Engl 520 preamp
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- schaublin65
- Posts: 88
- Joined: Sun Jul 08, 2012 11:59 am
- Location: Ireland
Engl 520 preamp
Hi,
I have been playing with this circuit for the last few evenings.
There is an interesting component I had not seen used in this way.
A small inductor between signal and ground.
It's a little black cube about 8mm on each side. Marked LT 3011/2.
I don't have an LCR meter so I will have to rig something up to measure what it's doing. Lifting one leg off the board it seems to make little enough difference.
Take care
John
I have been playing with this circuit for the last few evenings.
There is an interesting component I had not seen used in this way.
A small inductor between signal and ground.
It's a little black cube about 8mm on each side. Marked LT 3011/2.
I don't have an LCR meter so I will have to rig something up to measure what it's doing. Lifting one leg off the board it seems to make little enough difference.
Take care
John
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Re: Engl 520 preamp
It is an optoisolator. It is probably used for some kind of volume switching, but hard to tell without the whole schematic.
I Think I Think Too Much !
Re: Engl 520 preamp
Exactly. Here you can find photo and specs:
http://www.griotgroup.com/wp-content/up ... ors-07.pdf
http://www.griotgroup.com/wp-content/up ... ors-07.pdf
- schaublin65
- Posts: 88
- Joined: Sun Jul 08, 2012 11:59 am
- Location: Ireland
Re: Engl 520 preamp
Hi,
thanks for taking the time to reply.
I have edited my posts in this thread because they contained no useful information.
Old test equipment and confirmation bias is a troublesome combination.
The purpose of LT is presumably for stability when V3a is switched out.
Take care
John
thanks for taking the time to reply.
I have edited my posts in this thread because they contained no useful information.
Old test equipment and confirmation bias is a troublesome combination.
The purpose of LT is presumably for stability when V3a is switched out.
Take care
John
Last edited by schaublin65 on Sat Jun 13, 2015 9:50 am, edited 2 times in total.
Re: Engl 520 preamp
This is the schematic, but it's not 100% correct.
http://milas.spb.ru/~kmg/files/schemati ... ematic.pdf
[img850]http://rudn.nodevice.com/preview/big/372/372820-1.jpg[/img]
http://milas.spb.ru/~kmg/files/schemati ... ematic.pdf
[img850]http://rudn.nodevice.com/preview/big/372/372820-1.jpg[/img]
- schaublin65
- Posts: 88
- Joined: Sun Jul 08, 2012 11:59 am
- Location: Ireland
Re: Engl 520 preamp
Hi
post edited, see fourth post in thread
post edited, see fourth post in thread
Last edited by schaublin65 on Sat Jun 13, 2015 7:29 pm, edited 2 times in total.
Re: Engl 520 preamp
Have you tried to place a capacitor in parallel to the inductor, and calculate its value once you have determined the resonance frequency?
- schaublin65
- Posts: 88
- Joined: Sun Jul 08, 2012 11:59 am
- Location: Ireland
Re: Engl 520 preamp
Hi,
sine wave generator recap in progress...
[img1536]http://i.imgur.com/6ugGJHo.jpg[/img]
take care
John
sine wave generator recap in progress...
[img1536]http://i.imgur.com/6ugGJHo.jpg[/img]
take care
John
- schaublin65
- Posts: 88
- Joined: Sun Jul 08, 2012 11:59 am
- Location: Ireland
Re: Engl 520 preamp
Hi,
post edited, see fourth post in thread
post edited, see fourth post in thread
Last edited by schaublin65 on Sat Jun 13, 2015 7:30 pm, edited 2 times in total.
- schaublin65
- Posts: 88
- Joined: Sun Jul 08, 2012 11:59 am
- Location: Ireland
Re: Engl 520 preamp
Hi,
post edited due to strange results from these
[img:542:720]http://i.imgur.com/wJYnI8r.jpg[/img]
more work required
post edited due to strange results from these
[img:542:720]http://i.imgur.com/wJYnI8r.jpg[/img]
more work required
Last edited by schaublin65 on Sat Jun 13, 2015 7:34 pm, edited 1 time in total.