eXStata DIY Electrostatic Amp for Intermediate DIYers
Jan 10, 2010 at 4:39 AM Post #1,996 of 2,970
Quote:

Originally Posted by dBel84 /img/forum/go_quote.gif
Great work too Beefy , looking very neat ..dB


Thanks, I'm pretty happy with it so far.

I think I might be getting some occasional static in the right channel though. Could be anything along the chain; USB board, DAC, XLR cables, amp, volume control and phones are all new/untested or very recently reconfigured. Will try and chase it down in the morning......
 
Jan 10, 2010 at 5:32 AM Post #1,997 of 2,970
That's very cool Marc. I agree with Don, more people will be interested when you get it solid enough and if you want to make it available at large.

Beefy, looks like a really nice looking build is in the works.
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Jan 10, 2010 at 6:49 AM Post #1,998 of 2,970
Quote:

Originally Posted by HeadphoneAddict /img/forum/go_quote.gif
I was pretty sure Blutarsky wanted a set of boards, but he is out of town all last week/this week and probably doesn't know about the new sets.


Bummer - I posted that 12/28 and Bluto just got back in touch with me, after a family trip and then a ton of work keeping him away. He did indeed want a set of Hybrid boards and was sad when I told him was too late. This is the second run of beta boards he has missed out on because of his work demanding his time. If anyone has a set they can part with and can PM him about it (and can wait a few days to hear back) that would be great.
 
Jan 10, 2010 at 6:54 AM Post #1,999 of 2,970
Quote:

Originally Posted by Beefy /img/forum/go_quote.gif
Its alive! And making sweet, sweet music
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Very early impressions are that it exceeds even the lofty expectations raised by Pabbi, headphoneaddict and others. Certainly superior to my previous t-amp SRD7-SB combo. Dead silent noise floor at normal listening volumes.

Mounting everything in the case will commence this week, as will the FPE order.



I'm so very glad you like the amp. And here I was worried that maybe I had set some unreasonably high expectations. It really shouldn't sound this good, but then I remember how good the CTH and EHHA sound and I'm not surprised (Bill's balanced EHHA is serious competition to my ZDT).
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Jan 10, 2010 at 3:15 PM Post #2,000 of 2,970
Alex,
Would it be fairly accurate to say that the series "center section" of the amp that includes the 271s, from R29 to R9 is roughly 200k+, and that the current in this section is roughly 3mA?

I'm guessing about 25k for P1.
I'm mainly just trying to get the current through this section to do some more calculations.
 
Jan 10, 2010 at 3:23 PM Post #2,001 of 2,970
The tail current is designed to be about 2mA putting 1mA into each jfet all the way to the negative rail. The total tail resistor is around 150k which is what sets this current since this "resistor" spans from +300V to slightly less than ground.

The current mirror multiplies this current by 3X putting about 3mA into the HV device whether it's the BJT or the triode.
 
Jan 10, 2010 at 4:58 PM Post #2,003 of 2,970
Well, I haven't had as much free time this weekend as I was hoping for, but I did listen quite a bit yesterday morning, and I can give you some impressions so far.

The first thing is the amp is dead quiet. On my amp, I mounted the connectors for the heaters on the underside of the board, so the heater wiring is far from all of the other wiring. The casework is not ready, so actually the whole thing is currently only mounted on plywood, with the star grounds only connected to the ground wire on the ac input terminal block. Even with this temporary setup, it is dead quiet.

As far as the boards go wrt heat dissipation, the power supply doesn't produce much heat at all. The amp heatsinks are also only warm - far from hot. The biggest source of heat that I am noticing is from the tube heaters to tell the truth.

This is my first time listening to stats, and the whole listening experience is so different than dynamics that I'm not sure I'm the right person to judge the amp, but here's what I notice so far.

The amp appears to have a great deal of speed with precise control. I started out with a few albums I know well, and what was apparent was the reproduction of echo and reverb is very realistic sounding. One album was David Crosby's If Only I Could Remember My Name, which was recorded at Wally Heider's. This studio had a very unique sound, and this amp does an amazing job of reproducing the subtleties of their echo chamber which to me points towards precision of the amp to keep each channel tightly in phase with the groove of the album. Anyway, not sure if that's true, but that's how it feels.

The amp has tons of low end, which is great as well. I love bass guitar, and the amps really shines here. It's not hit you over the head bass power, instead its again very precise which means you can actually hear what the player is doing. It seems too that this presence and control is also there at low listening levels, which seems different than dynamics. I notice I can get all of the bass I want without the urge to turn up the volume.

Beyond this, then things probably begin to become headphone dependent, and again the SR-404LE's are my first and only stats. My first impressions there is that the soundstage seems smaller as compared to my Beyer's, which is taking some adjustment in listening. Vocals are amazing on the 404's. I'm also thinking I like acoustic music better than electric on the stats, but I need to do more listening before I can judge. Let me rephrase that, it may end up being that I like listening to rock on dynamics better than stats, but like I said, I'll need more time to listen before I decide.

Overall, I'm really impressed with this setup. I'm listening to Pavement's release Crooked Rain right now, and it sounds great. The reproduction of the harmonics coming from Malkmus' jazzmaster is simply amazing...

Thanks again Alex!
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Jan 10, 2010 at 5:15 PM Post #2,004 of 2,970
Ah, a playah... have a listen to Marcy Playground (mid 60's strats), Zappa (Joe's Garage or Sheik Yerbouti - 50's strats, and the Hendrix Monterrey strat), Neil Young (Martins and that 1956 Gibson LP), The Who (Tommy or Who's Next for a J200, Quadrophenia for Entwistle's Alembic), Rolling Stones (Sticky Fingers - a beautiful Gibson Hummingbird) - just definitive.

For electronic, spin up some DEVO, Wall of Voodoo, or NIN (Pretty Hate Machine is like a mushroom induced haze).

For an epiphany, Radiohead's "Packd like Sardines in a Crushed Tin Box" is not only euphonic, but utterly overwhelming with the detail and texture.

This is not just an amp - it is it's own instrument, where you can listen, and, if so inclined, analyze - but while having fun. That is pretty rare, regardless of budget,
 
Jan 10, 2010 at 5:56 PM Post #2,006 of 2,970
Yes, I feel like I'll be busy listening to my whole record collection again over the coming months (well years) to discover the nuances hiding in the grooves. Thanks for all the suggestions Al. I can tell we have similar tastes in music. This will certainly be fun.

A quick question from a stats noob - I'm assuming its normal for there to be a crackle/pop sound when plugging in the connector to the amp, right?
 
Jan 10, 2010 at 5:59 PM Post #2,007 of 2,970
Quote:

Originally Posted by pabbi1 /img/forum/go_quote.gif
This is not just an amp - it is it's own instrument


Just reread what you wrote - and that is a great way of describing this amp.
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Jan 10, 2010 at 7:24 PM Post #2,008 of 2,970
Quote:

Originally Posted by TimJo /img/forum/go_quote.gif

The amp appears to have a great deal of speed with precise control. I started out with a few albums I know well, and what was apparent was the reproduction of echo and reverb is very realistic sounding. One album was David Crosby's If Only I Could Remember My Name, which was recorded at Wally Heider's. This studio had a very unique sound, and this amp does an amazing job of reproducing the subtleties of their echo chamber which to me points towards precision of the amp to keep each channel tightly in phase with the groove of the album. Anyway, not sure if that's true, but that's how it feels.

Thanks again Alex!
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I also find Crosby's IOICRMN to be a disc I go back to all the time as a reference for evaluating equipment. In addition to the room acoustic where it was made, the mix of acoustic, electric and vocals and the separation between them has always been a key evaluation criteria for me.

While I don't have the diy amp, just a srm-t1s, I also just received 404LEs and am starting to get to know them............holy *.?$ batman, Stax with bass???????
 
Jan 10, 2010 at 11:08 PM Post #2,010 of 2,970
Quote:

Originally Posted by Beefy /img/forum/go_quote.gif
I think I might be getting some occasional static in the right channel though. Could be anything along the chain; USB board, DAC, XLR cables, amp, volume control and phones are all new/untested or very recently reconfigured. Will try and chase it down in the morning......


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.

At first I thought it could have been my slovenly week-plus without shaving rubbing on the pleather, but I'm all clean now and can still hear it. Doesn't seem to be cable microphonics either......
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