Hi Tom,
After you get the project built up and do some testing, if you have time
mess around with the secondary terminations. I'd be very interested to find
out what happens.
Regards, Jim
At 12:40 PM 3/23/2011, you wrote:
I received a couple UTC A20's and should have my Edcor's in tomorrow. I
should have the chassis made and wired by late weekend. I am very curious
to hear the differences and see if they are very noticable. Regardless, it
will be a fun project.
Tom
--- On Wed, 3/16/11, Brian Roth <[email protected]> wrote:
From: Brian Roth <[email protected]>
Subject: Re: NEOTEK: Adding Transformers
To: [email protected]
Date: Wednesday, March 16, 2011, 10:11 PM
On 3/16/2011 13:02, Ike Zimbel wrote:
>
> Hi Brian,
> I'm pretty sure you published those specs on the Ampex list...check the
> archive!
> All the best,
> Ike
Dear Ike,
I forgot I had posted some measurements on the Ampex list! I found the
following from the Jan, 2005 archives, which I believe were measurements
of the "smaller" series of Edcors:
<http://www.edcorusa.com/products/143-wsm600-600.aspx>http://www.edcorusa.com/products/143-wsm600-600.aspx
Here is what I wrote 6 (!) years ago:
The replacement Edcors (600:600 impedance versions) arrived today, and the
DCR was MUCH more reasonable. Approx. 54.1 Ohms primary, 54.5
secondary. Level drop from open loading on secondary to 600 Ohms was just
a bit under 1.5 dB, much what I would expect.
For testing, I breadboarded a "zero Ohm source" driver with a 5534 opamp
running as an inverter: 10K input and feedback R's, 22 pF compensation cap
(between pins 5 and 8) and 22 pF in parallel
with the feedback R to tame any overshoot and ringing from the opamp
itself. -3 dB response with the opamp circuit calcs to around 723 kHz. I
powered the 5534 with +/- 20 VDC from my bench
supply, which allowed just over approx + 24 dBu/m at clipping.
1 and 10 kHz squarewave response through the iron looked very good, loaded
or unloaded, with just a tiny bit of overshoot and ringing. Frequency
response was beyond anything I could measure with my
Amber (bandlimited at around 500 kHz or so) which came up with -1 dB at
approx 6 Hz and 300 kHz. Bypassing the Amber and just watching the scope,
usuable response was extended, and limited by the
rolloff of the opamp driver on the top end. With a 50 Hz square wave,
there was very little tilt which indicates LF response well below 20 Hz.
Next I measured THD, and at some of the lower levels I was fighting noise
picked up from the breadboarding! Here are various "spot measurements".
1 kHz, 0 dBm = 0.0085% +10 dBm = 0.005% +20 dBm = 0.0025% (noise was
an obvious factor!)
100 Hz, 0 dBm = 0.03% +10 dBm = 0.015% + 20 dBm = 0.05% **
50 Hz, 0 dBm = 0.055% +10 dBm = 0.035% +20 dBm = 0.18% **
20 Hz, 0 dBm = 0.07% +10 dBm = 0.085% + 20 dBm = 0.7%
Spot checks at LF and + 20 dBm: 40 Hz = 0.3% 30 Hz = 0.45%
(Actual 20 Hz numbers may be a bit lower since my 20+ year old Amber was
having a hard time nulling at 20 Hz).
** Notice the THD dip at the "middle" levels at those frequencies. I
also think I detected a THD rise at levels below 0 dBm but was fighting
noise issues.
I have a bunch of other numbers, but you get the drift. Looking at Jensen
choices, this Edcor is just a bit "rattier" than a JT-11-EMCF which sells
for $66.85. These Edcors are a bargain!!
Bri
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