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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"RIAA Minimalist" Phono Transfer System Board Stuffing

Post by mediatechnology » Thu Jan 07, 2016 12:31 pm

When I designed the signal flow for the Phono Transfer System I knew that there were going to be people who wouldn't need the entire feature set. This post shows how to stuff the PC boards for RIAA playback only applications in situations where the Flat Balanced Input Preamp and RIAA EQ board are in the same chassis. If the preamp is going to be remotely located from the EQ board, then the preamp should be built with balanced outputs (IC2 and IC22) and THAT1240s should be installed on the EQ board at IC1 and IC2.

Mouser Project Manager BOMs for the "RIAA Minimalist" configuration.

The Mouser Project Manager BOM for the Flat Preamp Unbalanced Output Without ICs is here: https://www.mouser.com/ProjectManager/P ... d250c298a2
The Mouser Project Manager BOM for the "Minimalist RIAA" EQ Board Without ICs is here: https://www.mouser.com/ProjectManager/P ... 86fa03a88a

The high-lighted areas on the stuffing diagrams below are the components needed for RIAA playback.

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Phono Transfer System Flat Phono Preamp Board Stuffing for Unbalanced Output

Construction of the Flat Balanced Input Preamp is virtually identical with only a single THAT1240 common mode rejector IC needed per channel.
The inverting output is used to correct a signal inversion on the RIAA EQ monitor board.

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Phono Transfer System RIAA EQ Board Stuffing for Unswitched RIAA Playback

The RIAA EQ board has all of the line receiver ICs, and two line drivers removed.
The "-" input is used to receive signal from the preamp.
No relays or relay 12V regulator IC are required.
In addition to the balanced RIAA EQ output there are auxiallary RCA outputs for both the EQ'd and Flat signals.
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Gold
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Re: Phono Transfer System

Post by Gold » Sat Jan 09, 2016 5:32 pm

Here is the final Demo Unit build. Sort of. Wayne suggested using the line in to receive the preamp board and using the phono in to receive the line in. That way I can pad the line in with J2/IC5 so line in is unity gain. I had it wired up with phono in going to phono in before Wayne suggested this so I'm leaving it for now.

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Here are some tests with the RIAA EQ in. Looks pretty close.

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Re: Phono Transfer System

Post by Gold » Sat Jan 09, 2016 10:44 pm

I packed the demo unit up and brought it over to Josh Bonati Mastering this evening. I made a cable with an SME connector on it so it could plug right in to the SME 3012. He uses the later SAL74 drive rack for his VMS70. This would replace the phono pre integrated into the rack. We set it up and calibrated it in a few minutes. Josh has a Grado black on his lathe at the moment. The PTS was about 15dB quieter than the SAL74 pre. The noise that was there was buzz. The SME connectors had no shells or shielding. I think the noise can come down another 6-12dB so the noise floor is hiss.

The PTS swiss army knife strikes again. The SAL74 rack has three choices for monitoring. Input, Feedback Monitor and Phono. By using a separate unit as a phono pre he losses a monitor position on his transfer/monitor console, which he can't spare. He also uses a Technics 1200 as a QC deck. The 1200 takes a monitor position. We are going to feed the output of the 1200 phono pre to the line in of the PTS. I'm going to arrange it so that there is only one switch and it changes over from the lathe turntable to the 1200.

Josh is going to hold onto it for a little while, beat on it and see if he can find anything wrong.

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Re: Phono Transfer System

Post by mediatechnology » Sun Jan 10, 2016 6:34 am

Thanks Paul!

Glad you had an SME-style cable so it could plug right in.
I had a plastic shell DB-9 and did have to internally shield it with foil so I think that once the SME is shielded it will quieten it even further.
But I'll take the 15 dB over the SAL-74 any day.

On the subject of the SL-1200 I found those are pretty easy to modify for balanced.
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Flat Preamp Build for Vinyl Streaming

Post by mediatechnology » Thu Jan 14, 2016 4:03 pm

I had a the need to build a Flat Balanced Input preamp with XLR inputs and outputs for a vinyl streaming application and wanted to share the pics.

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Flat Balanced Input Balanced Output Moving Magnet Phono Preamplifier with XLR Inputs and Outputs, Top.

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Flat Balanced Input Balanced Output Moving Magnet Phono Preamplifier with XLR Inputs and Outputs, XLR Inputs.

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Flat Balanced Input Balanced Output Moving Magnet Phono Preamplifier with XLR Inputs and Outputs, XLR Outputs.

The umbilical cable is the DIN DC power connection.
A male DIN cable extends from the case due to the lack of panel real-estate.
The male DIN mates with the Meanwell power supply's DIN using a MIDI female-female turn-around.

The case is available from Pro Speaker Parts http://www.prospeakerparts.com/aluminum ... eries-xlrs
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jimwnyc
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Re: Phono Transfer System

Post by jimwnyc » Thu Jan 14, 2016 8:54 pm

So awesome, Wayne!! Really helped me out getting it to that enclosure. Talk about a clean install!!

To give folks on this forum some background on what I plan on doing, I'm going to employ the Flat Balanced input preamp within my real-time vinyl->digital playback setup.

I have a Technics SL-1200 that is in the process of being converted to balanced output. That (with a KAB Pro-S 30 MM cartridge) will feed Wayne's Flat Balanced input preamp. From there, the boosted signal will go to my TC Impact Twin audio interface to convert it to digital at either 24bit / 96khz or 24bit / 192khz. JRiver is my playback software and it allows for ASIO input and ASIO output from the same device. Soooo...that means, I have the vinyl input going into the Impact Twin and also coming out of the Impact Twin. But, a crucial element here is the RIAA correction. I'm handling that via an ultra-accurate bi-quad IIR VST plugin in JRiver. Also in JRiver, I'm doing de-clicking and have the option of room correction via convolution

The conversion to digital is ultra transparent and the benefits of manipulating the signal in the digital domain are immense.

I had used my turntable directly into the Impact Twin's hi-z inputs (padded down to 47k input impedance) but my cables were on the long side and since the hi-z inputs aren't balanced, I wasn't able to get that noise reduction benefit (so this set up was pretty noisy).

I want to really express my gratitude to Wayne. He's been incredibly helpful answering my many (MANY) questions and help with my install. I can't WAIT to use it and will definitely report back.

If anyone has any questions, please feel free to let me know!!

Jim

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Balanced Phono Preamp Tone Arm Wiring

Post by mediatechnology » Sun Jan 24, 2016 12:57 pm

I'm starting to get questions about how to wire tonearms fully-balanced for use with the Flat Phono Preamp.

A picture is worth a thousand words.

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Balanced Tone Arm Wiring Diagram for the Flat Phono Preamplifier.

Ground strap "A" should always be removed from the back of the phono cartridge.
Ground strap "B" depends.
If the turntable chassis is electrically noisy (e.g. a cutting lathe) then "B" should always be removed.
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SL-1200 Balanced Tone Arm Wiring

Post by mediatechnology » Mon Jan 25, 2016 7:14 am

Lots of folks have Technics SL-1200s and it turns out that modifying them for balanced tone arm wiring looks to be pretty simple.

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Technics SL-1200 Phono Cord PC Board.

There are 5 wires from the arm. The top black one grounds the wand.
The four cart leads float unless one of them is grounded by the cart itself.
(The cart's grounding clip should be removed if there is continuity to the headshell.)

Point "E" is where the TT frame ground, the wand ground, and spade lug wire meet.
A long screw is installed at "E" to carry ground to the arm base and maintain a grounded arm bearing.

The RCA leads can be replaced with individual shielded twisted pair.
The STP can be wired to the cart leads on the PC pads with the shields taken to point "E."
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Re: Balanced Phono Preamp Tone Arm Wiring

Post by JR. » Fri Jan 29, 2016 12:35 pm

mediatechnology wrote:I'm starting to get questions about how to wire tonearms fully-balanced for use with the Flat Phono Preamp.

A picture is worth a thousand words.

Image
Balanced Tone Arm Wiring Diagram for the Flat Phono Preamplifier.

Ground strap "A" should always be removed from the back of the phono cartridge.
Ground strap "B" depends.
If the turntable chassis is electrically noisy (e.g. a cutting lathe) then "B" should always be removed.
Sorry for the late comment but perhaps ground strap B1 and B2 could be small caps, as long as there is a low Z connection to ground inside the preamp. ?

JR
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Re: Phono Transfer System

Post by mediatechnology » Fri Jan 29, 2016 1:13 pm

Sorry for the late comment but perhaps ground strap B1 and B2 could be small caps, as long as there is a low Z connection to ground inside the preamp. ?
Thanks for the input.
They could.
B1 is often internal to the arm base but it's easy enough to change if someone is willing to do it.
I think most of us are pretty timid about doing anything on the underside.
I was.

The SL-1200 for example has the motor/frame ground, the spade lug, the wand ground and the bearing ground all meet at a PCB terminal and screw labeled "E."
One of the black wires (B1) in the pic could be removed from "E" and have a cap wired in series.
(Not sure which one it is.)

My SP-15 is wired with B1 and B2 open.
The platter is isolated from the arm.
"C" is tied so the shield is continued through the bearing and whatever internally shields the carbon fiber wand.
FGND separately carries the platter's return current to the preamp.

I'm curious to see how high an impedance I can put in series with FGND.
That would give me an idea of the platter leakage current which I bet is pretty low owing to it being AC-powered on a 2 wire cord.

I found however that once a fully-floating connection is established with shielded twisted pair, the balanced input pretty tolerant of both hum, buzz and RF.
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