Hello All, Just an update FWIW: I built the transformer box and have been playing around with it. I used Edcor and UTC transformers. I still have some experimenting to do with the unit but overall it works quite well. Although like Kris states below, it can be hard to hear a significant different (coloration) with some material. I think it will still be a useful unit and it was/is a fun little project to make. This weekend I'm going to put a list together of the needed caps to recap my Master Section of my Series 1. I recapped the channels and PSU three years ago but did not do the Master, so that is next on the project list. Also, I'm visiting the mic museum here in town: http://www.sssmilwaukee.com/Microphone%20Museum.html This should be a blast!!! Although he does not have any Neotek's... Take care, Tom
--- On Fri, 3/25/11, Kris w <[email protected]> wrote: From: Kris w <[email protected]> Subject: Re: NEOTEK: Adding Transformers To: [email protected] Date: Friday, March 25, 2011, 1:18 PM Hello Neotek list, I have been reading all the transformer posts, and have been enjoying the info. For what its worth, I experimented briefly with transformers, in my Neotek. My motivation for giving it a try was simply because I have been doing a lot of 60's/70's soul/r&b and funk recordings, and I just need a heavier, thicker sound, in order for it to sound right, so I tried transformers, but my method only involved using my ears, since I was approaching the whole thing really from just a sound standpoint. I tried A couple Altran's some Crimson, and a vintage API. Honestly, I was disappointed, the Crimson transformers left the sound about 98% unchanged, I really had to listen hard, and even then I wasn't quite sure if I could hear any difference. surprisingly, the vintage API's were very close to the Crimsons. I could here only a very slight difference in tone, the Altrans changed the sound the most (one of the ones I tried is supposed to be a 100% clone of the coveted Neve output transformer, I don't know which one, but the one everyone likes), but in the end, with the clean clear open, extended sound of the Neotek, the transformers only changed the sound maybe 5% or less. Turns out if you want to make a heavy sounding funk recording, you just have to get an old console. My only thoughts though in retrospect is this: I was only trying one transformer at a time, maybe it would be a bit different if I loaded every single input and output, but it still wouldn't have got me back to 1970, but if you wanted to ad transformers to a Neotek and not have them get in the way of the sound, or maybe even help the sound a bit, try a Crimson and see what it dues for you. -Kris P.S. I love my Neotek, and the sound still amazes me, but if you were wandering, now on the side, I have a vintage early Auditronics from about 1970, loaded up with UTC input transformers, Triad outputs, and passive inductor EQ, the sound is very nice, just the complete reverse or a Neotek. From: Matt Syson <[email protected]> To: [email protected] Sent: Fri, March 25, 2011 10:12:11 AM Subject: Re: NEOTEK: Adding Transformers Hi As a rough guide, stepping up to a higher impedance tends to reduce the HF response as the winding capacitance increases. This is a pity because you could get fantastic 'gain' from a transformer as a valve grid or FET takes virtually no input signal current apart from it's capacitance. 50K to 100K is around the maximum secondary impedance for usual winding techniques to allow response 'flat' to 20 or 30KHz. Transformers with lower ratios are more suited to transistor inputs although singe there are some fabulous low noise transistors and IC op amps available now a transformer is not necessary. Matt S On 25/03/2011 14:41, Gabriele Ponticiello wrote: Tom, you'd be surprised at how little my knowledge is on the subject matter of transformers. I want to add input transformers to former reel to reel recorders' tube electronics (yes, those things...) to convert 'em into mic preamps and I am looking at contemporary catalogues from Cinemag and Sowter. I am also looking at old "mic to grid" transformers by UTC, Triad, Altec, Ampex, RCA, Rauland, Newcomb, Dukane, Bogen... You name it: they all have a secondary rated around 50.000 ohms and an input around 200 ohms. The former current manufacturers only have one model each with those figures (Cinemag has a good Altec 4722 replacement and Sowter has a replacement for the Ampex 351 in their vintage section) and when I personally inquired about which of their model could best suit my needs (providing schematics) they both indicated a 200 in/10.000 out ohms. Since I know nothing 'bout transformers, I keep wondering why the secondary figure has changed in years... Then again... sorry, maybe this is not the right place. Gabe. Da: Tom G <[email protected]> A: [email protected] Inviato: Ven 25 marzo 2011, 14:05:05 Oggetto: Re: NEOTEK: Adding Transformers Gabe, I would benefit from this too.; good idea. I know there are DIY forums that discuss transformers, but I wasn't impressed with the knowledge level. Tom --- On Fri, 3/25/11, Gabriele Ponticiello <[email protected]> wrote: From: Gabriele Ponticiello <[email protected]> Subject: Re: NEOTEK: Adding Transformers To: [email protected] Date: Friday, March 25, 2011, 3:42 AM Speaking of transformers... Jim, Tom: is there a virtual place where we could discuss the specific subject matter and I could ask questions without annoying Neotek aficionados? Thank you. Regards, Gabe Da: Tom G <[email protected]> A: [email protected] Inviato: Ven 25 marzo 2011, 04:23:39 Oggetto: Re: NEOTEK: Adding Transformers I should have enough spare parts (pots, caps, etc.) to start experimenting now that I have my transformers. The series resonant circuit...I am quite familiar with the resonant frequencies of guitar and bass pickups because I make them. Usually during R&D of a new pickup design, one of the tests I do is to document the resonant frequency. I will have to look up what capacitance's I'll be running into. My 2 track is a Sony APR-5003 and my AD/DA converters are SSL Alpha-Links. Thanks for all the info! This will be a very interesting and fun project to build. Tom --- On Thu, 3/24/11, Jim <[email protected]> wrote: From: Jim <[email protected]> Subject: Re: NEOTEK: Adding Transformers To: [email protected] Date: Thursday, March 24, 2011, 11:01 AM Greetings, Hi Matt, Great point.............I wasn't sure how much to write (or not). Please feel free to contribute anything else that comes to mind. Regards, Jim At 05:53 AM 3/24/2011, you wrote: > Hi > When simply adding a transformer on an output you need also to consider the > output capacitor, assuming the circuit uses them which many do. > This will cause a series resonant circuit with the transformer and it it > possible this resonance happens in the audio band, or nearby. High impedance > 'line in' transformers of remote connected gear suffer less but it is quite > easy to get a 3dB or more 'boost' at some frequency. Increasing the output > capacitor WAY beyond usual values usually 'cures' this. Values in excess of > 1000 uF may be necessary. > I had this discussion a while back with a guy using a 600 Ohm 1:1 transformer > (Sowter but the principle is valid for any similar types) and with a 47uF cap > (as used in the suggested circuit) it gave a 4dB boost at about 20Hz, hardly > an accurate response. (I can't remember the exact values now but it is an > example). Gratifyingly doubling the cap halved the boost frequency, as 'laws' > predict. > Matt S > > On 23/03/2011 23:35, Jim wrote: >> >> Hi Tom, >> >> Sorry I didn't explain this..............I had posted about transformers >>previously and assumed you saw that. Please keep in mind that entire books >>have been written on these topics. Anway, to maintain its rated frequency >>response a transformer requires some specific secondary termination, usually >>an R, sometimes an RC. In many cases this is achieved by the input Z of the >>component that its feeding. Without going into too much detail and history, >>back in the "old days" equipment was designed to a standard 600 Ohm line >>(matching load); all inputs and outputs were "matched" so that anything could >>be connected to anything else and it would all work out just fine. >> >> Since we've pretty much abandoned that approach, we run into the >>situations of non-matching loads; which can adversely affect both frequency >>response and the optimum transfer of voltage/power/etc.. Now we tend to think >>in terms of bridging loads; which is to say that the optimal situation would >>be an output impedance of zero feeding an infinite input impedance. Of course >>in the real world that situation does not exist. In general, we'll figure the >>output Z is pretty low (a few Ohms) and the input Z is high (say at least 1K >>Ohms). If you have a scenario where the ratio is on the order of 1:1000 or >>greater, things can work out pretty well. The problem comes when the output Z >>is high and the input Z is low. The most common example of this is plugging a >>bass guitar (with passive pick ups) directly into a console. The relatively >>high output Z of the pick up is severely loaded down by the relatively low >>input Z of the console. That's why we usually would use some type of direct box that matched the correct loading for the pick up; for example plug the same bass into an old tube bass guitar amp. Its going to sound much better. Typical input Z will be over 1MR, sometimes up over 5MR. >> >> Now lets look at your specific situation. The UTC is likely rated to drive >>into a 600R load (see if you can find the data sheet for it; there may be >>several ways to strap the input and output side for some other combinations; >>150R, 300R, etc.). The actual load will be determined by what the input Z of >>the device it is feeding. Say for example, it's feeding a solid state line >>level input device. That may have an input Z of between 1K and 10K; feeding a >>tube line level device may have an input Z of over 100K. So in either case a >>bridging load is in effect, but at pretty different ratios. Hook the >>transformer up "as is" or with the strapping set for 600:600. Then after you >>have measured/listened, etc. try installing a resistor in parallel with the >>transformer secondary; for example, try a 500R pot with just one end and the >>wiper connected. That puts the resistor in parallel with the input Z of the >>loading device, and will result in dropping the Z the output transformer sees. This will likely result in lower output level, but the interesting part is how it may affect the frequency response. So, this allows you to "tune" the circuit to perhaps achieve a beneficial effect. You don't have to limit yourself to the value I gave; try whatever you have; listen and let your ears be the judge. >> >> OK, hope that helps and that I didn't make too many errors. Just coming off >> the flu myself. Good luck! >> >> Regards, Jim >> >> >> At 01:22 PM 3/23/2011, you wrote: >>> Hi Jim, >>> >>> What do you mean exactly? Try using the different impedance taps on the >>> UTC's? Sorry, but I think I might be on the verge of a nasty cold! >>> >>> Tom >>> >>> --- On Wed, 3/23/11, Jim <mailto:[email protected]><[email protected]> >>> wrote: >>> >>> From: Jim <mailto:[email protected]><[email protected]> >>> Subject: Re: NEOTEK: Adding Transformers >>> To: <mailto:[email protected]>[email protected] >>> Date: Wednesday, March 23, 2011, 12:10 PM >>> >>> 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 >>> ><<http://us.mc657.mail.yahoo.com/mc/[email protected]>[email protected]> >>> > wrote: >>> > >>> >From: Brian Roth >>> ><<http://us.mc657.mail.yahoo.com/mc/[email protected]>[email protected]> >>> >Subject: Re: NEOTEK: Adding Transformers >>> >To: >>> ><http://us.mc657.mail.yahoo.com/mc/[email protected]>[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.edcor us >>> >a.com/products/143-wsm600-600.aspx><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 >>> > >>> > >>> > >>> >------ >>> > >>> >View the list online at: >>> ><<http://www.mail-archive.com/[email protected]>http://www.mail-arc hi >>> >mailto:ve.com/[email protected]>ve.com/[email protected]>http://www.mail-archive.com/[email protected] >>> > >>> > >>> >You can unsubscribe at anytime by sending an email to >>> ><mailto:[email protected]>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]>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. >>> > >>> >>> >>> ------ >>> >>> View the list online at: >>> <http://www.mail-archive.com/[email protected]>http://www.mail-archive.com/[email protected] >>> >>> You can unsubscribe at anytime by sending an email to >>> <mailto:[email protected]>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]>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. >> >> >> ------ >> >> View the list online at: >> <http://www.mail-archive.com/[email protected]>http://www.mail-archive.com/[email protected] >> >> >> You can unsubscribe at anytime by sending an email to >> <mailto:[email protected]>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]>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. >> >> >> >> >> No virus found in this incoming message. >> Checked by AVG - <http://www.avg.com>www.avg.com >> Version: 9.0.894 / Virus Database: 271.1.1/3524 - Release Date: 03/23/11 >> 07:34:00 >> ------ 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. No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.894 / Virus Database: 271.1.1/3527 - Release Date: 03/24/11 19:34:00
