The Headcase Stax thread

[spritzer]

This piece from a recent Hifi-news does explain some things...

 

 

[kevin gilmore]

you are loosing so much efficiency by lowering the bias by that much.

 

find a way to double the bias voltage. way better than arcing the diaphragm

and not even knowing it.

[edodo]

Hi there, I'm looking for Toshiba tubes for the Stax amps 006t 007t. Does anyone can tell me if the branding is of any importance or is there photos of the Toshibas somewhere?

[padam]

Raytheon is pretty much the same thing.

[shipsupt]

My 717 has been cutting out intermittently.  My crappy powers of deduction lead me to believe that my source was tripping the DC input protection circuit, but after changing the source I eventually had the same issue.

 

I took the amp to the bench to set DC offset and balance.  I bench tested for hours and everything was AOK.  

 

Moved it back into the "rack" and after a short time I had a trip again.  I decided to pull the amp out of it's normal spot and see if heat was my issue.  I ran it overnight in the open with no problem.  So now I'm thinking heat is my issue.

 

 

How much space do these amps need for cooling?  It had easily 3 inches above it and the room is not warm (I'd guess 16-18C ambient temperature right now).  I could place my hand on the amp when it tripped and it was hot, but not so warm that I couldn't keep my hand on it.

 

If it is being a little "over sensitive" to heat what are some things I should consider checking?

 

Thanks.  Thread searches have gotten me this far, so appreciate the help from the "archives" already.

Edited May 29, 2013 by shipsupt

[spritzer]

The heat aspect is hard to judge, way too many variables but dust inside the unit can also be a factor.  It the amp is one of the first built then you can be running into cap problems given the super simple power supplies. 

[kevin gilmore]

What you need to do is measure before the relay when it cuts out.

All 4 outputs. You may have one failing or one temperature sensitive

Component causing all the trouble.

Or temporarily defeat the relay circuit to make it easier to measure.

A bad power supply cap can definitely do this

[shipsupt]

Thanks gents.  I was trying to keep this thing limping along until my KGSShv is done.  Time to get that project done and spend some time with this guy.  I'll some more testing to see if I can narrow things down to one componenet, but I'm thinking just doing a recap at this point is going to be a good idea.

 

Any other parts in there I should consider replacing while I'm at it?

[spritzer]

Nothing springs to mind. 

[shipsupt]

Thanks.  I've seen the thread over at the other place where that guy is putting in all kinds of crazy stuff in.  I'm happy to keep it stock and make it reliable.

[spritzer]

I'm a bit amazed you could read that thread.    The guy is a bit of a case but in a nutshell he wants a separate PSU for the low voltage section (which draws almost no power) but not for the high voltage (which draws all of the power), less feedback and bigger caps.  He also calls the amps cheap in terms of build quality and shames Stax for using single transistors matched into pairs.  The guy has clearly never built anything as a product or indeed lives in the real world. 

[Nebby]

 

shames Stax for using single transistors matched into pairs

 

He put Stax down for matching single transistors? That makes no sense. Actually now that I think about it, didn't nwavguy tout duals as having better matching than singles or something to that effect? That might explain that guys reasoning...

Edited May 30, 2013 by Nebby

[spritzer]

Yes but it isn't true as you can do much better matching than the factory job and link the two dies thermally.  This guys claim was more than there were still plenty of P-fets to be found in duals as he was able to get some. 

[spritzer]

Just got a brand new SRS-2170 from Japan and why do Stax always do this, make the base model so bloody good.  The other Lambda models always have some issues (too fucking bright being my biggest issue) but this one is brilliant even with the SRM-252S.  I guess it is their way of making the more expensive models sound "better" but for fucks sake... 

[P.C.]

Just got a brand new SRS-2170 from Japan and why do Stax always do this, make the base model so bloody good.  The other Lambda models always have some issues (too fucking bright being my biggest issue) but this one is brilliant even with the SRM-252S.  I guess it is their way of making the more expensive models sound "better" but for fucks sake... 

Very interesting comment.

 In your opinion how does this set compare with the similar priced Koss ESP 950 , which I liked  but have avoided  buying   due to the known QC issues.

Thanks Philip

[spritzer]

It's been too long since I've had an ESP950 here for any meaningful comparisons but as a system it never impressed me all that much.  That is mostly the amps fault though, same as if you'd try a Sennheiser HE60/HEV70 setup which isn't very impressive at all. 

 

The Stax setup is also cheaper and there are huge variables with the ESP950 based on how the damping is configured. 

[DefQon]

Hey spritzer

 

Thought I'd get a better response here, managed to grab hold of a SRM-300, I've read your F/S thread on the other forum that you had the opamps removed and had another one installed, can the SRM-300 accomodate opamps such as the 627 or so that require a bit more power to work?

 

Hopefully when I receive the amp the 100v trafo can be re-wired for 240v. Cheers

[spritzer]

They will work but not optimally which kinda defeats the point.  I used OPA2604's which is very good and drop in compatible with most circuits. 

 

All the SRM-300's can be rewired but the 117V wires have been cut short so you'll probably have to extend them.  No big deal really but when I do this I run the wires to the correct spots on the PCB and then jumper there for the correct voltage.  Makes it easier to change later on. 

[DefQon]

Thanks for that, I would normally search before asking but since I can't find anything about it, which would be better, a modded SRM-300 vs SRM-323S? Will be using it to drive various Lambda's for now.

[spritzer]

323S by a nice margin. 

[VPI]

I actually like my 323s, until I listen to a BHSE, and then I want to shoot it for being so comparatively bad.

[spritzer]

Well you want to shoot anything that even might be a zombie...    

 

There is a giant leap there in performance though but for the price the 323S really isn't bad and the SRM-300 is far worse.  I just jumped from the 252S to the BHSE and yeah... a tiny bit of difference. 

[DefQon]

FFS, ordered the 323S as well. This better be a big improvement over the SRM-300 and my old recapped SRM1 MK2.

[livewire]

Doubt it. A BHSE would be.

[complin]

Yeh the entry level Stax amp is bloody great value for money, and performs respectably with most of the range.  

Exceptions I think are the Omega and 007 and thats where things like the BHSE and T2 really make a difference

 

Well you want to shoot anything that even might be a zombie...    

 

There is a giant leap there in performance though but for the price the 323S really isn't bad and the SRM-300 is far worse.  I just jumped from the 252S to the BHSE and yeah... a tiny bit of difference. 

Edited June 19, 2013 by complin