The Bear's new Aleph-X

sbear · 2nd June 2005, 12:29 AM

Well, I did it. Fired up my pair of 100+W Aleph-X's about two hrs ago. I don't know what else to say,

really.

I'll try to remember averything I've got going on here:

12 IR IRFP244 per ch. running almost 8A total
16.5V rails
Absolute offset is hovers +/- 100mV around zero
Rel Offsets are 10mV and 25mV running balanced and DC coupled to my mixer.
Dual discrete schottky bridges
Surplus 475VA trannies with dual 17V secondaries
Heatsinks: Wakefield's I got used on the net (no idea what model). 6 per channel and only $10 a piece
(total $120) and they get pretty warm but not so hot that I have to take my hand off.
CRCRC C's are 47000uF panasonic TH-HA series and R's are two parallel 0.22 ohm 10W power resistors
(only one side has the R's right now-the one with the R's has absolutly no audible hum, the without has some hum that cannot be heard more than about 2 feet away. Tweeters hiss some on both though (don't know if this is normal, but, like the hum, it can't be heard more than a ft or two away.)

But don't ask me about the sound! I wouldn't exactly know how they are supposed to sound. I'm not really an
audiophile and I have never listened to any high end systems. I was thinking about buying an amp about a year ago and couldn't afford anything good. Eventually I ran across the PassDiy site and this forum; I started reading and thought, "I can do this!" So I can only compare it to my roomates pioneer receiver and
mine sound better! I wish I had better speakers to run these through- guess I'll have to build those next.
I'm running these through my roommates definitives (no clue on the model).

I want to thank everyone involved with this forum for sharing all the info making this possible, especially Grey for his original contribution.

And I want to thank Mr. Pass personally for not just letting me, but allowing everyone here a chance to build such a wonderful amps through his generousity.

Now I just have to make them look nice. . .

sbear · 2nd June 2005, 12:31 AM

a few pics

sbear · 2nd June 2005, 12:36 AM

Oops. Let me try those pics again

sbear · 2nd June 2005, 12:38 AM

Another. . .

sbear · 2nd June 2005, 12:40 AM

Last one for now.

GRollins · 2nd June 2005, 01:55 PM

You're welcome, of course, but all I did was play around a bit with some of the concepts that Nelson put on the table. I've got a few other ideas that'll I'll toss out when I've got sufficient time to support a thread--very time consuming.

Grey

Netlist · 2nd June 2005, 03:09 PM

Congrats sbear, apart from some cleanup of wires it looks good.
Can the transformer take the current?
Also, how did you manage to get 16.5V rails out of dual 17V secundaries?
I like the Frugal-Phile (tm) approach.

/Hugo

sbear · 3rd June 2005, 01:02 AM

The transformers are very iffy and I'm planning on buying some new ones as soon as I can, but I wanted to make sure everything worked before I dropped the cash on the most expensive part of the amps. (I have another thread about the poor performance of the transformers which are sagging about 4V under a light load.) As far as the power supply goes, I would still like to add some bypass caps across the last big cap in each supply to quicken them up a little, but I can't decide what to do (how much F, brands, types, etc); any suggestions?

Also these amps are pretty darn loud for my small room right now and I am thinking about making these amps switchable between aleph current source and constant current source. This theoretically cuts the output power in half if I understand things correctly. Or am I wrong? Can someone verify, please? I also seem to remember reading that all I need to do to accomplish a constant current source is to break the connection between C1 and R12, and C6 and R34 (using greys original schematic). Anyone tried this?

Blues · 3rd June 2005, 01:53 AM

sbear,

If the components you mentioned are part of the current sources' feedback...breaking this connection will only limit the amps' peak to peak current output to its DC bias current. You keep the same gain and bias. Loudness will depend on your preamp volume setting

sbear · 3rd June 2005, 02:05 AM

Blues, thanks for setting me straight. I thought about it for a second and realized you are absolutely right. I guess I could still make it switchable just to hear the difference.

2nd June 2005, 12:29 AM	#1
sbear diyAudio Member Join Date: Jul 2004 Location: Lawrence, KS	The Bear's new Aleph-X Well, I did it. Fired up my pair of 100+W Aleph-X's about two hrs ago. I don't know what else to say, really. I'll try to remember averything I've got going on here: 12 IR IRFP244 per ch. running almost 8A total 16.5V rails Absolute offset is hovers +/- 100mV around zero Rel Offsets are 10mV and 25mV running balanced and DC coupled to my mixer. Dual discrete schottky bridges Surplus 475VA trannies with dual 17V secondaries Heatsinks: Wakefield's I got used on the net (no idea what model). 6 per channel and only $10 a piece (total $120) and they get pretty warm but not so hot that I have to take my hand off. CRCRC C's are 47000uF panasonic TH-HA series and R's are two parallel 0.22 ohm 10W power resistors (only one side has the R's right now-the one with the R's has absolutly no audible hum, the without has some hum that cannot be heard more than about 2 feet away. Tweeters hiss some on both though (don't know if this is normal, but, like the hum, it can't be heard more than a ft or two away.) But don't ask me about the sound! I wouldn't exactly know how they are supposed to sound. I'm not really an audiophile and I have never listened to any high end systems. I was thinking about buying an amp about a year ago and couldn't afford anything good. Eventually I ran across the PassDiy site and this forum; I started reading and thought, "I can do this!" So I can only compare it to my roomates pioneer receiver and mine sound better! I wish I had better speakers to run these through- guess I'll have to build those next. I'm running these through my roommates definitives (no clue on the model). I want to thank everyone involved with this forum for sharing all the info making this possible, especially Grey for his original contribution. And I want to thank Mr. Pass personally for not just letting me, but allowing everyone here a chance to build such a wonderful amps through his generousity. Now I just have to make them look nice. . .

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2nd June 2005, 01:55 PM	#6
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	You're welcome, of course, but all I did was play around a bit with some of the concepts that Nelson put on the table. I've got a few other ideas that'll I'll toss out when I've got sufficient time to support a thread--very time consuming. Grey

2nd June 2005, 03:09 PM	#7
Netlist diyAudio Moderator Join Date: Jan 2003	Congrats sbear, apart from some cleanup of wires it looks good. Can the transformer take the current? Also, how did you manage to get 16.5V rails out of dual 17V secundaries? I like the Frugal-Phile (tm) approach. /Hugo

3rd June 2005, 01:02 AM	#8
sbear diyAudio Member Join Date: Jul 2004 Location: Lawrence, KS	The transformers are very iffy and I'm planning on buying some new ones as soon as I can, but I wanted to make sure everything worked before I dropped the cash on the most expensive part of the amps. (I have another thread about the poor performance of the transformers which are sagging about 4V under a light load.) As far as the power supply goes, I would still like to add some bypass caps across the last big cap in each supply to quicken them up a little, but I can't decide what to do (how much F, brands, types, etc); any suggestions? Also these amps are pretty darn loud for my small room right now and I am thinking about making these amps switchable between aleph current source and constant current source. This theoretically cuts the output power in half if I understand things correctly. Or am I wrong? Can someone verify, please? I also seem to remember reading that all I need to do to accomplish a constant current source is to break the connection between C1 and R12, and C6 and R34 (using greys original schematic). Anyone tried this?

3rd June 2005, 01:53 AM	#9
Blues Lightning In A Bottle diyAudio Member Join Date: Sep 2003 Location: Bremerton, WA	sbear, If the components you mentioned are part of the current sources' feedback...breaking this connection will only limit the amps' peak to peak current output to its DC bias current. You keep the same gain and bias. Loudness will depend on your preamp volume setting

3rd June 2005, 02:05 AM	#10
sbear diyAudio Member Join Date: Jul 2004 Location: Lawrence, KS	Blues, thanks for setting me straight. I thought about it for a second and realized you are absolutely right. I guess I could still make it switchable just to hear the difference.

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