alternative, JJ is a definitive no-no.[/size]
 
[size=small]Best regards, Jörg.[/size]

 

[spritzer]

The ECC99 is a new design so it's naturally only made by one company.  It's a close relative to the 12BH7 though... 
 
The JJ ECC83 is better than any of the nos tubes measured but they will naturally not fix badly designed circuits.  Noise on the least good sets was down a few dB compared to the nos tubes. 

 

[kkqewl]

 Hi Spitzer,
 
Thanks for the reply, I think I have a bad tube since if I switch tube positions, the problem is now on the other channel and the previous channel is now OK !
 
These are brand new  ECC99 tubes from JJ so maybe there is somthing about their quality control that is lacking ?. Never thought that a brand new tube would act like that?  I use mostly older NOS tubes in much of my audio gear that are still going after 40+ years !
I have a replacement ECC99 on the way so hopefully I will be able to up and running soon.
 
Actually I have two SRM-T1 units , one that is still bone stock and this one I am modding to ECC99 tubes. I want to be able to compare them directly to see what sonic changes or improvements occur.  
 
I will report my findings as soon as I can.