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Old 3rd August 2010, 06:33 AM   #191
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I have the "little mongrel" done , the "PB60" (below - 1). Stuffed with enough capacitance (2 X 6800 - 10000uF / 30mm snap-in devices) to be a stand alone board ... just add a bridge , this little board will take all the X voltage boards (BX is next).

I LOVE MY NEW $20 SCOPE !!
I have been scoping traces on my Supersym and noticed that ripple increases drastically just centimeters away from the star ground. This influenced my design criteria for the new boards. The current pulses in the rails cancel out completely at a common center point . This I saw in a minor way with my small 60W amps but to a larger degree on my huge amp. THE LAYOUT IS IMPORTANT , visually confirmed...

Another observation is with the current balance in all my LTP's .... just a small adjustment in the current source (.1 - .2mA) makes all the difference in the world for the soundstage in ANY amp. Now all 4 of my DIY amps have the adjustable CCS. I truly wonder why this has not been common practice with amps on the forum. In simulation and backed up on my scope , sound quality and performance are worthy of this tweak , as well as the ability to adjust for different power supply rails. An adjustment range of 1 - 2 mA seems to cover all devices and rail voltages.

Below are the plots for the AX , BX , and CX (supersym 1) differential currents (Q1 and 2) ...with perfect balance the distortion is halved , mostly higher order stuff. This can be HEARD in real world , too !! The self amp ,the "AX" , is extremely good , but something about a current sourced VAS just doesn't sound as good. BUT ..I will try them again. BTW , the CX is doing 125V p-p at 20khz.

After seeing what these simple circuits can really do , I am going to build all 3
to swap them out on my PB250 board. They only cost about $ 10 apiece .. board and all.
OS

PS , The artwork for the CX1.1VB and PB250 (MY NEW AMP) are totally done and quadruple checked ,the most common mouser parts will fit perfectly and the BOM is done.
(3rd pix) How they go together.. he he
Attached Images
File Type: gif PB60_overview.gif (138.5 KB, 641 views)
File Type: gif current_balance.gif (70.2 KB, 606 views)
File Type: gif modular.gif (82.5 KB, 616 views)
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Old 5th August 2010, 12:12 PM   #192
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Hi ostripper!

Can you post the power board PB120?

Thank you.

Regards,
Paulo.
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Old 5th August 2010, 12:40 PM   #193
AKSA is offline AKSA  Australia
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Congrats from me too, Pete.

Great effort, exceptional results, elegant engineering.....

Hugh
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Old 5th August 2010, 01:18 PM   #194
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Giving the opportunity to compare three great amps is a great service to the DIY community.

Anatech has hinted elsewhere that a CCS can make a circuit sound worse, if it's a bad CCS. It might be interesting to try a different type of CCS, to confirm this? What do you say?

- keantoken
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Old 6th August 2010, 10:22 AM   #195
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Hi ostripper!

I apologise for my ignorance, but any of your power boards would work from +-50V rails? And the voltage boards, is it necessary to change resistor values for diferent power boards and voltage rails?

Thank you.

Regards,
Paulo.
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Old 6th August 2010, 05:23 PM   #196
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Nice work OS! I think I share your views of some aspects of this forum, but I've gotten in trouble for that before. I think I'd like to try some of your amps. I hope your troubles from last year are behind you!

Steve.
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Old 6th August 2010, 06:03 PM   #197
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Nice amp!

What´s limiting the slew? Output bipolars? Would MosFets in the output make the amp overall faster?

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Old 6th August 2010, 06:59 PM   #198
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Thanks for posting guys!! I won't bug "uncle charlie" anymore as this will give me time to finish all of these !!

I want these amps to be based on MATH and theory , as well as on the final listening experience. The AX , BX , CX and both powerboards PB60/250 ,I submit with the utmost confidence since they have already been built and simulated to "death" in the "mongrel labs".

The PB60/ 250 are totally finished.They have been reviewed/printed and triple checked for accuracy. You can download these in the ROOT of the mongrel folder as "PB60_schematic_artwork_Bom_complete.ZIP" and "PB250_schematic_artwork_BOM complete.ZIP".

They are smaller at about 1-2 megs but contain the main PCB 1200DPI artwork , parts placement , mirrored front board screenprint and detailed schematic and BOM. This took me a little longer to do because I wanted to perfect a "system" to facilitate further expansion. By the way the "CX1.1_ _schematic_artwork_BOM_complete.ZIP" is also in the "DONE" pile.

Quote:
By rising sun-I apologise for my ignorance, but any of your power boards would work from +-50V rails? And the voltage boards, is it necessary to change resistor values for diferent power boards and voltage rails?
The voltage boards will accommodate ANY voltage with a simple adjustment of the "CCS ADJ." trimmer provided, if you stuff the board with the 80/100V capacitors that are recommended. All the semiconductors are the High voltage types (120-300v) - Not BCxxx's , well over-rated for anything. The BC60 is more suited for 40-50V rails as It is just a "little amp" with 63V caps (smaller nichicon 22 mm w/10mm lead spacing or ALL the snap-ins which also have 10mm spacings).

The larger board (PB250)will do 80V rails provided you do use 100v electrolytic's , with 80v units 60-70V rails are recommended.

Quote:
Giving the opportunity to compare three great amps is a great service to the DIY community.

Anatech has hinted elsewhere that a CCS can make a circuit sound worse, if it's a bad CCS. It might be interesting to try a different type of CCS, to confirm this? What do you say?

- keantoken
Thanks , KEAN . If the don't like the CCS's (I heard little difference) they can do the BX (which will be my tribute to the ASKA). It will have the pads to do all sorts of mystical compensations or to leave the CCS out altogether. combine the BX with the PB250 and you will have an ASKA55 that will do 400w peaks!!

Quote:
By AKSA -Great effort, exceptional results, elegant engineering.....
You say elegant enginneering , NO machines are involved here ... all hand drawn , and mental layouts. I would ask you , after looking at a lot of layouts , are the parallel lines in the powerboards (especially the PB250) more prone to parasitics ?? I have seen this style in the quasi amps and many commercial offerings.

I do have the grounding "licked". By scoping real amps, what I have done on the powerboards is "state of the art " , giving almost ZERO hum and /or ripple at the 2 center nodes of the star(s). With the Capacitance multipliers on the 250 , the voltage boards "think" they have 10,000uF decoupling capacitors 47uF X 200Hfe = 10K = uV ripple).

There will be NO PB120 - Instead I will put out a 4 device vertical MOSFET offering (PBM 200).

The ones that are next in the "DONE BIN" are the AX and FX , being almost the same layout .. they are SO different . The AX is the standard blameless with it's .0002% distortion and the FX (KODA super pair).

OS
Attached Images
File Type: gif pb60 complete.gif (89.9 KB, 479 views)
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Old 6th August 2010, 07:23 PM   #199
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Quote:
Originally Posted by Rikard Nilsson View Post
Nice amp!

What´s limiting the slew? Output bipolars? Would MosFets in the output make the amp overall faster?

How much slew do you want ??? The 250 with the CX does 40+ V/uS symmetrical.

The "super pair" (Koda FX1.1 - not done) will do 53+ V/us. That is with a big lunky 100pF miller. (below) I am going to try the FX with the MOSFET board to use as a sub amp. I am still "scared" of the FX , as many have told me it is unstable.
OS
Attached Images
File Type: gif 53v_us.gif (17.3 KB, 430 views)
File Type: gif pb250.gif (73.9 KB, 138 views)
File Type: gif FX.gif (16.3 KB, 199 views)
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Last edited by ostripper; 6th August 2010 at 07:43 PM.
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Old 6th August 2010, 09:03 PM   #200
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Well, no offence, but I think reaching at least 100-200 v/us should not be that difficult. I did that myself with simpler circuitry than this. Still very impressed with the distorsion figures though!

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