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-   -   new discrete opamp for line preamplifier (http://www.diyaudio.com/forums/analog-line-level/228672-new-discrete-opamp-line-preamplifier.html)

scafas 26th January 2013 09:29 AM

new discrete opamp for line preamplifier
 
Hello everyone, I built this operational transistor and let me know which circuit and 'suitable to build a line-stage preamplifier.
must be supplied with dual voltage and the more 'simple as possible.
I tried to replace it with a NE5532 and I can say that it works very well but I would like a circuit that uses all its potential
http://www.pcb-audio.com/pcb-audio_c...p-discrete.png
http://www.pcb-audio.com/photos/op-amp-008.jpg
http://www.pcb-audio.com/photos/op-amp-003.jpg

it's use bc550c /bc560c and bd135-bd136
tks

linuxguru 26th January 2013 11:36 AM

This topology gives excellent results (it's similar to the Jensen JE990, but complimetary) - a few improvements are possible:

1) A current mirror on the LTP helps increase loop gain as well as equalize input offsets at the LTP.

2) Instead of a Darlington VAS, and emitter-follower driving a common-emitter VAS gives better results with the same number of transistors.

3) The Miller compensation may be referenced to the output (Cherry compensation), rather than the collector of the VAS, and helps reduce distortion of the output stage also.

scafas 26th January 2013 08:39 PM

opamp jensen
 
Quote:

Originally Posted by linuxguru (Post 3342920)
This topology gives excellent results (it's similar to the Jensen JE990, but complimetary) - a few improvements are possible:

1) A current mirror on the LTP helps increase loop gain as well as equalize input offsets at the LTP.

2) Instead of a Darlington VAS, and emitter-follower driving a common-emitter VAS gives better results with the same number of transistors.

3) The Miller compensation may be referenced to the output (Cherry compensation), rather than the collector of the VAS, and helps reduce distortion of the output stage also.

Can you explain with a diagram maybe intervening on my drawing?
the schematic it's a clone of jensen 918

scafas 21st January 2015 10:13 AM

new clone
 
Quote:

Originally Posted by scafas (Post 3342812)
Hello everyone, I built this operational transistor and let me know which circuit and 'suitable to build a line-stage preamplifier.
must be supplied with dual voltage and the more 'simple as possible.
I tried to replace it with a NE5532 and I can say that it works very well but I would like a circuit that uses all its potential
http://www.pcb-audio.com/pcb-audio_c...p-discrete.png
http://www.pcb-audio.com/photos/op-amp-008.jpg
http://www.pcb-audio.com/photos/op-amp-003.jpg

it's use bc550c /bc560c and bd135-bd136
tks

this is my new clone with lower dimension pcb
http://i38.servimg.com/u/f38/15/04/21/15/op-jen10.jpg

linuxguru 21st January 2015 04:02 PM

Very nice - I use a similar kind of construction in my LF03c discrete dual opamp. You can save some space by using 1/8W resistors like Dale ERL/RLR05 at some locations where the dissipation permits it.

scafas 21st January 2015 04:21 PM

Quote:

Originally Posted by linuxguru (Post 4194056)
Very nice - I use a similar kind of construction in my LF03c discrete dual opamp. You can save some space by using 1/8W resistors like Dale ERL/RLR05 at some locations where the dissipation permits it.

now i can same more space with a new pcb design.
so i have a 27x30mm max. ,, very good for replace some ic-standard operational amplifier.

scafas 21st January 2015 04:33 PM

pcb for sale
 
i've some pcb of this clone , if interest contact me.
the kit is composed of 3 pcb.

Blondie 13th February 2015 06:40 PM

I'm curious how this opamp play. I hope that one day will be available for purchase this prototype. Regards!

scafas 16th February 2015 06:01 AM

Quote:

Originally Posted by Blondie (Post 4222941)
I'm curious how this opamp play. I hope that one day will be available for purchase this prototype. Regards!

you can :
operazionale. a discreti jensen 918 clone | eBay

Joffe 23rd February 2015 07:10 AM

I would guess this will work fine on +24/-24 V rails as well.
Have you tried? Does it get warm (unloaded)?


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