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d
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Ortofon DS 522 feedback preamp

Post: # 13444Unread post d
Thu Mar 17, 2011 7:41 am

Hi,

can anyone suggest me a schematics on building preamp with feedback for Ortofon SD 522 cutterhead?

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subkontrabob
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Post: # 13447Unread post subkontrabob
Thu Mar 17, 2011 9:50 am

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.......

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d
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Post: # 13448Unread post d
Thu Mar 17, 2011 9:53 am

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.......
Thank you very much. The tube design would be nice too! I will wait, there is no rush.

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subkontrabob
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Post: # 13467Unread post subkontrabob
Fri Mar 18, 2011 4:39 am

d wrote: Thank you very much. The tube design would be nice too! I will wait, there is no rush.
Ok, let's see when I can get around to this.... 8)

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d
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Post: # 13468Unread post d
Fri Mar 18, 2011 4:41 am

thanks subkontrabob.

Also interested on a simple feedback preamp schematics for this type of head if anyone has...

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dubcutter89
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Post: # 13532Unread post dubcutter89
Sun Mar 20, 2011 6:30 am

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

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organicmusic
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Re: Ortofon DS 522 feedback preamp

Post: # 60363Unread post organicmusic
Sat Mar 05, 2022 12:46 pm

Hello,
did you ever found a shematic for Ortofon GO 511? I would need one also...

best regards,
Thorsten

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d
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Re: Ortofon DS 522 feedback preamp

Post: # 60364Unread post d
Sat Mar 05, 2022 1:31 pm

I am in the line here for 511 schematic please ;)
_______

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dubcutter89
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Re: Ortofon DS 522 feedback preamp

Post: # 60367Unread post dubcutter89
Sat Mar 05, 2022 1:59 pm

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
Wanted: ANYTHING ORTOFON related to cutting...thx

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flozki
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Re: Ortofon DS 522 feedback preamp

Post: # 60395Unread post flozki
Mon Mar 07, 2022 6:00 am

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.

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dubcutter89
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Re: Ortofon DS 522 feedback preamp

Post: # 60400Unread post dubcutter89
Mon Mar 07, 2022 9:02 am

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 :-)
Wanted: ANYTHING ORTOFON related to cutting...thx

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