ruffrecords

OEP A262A2E
« on: November 29, 2019, 09:19:35 AM »
The OEP A262A2E is a small 150:600 ohm input transformer with split winding so it can be wired 600:2400 if you wish. I have not paid this transformer any attention until I saw it used as an OUTPUT transformer wired 2400:600 in a 500 series all tube mic pre  by gemini86 (Rodney) here:

https://groupdiy.com/index.php?topic=51020.msg647656#msg647656

The A262A2E is specified to 100mW at 300Hz which is +20dBm - quite respectable, but only 1mW at 30Hz which is 0dBm - not so good. So I thought it was worth buying one an putting it through its paces. It arrived yesterday. All I have tine to do was measure the inductance at 100Hz with the windings in series (2400;600). Primary was about 10H and the secondary was about 2.5H. Perhaps not as high as they should b but, if the core is all iron, the inductance will rise at lower frequencies to the LF response might be OK. Tonight I will have a go at measuring its frequency response at 0dBu. Then I will move on to distortion.

Cheers

ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'


ruffrecords

Re: OEP A262A2E
« Reply #1 on: November 29, 2019, 05:51:31 PM »
I made some further tests tonight.

1. Frequency response at 0dBu and +18dBu in is pretty flat from 20Hz to 40KHz when output is unloaded.

2. With 600 ohm load the response at bothe levels is -1.25dB at 20Hz and -1.25dB at 20KHz

3. IKHz 3H distortion at 0dBu in was 0.0057%. with output unloaded. At +18dBu in it was 0.17%

4. At 0dBu input, distortion was measured from 100Hz down to 10Hz. At 100Hz it was 0.051%, at 40Hz it was 0.11%, at 20Hz it was 0.23% and at 10Hz it was 0.8%

I then tries to measure the low frequency distortion with an input level of +18dBu (+12dBu output). However it rose to 2.14% at 40Hz and to 14.6% at 32Hz. Clearly it was not going to reach down to 20Hz at this level. Instead I increased the 20Hz level in 1dB steps from 0dBu. At +9dBu input (+3dBu output) it reached 1.09%. It reached 2,76% at +11dBu input (+5dBu output).

Conclusion, low frequency distortion performance makes it unsuitable as an output transformer at levels significantly above 0dBu output.

A pity because it is a nice small low cost transformer.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Holger


Whoops

Re: OEP A262A2E
« Reply #3 on: January 13, 2020, 10:29:12 PM »
Thank you so much Ian

Some people seem to like this transformer for it's more lo-fi/distortion characteristics.

It's inexpensive so you get what you pay for here

vinyvamos

Re: OEP A262A2E
« Reply #4 on: January 17, 2020, 07:16:20 PM »
I have been meaning to buy a few from this OEP range as I am curious. Thanks for the test data Ian. I must say their datasheets are well detailed which is great. It bugs me when distortion and inductance measurements are not published
Atomic Analog Devices
*************************
Studio Silo - A Tape Studio in East Iceland


 

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