M2 edcor transformer specs

[Russellc]

A few times in the M2 and Mr Johnson's M2 related threads I have seen mention of First Watt measuring the transformers frequency response to screen out ones not good enough for their service.

What is required to measure these transformers, I assume it is important to perform this screening if First Watt is doing it.

Having used these transformers for a few M2 builds, they sound good, but what do I know.

Russellc

 

[Zen Mod]

just chill

Pa must give something to interns to do and learn

(he almost fried my brain in all these years .... and I'm not even intern ...... luckily , have no brain to fry )

 

[kbergsson]

You are in deep Russellc, and so am I as I did not measure mine. There was however a mention somewhere in the M2 threads that one could use trimmer resistors to fine adjust the autoformer output or something?

 

[Russellc]

You are in deep Russellc, and so am I as I did not measure mine. There was however a mention somewhere in the M2 threads that one could use trimmer resistors to fine adjust the autoformer output or something?

Snubbers maybe? Well if Zenmod says chill, chill I will.

Russellc

 

[Russellc]

Zenmod, my concern was for a perfect set for the M25 build. Somewhere in one of these threads I think Mr Pass mentioned he might send a box of measured ones to the store? We will see.

Russellc

 

[Zen Mod]

well , if you want to worry , just triple it (worry amount)

with these amps/pcbs , you know you can choose Edcor , Jensen , Cinemag



you could be surprised how some things can be different ..... and brain simply not caring for

 

[Soundhappy]

....There was however a mention somewhere in the M2 threads that one could use trimmer resistors to fine adjust the autoformer output or something?

Was nice Guy who shows us multiturns trimmer instead of two 10R resistors at 2SJ74| 2SK170 buffer output.
More easy way to get 0mV DC offset if jfet's is not perfect matched pair, good trick and Edcor is not saturated.

For test's of input transformer frequency response Audio Precision are superb tool

 

[Zen Mod]

boyz , don't make an issue of non-issue

for regular Greedy Boy , there is no need for fussing about everything ...... then more

Papa is manufacturer , his way of thinking and preparing entire production logistic is completely different realm , than of one doing just a piece for himself

 

[Mark Johnson]

If you have a dual channel digital oscilloscope it would be pretty easy. Tell the scope to measure the amplitude (Vrms) of both channel1 and channel2, and also to measure the frequency (Hz) of channel 1.

Connect a 50 ohm signal generator to the primary. Connect the channel1 probe to the primary and the channel2 probe to the secondary. Tell the signal generator to apply a sine wave to the primary; watching the frequency readout on the scope, adjust generator to 10 Hz. Write a line in your lab notebook

freq=XXX Hz Chan1=YYY volts RMS Chan2=ZZZ volts RMS​

Repeat for the E6 series of frequencies, all the way up to 100 kHz

f= 10, 15, 22, 33, 47, 68, 100, 150, 220, 330, 470, 680, 1K, 1.5K, 2.2K, 3.3K, 4.7K, 6.8K, 10K, 15K, 22K, 33K, 47K, 68K, 100K Hertz

Now plot (Vout/Vin) versus frequency using Excel. Voila, the frequency response of this one particular Edcor transformer.

I'll let you decide whether you want to make the measurements with the secondary loaded or unloaded, and also whether you want to make the measurements with the Zobel Network connected or disconnected.

 

[Zen Mod]

perfect

and one ends with 10K+680p

 

[kbergsson]

You hit the nail on the head Soudhappy.
Even if my edcors are unmatched I sleep quite well

 

[Zen Mod]

I can bet that Mr. Winder himself made that matching good enough , from the start

 

[Russellc]

Was nice Guy who shows us multiturns trimmer instead of two 10R resistors at 2SJ74| 2SK170 buffer output.
More easy way to get 0mV DC offset if jfet's is not perfect matched pair, good trick and Edcor is not saturated.

For test's of input transformer frequency response Audio Precision are superb tool

Interesting, I don't remember seeing this tidbit. Link? Maybe use 10R or 20R pots?

Russellc

 

[Soundhappy]

Interesting, I don't remember seeing this tidbit. Link? Maybe use 10R or 20R pots?

Russellc

Russellc find this post around midnight was not easy Enjoy !
Yes thanks to Eric for the tip and interesting M2 DIY photos

Official M2 schematic

 

[Soundhappy]

See connections on the Papa buffer schematic
left side with jfet source resistors and on right side with multiturn 20R trimmer.

 

[Russellc]

See connections on the Papa buffer schematic
left side with jfet source resistors and on right side with multiturn 20R trimmer.

Thanks. Seems most useful for those whose Jfets are not perfectly matched.

Has anyone here tried this? Appears straight forward. I realize that is another circuit, this pot idea would be fine simply replacing the 2 10R resistors?

Russellc

 

[Soundhappy]

...I realize that is another circuit, this pot idea would be fine simply replacing the 2 10R resistors?

Russellc

Yes two 10R = one 20R multiturns trimmer
Fellow Diyer Eric write more details in his post.
Source : http://www.diyaudio.com/forums/pass-labs/281520-official-m2-schematic-272.html#post5454431

 

[Russellc]

Yes two 10R = one 20R multiturns trimmer
Fellow Diyer Eric write more details in his post.
Source : http://www.diyaudio.com/forums/pass-labs/281520-official-m2-schematic-272.html#post5454431

Thankyou so much Soundhappy, very much appreciated information!

Russellc

 

[Russellc]

A few times in the M2 and Mr Johnson's M2 related threads I have seen mention of First Watt measuring the transformers frequency response to screen out ones not good enough for their service.

What is required to measure these transformers, I assume it is important to perform this screening if First Watt is doing it.

Having used these transformers for a few M2 builds, they sound good, but what do I know.

Russellc

Here is the post: Concerns some of them having a high frequency peak...

http://www.diyaudio.com/forums/pass-labs/321925-diyaudio-watt-m2x-3.html#post5431448


Russellc

 

[WalterW]

Thanks. Seems most useful for those whose Jfets are not perfectly matched.

Has anyone here tried this? Appears straight forward. I realize that is another circuit, this pot idea would be fine simply replacing the 2 10R resistors?

Russellc

I posted some findings in the B1 v2 thread.
B1 Rev. 2

Even with perfectly Idss matched JFETs you don't get zero offset. So trim pot seem always necessary.