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GreenAmp ++ modulated Class G output
GreenAmp ++ modulated Class G output
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Old 17th January 2019, 10:40 AM   #1
ostripper is offline ostripper  United States
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Default GreenAmp ++ modulated Class G output

OK , back to the "stuff".


(Below 1) is my input-VAS stage.



It is a full complimentary LTP (leach - like) combined with the "special sauce"

of a Baxandall super-pair / hawksford cascode VAS.


- Easy PPM performer ! Have to load it down to 2R to break 10ppm. Typically ,
sub ppm from 10K down.
-Self clamping saturation at clip , I will show this later. At 1% OMG clipping ,
all even order (like a Valve amp).


I will combine this with a error correcting - (modulated) CLASS G output stage. I will
show this in all its fast modulated goodness in my next few entries.
80% efficiency , little heat ,, here we come ... could go lateral MOSFET , as well.
SMPS is also the recommended supply.


This will be a full amplifier in the final form , it may start as a modular in it's
test phase .

OS
Attached Images
File Type: jpg greenamp V1.jpg (376.4 KB, 1418 views)
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Old 17th January 2019, 11:45 AM   #2
ostripper is offline ostripper  United States
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Default clipping and anti saturation

(below 1) is gross overload , the IPS will run cooler , like a "greenamp" should.


(below 2) is what to expect with a better output stage. An error correcting
output stage has 1/10th the THD (for NFB) to correct. This greenamp IPS
is a "distortion eater" , nearly sub - ppm in isolation.


I ALMOST have the GEC = (G class error correcting) OP stage done.
The greenamp IPS should have no problem "eating" it's distortion.


OS
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File Type: jpg greenamp V1 clip . sat.jpg (129.2 KB, 1429 views)
File Type: jpg greenamp V1 IPS.jpg (77.1 KB, 1315 views)
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Old 17th January 2019, 01:05 PM   #3
sajti is online now sajti  Hungary
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Interesting! Can't wait for the class G output!

Sajti
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Old 17th January 2019, 03:40 PM   #4
BesPav is offline BesPav  Russian Federation
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Nice approach!

But, some questions:
1. Why noninverting?
2. What will be CMRR?
3. What will be PSRR?
4. Why IPS CCS (Q5/Q6) aren’t cascoded?
5. Where D3/D4 reference filters?
6. Why righ shoulder of the LTP’s aren’t used? Put mirror there.
7. Why so small active LTP shoulder load(R19/R21) are? Again put mirror.
8. Followers (Q7/Q11) - clearly and exactly!
9. Why VAS stage hybrid driven? Redraw as common base.
10. Why last VAS stage are supplied by low-voltage rails?
11. Where are VAS load resistance? What nominal of RC-circuit?
12. Where base stoppers at first stage of output follower?
13. 2SA1381 drive MJL4302 - mouse pick a trailer. Add at least KSA1220A inbetween.

To be cont’d...
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Old 18th January 2019, 03:56 PM   #5
ostripper is offline ostripper  United States
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Default Class g woes ....

I have simulated successfully , but more THD and "glitches" beyond 10k.


Here (below) , are the .ASC + models.


The greenampV1 is the bada$$ input stage running a triple OP.
The greenampV1-ops is the class G trial run.


BTW - the GOAL is to produce a 200W amp with 1/2 the heatsink requirements
running on a SMPS in a 1U enclosure.
AMP will be 4 devices (2 steps + 2 active) , I expect to at least come close to
EF3 performance.

PS - Does anybody have the models for the Exicon lateral MOSFET's ? Exicon Lateral MOSFETS - Our Product Range
With these , more class A bias before the class G stepping (pix below)

OS
Attached Images
File Type: jpg greenampV1-OPS.jpg (259.4 KB, 1186 views)
Attached Files
File Type: asc greenampV1.asc (31.9 KB, 40 views)
File Type: asc greenampV1-ops.asc (26.1 KB, 32 views)
File Type: txt KT-Cordell models.txt (57.3 KB, 31 views)
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Old 18th January 2019, 04:08 PM   #6
sajti is online now sajti  Hungary
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Hi,

try faster driver for the outer devices, such as 2SC4793/2SA1837. My solution has extreme small glitch in the simulator.

Sajti
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File Type: png class_G_10k.png (111.2 KB, 1180 views)
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Old 18th January 2019, 04:11 PM   #7
dadod is offline dadod  Croatia
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Quote:
Originally Posted by ostripper View Post
PS - Does anybody have the models for the Exicon lateral MOSFET's ? Exicon Lateral MOSFETS - Our Product Range
With these , more class A bias before the class G stepping (pix below)

OS
Attached Files
File Type: txt Hegglun-Lateral-models2.txt (4.3 KB, 67 views)
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Old 18th January 2019, 04:44 PM   #8
ostripper is offline ostripper  United States
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Quote:
Originally Posted by sajti View Post
Hi,

try faster driver for the outer devices, such as 2SC4793/2SA1837. My solution has extreme small glitch in the simulator.

Sajti

I did try the C4793/A1837 pair.


If you run the simulation , you will see the negative step is not going symetrically
with the positive one. More load also makes thing worse.
Hitachi had a line of receivers and amps (sr-200x) that used 4 devices. 230W
@ 40 + 90V rails. They used the driver side to initiate the pos/neg step instead
of output local FB like this iteration.


The local FB of this class G stage adds another pole globally to the amp as a whole.
I did get my IPS to oscillate. Instability in the local OP FB.



I still have quite a few tricks left !!!


Edit - Thanx much , Dadod !!

OS
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Last edited by ostripper; 18th January 2019 at 04:47 PM.
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Old 18th January 2019, 04:49 PM   #9
ostripper is offline ostripper  United States
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Quote:
Originally Posted by sajti View Post
Hi,

try faster driver for the outer devices, such as 2SC4793/2SA1837. My solution has extreme small glitch in the simulator.

Sajti

Submit your .ASC, .... please.
All "tricks " are welcome.


OS
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Old 18th January 2019, 05:01 PM   #10
ostripper is offline ostripper  United States
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Quote:
Originally Posted by BesPav View Post
Nice approach!

But, some questions:
1. Why noninverting?
2. What will be CMRR?
3. What will be PSRR?
4. Why IPS CCS (Q5/Q6) aren’t cascoded?
5. Where D3/D4 reference filters?
6. Why righ shoulder of the LTP’s aren’t used? Put mirror there.
7. Why so small active LTP shoulder load(R19/R21) are? Again put mirror.
8. Followers (Q7/Q11) - clearly and exactly!
9. Why VAS stage hybrid driven? Redraw as common base.
10. Why last VAS stage are supplied by low-voltage rails?
11. Where are VAS load resistance? What nominal of RC-circuit?
12. Where base stoppers at first stage of output follower?
13. 2SA1381 drive MJL4302 - mouse pick a trailer. Add at least KSA1220A inbetween.

To be cont’d...

I will answer all these questions after I get the OP stage. This IPS will
work , already built "slewmaster" Slewmaster - CFA vs. VFA "Rumble"
search for "kypton C" and "spookyamp" , this IPS is the hybrid of the two.
OPS will have cap multipliers , the spooky had close to -100db PSRR
with the "slewmaster" output stage/cap multiplier combo.


PS - I simplified the Leach/Spooky LTP stage so more would build it.
The Spooky had over 100 components , I built it ... but most went for the far simpler
CFA IPS's.



OS
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Last edited by ostripper; 18th January 2019 at 05:04 PM.
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