I recently emailed EDCOR Electronics Corp and asked for more technical details on their Audio Output Transformers.
The technical information I was seeking was for their product >
https://www.edcorusa.com/cxpp100-8-5k
Hello;
I'm interested in this model transformer, but a few electrical specs you don't have listed, I am after are: >
Total Primary Inductance for this specific transformer;
the DC resistance per each half of the primary; and leakage inductance of the windings;
plus at what frequency is the maximum power measured at ?
What is the maximum B+ that can be safely applied for continuous operation ?
Maximum plate current that can be applied ?
Thanking you for your time;
-----------------------------------
The reply I got was >
I am sorry we do not keep any data on the inductance or DC resistance of the CXPP series.
We design our transformers to product the rated wattage and the lowest rated frequency listed in the frequency response specs. The maximum voltage is the brake down voltage, 500V.
Thank you,
Brian Weston
------------------------------
As a result it does not give me any confidence in using this product, since for a start, I want to run 807 tubes which need at least 500-600 volt B+ rails.
It baffles me as to why such data needs to be kept "secret" or not recorded at all for the benefit of the end user. That to me is sign of poor engineering practice. Up until now, I had a high opinion of Edcora - but now I'm not so sure. It also gives me reason to seriously doubt other users who have actually tried them- as to whether their running these transformers to spec.
More expensive brand transformers such as Tango, Hashimoto etc, do have such details recorded for the end user.
So, how does one get around such without buying a unit and testing your self ? - ( only to find you pay for it, ship it halfway around the world to Australia, pay customs import duties and exchange rates on top of the existing costs, and then find the end product may be unsuitable ).
Has anyone else had similar experiences ?
The technical information I was seeking was for their product >
https://www.edcorusa.com/cxpp100-8-5k
Hello;
I'm interested in this model transformer, but a few electrical specs you don't have listed, I am after are: >
Total Primary Inductance for this specific transformer;
the DC resistance per each half of the primary; and leakage inductance of the windings;
plus at what frequency is the maximum power measured at ?
What is the maximum B+ that can be safely applied for continuous operation ?
Maximum plate current that can be applied ?
Thanking you for your time;
-----------------------------------
The reply I got was >
I am sorry we do not keep any data on the inductance or DC resistance of the CXPP series.
We design our transformers to product the rated wattage and the lowest rated frequency listed in the frequency response specs. The maximum voltage is the brake down voltage, 500V.
Thank you,
Brian Weston
------------------------------
As a result it does not give me any confidence in using this product, since for a start, I want to run 807 tubes which need at least 500-600 volt B+ rails.
It baffles me as to why such data needs to be kept "secret" or not recorded at all for the benefit of the end user. That to me is sign of poor engineering practice. Up until now, I had a high opinion of Edcora - but now I'm not so sure. It also gives me reason to seriously doubt other users who have actually tried them- as to whether their running these transformers to spec.
More expensive brand transformers such as Tango, Hashimoto etc, do have such details recorded for the end user.
So, how does one get around such without buying a unit and testing your self ? - ( only to find you pay for it, ship it halfway around the world to Australia, pay customs import duties and exchange rates on top of the existing costs, and then find the end product may be unsuitable ).
Has anyone else had similar experiences ?
Yes, I called last week asking similar questions about one of their transformers.
I received a similar answer from Phyllis, and to paraphrase, 'no one has ever asked me that before...we don't have that kind of data...why would you even need it?'
I received a similar answer from Phyllis, and to paraphrase, 'no one has ever asked me that before...we don't have that kind of data...why would you even need it?'
That is a bit odd... as Edcor do list primary resistance and maximum rated DC current for the primary of their single-ended iron. Still, they are budget units along the same lines as Hammond albeit better quality than Hammond.
I'm not too sure about the reply from them, as most iron usually has a insulation rating of 1.5KV or higher... and the fact the he used "brake down voltage" vs "breakdown voltage" pretty much disqualifies him from authoring any data sheets.
I've used their power transformers, filter chokes and SE OPTs and I can recommend the power/chokes as good value and decent fit/finish (if you like the blue color). Their SE OPTs are fair at best, but then again... you're talking $85 for a 25-watt rated unit ($170US per pair) vs $1200 for a pair Hashimoto 30-watt SE OPTs. Not exactly a reasonable comparison. Still, I don't recall seeing leakage inductance specs listed for any OPT over the decades.
You might want to consider Transcendar OPTs. They have a fuller set of meaningful specifications and aren't priced too badly.
Push-Pull Transformers - Transcendar Audio Transformers
Regards, KM
I'm not too sure about the reply from them, as most iron usually has a insulation rating of 1.5KV or higher... and the fact the he used "brake down voltage" vs "breakdown voltage" pretty much disqualifies him from authoring any data sheets.
I've used their power transformers, filter chokes and SE OPTs and I can recommend the power/chokes as good value and decent fit/finish (if you like the blue color). Their SE OPTs are fair at best, but then again... you're talking $85 for a 25-watt rated unit ($170US per pair) vs $1200 for a pair Hashimoto 30-watt SE OPTs. Not exactly a reasonable comparison. Still, I don't recall seeing leakage inductance specs listed for any OPT over the decades.
You might want to consider Transcendar OPTs. They have a fuller set of meaningful specifications and aren't priced too badly.
Push-Pull Transformers - Transcendar Audio Transformers
Regards, KM
I've not had significant problems with any Edcor filament or plate power transformer, whether standard or custom, but have not tried an output transformer.
What I can say is that their custom power transformers handily meet my specifications, exhibit really good voltage regulation over no load to rated full load, and run very cool and are also relatively quiet. (Quieter than a lot of the competition by a pretty wide margin actually.)
I learned a long time ago to just ask for what I want and not ask questions after a few heated exchanges with Brian. With the exception of electrostatic shielding I have gotten the level of performance requested and at a very, very reasonable price.
I will continue to do business with them, and will probably try their middle of the range PP OPT for a PP 6BQ5 stereo amp I plan to design and build to satisfy some nostalgic craving I have.. LOL
I was quite pleased with a set of Transcendar SE output transformers I purchased on eBay about six or so years ago. So I think that is another suggestion.
What I can say is that their custom power transformers handily meet my specifications, exhibit really good voltage regulation over no load to rated full load, and run very cool and are also relatively quiet. (Quieter than a lot of the competition by a pretty wide margin actually.)
I learned a long time ago to just ask for what I want and not ask questions after a few heated exchanges with Brian. With the exception of electrostatic shielding I have gotten the level of performance requested and at a very, very reasonable price.
I will continue to do business with them, and will probably try their middle of the range PP OPT for a PP 6BQ5 stereo amp I plan to design and build to satisfy some nostalgic craving I have.. LOL
I was quite pleased with a set of Transcendar SE output transformers I purchased on eBay about six or so years ago. So I think that is another suggestion.
Ditto with kevinkr on their power transformers... they are quite good, especially considering the price. I do wish Edcor had a wider range of chokes available however.... pretty slim compared to the Hammond catalog.
I have a pair of (Edcor) 25-watt SE OPTs... one has a pretty big step difference in the core alignment while the other is fine, so QC could be better. Stiil, one can consider it a bargain for that much copper and iron at a weight/dollar figure. You also have to wait a fairly long time to get them and their shipping is pretty high.
I also bought a SE pair of Transcendar OPTs on Ebay some years ago, they are very good performers at the price. I also just ordered a pair of Transcendar 15-watt SE OPTs for a 3C24 project. Gerry quoted 2 weeks but they came in less than 10 days and only $12 shipping USPS and extremely well packed. I am using Edcor for the Power and Choke units... and still waiting for them.
Regards, KM
I have a pair of (Edcor) 25-watt SE OPTs... one has a pretty big step difference in the core alignment while the other is fine, so QC could be better. Stiil, one can consider it a bargain for that much copper and iron at a weight/dollar figure. You also have to wait a fairly long time to get them and their shipping is pretty high.
I also bought a SE pair of Transcendar OPTs on Ebay some years ago, they are very good performers at the price. I also just ordered a pair of Transcendar 15-watt SE OPTs for a 3C24 project. Gerry quoted 2 weeks but they came in less than 10 days and only $12 shipping USPS and extremely well packed. I am using Edcor for the Power and Choke units... and still waiting for them.
Regards, KM
Thanks all for your comments.
I have no issue with Edcor's price, nor even their turn around time - as I don't expect some transformers to be "Off The Shelf" either. In Edcor's favour you can now buy - Bobbins Laminations, Bell covers and Wire if your keen enough to wind your own spec output - which I may do yet - then I can only blame myself if the damn thing don't work.
As Edcor's price is so good - it's not worth reverse engineering to copy their design, if that is their fear, by not giving out the specs - but it certainly would help customer relations if such data was made readily available.
As we all know - when it comes to choosing an Output Transformer - Plate Load Impedance, Power Handling Capability and Frequency Response are not the only considerations to take into consideration.
As an example - a plate voltage swing on a 500 volt B+ rail would typically be with an open circuit secondary load, as high as 1000 volts Peak-peak maybe a bit more. If the insulation is only rated for 500 volts, then any flash over of inter-winding insulation is guaranteed.
To be safe, you need at least a 10-20% safety margin built in. So with a 500 volt breakdown rating in the transformer windings, the maximum B+ I would even consider safely using would be around 200 Volts DC. Few tubes run on those very low Dc voltages. ( Yeah maybe a 6AS7 or some smaller Audio Tubes, but not Transmitter Tubes ).
To get around this issue, you would generally have to electrically suspend the transformer on an insulator plate, and/or wire the steel core to the B+ rail instead of the chassis. This would require another protective cover over the existing transformer metal core, hence creating a lot of extra modification to get around a very simple problem of poor interwinding insulation.
Many older transformers from places like Stancor & UTC, etc, had at least a 1.5-2kv breakdown rating between windings. This would allow for B+ rails as high as 650 - 900 volts DC to be safely used. And so it goes !
I have no issue with Edcor's price, nor even their turn around time - as I don't expect some transformers to be "Off The Shelf" either. In Edcor's favour you can now buy - Bobbins Laminations, Bell covers and Wire if your keen enough to wind your own spec output - which I may do yet - then I can only blame myself if the damn thing don't work.
As Edcor's price is so good - it's not worth reverse engineering to copy their design, if that is their fear, by not giving out the specs - but it certainly would help customer relations if such data was made readily available.
As we all know - when it comes to choosing an Output Transformer - Plate Load Impedance, Power Handling Capability and Frequency Response are not the only considerations to take into consideration.
As an example - a plate voltage swing on a 500 volt B+ rail would typically be with an open circuit secondary load, as high as 1000 volts Peak-peak maybe a bit more. If the insulation is only rated for 500 volts, then any flash over of inter-winding insulation is guaranteed.
To be safe, you need at least a 10-20% safety margin built in. So with a 500 volt breakdown rating in the transformer windings, the maximum B+ I would even consider safely using would be around 200 Volts DC. Few tubes run on those very low Dc voltages. ( Yeah maybe a 6AS7 or some smaller Audio Tubes, but not Transmitter Tubes ).
To get around this issue, you would generally have to electrically suspend the transformer on an insulator plate, and/or wire the steel core to the B+ rail instead of the chassis. This would require another protective cover over the existing transformer metal core, hence creating a lot of extra modification to get around a very simple problem of poor interwinding insulation.
Many older transformers from places like Stancor & UTC, etc, had at least a 1.5-2kv breakdown rating between windings. This would allow for B+ rails as high as 650 - 900 volts DC to be safely used. And so it goes !
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My experience with Edcor has mainly been positive. I've used two of their single-ended output transformers (CXSE and XSE series). They've worked just fine. For $80/each I think you get your money's worth. But yeah... They do suffer from Poor Datasheet Syndrome.
~Tom
~Tom
I read some where that OT Hammond keeps more than 1000 v.
I have 25 W XSE and 20 W Hammond 125FSE.....I tried SE 300B with both, EDCOR keeps band in LF 60-200 HZ, Hammond 20-200 Hz with the same form of amplitude with current 90 ma.. IMO, /I'm not agree with spec. 150-15000/. Second OT /with recommended current 90 ma/ works very good with 120-130 ma with GU50. I prefer 125FSE.
I have 25 W XSE and 20 W Hammond 125FSE.....I tried SE 300B with both, EDCOR keeps band in LF 60-200 HZ, Hammond 20-200 Hz with the same form of amplitude with current 90 ma.. IMO, /I'm not agree with spec. 150-15000/. Second OT /with recommended current 90 ma/ works very good with 120-130 ma with GU50. I prefer 125FSE.
I have had Edcor make me a number of custom 800VCT and 700V (no CT) transformers for power supplies in my amps and pre-amps and with one exception have not had any problems with them, I'm not sure where that 500V rating comes from, probably Brian being ultra conservative, I believe that is an RMS rating FWIW and obviously does not apply to the higher voltage transformers I mentioned.
I am sure they will make custom value chokes (non swinging) if you ask them to. I have found the limited selection adequate to my needs, Hammond can also be a good source for chokes.
I am sure they will make custom value chokes (non swinging) if you ask them to. I have found the limited selection adequate to my needs, Hammond can also be a good source for chokes.
I once asked for the Hi-Pot voltage and I believe the answer was the transformers were tested to 1KV.
Voltage ratings are difficult. For one thing, there are few if any reliable ways to determine what voltage will allow the unit to resist arcing, corona, leakage, etc. for its lifetime. For another, the traditional standards simply don't have enough science or data to justify them. The same goes for design practices, made worse by the lack of published design rules in general. It's an old art that has not been much updated for the last 50 years, outside the commercial power line units.
The traditional test is the hipot test, which determines the voltage below which the windings will be safe for a few seconds or minutes. I have heard more than one formula, but typically it was said that you need a hipot at 1000v plus 1-2 times the working voltage - i.e. a 500v rating calls for a 1500-2000v hipot test.
Between the inherent uncertainties of measurements and the current atmosphere of lawsuit paranoia, I think few companies are willing to provide ratings in excess of 500v, whether or not certain design practices are followed.
The traditional test is the hipot test, which determines the voltage below which the windings will be safe for a few seconds or minutes. I have heard more than one formula, but typically it was said that you need a hipot at 1000v plus 1-2 times the working voltage - i.e. a 500v rating calls for a 1500-2000v hipot test.
Between the inherent uncertainties of measurements and the current atmosphere of lawsuit paranoia, I think few companies are willing to provide ratings in excess of 500v, whether or not certain design practices are followed.
I published a version of Pete Millett's Engineers Amp that puts out 125 WPC and runs a plate supply voltage in the range of 600 to 650 volts depending on choice of power transformers. At least a dozen people built this design, probably more, and most of us used CXPP100-8-3.3K OPT's. There have been no failures that I know of in the 3 years that these amps have been running, and I play guitar through mine.
A second set with the multi impedance secondary will be going into a 125 WPC rack mount PA amplifier running 650 volts as soon as I have time to build it. I have seen 200 W RMS flow through these if constrained to operation above 70 Hz. There will be a 300 WPC Class D chip amp sub amp.
I have used the CXSE25-8-5K in SE 300B and 307A amplifiers. I have also used Transcendars, Electra Prints, One Electrons, and Hammond SEA1628's in the same design.
The Hammond and Edcor are in the same LARGE (about 10 pound) size but the Hammond has so much HF rolloff and phase shift that they still sit on the shelf after 8 years. The Edcors are the best deal in an OPT of this size, and does sound quite nice when driven by a low impedance source like a 300B.
All the others are roughly 5 pounds. The Electra Print sounds the best to most listeners, but a couple people rated it worst in my blind, but somewhat uncontrolled tests. The older Transcendars that I had were second best, and the One Electron was good but the least efficient due to it's high DCR.
I spent a bit of time digging through my Radiotron Handbook on transformers today. As expected, tons of detailed information of inductance, leakage inductance, DC resistance, etc., but nothing on insulation resistance. In fact, I couldn't anything even remotely related to hi-pot testing, etc. for anything.
I did however find a handy chart on insulating materials. As most manufacturers have used paper (between windings) over the decades, it has a rating of 1250 volts per mil. Nylon was 340 volts per mil.
Getting back to Edcor, they do show some specs on the bobbins they sell... which are glass-filled nylon and they list a rated insulation of 540 volts per mil, which is believable. Considering the bobbins are spec'd at an 1/8-inch thick, I have no doubt they won't ever arc from a winding to the core via the bobbin.
It is a bit odd that Edcor will sell you virtually all of the parts to build your own iron (cores, bobbins, magnet and lead wires plus endbells) but don't sell the insulating paper or whatever they use. I guess another way to get info is to ask them what they use for insulating between the windings and how thick it is.
Looking at their 100-watt PP iron, they list a 10K primary available. Do the math listed earlier (P=E2/R) and you'll end up with about 1000 VRMS on the primary at full power. As a result, I wouldn't be worried about breakdown insulation, but it would still be nice to get specs for rated current, inductance and DC resistance. I have to believe they know these specs... how could they not?
Regards, KM
I did however find a handy chart on insulating materials. As most manufacturers have used paper (between windings) over the decades, it has a rating of 1250 volts per mil. Nylon was 340 volts per mil.
Getting back to Edcor, they do show some specs on the bobbins they sell... which are glass-filled nylon and they list a rated insulation of 540 volts per mil, which is believable. Considering the bobbins are spec'd at an 1/8-inch thick, I have no doubt they won't ever arc from a winding to the core via the bobbin.
It is a bit odd that Edcor will sell you virtually all of the parts to build your own iron (cores, bobbins, magnet and lead wires plus endbells) but don't sell the insulating paper or whatever they use. I guess another way to get info is to ask them what they use for insulating between the windings and how thick it is.
Looking at their 100-watt PP iron, they list a 10K primary available. Do the math listed earlier (P=E2/R) and you'll end up with about 1000 VRMS on the primary at full power. As a result, I wouldn't be worried about breakdown insulation, but it would still be nice to get specs for rated current, inductance and DC resistance. I have to believe they know these specs... how could they not?
Regards, KM
Hi Kimbal, your fellow aussie Patrick Turner has traffos in his inventory, there could be one that fits your needs...for-sale-2-output-transformers
I quite agree that Brian is not great in the field of grammar. I also think he miss wrote about the breakdown voltage. The magnet wire used by EDCOR has an insulation breakdown voltage of 1000V, between windings would be 2000V. As for the DC resistance and leakage inductance, because it is not used in the design or testing of the CXPP series, it is not kept on file. Most, which ask for it, are using it just for Spices models. EDCOR designs all of their audio transformers around the lowest frequency. Meaning that the rated wattage is at the lowest frequency listed in the frequency response spec.
I agree the delivery from EDCOR is way too long. They do not keep any of their transformers in stock, except from some of the smaller matching transformer and S2M units. This is to try to keep the cost down.
I also agree they could use a little more information of their website about the specs of some of the transformers.
Me, personally, when I call in I like talking to the girl with the British accent. ;-)
P.S. I am very sorry for the bad information.
I agree the delivery from EDCOR is way too long. They do not keep any of their transformers in stock, except from some of the smaller matching transformer and S2M units. This is to try to keep the cost down.
I also agree they could use a little more information of their website about the specs of some of the transformers.
Me, personally, when I call in I like talking to the girl with the British accent. ;-)
P.S. I am very sorry for the bad information.
Its interesting,
That some transformer manufacturers are creating paper insulated designs,
I'm surprised Edcor hasn't looked at this. Perhaps its not cost effective.
Regards
M. Gregg
That some transformer manufacturers are creating paper insulated designs,
I'm surprised Edcor hasn't looked at this. Perhaps its not cost effective.
Regards
M. Gregg
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As for the insulation of EDCOR's transformers, the magnet wire is a heavy coated wire. If you look at the wire specs listed on the magnet wire they sell on their website, you can see the type and rating of the magnet wire they use. On some transformers, a black tape is used to isolate the windings. We are looking at putting some of the tape on our website, but just have not had the time yet. Kraft paper is a good choice between windings, but it can add a lot of build to the winding. The newer tapes on the market are thinner and can handle a lot of voltage. EDCOR is looking into adding everything you would need to build transformers. It will just take sometime. We are even looking into maybe adding a winding machine and lamination stackers to the website.
It's good to see Edcor chiming in. Very nice.
FYI: The small-signal parameters builders ask for can be measured using an LCR meter (or impedance analyzer if you have the budget). This would allow you to publish Spice models for the transformers. The max primary current should be possible to calculate from the core area, air gap (if applicable), and max. magnetic field in the core. There's gotta be someone in the company who's performed those calculations...
I really enjoy the CXSE transformers and recommend them to builders of my circuits who want good quality for a reasonable price. You have a good product. I encourage you to back it up with a good data sheet as well. Contact me privately if you need help with this.
~Tom
FYI: The small-signal parameters builders ask for can be measured using an LCR meter (or impedance analyzer if you have the budget). This would allow you to publish Spice models for the transformers. The max primary current should be possible to calculate from the core area, air gap (if applicable), and max. magnetic field in the core. There's gotta be someone in the company who's performed those calculations...
I really enjoy the CXSE transformers and recommend them to builders of my circuits who want good quality for a reasonable price. You have a good product. I encourage you to back it up with a good data sheet as well. Contact me privately if you need help with this.
~Tom
Just about every transformer manufacturer seems to be reluctant to publish detailed specifications, especially when it comes to microphone and output transformers. I eventually invested in a decent inductance meter and started to collect data o a number of popular audio transformers. Initially this contained only data from transformers I own but it soon got added to by the tests of others. You can read the info here:
http://www.ianbell.ukfsn.org/EzTubeMixer/docs/EzTubeMixer/Iron/TransformerInductance.pdf
If you have any data for transformers not listed I would be happy to include it.
Cheers
Ian
http://www.ianbell.ukfsn.org/EzTubeMixer/docs/EzTubeMixer/Iron/TransformerInductance.pdf
If you have any data for transformers not listed I would be happy to include it.
Cheers
Ian
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