MAT02, 03 Elektor preamp schematic

[Samuel Jayaraj]

As far as I can remember, this Elektor preamp has an output impedance of 1 ohm, it that helps.

 

[stv]

output impedance of 1 ohm

Without the 47 ohm output resistor, i guess?

 

[lineup]

@lineup do you know anything to the above question🙂

I'm thinking a 20Kohm volume pot and a decent regulated power supply. Any thoughts🙂

20 or 25 kOhm will be fine.
20VA transformer will also do well. With regulated voltage.

 

[hcpower]

Thanks🙂

 

[hcpower]

I've got good results with the THAT340. Just changed the 50k offset pot to 10k. More then enough to zero out the DC.
The 340 I've got for test do 130Hfe at the NPN and 69Hfe at the PNP

 

[Nisbeth]

@hcpower is there a PCB layout for this design that you are using or?

 

[hcpower]

@Nisbeth I've just drew a proto PCB and ordered for testing. I've got four in spare, if you want one we can arrange it.
I skipped the BC327/337 outputs as I'm still waiting for these from mouser, TTA/TTC004 are used as outputs instead

Regards

 

[hcpower]

I'm working on a final layout. Something like this for a stereo preamplifier drawn to fit a perfectly in a modushop chassis

 

[Nisbeth]

Interesting. Not something I'd want to start on right now, but definitely interested in following your progress 🙂

 

[hcpower]

No problem🙂 There's still a long way, and just throwing in some ideas for a final layout 🙂.
I want to test BC550/560 instead of THAT340 also, a breadboard test showed that a 2.2Meg would settle the offset with the BC's if Hfe were around 550's still with the NPN as the better of the two.
The servo option will be tested as well before deciding.

Regards

 

[Drbulj]

Hi,
Didn't read this tread in details but I see it is about old matched pairs. If someone needs I have this original book from PMI that was originally making them before Precision Monolithic Inc were sold. If you need any page from it i will scan for you there are many pages on MAT and SSM matched pairs.

 

[hcpower]

I've spend all evening last night trying to find some curve traces on the THAT-corp just to compare to the BCxxx, but there's nothing to be found online. Only the datasheet from factory. That said, I've decided to go with the THAT340.
DC-offset is more stable then with the BC550C/560C.

I'll do the preamp with the TTA/TTC004. Even at 40mA across each emitter, the TT's stay cool and DC-offset remains calm.
I do find the preamp to take quite some time to find the Null-Point at power up, so I'm leaning towards the servo-version.
The picture is with the THAT340 diff and TTA/TTC outputs at 10kHz

I'll start a new thread on subject if I managed to continue the build🙂

Regards

 

[inyashd]

Yes,Interested to built THAT340 diff ,version start new thread.

 

[Jok3r7]

Old thread, but seams like a good place to aske about this preamp.

I've had my eyes set for building this preamp for quite some time now.
It's hard to find any further information besides from this thread. And very helpful reading. I don't have MAT02/03, but loads of BC550C/560C or KSA992F/KSC1845F if these will do if properly matched.
As for the BF256C I have purchased Onsemi J111 as replacement.

But two questions:
-The volumepot, how many Kohms should I use for this preamp?
-For the PSU I'm thinking of a 20VA or so regulated power supply with 2x6800uf. What did Elektor recommend as PSU for this preamp?

Thanks🙂
View attachment 1303438
Best regards

Hello HCPOWER, the schematic is too blurry and I can't see the value of the components clearly. Do you have a clear schematic? Thank you

 

[hcpower]

I just followed the schematic on page1/#4 https://www.diyaudio.com/community/threads/mat02-03-elektor-preamp-schematic.41993/post-488877
I build both the servo version and non-servo, and settled with a servo.
I've tried 1845F/992F but didn't get it to work properly. BC549/559 or 550/560 will get you going.
The tricky part is to set the offset if MAT02/03 is not used. I'll leave this to the builders for now, but I got it working with THAT340 primarily by increasing R29.

Best regards

 

[carlmart]

If you need any more questions answered, i built the preamp.

I did the discrete versions with Mat02, Mat03.
And the full scale preamp with MC/MD version,
with MAT02/MAT03/OP27/OPA627 with relay switches.
Later i tossed out the voltage regulation and stepped up to batteryfed.

What did you find in the audio quality compared to other designs?

 

[hcpower]

I've finished my build some time ago but forgot to share on DIYA besides from a simple question regarding R-core transformers, so here's a picture of my version. Vastly overkill PSU, but had a lot of fun while building this unit.
I didn't stick completely to the original schematic besides from the overall topology hasn't changed, and the two 10Kohm/150pf has been removed as they weren't needed with the TTA/TTC004 outputs I selected to use.
It sounds excellent and I see no problem recommend others building this "old" 1993 Elektor preamp as posted on page 1, even with BC549/559 as diff if matched properly.
The magazine talks alot about matching diodes and transistors, and it's a must.. Only thing that's not mentioned is the BF256C.
After finishing this build I ended up matching two BF256C, one for each channel to keep the currents source delivering the same mA between the two channels and performing equally. I would recommend this also.
Best regards

3D render...
and the finished preamp