[Beefy]

Oh, and just some notes on DC offset behaviour. On power up, there is a tiny spike, but it behaves very well.

On power down, there seems to be a lot more offset - it jumps up to ~30V before drifting down again. Is it because the negative rail with its higher current draw collapses before the other? Or is this unique to my build?

 

[luvdunhill]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif My static issue seems to be the phones themselves. Even after unplugging them from the amp, they give an occasional 'scratchiness' that seems to hang around as long as the bias is still up. It sounds like a rodent rummaging through the roof at night.

That's very strange, I've never encountered anything like that *after* they've been powered off..

oh, I cannot imagine DC offset of those magnitudes being an issue.... compared to the very large "DC offset" that you're intentionally applying to the drivers

 

[runeight]

Check the bias supply soldering on the board. I wonder if this is intermittent HV to the headphones??

Yes, the shut-off swing is higher than the turn on. I haven't bothered to think about why, but your theory seems like a good working assumption. And, as Marc says, 30V is trivial to these headphones.

 

[Beefy]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif That's very strange, I've never encountered anything like that *after* they've been powered off..

Quote:

Originally Posted by runeight /img/forum/go_quote.gif Check the bias supply soldering on the board. I wonder if this is intermittent HV to the headphones??

I'll try them again with the SRD7-SB and see if it still happens.

I doubt it is anything on the board, as both drivers are connected to the same terminal but only one is doing it. Poor wiring is a higher probability, but as Marc says it is really odd that they keep scratching after they have been disconnected.

 

[Emooze]

It wouldn't happen to have something to do with the fact that the drivers are essentially capacitors? Mine do this too after the amp is shut off, headphones unplugged.

 

[sumo-kun]

Regarding scratchyness, I have some SR303s that have never done that since I bought them. However I have bought an SR001 which does do it... kind of. I bought them new not too long ago and I was curious if the ear pieces could be modded with damping so I opened one side up to take a look inside. Of course, there is next to no space in those things Anyway, I had them completely apart and put them back together the best I could. Afterwards, I noticed weird sounds coming from the earpiece. The reason came from there being an airtight seal from the phones to my ear and the (slight) change in air pressure seemed to make the diaphragm or something else in the earphone wobble ever so slightly and give a crackle/scratch noise. It didn't happen in the other ear. It also occasionally gave a farty type sound. Anyway, it really annoyed me so I took it apart again, checked it, there was some dust so I cleaned it and put it back together again and now it is perfect.
Moral of the story? Well, maybe its dust but I guess you should first check if you still get weird sounds if you don't move at all. If you still do, get some cotton or something and wedge it between the pad and your head to create an air gap and see if that changes things. I also think it is very unlikely it is something to do with the amp. If the entire headphone is still storing charge, then maybe you could try draining the capacitor so to speak?

 

[Beefy]

Thanks for sharing your experience, sumo-kun

I have tried 'discharging' the bias and the effect does seem to lessen (but the humidity in here is so dreadfully low, I can't be sure everything has completely dissipated), so I don't think it is any sort of microphonics. Some advice I got elsewhere it that if dust gets in there I will get a screeching noise. I have been told it is possible that the dust cover is rattling, the stators are separating from the diaphragm, or that a small amount of arcing has left a deposit on the diaphragm.

Still need to do more testing though, but I will keep at it......

 

[sergery]

Hey TimJo, how are you finding the volume levels with your setup? I am thinking about setting up a vinyl rig and considering various phono stages. I am concerned I will end up with a weak source though. I am not a maths pro, but I calculate u feed the exstata something like 150 mV, which seems low, but I didn't know all of the impedances so this could be way off.

 

[runeight]

Gents, I have PM'd acmemr and given him at least 48 hours to respond beyond the many posts to this thread asking for shipping information. It's hard for me to know what his circumstances might be or why he is not able to communicate. But, he has rights to the last SS board set.

Since I need to get this done before too much longer, I'm going to make this board set available to the first person who PMs or emails me. But the rule still applies. No doubling up and no one from the first beta team.

I hope that acmemr will forgive me for having to make this change in order to finish out this beta build.

As you all know I'll be out of town soon. I will, of course, still have internet access while plying my trade in other places, but I won't be contributing as much. I think there are enough seasoned eXStatA builders on this thread and the amp is sufficiently problem free that new builders should have no trouble getting their amps working.

Hopefully those of you who DO have eXStatA builds are enjoying them because we don't know when we'll get back to this.

 

[sumo-kun]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif Some advice I got elsewhere it that if dust gets in there I will get a screeching noise.

I had that problem too when I put my SR001s back together the first time

Scared me pooless the first time turned it on because it was so loud.
Big piece of dust/hair discovered when I opened it up but that wasn't the source of crackling. Have the phones been opened up in the past? It sounds more like a mechanical problem rather than an electrical one, due to the noise being present even when they are unplugged and probably discharged. As a last resort, maybe you could give them a good shake to dislodge any loose particles or maybe settle down the loose parts?

 

[HeadphoneAddict]

Quote:

Originally Posted by runeight /img/forum/go_quote.gif Gents, I have PM'd acmemr and given him at least 48 hours to respond beyond the many posts to this thread asking for shipping information. It's hard for me to know what his circumstances might be or why he is not able to communicate. But, he has rights to the last SS board set. Since I need to get this done before too much longer, I'm going to make this board set available to the first person who PMs or emails me. But the rule still applies. No doubling up and no one from the first beta team. I hope that acmemr will forgive me for having to make this change in order to finish out this beta build. As you all know I'll be out of town soon. I will, of course, still have internet access while plying my trade in other places, but I won't be contributing as much. I think there are enough seasoned eXStatA builders on this thread and the amp is sufficiently problem free that new builders should have no trouble getting their amps working. Hopefully those of you who DO have eXStatA builds are enjoying them because we don't know when we'll get back to this.

I would still love to see you make these available to everyone and anyone soon, even as a PCB set and written BOM since kits wont be made available like the CTH had. We need more eXStatA, CTH and EHHA out in people's hands as they are all wonderful amps.

 

[runeight]

Thanks. I'll be back sometime, but things will change. The EHHA is obsolete unless someone puts the 6GM8s into current production. It will be replaced with the EHHA II. The CTH ... well there are things in the works. And the eXSTatA will be back sometime in some form. And then there are the amps that you guys don't know about yet. But I gotta take care of business first.

 

[BoilermakerFan]

Quote:

Originally Posted by runeight /img/forum/go_quote.gif Thanks. I'll be back sometime, but things will change. The EHHA is obsolete unless someone puts the 6GM8s into current production. It will be replaced with the EHHA II. The CTH ... well there are things in the works. And the eXSTatA will be back sometime in some form. And then there are the amps that you guys don't know about yet. But I gotta take care of business first.

Hmmm. So I was planning to build my Aikido 24V as a HV mod with the other 500VCT trafo I bought.

Which means my NOS Amperex Holland 6GM8s have a new home. Booyah!

Which way to build them AC? BJT with 2238/968 or MOSFET IRF510/9510?

I happen to have both in my stash.

 

[pabbi1]

Quote:

Originally Posted by HeadphoneAddict /img/forum/go_quote.gif I would still love to see you make these available to everyone and anyone soon, even as a PCB set and written BOM since kits wont be made available like the CTH had. We need more eXStatA, CTH and EHHA out in people's hands as they are all wonderful amps.

The BOM is available (if read the comment correctly).

Agreed on more eXStatAs - that's why I built 4, and still have 3, though one is going to my brother over in the sandbox. Even Jarheads know a good amp when they hear it...

 

[runeight]

Actually gents, quite a few exstatas have been built now. The first beta run was 39 total board sets. The second will be 20. This doesn't include the few original proto amps that are circulating around.

In this respect perhaps we can consider the project successful so far with at least 60 amps in use or about to be built. And, it would seem from the posts, quite a few folks were encouraged to try stats as a result of this amp's availability.