The AM Forum

I just took delivery of a Modulation Transformer still being made. It seems it would work well for a transmitter with a 30w-40w P-P modulator like a Pair of 6L6's. It is in current production by Sowter in the UK. It is a bit pricey though, especially with US dollar where it is right now.

Impedance 5k to 5k pri/sec, 200ma sec, 1500vp-p voltage on sec

It may be a good candidate as a replacement for mod iron in several of the older boatanchors using a single 6146 or 2e26 like Ranger's, Globe Scout 680, and others. Or you could use it build a modulator for a Heath DX-35, DX-40, Eico 730 or others. Not to mention homebrewing small AM transmitters, like something using a Pair of 6L6 modulating a 6146.

Here's the link:

http://www.sowter.co.uk/acatalog/SOWTER_TRANSFORMERS_SINGLE_ENDED_OUTPUT_17.html#a317 (http://www.sowter.co.uk/acatalog/SOWTER_TRANSFORMERS_SINGLE_ENDED_OUTPUT_17.html#a317)

and another with more data:

http://www.sowter.co.uk/single-ended-output-transformers.php (http://www.sowter.co.uk/single-ended-output-transformers.php)

In a thread from 2008. Stu--AB2EZ-- mentioned AnTek Inc. as a source for a toroidal modulation transformer which he used with good results on his Viking Ranger, followed by a couple more AnTek toroidal transformers that he bought for modulating a high power rig. Search on AnTek, and the thread will come up about third.

I had a look at AnTek's toroidal power transformer line, and they were very robust indeed, and about 15% less expensive than the nearest Hammond equivalent.

Anybody else have any experience with AnTek's products as modulation transformers?

Cheers,

Brian

Actually I have. My company has been working on a prototype plate modulated "boatanchor" type transmitter using a DDS VFO (80m-10m) and all tube design. With solid state regulated supplies having separate supplies for Fils, Bias, Mod B+, PA B+, & other low voltages. This is for new manufacture, hopefully to begin production & distribution sometime in early 2013.

We are modulating a 6146 with a PP pair of 6L6's and use an Antek Toroidal for the mod tranny. The same setup can have increased output by adding another 6146, increasing the output of the modulator (which is dialed back right now running lower plate voltage) and changing the mod tranny.

We swept the radio and it has a flat audio response on the output of 60hz-11kHz. We ran the TX on a dummy load on 40m with pink noise input running at 110% modulation for a continuous key down of 26 hours. We noticed no significant problems.

Some of the folks here heard this prototype on the air and can comment if they feel so inclined on how it sounded on the air.

John LeVasseur, W2WDX

How are you connecting the mod transformer? B+ straight through the secondary, modified Heising or parallel-feed?

I think there is a lot of promise in using the Hammond 125FSE and GSE single ended transformers for modulation transformers. Both are large heavy iron and are rated for 90 mA and 100 mA DC current.

A 4 or 8 ohm input can be matched for many output impedances and using a modified Heising choke to get rid of the DC bias probably allows them to be rated at 100 watts or so. I plan to test a GFE soon.

Pat
N4LTA

actually, with a single-ended transformer, you might not need the heising choke at all. most of these transformers have a gapped core to handle the unbalanced DC on the primary. feeding one backwards, the primary is hooked inline with the power supply and the RF final. normal mod iron has a gapped core to deal with the unbalanced DC on the secondary. the reason for the heising coke is to keep the DC current, which is what causes core saturation, off of the transformer. this is what is needed when a backwards-connected audio transformer or even a power transformer is used as a modulation transformer.

Yes - They are rated for 90 and 100 mA of DC which works well at lower powers but I suspect that their power can be tripled with a choke. They are big hunks of iron for the power rating. Hi pot rating may be their downfall for larger transmitters.

Hammond also make a big moose of a SE transformer rated at 300mA and hi potted to 3500 volts. It weighs 28 pounds and has a 55 H winding but it cost  $325. I suspect that it would work fine at 200-300 watts.

I have seen the Sowter tranformers but they are too hooked up with the audiophoolery crowd to suit me. Way to expensive anyway. At those prices , I am sure Hammond would wind a custom transformer if there was any demand at all. Hoerboer could also do it if there was any demand.

Pat
N4LTA

Sowter is a very conservative and iirc old English mfr of high quality xfmrs. Excellent performance and specs in general.

They are not "hooked up" with anyone.
Audio hobbyists learned of them from people in England and have sought them out, as have recording studios (when there still were recording studios...). Nothing whatsoever to do with any snake oil or nonsense. FYI and FWIW.

Generally speaking you get what you pay for.

Since we do not usually want or need response out past 20kHz. their value may or may not be there for AM ham users.


                             _-_-bear

Don't know about use as mod tranny--still have to try that--but Stu's posts served as inspiration and I tried Antek 12 Volt Filament tranny to excite grids of 811A's in PP.  Exciting with one channel of board-kit 15 watt stereo amp with line level audio.  Works great with super response.  Modulating single 813 with Stancor multimatch.
73's Geo 

Very nice!

Geo,
I agree, "very nice"' and your rig looks like a Christmas tree, what with the slightly out of focus pilot lights. 

Very nice panel and window layout in particular...  Pix of the amp inside?

Anytime someone sell a 30 watt modulation transformer for $300-400 or more delivered -  they are hooked up with some kind of Phoolery. Quality is one thing and maybe they are gold plated - but Sowter's customer base is deep into audiophoolery.

People who pay $300- 700 each for an output transformer meet my definition of audiophoolery - but that's just my opinion.

Pat
STF

Thanks Guys.  Here are some slightly better pics--you can see the antek tranney better. This started out as a junkbox prototype RF deck--hence all the odd sized DoD surplus chassis and "home depot" stuff. Was experimenting with various biasing arrangements, neutrialization, and rf coils on single 813 deck.....and took off from there.  Went a bit farther than I'd originally intended. Bandswitching and JV2 knobs, paint, cabinet, pilotlights were after-thoughts.  Paint left over from R-390 panel repaint.  Coils are all homemade--based on a 15 year old QST article--highly recommend it.  Can get everything for em at Lowes or Home Depot. Power supply is on plexiglass and oak slat chassis.  Operated it on floor for a longtime--which allowed me to try different things and want to continue with that out here in CA.  Still want to experiment with Antek Mod tranney and modified heising...maybe add preamp, try some neg feedback.  Plenty of room in cab for it.  Note shack doors are closed--so the cat can't come in  ;D 

Metal work is all dremel, scroll saw, etc.  Used fly cutter to do two meter holes and then resorted to borrowing a punch.  Too much work!

When company alerted me of impending Calif move, XYL demanded I get it off the basement floor so cabinet was something put together in hurry--inexpensive shelving and flashing/aluminum screen for shielding RF deck.  When I get it out here--is going back on bench or the deck to I can continue to play/add on  :)

I don't post much but love to read everybody's ideas here--much inspiration derived from em. 


Best 73's Geo

What decade (or century) are you living in I wonder? Let's see ... a 30w mod transformer in 1957 cost about $49 so adjusted for inflation the same transformer today would cost about $400. Seems about right to me.

This thinking is the reason you will never see any new electronics built with any quality ever again. To hit the price points based on 1950's pricing means you MUST build junk to hit the price anticipation of the Ham radio buyers who think everything should cost the same as it did decades ago.

The same transformers sold by other manufacturers to the audiophoolery market sell for thousands of dollars. Sowter is actually selling the type of transformers they build for low prices based on current dollar values.

You are the "phool" if you think you are going to get a new transformer of any real quality for our applications on the cheap, which anything under $300 would be.

The majority of sales for Sowter BTW is to the guitar player market, not the audio fools. And they are cheaper than Hams ("starving musicians") when it comes to buying stuff. Marshall and Vox used to use Sowter to build their transformers, before Korg bought them out and moved manufacturing to China.

So if you want an inexpensive new transformer buy something made in China, otherwise go buy your used junk at a fester.

Sorry ... that thinking just pisses me off.

Geez!

John

I totally agree with Pat, the audioholes simply dont care what it costs and I enjoy seeing them get ripped off.

In 1957 you could buy a NIB ART-13, TCS, or similar mod transformer for $5.


I dont know what orfice you pulled that number out of but in 1957 a generic communications style 30W mod transformer, even multi tap, was under $10. The much praised CVM-1 was a whopping $13.80 and those are list prices.
The DX-100 replacement was $16.95 if I remember.
So using your inflation example a CVM-1 should be around $110 today and put the 300W CVM-4 at around $315 which sounds just about right.



Well you better get used to it since anyone who comes here expecting to pimp overpriced audiohole stuff deserves it.

Maybe if you go to the Collins forum you would find a more receptive audience as many of them are big on cash but low on smarts.
Its usually the other way around on here and most elsewhere ;D

Unless American transformer winders get their prices in line with realistic profit margins I would welcome Chinese or any other countries iron if it offered a decent savings.

Carl

Curious what P. Dahl would say if he were still around.  There was a great guy making a great product.  Timely and tape wound too. I don't think his margin was excessive.  Of course copper, etc. has sky-rocketed since.

Call up his price list on mod. iron replacements.  Tres interessant for 1990's.

For 7 years I was selling locally built transformers in direct competition with Dahl. I sold for 30-40% less PLUS cleared a nice profit so dont tell me about Dahls "perceived" margin. While Dahl regularly raised prices claiming copper and steel cost increases my guy had longer time periods and less dollar increases.
Id still be selling them if the company owner had not died suddenly and the place was liquidated.

I also quoted shipping charges up front instead of shipping the most expensive way with shipping COD...one of Dahls known tricks.

Carl

anyone who can get me hifi output iron equal or better than Sowter quality, at a price that is better, like 25% of Sowter retail, step up. I'd like to buy some. We can both make some money. I am quite serious. I'd even consider Chinese product, if I could figure out how the heck to do business with them.

But if you have product, I'd like to see it.

In fact, I do not think I can wind an output transformer in the 30+ watt class for $100 in raw parts, it would be darn close today... and that is buying in what would be commercially small lots of core, wire and associated parts. (forget about labor, overheads and profit margin)

Step up, I would do it.

I own two Meteor Swiss coil winding machines. C'mawn!

               _-_- bear

Why not try it and see? Something not fancy and with only a few impedance options. Open frame (if feasible at 30W) with color coded leads, user tapes up or cuts what isnt needed.

KISS

Where, in the U.S.?  It won't happen.  Why:  Because of a hidden cost in America that most hams fail to notice--the sky high cost of employee medical plans now.  This is one of the big reasons your RF amp that was $2K 10 years ago is now $4K.  Of course this assumes the manufacturer wants to have decent manufacturing employees who have jobs with benefits like disability insurance (a good idea for people in machine shops).    But since consumers now think everything should cost what cheap crap goes for at Great Wal-Mart of China, they get junk and outfits like Apple have their stuff made where no one has ever heard of medical plans.

Where did your computer come from Rob?

Also, much of the so called news about Apple factories was made up.

http://online.wsj.com/article/SB10001424052702304459804577285713362126158.html?mod=ITP_businessandfinance_0

http://www.youtube.com/watch?v=DDWgMXoQnH8&feature=youtu.be

Kindly explain your desire to make this personal.  I use a mac; I did not know where it was made at the time and in 2008 when I bought it I was not concerned with buying American like I am now.  Does any of this change where Apple's products are made?

And, where are they made Steve?  Are they made in the U.S.?

You did not know in 2008 that nearly all computers (or at least the component parts) are made off shore? Really?

The sky is blue.
Water is wet.
Apple (and all other computers) are made off shore.

Tell us something we don't already know.

BTW, it's hardly personal. I own five Apple products currently and have been using their stuff since the early 90's.  ;)

First let me apologize for the attitude. In my defense it was late, and I just had long argument with a supplier about pricing. So costs of quality products was on my mind and an irritation.

What I will say is I don't know where I got the $49 number, I thought I typed $19 (damn number keypad and chubby fingers.) My $400 number is spot on. If you included the inflation of the dollar, higher relative labor costs in the US, AND factor in the 12x increase on the price of copper since that time.

The audiophools are properly named. They are fools. However that doesn't change the fact that the cost of raw components is now high simply due to real costs. The people who buy the parts, the hi-end audio equipment manufacturers, are the ones who charge the outrageous prices. Simple single ended EL-34 based tubes amps selling for $40,000 is not uncommon. Does it cost half that to build it? Not even close. If it costs $1000 I would be surprised. So don't blame companies like Sowter, they actually are reasonable and inline with real non-audiophoolery costs.

Hammond is a steal BTW. They manage on economies of scale, due to larger production.

BTW, if you want to buy American, for anything, good luck. Our "cheap" American attitudes and need to have everything stay at the same prices over decades have forced this shift in economy.

Just look at MFJ versus any other Ham radio market company with products made here. Well the cheap Asian crap they sell is the number one product. Why? Because Ham's do not want quality or US made products, they want it all "on the cheap". We talk big about "buying US made", but when it comes down to it we Americans can't or won't pay for it. How many Ten-Tec's do you own? MFJ just bought out Palstar. And so it goes ...

Again sorry about the attitude in the earlier post. That was un-called for and I apologize.

John, W2WDX

When did this happen?

After disasters with a Paragon and Orion I bought new Id never own a Ten Tec product again.

I get enough of their amps in here for service to know they are inferior to even Ameritron in most areas.

Copper and steel costs are a crock, they are far less in China and elsewhere that has the natural resources and/or processing ability. We are paying for over the top union wages, EPA, OHSHA, and envirowhacko lawsuits plus out of sight energy costs.

A modulation transformer can be built in a basement with a trained housewife getting part time wages. Im sure there are many areas with assemblers who used to work for small transformer companies. There are other ways to keep the cost low.

Carl

You're not serious Carl, are you? Is he joking with me; pulling my leg?

A housewife in basement part time? That's a joke right?

First off, I own a company. I have to pay at least minimum wages, pay for disability insurances, pay my share of FICA, get all the information Homeland Security requires now for hiring, and all the other things that go along with ownership and employees.

Hiring a slave lady to work down in my basement would not a good business plan make. How long would that last? Maybe I could hire some illegal aliens and chain them to the winding machines. Or maybe I could get child labor in India to make them work for me. Ooo ... I could get a bullwhip!!! :P Yeah !!! {CRACK} Work you dogs!!!  ::)

Just so you could have your dream of a cheap modulation transformer. You are joking right?

Carl I can't take you seriously if you are gonna say things like that. And the price of copper IN THE USA is the highest it has ever been in history. Period. Take at look at this chart that goes back only to 1986. The price has risen 8 times over that period alone. 2009 was a good year though to buy.

http://en.wikipedia.org/wiki/File:Copper_Price_History_USD.png (http://en.wikipedia.org/wiki/File:Copper_Price_History_USD.png)

And I looked up the price of copper for Feb 1959 as being at .24k in USD per metric ton (adjusted from US ton). More than a quarter of the price of 1986. Those are real numbers.

And BTW copper prices are paid globally and the markets do not differ that much from each other. So the idea that China pays that much less for it, or it costs more to buy here is ludicrous. It costs more to produce it here making the margin lower for the producers, the sell price is the same set by the exchanges. (An oversimplification maybe but close enough to reality.)

Don't just take a stance to be right. Please.

Anywho, the Sowter seems like FB. Considering nobody makes anything like it anyway. Seems to be well made, like Bear said. I wired it into a Ranger I have here and it works well. I have to sweep it to see what it really does though. Maybe it's something to consider for a future venture.

John

A good transformer is NOT an easy item to fabricate.  Steel, copper, punching presses, winders, all of it comes at a price and not something you can do on a bench by hand without some sort of support:  E&I stuff, forms, whatever.  The less of those things you have, the less professional the item is.

And a design.  That damn design.  You can cite impedance ratios all you want, but as Heinlein said, "The map is not the territory".

So-so ones abound, just look & listen to some in critical auditons.

It goes back to the guy getting $100 for slapping a TV set and having it work just fine...$1 for hitting it, $99 for knowing where & how...

A good, well designed and produced transformer is worth every penny.

73DG

Yup ... this is I meant by reinventing the wheel. Carl, you seem to have some intrinsic knowledge. Wanna come work in my basement? I have cookies!!!

I wasnt commenting to you, its Bear that has the winder and all he needs to do is start a basement shop building small transformer runs. Others have done that and thrived if they are smart.

Yeah I do have the winders. Two. But when you look at the prices of the raw materials, the cores, the copper, the insulation, the screws, nuts, washers, insulators, paint, various goo compounds, tape, heatshrink, end bells, etc, then add in the labor costs, the taxes, the overheads it starts to look like a job that doesn't pay well until you get past a fairly high number of units sold! Then you go back around with the gov't carp that you have to deal with - even a 1099 to a legit subcontractor can be a nightmare. And TRY to find anyone who doesn't think that they should get $20/hr to "sweep ur floor". Find me someone PLEASE!!! Heck I'd pay someone to just clean the benches and restock parts!! Try to find that "part time person". Please.

I do know someone whose biz it is to wind custom audio things. He supports himself in his one man shop pretty well now. I think it took him over a decade to get to the point where he is on cruise control for that.

It just isn't an easy road to hoe, and unless you get the recipe right by accident, or "borrow it" or come with info from working for someone else first (there's another problem with hiring someone who is motivated and into the biz, vs. a "housewife" or other undocumented "worker") then ur going to spend a fair amount of time getting things right both from the mechanical construction part and the actual performance end.

Seems to me with the cost of copper now, ur going to blow through hundreds of dollars worth of wire before you make ur first *audio* transformer that is worth a darn. Power is probably going to be easier to get right.

Anyone who would like to run my winders, gimme a shout! :D

                          _-_-bear

Well, that rewinder in ME takes old iron apart and even counts turns.

Id start with something small and cheap that is known good and start reverse engineering.
Nobody said it wont take time or be a labor of love at least in the beginning. Put on your work dress and apron and play housewife...its called R&D ;D

Even do some rewinding for others to get a feel for the various designs.

I wish I had grabbed some of the gear when NH Transformer was liquidated when the owner died. He had a nice 4-5 person business doing mostly small runs and prototypes that the Magcaps, Merrimac Magnetics, and others didnt want to bother with.

Didn't mean to cause such a stir.

What decade did I come from?

 - The 50s when a TV cost 5 % of the annual income and today a 30" HDTV cost 1/2 weeks pay.


Souther ? A good quality British company  - typically British  - non inovative and only still in business because Audio Phools pay the inflated cost to make something that is out of date and non competitive with todays technology.

Hammond ( I know Hammond well and they are probably 85-90% as good as Souther and cost 1/3 the price Hammond is a transformer and sheet metal company - not a tube phoolery company - they make lots of good stuff and still sell the classic stuff more or less for nostalgia) I doubt that 2% of their business is tube iron.

The Hammond stuff does very well on the test bench but performs poorly in the Audiophool market because it doesn't cost enough.

And gee - Hammonds has very conservatively rated real copper wire and real silicone steel windings


Only problem that I have with an amplifier built with Hammond parts is that it has poor frequency response compared to a modern MOSFET amp that cost half as much - it sounds tubey - it sounds just like the Souter transformer amp - it has a colored frequency response exactly like the Marnatz and Mac amps of the late 50s and 60s that only the Doctors could afford.

If Hammond and Hoerborer can make a 50 watt output transformer that gets 50-18,000 Hz for $95  - I ain't paying $700 for one to get  5%  more frequecy response - especially when I can pay half the price for a MOSFET amp that I can use as a linear for the new Ham band.

But then - That's just me - Thats what decade that I am from - I have been Phooled more than once and built a whole lot of audio amps -  I like the tube sound but I hate the PHOOLERY and PHOOLERY  is rampant (in more than tube audio)

Pat
N4LTA

" The Hammond stuff does very well on the test bench but performs poorly in the Audiophool market because it doesn't cost enough. "


Well, marketing would help......   Grab one of yer units, get some expensive, high quality paint and paint the  'bells' to a mirror finish. A bit o spagetti fer the leads and triple the price. And get someone who can write a gud review. Making up a few new words would be oh tay.  Look to see if there's a old term that doesn't get used and apply it to the Premium line.


klc

Chrome plate the bells and jack the price $1000+

'  Chrome plate the bells '

Doesn't chrome cause Cancer !!!???


The powder coat, ferrite laden (which keeps the flux inside, thereby improving the texture), envyronmentally $afe,  ~green~, socially conscious is much better than the deadley chrome (which makes the sound waves reflect off of the inside, which makes them beyonc around).

klc

As any good businessman can tell you, especially a proprietress of a one woman show, you only want your help to be so bright ...  Any more and the "valued employee" will simply learn all from you and start their own business.

Not counting all the regulatory hurdles, the greatest challenge in small business is walking the fine line between keeping employees good enough to be competent while keeping the poorer ones from tipping the till.    This ranges from outright cash register theft to highly maskable embezzlement.

Hammond already makes a modulation transformer of sorts

(http://i620.photobucket.com/albums/tt286/n4lta/125GSE_B.jpg)

Rated at a very conservative 25 watts and 100 mA and weighs 6 pounds. Rated at 100hZ to 15kHz and will match 4 - 8 - 16 ohms from a solid state audio amp to 2500 -10,000 ohms.

If there was enough interest, Hammmond would probably put a tube push pull winding in place of the low impedance winding.


Sells for about $85 and it has all that expensive copper and steel that Souter gets $600 for


It really is a quality piece of iron. I will use one to modulate my 40 watt transmitter.

Pat
N4LTA

...as have generations to 'modulate' their 811's grids from a transistor PA or HI FI amplifier.  ;D

Here is the Edcor 25W single ended tube audio output transformer. This one is unusual in that it has a 600 ohm winding, and a teritiary tap for the screen grid.

http://www.edcorusa.com/p/475/cxse25-600-5k

So picture the Edcor in a Heising modulation scheme with the 600 ohm winding left unconnected. With the usual class A modulator, modulation is limited to about 80%, but a nice clean 80%. The transformer can take 200ma and not saturate at audio frequencies as low as 20HZ. So picture a B+ of 500V with a RF tube (6146) running 50 w DC input, or 100 ma plate current. Then for modulators use two EL-34's in parallel class A at 50 ma each. The total current will be 200 ma, RF input 50W, output about 35W carrier.

Now take that 600 ohm winding and phased properly, put it in series with the modulated B+. With a turns ratio of 2.9:1 the modulation capability will jump from around 80% to over 120%.

If it gets a little close to saturating, then just lessen the bass response to around 100 hz.

So here is another off the shelf modulation transformer for $83.50.  :-\


Edit: The concept above of a single ended class A modulator runs 50W DC input, and with 50% efficiency puts out 25W to 100% modulate the 6146 which is also running 50W DC input. The modulator runs the tubes at maximum plate dissipation, and might not be capable of providing the peak modulation required to achieve 120% on peaks.

To overcome this limitation we could run the modulator class A2 with a cathode follower drive. This boosts the peak power ability of class A, and increases efficiency. Distortion can remain low so long as the audio drive is low impedance. Go a step further and use a sliding modulator bias (like the Brooks circuit). The following link analyzes the Brooks circuit, and then the author designs a sliding bias circuit for a single ended class A audio amplifier, called "Turbo SE". This could back off the modulator DC input from 50 watts to maybe 35 watts, yet with the sliding bias achieve over 40 watts audio. The circuit as at the end of the following link:

http://www.tubecad.com/2007/12/blog0128.htm


Jim
WD5JKO

hmm, if you sat that hammond transformer up on some insulators, you might be able to pass a higher voltage through it, and for intermittent use, might handle twice their rated power. they have another single ended transformer that is rated at 75 watts. one could build a high power direct coupled solid state amp and feed it into the low impedence side of the transformer then hook the high impedence side to the RF final.

In the old days (70's), Hammond would custom wind transformers for small quantity orders ... or make 'specials' available to hams when referenced in magazine or Handbook construction articles. Admittedly, that was when Fred Hammond VE3HC was running the show and you could call and talk with him directly. Not sure what their current stance is on small quantity production runs but it may be worth asking ... especially if it is generally a viable product to add to their line. Might help to mention the VE3HC museum http://www.hammondmuseumofradio.org (http://www.hammondmuseumofradio.org) during the call with it's early broadcasting, AM heritage, etc. An e mail to the museum curator may get a good contact name within the company rather than a 'standard' sales person. Hammond has experience in 'high' voltage ... I have a couple custom wound plate transformers 3500 V @ 2 amps ... big, heavy and quite 'stiff' under load. Ratings appear to be quite conservative.

   

Today Edcor provides this service, "EDCOR charges a $40.00 design and setup fee for quantities less than 10 pieces. We have a large database of designs going back over 30 years and if we already have the transformer on file then the design and setup fee is waived."

http://www.edcorusa.com/c/10/custom

As I've already posted here (post 39 this thread), they have some off the shelf stuff that might work out well if we design around one of their single ended tube offerings.

For sure Hammond makes good stuff but they are not the only choice out there.

Jim
WD5JKO

Hammond is still a good company but they charge quite a bit for custom work - They won't do it for $40 but they have generated  some goog stuff for Hams and radio enthusiasts. They have introduced an output transformer for the Collins military radios and some nice interstage transformers.

If there is enough interest for a general purpose modulation transformer 50-75 watts or whatever - let me know and I'll see what they will do.

Pat
N4LTA

You know what, I come from the "audiophoolery" market, having worked for Cary, Levinson & others over the years. The nosense in that industry drove me out of it. So I agree most people who buy this stuff prebuilt are nutz paying the prices they pay.

That being said, two transformer dominate the area of DIY tube amplifier parts suppliers. In Europe, it's seems Lundahl is the preference. In the US, Hammond dominates the field. Yes ... Hammond. The reason they can supply transformers cheaply is in economies of scale. The bulk of its business is in large industrial transformers and sheet metal work, not just little transformers for audio. So they have lower cost of manufacturing.

Now what we are talking about is a transformer designed specifically as a mod transformer, with a primary for P-P higher impedance plate connection and the proper lamination types. The Hammond you refer to will work well, IF it's connected to solid state audio amplifier. However for a standard type modulator in the classic scheme it's a no go.

Now to put down Sowter, because they are "british" and to say that the British are not innovative is a demonstration of a lack of understanding of the history of transformer design (and electronics in general). G.A.V. Sowter was a pioneer in transformer and magnetics starting in the 1920's and published many papers on the subject from the 1930's through the 1990's. His work on moving coil technologies, magnetic properties of soft metals, work on various nickel-iron alloys, Mumetal use, and applications of high-permeability magnetic alloys are considered benchmarks for transformer design. His call sign is G20S and designed numerous modulation transformers over the years. Good ones!

Sowter is a bit more expensive for two primary reasons. The cost of manufacturing in Britain is even higher than it is here, and two the difference between the Euro and the US dollar.

And as far as keeping employees out of learning everything and starting there own business? Make them sign an agreement stating they cannot do that! It's perfectly legal and enforceable, and it works most times. I can't build and sell tube audio amplifiers of certain types for another 6 years, because of working for one manufacturer I previously designed for.

However, we are talking about finding real NEW mod transformers, and not using trannys' designed for other applications and changing or limiting our designs to suit that. Like being limited to solid state modulators, not being able to connect to the plates of a tube audio amplifier output without jumping through hoops.

$700 for a prototype mod tranny sounds like they don't want to do it at all. Hey ... don't get me wrong, I love Hammond.

J

  Loyalty to Hammond can get expensive..... ;D

Has anyone talked to these folks about a push pull modulation transformer? The single ended Edcor I brought up earlier in this thread can handle 200ma whereas the Hammond only 100ma into the primary.

Jim
WD5JKO

Denny found his dream niche when he started Cary.