[JimL11]

To elaborate a bit, I would say the only time that voicing an amp makes sense is for an active speaker, where the amp and speaker are designed as a unit so the amplifier(s) can compensate for any shortcomings of the drivers, contouring frequency response and doing active crossovers..  There have been a number of them over the years: the Powered Advent, the Meridian M1, etc., but most of them have not been great commercial successes, at least in the home hi fi market, as the number of active speaker manufacturers could probably be counted on the fingers of both hands, or maybe just one hand.  I am leaving headphones out of it because AFAIK, nobody has even attempted to design an active amp/headphone system where the headphone can only be used with its dedicated amp (possibly the new Sennheiser stat phone is an exception but AFAIK if you've got the right socket you could run it with a BHSE).
 
I am not quite advocating the late Peter Walker's position that all properly designed amps running within their limits sound the same, but I would argue that the differences between amps are relatively small, and the differences between samples of the same amp design are at least as likely to be inadvertent (random parts variations) as deliberate.
 
Now if you want to try "voicing" an amp for your particular source and transducer, it would seem to me that a tube amplifier is the way to go, as tubes of the same type from different manufacturers may sound different and can easily be unplugged and replaced (i.e. tube rolling), whereas with a solid state amp everything is soldered in place so unless you go in for desoldering and soldering in different transistors and resistors you're kind of stuck with what you have.  Personally I'd rather listen to music, but to each his own.

 

[paradoxper]

I'd say semantics. I agree about 'voicing'. I believe the designs are intended to be transparent, however, the 007 surely was optimized with the then KGSS, HV, BH, T2. Likewise, it was planned (at least at some point) to have the Carbon be optimized with the 009. 
 
I'd rather prefer we substitute the term voicing with gimping so we understand the true context.

 

[dharma]

  I have spent about 2 hours with the following gear:
 
(Energizers)
Stax SRM-007t II
Stax SRM-353X
Nebuchadnezzar:  http://knob.planet.ee/amps/staxneb1/staxneb1.htm
(I will call it Nezzar for shorter name).
 
(Ear speakers)
Stax SR-L500
Stax SR-L700
Stax SR-007 Mk 1 (modified)
Stax SR-007 Mk II
Stax SR-009
 
Thanks to Audelec (http://www.audelec.fi) for the opportunity. The reason I went there was to hear Erik Konka's Nezzar amp, compared to some Stax amps I know. The Nezzar has recently been reviewed in a Finnish Hi-Fi magazine, and the test unit was still lingering there before going back to Estonia, so I took the opportunity.
 
Disclaimer: I have no interest, nor conflict of interest and no financial gains in doing this short review.
 
[...]Of course you get what you pay for, the 009 is more exact, has yet fuller midrange, and better stage, but still, you're not losing much music with the L700. Especially when going from the 353X to the SRM-007t II, or even better, the Nezzar. If you are contemplating the L700, I think the Nezzar would make the best synergy from the amps above. [...]  
The 007t II is like a more harmonically rich 353X, and the Nezzar is somewhat richer and perhaps a bit more refined than the SRM-007t II. The 353X is not much behind these two, though, but the difference is there. The Nezzar makes the 009 sound really sweet and musical, with nicely layered stage and powerful, resolving bass.
 
[...] I don't know if the Nezzar is among the best amps for the notoriously difficult 007 Mk1, but I was happy how it has driven it -- let's call it sufficiently powerful. Again I could not decide if I liked the 009 or the 007 Mk1 more. Each had their strong sides, and no weak sides really.
 
Anyway the end of the story is that I was quite happy with the Nezzar, reminding me to Leben sound signature: highly musical, resolving, nice layered sound stage, rich in harmonics, yet closer to neutral than to being warm. I'd give it that I liked it more than the SRM-007t II, though for such statement a lot more testing would be needed.
Note that the Nezzar unit I tested looked more like a prototype, but I understood that production versions are on the way. I don't know the exact price, but AFAIK it is quite reasonable. Well done.

 
 
CUSTOM AUDIO 'NEBUCHADNEZZAR' seems to have great sound (mentioned audio-test in Finnish HiFi magazine was made by notoriously critical grand-oldman of Finnish HiFi society). In magazine, it was mentioned, that it is about 1000 euro cheaper than other comparable amps. To whom You suggest to have it (as first or second 'serious' amp, etc..)?

 

[martin778]

Can I install ECC88 / E88CC / 6922 / 6DJ8 in an SRM006tS without risking a meltdown of either the amp or the tubes?
 
(Personally I don't think so but I just want to be sure).

 

[zolkis]

 
CUSTOM AUDIO 'NEBUCHADNEZZAR' seems to have great sound (mentioned audio-test in Finnish HiFi magazine was made by notoriously critical grand-oldman of Finnish HiFi society). In magazine, it was mentioned, that it is about 1000 euro cheaper than other comparable amps. To whom You suggest to have it (as first or second 'serious' amp, etc..)?

 
I'd recommend it over any Stax-labeled amps except the T2, especially at the price, and the number of options one can negotiate directly with Erik (e.g. normal or Pro sockets, balance, volume controls etc). If someone contemplates the 353X, should already definitely consider this one instead. At its price, I think it may give a good run for money to at least some of the KG amps as well, though I have not yet managed to make direct comparisons.
 
Of course until someone like Tyll and/or a sufficiently large number of educated head-fi users have tested it, this is still unreliable basis of comparison. However, I am sure this is not a budget amp at all: it has high-end sound with a bit of hand-made 'bouquet' on the finish level, but I guess few people would mind that, given the record cheap price for this level of sound quality. And this trend will continue: in about a month or two I will also get another new high-hopes Stax amp from Europe. Good times for Stax lovers.

 

[dharma]

   
I'd recommend it over any Stax-labeled amps except the T2, especially at the price, and the number of options one can negotiate directly with Erik (e.g. normal or Pro sockets, balance, volume controls etc). If someone contemplates the 353X, should already definitely consider this one instead. At its price, I think it may give a good run for money to at least some of the KG amps as well, though I have not yet managed to make direct comparisons.
 
Of course until someone like Tyll and/or a sufficiently large number of educated head-fi users have tested it, this is still unreliable basis of comparison. However, I am sure this is not a budget amp at all: it has high-end sound with a bit of hand-made 'bouquet' on the finish level, but I guess few people would mind that, given the record cheap price for this level of sound quality. And this trend will continue: in about a month or two I will also get another new high-hopes Stax amp from Europe. Good times for Stax lovers.

OK thanks... ... From capital of Finland Helsinki to capital of Estonia Tallinn it's about 80 km + 180 km to Tartu (second biggest city in Estonia). Not far for You to go and test some of Your hp's for longer than 2 hours??....

 

[joseph69]

Jim is right.

No, I wasn't saying Jim was wrong…I was saying I believe you should build your system around your preferred headphone. 

 

[soren_brix]

  I'd say semantics. I agree about 'voicing'. I believe the designs are intended to be transparent, however, the 007 surely was optimized with the then KGSS, HV, BH, T2. Likewise, it was planned (at least at some point) to have the Carbon be optimized with the 009. 
 
I'd rather prefer we substitute the term voicing with gimping so we understand the true context.

You really seem to know your stuff.
Can you please shed some light on how the various amps was "optimized"?

 

[paradoxper]

  You really seem to know your stuff.
Can you please shed some light on how the various amps was "optimized"?

Your sarcasm is poor.
 
Perhaps KG can provide his thoughts on how he develops his designs. One aspect I'd see as optimized would be voltage requirements or
looking at the output stages. 
 
I also find it interesting how Birgir always felt the 009 had faults and in that, the Carbon was posed as a solution. Within that thinking,
I'm curious about the design choice in regards to 'voicing' the Carbon for the 009, or, er optimizing an amplifier with the 009 in mind.

 

[JimL11]

  I'd say semantics. I agree about 'voicing'. I believe the designs are intended to be transparent, however, the 007 surely was optimized with the then KGSS, HV, BH, T2. Likewise, it was planned (at least at some point) to have the Carbon be optimized with the 009. 

Um, actually no.  What you're saying is exactly the opposite of what I'm saying.  What I'm saying is that the 007 was NOT optimized for the KGSS, HV, BH or T2.  Those amps were designed to be as powerful and neutral as possible.  They were not designed to be optimal for the 007, they were designed to do the best job of driving any headphone.  Likewise the 007 was not designed to be optimal for the KGSS, HV or BH, all of which came out AFTER the 007.  To say that the 007 was optimized for those amps would be to say that Stax designed a phone to work best with amps that were not even in existence when it was designed, which is clearly ridiculous.  The 007 was designed to be the best phone that Stax could make.  Ditto with the 009, Stax designed it to be the best, but as we know, not everyone agrees that it is, at least tonally.  Likewise the Carbon was NOT designed to be optimized with the 009, it was designed to be the best solid state amp for stat headphones.  It was HOPED that it would work well with the 009 but it was not INTENDED to be optimal for it, except in the sense that the best amp gives any headphone the best chance to show what it can do, both good and bad.  For example, when the 009 first came out, spritzer reported that, in comparison with the KGBH and KGSS,  the best amp he had found for his 009s was the Stax SRA12, which is one of Stax's early solid state designs, even though as an amp it is not as good as the BH, T2, or even KGSS - a less-than-best amp's "voice" matched best with the "best" Stax headphone.  
 
The difference, in short, is this.  The notion of voicing is to design an amp to be optimal with a specific transducer.  This is as opposed to designing the best possible (i.e. most powerful and neutral) amplifier, which should do the best job of driving ANY transducer, but may or may not be the best match for any specific transducer.   What I am saying is that KG and spritzer's approach is the latter and NOT the former.  The two approaches are philosophically completely opposite.    Saying that's semantics is like saying that left vs right, up vs down and yes vs no is semantics.
 
Now, it may be that one amp designer's notion of what is neutral is different from another designer's, so one designer's amps may sound somewhat warmer, and another's more transparent, etc.  But that is different from saying an amp is voiced for a specific headphone or speaker.  And as I said, why would an amp designer limit his "market" by designing an amp for one speaker or headphone?

 

[JimL11]

  No, I wasn't saying Jim was wrong…I was saying I believe you should build your system around your preferred headphone. 

 
Yeah, I took your comment as agreeing with me.

 

[paradoxper]

  Um, actually no.  What you're saying is exactly the opposite of what I'm saying.  What I'm saying is that the 007 was NOT optimized for the KGSS, HV, BH or T2.  Those amps were designed to be as powerful and neutral as possible.  They were not designed to be optimal for the 007, they were designed to do the best job of driving any headphone.  Likewise the 007 was not designed to be optimal for the KGSS, HV or BH, all of which came out AFTER the 007.  To say that the 007 was optimized for those amps would be to say that Stax designed a phone to work best with amps that were not even in existence when it was designed, which is clearly ridiculous.  The 007 was designed to be the best phone that Stax could make.  Ditto with the 009, Stax designed it to be the best, but as we know, not everyone agrees that it is, at least tonally.  Likewise the Carbon was NOT designed to be optimized with the 009, it was designed to be the best solid state amp for stat headphones.  It was HOPED that it would work well with the 009 but it was not INTENDED to be optimal for it, except in the sense that the best amp gives any headphone the best chance to show what it can do, both good and bad.  For example, when the 009 first came out, spritzer reported that, in comparison with the KGBH and KGSS,  the best amp he had found for his 009s was the Stax SRA12, which is one of Stax's early solid state designs, even though as an amp it is not as good as the BH, T2, or even KGSS - a less-than-best amp's "voice" matched best with the "best" Stax headphone.  
 
The difference, in short, is this.  The notion of voicing is to design an amp to be optimal with a specific transducer.  This is as opposed to designing the best possible (i.e. most powerful and neutral) amplifier, which should do the best job of driving ANY transducer, but may or may not be the best match for any specific transducer.   What I am saying is that KG and spritzer's approach is the latter and NOT the former.  The two approaches are philosophically completely opposite.    Saying that's semantics is like saying that left vs right, up vs down and yes vs no is semantics.
 
Now, it may be that one amp designer's notion of what is neutral is different from another designer's, so one designer's amps may sound somewhat warmer, and another's more transparent, etc.  But that is different from saying an amp is voiced for a specific headphone or speaker.  And as I said, why would an amp designer limit his "market" by designing an amp for one speaker or headphone?

 
I have to think the flagships got a little special consideration. And perhaps I'm wrong in that thinking. Part of this stems from conversations I've had with Birgir. The Carbon may not have ended up being optimized for the 009 or any other headphone, but it was at one time the direction of the design, at least for one.
 

 

[soren_brix]

  Your sarcasm is poor.
 
Perhaps KG can provide his thoughts on how he develops his designs. One aspect I'd see as optimized would be voltage requirements or
looking at the output stages. 
 
I also find it interesting how Birgir always felt the 009 had faults and in that, the Carbon was posed as a solution. Within that thinking,
I'm curious about the design choice in regards to 'voicing' the Carbon for the 009, or, er optimizing an amplifier with the 009 in mind.

so basically you don't know, but are rather speculating.

 

[paradoxper]

  so basically you don't know, but are rather speculating.

Not exactly. 
 
http://www.head-fi.org/t/476891/does-anyone-else-think-the-stax-007-has-a-constricted-soundstage#post_6466437

 

[mulveling]

I don't believe that builders are actively "voicing" their amps to a high degree. That gets too far into the tweaky magic fuses/cables/footers sector of audiophillea for me, and this kind of thinking generally does damage to the hobby -- and it especially doesn't mix with the brand of no-nonsense DIY amp builders in the KG/Stax world. But the different amp designs and implementation configurations discussed here do sound meaningfully different; yes, even the good solid-state designs. And besides the major configuration choices, there are at least a few meaningful things to tweak that are within the builder's control -- e.g. mA bias, PSU size, etc.
 
But while we're on the topic of opinions/ideas that are hard to justify, it's always bugged me that parts of the Stax mafia were so eager/quick to ratify a "new" 009 version without (to my knowledge) having had multiple 009 units of different vintages on hand at any one time to evaluate. I've had 3 units in one place, and they all sound like the same 009 (I love them all) -- with accommodation for some sonic differences due to pad conditioning.