Aksa Lender P-MOS Hybrid Aleph (ALPHA) Amplifier

[xrk971]

Did some soldering tonight, have to ask what those resistors marked in bom as R20x and R22x supposed to be ?

The BOM for B.B. v2 is in the other thread:

http://www.diyaudio.com/forums/atta...aleph-alpha-amplifier-alpha-bb_bom-v2-xls-zip

I could not find any R20x or R22x in that spreadsheet. Can you sho wow where?

X

 

[Juntuin]

Somewhere there?

 

[Vunce]

Juntuin,
I believe those parts are for the additional circuitry for those fan control boards. You do not have to populate that stuff now to get the alpha amplifier board to work.
The only SMD components you need are the snubber resistors and capacitors for the output MOSFETs.

 

[xrk971]

Yes, those were supposed to be part of the PWM fan controller board that JPS64 designed. I forgot to move them down to rest of stuff associated with the fan controller.

 

[xrk971]

I just tried using the TimS Simple HPA as a preamp for the Alpha BB, and can confirm that it works very well. It's a low distortion DC-coupled headphone amp that I employed as a preamp.

Simple High Performance DC Coupled Class A HPA with sub PPM THD

This was with my hand-etched prototype.

Of course, JPS64 is on the case and is developing an uber-special version of this HPA with built in 4uV rms dual rail power supply that only needs a 12v wall wart for power.

Here was my measurement of the prototype with the new ultralow noise psu. You can see the noise floor has very short "grass" - as low as a battery, and this is running off 120vac mains.

 

[pinnocchio]

X did you used these type of caps on the input.
If yes where did you got those?
Thank you

You can buy them at Parts Connexion in Toronto. You'll save customs this way

ClarityCap CSA/ESA 250Vdc Series Film Capacitors

Thanks
Do

 

[Juntuin]

Finally some psu wiring, couple of things missing though..

 

[Juntuin]

Oh, forgot to ask. Should I add MKP's as bypass caps or not? I have usually used bypass caps, but don't actually know is there any real world reason to use those for HF-filtering?

 

[xrk971]

Yes, 0.1uF MKP/MKT/MKS 100v to 250v is fine for bypass between legs of each cap. Actually, a tiny 0.1uF X7R 100v SMT is very good for this.

 

[Juntuin]

Wow, usually this subject gets as much opinions as there are builders.

Yes, 0.1uF MKP/MKT/MKS 100v to 250v is fine for bypass between legs of each cap. Actually, a tiny 0.1uF X7R 100v SMT is very good for this.

Thanks X, i guess I'll go with that then. Normally I have used only one pair of bigger bypass caps, but let's go with your way now

Powered up PSU couple of minutes ago, added 2,2k bleeders before that. +/-44,6v without load, that's a little more than I hoped but let's see where it sags under load.

Seems that my home brew secondaries won't provide enough current for fans. Luckily it provides enough juice to control dc-prot/delay circuit. So, next thing is seek some little 230v/12vdc small power supply that can output 100w/0.1A? Ebay is not an option, takes too long to delivery.

Actually I'm really close to fire first channel up, it could happen tonight but I'm too tired to build it now I can power fans with external psu..but tomorrow I'm not home and work related trip on monday..

 

[Vunce]

Powered up PSU couple of minutes ago, added 2,2k bleeders before that. +/-44,6v without load, that's a little more than I hoped but let's see where it sags under load.

Nice progress Juntuin!
I get about 43.5vdc without load, 37.5vdc with the BB connected. I’m good with the slightly higher voltage, heat is not an issue. You could increase your resistors a bit to lower the output or add another resistor between your paralleled C’s. (CCRCRCRC)

Cheers

 

[Kokanee]

@Juntuin or anyone who has used bypass caps,

Is it possible to get a closeup of how you soldered the cap to the legs. I take it the caps are for lessening of the HF hash/ripple. If you used by pass on your rectifiers/bridge, would you need these on the caps.

Thanks for the help

 

[drpro]

My build is down the road a bit, other projects, life first. I really like what you have done Juntuin. It is nice to see the various build paths folks are going.
Super good.

 

[Juntuin]

Nice progress Juntuin!
I get about 43.5vdc without load, 37.5vdc with the BB connected. I’m good with the slightly higher voltage, heat is not an issue. You could increase your resistors a bit to lower the output or add another resistor between your paralleled C’s. (CCRCRCRC)

Cheers

Ok, maybe B.B. can handle my extra 1,1v I will use my fans at full 12v, they are so silent and I'm not using any PWM controlling on this one.

@Juntuin or anyone who has used bypass caps,

Is it possible to get a closeup of how you soldered the cap to the legs. I take it the caps are for lessening of the HF hash/ripple. If you used by pass on your rectifiers/bridge, would you need these on the caps.

Thanks for the help

It have been always a challenge for me also, this time I was thinking to find some axial film caps to make soldering easier. It would be interesting to hear how everyone else have done their bypasses? I read that it's better not to use bypass at all than use wrong values at wrong places?

My build is down the road a bit, other projects, life first. I really like what you have done Juntuin. It is nice to see the various build paths folks are going.
Super good.

Yeh, more important things first thanks, I like to see also how people have their own paths how this should be built.

 

[xrk971]

Wow, that looks very nice! Awesome job, Juntuin!

I use a tiny 12v 800mA external wall wart class 2 transformer and it powers two separate PWM controller boards, which powers 4 of my PWM fans just fine. But maybe PWM fans use less current?

 

[Juntuin]

Wow, that looks very nice! Awesome job, Juntuin!

I use a tiny 12v 800mA external wall wart class 2 transformer and it powers two separate PWM controller boards, which powers 4 of my PWM fans just fine. But maybe PWM fans use less current?

Thanks X. Cloning second mono will be pain in the ***..

Would it be stupid idea to steal power to fans from psu's rectifiers? I have oversized trafo anyway, so wondering mostly that will they emit some **** in powerlines that will get to amplifier and cause buzzing and humming and all the other headaches? I'm trying to keep this as simple as I can, without nothing extra.

 

[xrk971]

Add CLC in between fan and your supply. About 470uF and 1mH 470uF (51ohm parallel withL) is what I use. Also 0.1uF 250v film cap bypass on those electrolytics. If you have the Aksa Lender Preamp it comes with a small CLC that both Vunce and myself use and it prvents noise from coming back. You can also just wire it P2P. You can also use 7812 in TO220 to drop your 35v to 12v. Or if higher voltage than LM317HV.

 

[AKSA]

Juntuin,

Terrific work! I like the fans bottom, amp above, power supply caps above that. Very elegant, almost like a guitar amp case.

With 37.5V supply you should get about 55W out of the BB. It will clip first on the negative rail, around -30V. This is 56W, impressive for a Class A. I'm amazed that the fans make no noise even at full tilt!

HD

 

[zman01]

Juntuin,

Good to see one channel up - nicely done!

 

[gaborbela]

Yes, it is a nice amplifier, I wish I could have the possibility to build something like that. Unfortunately, I can not do that while I live in an apartment on the kitchen table neither on the balcony. If you would accept an advice please Try to use as short and thick wires as possible especially between you PC boards and the capacitor banks. If is too far away because of the construction maybe use an extra pair high-quality caps just before your PC boards, like a pair M Lithic. Mr. Pass always advised us at DIY Aleph amps thick and short wired as possible. If you can do that a par extra caps like 10 000uF close to you PC boards.
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