[milosz]

Quote:

 
I don't have personal experience with this Nuforce Icon amp so I don't know if it's any good per se but derived from the specs it might be ok.
I've utilized Tripath T-2020 based amps (that don't have more oomph than the Nuforce thingie) in the past for the purpose and it was quite good.
 
 
 
This is at least debatable.
I've owned lots of Stax and third party amps in the past and I switched to transformer/loudspeaker amp solutions.
I still own a humble SRM-313 but I never use it.
A SRM-2xx is even worse.
My combination of a refurbished age old Marantz 4300 (a good sounding amp that did cost as much as a good used car when it was new) and a slightly modded old Stax transformer box sounds way better, and there are even more sophisticated modern transformer designs out there.
For those that own a good loudspeaker amp anyway the transformer box route is still the most cost effective way to get good sound quality (even though the old Stax Pro transformers are more expensive nowadays than a few years ago when I got my two SRD7 Professionell).


 

 
Well that's interesting. I bought a Stax "pro" transformer-bias box so I could try my various electrostatic headphones with some of the amplifiers in my collection. A transformer will limit low frequency response, the high frequency response,  there will be some phase problems,  group-delay issues, harmonic distortion from the core hysteresis properties and so on. If the transformer is designed well, these things can be minimized. However, in the Stax direct drive amplifiers there is no transformer and hence no potential for these problems.  Of course amplifiers come with a whole set of their own issues.
 
Anyway I've got this SRD-7pro, and amplifiers: Citation II with the McShane mods, Forte 4a with the Soderburg mods, two of the original pure class-A Monarchy SM70's, an AMC class-A MOSFET / EL-34 amp, a Mr. Liang 845 SET amp (with 300B driver tubes,) and a Pass DIY F3 class-A power JFET amp (but that probably doesn't have enough power, alas.)
 
In the fullness of time, I will get around to trying these amps with my various electrostatic 'phones (Koss ESP-950, Stax Lambda Signature, Stax SR-007 mk II) on the SRD-7, but I haven't got there yet.  I don't expect to be blown away by the sound, but often these kind of experiments provide interesting results. 
 
Anyone with experience using various amps with an SRD-7 / STAX earspeakers, I'd be glad to hear your impressions.
 
 

 

[Clarkmc2]

To give the energizer box approach a fair shake, that old box needs to be improved a bit. If you can possibly get your hands on a Spritzer board for it, and rewire it direct (skip the speaker terminals altogether), it will be in the high fidelity hunt. The original, unmodified boxes will not give anything a fair hearing. If the amps are really good, they will be at a disadvantage.
 
Another plus, the board will still allow one socket each, Pro and Normal, so all Stax phones are fair game.

 

[NamelessPFG]

So you're all saying that my unmodified SRD-7/SB is really holding these Lambdas back? (Possibly moreso than the TX-SV515PRO I had lying around to drive them with?) They're already a noticeable improvement over the AD700s; how much better does it get?
 
I don't think those Spritzer boards are in production anymore, which will complicate things severely. Why did they go out of production, anyway? Too much cost? Even then, do they require external AC power (making it incompatible with my transformer unit), or are they self-biasing?
 
In terms of rewiring these things, I'm hearing different opinions. Some say to just connect the speaker terminals to the transformers, then the transformers to the headphone sockets, bypassing the PCB altogether. What I'm hearing here suggests to bypass just the earspeaker/loudspeaker switch, from the sound of it. Even then, it would help if I simply knew what wires off the transformers to solder where without having to study the PCB first, though it's probably a good idea to study the PCB and the schematics anyway.

 

[HeadphoneAddict]

Quote:

To give the energizer box approach a fair shake, that old box needs to be improved a bit. If you can possibly get your hands on a Spritzer board for it, and rewire it direct (skip the speaker terminals altogether), it will be in the high fidelity hunt. The original, unmodified boxes will not give anything a fair hearing. If the amps are really good, they will be at a disadvantage.
 
Another plus, the board will still allow one socket each, Pro and Normal, so all Stax phones are fair game.

x2.  
 
I have an old SRD-7 SB that Audiocats modded for pro and normal bias jacks, with inputs directly into the transformers via Vampire banana jacks, and no pass through, and this sounds a bit better than my stock SRD-7 Mk2 or SRD-7 Pro (which I paid over $350 each for the stock pro-bias boxes).  It's more transparent, with better micro-detail and extension; although it is only presenting about a 4 ohm load, or less as frequency approaches DC.  
 
That being said, the stock SRD-7 Mk2 or Pro with an 5-12 watt speaker amp still drove the SR-007 better than either of my old Stax SRM-1 Mk2 Pro amps.  And the transformers with speaker amp have more driving power for SR-007 than my eXStatA as well, although not the detail and extension of the dedicated stat amp.
 
I'd probably take $225 on each stock pro-bias Stax box, but will never sell the audiocats modded one.  It's pretty close to the Woo WEE right now.

 

[Clarkmc2]

I'm not saying the old equipment is bad; just that the improvement is desirable. But if you see the old Stax board in there and compare it to Spritzer's, it is like a broken bar stool as compared to a Chippendale desk.
 
The "Spritzer Board" was designed and built by member Spritzer. He was kind enough to sell off the spares. He designed another version with an LED driver; I heard it at the 2010 Chicago meet. I do not think he produced it in quantity.
 
The board replaces the rudimentary bias supply circuit of the original Stax boxes and is a big improvement in that area. It also eliminates the thermistors. That improves the sound but removes some circuit protection as well. I am more than willing to live with the trade. The other modification is to improve the quality of the wiring and connections. I chose to simplify the wiring by leaving off the connections to the speaker terminals altogether. Just use the bundled cabling coming in from the amp and hook the leads directly to the transformers, and the transformers directly to the sockets. The pin out scheme can be found http://gilmore2.chem.northwestern.edu/projects/gilmore_prj.htm in Kevin Gillmore's project on the old Headwize site. I use the selector switch for AC on/off only.
 
And yes, it requires an AC source. Edit: Maybe not. See Spritzer's post #16286.
 
If any of this is possible without the bias boards, I don't know. I have converted three boxes, two for friends. My apologies if I have misstated any technical information. I have never designed anything.

 

[HeadphoneAddict]

Quote:

So you're all saying that my unmodified SRD-7/SB is really holding these Lambdas back? (Possibly moreso than the TX-SV515PRO I had lying around to drive them with?) They're already a noticeable improvement over the AD700s; how much better does it get?
 
I don't think those Spritzer boards are in production anymore, which will complicate things severely. Why did they go out of production, anyway? Too much cost? Even then, do they require external AC power (making it incompatible with my transformer unit), or are they self-biasing?
 
In terms of rewiring these things, I'm hearing different opinions. Some say to just connect the speaker terminals to the transformers, then the transformers to the headphone sockets, bypassing the PCB altogether. What I'm hearing here suggests to bypass just the earspeaker/loudspeaker switch, from the sound of it. Even then, it would help if I simply knew what wires off the transformers to solder where without having to study the PCB first, though it's probably a good idea to study the PCB and the schematics anyway.

I think Spritzer just made the boards for fun, not as a business.  
 
I thought the Lambdas sounded pretty good from an SRD-7 SB, but out of a budget vintage Stax amp like the SRM-1 Mk2 Pro they were a bit better.  The transformers offer good dynamics and punch, but the sound is a little veiled with them vs a dedicated stat amp.  I still thought that an 8-watt amp with transformer and SR-Lambda could compete with an HD600 on a Woo WA6.
 
My eXStatA with normal bias Lambdas is an excellent match, beating out the transformers as well.  Where I see the transformers being a bonus is when you need a lot of power for an SR-007 or HE-60 and can't afford a $1500 - $5000 stat amp to drive them.  But even via an underpowered $1500 Woo GES the SR-007 at moderate volumes will sound much better than using a stock Stax transformer on a $2500 speaker amp like my ZDT.
 

 

[cjfrbw]

 I have been using 300b amps with 7SB and one of Spritzer's pro mod 7 types. Currently, I have a Lambda normal bias, SR 3/5n driver normal bias, and a  current 507 pro bias. The result has been utterly hypnotic with all three.  I think more edge definition and crispness would actually deter some from the magical effect.

Most of the chatter here tends to support the direct amps rather than transformer coupling, but I have also noted that  there is a minority population Stax users that would ONLY use transformer coupling with high quality speaker amps. Good transformer coupling enhances tone, musical flow and fullness.


I suppose it ultimately comes down to listening preferences and taste. One must try as many as possible and choose.

 

 

[milosz]

RE:  Stax "energizers"
 
This is all very interesting.  I still haven't gotten around to trying my Stax SRM-7pro  box, but I am now more anxious to try it on various tube and solid state amps, I'm really glad I bought it.
 
I really liked the results I got from using my (planar) HiFiMan HE-6's on various amps.  So I know there is some fun, and good listening, to be had trying different "speaker" amps with headphones.  For me, this hobby is equal parts joy of listening and fun of playing around with the gear, building stuff, etc.  I get great pleasure out of both aspects.
 
Doesn't Woo also make an "energizer?"  How does it compare to the Stax?
========================================================================
 
This "Spritzer board" - anyone got a schematic for it?
 
For the heck of it, here is the inside of a Stax SRM-7
 

 

[Beefy]

 
Quote:

Originally Posted by HeadphoneAddict /img/forum/go_quote.gif
 
My eXStatA with normal bias Lambdas is an excellent match, beating out the transformers as well.
 

I concur with this. My SR-Lambda sound much better out of an Exstata than through an SRD7-SB fed by either my M3 or a t-amp.
 
Now admittedly I don't have what most would consider a suitable high-end speaker amp to try with these, but the M3 is a great sounding amp and can certainly handle the transformer load - and the difference is pretty substantial.

 

[oso]

Hello everybody
 
I can read everywhere that the stax srm727 is badly designed, bad sounding and non linear. However, I can't find a post with measures demonstrating or explaining this in details. It is said that the design is bad, but in what does it differ from the 717 for example?
 
thank you very much to indicate me interesting links about it
 
All the best
 
olivier

 

[spritzer]

The 727 isn't badly designed, in fact it is quite a nice design and makes 99% of "dynamic" amps look like the cheap toys they really are.  Stax did make an unfortunate change to the design by shortening the feedback loop and leaving the last stage out of it.  Ramp up the output stage bias and you could get away with this but in this setup it doesn't work.  Distortion is an order of magnitude higher and the sound signature is clearly non linear. 
 
Good luck finding any measurements since we never post this stuff.  Why bother since most people can't understand it anyway... 
 
As for the Pro bias adapter boards, I did make these out of necessity since the Pro bias transformers were fetching silly prices and there was an abundance of very cheap normal bias units out there.  Four versions later and it is about as good as a bias supply can be while still being able to cram it into a SRD-5. 

  I do still have about a dozen units left so if anybody needs one just PM me.  The boards are assembled so you just need to install it in the chassis.  These also work with non Stax transformers should you want to experiment. 
 
As for running these in a non AC powered box, I've never tried it but I can't see any reason why it wouldn't work.  I've certainly used this design in tiny SB units I built so it shouldn't be a problem. 

 

[oso]

Quote:

The 727 isn't badly designed, in fact it is quite a nice design and makes 99% of "dynamic" amps look like the cheap toys they really are.  Stax did make an unfortunate change to the design by shortening the feedback loop and leaving the last stage out of it.  Ramp up the output stage bias and you could get away with this but in this setup it doesn't work.  Distortion is an order of magnitude higher and the sound signature is clearly non linear. 
 
Good luck finding any measurements since we never post this stuff.  Why bother since most people can't understand it anyway... 
 
. 

Thanks for your answer. So it's all in the feedback design (claimed as a enhancement in Stax adverts!). Why did they do that???
 
If you have these measurements somewhere, please do not hesitate, and comparisons with references such as 717 or KGSS should be really interesting!
 
Olivier
 

 

[Amarphael]

I'm considering picking up the SRS-005A system from seyo-shop, seems like a nice deal... couple of questions:
 
- What would be a good power adapter for 230V?
 
- Is the 252S markedly improved from the 252A, and can the latter be brought "up to spec" or is it a different circuit?

 

[svyr]

I'm considering picking up the SRS-005A system from seyo-shop, seems like a nice deal... couple of questions:
 
- What would be a good power adapter for 230V?
 
- Is the 252S markedly improved from the 252A, and can the latter be brought "up to spec" or is it a different circuit?

from the spec pages the only difference is S has 4db higher gain (but the same max output voltage).I think there's also a review of a guy comparing both somewhere on head-fi. You could try get him to open the units and take a pic, if he didn't do an in shop comparison. or ask spritzer, he might know ...

From memory 12v, 0.4A+, regulated switching wall-wart with a center pin as - .

There are at least two threads on the topic:



http://www.head-fi.org/forum/thread/441597/stax-basic-system-power-adaptor-eu#post_5963306

http://www.head-fi.org/forum/thread/210476/srm-252-power-supply

 

[RockCity]

I wonder what Spritzer thinks of the 404LE. I've been comparing them back and forth with the O2's and they are surprisingly good.