Ortofon DS 522 feedback preamp
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Ortofon DS 522 feedback preamp
Hi,
can anyone suggest me a schematics on building preamp with feedback for Ortofon SD 522 cutterhead?
can anyone suggest me a schematics on building preamp with feedback for Ortofon SD 522 cutterhead?
- subkontrabob
- Posts: 284
- Joined: Fri Oct 30, 2009 5:40 am
- Location: Helsinki, Finland
Thank you very much. The tube design would be nice too! I will wait, there is no rush.subkontrabob wrote:if you're interested in a tube design, I could MAYBE scan the original schematics for the Ortofon GO 511 amp (complete cutting amp with tube power amplifier from circa 1950ies). Only problem is, they're not my property, and I'm currently 1500 km away, so you would have to wait a little.......
- subkontrabob
- Posts: 284
- Joined: Fri Oct 30, 2009 5:40 am
- Location: Helsinki, Finland
- dubcutter89
- Posts: 361
- Joined: Thu Oct 19, 2006 6:30 am
- Location: between the grooves..
Hey!
I've built one myself, but I don't have the schematic here right now...sorry
The structure was something like this:
1. The feedback amplifier - i made it using a single opamp in differential amp configuration with a gain of approx 40dB and an input resistance of approx 1kOhm. Maybe a standard mic pre will do the same...
2. The mixer - again a single opamp in (inverting) summing configuration. nothing special, just mixing the input (already RIAA encoded) with the output of the feedback amp. the level of the feedback has to be adjustable!
I also added buffer stages, but I think they are not necessary...
About the RIAA encoder you'll find some schemes in the forum...
For setting up a scope is a must (or at least very helpful). Also you should fuse the drive leads to your head with a little one (100mA) as the Ortofon is very fragile (200mA max continiuous current)
To verify the correct cabling (negative feedback) you could turn the feedback to zero, plug in everything, then turn up the feeback a little and watch it on the scope. If there is no signal it should be good. Maybe touch the stylus with your finger. You should see the touching, and afterwards again no signal. If it starts to oscilate (heavy signal) turn down the feedback or amp immediatly!!!
Hope this helps.
All the best,
Lukas
I've built one myself, but I don't have the schematic here right now...sorry
The structure was something like this:
1. The feedback amplifier - i made it using a single opamp in differential amp configuration with a gain of approx 40dB and an input resistance of approx 1kOhm. Maybe a standard mic pre will do the same...
2. The mixer - again a single opamp in (inverting) summing configuration. nothing special, just mixing the input (already RIAA encoded) with the output of the feedback amp. the level of the feedback has to be adjustable!
I also added buffer stages, but I think they are not necessary...
About the RIAA encoder you'll find some schemes in the forum...
For setting up a scope is a must (or at least very helpful). Also you should fuse the drive leads to your head with a little one (100mA) as the Ortofon is very fragile (200mA max continiuous current)
To verify the correct cabling (negative feedback) you could turn the feedback to zero, plug in everything, then turn up the feeback a little and watch it on the scope. If there is no signal it should be good. Maybe touch the stylus with your finger. You should see the touching, and afterwards again no signal. If it starts to oscilate (heavy signal) turn down the feedback or amp immediatly!!!
Hope this helps.
All the best,
Lukas
- organicmusic
- Posts: 26
- Joined: Fri Jan 18, 2008 1:49 pm
Re: Ortofon DS 522 feedback preamp
Hello,
did you ever found a shematic for Ortofon GO 511? I would need one also...
best regards,
Thorsten
did you ever found a shematic for Ortofon GO 511? I would need one also...
best regards,
Thorsten
- dubcutter89
- Posts: 361
- Joined: Thu Oct 19, 2006 6:30 am
- Location: between the grooves..
Re: Ortofon DS 522 feedback preamp
Hey!
Got the schemes, but want an amp - who has one for me?
@ Thorsten - probably time for a meeting soon!
@ Dovolis - would also love to meet, but affraid of the fighter jets...maybe pm
Lukas
Got the schemes, but want an amp - who has one for me?
@ Thorsten - probably time for a meeting soon!
@ Dovolis - would also love to meet, but affraid of the fighter jets...maybe pm
Lukas
Wanted: ANYTHING ORTOFON related to cutting...thx
Re: Ortofon DS 522 feedback preamp
GO511 i have never seen .
i have both the amps and the schematics. just no scanning assistance. one day the flokason book will be out with all in. but only GO541.( which was official amp for DS522 in most sales brochures datasheets. and how i received in combo with a DS681 many years ago. )
but i guess its same as ortofon always adapted their number DS522, DS641, DS681 all the same.
the main amp is minimlaistic. 4 tubes. input transofromer, feedback trafo. E80F, 2x E83F, 2x EL34 output transformer. basic schematics.
but there is no reason why not to go caruso preamp (i think you already do) just adapt the regulation a little.
except you want to go tube. that will not be better for sure.
if ever i might will go tube hybrid. the transformers make so much phase shift that a
good feedback regulation is not really possible. in all those years i was never satisfied with all the tube designs i have here. the GO541 sounds fantastic i have to say but it would sound even better with new design.
and i have all tube cutting amps/preamp systems here. neumann.ortofon. westrex. grampian.
if you compare what is possible today. but still open and interested if someone ever comes up with a good tube amp design.
bottleneck imo.is still the quality of stylis, tight holders. aged springs and coil. weak magents. diameter of coils.
we are dealing with 60-70 year old equipment and all this gives you the limitations. not the amps.
and of course the playback.
i have both the amps and the schematics. just no scanning assistance. one day the flokason book will be out with all in. but only GO541.( which was official amp for DS522 in most sales brochures datasheets. and how i received in combo with a DS681 many years ago. )
but i guess its same as ortofon always adapted their number DS522, DS641, DS681 all the same.
the main amp is minimlaistic. 4 tubes. input transofromer, feedback trafo. E80F, 2x E83F, 2x EL34 output transformer. basic schematics.
but there is no reason why not to go caruso preamp (i think you already do) just adapt the regulation a little.
except you want to go tube. that will not be better for sure.
if ever i might will go tube hybrid. the transformers make so much phase shift that a
good feedback regulation is not really possible. in all those years i was never satisfied with all the tube designs i have here. the GO541 sounds fantastic i have to say but it would sound even better with new design.
and i have all tube cutting amps/preamp systems here. neumann.ortofon. westrex. grampian.
if you compare what is possible today. but still open and interested if someone ever comes up with a good tube amp design.
bottleneck imo.is still the quality of stylis, tight holders. aged springs and coil. weak magents. diameter of coils.
we are dealing with 60-70 year old equipment and all this gives you the limitations. not the amps.
and of course the playback.
- dubcutter89
- Posts: 361
- Joined: Thu Oct 19, 2006 6:30 am
- Location: between the grooves..
Re: Ortofon DS 522 feedback preamp
The 511 was before the 541 and used different tubes (rimlock socket type instead of noval) and also has different design (different eq, different fb...)
There's even older ones but very little information around.
I'm always on the hunt for anything regarding our hobby so happy to become your scanning assistance
There's even older ones but very little information around.
I'm always on the hunt for anything regarding our hobby so happy to become your scanning assistance
Wanted: ANYTHING ORTOFON related to cutting...thx