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
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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