New Doug Self pre-amp design...

[jshowalter]

Originally Posted by Kindhornman

DouglasSelf,
I am new to the DIY site and this is the first time I have seen one of your postings. I do have two of your books and I am studying them intently. It seems funny to me that so many find a tone control sacrilegious as they do so many other things to overcome this aversion. The room treatments, speaker placements, shelving and sloping of crossover networks to get the sound correct are all forms of tone control to me, just in another domain. I for one still think that there is nothing wrong with a proper tone control. If everything was absolutely perfect in the reproduction chain we would still have different rooms and the effects on frequency response.

Steven

It's worse than that. Those who would never think to use a tone control will willingly take a pristine analog signal, A/D it in a receiver, run it through Audyssey, then D/A it, all to correct for room problems that could (probably) have been corrected for in the analog domain.

[jshowalter]

Originally Posted by Struth

On the other hand, when he says "I have come up with a better method than this but this is not the place to disclose it" he is being over-the-top.

I will attest that this is untrue.

When he says that he can't disclose something, it is either because the circuit in question was designed for a client, or because he hopes to sell it to a client in the future.

As one of his clients, I have been directly involved in both of those cases, thus my assertion.

[hareslade]

Hi, my first post here forgive me if this has been covered already

I'm probably just going to build the main preamp and MC section, my own preamp I built some decades back uses the switches on a stereo jack socket to switch out the MC section for aux inputs, I think a basic unit for home hi-fi could be made much more cheaply.

AS a true DIY-er the power supply is standard and I'd probably make my own version. The complete board set adds up to quite a bit.

I see the main pcb's are double sided, to me thats a shame because they cost arm and a leg to buy, is anyone doing a single sided pcb design? I found DIY double sided was a prob, because you can't through plate holes on the kitchen table. So each through joint has to be soldered both sides, and its not practical with stand-up capacitors and I.C holders..

None of this is a criticism of the design technology, I've been around long enough to know Douglas Self knows his stuff. I just think the system could have been made more flexible in its practical construction, and a strip down version would cost less.

I don't see any easy 'purist' alternative to the expensive cermet 1k pots though.. except my own preamp used standard carbon pots of the old style, I've never noticed any great probs over the years,, but it depends whether you're building audiophile standards, or just a boot and braces version to keep cost minimised.

If anyone could work out the working wattage of the pots it'd be useful.. real life audio power levels are significantly less than when sine wave testing.

Finally, one point of order, I see people pass judgement on the sound quality, I wonder if their system was monitored to check against parasitic oscillations. Yes I know.. circuits are modelled ...but if you get an out of spec I.C or a dry joint on a decoupling capacitor, you can get tiny oscillations at high frequencies, and in my experience those do cause sound degradation. So anyone doing sound tests and passing public opinion should really get it checked on a scope by a techie, that things are as they should be..

But its all exciting and I look forward to the build!

[Ian Finch]

Hi and welcome to the forum
It's funny how we have a preamp in the solid state amplifier forum but here it is!
You probably realize from the early posts and exchanges in the thread that this preamp is intended as a no-compromise showpiece
of just how low distortion could be achieved with standard opamps. That meant using an unusual, low 1k circuit impedance and
uncommon, expensive controls and switchgear, commensurate with the circuit performance. The early versions (the last version was
developed in 1996, IIRC) used more conventional impedances and parts values but you'd never call them simple and inexpensive.
The '96 version's PCB was to full size rack case dimensions.

The publication of this project was sponsored by ELEKTOR magazine and I understand they had a hand in determining at least
the physical format and scope of the design before it was published.

Judging sound quality? I can't see much room for the usual implication there of a little sweet distortion, when absolute lowest
distortion is the design goal. That suggests zero sound quality to me, much as Owdeo discovered at the conclusion of his build.

[rsavas]

The only thing that I see wrong with this pre-amp design is that everything is manual operation. For a purest, then I would have to agree that manual controls can be less intrusive, but as a product for a modern day market, it lacks remote control, thus a very limited market. This whole design, could have all been done on one PCB, I hate manual wiring, if it can be avoided, in a production sense, it adds costs to the mfg process.

So all the power to you, to get up off your a$$ every time, walk over to change the volume/mute when the phone rings. Just because you do not want to use a PGA2320 or similar part, thinking that it will taint the music experience some how = rediculious.

I like a complete solution, this is why I design my own HW. For example, the small cost to add a radio function, i.e. Si4735 or Si4770, costs very little, but completes the design into a more functional unit. Having a big external box, tuner unit, is rediculous extra cost and in the end costs a lot more money. I could go on with functional ehancements, some add extra costs, some are cheap to add, other a bit more, thus they make sense. For Elektor it would have been real easy to add the radio function, since they already offered this radio design previously, "DSP-Radio". Personally I do not understand Elecktor's logic in product requirements specs, what can I say, they offer toys, not well marketed/researched products!! This is my opinion, others can voice there own & defend the product as it is.

FYI, these days a double-sided PCB in small qty is as cost effective as a single sided board, because most of the cost, is NRE costs. If you are talking large volumes then the incremental savings, do make some sense, if you want a lower quality PCB and are a nickel & dime operation.

[hareslade]

HI Ian
What I meant about parasitics was, they are naughty things that happen in the real world, when someone recreates the physical item. The specs for this design are superb, and yes I've had the same experience, build something, find it sounds totally flat, then realise its just missing all the added hiccups one's used to.
rsavas..
Regarding remote control, I'm not aware what they use now commercially, but many the solid state auto volume circuits would destroy the distortion spec for this kit, ..use motorised servo's to rotate the pot spindles.
and i promise not to make my own single sided boards.

[Ian Finch]

Originally Posted by rsavas

.... as a product for a modern day market, it lacks remote control, thus a very limited market. This whole design, could have all been done on one PCB, I hate manual wiring, if it can be avoided, in a production sense, it adds costs to the mfg process....

Absolutely, but you can take it for granted that D. Self wouldn't tender an ultimate performance DIY design like this for commercial manufacture - what would be the point, anyway? Take a look at his Cambridge 840 Azur designs for example. Dated now (2006), but they obviously must have remote controls and typical popular features of the rest of the range to be competitive in the mass market. 'Not a bad system remote control, either.

[rsavas]

but many the solid state auto volume circuits would destroy the distortion spec for this kit,

This statement is open to controversy, so you are implying/saying that a 5532 OPA has less distortion than a PGA2320, that is debatable. Could say that a 5534 is a marginally better performer than a 5532.
As for mechanical pots, driven by motors, well they have their issues as well and certainly are more costly to implement.
Lots of options, what can I say and every one has their advantages & dis-advanatges. Something that the buyer has to rationalize.

The Cambridge design:
Cambridge Audio Azur 840A Features
Patent pending proprietary Class XD technology.
Oversized low flux toroidal transformers
120 watts per channel (8 ohms)
200 watts per channel (4 ohms)

Completely separate pre-amp and power amp toroidal transformers and circuits make the 840A effectively a pre and power amplifier combination in one chassis

8 audio inputs - including 1 with balanced connections

Sophisticated resistor ladder and relay based attenuator for volume/balance control


The 840A features Incognito Ready TM / A-BUSTM Ready outputs, allowing multi-room capability.

Read a review finding fault in the stepping of the level, not gradual as one would find with a regular pot, everyone has an opinion.

Yet no radio/tuner, same issue as the Elektor design!!

[Ian Finch]

I occasionally use a Cambridge 650T with this combination: TESTED: Cambridge Azur 840E Preamplifier and 840W Power Amplifier | The Absolute Sound
'Looks like "tuner" programmed in there at 3 on the 840E pre. display, or were you looking for a Receiver?

[rsavas]

I guess that I was looking at the Integrated Amplifier version.
What I see is that you can change/program the display, as to the source selection, rather than the default "Input 2". Just like it was done in The Elektor "High-End Pre-amp" that was done around 10 years ago, using a PIC & a PGA2311, used Takamatsu relays for source selection. Why Elektor can not integrate all its articles into one unit is another puzzle?
Not much has changed in 10 years except for the introduction of the Si4735/Si4770 1-chip tuners. The ease of using these parts is outstanding, why anyone would not use them in a modern day receiver/integrated amp is puzzling to me!! I am working on the Si4770 design, as we speak, almost ready to hit the fab button, curious to compare the Si4735 to Si4770 performance, lucky enough to get a sample of the mixer/Balun from Toko to complete my BOM.