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No-global-loop amplification
No-global-loop amplification
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Old 30th September 2017, 11:17 AM   #11
jwilhelm is offline jwilhelm  Canada
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We've been working on a preamp design that incorporates NGFB for the input buffer, and will likely use a NGFB headphone amp too (still to be designed and built).
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Old 30th September 2017, 11:22 AM   #12
BesPav is offline BesPav  Russian Federation
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Default No-global-loop amplification

Quote:
Originally Posted by vzaichenko View Post
Exactly, dual-diamond configuration with the diamonds, loaded to each other. Rather simple and efficient.

Valery, are you ever tried even simpler four-quadrant self-biased cascoded IPS like this?
IMG_6491.JPG

Or matched arrays like THAT340/ALD1103? Last one have dedicated substrate connection.

THAT1206 seem to have 7 kOhm at input in-series and could degrade noise performance in low-level applications.

Last edited by BesPav; 30th September 2017 at 11:25 AM.
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Old 30th September 2017, 12:56 PM   #13
vzaichenko is offline vzaichenko  Russian Federation
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No-global-loop amplification
Quote:
Originally Posted by dadod View Post
Valery, as always you have very good ideas how to design different amplifiers. You use diamond OPS here, how you do thermal compensation here, I never built any diamond power OPS yet (only for preamp)? How you get THD 0.002% if OPS alone has 0.05%?
I designed no GNFB but never built yet, to many project, have you built that one, if yes, how you like the sound?
This is my NGNFB amp and it uses current mirror with current gain of 2.12 GainWire-NGNFB-classB-PowerAmp
Those are my preamps with no GNFB, also uses current mirror. Current conveyor as a voltage amplifier and No NFB line amp (GainWire mk2)
Maybe you can get some ideas from it, like to use supper pairs.

P.S. pity you don't use LTspice
Hi Damir,

Good to see you here
Part of the circuit, shown on the schematic, does not include OPS - diamond on the right is the unity gain buffer. Connecting the OPS right to the transimpedance stage results in significantly higher level of distortion because of OPS's input impedance modulation. Buffer does the job perfectly.
So, distortion figures shown on the pictures are true for the front-end only.
NS-OPS dictates overall level of distortion at around 0.05%, running open loop.

Cheers,
Valery
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Old 30th September 2017, 01:02 PM   #14
thimios is offline thimios  Greece
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Quote:
Originally Posted by jwilhelm View Post
We've been working on a preamp design that incorporates NGFB for the input buffer, and will likely use a NGFB headphone amp too (still to be designed and built).
Yours test man is here
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Old 30th September 2017, 01:05 PM   #15
jwilhelm is offline jwilhelm  Canada
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Quote:
Originally Posted by thimios View Post
Yours test man is here
Still waiting for a shopping list for the other inputs.
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Old 30th September 2017, 01:50 PM   #16
vzaichenko is offline vzaichenko  Russian Federation
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No-global-loop amplification
Quote:
Originally Posted by jwilhelm View Post
We've been working on a preamp design that incorporates NGFB for the input buffer, and will likely use a NGFB headphone amp too (still to be designed and built).
Yep, this one incorporates a simpler unity gain buffer, particularly designed to match NS-OPS though
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Old 30th September 2017, 01:55 PM   #17
thimios is offline thimios  Greece
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Originally Posted by jwilhelm View Post
Still waiting for a shopping list for the other inputs.
I will do soon
These days NS is on my test bed again.
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Old 30th September 2017, 03:35 PM   #18
vzaichenko is offline vzaichenko  Russian Federation
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No-global-loop amplification
Quote:
Originally Posted by BesPav View Post
Valery, are you ever tried even simpler four-quadrant self-biased cascoded IPS like this?
Attachment 637998

Or matched arrays like THAT340/ALD1103? Last one have dedicated substrate connection.

THAT1206 seem to have 7 kOhm at input in-series and could degrade noise performance in low-level applications.
Hi Pavel,

Yes, I have used this kind of self-biased IPS arrangement, based on 2sk246/j103 pairs in one of X4 front-end options.

Noise - at low levels yes, but at line levels - no problem
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Old 1st October 2017, 05:11 AM   #19
vzaichenko is offline vzaichenko  Russian Federation
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No-global-loop amplification
Quote:
Originally Posted by thimios View Post
Yours test man is here
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Old 4th October 2017, 06:18 PM   #20
vzaichenko is offline vzaichenko  Russian Federation
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No-global-loop amplification
Arrow Diamondstark

Following Pavel's post, I have tested the concept with diamond IPS.

Initial setup did not include common base cascodes U8, U9 - overall distortion level was roughly 1/2 from what we've seen with differential pairs in place, still copying that initial profile.
The cascodes noticeably reduce 2-nd harmonic, improving overall performance, with 3-rd harmonic dominance. This configuration also shows rather good result in terms of IMD.

It's also cool to be able to use +/-15V regulated rails for IPS, allowing low-voltage complementary transistors.

Live performance is going to be slightly lower, strongly depending on components selection, as a number of important parts are either out of any NFB loop, or form the local loop itself.
Attached Images
File Type: jpg Diamondstark_1.0-Sch.JPG (293.6 KB, 585 views)
File Type: jpg Spectrum_1KHz_20V_RMS.JPG (85.3 KB, 564 views)
File Type: jpg Spectrum_20KHz_20V_RMS.JPG (87.2 KB, 523 views)
File Type: jpg Square-wave_20KHz_57Vpp.JPG (50.7 KB, 514 views)
File Type: jpg xIM_14-15KHz_20V_RMS.JPG (86.7 KB, 509 views)
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