Presto A-920, preamp/amp

[Conviction]

Hi all,

I recently acquired a Presto A-920 preamp/amp, but am wondering what to do with it. Of course, I could use it - as is - as a microphone preamp, but I am a little unsure of it's potential. The input transformers are top notch - a pair of Presto labeled HA-100X's - but I'm thinking they'd be happier in another circuit. Take a look at the schematic: https://www.dropbox.com/s/h16ktza2fpu5mjf/A920.pdf

What's the (if any) disadvantages by using the (Triad) PP output transformer to create the balanced line output?
I'm trying to figure the schematic out, so correct me if I'm reading it wrong.

All input appreciated.

 

[emrr]

This is likely the first tape machine Sun Studios had, if that helps.  I have one, and I remember it sounding pretty great the last time I tried it.  I'm not sure if they are really HA-100X equivalent, or if that's just good old ebay marketing at it's finest.  We'd need to see inductance comparisons, the custom part # types are often lower inductance than the stock types. 

One like yours did sell on ebay recently in the $2000-3000, if that changes your mind about hacking. 

There's a big list of obvious stuff you might do for permanent preamp conversion, starting with reversing the backwards gender of all the XLR's, and making them balanced rather than unbalanced.  Depends on what you are after, which you'll only know after trying it as-is. 

 

[m.a.x]

Hi all,

I recently acquired a Presto A-920 preamp/amp, but am wondering what to do with it. Of course, I could use it - as is - as a microphone preamp, but I am a little unsure of it's potential. The input transformers are top notch - a pair of Presto labeled HA-100X's - but I'm thinking they'd be happier in another circuit. Take a look at the schematic: Dropbox - Error

What's the (if any) disadvantages by using the (Triad) PP output transformer to create the balanced line output?
I'm trying to figure the schematic out, so correct me if I'm reading it wrong.

All input appreciated.

Hey I know I'm late here but I just acquired one of these units and was wondering if you still had the schematic PDF as the dropbox link is no longer active. Much appreciated in advance!

 

[eskimo]

Hey I know I'm late here but I just acquired one of these units and was wondering if you still had the schematic PDF as the dropbox link is no longer active. Much appreciated in advance!

https://groupdiy.com/threads/presto.58678/

 

[m.a.x]

https://groupdiy.com/threads/presto.58678/

Thank you @eskimo ! I really appreciate you directing me to the appropriate thread. You're a lifesaver!