Flat Phono Preamp Based on John's P10 and 2SK389

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JR.
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by JR. » Mon Aug 24, 2015 10:50 am

mediatechnology wrote:I'm really curious - in fact dying to know - what the last LP was that you listened to John.
After you remove the dust please tell us.
I flipped it over to read the other side...King Crimson, in the court of the crimson king. A good album to crank VERY loud. 8-)

The last several times I fired up the record player was after several beers and revisiting some of my old vinyl from the 60's-70s.

I bought the king crimson album after accidentally seeing them live. They were the opening act for the Doors at a concert back in the '60s. In fact I saw the Who as an opening act for the Doors, another opener Linda Ronstadt (stoned ponies)

I've been doing a few needle drops of stuff that was best forgotten.
There were a lot of bands then (the 70s) that sound like Spinal Tap.
I hear those records today and think "I hope I got this as a promo."

There's one LP's credits I looked at that had a quote from a label exec that said: "It takes $15,000 to make a hit album. That's why I'm giving you ten."

Then there's the Joe Sample Carmel album I rediscovered.
Made digging through the other ten worth it.
Here's a youtube of a song from one of my more obscure albums. I don't know if you'll enjoy a first listen but one of my favorites from back in the day and I'm enjoying the hell out of hearing again. :D :D :D :D (lots of subtle humor and 60's references in his rap).

https://www.youtube.com/watch?v=D1JbQcoy7t4

I have albums from a few obscure Boston bands I saw live in clubs or free concerts around town. I recall seeing Emerson lake and palmer free at the half shell. Mahavishu orchestra played a free concert on the boston commons.

I wonder how much of my old vinyl I can google up? nah... I have work I should be doing. Maybe tonight after a few beers. 8-)


JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by Gold » Wed Aug 26, 2015 10:25 am

mediatechnology wrote:I'm very close to hitting the "submit" button for a small ProtoPro order on the EQ/Monitor switcher.
While setting levels using test tones from the CBS STR-100 disc I noticed something very curious: MM cartridge crosstalk (1kHz AT AT-96) is out of polarity.
Left-only modulation is producing a right channel output about -20 dB down exactly out-of-polarity.
I think this may have to do with disc mechanics.
What occurred to me seeing out-of-polarity crosstalk is that a cart may measure 20 dB separation based on level, but it will sound far wider, and produce more apparent separation, than what it actually measures.
An in-polarity crosstalk component will pull left and right together, an out-of-polarity crosstalk component pushes them further apart.
This may have been a trick used by the designers of stereo phono playback.
You are blowing my mind. Fantastic!
While playing around with the jumpers and monitoring the flat output on the oscilloscope I can see the ultrasonic HF material "bloom" on the scope if the cartridge does not have enough Cload.[/color]

Most people playing around with loading have to listen (or monitor with instruments) the RIAA-EQ'd output.
Monitoring un-EQ'd output the differences are profound.
The HF material on the 'scope literally explodes as the cart begins to resonate.

With no added Cload cymbal crashes screech like fingers on chalkboards and there is audible mistracking.
The scope has HF material way off-scale.
Add 50-100 pF and it sounds sweet again and HF energy returns to normal.
Ultimately I decided on 100 pF and 47K.
You are blowing my mind again. Stellar work.

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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by mediatechnology » Wed Aug 26, 2015 11:16 am

+1 saloom, sinclair & the mother bear // marie la peau

Wow, really out there. Reminds me of Arlo Guthrie's Alice's Restaurant morphing into a rock opera.
You Tube segued into the entire album side.
King Crimson, in the court of the crimson king. A good album to crank VERY loud.
Yep, in the stack to play.
Mine is probably too worn out to transfer.

About that out-of-polarity crosstalk thingy...

I had someone contact me via ebay recently wanting to use the Stereo Width Controller to blend Phono playback to partial Mono.
Width would be something less than 100%.
The objective was to restore imaging lost due to playback crosstalk.
(Another was the apparent warp/rumble reduction by steering the LF artifacts to mono.)

It makes perfect sense now - partially blending to mono the out-of-polarity crosstalk actually reduces the crosstalk.
Though it's undoubtedly frequency-dependent I suspect that over the midrange some fairly significant crosstalk reductions could be made to happen.

I'm curious to see if other MM and MC cart topologies besides the AT torroidal have out-of-polarity crosstalk.
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by emrr » Wed Aug 26, 2015 1:22 pm

mediatechnology wrote: It makes perfect sense now - partially blending to mono the out-of-polarity crosstalk actually reduces the crosstalk.
Off topic, this sounds like the noise reduction trick you can use on mono tape recordings when played back with stereo heads. Separate mid from side and lose the sides. Or adjust the balance of the two if something is lost in the removal.
Best,

Doug Williams
Electromagnetic Radiation Recorders

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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by JR. » Thu Aug 27, 2015 11:41 am

mediatechnology wrote:+1 saloom, sinclair & the mother bear // marie la peau

Wow, really out there. Reminds me of Arlo Guthrie's Alice's Restaurant morphing into a rock opera.
You Tube segued into the entire album side.
Most of my albums are more conventional songs, That guy can draw a vivid picture but his stream of consciousness patter sounds like a little too much LSD usage.
King Crimson, in the court of the crimson king. A good album to crank VERY loud.
Yep, in the stack to play.
Mine is probably too worn out to transfer.
My copy isn't very bad, ignoring the layer of dust obscuring one side. :lol: :lol: It wasn't in heavy rotation back in the day. My old albums are lucky to have covers, and a roommates dog didn't chew them up. After parties in the '60s we would pick up the albums off the floor...so footprints too.

I listened to whole solloom sinclair youtube, (and really enjoyed it). I heard one fairly loud record scratch/tick in one cut. Only one though so a respectable dub.
About that out-of-polarity crosstalk thingy...

I had someone contact me via ebay recently wanting to use the Stereo Width Controller to blend Phono playback to partial Mono.
Width would be something less than 100%.
The objective was to restore imaging lost due to playback crosstalk.
(Another was the apparent warp/rumble reduction by steering the LF artifacts to mono.)

It makes perfect sense now - partially blending to mono the out-of-polarity crosstalk actually reduces the crosstalk.
Though it's undoubtedly frequency-dependent I suspect that over the midrange some fairly significant crosstalk reductions could be made to happen.

I'm curious to see if other MM and MC cart topologies besides the AT torroidal have out-of-polarity crosstalk.
Now that sounds like a useful trim if it can improve actual cartridge playback accuracy.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by mediatechnology » Thu Aug 27, 2015 4:20 pm

Got the pre-production run of boards in and they checkout OK.

Image
RIAA EQ/Flat Dual Path Monitor Switcher for the Flat/RAW Balanced Input Phono Preamp

The THAT1240 balanced inputs from the remote flat preamp are on the left.
In the middle of the group of connectors is the DC power feed to the preamp.
The THAT1246 Line Inputs are the bottom two connectors.

The Flat gain is adjustable by VR1 and VR2.
John's P10 EQ is in the middle between the relays.
VR3 and VR4 trim the post-EQ level.
RY1-RY4 switch the various monitor and EQ functions.

The THAT1646 balanced outputs are on the right.
Secondary -6 dB unbalanced outputs are also available for RCA or oscilloscope monitoring.
There are no electrolytics in the primary signal path.
The capacitors around the THAT1646 are for OutSmarts and are essentially out-of-circuit for balanced outputs.
The unbalanced outputs pass through 10uF bipolar electrolytics.

J1 bypasses the input 1240 if the flat preamp is located with the EQ board.
J2 adjusts the Phono input level in 3 dB steps.
J3 is an insert at the Phono post-gain trim stage.
J4 is a pre-EQ insert.
J5A/J5B can reverse the RIAA EQ to provide Inverse RIAA EQ for cutting.
J6 is a post-EQ insert.
J7 adjusts the Post-EQ level in 3 dB steps.
J8 is an insert at the RIAA EQ post-gain trim stage.
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by mediatechnology » Sun Aug 30, 2015 12:08 pm

Now that I have a complete system with Flat Preamp and EQ/Monitor Switcher I decided to revisit the OPA2132/OPA2134 FET input dual op amp in the flat front end.

In one of my previous posts I compared the NJM2068 to the OPA2134 and found the '2134 to be about 3 dB noisier with a 1K source resistor.
The NJM2068 is what I've been using for tests and its very, very quiet.
With a real cartridge connected the OPA2134 performs at least as well as the NJM2068.
Though the OPA2134 is noisier with a resistive source, the rising impedance of the cartridge due inductance combined with the orders of magnitude lower noise current yield an almost identical result with RIAA EQ applied.
In Flat mode I also didn't notice much difference between the OPA2134 and the NJM2068 either.
The voltage noise penalty of the FET input OPA2134 is offset by the greatly reduced noise current.

The op amp choices so far are:

NJM2068
OPA2132 OPA2134
NJM2114
NE5532

When I get time I'll see if I can find any LME49720/49860 in my stash that do not have burst noise.

I don't know what the slew rate demands are of a flat preamp - they are far greater than an Eq'd one - but I have to think they OPA's 20V/us SR can't hurt.
Realistically the NJM2068 at 6V/us is probably fast enough but for wideband performance the OPA2134 or NJM2114 would be the best choices.

Oh, and BTW, I can hear fades very deeply below the surface noise so there is definitely an advantage to having a noise/hum/buzz floor below the surface noise level.
At least for records that haven't been walked on at parties...
https://ka-electronics.com

"States Ordered To Fraudulently Inflate COVID-19 Cases 15 Times Actual Rate"
https://banned.video/watch?id=5efab695672706002f367a0a
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by JR. » Sun Aug 30, 2015 1:47 pm

mediatechnology wrote:Now that I have a complete system with Flat Preamp and EQ/Monitor Switcher I decided to revisit the OPA2132/OPA2134 FET input dual op amp in the flat front end.

In one of my previous posts I compared the NJM2068 to the OPA2134 and found the '2134 to be about 3 dB noisier with a 1K source resistor.
The NJM2068 is what I've been using for tests and its very, very quiet.
With a real cartridge connected the OPA2134 performs at least as well as the NJM2068.
Though the OPA2134 is noisier with a resistive source, the rising impedance of the cartridge due inductance combined with the orders of magnitude lower noise current yield an almost identical result with RIAA EQ applied.
In Flat mode I also didn't notice much difference between the OPA2134 and the NJM2068 either.
The voltage noise penalty of the FET input OPA2134 is offset by the greatly reduced noise current.
+1 I gravitated toward JFET inputs for my last two preamp designs, without the rigorous objective analysis you performed.
The op amp choices so far are:

NJM2068
OPA2132 OPA2134
NJM2114
NE5532

When I get time I'll see if I can find any LME49720/49860 in my stash that do not have burst noise.

I don't know what the slew rate demands are of a flat preamp - they are far greater than an Eq'd one - but I have to think they OPA's 20V/us SR can't hurt.
Realistically the NJM2068 at 6V/us is probably fast enough but for wideband performance the OPA2134 or NJM2114 would be the best choices.
I wouldn't over think this. 20kHz is attenuated -20dB wrt 1kHz by RIAA so in theory you might expect +20dB at 20kHz, but the gain at 20 Khz is still nominally +20dB so referred to the input, output clipping at 20kHz is down -20 dB from full scale so near 0dBu (give or take.)

I would like to see a pole at 100-200kHz on the flat path just for general principles but a full power bandwidth is probably only necessary for 20 dB below full scale.

I liked my design with a 75uSec real pole in the first stage so i could literally handle a wide band square wave input, but in reality the edge rates from cutting lathes and vinyl are just not very fast...

Oh, and BTW, I can hear fades very deeply below the surface noise so there is definitely an advantage to having a noise/hum/buzz floor below the surface noise level.
At least for records that haven't been walked on at parties...
Less noise is always better... in the early CDs it was a little disconcerting to not have surface noise.

I resemble that remark.. :lol: The footprints are probably not the worst thing found in my record collection. IIRC the footprints didn't sound as bad as deep scratches from careless handling.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by mediatechnology » Sun Aug 30, 2015 3:09 pm

but in reality the edge rates from cutting lathes and vinyl are just not very fast...
True.
Clicks do.
Though I really wouldn't have thought it the ultrasonic harmonics created by mechanical distortion (mistracking) may not have high edge rates but they sure create a lot of ultrasonic energy.
In the flat preamp wideband output on the scope you can see all kinds of stuff above hearing range.
Particularly after that first speck of dust gets hooked onto the stylus and the second-order goes through the roof.
I honestly think a useful transfer instrument would be a HPF just above 20 kHz.
If the energy in that band starts to rise unexpectedly it might provide an early warning of a dirty stylus.
Keeping that sucker clean is a big challenge. More than I remember.
It's amazing CD-4 worked. My brother had Pioneer receiver with it.

I also tried cross-talk cancellation using the Stereo Width Controller to blend broadband to mono.
One the 1 kHz test bands I could increase the separation from about 20 dB to >30 dB with a slight amount of blend.
This is due to the crosstalk being 180 degrees out of polarity.

On the few cuts I listened to it did image slightly better with the blending giving a little more stable mono.
Stuff in the 10-2 O'clock range seemed a little more defined.
I didn't listen to material with a lot of "space" in it though.
https://ka-electronics.com

"States Ordered To Fraudulently Inflate COVID-19 Cases 15 Times Actual Rate"
https://banned.video/watch?id=5efab695672706002f367a0a
"Plandemic/Doctors In Black" https://proaudiodesignforum.com/content/Plandemic.mp4

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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by JR. » Sun Aug 30, 2015 4:25 pm

mediatechnology wrote:
but in reality the edge rates from cutting lathes and vinyl are just not very fast...
True.
Clicks do.
Though I really wouldn't have thought it the ultrasonic harmonics created by mechanical distortion (mistracking) may not have high edge rates but they sure create a lot of ultrasonic energy.
In the flat preamp wideband output on the scope you can see all kinds of stuff above hearing range.
Particularly after that first speck of dust gets hooked onto the stylus and the second-order goes through the roof.
I honestly think a useful transfer instrument would be a HPF just above 20 kHz.
Yes but for slew rate it is the product of frequency and amplitude so it may still not be that fast for rate of change.

Clicks and scratches are still going though the LPF called a cartridge. MC carts may be wider bandwidth but lower amplitude. I wonder what the rise-time is for typical cart... That is the magic number to exceed.
If the energy in that band starts to rise unexpectedly it might provide an early warning of a dirty stylus.
Keeping that sucker clean is a big challenge. More than I remember.
It's amazing CD-4 worked. My brother had Pioneer receiver with it.

I also tried cross-talk cancellation using the Stereo Width Controller to blend broadband to mono.
One the 1 kHz test bands I could increase the separation from about 20 dB to >30 dB with a slight amount of blend.
This is due to the crosstalk being 180 degrees out of polarity.
That sounds really useful.
On the few cuts I listened to it did image slightly better with the blending giving a little more stable mono.
Stuff in the 10-2 O'clock range seemed a little more defined.
I didn't listen to material with a lot of "space" in it though.
Way to go, improving a technology 20 years after I gave up on it. :lol: :lol:

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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