Elektor's Preamplifier 2012 in 2023

Good morning

I am building a clone of the SUGDEN A21 amp (class A) and want to associate a very good preamp with RIAA, tone control.
That of ELEKTOR 2012 caught my attention. To validate the quality of the PCBs manufactured by JLCPCB, I ordered the tone corrector part from them. Superb quality.

Now that I am sure I can have PCBs, I would like to have feedback from those built or use/used the Elekto Preamp 2012 or want to go in the same adventure than me!
So any feedback from this preampli would be appreciated, going to build it alone with no support is a bit hard.

Please let me/us know

Georges
 

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Hi Georges,
I built the Elector 2012, ten years ago and still going strong. Performance is excellent. Very low noise.
The documentation is excellent and the recommended parts were easy to find. I used NatSemi LM4562 all round for the dual op amps because I like them. The boards are well laid-out and component ID markings were clear. All making assembly quite straight forward.
Do not use the standard 317/337 voltage regulators in the +/- 17Vdc power supply - they are noisy and slow. LinearTech make very good 3 pin adjustables (eg LT1085 for +ve).
I am happy to assist if needed.
John
 
@Gvida - I'll 2nd what Johno said above. I built mine about 10 yrs ago as well. The 3 Part Elektor article was well written and easy to follow. Up to that point, this was an advanced project for me, but I always enjoy a challenge. When I fired it up nothing but silence. A little trouble-shooting led me to a reversed opamp. Once inserted correctly, it started singing beautifully! :) You can't go wrong with this preamp.
 
Some pointers regarding the BOM:

1. The Potentiometers are like 30 bucks each, but at least available. So be aware you will be spending like 120€ on potentiometers alone.

2. The specified BJTs (2SA1085) for the MC input stage are long EOL. ZTX951 are available but have a different pinout. However a forum member is selling NOS 2SB737 (which are also mentioned in the article and even preferred to the 1085s) here.

3. You might have some trouble sourcing all the capacitors specified as polystyrene, so be prepared for that. LCR in the UK still makes them, I know HifiCollective from the UK stock them (fairly expensive "audiophile" store from my impression). Apart from that it's a bit hard to get LCR caps as a consumer (Farnell stocks many values but only sell to customers with VAT numbers). Mouser also stocks some Polystyrenes made by Xicon, but not all the specified values. Ebay is full of polystyrene caps from various sources, including what claim to be NOS Philips. Make of that what you will.

4. LM4562 have become a bit controversial or whatever you want to call it, with reports of noise issues (popcorn noise) and higher sensitivity to EMI than other OpAmps commonly used in audio applications. My plan was to test every single LM4562 for excess noise myself (since TI seemingly doesn't), but still use them despite the EMI aspect. Sure, one could improve over LM4562 with newer SMD parts on adapters, but at least for the initial evaluation I will keep it as close to specified as possible.

Overall, I have been soldering on this project on/off for about 4 years now I think, just recently got some of the 2SB737s and the remaining polystyrene caps. Still have to buy the pots and want to replace some components I soldered years back which were of questionable quality (resistors and diodes from AliExpress kits). Considering the total BOM cost its really not worth leaving them in there. And yes, the total BOM cost is substantial at least by my standards. But I hope to get it done this year with enclosure and everything. I don't know if anybody has ever uploaded design files for a front and rear panel, but JLCPCB offers reasonably priced Aluminium PCBs now which make pretty decent front and rear panels. If we could agree on an enclosure, maybe we can cooperate on that part.
 
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@kn0ppers
2-For the BJTs I have time to find equivalent as my vinyle table is MM. The MC part will be done later.
3-Is there any equivalent, i mean polypropylene, ceramic ... ? Mouser has Polystirene but 150pf not 100, a shame.
5-I will definitively by part from mousers and other wellknown provider, and avoid any chines parts.
Yes JLCPCB looks to deliver good job. regarding front and rear, this is a good ide to see if possible to do something.
==> from my side I will use this box (in black) Box
because this is the same width as my amplifier.
I also studying to use a motorized pot for volume, so for that its position could be slightly shifted to the right.

@jono you said you only use LM4562, any issues like kn0ppers relates ?

Please to continue to progress.

Georges
 
You will need to use a low profile heatsink and capacitors in the power supply to use that case with 40mm height.

Regarding the capacitors you can also use WIMA polypropylene like FKP2 or NP0/C0G ceramics I guess. But I think you should be able to find at least the 100pF polystyrene caps somewhere, as 100pF is quite a common value.
 
Georges,
Capacitor type is less important than its value - but avoid cheaper polyester or ceramics. The best capacitor types are stable over the temperature, voltage and frequency ranges and that means film/foil types. I used polyprop because I was still working back then and could afford it. But I also selected each cap and resistor for the tightest value match - the RIAA equalisation accuracy depends on this.
I only populated for MM so cannot comment.
My 4562 were older Nat Semi originals from before TI took over. The newer surface mount types from LT are very good but they do not have the output drive current capability of the 4250 which this circuit requires (very low output impedance design needs higher and more accurate current drive capability) I do not have any hints of noise, hiss nor pop. You should use sockets for all the op amps - and only buy gold plated for long oxidisation free life.

Cheers
 
There is quite a difference between various types of ceramic capacitors. NP0 ceramic capacitors, also known as C0G ceramic capacitors, are about as linear and as stable over temperature as it gets, and you can get them in 2 % or 1 % tolerance, although 5 % is more common. Still, polypropylene capacitors are the closest substitute for polystyrene capacitors.

I don't know this specific preamplifier, but many moving-magnet preamplifiers published in Elektor are not noise-optimized well. They tend to design for minimum noise voltage while overlooking that there is also noise current. If they use JFETs for the moving-magnet input, or bipolar transistors biased at a low current (typically 25 to 100 uA), then it was noise-optimized well.
 
Georges,
Capacitor type is less important than its value - but avoid cheaper polyester or ceramics. The best capacitor types are stable over the temperature, voltage and frequency ranges and that means film/foil types. I used polyprop because I was still working back then and could afford it. But I also selected each cap and resistor for the tightest value match - the RIAA equalisation accuracy depends on this.
I only populated for MM so cannot comment.
My 4562 were older Nat Semi originals from before TI took over. The newer surface mount types from LT are very good but they do not have the output drive current capability of the 4250 which this circuit requires (very low output impedance design needs higher and more accurate current drive capability) I do not have any hints of noise, hiss nor pop. You should use sockets for all the op amps - and only buy gold plated for long oxidisation free life.

Cheers
@Johno Thank you very much for your feedback.
I will use the combination of NE5532 and LM4562 as designed by Doug self first, then make a test with one chanel full 4562.
 
I've downloaded the Gerber files, might start working on this project :scratch2:
Now following thread.
When you order PCB to JLCPCB the minimal qty is = 5. I ordered the Main PCB to see how job's done. It looks perfect. So I have 2 more I can resel if that interrest someone. Same thing for the rest of PCBs, I planned to make the order to JLCPCB on september, keep 3 to me and resell the 2 others at cost price +shipping costs. Lets discuss if any are interrested, just to help.

Georges
 
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When you order PCB to JLCPCB the minimal qty is = 5. I ordered the Main PCB to see how job's done. It looks perfect. So I have 2 more I can resel if that interrest someone. Same thing for the rest of PCBs, I planned to make the order to JLCPCB on september, keep 3 to me and resell the 2 others at cost price +shipping costs. Lets discuss if any are interrested, just to help.
I'm interested, PM sent.
 
I'm doing good progress with this project. Only a few parts are missing butthey're on their way. Elektor's articles quality is outsanding.

Still have to complete phono preamp board and source a suitable chassis.
 

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