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 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 ------ View the list online at: http://www.mail-archive.com/[email protected] You can unsubscribe at anytime by sending an email to mailto:[email protected] with "unsubscribe neotek" in the message body. If you have any difficulties, or questions --please send an email to mailto:[email protected]. The Neotek list is lovingly hosted by Catapult Web. Remember that any message or reply sent to the list will be automatically forwarded to all subscribers. Vive Le Neotek! Thanks.
