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post #19561 of 24765

Thanks a lot for your reply! I'll report back once the Stax get here. biggrin.gif

 

e: Good to know about the F3, I was considering building one but wasn't too sure what to expect from it.


Edited by PretentiousFood - 9/21/12 at 5:53am
post #19562 of 24765
Quote:
Originally Posted by Keithpgdrb View Post

I dont see 1k or 200R anywhere?  

 

Offset - B50XΩ J  Board lists them as 50k

 

Balance - B5KΩ M  Board lists at 5k

 

I wonder if I could pick these up at a place like radio shack?  or are they just too cheap?  Would this work for the offset?  http://www.radioshack.com/product/index.jsp?productId=2062302&filterName=Type&filterValue=Trimmers

 

again, I can instal it, but I'm not educated enough to pick the proper parts yet.

 

should I just replace the offset pots?  or should I do both sets? 

 

It appears you have some bastard version of the SRM-1 Mk2.  There were a number of side steps as they evolved from the SRM-1 to the Mk2.  My first stop would be to replace all the pots but something identical would be a bad choice imho..  There are so much better pots out there now and something like 81-PV37W503C01B00 and 81-PV37W502C01B00 should fit.  Do check the datasheet though but I used the right angle version in my SRA-12S to replace the same style pots. 

 

Next step is to measure all the resistors in circuit to get the basic idea if they are in spec or not.  Any conflicts between the channels means it's a good idea to take a closer look by lifting one end and testing it like that. 

post #19563 of 24765

He shoots he scores http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=130770910153 .  I bet that's a bad combo and the  T1 will go a lot better with my Lambda Signatures. I thought they only sold the regular bias Sigmas with a stand.


Edited by jaycalgary - 9/22/12 at 8:25am
post #19564 of 24765

Hi, anyone knows which is the best choice for pairing with the sr-252s, the stax sr-207, sr-307 or sr-407?

post #19565 of 24765

The SR-252s is selling as a set with the SR-207. You can use any Lambda phones with this amp. It depends on your budget and wich phones fit best to your taste.
 

post #19566 of 24765
Quote:
Originally Posted by spritzer View Post

 

The drivers are completely modular but they need to be assembled in a clean room if you want them to be noise free.  Given that the D/S spacing on that driver is 0.5mm then the particles that cause problems are tiny to say the least. 

 

Yama's isn't even a service center to be honest.  With the headphones they just replace parts but on the amps they replace with what ever they find at the bottom of the parts drawer.  Horrible stuff... 

 

Actually, on second look (and I am not familiar with Stax driver assembly and parts) it appears that there are two round gold coloured plates with many small holes throughout and there is a clear film going between them which appears fully intact. What I was initially calling the mylar might actually be just dust covers? They are very very fine and light and see through (not sure what they are made of). Assuming this is correct, is there an easy (and safe) way to energize the drivers to test them out? I do have an extra cable handy.

post #19567 of 24765

I had no doubt that the main diaphragm was intact but the dust covers (made out of ultra thin PVC by the way) are essential to keep the drivers noise free.  At these small tolerances a tiny spec of dust will cause them to buzz and pop like mad which is quite annoying.  You can power them up though and connect to a Stax amp in the current state.  Of the 3 wires which go to each earpiece the center is the bias and it goes to the center terminal on the drivers while the one with the stripe is + and goes to the gold plate closest to the ear.  Be sure to cover the open surface of the driver with something solid before soldering as even a small drop of flux castoff will burn through the driver.  It's also advisable to keep soldering time as low as possible.  Anything over a second is a very bad idea. 

post #19568 of 24765

Thanks, will give it a try one of these days.

post #19569 of 24765
Quote:
Originally Posted by spritzer View Post

 

It appears you have some bastard version of the SRM-1 Mk2.  There were a number of side steps as they evolved from the SRM-1 to the Mk2.  My first stop would be to replace all the pots but something identical would be a bad choice imho..  There are so much better pots out there now and something like 81-PV37W503C01B00 and 81-PV37W502C01B00 should fit.  Do check the datasheet though but I used the right angle version in my SRA-12S to replace the same style pots. 

 

Next step is to measure all the resistors in circuit to get the basic idea if they are in spec or not.  Any conflicts between the channels means it's a good idea to take a closer look by lifting one end and testing it like that. 

 Took a look at those pots, and the data sheets say they adjust from the top, so they should be great.  They are however the same value as the originals.  I thought you originally suggested an increase to give me more room to dial it in?  But if keeping the values consistent and checking the resistors is the better way, I'm on board.

 

My unit is serial # A 4175.  I understand that the A units are the early ones.  I dont care of course, as performance is my main concern.   It does have two normal bias plugs, and if my cans die, I would probably try to alter the circuit to normal/pro.  I got this unit really cheap, so I've got some money to tune it up as best as it can get.  Here is a better pic of the circuit board overall.  maybe it will help as we continue.  I focused on the components, not the big caps or transformer.  Cant thank you enough for all your help thus far spritzer.

 

post #19570 of 24765

Two normal bias outputs make a lot of sense as this would make it the earliest version of the Mk2 amp.  The basic building blocks are the same though as the later ones but they increased the bias on the outputstage and made some other changes. 

 

Couple of things you could check for me to get a better picture of the circuit, what is written on the transistors.  The TO126 units (squares without heatsinks) are probably all 2SA1156's but I'm not sure what the TO92's are  (half circle ones) and the ones on the heatsinks.  101 and 102 are the input fets so probably J113 or something like that and the other 92's are probably D735 which would make them the bottom of the output stage. 

 

Since the next pot values are +50% then it makes sense to tweak the resistor values instead.  Better yet would be to just replace all the resistors with modern metal films as the amp clearly works as it so the sand is all good.  This would make it essentially new and cost only a few $.  This is what I do with some of these older amps as carbon+moisture is a very bad mix in the long term.  If you can upload a higher resolution version of the same pic then I can pick out the resistor values for you. 

post #19571 of 24765
Quote:
Originally Posted by jaycalgary View Post

He shoots he scores http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=130770910153 .  I bet that's a bad combo and the  T1 will go a lot better with my Lambda Signatures. I thought they only sold the regular bias Sigmas with a stand.

The Sigma Pros came with a brown nextel spray on the stand, compared with the Sigmas, which had a grey Nextel spray.

The Ear pads (including the mesh attached to the ear pads) are still available from, for example, Audiocubes, so a much more cosmetically acceptable effect should be doable. The Sigma series may be a bit underpowered by the SRM-T1, but they are great phones (and the Sigma Pro is very good too - IMHO, it bests the Sigma/404 in a couple of areas too).

Nice price, presuming all is in excellent condition.

post #19572 of 24765

Don't you use them with Lambda pads? This will be my 2nd pair of Sigma pros. I gave up on the first pair a bit quick and sold them. They are in Australia now. I am sure I will keep this pair and looks in better shape. I won't do the 404 mod I'd make a pair from scratch first. I am going to play them on the 717 for now till I get/build better. I have a diy kgsshv in the works but it will certainly be a while as my skill in that area is lacking. You sure have stood behind the Sigma's for a long long time now.

post #19573 of 24765

Wondering if anyone has tried using a mcintosh dac or source with a woo amp and a pair of STAX. I really like McIntosh sound and I have always wanted the WES and SR009 but never hear of anyone using Mc gear with the usual popular electrostat amps, was thinking of going this way once I settle to a bigger place and save enough for my dream speaker+ STAX rig. 

post #19574 of 24765

Would a Stax Lambda Pro with an SRM-T1 MkII  amp be good buy at $500 ? Its supposed to be in good shape .

post #19575 of 24765

No it will start an expensive addiction.

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