esoteric audio reserch - EAR 660

Hi
I'm searching EAR 660 schematics...
can someone help me?
Thanks!

here

THANKS!!!
Any info about  in -out- sc transformer?
thanks!!!

???

It's 85% of a Fairchild 660. I would assume the same transformers.

Thanks PRR
do you think also  the interstage transformer?
Thanks!

ilfungo said:

Any info about  in -out- sc transformer?

Click to expand...

identical transformers for signal input/output.

gridcurrent said:

identical transformers for signal input/output.

Click to expand...

could be
input 600:10k
output 10k:600 ( gapped?)
interstage?

The signal path transformers will be very similar to Fairchild.

The sidechain rectifier is likely a 10r:1K at 10-20 Watts. It is possible a 16r:8K 25W will work with trimming.

Thanks PRR!!!
some suggestion for 10r:1k ?
there is something similar in commerce?
Thanks!

can someone help me?
Thanks!!!

Nobody knows much about this unit. You are a pioneer.

Hi PRR!!!
The unit power on and sound!!!
I'm using a sowter 3575 as input
Custom Sowter interstage output
Sowter 9900 as output.

only 2 dubts:

the 2k5 input pot on input transformer need to be changed for the new transformer?
The original would be 600:10K the new one is 10K:10K

The 9900 output transformer have 2 secondaries, do I need connect them in series or parallel?
the original transformer from the schematics seem to use only one.

THANKS!!!

> the 2k5 input pot on input transformer need to be changed for the new transformer?

Why?

> output transformer have 2 secondaries, do I need connect them in series or parallel?
> the original transformer from the schematics seem to use only one.

No clue. Only difference would be output level.

Thanks!

Hi
I've make some measurement
SOWTER 9900 on output:
With 220R the response is nearly flat but there is a big level loss.
No termination is very weird frequency response, but much more level.
There is a way to have the same frequency response without this big loss?
Thanks!

220 R terminated.

???
new test:
also with termination ( 220R) i have a constant roll off from 20k to 20 hz of 2 db.
Could be a impedance problem ?
I've used Sowter 9900 ( 10K:600)
The original Fairchild 660 transformer are 600:60k an 60K:600.
Could this affect the frequency response?
Thanks!!!

> Could this affect the frequency response?

Yes.

Why are you testing with 200 and infinity?? You -say- the design load is 600. Have you tried that?

Yes I've tried with different termination
This is the frequency response with 600R termination.
In this circuit the better result I can have is with 220R termination.
Now I want to try with Sowter Fairchild transformers...
Thanks!