esoteric audio reserch - EAR 660

[ilfungo]

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]

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!

 

[bluebird]

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]

Thanks Blebird!
I will try...

 

[ilfungo]

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!!!

 

[ilfungo]

NEWS!!!!
Work and sound great!!!
sorry for a crappy images...

 

[ilfungo]

Front

 

[ilfungo]

Thanks to all for great help!!!
First as possible I will post some sound samples...

 

[ilfungo]

I would like to understand if it's normal or why this happens?
the positive half-wave is more controlled while the negative one has strange peaks,
but I've seen some samples
Dry drum and Analog _Tube 670 and I see the same behavior

Attached 2 screenshots from pro tools (dry drum and processed 8db compression Time 1 pos)
Thanks!!!

 

[scott2000]

Interesting.... Maybe some kind of bias movement??? Doesn't bias affect this behavior??

 

[ilfungo]

Hi Scott2000
thanks for your answer
sorry I'm not an electronic exerpert but how the bias is set accordly with schematics?
Thanks!

 

[ilfungo]

The sound is good!!!
But I'm trying to understand why this happen....
Could be a simple matching tubes problem ( i've bought them as matched but I don't have tube tester to see if is real).

 

[ilfungo]

does anyone have any ideas?

 

[ilfungo]

News
I've found online:
1: dry drum samples
2 :same processed with Anamod 660 ( with all settings)

after I have processed the samples with my unit , the result is the same.
Also the Anamod have the same behaviour
At this point I think it's normal, but why this happen?

 

[Dmichel123]

I think maybe you're seeing the first transient that gets through while the timing cap charges. Attack time  is .2mS, about 1/4 of a 1kHz wave. I think.

 

[justinheronmusic]

Front

Am I correct in saying that you built one of these? Did you make a PCB for it? Do you have Gerber files or any info? I would love to build two of these compressors!!

 

[petermontg]

Am I correct in saying that you built one of these? Did you make a PCB for it? Do you have Gerber files or any info? I would love to build two of these compressors!!

Hi justin,

I have boards for this just in the middle of proofing them. I am a bit reluctant to let them out at the moment as there is word that you can still order the 660 from TDP's son???

Theres not much in it so it wont be hard to go from the schematic.

Also bear in mind the schematic here is an early version and does not fully correspond to the finished version of the 660.

I've came to the conclusion that there are 3 different versions of the 660 in circulation. This schematic been the very first.

The release timing has one change on pin 2 thats not on the schematic and changes around the LM346. Changes around both trimmers and a couple of extra caps.

Give the schematic ago and report back.

Best
Pete

 

[Tubetec]

I hadnt seen this before ,
Anything I saw of Tims designs is amazing though ,

This 660 is an interesting beast , all tube audio signal path , but solidstate CV chain makes a huge saving in cost and power consumption ,

If a tube compressor makes unpleasent noises it usually because of imbalance ,
You could number the tubes then swap the sockets until a better balance is found , or maybe one of the tubes in the set is out of spec badly enough to throw things off .

Is the balance control on the front panel?
, you could try adjusting it under dynamic signal conditions to see if things improve a bit ,

Im having a hard time visualising exactly whats going on in this circuit , a redraw simplified would be great

The service documents and manual would also be nice to see , Tim might have left a few clues about the theory of opperation in there .

 

[petermontg]

Service documents would be great. I've yet to come across them. Yes, balance is FP mounted across dual 500R potentiometer. Later versions have this area more complex.