Wah! Mine is the "A" Series!

And of course the one on ebay is the "C" series, and is still hovering under $125 right now...

should i buy it and sell my old one? Hmm, nah - if the rig ain't broke why fix it, right? But thanks for the insight!

I remember auditioning the ED-1 diffuse field equalizer many years ago with an SRM-1 driver and Lambda Signatures. I can't understand why this device could be popular today on the used market. I remember trying it out on regular stereo recordings and most of the time it did very little to enhance the headphone experience. The imaging did not expand outward from its normal inside the head location. That's afterall the main reason for buying this equipment.

What it did do is to unfortunately add an extra veil of dirt and obscure the clarity of the music. I felt as if I was looking at the world through a dirty car windshield that hasn't been cleaned in a while. This might be due to the fact that the ED-1 basically contains a lot of equalization circuitry that involves passing the signal through capacitor and inductor reactive components. No matter how high the quality of those parts, there is guaranteed to be some degradation to the music signal. The best circuit design is the old expression
"straight wire with gain." Passing the signal through many reactive components is not a good idea.

Finally! Someone who agrees with me! Personally I feel the same way.

The C series is by far the best. If you get a chance to audition an A series side by side with a C series, the differences will be very easy to hear. Unfortunately, it really is that big. For someone looking for a used SRM-1, I would never recommend anything older than a C series. Unless someone is willing to personally modify the device and painstakingly upgrade the 30 or so resistors inside. (Lots of time and money).

Speaking of C series, I later found out that the highest serial numbers made by STAX before the SRM-1 was discontinued are the ones ending in the 6000 range (i.e. C6xxx). The 6000 range featured a further upgrade to the resistors which now go beyond the level of Roderstein. Unfortunately, I don't know for sure which new brand of resistor was used.

However, I clearly remember 10 years ago, when I was deeply involved in high end audio, I auditioned side by side a C5xxx with a C6xxx and I could hear a significant difference even between the two different C series M1's. The newer model had much less of that electronic haze/electronic texture that many people have reported when listening to the M1 driver. The differences between an A and C series is far bigger.

When buying an SRM-1 used, do yourself a favor and look for the C series serial number.

*reads the back of that ebay one*

"C5562" I think...hmm...bah, I'll stay pat until I see a C6xxx then. boy, you're evil!

I hear a lot complaints about the M1 driver having an electronic haze or glare to it or that it may sound too bright at times. I can hear this too very clearly when listening to my C series M1 when I use it straight from the box without any upgrades. I feel there is an easy way to reduce this effect and maybe even get rid of it.

I was given this upgrade tip by the old USA STAX importer. He said STAX designed the M1 with an undersized power transformer to try and save money. That means the transformer has to work very hard to up convert the USA AC line voltage of 117 to the much higher values used inside the electrostatic driver. The only AC voltages where that small transformer can work well are the much higher AC voltages used for the European market (220 and 240V).

He recommended buying an AC power transformer (110V to 220V) from an electronics store and running the M1 from the 220V side! It's easy to change the AC value on the back of the M1 by repositioning the "pull out" AC adaptor. This upgrade will help the undersized transformer inside the M1 to have an easier time generating the much higher voltages used in the driver stage. It now becomes much easier for the small transformer to do its job. Hence the sound will be much smoother and free of the electronic haze/glare many people complain about.

When I asked what power size AC transformer to buy, he said the bigger the better. I ended up paying about $90 for a 1000W model (110V to 220V AC adaptor). It weighs about 25 pounds! I took it home and from the first time I listened I could hear the big improvements he promised each time the AC voltage transformer was plugged in. The glare was gone, the excess brightness was gone. It's as if I had bought a brand new driver amp.
This is one of the most cost effective upgrade/mod I have ever made. The only downside is the increased electricity bill.

Not only does the STAX SRM-1 driver sound much better when operated at the higher AC voltages found in Europe. But, loudspeaker power amplifiers in general sound better when operated at the higher European voltages. This makes sense since the power transformer inside a power hungry device like an amplifier has to work harder when the AC line voltage is closer to voltages the amp itself is generating. The higher the AC line voltage, the less hard the transformer has to work to generate its fixed output voltage.

Some high end audio enthusiasts even go to the trouble of requesting a separate AC line feed of 230V from their local electricity supplier. This is then used to wire an entire room in the house with the higher voltage which is designed for serious listening to their high end system. Their power amps, CD player, etc are all configured to operate on the higher value European AC voltage. The audio components also sound better from the fact that they have a separate AC line feed. They do not have to share the AC line with household appliances which tend to contaminate the line with spurious noises.

Going this far is actually not that expensive. It would probably cost only a few hundred dollars. The components that would benefit the most would be the power hungry components like loudspeaker amplifiers. CD players would benefit less.

While there is a small improvement starting with the C6xxx numbers, they are very rare and hard to find. There were only a few hundred? ever made (just before the SRM-1 was discontinued), compared with the several thousands? of all the other C series numbers. I have NEVER seen a C6xxx number available used and I've been looking around a while. If you keep waiting it may never show up.

The best I can recommend is to buy a C series in general, and then keep that for as long as it takes until a C6xxx becomes available. The C5502 SRM-1 driver available on ebay now is right at the boundary between the two sets of resistors. It almost certainly uses the Roderstein resistors.

It might be a good idea to email the seller and verify. Simply look through the top grill of the driver and the Roderstein resistors have a unique appearance. They have the usual color banded stripes, but also, unusually, they have "aluminum end caps" on the leads. Maybe the seller can notice this for you.

Quote:



Maybe you want to ask this guy if his amp is still available and what the serial number is:

http://www6.head-fi.org/forums/showt...highlight=stax

you are all evil. i will do nothing of the sort! my rig sounds great, i tell you, GREAT! *runs away with a pro bias plug bouncing off his heels*

Sorry - it's an A series. Sounds excellent to me also. Thanks for the info, espra.

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How weird is this! I've just had a look at the SRM-1/MkII I've got right here in my office (bought off ebay UK in March 2006) and guess what: it's the C5562 about which you wrote, and which is pictured earlier in this thread!

HI. I have a SRm1 mk 2 with only the noraml bias, but would like to add the "pro" bias to this unit. There is a space on the board for the pro bias components. Does anyone know the values of:
R301,R302,R303 and R304, C301,C302 and C303 and D301 and 302? I am assuming it is just a voltage doubler circuit.

I think all I really need are the resistor values of R301,302,303 and 304 to get this to work. Anyone?