[dukja]

I have some problem getting the Right channel of my recently received SRM-1 MK2 PP tune to range.
 
The amp was 240V and I rewired the transformer to 117V.  The amp turned on alright.  But the balance and offset reading on both channel are out of range.  I can adjust the left channel into range, but not the right channel. 
 
I started by adjusting the pot labeled as BALANCE.  However, the voltage (V_R+/R-) between R+ and R- will never go down to zero.  Then I found out that I can adjust the pot labeled as OFFSET to make the V_R+/R- to zero.  However, this shift the offset measurement (the voltage between R+ and ground post, V_R+/G) way off to >100V.  And if I try to adjust the V_R+/G to zero, then V_R+/R- will be way off >100V.  The best I can do is to find a mid point where V_R+/R- is about 5V and V_R+/G is about -50V.
 
First question, should I only adjust the pot labeled as BALANCE when I try to make V_R+/R- to zero?  (or I need to adjust OFFSET pot as I did).
 
I highly suspect this amp has problem.  Thanks for the help!!

 

[Knijsterbek]

Quote:

I have some problem getting the Right channel of my recently received SRM-1 MK2 PP tune to range.
 
The amp was 240V and I rewired the transformer to 117V.  The amp turned on alright.  But the balance and offset reading on both channel are out of range.  I can adjust the left channel into range, but not the right channel. 
 
I started by adjusting the pot labeled as BALANCE.  However, the voltage (V_R+/R-) between R+ and R- will never go down to zero.  Then I found out that I can adjust the pot labeled as OFFSET to make the V_R+/R- to zero.  However, this shift the offset measurement (the voltage between R+ and ground post, V_R+/G) way off to >100V.  And if I try to adjust the V_R+/G to zero, then V_R+/R- will be way off >100V.  The best I can do is to find a mid point where V_R+/R- is about 5V and V_R+/G is about -50V.
 
First question, should I only adjust the pot labeled as BALANCE when I try to make V_R+/R- to zero?  (or I need to adjust OFFSET pot as I did).
 
I highly suspect this amp has problem.  Thanks for the help!!

I remember I had the same experience when I adjusted mine. It seemed to me that balance and offset markings were switched on the PCB.
If you adjust offset with the one pot and balance with the other and repeat measurements a few times (alternated), it should be possible to get both readings around zero. At least, with mine, that worked out well (with 230V AC mains and the amp wired for 240V).
 
 

 

[dukja]

I used two DMMs to measure V_R+/G (volt between R+ and ground post) and V_R-/G simultaneously and figure out how these pots work.
 
The OFFSET pot adjusts V_R+/G and V_R-/G reading in the opposite direction (one increased and the other decreased)
 
The BALANCE pot adjusts V_R+/G and V_R-/G reading in the same direction (both increased or decreased).
 
With the combination of these two pots, one is suppose to be able to make both V_R+/G and V_R-/G to zero simultaneously, which should be equivalent to the procedure mentioned by previous posts.
 
But with my right channel, I can only adjust both V_R+/G and V_R-/G to about 48V with OFFSET pot.  My BALANCE pot cannot reduce that value but only increase it.  Is my BALANCE pot bad?   Or other components are out of spec?
 
Thanks for the help.
 

 

[dukja]

My 407 finally came but now I have not even plug it in yet, just because of this issue. 

 
Or can I at least get a listen?  Is it safe to do so with such unbalanced reading?

 

[Knijsterbek]

Have you tried to first get V_R+/G or V_R-/G to 0V DC and then adjust V_R+/R- for 0 DC?
In other words: if there is no offset pot setting at which V_R+/G and V_R-/G is lower than 48V DC, then I assume that something is out of specs.
BTW: did you close the volume pot to zero?

 

[dukja]

Sprizer PM me briefly before he heading to bed and his reply confirmed my observation:
 
1. The labels on the PCB were (probably intentionally) WRONG.  The pot labled as "offset" is actually "balance" and vice versa.  I already suspected that in my adjustment.
2. Spritzer mentioned that adjustment on one pot will knock the other setting off.  That is also what I suspected and observed.  However, if you have two DMMs, you can very quickly dial the number into range: I basically adjusted the BALANCE (labeled as "offset") pot and see the reading of V_L+/G and V_L-/G to be the same.  Then, adjust OFFSET (labeled as "balance") until both reach zero.  This is actually exactly what was described in the posts with one DMM.  Just the wrong label confused the hell out of me.

3. I did leave the volume pot to zero.  Do I need to connect source (input)?  I don't think so though.
4. And if I get either V_R+/G or V_R-/G to 0V DC, then the other will be way off.  There is no way I can make both zero simultaneously.
 
But still I cannot make right channel dial into range.  If someone experienced this before can offer me a quick diagnosis, I should be able to debug it out.  OR I will ask the sell to take it back if it is confirmed bad.
 
A hint for preventing temperature interference during adjustment: 
Just slide the top case half way and use a stack of paper or book to cover the other half.  Leave a crack to allow screw driver coming down for adjustment.  I pretty much can finish the adjustment without introduce any reading perturbation.  Otherwise, the reading was just drifting too rapidly.

 
Quote:

Have you tried to first get V_R+/G or V_R-/G to 0V DC and then adjust V_R+/R- for 0 DC?
In other words: if there is no offset pot setting at which V_R+/G and V_R-/G is lower than 48V DC, then I assume that something is out of specs.
BTW: did you close the volume pot to zero?

 

 

[FlyingBear]

I live in the San Francisco Bay Area, but travel constantly, including to Japan. If I have time, a few hours geeking out in Akihabara is always fun. Look what I saw in Yodobashi Camera, in their high-end headphone section (which is bigger than most US audio stores):
 

 
There's more:
 

 
It's a little noisy, but I was able to listen to the same SACD on the SR-007 MkIIs and the SR-009s. As usual in Japan, nobody messes with you, and you're left to listen to what you want for as long as you want. I should have moved the SR-007 MkIIs to the SR-009 amp for a true comparison, but they were secured in their area. The SR-009s at first had only the left channel working, but a Yodobashi guy cleaned the contact pins on the plug and then they worked just fine.
 
I'm very new to Stax: I'm waiting for my Woo WES and MkIIs to arrive. So these impressions are from a noob, in a less-than-quiet environment. The difference between the MkIIs and the SR-009s is, of course, subtle, but evident even to a new listener. Acoustic guitar material had more attack and impact on the SR-009s. There is slightly more well-defined bass. The overall experience though, is clearly superior. Perhaps it's partly because the rotating-within-rotating earcups and transducers on the MkIIs take some getting used to, and I'm not there yet, but the SR-009s are immediately comfortable with no adjustments. I was fiddling with the MkIIs all the time. But the "wow" factor was higher with the SR-009s too. But gosh, $5000? A future treat, perhaps.....

 

[TMoney]

Whoa! Awesome!
 
Did they actually have any stock on the SR-009s or was it just the floor model?

 

[FlyingBear]

Quote:

Whoa! Awesome!
 
Did they actually have any stock on the SR-009s or was it just the floor model?

I didn't ask, sorry.

 

[Hammerzeit]

It's...It's so beautiful *sheds tear* Also the SR 2050a should arrive tomorrow, quite excited.

 

[livewire]

Yes. Tis a thing of beauty.
 
Awrite on the Stax Basic!
 
Listening to "The Year Of The Cat" on mine right now. Sublime....

 

[Ckaz]

 
I've been hearing a lot about Stax lately, and they seem like something I really wouldn't mind trying out. However I'm a bit confused as to how they work.

 

What is confusing me are their driver units. How exactly do I go about driving a pair of Stax headphones? I'm guessing they don't just plug into any old amplifier, but the driver units that they carry are extremely expensive, more so than even the headphone themselves.

 

Would anybody be able to help clear this up for me?

 

[Hammerzeit]

Got my stax earlier today and I'm loving it.

I think my current headphone stands expresses my feelings perfectly, although I kinda worry that it might mess with the headband.

 

[edstrelow]

Quote:

 
I've been hearing a lot about Stax lately, and they seem like something I really wouldn't mind trying out. However I'm a bit confused as to how they work.

 

What is confusing me are their driver units. How exactly do I go about driving a pair of Stax headphones? I'm guessing they don't just plug into any old amplifier, but the driver units that they carry are extremely expensive, more so than even the headphone themselves.

 

Would anybody be able to help clear this up for me?

Yes  you need either a special head[hone amp or a special transformer which runs off the speaker terminals of a regular amp.  Most people go for the separate headphone amp.  Costwise, you are looking at about the same money for the lower Stax range as for a top-class dynamic system to which most Staxen can be compared.
 
Fortunately these phones and their amps hold up well over many decades and you can get good sets well over 30 years old at a good price on Ebay or in these selling forums.  Stax has made a dozen or more Lambda models over the last 30 years and still makes this basic design.  You may be able to get an old Lambda ( preferably high bias) and an SRM1k2 amp for somewhere between $500-$700.00.  This could be a very good set-up and cost effective as these things go.  You will get better sound, probably the best  there is, with a BHSE and SR009 but that will set you back about $10K not including a few thousand more for a  top class source.
 

 

[gilency]

Another normal bias Sigma for sale in ebay. Expensive, sold as a bundle with SRM-1 MK2, both for 1800.00. Crazy.
They even used John Buchanan's description/history of the Sigma's. 
 
http://cgi.ebay.com/STAX-Sigma-Earspeakers-and-SRM-1-Mk-2-Amplifier-NM-/190534910616?pt=LH_DefaultDomain_2&hash=item2c5cc40298#ht_16701wt_622
 
And an SR-Omega for 3600.00! Crazieeer......
 
http://cgi.ebay.com/STAX-SR-Omega-SR-Ultra-Rare-/260786960748?pt=LH_DefaultDomain_0&hash=item3cb81d396c#ht_500wt_964
 
I dont know if the sellers are legit or not...