Stereo Solid state Pultec using Lawo DV972/3 (pic's)

The schematic of the Lawo DV972/3 can be found on the Kubarth website (all hail to Kubi)
I just inserted the EQ part between the input tranny and the cap C1/C2.
The DV972/3 gives 30dB gain so it's more than enough. The input tranny is a 1:66/1 Haufe St 4934/2 (info also on the Kubarth site..).
I increased R7/R8 from 4,7K to 44K or so, and I removed C5/C6 for more bandwidth. I put it together and it works fine but maybe if someone more tegnical than me feels the urge to comment on this approach ....please do.
All switches are Grayhill rotary's wich I got for cheap from evilbay...
Ok, here the pics....













Edit: Running it unbalanced on the inserts (tip-ring sleeve) of a Allen @ Heat Mixwizzard mixer I got some nasty oscilation. It was solved by decreasing R7/R8 from 44K to 35K (maybe less). It was probabely an impedance missmatch or so. On the inserts of a Mackie 1402 VLZ mixer it caused no problems (those inserts where a mod. done by me ......so maybe that explains it )

Looks very good. Well the only thing you need to work on is your frontpanel "design" :green:

Flo

Yeah, I'm waiting for Schaeffer to send it to me. It will look like my previous attempt

http://www.groupdiy.com/index.php?topic=9563&highlight=solid+state+pultec

only different scales....

OOOOH NOOOOO
You did it before me. I´m right now at planning exactly this project.
Well, then let us know how it sounds compared to the other Pultec around.
:thumb:

Clean innerds , nice job !

[quote author="Infernal_Death"]Looks very good. Well the only thing you need to work on is your frontpanel "design" :green:
[/quote]

Yeah, any chance of the .fpd file for that one? :wink: :razz:

I don't have a "tube Pultec" around but all I can say about the sound of the DV972/3 is that it's very clean. There's also zero hum (after some fiddling around with the grounding)
My other solid state Pultec (with Neve BA 283 make up gain) sounds a little more "agressive" or so. A very subtle difference that is.
OTOH, the frequenties of both units differ a little so the comparison is not completely fair.

Sorry to bring this topic up, but I´m just curious because it seems you didn´t use a shield at the inductor... So, no hum there?

[quote author="rafafredd"]... So, no hum there?[/quote]

No Siree! no 0(zero)

I didn't notice this when posted. That's proper DIY, and there's nothing wrong with the front panel. :thumb:

radiance said:

The schematic of the Lawo DV972/3 can be found on the Kubarth website (all hail to Kubi)
I just inserted the EQ part between the input tranny and the cap C1/C2.
The DV972/3 gives 30dB gain so it's more than enough. The input tranny is a 1:66/1 Haufe St 4934/2 (info also on the Kubarth site..).
I increased R7/R8 from 4,7K to 44K or so, and I removed C5/C6 for more bandwidth. I put it together and it works fine but maybe if someone more tegnical than me feels the urge to comment on this approach ....please do.

Click to expand...

Hi !

Must admit I was a bit surprised that the insertion of the passive EQ-section went as well as it seems to have gone, but as always:
if it works it works !

So be sure to ignore the following stuff which you asked for above 
OK, here goes, when looking at this thread as a potential DV972/3-card application (as suggested by Laitue5 in his BM-thread),
a few potential tech-issues that came to mind are:

Is the Haufe input-TX still happy ? It wants to see 3k9, but don't know how critical or wide this range is.
Note though that there have been discussions here about partly relevant/partly worst-worst-case situations in which the load that the GPultec-EQ-section presents can be as low as under 100 Ohms, which might pretty sure out of the nice range for this TX.
It may not matter or may be a potential issue (of some lesser or bigger size).
As a consequence the EQ-section may not be driven with enough muscle (again, it may be perfectly fine, but that needs to be verified then) so expected ranges as advertised on the front panel may differ from the actually obtained.

As said, FWIW, if it makes your music work then it's all fine, but since you asked...


Bye,

Peter

I was thinking about the loading issue, too, when I did my version with MEQ filters. Since the Lawo card has a Zin of 9k it seemed very handy to me not to insert the Filter behind the (stepdown) input tranny but simply put it before the card and add additional line in iron. This way the card behaves as a perfect termination for the recommended 10k which the MEQ filter wants to see at it´s output.

From the [disclaimer]more or less relevant[/disclaimer] technical point of view this sounds a lot better !
Too bad you need an additional TX now though (for now three in total per channel, if I understood it correctly).

I think that -if you want- you could remove the orig. Lawo(Haufe) input trafos, fiddle a bit with the now unbalanced input
of the card to get 9...10k termination again and use the removed TXs somewhere else.

Bye,

  Peter

radiance said:

I put it together and it works fine but maybe if someone more tegnical than me feels the urge to comment on this approach ....please do.

Click to expand...

At the time when I put this together I did not have a clue about loading and what not, BUT I had my doubts.
I think Jens's solution is simple and efective and buying another transformer is no big deal since these Lawo cards can be had for cheap.

But than again..if it works, it works...and it does work. Only slightly less boost as my other solid state Pultec which uses Steffens design.