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John Eppstein

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Posts: 1,150 Member Since:31/05/2015

#84 [url]

Oct 10 15 11:45 PM

zmix wrote:
Thanks for posting that.  Now that I can read it, I am a bit shocked by the use of the SSM2017... that was used in a lot of the cheaper AMEK consoles in the 1890s,
 

1890s?
 Damn, this stuff has been around a lot longer than I thought!

(Sorry, I just got a bit of a giggle out of the typo....)

EDIT: Seriously though, this thread is fascinating. Lots to learn here!

Last Edited By: John Eppstein Oct 11 15 12:15 AM. Edited 1 time.

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Wayne Kirkwood

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Posts: 5 Member Since:10/11/2015

#86 [url]

Nov 10 15 9:36 PM

Phono Transfer System Boards are Available

Hi - I just wanted to let people know that the Phono Transfer System boards Paul have been referring to are now available.

The construction information and circuit description is here: http://www.proaudiodesignforum.com/forum/php/viewtopic.php?f=7&t=753

Bare and assembled boards are available. Paul will be doing custom builds for those not wanting to DIY.

The flat non-EQ'd preamp board at the top has balanced MM inputs and balanced outputs. With transformers it does MC carts. It is designed to be located at the lathe or turntable. The bottom board provides RIAA EQ, monitor switching and simultaneous flat and EQ'd balanced outputs.

I designed this one for myself with the objective of recording flat, de-clicking flat files with analog RIAA EQ for monitoring, and then performing final RIAA in DSP. Dual signal paths permit simultaneous ingest and editing. Good DSP filters were the last piece of the puzzle. I wasn't happy with the FIR filters I in Cool Edit. Diamond Cut DC8 is the DSP-based RIAA EQ that I found to be phase accurate. DC8 sounds like the analog EQ.

For people wanting simple RIAA playback or flat recording the build can be simplified.

The board is also capable of line-level inverse RIAA by jumper configuration for cutting.

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Phono Transfer System with remote flat phono preamp and RIAA EQ monitor switcher.


There is a long thread describing the evolution of this project along with a lot of measurements: http://www.proaudiodesignforum.com/forum/php/viewtopic.php?f=6&t=423

My goal was to make it quiet in the real world and provide as much signal routing and flexibility as possible.

Wayne

Last Edited By: Wayne Kirkwood Nov 10 15 9:40 PM. Edited 1 time.

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waltzingbear

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Posts: 1,203 Member Since:16/07/2012

#87 [url]

Nov 10 15 10:43 PM

for those wanting more info on de-clicking prior to EQ, you should find the old Richard Burwen articles on de-pop and de-clicking. I'm not sure if he did any in the JAES as papers, but he did do a series in Audio on the design and development of the de-clicker he designed. Not sure what the dates were, but I think one of the sites has Audio up now. (I'm thinking late 70's or early 80's)

Cheers
Alan

Alan Garren
Waltzing Bear Audio

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gold

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Posts: 1,468 Member Since:27/01/2011

#88 [url]

Nov 11 15 1:09 AM

It's the best playback I've ever gotten. It's dead quiet. I have two front ends built. One has Lundahl 1676 transformers at 1:16 for a Denon DL103. The other one is for MM carts with no transformers. I have a variety of MM carts and just got a pile of boards so I can dedicate a front end per cartridge. That way a changeover happens very quickly. Change the headshell and pop in the crresponding calibrated front end box and it's good to go. I have another set of transfprmers for the Ortofon SPU.

The Denon 103 is scary quiet. It's a 'medium level' MC cart. The CMRR of the transformer and the CMRR of the instrumentatation amp combined with the relatively high output level make it scary quiet. The MM carts I've tried are also very quiet. Much quieter than anything else I've tried or heard. I liked the DL103 before and I still like it. I can't decide whether to underdamp the cart. It sounds less constrained that way but it gets brighter. The stock termination value gives the flattest frequency response but sounds a little choked. 

It's hard to get quiet playback from the tonearm on a Neumann lathe. The ground bus is polluted with switching noise and the cable run to electronics is long. I built mine so that it's nearly impossible to have any hum or buzz problems. Just hiss and not much of it. It would also work on a stage with bad grounding and heinous dimmer noise.

I've always thought discussions about how quiet phono pre's are have an Alice in Wonderland quality. I spent years trying to get clean quiet playback from preamps with great specs. I thought it was me for a long time. The problem is the unbalanced interface. It doesn't matter how quiet the pre is. Unless you are in an RF/EMI free zone you will have problems. It doesn't matter haow many unobtainable Japanese transistors are there. 

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Wayne Kirkwood

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Posts: 5 Member Since:10/11/2015

#89 [url]

Nov 11 15 5:34 PM

I posted this originally at the Pro Audio Design Forum of a click I captured in the wild.
The RIAA de-emphasis was done in Cool Edit and is FIR so it may not be representative of phase-accurate RIAA implementations using analog EQ or IIR RIAA.

This particular example is a rather large click having a typical strong Side L-R vertical component.
I didn't have to look hard for this needle in the haystack: It was the first big click in the file.

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Anatomy of A Phono Click, No RIAA, Flat Transfer. Note strong L-R (Side, Vertical) Component.

This is the same click after RIAA EQ:
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Anatomy of A Phono Click, With RIAA Equalization (FFT).

Note the time-smearing and increased difficulty of detecting the click if RIAA EQ had been used during recording.
And it's primarily a Side, L-R, vertical event.
This click would have been almost at right angles to the mono line when viewed in Vectorscope X-Y mode.

I don't know if all click auto-detection methods are friendly to flat files but the Virtos DirectX plugin used with CE seems to be.
I haven't done a lot of work yet with DC8 to know.

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waltzingbear

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Posts: 1,203 Member Since:16/07/2012

#90 [url]

Nov 11 15 5:54 PM

Although its hard to tell on screen shots, I'm not sure what you mean in this case by time smearing. I see the effects of EQ on the signals, not sure I see anything else. Please elucidate.

Thanks
Alan

Alan Garren
Waltzing Bear Audio

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Wayne Kirkwood

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Posts: 5 Member Since:10/11/2015

#91 [url]

Nov 12 15 9:20 AM

I mis-spoke. What you're seeing in the lower shot are just the effects of CE's linear phase FIR RIAA EQ.

"Time smearing" in that example would be more accurately described as reduced dV/dt due to the integration of the RIAA curve. The working theory is that many de-clickers work better with high dV/dt flat chains. I haven't tested enough to know.

The time-smearing comment came about from a related discussion (proaudiodesignforum) on the impulse response of multi-order warp and rumble HP filters.

I should grab some screen shots of analog EQ including HP filtering to see what they show. Maybe I can find that same click.

Last Edited By: Wayne Kirkwood Nov 12 15 11:36 AM. Edited 3 times.

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gr

Gold Finger

Posts: 350 Member Since:21/02/2011

#92 [url]

Nov 12 15 11:07 PM

Sonic Solutions No Noise used to have a flat click detection option (maybe still does) but I assumed modern systems built that in to their detection systems making flat transfers unnecessary. Is that not the case?

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Wayne Kirkwood

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Posts: 5 Member Since:10/11/2015

#93 [url]

Nov 13 15 10:39 AM

I think it depends. http://www.iasa-web.org/tc04/audio-preservation

5.2.6.10 There is some debate as to whether noise reduction tools for the removal of audible clicks, hiss etc are more effective when used before an equalisation curve is applied rather than afterwards. The answer very likely varies according to the specific choice of tool and the nature of the job to which it is applied, and in any event will be subject to change as tools continue to evolve. The most important point in this regard is that noise reduction equipment, even fully automated tools with no user-definable parameters, ultimately employs subjective and irreversible processes, and so should not be used in the creation of archival master files.

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gold

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Posts: 1,468 Member Since:27/01/2011

#95 [url]

Jan 13 16 7:24 PM

I'm not sure how many are checking in on the Phono Transfer System threads over at Wayne's. I've been using one as lathe playback for over a month now. I think it's stunning but I'm biased. I brought one over to Josh Bonati's last weekend. We set it up in a matter of minutes. It was about 15dB quieter than the phono pre in the SAL74.

I have come up with a way of building them that I think will be most useful for mastering folk. The demo isn't built that way but I can flip the face plate over and relabel. There will be two phono inputs and two line outputs. Output 1 will be switchable between Phono 1 and Phono 2. Output 2 will be Phono 2 only. Output 2 can switch the RIAA EQ In or Out. You could even use a favorite phono pre and feed it into a base station In.

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