Small SE Transformer Candidate: Visaton TR10.16 - Test data attached

SerpentRuss

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I was purchasing some parts from Mouser a few months back and looked through some of their signal transformers and spotted this. It was about $14 dollars so I went ahead and purchased one. Today when I was testing the two PP transformers that I placed in another post, I tested this one as well. I think it looks promising as a 2 to 3 watt transformer for small SE projects. Since the turns ratio between the .625 watt and 2.5 watt tap are doubled it think it might even work as a small PP transformer. I'll have to experiment with it.

I happened to have a Hammond 1750AX on hand as well. That transformer is normally used as a reverb driver for 8Ω tanks. The Hammond is rated at 3.5 watts and is wound for a reflected impedance of 7.5K. I've used the Hammond 1750AX in two 6CL6 SE projects.

The Visaton appears to be more substantial and is certainly more versatile. It has 5 primary taps and 3 secondary taps. The laminations on the Visaton are thicker than the Hammond and overall it's 100 grams heavier. From test results today it looks like this Visaton transformer could substitute for the Hammond and may have a bunch of other possible applications. It also seem to be made really well. I like that it has lugs instead of leads. Visaton is a German company, but I have no idea if this was wound in that country.

I realize the test data may be a bit cryptic. There is a section of data for each secondary tap that includes the turn ratios for the various primary taps that result when that secondary tap is used. Then the reflected Impedance for each Primary is calculated for various speaker loads attached to that secondary. In other words, the transformer's designation for each secondary tap (4,8, and 16Ω) only tell you where we'd wire the speaker, they don't dictate the speaker that we'd wire there. Clear as mud, right?

The yellow highlight in the 8 ohm speaker column shows a few combinations that might work using a standard 8 ohm load with an output tube like a 6CL6, 6AK6, 6AQ5, Parallel 12AU7/6AU7, EF80, etc.

I'll let you know when I use this transformer. It shouldn't be too far down the road.



Edit: Replaced data photo with a table with better headings
 

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2L man

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Thank You! I have just installed Visaton 100V transformer to my reactive Attenuator I am building.

Please test what winding ratios you get if you drive the AC to its primary?
 

SerpentRuss

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Thank You! I have just installed Visaton 100V transformer to my reactive Attenuator I am building.

Please test what winding ratios you get if you drive the AC to its primary?
Thanks,

Which Primary taps do you want to drive and which secondary taps do you want to measure. When I tested yesterday, it was more convenient to "back-flow" the test voltage.

Right now I have the 0.625 Watt hooked up with rectified, but unfiltered DC right from a bridge, testing to see how tolerant of DC current this transformer is. It would be relatively easy to use straight AC. I just spent about an hour listening to 120 Hz through an 8-inch, 16 ohm Celestion and I'm a bit foggy.
 

mountainhick

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@SerpentRuss If you wanted to use this as 16K:8ohm PP, would the taps be common to 0.625 with 1.25 as CT?

(Note: I see your actual measured values are not quite there at 13435 and 7162)
 
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SerpentRuss

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@SerpentRuss If you wanted to use this as 16K:8ohm PP, would the taps be common to 0.625 with 1.25 as CT?

(Note: I see your actual measured values are not quite there at 13435 and 7162)
I replied to this on the 6AK6-PP thread, but for clarity I'll put a blurb here. Impedance ratios are always calculated by turns ratios. In this case, we're calculating those from back-feeding a voltage from secondary to primary. I normally do it the other way, but for this transformer there were less wires to move by doing it backwards.

Those same impendence ratios in the chart are calculated referenced from the primary's winding common tap. When you're thinking about using this as push-pull, think about finding two taps that are approximately the same number of windings from each other and common. Then the common goes to one plate, the farthest tap goes to the other, and your B+ is landed on the center.

For this transformer the taps that work that way are the 0.625 (plate), 2.5 (B+), and common (plate) OR 1.25 (plate), 5 (B+), and common (plate). Use the far tap to calculate plate to plate impendence and then assume you have half of that on each side of the B+ terminal.

As I stated in the other thread, this is for grins and giggles projects. It may sound very good, it may not. Be prepared to do something else if it doesn't. I should have sound files on the 6AK6 project in a couple of weeks.
 
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2L man

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If you find power transformers which have two 110V/115V separate primarys they possibly can be used decent PP OT connecting primarys to series like OTs have. Also "international" PTs which have one primary coil, its american input might be exactly half between 0 and 230V, and might also make decent OT.
 

SerpentRuss

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If you find power transformers which have two 110V/115V separate primarys they possibly can be used decent PP OT connecting primarys to series like OTs have. Also "international" PTs which have one primary coil, its american input might be exactly half between 0 and 230V, and might also make decent OT.
Yes, some of the small voltage ANTEK toroidal transformers would work for budget PP OTs. The ANTEK 207, (7 volt, 25VA) looks like it would be a good EL84 or 6V6 push-pull candidate.

For a 16 ohm load on this project, an ANTEK 206 would work and I have one. The only reason I wouldn't use it would be size.
 

2L man

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Yes, some of the small voltage ANTEK toroidal transformers would work for budget PP OTs. The ANTEK 207, (7 volt, 25VA) looks like it would be a good EL84 or 6V6 push-pull candidate.

For a 16 ohm load on this project, an ANTEK 206 would work and I have one. The only reason I wouldn't use it would be size.
Yes, I just came to an article where 6SN7 was used to drive this $12 Antek toroid for 1W output. It has two equal primary coils so using 8 ohm speaker on paralleled 5V output impedance comes 17k. Naturally other output voltage transformers can be used as well and on Antek line there are many and many VA as well. Actual toroid OTs are reasonably priced too but not for low power low cost amps.

 

mountainhick

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Yes, I just came to an article where 6SN7 was used to drive this $12 Antek toroid for 1W output. It has two equal primary coils so using 8 ohm speaker on paralleled 5V output impedance comes 17k. Naturally other output voltage transformers can be used as well and on Antek line there are many and many VA as well. Actual toroid OTs are reasonably priced too but not for low power low cost amps.

Do torroidal TFs have different sound than ferrite core? 17K could be a pretty good ball park number for 6F4P PP.

IS the 6SN7 circuit you are referring to guitar or hifi?
 

mountainhick

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Yes, I just came to an article where 6SN7 was used to drive this $12 Antek toroid for 1W output. It has two equal primary coils so using 8 ohm speaker on paralleled 5V output impedance comes 17k. Naturally other output voltage transformers can be used as well and on Antek line there are many and many VA as well. Actual toroid OTs are reasonably priced too but not for low power low cost amps.


Can you show me the math on this @2L man ?

I've come up with this for 115V to 5V for 8 ohm:

primary 115V, secondary 5V, winding ratio 23, impedance ratio 529, secondary impedance 8 ohm, resulting primary impedance 4232ohm. So does parallel square the primary impedance?

EDIT: I think I figured it out! wiring 2 115V primary coils in series, primary voltage number is doubled at 230v. making winding ratio double at 46, impedance ratio is winding ratio squared for 2116, 16.9K at 8ohms!
 
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2L man

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Do torroidal TFs have different sound than ferrite core? 17K could be a pretty good ball park number for 6F4P PP.

IS the 6SN7 circuit you are referring to guitar or hifi?
I recall it was "flea HiFi" ;)

Found the thread which is 23 pages:


I have used three toroidal OTs which are designed as OT but I don't know what their cores are. I think they are based to iron? One is SE and two PP amps.

The sound what comes out of toroid OT has more clarity obviously because their high frequency range is higher.

I have test two toroid power transformers which have 0-115-230 primary or two 115V primary coils and they did sound just fine and have began building EL84 PP amp but put it away when other interests came.
 
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2L man

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Can you show me the math on this @2L man ?

I've come up with this for 115V to 5V for 8 ohm:

primary 115V, secondary 5V, winding ratio 23, impedance ratio 529, secondary impedance 8 ohm, resulting primary impedance 4232ohm. So does parallel square the primary impedance?

EDIT: I think I figured it out! wiring 2 115V primary coils in series, primary voltage number is doubled at 230v. making winding ratio double at 46, impedance ratio is winding ratio squared for 2116, 16.9K at 8ohms!
When you calculate winding ratio estimates you use full primary coil when amp uses them series like Push Pull amps use so for that it comes 230V:5V=46^2=2116 times speaker ohms.

In practice its no load output might be 5,5VAC or even close to 6V and true winding ratio comes different. Just connect primarys to series and input your Mains and measue output and that there is half the mains on CT against neutral and hot. If two primary coils came opposite phase there is no output voltage. This in case builder has marked wires wrong.

If you buy something from Antek I hope adding one of these won't increase postage too much because at only $12 it is cheap if it work as guitar amp OT.
 
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mountainhick

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When you calculate winding ratio estimates you use full primary coil when amp uses them series like Push Pull amps use so for that it comes 230V:5V=46^2=2116 times speaker ohms.

In practice its no load output might be 5,5VAC or even close to 6V and true winding ratio comes different. Just connect primarys to series and input your Mains and measue output and that there is half the mains on CT against neutral and hot. If two primary coils came opposite phase there is no output voltage. This in case builder has marked wires wrong.

If you buy something from Antek I hope adding one of these won't increase postage too much because at only $12 it is cheap if it work as guitar amp OT.
Thanks! Confirmation.

I've been reading more about toroids, sounds like they are unforgiving of imbalances between output tubes and saturate easily. I am not so sure I'll try this route, but yeah for $12, if it doesn't add shipping cost. (I'll be ordering a few PTs anyway).
 

mountainhick

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I recall it was "flea HiFi" ;)

Found the thread which is 23 pages:


I have used three toroidal OTs which are designed as OT but I don't know what their cores are. I think they are based to iron? One is SE and two PP amps.

The sound what comes out of toroid OT has more clarity obviously because their high frequency range is higher.

I have test two toroid power transformers which have 0-115-230 primary or two 115V primary coils and they did sound just fine and have began building EL84 PP amp but put it away when other interests came.
OK, thanks. The article discussed garter bias for the toroid imbalance issue... more study.
 

2L man

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OK, thanks. The article discussed garter bias for the toroid imbalance issue... more study.
To the other true toroid OT amp I made a bias circuit which has also balance adjust because I thought possible tube imbalance would cause problems. Then I was able to set biases to very high imbalance. I don't remember exactly but for 6V6GT about 60mA to other and about 15mA to other and I saw distortion increase on 100Hz quite a lot when as a reference when on balanced bias the output power was set to 10W. When I did drive lower power using same imbalance the 100Hz distortion did drop significantly. I think that together with imbalance and low frequency the OT core did saturate when high power was tried to produce.

Then when I did play guitar thru loudspeaker I was able to hear sound change but when imbalance was set to only about 10mA but it did still sound just good. This distortion increase happen on EI-core OTs too when tubes are much different. Then the next toroid OT amp I did build having typical cathode bias.

I think bias balance is only small part of operation and if tube pair is way too different, setting idle bias balanced using balance potentiometer help only partially because amplifying signal is much more dynamic.

I understand that for HiFi guys better balance, to avoid core saturation, is much more important when they need less than 20Hz.

Garter Baumlain bias is very interesting but I have made only one test circuit which I did not measure enough to say is it useful.

On that PP build (where I am going to use power PT as OT and put hold) I chose EL84 because their cathode bias voltage loss is lower. I also use PT which has plenty on spare voltage for double the cathode resistor voltage losses if I must use Garter bias?
 
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