A S.E.X. for Stax. Putting the E back in sEx :)

So capacitors in the SEX, I feel at an impass. Sound wise I would like a little more mid bass/low treble than I have currently. I'm getting closer but not quite there.

I tried the Mundorf S/G/O for couplers and have been playing around with Russian KBG-MN's for parafeed. The Mundorfs have a little too much top end for my ears and to be honest, I don't find them as musical as the K40's for couplers. The k40/KBG combo is really nice to listen to. It may be a little edgy on some vocals but it could also be the Gibb brothers (listening to Bee Gees, Spirits Having Flown).
 
It took a buddy to remind me that tubes have more of an effect on sound than capacitors. I rolled in a pair of old (1958) GE tubes and it was just what the doctor ordered. I've read that there isn't much change when rolling 6DN7 tubes but in my case it was enough to tame the highs and bump the low end just a little.

Time to get back to the music!
 
I've sent some time now with the SRD-7 + SEX combo now and think it sounds lovely but is ultimately underpowered.  The tone and soundstage is appealing and expansive but lacks the clarity, detail and focus which my dedicated STAX amp delivers.  I which I had another dedicated speaker amp to test the SRD-7 with to see what improves with more power. 
 
There was a recent Head-Case group buy for board for two Kevin Gilmore Stax amps: his "Megatron" (tube amp) and KGSSHV (solid state). The guy who organized the group buy (username Lil' Knight) might have some boards left over. Check in the DIY subforum of Head-Case.

Best regards,
Adam
 
Power shouldn't have anything to do with it as long as it is capable of reaching the same listening volume without clipping as your dedicated Stax amp. If you are running the SEX wide open to achieve listenable volume then you will have a higher level of distortion than if the amp as idling along.  That box is in essence a pair of PP transformers wired in reserve with a bias suppy. It acts as a phase splitter and a voltage step up. By putting a more powerful amp in front of it you can swing higher voltages and reach higher volumes. That box is the limiting factor if you follow the train of thought.

I have nothing against the tube based Stax amps but to my ears, I didn't care for any of them. My SEX is still being tweaked to my listening preferences and that is something you can't do with the Stax amps. It's a hell of a lot simpler having one and if they fit your listening preferences then congrats!

If you like the sound of the transformer box with other amps you can easily build one yourself with much better iron. A 5k transformer has the ideal winding ratio but others have had good results with 8.6k too. It's a balance between power output of the amp and finding a transformer with the lowest turn ratio to achieve the voltage step up to drive your ear speakers. If you search on Head-Fi there are a few old treads on the topic. I was going to go this way but again, it's a compromise. The SEX offered a simple platform to experiment with I'm happy with the results. To be honest I don't listen to headphones enough to justify a dedicated amp for them. My current focus has been tailoring the SEX to match my speakers and listening preference. Once that's dialed in I'll put on the cans and see if they sound good enough :)


 
I've been rolling caps for a while and have finally settled on a pair that work well with my system (for now ;). I'm using the Rike Audio S PIO capacitors for both coupling and parafeed positions (standard values). These caps are surprising in may ways. First, they are not like other PIO's I've tried in the SEX namely the K40 and KBG's which until now has been my favorite combo. The Ruskies had a certain fluid nature that is suductive. The Rike caps have a surprisingly neutral clarity to them that is easy to listen to though it can be too revealing at times. They have a wonderful soundstage that is deep, layered and realistic in tone and presentation. Overall they do everything nicely but not too nice if you know what I mean. The level of detail is all I could ask for without being painful and the tone seems accurate to my untrained ears.  And given their price they are worth a try. As a coupler, I prefer them over the Mundorf S/G/O...
 
The SEX has to run at nearly max to get a good listening level with most of my hi resolution music which has a high dynamic range.  I'm not sure if it plays a big role in the performance but I have my impedance switches set to the MH level.  One idea I've been thinking about is to buy a Stereomour and install the guts of my SRD-7 thus making it a dedicated STAX/Speaker amp.  I would like to ditch the STAX and keep my setup more streamlined but so far the SEX + SRD7 cant deliver the same level of performance.  Also I dont have any experience in tweaking electronics so I can't do much tweaking on my own. 
 
Stats are all about voltage, I'd try the SEX at the highest impedance rating (to get the most voltage). 

Also, the C4S ugprade will give you a bit more gain, which may be helpful.
 
Paul, what would you think of an exo 173 instead of the Sowther to do the stax sex (or maybe mainline)? I have a cobalt pair looking for a home.
 
X-Fi > Stello DA100 > Extended Foreplay III  > SEX 2.1 > Stax SR-Lambda with SRD-7/SB

This is the setup that is used with my Stax headphone with the amp, with C4S, impedance switches set at 4 ohms.  Used 8 ohms but noticed a slight amount of hiss that I don't get a 4 ohms.  By using the Foreplay to set max volume I have full range on the amp volume knob.  It plays as loud as I can possibly stand...

tdogzthmn said:
The SEX has to run at nearly max to get a good listening level with most of my hi resolution music which has a high dynamic range.  I'm not sure if it plays a big role in the performance but I have my impedance switches set to the MH level.  One idea I've been thinking about is to buy a Stereomour and install the guts of my SRD-7 thus making it a dedicated STAX/Speaker amp.  I would like to ditch the STAX and keep my setup more streamlined but so far the SEX + SRD7 cant deliver the same level of performance.  Also I dont have any experience in tweaking electronics so I can't do much tweaking on my own. 
Click to expand...
 
Would placing a Quickie in front of my SEX make more of an impact than adding the CS4 boards?  The SR-507 headphones are more revealing than my previous HD800, so I'd like to make sure they can perform their best.
 
The C4S upgrade will lower distortion, increase gain, and improve the noise floor.

The Quickie will increase the gain, increase the distortion (just a little) with no impact on the noise floor.

(I'd opt for the C4S first)
 
Thanks for the advice Paul.  I've also notice that I've been able to get a good level with the volume set at 60-70% where in the past I had to keep it at 90-95% to get a good level.  Maybe the SRD-7 takes time to warm up?  I don't think the output of the SEX has changed so I'm guessing the transformers in the STAX box needed some time to get working.  Either way adding the CS4 board will improve the listening experience! 

STAX headphones can generally be had for very reasonable prices.  Its the special "energizers" which generally increase the price and the limited compatibility with other gear that puts people off. 
 
Today I stripped the HN plate chokes out of my SEX for use in another project and found that I prefer the sound with the resistor. All things with time and experimentation it seems!  At the moment I'm jamming out the Daft Punk's, Random Access Memeories :)
 
Last week I replaced the PS resistors with a pair of SEX 2.0 PF chokes thanks to a generous BH member. I'm not sure if it was the PS chokes, the removal of the plates chokes or everything finally settling in but the sound is impressive. Strings and piano finally sound correct and my wife and I are enjoying the system more than ever.

This little SEX amp really delivers with HE speakers!
 
I have been able to try my SR-507 on both my Stereomour and SEX amp using the SRD-7 and find that the SEX does a better job of driving the STAX headphones.  I believe the CS4 boards I added did take the level of performance up a notch.  Really makes for a killer listening experience that tops any headphones I have owned or heard in the past. 
 
Oh man this sounds like a great project. Any chance you still have pictures of it/can take more? The ones in your replay on the first page are corrupted on download :(
 
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