Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 11th June 2019, 09:09 PM   #3201
danny_66 is offline danny_66  Belgium
diyAudio Member
 
danny_66's Avatar
 
Join Date: Jun 2005
Location: Lierde
Hi X,
I made a table last year,
here's the updated one with 0.15 sensor added, I settled on this version for 4R that I'll soon start building.

Code:
        | R131   | R132   | R128   |        |               
        | source | sensor | ccs-fb | bias   | speakers
--------|--------|--------|--------|--------|--------------
Alpha4R | 0.33   | 0.15   | 885    | 1.95A  | 4R-8R  
Alpha20 | 0.33   | 0.12   | 680    | 1.95A  | 4R-8R
Alpha20 | 0.33   | 0.11   | 640    | 1.95A  | 4R-8R
Alpha20 | 0.44   | 0.12   | 510    | 1.46A  | 8R  
Alpha20 | 0.44   | 0.11   | 480    | 1.46A  | 8R  
Alpha4R | 0.27   | 0.12   | 860    | 2.38A  | 4R  
Alpha4R | 0.27   | 0.11   | 790    | 2.38A  | 4R
If it is a 4R Alpha or a 8R Alpha is primarily defined by the R111 FB shunt resistor: 820R for 8R, 1k8-2k5 for 4R.
For a 4R you need minimum bias of 1.9A

Regards,
Danny
__________________
My RefSpeaker v2
  Reply With Quote
Old 11th June 2019, 09:16 PM   #3202
danny_66 is offline danny_66  Belgium
diyAudio Member
 
danny_66's Avatar
 
Join Date: Jun 2005
Location: Lierde
Quote:
Originally Posted by Shawnstium View Post
Should R121 and R122 (R19 & R22 in the LTspice one you made) also be changed to 50R?
Definitely not, the two 50 ohm resistors are not in the original schematic, they're extra resistors parallel to R132,
so you can change the damping factor of the Alpha, see this post.
__________________
My RefSpeaker v2

Last edited by danny_66; 11th June 2019 at 09:18 PM.
  Reply With Quote
Old 11th June 2019, 09:34 PM   #3203
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
Thank you Danny! I added a link to Post 1.
__________________
XRKaudio https://www.etsy.com/shop/XRKAudio
  Reply With Quote
Old 11th June 2019, 10:03 PM   #3204
AKSA is offline AKSA  Australia
diyAudio Member
 
Join Date: Sep 2001
Location: Melbourne, Australia
And thanks from me too Danny. This is very good table for the ALPHA 20 and gives it terrific versatility..

Hugh
__________________
Aspen Amplifiers P/L (Australia)
www.aksaonline.com
  Reply With Quote
Old 12th June 2019, 08:09 PM   #3205
Shawnstium is offline Shawnstium  United States
diyAudio Member
 
Join Date: Jun 2018
Location: New England
Whoa, those are really small changes in the resistor values and it makes my head spin! Are you measuring the resistors before installing them or are those the values listed on the parts you purchased/simulated? What kind of tolerances and temp coefficients are you using?

What do the different values of the CCS FB R128 do for the circuit?

I recall you posting a table (copied below) with different cap values for the different FB shunt R111. My guess is the cap values effects the gain in the VAS portion of the amp, with a higher value giving more gain. How did you come up with those recommend ratios and again what kind of tolerances are you looking at?

Gain settings: max. Vin for 17 Vout (max power):
Alpha20 with shunt fb 820r: 0.69 Vin
Alpha4R with shunt fb 1k8+68uf: 1.45 Vin
Alpha4R with shunt fb 2k2+56uf: 1.74 Vin (recommended, ratio H1-15/H1-4 = 99.74)
Alpha4R with shunt fb 2k7+47uf: 2.09 Vin
The FFT profile of the Alpha4R 2k2 looks a lot like the Alpha20 8R.
  Reply With Quote
Old 12th June 2019, 09:50 PM   #3206
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
The ABBB GB thread has been started:

The Alpha Big Boy with Buttah (ABBB) 52w Class A Amp GB
__________________
XRKaudio https://www.etsy.com/shop/XRKAudio
  Reply With Quote
Old 12th June 2019, 10:40 PM   #3207
AKSA is offline AKSA  Australia
diyAudio Member
 
Join Date: Sep 2001
Location: Melbourne, Australia
Shawnstium,

These are simulated values and they work well on the prototype. Not all these are tried, but they will always work well. In particular, the difficult value is R128, the fb CCS resistor. None of the values given in Danny's table alter the gain of the amplifier, which is set solely by R113 and R111 (22k/820R). These should be 1% tolerance.

R128 equalises the antiphase currents in the output devices so they show identical dynamic range, a few tens of mA to about 3.5A each at max output into 8R. Different for 4R load of course. These values are given, but it can be examined on a dual beam CRO at max output with a load. But they are easily derived using simulation, and they are accurate.

This is an open source amp. You are invited to build and play, and if you discover something significant, as Danny did, put it up and we will have a look at it. This amp is extremely tolerant of 'fiddling' and gives a consistent, almost invariant harmonic profile across many versions.

HD
__________________
Aspen Amplifiers P/L (Australia)
www.aksaonline.com
  Reply With Quote
Old 12th June 2019, 11:50 PM   #3208
Shawnstium is offline Shawnstium  United States
diyAudio Member
 
Join Date: Jun 2018
Location: New England
Thank you for the feed back. I have started the build of the 4R using 22k/2.2k for R113 and R111. Iíll try a couple values for the bypass cap for R111 and maybe a few R in 128.
Attached Images
File Type: jpg 66FA5A44-67BA-4B9B-93D8-DFEA0DE1584E.jpg (996.2 KB, 280 views)
  Reply With Quote
Old 13th June 2019, 03:42 AM   #3209
Vunce is offline Vunce  United States
diyAudio Member
 
Join Date: Jan 2014
Location: LI, NY
Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
Hello Alpha Builders,
Iíve remodeled my Alpha20 to utilize the new SLB psu and also added a regulated linear psu to power the PWM fan controller.
Iím happy to report that the ďremodelĒ was well worth it! The amplifier is much quieter at idle, almost silent. Revisiting this project has me thinking that Iíll build another set of boards following one of Dannyís 1.95A, 4R/8R models. (Thanks for all the Alpha20 modeling youíve done )

Vunce
Attached Images
File Type: jpg 16350C83-C3E9-4B48-B004-DED133AA1D93.jpg (1.01 MB, 323 views)
File Type: jpg 5F41A547-B598-4F77-9CD2-A3398B5ACE7A.jpg (994.1 KB, 274 views)
File Type: jpg 2533BCED-CD49-4043-AFBC-354C827A73BC.jpg (944.3 KB, 272 views)
File Type: jpg A5DEAA3F-DFC3-4B66-9BED-B9C074E17C1B.jpg (978.8 KB, 750 views)
  Reply With Quote
Old 13th June 2019, 05:12 AM   #3210
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
Nice work, Vunce!

Is that the nice super flexible 16ga silicone insulation RC model car wiring you are using between the SLB and the amps? Looks very low strain for how thick they are.

Click the image to open in full size.
__________________
XRKaudio https://www.etsy.com/shop/XRKAudio
  Reply With Quote

Reply


Aksa Lender P-mos Hybrid Aleph (ALPHA) AmplifierHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
AKSA's Lender Preamp with 40Vpp Ouput GB xrk971 Group Buys 456 20th September 2019 12:56 PM
AKSA's Lender Preamp with 40Vpp Output xrk971 Analog Line Level 1193 15th September 2019 02:03 PM
Aksa Lender HPA xrk971 Headphone Systems 115 13th July 2019 05:15 PM
Help newbie with low budget Magnificat/MLTL hybrid project AN8 + Eminence Alpha 10? klykx Full Range 1 9th October 2006 03:22 PM
AKSA vs Aleph or Aleph-X Prune Pass Labs 20 11th March 2004 03:05 PM


New To Site? Need Help?

All times are GMT. The time now is 05:09 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki