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Old 14th August 2007, 07:24 AM   #1
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Default New Projects Questions

Well first off hello to all in the Pass section, and much love and respect to Nelson for being so gracious to the DIY community with his designs, ideas, and continued support

For that reason I decided to make my next projects Pass orientated. I have been working on a few of my own designs with some success, but I want something new to learn from...and to tantalize my ears! I have a pair of LM3875 based non-inverted amps, which sound good, especially when playing movies, but I feel they are lacking something. I also have a pair of Original 1969 JLH's with MJ15003 outputs which I LOVE! They sounded magical even when I first fired them with RCA 3055's with a 18v supply, 6800uF PSU cap, and a 2n2222 as a splitter/driver...LOL. Now it has a BC556 input and a 2n3019 driver/splitter. It is soon to get some Halco .1% precisions and maybe some Cerefine's or Muse's, see if they change the sound at all. Maybe give the regulated/capacitance multiplied PSU a shot too, right now it is unregulated with a big 33KuF Mallory cap. I must say the JLH, to me at least, will be a tough act to beat, but I think Nelson is up for the challange

I have a few designs I have been looking at and have some questions on each. The first design I am thinking of would be a Zen of some variety or a Mini-Aleph. I really don't know what kind of Zen, I have a LTP Zen plan designed by Allen Newby that I am drawn to, but I would also like to stick with a traditional more Pass-like design. Any advice from builders which version they like the best, I know the differences are subtle, but they are there. This would get my feet wet in Nelson Pass designs.

My next project is slightly more ambitious, a Aleph-X pair. I have always had a...well call it fetish... for the X topology, and have always wanted to try it. I hear the results can by pure sonic joy if done correctly. I really want something to A) compare with and/or beat my JLH. B) Have something to use for a reference for my designs, and for other DIY amps. C) Have something to blow the socks off my buds...though the JLH's have done that so far. I think the AX may be what I was looking for. I want something that can bring me to tears (you know what I mean) when I listen to some jazz or a piano solo...something that can free me when I listen to some Matisyahu (OMG, love them) or Dave Matthews...but can also drive like mad if I want to listen to some rock or watch a movie with it. I am thinking Aleph-X 100 or maybe a little more (power wise) unless anyone has a different suggestion, and I am fully open.

1. For the A-X builders out there though...would it be easier to build a version with single pairs of output devices and a +/-15 supply, then move up, or better to start full size?

2. I am almost certain I will be driving this from a BOSOZ (or CCS-X-BOSOZ) preamp. But my sources (for now) are not balanced, how do I get around this, ie unbalanced into balanced? Besides using some opamp unbal to bal driver (I was thinking about this for a balanced LM3886)?

3. I am planing on going "all out" on this set of projects, namely the AX, I have some questions regarding that.

A) Are Holco's (though highly regarded) a better choice than Vishay/Dales (a little easier to get and cheaper)? I know the (some) Holco's are .1% vs. 1%, but I am just curious. I really want to do Caddock Mk132's throughout, and I know that would be "all out", but that would be hundreds, approaching thousands on just resistors. Also is it useful at all to put something like Vishay Foils in signal path locations? IE the 100k in the feedback, the 10k at the input (on the AX), or is it overkill compaired to just using a precision Holco, Caddock, or Dale?

B) Is there a point to getting some "sell my kidney/soul" Black Gates over Cerafine's or Muse's? Are the general purpose Black Gates good as well, or should I go with a N series or FK/K/VK...I guess which Black Gate if I used them. The standard grades are about $7.00 for the required 220uf caps at 50V, to goto a N series it would be in the $30 to $40 range. For about $4 than a Muse of the same value and rating I would use the BG Std., but for the N Series price I would like to hear from some users before I spend that much...I know I know, not very "all out"... I am a poor college kid, LOL. Lastly is it better to use Bi-Polars in these spots or polar?

C) For the outputs, to what voltage are the IRFP044's usable up to? I know they are rated for 60v (IR's datasheet) but I don't want them running on a +/-50v supply for safety, besides I like overkill, I'm old school. Are there any better/other choices than the IRFP240?

D) What do ye builders recommend for the output resistors, the high power ones. Mills wire wounds, or something like some metal oxide precision power resistors?

Thanks to all for your time, and for dealing with my noobish long and winded posts!

Cheers to DIYAudio!
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Old 15th August 2007, 06:15 PM   #2
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For your questions regarding component types, look first to Nelson's publications on www.diypass.com. Nelson has covered this material in great detail.

I'd suggest you search the forum here as most of the questions you are asking have been discussed at some length. For example read teh Aleph X builders thread, and search for the AX and xBosoz threads. I believe you will find everything you are looking for.

Also consider building a Zen or Aleph 3 or Aleph30 as your first amp. It's much easier than the X amps and sound wonderful.

Welcome,

-David
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Old 16th August 2007, 01:22 AM   #3
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Quote:
2. I am almost certain I will be driving this from a BOSOZ (or CCS-X-BOSOZ) preamp. But my sources (for now) are not balanced, how do I get around this, ie unbalanced into balanced? Besides using some opamp unbal to bal driver (I was thinking about this for a balanced LM3886)?
There are many "slight" variations to the BZLS that make great unblanced to balanced converters. There is "metalman's circuit" posted out there on a thread somewhere that I believe Nelson said was good for unbal to bal conversion. It is a cascoded circuit with one current source. Take a long look at the BOSOZ or BZLS threads and I think you will find it.

JJ
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Old 16th August 2007, 01:28 AM   #4
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A plain vanilla BOSOZ will do the trick.


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Old 16th August 2007, 01:36 AM   #5
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Oh, my 2-cents regarding the really expensive resistors:

IMHO, the only person who can really tell you if it is worth it is you. (not babowana, jpeitzman).

Listen to a circuit with Vishays, listen to the same circuit with Halcos. If you can hear the difference, then it is probably worth it.
I have used the Vishays in all my amps, and the amps sound amazing.
I don't have the time to do a detailed listening comparison of resistor types in circuit. I wish I did. I would if I had the time, but I don't. But like I said, the amps sound amazing and I don't lose any sleep worrying about whether they would sound better if I used Halcos.

Certainly, someone who sells resistors for a living will tell you which ones to buy.....

I've also seen powercords with voluminous plastic baggies for insulation that were said to greatly improve the sound of any system.....

JJ
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Old 16th August 2007, 02:18 AM   #6
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Hmmm...

Do you suppose Halcro uses Halco's?

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Old 16th August 2007, 02:27 AM   #7
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You could probably stick Clarostat rheostats all over the inside of an Aleph and it would still sound good

I wouldn't lose sleep over it and just use good parts
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Old 16th August 2007, 02:56 AM   #8
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I think the way this works is first you make a Lily, then
you gild it.

I always publish un-gilded lilies - that way you get the pleasure
of making your own contribution.

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Old 16th August 2007, 03:19 AM   #9
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Thanks for the replies, especially Nelson's, always very, hmmmm.....zen

I did do some searching and found some other answers/ideas for the balanced/unbalanced problem. Thanks though for the replies and ideas on that. I am just wondering though that if I build a BOSOZ and a Aleph-X, it there a point if I am not feeding it from a balanced source?

I have decided though that I think I will build some small DRV134 based boards to slip into ether a DAC or a cheap (to start with!) DVD/CD player. To me this seems like the easiest route to obtain balanced line outs from unbalanced sources...despite my coolness towards op-amps.

I reread my part on parts and thought, wow! Early morning ramblings...I am just going to use some Dales from Mouser and some quality caps, add money later...like Nelson said, "build the lily".

I am ordering parts as I type for a Aleph-M! It will be my first foray into a Pass design with the others soon to follow. Keeping my fingers crossed that all goes well, soon I should have a cute desktop Aleph. I do have one quick question though, I am ordering IRF644's for the output devices, could/should I use IRFP044's or IRFP240's...or something different?
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Old 16th August 2007, 04:17 AM   #10
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That's gild the Lily.

The BOSOZ is also popular for single-ended output applications
because the differential pair offers some distortion cancellation
that you won't see with a single device.

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