rafafredd
Well-known member
I tghink it was NYDave that posted poor results when trying to use those transformers with DC running throught the windings.
I do like EDCOR, as $10 dollas trafo, but look, some of their specs are bogus...
Western Electric 417A Tube Preamp
- Thread starter CJ
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Help Support GroupDIY Audio Forum:
I tghink it was NYDave that posted poor results when trying to use those transformers with DC running throught the windings.
I do like EDCOR, as $10 dollas trafo, but look, some of their specs are bogus...
> Neve type output core
It would be brutal, but... that 1:1.4 Neve output used with a 2N3055 transistor? Turn it around, work it as 1.4:1, 1K2 input to 600 output. Work the 417 tube at high plate current (30mA?) and full power (say 140V B+ or 4,2 Watts Pd). Loaded, the gain is around 20, times 1.4:1 is 14 (23dB). Max output is 14V peak or 10Vrms, +23dBm. UNloaded, the output voltage will soar 6dB, and the distortion is very much a function of the iron.
It would be brutal, but... that 1:1.4 Neve output used with a 2N3055 transistor? Turn it around, work it as 1.4:1, 1K2 input to 600 output. Work the 417 tube at high plate current (30mA?) and full power (say 140V B+ or 4,2 Watts Pd). Loaded, the gain is around 20, times 1.4:1 is 14 (23dB). Max output is 14V peak or 10Vrms, +23dBm. UNloaded, the output voltage will soar 6dB, and the distortion is very much a function of the iron.
NewYorkDave
Well-known member
Rafa, it was the XSM series I tested, and they did indeed do poorly with DC in the primary--contrary to what was implied by the spec on the webpage. However, the XSE series state unambiguously that they're gapped for single-ended use, so presumably the results would be better. But there's only one way to find out!
rafafredd
Well-known member
OK, so we need to know if they would make a XSE with a 600 Z secondary for this preamp...
Anyone has good contact with them?
Anyone has good contact with them?
tk@halmi
Well-known member
[quote author="rafafredd"]I tghink it was NYDave that posted poor results when trying to use those transformers with DC running throught the windings.
...
I do like EDCOR, as $10 dollas trafo, but look, some of their specs are bogus...[/quote]
Which of their specs are bogus? Granted, they are often missing information that may help decide about their suitablility for a particular application. However, we are often aroused by wishful thinking. There is probably no cheap way to make a single ended plate transformer without gapping, or keeping it smaller than a car battery. Nowhere does the XSM spec states that they are suitable for single ended operation. When they are the spec mentions gapping.
...
I do like EDCOR, as $10 dollas trafo, but look, some of their specs are bogus...[/quote]
Which of their specs are bogus? Granted, they are often missing information that may help decide about their suitablility for a particular application. However, we are often aroused by wishful thinking. There is probably no cheap way to make a single ended plate transformer without gapping, or keeping it smaller than a car battery. Nowhere does the XSM spec states that they are suitable for single ended operation. When they are the spec mentions gapping.
Yes, the core size will need to go up quite a bit with the dc current.
Ten bucks or no, you need the iron with a SE type output.
Even the big Neve core was barely enough to avoid saturation with this circuit.
Ten bucks or no, you need the iron with a SE type output.
Even the big Neve core was barely enough to avoid saturation with this circuit.
NewYorkDave
Well-known member
[quote author="tk@halmi"]Nowhere does the XSM spec states that they are suitable for single ended operation. [/quote]
The XSM spec states:
This implies that direct current through the primary is acceptable. But such is not the case.
Also, they call these "tube interstage matching transformers" and historically, interstage transformers have been designed for direct coupling to a plate.
I like Edcor as much as anybody here--and you might recall that I was one of the first people on this board to promote them--but I find their published specs to be very incomplete. Luckily, they're so inexpensive that "buy and try" is usually a feasible option.
The XSM spec states:
This implies that direct current through the primary is acceptable. But such is not the case.
Also, they call these "tube interstage matching transformers" and historically, interstage transformers have been designed for direct coupling to a plate.
I like Edcor as much as anybody here--and you might recall that I was one of the first people on this board to promote them--but I find their published specs to be very incomplete. Luckily, they're so inexpensive that "buy and try" is usually a feasible option.
A #2 large combo at J-Box is about six bucks.
So how much better can the transformer be compared to a cheeseburger?
They are selling these things in hopes that one of their products will somehow take off, selling zillions at a time, so that they can realize a profit somewhere down the road. So it's an investment in the future on their part. Sooner or later these people get smart and quit doing this when they realize it is a dead end, so get em while their hot.
It costs us 75 dollars just to process a purchase order around here, so....
Sales, accounting, production, shipping, lots of paperwork to get something out da door.
So how much better can the transformer be compared to a cheeseburger?
They are selling these things in hopes that one of their products will somehow take off, selling zillions at a time, so that they can realize a profit somewhere down the road. So it's an investment in the future on their part. Sooner or later these people get smart and quit doing this when they realize it is a dead end, so get em while their hot.
It costs us 75 dollars just to process a purchase order around here, so....
Sales, accounting, production, shipping, lots of paperwork to get something out da door.
tk@halmi
Well-known member
[quote author="NewYorkDave"]...they call these "tube interstage matching transformers" and historically, interstage transformers have been designed for direct coupling to a plate. [/quote]
OK, I see how that can be misleading.
OK, I see how that can be misleading.
Svart
Well-known member
when i called edcor a lady answered the phone and asked me what I wanted.. she turned around and asked someone in the background if they could wind what I wanted.
that tells me a couple of things.. one, that there aren't that many folks working there, two, that there is likely only one knowledgable person there, and three, that it's likely a small place with automated winders that are probably on autopilot.
doubt they spend 75$ on an order, likely that the person who answers the phone and the questions is probably an owner.
that tells me a couple of things.. one, that there aren't that many folks working there, two, that there is likely only one knowledgable person there, and three, that it's likely a small place with automated winders that are probably on autopilot.
doubt they spend 75$ on an order, likely that the person who answers the phone and the questions is probably an owner.
tk@halmi
Well-known member
[quote author="CJ"]It costs us 75 dollars just to process a purchase order around here, so....
Sales, accounting, production, shipping, lots of paperwork to get something out da door.[/quote]
That is the Corporate Mantra: lots of overhead and lots of paperwork. The Edcor model seems to be really simple. They use a single core type M6, use no fancy wires, good automation to speed up production. Having a variaty standard products helps keep the operation steady. They have been in business for over 30 years. There is something to learn from. :thumb:
Sales, accounting, production, shipping, lots of paperwork to get something out da door.[/quote]
That is the Corporate Mantra: lots of overhead and lots of paperwork. The Edcor model seems to be really simple. They use a single core type M6, use no fancy wires, good automation to speed up production. Having a variaty standard products helps keep the operation steady. They have been in business for over 30 years. There is something to learn from. :thumb:
Svart
Well-known member
they've likely honed it down pretty good.
CJ: I'd like to think about a nice passive EQ with a couple of these 417s on the output.. whatchu think?
CJ: I'd like to think about a nice passive EQ with a couple of these 417s on the output.. whatchu think?
bcarso
Well-known member
The Word of the Day:
Inselbildung
Inselbildung
> Inselbildung
That, and Temperature, explain why thermionic transconductance for current never reaches transistor levels.
Work your way to pg 166 (pg 18 in the PDF).
The main problem is that you can't get the grid close enough to get good leverage on the electrons, not with (1965-)producable stuctures. So the Gm varies roughly as square-root of current, and is low.
If you get the grid to the potential minimum, and avoid Inselbildung, eq 5.2-17 says 11,600/T Mhos/Amp. Taking T as 1,160 degrees (a bit hot), we get 10 Mho per Amp or 10 mMho at 1mA or 100 ohms or 100 milliVolts. This is a bit more than three times higher than a BJT working at 1/3rd the temperature.
So yes, a tube could be as good Gm/I as a BJT, if we could put the grid very darn close, without Inselbildung or stray grid emission, and find a good room-temp emitter.
It is interesting to me that it seems to have taken over 30 years to derive this result for the thermionic device, and Shockley got it for the BJT in less than 10 years.
That, and Temperature, explain why thermionic transconductance for current never reaches transistor levels.
Work your way to pg 166 (pg 18 in the PDF).
The main problem is that you can't get the grid close enough to get good leverage on the electrons, not with (1965-)producable stuctures. So the Gm varies roughly as square-root of current, and is low.
If you get the grid to the potential minimum, and avoid Inselbildung, eq 5.2-17 says 11,600/T Mhos/Amp. Taking T as 1,160 degrees (a bit hot), we get 10 Mho per Amp or 10 mMho at 1mA or 100 ohms or 100 milliVolts. This is a bit more than three times higher than a BJT working at 1/3rd the temperature.
So yes, a tube could be as good Gm/I as a BJT, if we could put the grid very darn close, without Inselbildung or stray grid emission, and find a good room-temp emitter.
It is interesting to me that it seems to have taken over 30 years to derive this result for the thermionic device, and Shockley got it for the BJT in less than 10 years.
Someone who knows tubes please look at 12GN7 and 12HG7 (TheTubeStore calls them equivalent and charges $10 each), and see if you agree that, triode-wired, working around 30mA, it gives Mu about 45 and Rp about 1K2.
This is especially pointful considering folks are putting big sounds into two triodes (albeit in one bottle) and getting too-hot levels.
Pete's page on high-Gm tubes is also relevant. 7788/E810F is spiffy, though it, (like 5842/417) costs $30 at TheTubeStore.
This is especially pointful considering folks are putting big sounds into two triodes (albeit in one bottle) and getting too-hot levels.
Pete's page on high-Gm tubes is also relevant. 7788/E810F is spiffy, though it, (like 5842/417) costs $30 at TheTubeStore.
skipwave
Well-known member
Those do look interesting (simple one-page html datasheet). They're only $5.60 at tubesandmore.com.
I haven't had that issue with my one-bottles, but I used a little more step down in the op tranny than was recommended. And I've only used it on acoustic guitar and drum room, so far.
I haven't had that issue with my one-bottles, but I used a little more step down in the op tranny than was recommended. And I've only used it on acoustic guitar and drum room, so far.
There is a "triode version" of the 7788 that you could use. It is the Russian 6C45pi or 6S45P to those of use who can't field Cyrillic. It's a single triode with very similar specs to the 7788 triode connected. They aren't too expensive and work well.
I have more experience with the 417A/5842 than I would like to admit. There are gremlins lurking in its application. They tend to become noisy after 6 months or so of continuous use, and turning the power off and on seems to expedite bad behavior, even if the HV supply is delayed to allow filament warm-up. I was never able to solve the problem and abandoned the tube for triode-connected 7788s, which behave beautifully.
I have more experience with the 417A/5842 than I would like to admit. There are gremlins lurking in its application. They tend to become noisy after 6 months or so of continuous use, and turning the power off and on seems to expedite bad behavior, even if the HV supply is delayed to allow filament warm-up. I was never able to solve the problem and abandoned the tube for triode-connected 7788s, which behave beautifully.
rafafredd
Well-known member
If it really does what it claims, then we´ve found it, and for a very good price.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5863213361&fromMakeTrack=true
It seems that this guys winds the transformers, so it could be a nice source, if we support it. One would have to buy and test it, to make sure it really stands.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5863213361&fromMakeTrack=true
It seems that this guys winds the transformers, so it could be a nice source, if we support it. One would have to buy and test it, to make sure it really stands.
Svart
Well-known member
i had 15k:600 wound by edcor, they work fine and sound pretty good to me. I'd like to compare them to something else though
