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Old 10th October 2013, 03:30 AM   #11
wahab is offline wahab  Algeria
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Very nice and refreshing amplifier considering the "current"
subjectivists tendencies , it should allow very good perfs
that might well surprise some esoterics design afficionados...

No doubt that i ll give it a try in the simulator...

Stability would be greatly improved with say a 22pf from
collector to base of Q7.

Also , what happened to Q7/Q11.?.?..
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Old 10th October 2013, 04:54 PM   #12
wg_ski is offline wg_ski  United States
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That 22pf would add what would normally be a 'cdom' - in this case, extra phase shift. Since the amp is already lag compensated (R7 C5) this may or may not help stability. If you remove the lag comp, you need it or else. And maybe a higher value would be advisable.
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Old 10th October 2013, 05:30 PM   #13
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Default Sansui 3900/5900

Quote:
Originally Posted by wahab View Post
Very nice and refreshing amplifier considering the "current"
subjectivists tendencies , it should allow very good perfs
that might well surprise some esoterics design afficionados...

No doubt that i ll give it a try in the simulator...

Stability would be greatly improved with say a 22pf from
collector to base of Q7.

Also , what happened to Q7/Q11.?.?..
Here is the "truth" .

Attachment 1 is the amp section. The input stages (I tested them) are run by
a +/- 18VDC supply. It is strange they regulate the positive 18v from the amps main
V+ rail and derive just the negative 18V for Q1-2 from an auxiliary supply.

I might "clean up" the differential supplies and create two zener regulated
ones instead , it will make for a "standalone amp".

This is really a Sansui Z3900 , the PDF is too big.
You will notice the Sansui had a DC servo - I changed this into it's passive
equivalent.

OS
Attached Images
File Type: jpg z3900.jpg (211.3 KB, 698 views)
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Last edited by ostripper; 10th October 2013 at 05:34 PM.
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Old 10th October 2013, 06:43 PM   #14
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Default Zener supplies

Very good !

Lower distortion .... .008% THD20K 8R

Used 15V zeners with 2 simple follower trannies (below).
One pair of differentials (Q1-2) sees 12v and the other (Q3-4) 35V.
Many choices here !

Sansui made some economic choices and just "stole" existing supplies
for the differential to save $$$$ .

Much more stable , I can change the Q1-2 Ic over a much wider range without
oscillation now ,as well.

PS - scaled down R8-9 to 3K3 to keep things "vintage".... (-14.4VDC instead of -18VDC)

OS
Attached Images
File Type: jpg supplies.jpg (102.5 KB, 524 views)
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Last edited by ostripper; 10th October 2013 at 06:45 PM.
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Old 10th October 2013, 07:52 PM   #15
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Default OMG -Q7 and 11



But it actually simulated right -

I fixed this - and wow ! .001% 20k.

- Tiny glitch in the stages is gone , and the loop gain is "more normal"
(typical) 500k UG with 80+ margin....

-Q1-2 nearly superimpose (balanced)

-Q1-2 are 1ma , Q2-3 are 2ma , the VAS is 3ma.
The actual amp measures real close to this.

This is almost ready to FLY! (pcb)
PS- this amp's topology was actually able to compensate for 2 swapped E-C's !

New .ASC (below)

OS
Attached Files
File Type: asc GLA-v1.1.asc (14.7 KB, 48 views)
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Last edited by ostripper; 10th October 2013 at 07:54 PM.
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Old 11th October 2013, 05:17 PM   #16
ATAUDIO is offline ATAUDIO  Austria
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Hi, OS!
Very nice amp, indeed.
Probably I did not get it right, but it isn't a little too much 50 V rails for a single pair? I see that you have used good robust ONSemi outputs, but you can be sure that sooner or later somebody will hook some 4 Ohm speakers on it.
I would be tempted to put 3 pairs on output and call it a good 250 Watter!
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Old 11th October 2013, 09:01 PM   #17
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Quote:
Originally Posted by ATAUDIO View Post
Hi, OS!
Very nice amp, indeed.
Probably I did not get it right, but it isn't a little too much 50 V rails for a single pair? I see that you have used good robust ONSemi outputs, but you can be sure that sooner or later somebody will hook some 4 Ohm speakers on it.
I would be tempted to put 3 pairs on output and call it a good 250 Watter!
I'll design a single pair MJL21193/94 version first. Using the triple OP stage
demands it. That should give about 80W/channel (8R) ,the MJL's soa would also be good enough for a 4R load at 40V rails.

Solved the compensation issue. Standard miller comp. with a B-C capacitor
won't work with this amp !

Phase compensation -(R7/C5) of the first differential plus a little lead compensation from the VAS (R6) let's you "shape" the phase margin and unity gain point of the amplifier response curve. Harder ! , but a more elegant
approach. Original "vintage" (47R and .0022uf) values still gave a stable amp.

(below attachment)... this amp is compared to the standard "blameless".

Latest .ASC below - (with the "vintage" parts modeled) the performance came out real close to the OEM specs - but just a little better.

OS
Attached Images
File Type: jpg blame-vs-GLA.jpg (209.8 KB, 443 views)
File Type: jpg GLA1.1.jpg (109.8 KB, 411 views)
Attached Files
File Type: asc GLA-v1.1.asc (14.6 KB, 19 views)
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Old 11th October 2013, 09:45 PM   #18
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Default 400W "monster version"



Scales up VERY nicely. No troubles with THESE "tribbles" (triples).
- 6 pairs 21193/94

OS
Attached Files
File Type: asc GLA-monster.asc (19.3 KB, 52 views)
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Old 13th October 2013, 04:28 AM   #19
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Default GLAv1.2 (final)

All is wonderful ...

V1.2 is SO close to the Sansui 3900 , both in compensation and actual voltages.

(Attachment 1) is the final work.

My tweaks to C6 (lead comp.) and the "lag" comp. (R7/C5) are within range
of the original specs.
The simulation also allows for higher Hfe Zetex devices , 2n5401's , 2sa992's
or any other to-92 device for Q1-4.

Any to-220 (mje15032/33 , 2sa1837/2sc4793) as driver , and any OP device
..including the low gain/low Ft mjl21193/4... work very well with this amp.

R25 and 26 load the VAS , which gives a monotonically decaying harmonic
output.

The differentials and VAS are at such low current (no heatsinks),
I can squeeze this into a 76 X 102 mm board for the 70W version (attachment 2).
The main board will use njw TO-3P's as drivers !!

For those who want the "Frankenstein" version , attach the "GLAeX" PCB
(attachment 3).Run your 80V rails, you will have a 400W true triple OPS.

Also , the final .ASC is also below.

PCB's + the BOM will be done in the next few days.

OS
Attached Images
File Type: jpg GLAv1.2.jpg (129.5 KB, 411 views)
File Type: jpg GLAmain.JPG (203.5 KB, 265 views)
File Type: jpg GLAeX.JPG (339.4 KB, 157 views)
Attached Files
File Type: asc GLA-v1.2.asc (15.7 KB, 30 views)
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Old 13th October 2013, 07:36 AM   #20
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Wow, very nice map OS! The "Frankenstein" version is going to be my next project.

By the way, the name 'Survivor" reminds me of the 80s band that did the theme song "Eye of the Tiger" for Rocky III, a fitting name for a simple, rugged & quality amp.

Last edited by lloop9; 13th October 2013 at 07:42 AM.
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