Anyone built/listened to D Selfs precision preamp. - diyAudio
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Old 8th December 2009, 07:47 AM   #1
Mooly is online now Mooly  United Kingdom
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Default Anyone built/listened to D Selfs precision preamp.

Wondered if anyone had built and or listened to Doug Selfs precision preamp published in August and September 1996 in Electronics World ?

The Signal Transfer Company: Precision Preamplifier

Dougs tone controls with adjustable turnover frequencies look interesting.
The whole design uses NE5532's and does have a fair few electroylitics in the audio path, mainly to keep any offset current out of the pot wiper as it uses NE5532's. Using FET opamps looks a possibilty and would enable these to be ommited.

Anyone any experience of the design in practice
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Old 30th December 2009, 11:07 AM   #2
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Update on this... I prototyped the design and have to say I am very impressed. It's far more useful than "conventional" tone controls due to having continuosly adjustable turnover frequencies and a "return to zero" curve... meaning that it doesn't boost frequencies outside the audio range.

If I ever incorporated the design into a future amp build I would definitely look to using FET opamps and eliminating the electrolytics... but even so... built as published with NE5532's it's excellent.
The only FET opamps I had available (needing 7 of them) were TL072 which often sound better than 5532's particularly as a quick swap in a CD player I/V convertor and filter, but not here... the 5532's are pretty faultless to me
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File Type: jpg print.JPG (90.7 KB, 1536 views)
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Old 30th December 2009, 12:23 PM   #3
Nrik is offline Nrik  Denmark
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Hi Mooly.
Congrats with your D.Self EQ.

Before you get attacked by the "tone-control-is-bad-for-you"-people, I just wanna join your side; Tone Control is good - and often needed!

And especially in these MP3/download times, I think the equaliser really should have a comeback.

As Mark Levinson himself said: "We never said one could do witout tone controls, there just wasn't any that sounded good!" ...wich is double impressive since he practically invented the 'purist' approach wich sported everybody to leave out tonecontrols.

...some music becomes so much more enjoyable with the correct dose of EQ, and that is what it is all about. Try these:
Donald Fagan - the nightfly (add bass - no more 'thin' sounding, but really groovy)
Pink Floyd - Animals (add some in the highest treble - no more muffled sounding, but open and dynamic)


I chose to clone the Audio Palette equalizer instead, and I am as happy as can be.
I am not gonna spoil your happiness, but my Audio Palette clone features:
- Only six controls = intuitive operation
- Well chosen frequencies = attacks the right places
- Range that fits each band = feels 'just right' on all controls.
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Old 30th December 2009, 12:37 PM   #4
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Thanks for your support

I've sat on both sides of the fence when it comes to eq and tone controls... so thought it about time to experiment a little.
I agree with you, some recordings do seem to benefit from a little correction in the right places... and doing it "right" is vitally important.
This tone control stage doesn't wildly accentuate or attenuate in an all or nothing way as most seem to do... it's far far more subtle than that, and makes a real difference truth be told.
I am sure you find yours is similar too.

I would seriously consider adding this to a future complete amp project... it's that good.
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Old 30th December 2009, 12:41 PM   #5
Nrik is offline Nrik  Denmark
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Quote:
Originally Posted by Mooly View Post
I would seriously consider adding this to a future complete amp project... it's that good.
You should!
I am in the process of doing exactly that.
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Old 31st December 2009, 09:06 AM   #6
barry4 is offline barry4  United Kingdom
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I built one using the PCB that was (still is?) available. It sounds very good and is very quiet. After 12 years, the input selector switches are starting to stick and crackle, and I don't like the box I used. Will probably re-box it and replace the input selectors with a relay board.

Barry
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Old 31st December 2009, 11:17 AM   #7
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First post, so greetings all. I have been lurking in the background reading and following this good forum.


Quote:
Originally Posted by barry4 View Post
I built one using the PCB that was (still is?) available. It sounds very good and is very quiet. After 12 years, the input selector switches are starting to stick and crackle, and I don't like the box I used. Will probably re-box it and replace the input selectors with a relay board.

Barry
Hi Barry4,

The original PCB is no longer available - there is a new version with some additions to it such as headphones amp.

The original switch bank parts became a real hassle to source. A custom switch bank is available as a stock-item for the new Precision Preamp. It is NOT compatible with the original PCB.

There may be one or two (literally!) of the original switch banks, or possibly the parts for 1 or 2 switch banks, if you decide to re-switch your Precision Preamp - let me know. Your idea to replace the input selector switches with relays is OK and great for remote control, but please be aware that the switches & their contacts have been laid-out on the PCB in a way that is designed to reduce cross-talk. Note that the circuit schematic shows 2 switch contacts in series - this is to increase physical separation of non-selected active signals from the selected signal. Doing the same thing with relays is recommended.

Hope this helps.

Gareth.
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Old 31st December 2009, 08:16 PM   #8
Pingrs is offline Pingrs  United Kingdom
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Default Self '96 Pre-amp.

Some may be wondering what the tone control stage actually does in Self's pre-amp. Attached is the measured curves from my build on my own DIY pcb design, 8 yrs ago. Similar to the original in layout, but not in tracking.
It provides the normal boost/cut but with variable turnover frequency.
Snag now is crackly pots. Mooly, where did you get yours. Are they conductive plastic?

Brian.
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File Type: doc '96 Pre Amp Freq response.doc (39.5 KB, 287 views)
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Old 1st January 2010, 06:26 AM   #9
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Brian, the pots (along with everything else mostly) were from here,
OMEG|PC2G16ECO10KA|POT, DUAL GANG, LIN, 10K | CPC
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Old 1st January 2010, 07:04 AM   #10
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Hi Garreth... you are too modest I believe you were the designer of the original PCB's in question.

Found this on Google showing and detailing the design, starting on page 70 for those that haven't seen the tone control part of the circuit.

Self on Audio - Google Books

Must admit I prefer switching using discrete FET's in a series shunt arrangement... partly for the fact that the performance is consistent over time, and also to use with remote control. And the isolation is better too.

Last edited by Mooly; 1st January 2010 at 07:16 AM.
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