STAX vs KOSS amp
Jun 7, 2015 at 5:13 PM Thread Starter Post #1 of 11
luvmusik

luvmusik

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KOSS E/90 amp vs STAX SRM-212 amp for driving KOSS ESP950 headphones advice needed. These are the 2 drive units I have, but before trying the SRM-212 with the KOSS need to know if OK to do (I think for this amp the STAX Pro Bias voltage is OK with the KOSS ?), and if either of these amps are better or fairly equal in sonics when matched to the KOSS cans ?
 
Has anyone tried these 2 particular amps, and what difference in sound were noted ? Realize the adaptor cord is needed for the KOSS cans with the STAX amp, but does anything else need to be done for them to work together ? The STAX amp is a strong build, but is it fairly close, equal or way above the E/90 sonically, before I try it ? Does running the KOSS cans with this STAX amp pose any danger for any type of damage to anything - cans, amp, or hifi source amp ? If the sound comparison is really close, maybe it's not worth the adaptor price, or maybe I can make my own adaptor by finding the male-pin part.
 
 
 
Jun 9, 2015 at 2:09 AM Post #3 of 11
I had the Koss phones for many years and ran them off a Stax SRM3 with no problems.  I do not see why the amp you are considering would create difficulty.  And the Stax amp gave a good deal more clarity than the Koss amp.  However, you might consider using a better power supply for the Koss amp, as opposed to the  transformer it comes with. I my experience a better power supply and even a power cord pays off in sonic dividends.
 
Jun 9, 2015 at 2:46 AM Post #4 of 11
Thanks, good advice, I had not thought about the power supply and power cord; it makes good sense and can make a difference in sound.
 
With the KOSS ESP950 flagship, the matching E/90 energizer is sonically below the great STAX amp designs, and KOSS could've made a better box unit for such great headphones. The STAX SRM-3 amp is a really nice performer - that is a nice combo with the KOSS !
 
Do you think because the STAX SRM-212 amp (Basic System II) was the lowest entry-level amp they had during that period it would still outperform the humble E/90 ? I'm hoping so, but maybe it is near even or close, but hoping it is way better than the E/90 sonically ? I already have this STAX amp & may experiment, but need to get the adaptor cable. If the sound will improve I would buy the adaptor, and I think they go around $150. I am biased to thinking the STAX will improve the sound, but maybe because it's only a SRM-212, the difference may be negligible, not worth pursuing...thus, the decision to make ! I'm stuck deciding, but guess I could always sell the adaptor or keep it for a someday better STAX amp grab to make it worthwhile.
 
Jun 9, 2015 at 3:28 AM Post #5 of 11
luvmusik said:
  Thanks, good advice, I had not thought about the power supply and power cord; it makes good sense and can make a difference in sound.
 
With the KOSS ESP950 flagship, the matching E/90 energizer is sonically below the great STAX amp designs, and KOSS could've made a better box unit for such great headphones. The STAX SRM-3 amp is a really nice performer - that is a nice combo with the KOSS !
 
Do you think because the STAX SRM-212 amp (Basic System II) was the lowest entry-level amp they had during that period it would still outperform the humble E/90 ? I'm hoping so, but maybe it is near even or close, but hoping it is way better than the E/90 sonically ? I already have this STAX amp & may experiment, but need to get the adaptor cable. If the sound will improve I would buy the adaptor, and I think they go around $150. I am biased to thinking the STAX will improve the sound, but maybe because it's only a SRM-212, the difference may be negligible, not worth pursuing...thus, the decision to make ! I'm stuck deciding, but guess I could always sell the adaptor or keep it for a someday better STAX amp grab to make it worthwhile.
Click to expand...

Whoa $150 for an adapter. I made my own using the extension cord which came with the Koss. I included it when I sold the Koss phones.
 
Jun 9, 2015 at 4:01 AM Post #6 of 11
Yes, it is something when the sellers are pricing such a simple thing so high. I guess they are charging for their labor time; the male pin part is peanuts, and only the cord type needs to be matched for electrostatic use. Probably not a big seller either. I'm not sure how much cable length they provide - that may increase cost.
 
There have been some fellows selling just the male pin part I believe, maybe that's how you also were able to construct one and I may go that route. I may want to find an extra short cord, as the Koss I think is only 4 ' plus 6' for only 10 feet total, and still want the versatality to switch between the SRM-212 and the E/90 to compare. So, I would make a seperate short adaptor cable.
 
That's cool that you included your adaptor with your system when selling it -good guy ! It gave the next owner a jump up right away for STAX amp use !  Hope a Head-Fi'er got 'em !
 
I think for KOSS, maybe all electrostatics ( ? ) that the cord length overall is "tuned" to the system, so to speak for optimum transmission and to alleviate any loss in signal. I may be wrong there. I think if the stat cord is really excessively long, the system may either not attain volume or change the resistance for possible damage to the system. Again I may be wrong, but I believe KOSS will not lengthen their factory-specified stat cord length ( ? 10 feet total ? ), even if someone requests it. It may also be why their site doesn't display extra stat cables for sale. But, if a repair is needed they will renew the cord from their repair center. I could be way off base on this, but kinda think it may work this way.
 
That said, I wonder if it is OK to run a double length STAX extension cable with an all-STAX system ? The standard is 15 feet I think, I never measured them here (have 2 or 3).  Putting 2 together then goes 30 feet, but maybe that is not advised. Huh, just wondering, maybe it is OK. I dunno, never looked into it.
 
Jun 9, 2015 at 4:39 AM Post #8 of 11
Koss does not make an headphone amp, they make energizer boxes. Stax makes headphone amps and energizers. 
 
Jun 10, 2015 at 12:41 AM Post #10 of 11
The E/90 certainly is an amp. KOSS points that out in the owners manual, and previous post is right on. Fotos abound of the inside components.
 
The confusion is that KOSS also uses nomenclature of - E/90 Energizer/Amplifier, which clouds the understanding. In thread I used both KOSS terms, so no intention to mislead if so taken.
 
True also, 2 posts back, STAX makes/made amps for electrostatic in either normal or higher voltage pro bias & can also be used on electret/electrostatic when matched. STAX also made energizers, sometimes called adapters, for electrostatic & electret/electrostatic in either normal or pro bias versions when matched. Some of all of these types of boxes were specific to certain model headphones, many were inter-changeable when properly matched.
 
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