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.
Gold
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Re: Phono Transfer System

Post by Gold » Tue Sep 22, 2015 3:16 pm

I removed the old Shure SE22 phono pre I was using today. I'm all in. I'm going to build a "demo unit" and pass it around. I'm very curious to get feedback from others (mostly cutters). First I need to finish restoring the lathe I'm supposed to deliver in six weeks...At least I got this build mostly out of my system.

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mediatechnology
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Re: Phono Transfer System

Post by mediatechnology » Tue Sep 22, 2015 4:32 pm

Gold wrote:I removed the old Shure SE22 phono pre I was using today. I'm all in. I'm going to build a "demo unit" and pass it around. I'm very curious to get feedback from others (mostly cutters). First I need to finish restoring the lathe I'm supposed to deliver in six weeks...At least I got this build mostly out of my system.
Thanks Paul for all the hard work!
Glad it was worthy of replacing the vintage Shure SE22.

Looks like I need to build another board and test my forthcoming assembly instructions.

Just finished updating the RIAA EQ Monitor Switcher schematic.
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Re: Phono Transfer System

Post by Gold » Tue Sep 22, 2015 5:46 pm

mediatechnology wrote:
Glad it was worthy of replacing the vintage Shure SE22.
It was no contest. This is not only quieter but sounds better.

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EQ Monitor Switcher on the Bench

Post by mediatechnology » Wed Sep 23, 2015 11:10 am

Thanks Paul! I really appreciate all the hard work you did.

Today is one of those rare moments that I got the work bench cleaned off enough to take a decent picture.
I'm about to build the last PC board set so the tidiness won't last long.

This is the "test jig" that I'm using until I box the EQ/Monitor Switcher:

Image
Phono Transfer System RIAA EQ Monitor Switcher on the Workbench

Connections

The soundcard/DAW connections are the RCA connections.
Red and Black feed the DAW A/D; the D/A output used for playback monitoring is Green and Yellow.

The connections to the monitor amp are Grey and Black.

The remote preamp tie lines are the grey shielded twisted pair.
The DC connections have a purple band.

Relay Mode Switching

I don't have switch connections to the relay coils made yet because for general listening they aren't needed.
The EQ Monitor Switcher powers up with all the relays NC.
When powered up, the phono input feeds flat to record and RIAA EQ to monitor.
For general listening or needle drops the Phono Transfer System "wakes-up" with it's input from the turntable and RIAA EQ applied to the monitor out.

The relay coils can be interconnected differently depending on how you in tend to use the unit.
The connections to the individual coils can be "wire or" or "diode or" by paralleling the coils directly or through diodes.

If flat recording is the norm, then the only relay requiring routine operation is RY2 which switches from monitoring the record path to monitoring the DAW output.

There are lots of possible routes through the inputs, EQ, Record and Monitor Outs:

Image
Flow diagram for Phono Transfer System with remote flat phono preamp and RIAA EQ monitor switcher.

Last night I listened to the A-Side of King Crimson's "In the Court of the Crimson King."
Amazing recording.
I've got some restoration work to do but probably not as much as if I had JR's copy. :lol:
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Gold
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Re: Phono Transfer System

Post by Gold » Tue Sep 29, 2015 1:19 pm

Here is a shot of the final build. There were some issues with bringing the A/B gain switch to the front panel so that was undone. I also did a bit of rewiring. I've never gotten the phono playback so close to sounding like the source before. I have the Denon DL103 almost unloaded. It's a 221kΩ in parallel with 100kΩ. My termination was changed.R2 and R3 to 1MΩ and R1 to 47kΩ.

Image

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mediatechnology
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Re: Phono Transfer System

Post by mediatechnology » Tue Sep 29, 2015 1:46 pm

Very nice Paul!
I'm so glad it's quiet and transparent.

What was the overall preamp/EQ gain with the LL1678 and DL-103 to get to +4 dBu?
Were the LL1678 in 1:16?

Who makes those ferrules?
That's what is needed with the Phoenix connectors.

I need to get a DL-103 soon to try with the active MC preamp.
I bet your preamp with the LL1678s are quieter.
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Re: Phono Transfer System

Post by Gold » Tue Sep 29, 2015 2:43 pm

mediatechnology wrote: What was the overall preamp/EQ gain with the LL1678 and DL-103 to get to +4 dBu?
I don't have an exact number because I tweaked the termination resistor by hand. Every time the value went up so did the level. The basic idea was to have 7cm/sec lateral produce -2dBu at the output of the preamp. Then make up the 6dB to produce +4dBu at the gain stage in the base station. That's basically the way it is. I undid the gain switch I had in the base station when I was sorting out my build. I plan on putting that back. So I would need 18dB of gain to get to my +12dB goal. When I was testing with the AP I had the source level set at -60dBu. That was about right to produce a +4dBu output. So somewhere in the neighborhood of 64dB of overall gain.
Were the LL1678 in 1:16?
Yes.
Who makes those ferrules?
That's what is needed with the Phoenix connectors.
I don't know. I get them from McMaster-Carr but I'm pretty sure Mouser sells them. They aren't expensive and worth every penny. http://www.mcmaster.com/#ferrule-terminals/=z5i5mt
I use a Wiha 32945 crimp tool. This is an insulated cusion grip. The plain vinyl grip is a little less expensive 32605

I need to get a DL-103 soon to try with the active MC preamp.
I bet your preamp with the LL1678s are quieter.
I'm quite happy with the setup as is. I don't see a big need for a transformerless MC pre. I guess it would be interesting to compare but I feel that this application is about as perfect as it gets for a transformer. I would like to try a Tamura MC transformer as I bet the DL103 was designed using one of those as the step up.
Last edited by Gold on Tue Sep 29, 2015 9:48 pm, edited 1 time in total.

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Re: Phono Transfer System

Post by mediatechnology » Tue Sep 29, 2015 4:02 pm

I thought the only justification for an active MC preamp module at this point might be cost.

It looks like the LL1678 is about $105 each? It might be comparable cost-wise too if it takes as many as 3-4X 1512/channel.
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Gold
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Re: Phono Transfer System

Post by Gold » Tue Sep 29, 2015 4:06 pm

mediatechnology wrote:I thought the only justification for an active MC preamp module at this point might be cost.

It looks like the LL1678 is about $105 each? It might be comparable cost-wise too if it takes as many as 3-4X 1512/channel.
That's right, from K&K Audio. The Jensen's are also about the same price.

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Re: Phono Transfer System

Post by mediatechnology » Mon Oct 05, 2015 8:29 pm

I was testing a unit today and ran some curves using the Lipshitz/Jung inverse RIAA network published in the TAA, 1/1980 issue.

(See: "A High Accuracy Inverse RIAA Network," The Audio Amateur, 1/1980. http://waltjung.org/PDFs/A_High_Accurac ... etwork.pdf)

The inverse RIAA network feeding the preamp is based on figure 3 without padding.

The first curve is the overall RIAA response curve with each channel individually driven.
The left and right response curves overlay.
Plotted with the frequency response curve is the interchannel crosstalk clearly below the noise floor.

Image
Phono Transfer System RIAA Frequency Response and Inter-channel Crosstalk

The subsonic response deviates from RIAA. The LF rolloff is user-selectable using the gain jumpers.

The following curve is the inter-channel RIAA equalization error.
I suspect that the rising response in the top octave is both an error in the inverse RIAA as well as analyzer filter error.

Image
Phono Transfer System Interchannel RIAA EQ Error

The maximum inter-channel response difference is about 0.05 dB at 200 Hz.
https://ka-electronics.com

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