Need a Discrete Transistor preamp stage (for summing amp)

[ioaudio]

as this is my first post i´ve to say that i´m happy finding this place finally.
feels a bit like home

my english is not the best, i am from austria, but i hope i will get into it after some posts. if you feel like correcting me, please do it :grin:

this is the place of my first post because the studiomaster 16 16 2 (which i recently grabbed from the garbage dump) brought me here via google.

the search took me a while, but now i direktly could find the one who designed this mixer,
i´m really overwhelmed !

i just fixed fuses in the supply, conncted, and it seems to work. lucky me!
pots are quite sticky, some of them seem to be rusty ( i opened the mixer, lots of dirt in the inside)

i´m still not shure what way i want to use this desk. when i saw it in the garbage, i thougt i might use the mic pre´s only, stuff them into a compact case for mobile recording. thats what i would need it for.
so i start thinking about modding it,
any suggestions?

thanks in advance.

 

[Eric Best]

Hey, I still have a P7!!!!!!!!!

I had good use over the years. Now it just sits though.

Do you know where I could find a schematic to see what is going on in there?

 

[ioaudio]

this one hase been pasted in another thread.




http://mysite.wanadoo-members.co.uk/studiomaster/

 

[Eric Best]

I can't find the P7 in that list though.

 

[Eric Best]

I also didn't realise that this was a ressurected thread. I'll let it die again.

 

[gar381]

AP

Just noticed that the mic-pre in the R6a looks like an earlyer version
of the mic-pre that Tangent of Phoenix AZ. used in their xx02a bar boards In the late 70's.
Change the 2sa970's to pn4355's and the 4560 to a tl071.
Change a few other part values and you got a tangent. Those mic
pres sounded damn good for a desk that people poured beer in... (including ME!!) You were a pioneer. Hats off!!

GARY

 

[northsiderap]

Here is a gain block I sketched out for this concept.

You could use an emitter follower on the output for transformerless output at 600z or less. Ive heard of a medium-impedance amp using both the emitter and collector as a push-pull, which would technically make it balanced. Anyone know of any phase problems doing this?

Probably not the quietest thing in the world, but it is the coveted Class A. Has anyone made the feedback capacitors high-pass filters to feedback 50k and above to prevent RF oscillation?

As for input... You can work it out to @6000z input impedance with 18v I think... I had it at 24v and started the first voltage divider at @12k

The box on the far left is your simulated line input, and the resistor on the far right simulates the next stage in your audio chain. You'll notice that there's two halves of the same thing seperated by a capacitor. You can use only one half, depending on how much gain you need. How much gain DO you need?

I was thinking about a 1:4 input transformer for a mic input when I designed it... Maybe with a resistor ladder or a buffering opamp you could get the right input impedance for a summing amp...

Someone has used this kind of design before right? Let me know how yours turned out...

 

[anna loog]

V275 Schematic

Try this one...