API 312, with no high end

The API 312s I put together are working but with little High end.
I figure it is either the lack of the some parts(mentioned below), or an impedance problem. I have not yet begun to debug the problem and will get into it again until next week, but thought I might ask where some of you would start with such a problem.

I am using the schematic from Waltzing Bear

http://www.waltzingbear.com/Schematics/API/API_312.htm

I am using Lundahl 1:10 transformers. As the Lundahl data sheet said the transformers did not need to be terminated, I did not use C6 and 7 (1000pf tying the transformer inputs to ground), and probably did not use R4 or C5 either (220pf and 5.1k tying the outputs of the transformer to each other).


Thanks for all the information that got me this far.

Make sure the 120pF feedback cap is actually 120pF. 1200pF (for eg) would roll off quite a bit of the top end.

Peter

...and 120nF would be a muffled mess!

Keith

Thanks, I'll take another look!