calling NY-Dave

Hi Dave,

I build a few boxes according to your schematic :sam: found here
( http://www.ionrecords.com/tapeop/ampinterface.jpg ) :thumb:
and made a modification that should work to my opinion.

I used a trannie from edcor (10K:600 with centertap on the secundary) connecting the 200 ohm resistor on the sec+ and this CT, following advise i got from this forum

Since i find it a good idea to be able to connect two amps in parallel i made the whole thing from the secundary to the amp output double, thus connecting the second one on the CT (using as +) and the - of the secundary of the trannie. I noticed i cannot use the volume and the impedancecontrol seems to work more efficient then on my other units i made. All connections have been checked a few times and seem to be as i discribe and in respect to your schematic. All other units work perfect

I also brought in a 2nd groundlift on the second chain since it's possible to create groundloops when connecting amps in parallel.

Do you have any idea what might go wrong?
Or do i maybe have a damaged trannie here?

btw R1 is 220 ohm VR2 is 47K but that shouln't give any concern i assume

If I understand your description correctly, it sounds like you "stacked" the two outputs, which means the level control on the upper output can never go to zero, hence its ineffectiveness.

If you must have two outputs from one box, using only the one transformer, a better way would be to simply duplicate the circuit in parallel after the transformer and the 200-ohm shunt resistor. The load on the secondary of the transformer will drop to about 142 ohms, which is still close enough to 150 ohms. This won't give you galvanic isolation between the amps; for that, you'll need a transformer with split secondary windings, two transformers, or simply build two of the circuits and connect the inputs in parallel. (This will give you a 5K input impedance, which is still plenty high enough for just about any pro gear to drive).

Thank you Dave for your reply.
I must have been not clear enough in my previous post.
I have used a transformer with centertap (splitting the secondary).

a better way would be to simply duplicate the circuit in parallel after the transformer and the 200-ohm shunt resistor

Click to expand...

this is exactly what i did...

Dave,

do you want me to post a picture of this?