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The Stax Thread III - Page 92

post #1366 of 4018
Some wires should be resoldered, that's it I suppose
post #1367 of 4018
Quote:
Originally Posted by davidsh View Post

Some wires should be resoldered, that's it I suppose

 

Yes this too.

post #1368 of 4018
Quote:
Originally Posted by Pier Paolo View Post
 

Hi, I have a question for Kevin or Spitz (or for everyone that can help me).

I have an SRM-600 LTD and I would try to transform it in a 006Ts.

I think that I have to change the 4+4 plate resistors (with what kind) and to change some contact in the valves sockets and then use two 6CG7.

May someone be more precise so I can proceed in this transformation?

Also: do you think that is a good idea (I have a 507 to drive) or not?

 

Thank You in advance

PP

 

Change the plate resistors to 30K/2W or greater wattage.  I use Koa SPR2's raised about one inch off the PCB but metal film or metal oxide will be fine as well. 

 

As for rewiring at the tubes, the current heater setup is for the 6CG7 which is a 6.3V tube.  The ECC99 is 12.6V with a center tap so you need to cut one leg of the heaters and connect that to pin 9.  Bridge 4 and 5 so that the ECC99 runs at 6.3V.  This is for both tube sockets. 

 

The mod does transform the amp into something much better so well worth it. 

post #1369 of 4018
Quote:
Originally Posted by 2Erly View Post
 

Can someone tell me if this T1S amp can work on US voltage? It lists 100V,117V, 220V, 240V on the rear but under the plug says 240V  can you just plug in the US power cord and it'll work?

 

 

The easiest way to use this in the US is to get a step-up transformer  like  http://www.world-import.com/all-transformers.htm

 

You plug the transformer into the wall; the wall supplies 120 volts AC to the transformer which steps that up to 240 volts AC  which is what the SRM-T1s  wants.

 

The USA has standardized on something close to 120 volts - 112, 117, 122....US ac power is roughly 120 volts give or take.

 

In Europe it is 220 volts to about 240 volts.  In Japan it is 100 volts.

 

You could adjust the wiring in your amp to set it to expect 120 volts AC instead of the 240 volts it is now set up for, but you will have to move some wires and possibly do some soldering;  if you get it wrong you could damage the amp.  If you are not comfortable with this kind of work, give the job to someone who IS comfortable with this kind of work.  A local audio repair shop should be able to do this for you for maybe $25~$50  I would guess.

post #1370 of 4018
The consequences of even attempting to run a 120V amp on 220-240V are fairly obvious, including but not limited to small explosions and forest fires.

But with a 220-240V 50-60Hz amp, what are the risks assuming it could even power on or operate at 120V?
post #1371 of 4018
Quote:
Originally Posted by 3X0 View Post

The consequences of even attempting to run a 120V amp on 220-240V are fairly obvious, including but not limited to small explosions and forest fires.

But with a 220-240V 50-60Hz amp, what are the risks assuming it could even power on or operate at 120V?

 

There are electronics that have a maximum rise time and will be damaged in a brown out. That said, I seriously doubt this amplifier is one of those. If you left it on for any considerable amount of time, the tubes could be damaged by having half filament voltage while operating. You should know fast enough whether or not it is working, though.

 

The odds of it working with half input voltage are effectively zero. If you are sure it is set on 220v, there is no point in trying it at 110v. I'd only consider trying if there is some reason to believe it might automatically configure, which doesn't seem likely if it is marked for a specific voltage.

post #1372 of 4018
Quote:
Originally Posted by dude_500 View Post
 

 

There are electronics that have a maximum rise time and will be damaged in a brown out. That said, I seriously doubt this amplifier is one of those. If you left it on for any considerable amount of time, the tubes could be damaged by having half filament voltage while operating. You should know fast enough whether or not it is working, though.

 

The odds of it working with half input voltage are effectively zero. If you are sure it is set on 220v, there is no point in trying it at 110v. I'd only consider trying if there is some reason to believe it might automatically configure, which doesn't seem likely if it is marked for a specific voltage.

In my case, it is not a SRM-T1S but rather a SRM-323S. The seller advertised it as a 120V USDM amplifier but I see quite clearly now on the back that it is labeled 220-240V 50/60Hz. The internals were not tampered with so I highly doubt it was wired to 120V input.

 

I hadn't noticed any hiccups in performance or operation using it up until I had noticed this (several months). I'll have a bone to pick with the seller for sure.

post #1373 of 4018
Quote:
Originally Posted by 3X0 View Post
 

In my case, it is not a SRM-T1S but rather a SRM-323S. The seller advertised it as a 120V USDM amplifier but I see quite clearly now on the back that it is labeled 220-240V 50/60Hz. The internals were not tampered with so I highly doubt it was wired to 120V input.

 

I hadn't noticed any hiccups in performance or operation using it up until I had noticed this (several months). I'll have a bone to pick with the seller for sure.

 

In the case of a solid state amp, it becomes considerably more likely that it'll seem to be working since there are no filaments. The only way it can actually work properly with either voltage is if it had a switching supply, which I'm guessing Stax amps never do. 

 

That leaves two possibilities, either it was modified, or you're using it at half voltage. In most amplifiers, this would take stages out of proper bias, reduce voltage swing by a factor of two, and greatly hurt amplifier linearity and sound quality, but it'd likely still act as an amplifier. In most but not all cases, there'd also be severe 60hz humm since you wouldn't be over the linear regulator dropout. It seems unlikely you wouldn't know if this is the situation, but I could certainly see it as conceivable. (Inconceivable if you have a lot of experience with Stax products and would notice half volume, poor linearity, etc.)

 

Kind of puts you in a sticky situation, since if it was modified to operate on 110v and you connect 220v it'll blow up! I would definitely contact the seller and ask for details on the input voltage.


Edited by dude_500 - 1/23/14 at 11:23am
post #1374 of 4018
Quote:
Originally Posted by dude_500 View Post
 

 

In the case of a solid state amp, it becomes considerably more likely that it'll seem to be working since there are no filaments. The only way it can actually work properly with either voltage is if it had a switching supply, which I'm guessing Stax amps never do. 

 

That leaves two possibilities, either it was modified, or you're using it at half voltage. In most amplifiers, this would take stages out of proper bias, reduce voltage swing by a factor of two, and greatly hurt amplifier linearity and sound quality, but it'd likely still act as an amplifier. In most but not all cases, there'd also be severe 60hz humm since you wouldn't be over the linear regulator dropout. It seems unlikely you wouldn't know if this is the situation, but I could certainly see it as conceivable. (Inconceivable if you have a lot of experience with Stax products and would notice half volume, poor linearity, etc.)

 

Kind of puts you in a sticky situation, since if it was modified to operate on 110v and you connect 220v it'll blow up! I would definitely contact the seller and ask for details on the input voltage.

Thanks; this is just the type of answer I was seeking. I don't suppose it was converted as I received it brand new.

 

I guess the other option would be to open it up with the intent of switching to 120V, with the potential of being pleasantly surprised.

 

It sounded "better" than either my 120V SRM-T1 or SRM-T1S ever did, but seems significantly less sensitive on the dial than the latter of the two. Guess it's time to crack it open...


Edited by 3X0 - 1/23/14 at 1:58pm
post #1375 of 4018

 

The Liquid Lightning mk2 is such a delightful sounding amp. I have been enjoying both pairs of my Stax headphones on this amplifier so much. Stunning performance..................

post #1376 of 4018
Quote:
Originally Posted by Pier Paolo View Post
 

Hi, I have a question for Kevin or Spitz (or for everyone that can help me).

I have an SRM-600 LTD and I would try to transform it in a 006Ts.

I think that I have to change the 4+4 plate resistors (with what kind) and to change some contact in the valves sockets and then use two 6CG7.

May someone be more precise so I can proceed in this transformation?

Also: do you think that is a good idea (I have a 507 to drive) or not?

 

Thank You in advance

PP

No answer?:popcorn:

post #1377 of 4018

just noticed this.  You have to rewire the socket for the filament difference

or make an adapter, and then the tubes won't fit in the case. Otherwise

no other circuit changes. You will have to adjust the offset and differentials.

 

If the srm323 is wired for 240v, its not even going to make any music

when plugged into 120v. Or if it does make music its going to be very distorted.

A 240V model would have all 6 wires on the transformer, so the conversion to

120V is easy. Its the 200V or 100V model that is the problem.


Edited by kevin gilmore - 1/24/14 at 7:38am
post #1378 of 4018
Quote:
Originally Posted by kevin gilmore View Post

just noticed this.  You have to rewire the socket for the filament difference
or make an adapter, and then the tubes won't fit in the case. Otherwise
no other circuit changes. You will have to adjust the offset and differentials.

Welcome back, Kevin, and thank you.
I though that I had to change the plate resistors. I have (4+4)X30Kohm now with the ECC99.
And which tubes you can suggest? Or it would be better to stick with the 99?
Also, when you say "You will have to adjust the offset and differentials" are you talking about the same bias setting procedure (set near to zero V) that I use when I change the tubes?
post #1379 of 4018

bias settings, yes. which really are not bias settings.

 

you should check out how the filaments are actually wired first.

I think its 6V, but it may be 12V. If it actually is 12V, then you

have to wire the 6cg7 filaments in series because those are 6V

tubes only.

post #1380 of 4018
Quote:
Originally Posted by kevin gilmore View Post

bias settings, yes. which really are not bias settings.

you should check out how the filaments are actually wired first.
I think its 6V, but it may be 12V. If it actually is 12V, then you
have to wire the 6cg7 filaments in series because those are 6V
tubes only.

Ok, Kevin, I will try. Have you an srm-006 ts schematic, please?
Edited by Pier Paolo - 1/24/14 at 10:46am
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