The Stax Thread III
Apr 13, 2019 at 1:30 PM Post #17,521 of 21,668

Sound Eq

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I will say that a Mjolnir Audio SRD-7 estat transformer + quality stereo amp of choice and a little bit of EQ is a great setup for an SR-007 Mk2 (and L300 Limited) if you are trying to keep costs down. Since the amp is the main driving force behind the sound you will be getting from the estats, just a matter of getting one that suits personal taste. There are many stereo amps available compared to Estat specific amps...much easier to find a lower cost, warm leaning high quality stereo amp.
thanks, that could be an option as well, i am still waiting for a member here to compare iesl with his upcoming carbon,

is the srd7 different from iesl
 
Apr 13, 2019 at 5:38 PM Post #17,524 of 21,668

JimL11

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The GES is based on Kevin Gilmore's all triode amp, which was one of his first designs. When he designed his KGSS, he felt it sounded better (with the SR-007 Mk I, which was the top of the line at the time) than his all triode amp. The KGSSHV and KGSS Carbon are advances on the original KGSS. The problem with the GES and the Stax tube output amps is they all use plate resistor outputs. All the Stax solid state amps and all the modern Gilmore amps including the KGST use current source loads, which more than doubles the effective output power of the amp because they are not wasting the majority of their power heating up the output resistors. In fact, just taking the SRM-T1, which is basically the same circuit as the 006 and 007, and replacing the output resistors with good cascode MOSFET current loads kicks it up to being able to drive the SR-007 adequately for most people. The modified T1 is essentially a lower power version of the KGST (6CG7 rather than 6S4A output tubes), but lacking the regulated power supply of the KGST.

IMHO, a modified T1 is the least expensive way to get an amp that will drive any Stax headphone - the cost is basically that of a used T1, plus another $100 in parts, which includes the cost of replacing all the power supply electrolytic capacitors, which needs to be done in an amp that is more than 25 years old anyway. If you don't want to DIY, any repair technician should be able to do the modification with a few hours work. If you already have an SRM-007, modifying it with current sources in place of its plate resistors will significantly improve its bass and high end, along with its ability to drive the 007.

Unlike @antimatter, I feel an SRM-727 with global feedback mod is capable of driving the SR-007, although I prefer the sound of a modified T1 - I had both, and sold the modified 727.

As I have mentioned elsewhere, an SRX Plus is also a reasonably inexpensive amplifier that will drive any Stax headphone, however it is a DIY only design. It does have that tube tonality with very little of the stereotypical tube defects of soft bass and highs.

Using the Stereophile ranking system, the SRX Plus would fit in class B along with the KGSSHV and KGST, while consensus class A amps would be the Carbon, BHSE, GG and Megatron, with many placing the T2 in class A+.

There are a couple people (e.g. spritzer) who would put the T2 in class A with the other KG amps, and a few people who would rank the SRX Plus in the same category as the BHSE, but what I have written in the previous paragraph is what seems the most prevalent opinion.

Finally, it should be noted that with amps which are predominantly DIY, there may be small differences due to parts selection, and differences due to choice of regulated power supplies. Kevin Gilmore has designed several regulated power supplies of varying complexity and performance. KGSS Carbons often are built with his most sophisticated Golden Reference supplies, whereas the less costly KGSSHV and KGST are more commonly built with one of his lesser supplies, which may enhance the differences in performance between, say, a small KGST with a simple regulated supply versus a large KGSS Carbon with Golden Reference HV and LV regulated supplies.
 
Apr 13, 2019 at 5:56 PM Post #17,525 of 21,668

Sound Eq

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The GES is based on Kevin Gilmore's all triode amp, which was one of his first designs. When he designed his KGSS, he felt it sounded better (with the SR-007 Mk I, which was the top of the line at the time) than his all triode amp. The KGSSHV and KGSS Carbon are advances on the original KGSS. The problem with the GES and the Stax tube output amps is they all use plate resistor outputs. All the Stax solid state amps and all the modern Gilmore amps including the KGST use current source loads, which more than doubles the effective output power of the amp because they are not wasting the majority of their power heating up the output resistors. In fact, just taking the SRM-T1, which is basically the same circuit as the 006 and 007, and replacing the output resistors with good cascode MOSFET current loads kicks it up to being able to drive the SR-007 adequately for most people. The modified T1 is essentially a lower power version of the KGST (6CG7 rather than 6S4A output tubes), but lacking the regulated power supply of the KGST.

IMHO, a modified T1 is the least expensive way to get an amp that will drive any Stax headphone - the cost is basically that of a used T1, plus another $100 in parts, which includes the cost of replacing all the power supply electrolytic capacitors, which needs to be done in an amp that is more than 25 years old anyway. If you don't want to DIY, any repair technician should be able to do the modification with a few hours work. If you already have an SRM-007, modifying it with current sources in place of its plate resistors will significantly improve its bass and high end, along with its ability to drive the 007.

Unlike @antimatter, I feel an SRM-727 with global feedback mod is capable of driving the SR-007, although I prefer the sound of a modified T1 - I had both, and sold the modified 727.

As I have mentioned elsewhere, an SRX Plus is also a reasonably inexpensive amplifier that will drive any Stax headphone, however it is a DIY only design. It does have that tube tonality with very little of the stereotypical tube defects of soft bass and highs.

Using the Stereophile ranking system, the SRX Plus would fit in class B along with the KGSSHV and KGST, while consensus class A amps would be the Carbon, BHSE, GG and Megatron, with many placing the T2 in class A+.

There are a couple people (e.g. spritzer) who would put the T2 in class A with the other KG amps, and a few people who would rank the SRX Plus in the same category as the BHSE, but what I have written in the previous paragraph is what seems the most prevalent opinion.

Finally, it should be noted that with amps which are predominantly DIY, there may be small differences due to parts selection, and differences due to choice of regulated power supplies. Kevin Gilmore has designed several regulated power supplies of varying complexity and performance. KGSS Carbons often are built with his most sophisticated Golden Reference supplies, whereas the less costly KGSSHV and KGST are more commonly built with one of his lesser supplies, which may enhance the differences in performance between, say, a small KGST with a simple regulated supply versus a large KGSS Carbon with Golden Reference HV and LV regulated supplies.


thats so beneficial to read, thanks so much, somehow i am leaning to kgst, would its sound signature be similar to 007tii, but with more power am i right

i have both 323s and 007tii and i like the sound of the 007tii better with my 007mk2.

i dont know which is more powerful the 323s or 007tii, but i feel i have to turn the volume higher on 007tii than with 323s with my 007mk2, which is strange as the 323s is very cheap in comparison

so if we take the sound signature of my tube 007tii i am really fine with bass mids and details and I am not asking for more, its just I aim for more head room, thats all, although on the dial of my 007tii i barely go over 60-70% volume
 
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Apr 13, 2019 at 6:38 PM Post #17,526 of 21,668

buzzlulu

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SS Carbons often are built with his most sophisticated Golden Reference supplies, whereas the less costly KGSSHV and KGST are more commonly built with one of his lesser supplies, which may enhance the differences in performance between, say, a small KGST with a simple regulated supply versus a large KGSS Carbon with Golden Reference HV and LV regulated supplies.

I believe Birgir's Carbons (Carbon and CC) use his own versions of the HV and LV supplies (?) I have his "regular" Carbon. I wonder how it compares (with his own power supplies) to a Carbon utilizing the Golden Reference ps's?
 
Apr 14, 2019 at 2:11 AM Post #17,527 of 21,668

JimL11

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thats so beneficial to read, thanks so much, somehow i am leaning to kgst, would its sound signature be similar to 007tii, but with more power am i right

i have both 323s and 007tii and i like the sound of the 007tii better with my 007mk2.

i dont know which is more powerful the 323s or 007tii, but i feel i have to turn the volume higher on 007tii than with 323s with my 007mk2, which is strange as the 323s is very cheap in comparison

so if we take the sound signature of my tube 007tii i am really fine with bass mids and details and I am not asking for more, its just I aim for more head room, thats all, although on the dial of my 007tii i barely go over 60-70% volume

The KGST should be the closest of the Gilmore amps to the 007 as the circuits are very similar, in fact as I recall, spritzer once described the KGST as the 007 if built with no commercial considerations, i.e. with more powerful tubes, constant current sources instead of plate resistors and regulated power supply in place of a passive one.

If you look at Tyll's review of the 007 on InnerFidelity (https://www.innerfidelity.com/conte...nd-great-headphone-amplifiers-stax-srm-727tii) you will note that he finds that at higher listening levels, the 007's bass becomes "wooly" and the treble becomes "glary." The KGST should fix these issues, which are likely due to the plate resistors in the 007 burning up signal current.
 
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Apr 14, 2019 at 2:37 AM Post #17,528 of 21,668

JimL11

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thanks, that could be an option as well, i am still waiting for a member here to compare iesl with his upcoming carbon,

is the srd7 different from iesl

The SRD7 is the same concept as the iESL (both using a transformer to boost the voltage), but there may be some small differences due to the exact transformer used. Also, the SRD7 was made for normal bias Stax headphones (200-230VDC), whereas all the modern Stax headphones are Pro bias (580VDC). Stax did make an SRD7 MkII, also known as the SRD7 Pro, but those are relatively uncommon and usually more expensive. However IIRC they are not nearly as expensive as the iESL. All the Stax converter boxes are obsolete as Stax apparently decided that dedicated amps was a better way to go.
 
Apr 14, 2019 at 3:43 AM Post #17,529 of 21,668

JimL11

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Never laid eyes on one so I have no idea how it sounds. However, I note that it draws 60 watts quiescent and 100 watts full load. This suggests that it may run in class AB, as class A amps have a constant power draw independent of load. All the other electrostatic headphone amps I am aware of run in class A. The Audiovalve Luminaire uses 4 PCL805 tubes so that is 21 watts of filament power which is used to heat the tubes. That leaves us with 39 to 79 watts used by the amp to power the headphones. Now class AB amps run in class A for lower powers so it is likely that the class A part of of its operation goes to about 39 watts.

By comparison, the Stax amps are specified as drawing between 30 (323) and 46 (727) watts, the measured line draw of one Carbon was 92 watts, and a Blue Hawaii SE is specified 180 watts. Note however that 40 watts of the Blue Hawaii power draw is due to its tube filaments. This suggests that the potential power of the Audiovalve is in the same ballpark as the Stax amps but not comparable to the Gilmore amps.

Finally, note that the Audiovalve uses a step-up transformer output for its electrostatic output and a step down transformer for its low impedance outputs. This increases its versatility at the cost of, well, greater cost, weight and size. And although the manufacturer claims that there are no compromises, IMO it is difficult enough to design a no compromise amplifier for one type of headphone, let alone three types with very different drive requirements. It seems to me that unless you simply must have only one amplifier to use with dynamic, planar and electrostatic headphones, it is better and potentially less expensive to have a dedicated amplifier for electrostatic headphones and a separate one for dynamic and planar headphones.


I believe Birgir's Carbons (Carbon and CC) use his own versions of the HV and LV supplies (?) I have his "regular" Carbon. I wonder how it compares (with his own power supplies) to a Carbon utilizing the Golden Reference ps's?

Yes, I believe his mini chassis builds use a version of the original Blue Hawaii regulated power supply, which is a pretty basic series regulated supply, using a MOSFET sitting on top of a zener string driven by a constant current source as the voltage regulator. I believe he has stated that he doesn't find that much difference between regulated power supplies, so he prefers to build amps with more compact form factors - in fact they are often smaller than the current Stax amps which don't have any regulated power supplies at all. Note that Stax have made a similar decision for commercial reasons - they evidently don't feel that a regulated power supply is worth the additional cost, complexity and size in terms of commercial sales. Don't know what he uses for the CC Carbon, but it may be a version of the Golden Reference regulated supply using his own PCB design.
 
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Apr 14, 2019 at 11:46 AM Post #17,530 of 21,668

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Don't know what he uses for the CC Carbon, but it may be a version of the Golden Reference regulated supply using his own PCB design.

I am pretty sure that around the time he started on the CC he stated exactly this in regard to the HV supply. I don't believe he has commented on the LV.

He has also said that the version of the amp board in the DYI carbon is an early design, which he has continued to develop and refine since.
 
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Apr 14, 2019 at 11:52 AM Post #17,531 of 21,668

Sound Eq

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what is so strange, and with all respect to all builders, but if one man show builders can build better amps than stax, then what the hell is stax doing who run a company and have more resources, that is just strange, that they make these headphones, and have no great amps to let people audition them with.

that is just strange, as stats are a niche segment, so its not like you can plug your headphones into so many different amps from other companies
 
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Apr 14, 2019 at 12:02 PM Post #17,532 of 21,668

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what is so strange, and with all respect to all builders, but if one man show builders can build better amps than stax, then what the hell is stax doing who run a company and have more resources, that is just strange, that they make these headphones, and have no great amps to let people audition them with.

that is just strange, as stats are a niche segment, so its not like you can plug your headphones into so many different amps from other companies

it was stated before, the BOM to build a carbon or any of these tier1 amps after marketing, distribution, markups, etc etc would be prohibitively expensive if it was commercialized. Btw, you aren't limited to just these amps if you go the energizer route.
 
Apr 14, 2019 at 12:08 PM Post #17,533 of 21,668

SeaWo|f

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it was stated before, the BOM to build a carbon or any of these tier1 amps after marketing, distribution, markups, etc etc would be prohibitively expensive if it was commercialized. Btw, you aren't limited to just these amps if you go the energizer route.

This in addition to mistakes in the design and packaging of the orginal SRM-T2 almost sunk Stax.
 
Apr 14, 2019 at 12:13 PM Post #17,534 of 21,668

Sound Eq

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it was stated before, the BOM to build a carbon or any of these tier1 amps after marketing, distribution, markups, etc etc would be prohibitively expensive if it was commercialized. Btw, you aren't limited to just these amps if you go the energizer route.

totally agree, awaiting your feedback and comparisons with ifi iesl as well
 
Apr 14, 2019 at 1:08 PM Post #17,535 of 21,668

JimL11

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I am pretty sure that around the time he started on the CC he stated exactly this in regard to the HV supply. I don't believe he has commented on the LV.

He has also said that the version of the amp board in the DYI carbon is an early design, which he has continued to develop and refine since.

Yes, that was my impression also.

what is so strange, and with all respect to all builders, but if one man show builders can build better amps than stax, then what the hell is stax doing who run a company and have more resources, that is just strange, that they make these headphones, and have no great amps to let people audition them with.

that is just strange, as stats are a niche segment, so its not like you can plug your headphones into so many different amps from other companies

Not really that strange. As mentioned above, Stax got burned by their T2 experience, which sunk the company. The current Stax was re-formed after bankruptcy. They have focussed on commercial viability, so, for example, there is a benefit to using regulated supplies, but the extra cost and size may not be justified in a commercial amp. Consider that parts cost (including chassis) is only about 20% of the price of an amp.They have also chosen to use, until recently, a relatively small chassis, as larger, heavier amps are more expensive to ship. Also, Stax has mostly focussed on the Japanese market. The vast majority of that market is likely unaware of the existance of third party amps.

A single builder does not have to worry about pricing in distributor costs and profit, dealer costs and profit, shipping multiple units to different parts of the world, paying a decent wage to its workers, withstanding changes in the world economy, etc. Kevin Gilmore designed his amps without much consideration of commercial costs - if he can do 5% better by spending 50% more he will do it - a company that is in business to make money will not. Another example: the KGST is designed to use a tube that is no longer in production. No commercial company can do that.
 

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