madswitcher
Well-known member
Hi folks,
I have just been playing around with the op transformer from a Studer A80 - I found a line card from somewhere and decided to see how it performed. The line card has a 30dB or so of gain - a bit too much for what I wanted - and I wanted to look at the transformed in particular and see how it performed with my newly built Gar2520s.
Having taken the op tranny off, I strapped it up to the output of a 2520 DOA set for unity gain, gave it a 2200uF op cap and gave it a frequency sweep. The transformer has an 8dB voltage step up.
At 0dBu out it gave a remarkable range of 15Hz well up to 240KHz into a 10Kohm load - this is -1dB down at these frequencies.!!! Phase shift at 20Hz wasn't too bad either - about 10 to 15 degrees or so (judging by my scope trace). There was a bit of a kick at about 10Hz, but a 12 Ohm damping resistor between it and the 2520 solved that one.
Turning the input up, it gave a reasonable op of about +30dBu at 1 KHz into a 10K load before the 2520 started to clip (I was running that on 17 volt rails). Loading with a 1K load brought the max output down to about +24'ish dBu
The bottom end started to saturate the core at +20 at 20Hz or so, but still a reasonable performance.
Putting some Pink Floyd through them - nice and deep, and clear as a bell.
So if you get the chance to pick up any of these cheap - well worth the play.
Happy listening
Mike
I have just been playing around with the op transformer from a Studer A80 - I found a line card from somewhere and decided to see how it performed. The line card has a 30dB or so of gain - a bit too much for what I wanted - and I wanted to look at the transformed in particular and see how it performed with my newly built Gar2520s.
Having taken the op tranny off, I strapped it up to the output of a 2520 DOA set for unity gain, gave it a 2200uF op cap and gave it a frequency sweep. The transformer has an 8dB voltage step up.
At 0dBu out it gave a remarkable range of 15Hz well up to 240KHz into a 10Kohm load - this is -1dB down at these frequencies.!!! Phase shift at 20Hz wasn't too bad either - about 10 to 15 degrees or so (judging by my scope trace). There was a bit of a kick at about 10Hz, but a 12 Ohm damping resistor between it and the 2520 solved that one.
Turning the input up, it gave a reasonable op of about +30dBu at 1 KHz into a 10K load before the 2520 started to clip (I was running that on 17 volt rails). Loading with a 1K load brought the max output down to about +24'ish dBu
The bottom end started to saturate the core at +20 at 20Hz or so, but still a reasonable performance.
Putting some Pink Floyd through them - nice and deep, and clear as a bell.
So if you get the chance to pick up any of these cheap - well worth the play.
Happy listening
Mike
