Phono Transfer System Construction Information

Construction information for DIY projects, including the MS Mid Side Matrix, Elliptic Equalizer, Mastering Console, Phono Transfer System, Insert Switcher and the Dual Class-A Amplifier. You can post your baby pictures here.
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mediatechnology
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Re: Phono Transfer System Construction Information

Post by mediatechnology » Thu Jul 22, 2021 4:21 pm

For both 15 and 30 IPS?

I see what I think is a bias trap in the preamp front end.
Does this machine record?

Can you send me some large-format scans by email?
I can assemble them back into a big image.
I'm wondering if we could put the MM at the headstack and then use the EQ on the existing board.
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Gold
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Re: Phono Transfer System Construction Information

Post by Gold » Fri Jul 23, 2021 11:51 am

mediatechnology wrote:
Thu Jul 22, 2021 4:21 pm
For both 15 and 30 IPS?

Anything will do. Just one setting will work. This would just be for 'proof of concept'. As long as I can hook it up and play a tape it will give me enough information to know whether I want to pursue this further. I know there won't be adjustable Hi and Lo frequency adjustments. What I will be listening for doesn't have much to do with frequency response. As long as it's close it's good enough. If one speed and curve is easier get with the existing RIAA EQ then that's the one.
I see what I think is a bias trap in the preamp front end.
Does this machine record?
Playback only. For the preview decks.

Can you send me some large-format scans by email?
I can assemble them back into a big image.
I'm wondering if we could put the MM at the headstack and then use the EQ on the existing board.
Sure, I will have to rescan them as I altered the original scans.

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mediatechnology
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Re: Phono Transfer System Construction Information

Post by mediatechnology » Sun Jul 25, 2021 5:56 pm

Sure, I will have to rescan them as I altered the original scans.
A road map should would help. Thanks!
https://ka-electronics.com

Covidland (The Movie) Part 1: Lockdown https://banned.video/watch?id=615f96b3aa816336dbd21792

Directing Orson Welles: "What Is It That You Want?": https://waynekirkwood.com/content/Orson ... u_Want.mp3
Americas Frontline Doctors Lawsuit Motion For Preliminary Injunction Of Covid-19 Vaccine Emergency Use Authorization: https://waynekirkwood.com/images/pdf/Am ... zation.pdf

crin
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Re: Phono Transfer System Construction Information

Post by crin » Mon Jul 26, 2021 10:24 am

since i don't know which model of A80 you're talking about, i have put all Studer A80 repro amp schematics from the service manuals i could find as PDFs on my server:
i think the schematic you're looking for is in the A80 VU Mk II … IV file.

hth, ©
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that shouldn't be in charge of brooms
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Gold
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Re: Phono Transfer System Construction Information

Post by Gold » Mon Jul 26, 2021 12:03 pm

crin wrote:
Mon Jul 26, 2021 10:24 am

i think the schematic you're looking for is in the A80 VU Mk II … IV file.
That's correct. I have three A80VU Pre. They are not strictly any vintage. My 1/4" machine has the MkI frames with the Weston meters but the electronics are MKII. I'm not sure about all the differences between models mechanically. I think later machines had two light barriers. The 1/4" and 1/2" machines only have one light barrier. The 1" Preview machine has two light barriers. That one was put together from a 1" layback transport with older (MKII I think) electronics. All the bearings, dashpots, brake bands and drums and other mechanical stuff was band new as of about seven years ago. They see good use (except for the 1") but are not run all day every day.

Thanks for posting the schematics in a readable form.

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mediatechnology
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Re: Phono Transfer System Construction Information

Post by mediatechnology » Mon Jul 26, 2021 12:40 pm

Studer made a layback machine?
Wow, that brings back memories of the MCI JH-110 1" layback I used to have to maintain at DSL.

The A80 VU Mk II … IV looks to have a low impedance head transformer-coupled to the preamp.
The MC preamp might be a better fit.
https://ka-electronics.com

Covidland (The Movie) Part 1: Lockdown https://banned.video/watch?id=615f96b3aa816336dbd21792

Directing Orson Welles: "What Is It That You Want?": https://waynekirkwood.com/content/Orson ... u_Want.mp3
Americas Frontline Doctors Lawsuit Motion For Preliminary Injunction Of Covid-19 Vaccine Emergency Use Authorization: https://waynekirkwood.com/images/pdf/Am ... zation.pdf

Gold
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Re: Phono Transfer System Construction Information

Post by Gold » Mon Jul 26, 2021 1:28 pm

I have the low impedance heads on my 1/2" machine. I have high impedance heads on the 1/4". I can scan that one too. It has a 1:10 step up transformer that is terminated on the secondary with a 180K resistor in parallel with a 33p capacitor. After the front end it's exactly the same as the posted schematic.

Gold
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Re: Phono Transfer System Construction Information

Post by Gold » Mon Jul 26, 2021 10:37 pm

mediatechnology wrote:
Mon Jul 26, 2021 12:40 pm
Studer made a layback machine?
Wow, that brings back memories of the MCI JH-110 1" layback I used to have to maintain at DSL.

The 1” Preview deck was pieced together from the 1” layback machine and a 1/4” parts machine. I got the layback machine in Toronto. It was missing the headstack. That and no one needs a layback machine made it cheap and worth the drive. I stayed overnight with the folks in Buffalo on the way there and back so it was easy.

The 1/4” parts machine came from Sony W54th St studios. I got one and a half 1/4” preview machines at the auction. The complete 1/4” machine stayed that way. Dan Zellman put together the 1” deck with John French making the headstack.

Dan isn't doing house calls anymore. Midnight Bob Shuster is maintaining the machines now. He maintained them at Sony too.

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