ilfungo

Re: esoteric audio reserch - EAR 660
« Reply #20 on: November 29, 2017, 05:15:58 AM »
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!
« Last Edit: November 29, 2017, 06:43:32 AM by ilfungo »


ilfungo

Re: esoteric audio reserch - EAR 660
« Reply #21 on: December 07, 2017, 01:04:39 PM »
Hi
mounted new transformer and now the gain staging is the same!!!
But the frequency response is not better :'(
Today I have tried to mount the sowter 8344e to real unit and the frequency response is the same of my unit....
This confirm me that the problem is  output transformer.


The big difference I can see with some misurations are this:


EAR 660 output transformer: resistance of each primary is about 750R - secondary 12.5R
Sowter 8344                        : resistance of each primary  is about 300R/ 250R - scondary 6.6R


There is a way to change something in the tubes area to suite better the new transformer?

Thanks!!!

ilfungo

Re: esoteric audio reserch - EAR 660
« Reply #22 on: December 09, 2017, 12:25:03 PM »
Hi
this is the link to 2 files:
( the song is from a disc and it's a mastered version, just L channel)
no processing
processed : 4 db compression/ position 6
https://drive.google.com/drive/folders/1XEXbtgEg6RJUKs3rq4pMZ4JXN5SnlofD?usp=sharing

Now the unit is 100R teminated and sound good ( I hope it's not a problem for the output stage  ???)

what do you think?

thanks!
« Last Edit: December 09, 2017, 12:29:21 PM by ilfungo »

bluebird

Re: esoteric audio reserch - EAR 660
« Reply #23 on: December 09, 2017, 05:50:01 PM »
In any varimu, tube matching is very important. If your tubes are mismatched you will have problems. If you don't have a way to test the tubes, try just switching them around in different sockets. Maybe you will see better response...or worse.

ilfungo

Re: esoteric audio reserch - EAR 660
« Reply #24 on: December 10, 2017, 04:32:04 PM »
Thanks Blebird!
I will try...

ilfungo

Re: esoteric audio reserch - EAR 660
« Reply #25 on: December 11, 2017, 09:50:52 AM »
Hi Bluebird
with matched tube the situation is much Better!!!
150R terminated.
Now I have only -0.2db at 100HZ -0.6db at 40hz and the rest flat.
I think could be good but I don't understand why I have this attenuation on low frequency...
Suggestions?
THANKS!!!