OT question

[Randall]

Can an 8 ohm center tapped push pull OT be used to drive a single ended 4 ohm load?

[Jazz P Bass]

Short answer: No.

Long answer: http://music-electronics-forum.com/t25816/#post220890

and:

http://music-electronics-forum.com/t15200/#post121433

[cjenrick]

yes you can do it. will the core saturate? will it sound good when it saturates? this is best found out through experimentation. it might sound frickin awesome, depends on the size of the transformer, the number of primary turns and what tube you are using for the SE amp.

i ran a push-pull xfmr in a vibro champ and it was the most awesome harp amp i have ever heard.

push-pull transformers run unbalanced DC all the time. how much? depends on how well the tubes are matched. might be as high as 20 ma, so let's say you run a single 6V6GT at 30 ma, you only have 10 ma more unbal DC than the push pull circuit.

look at the core of your transformer. are there three laminations going one way and three going the other way? this is called lap 3. this lacing method will create a natural air gap which is larger than an output transformer which is laced 1 x 1, that is, one lam going one way and one going the other way. get out a mag glass. a 3 x 3 will saturate less then a 1 x 1 in an SE circuit.

can you use a single ended transformer for a push-pull circuit? that's what they do in the Tweed DeLuxe. some people e really like the sound of the Tweed DeLuxe.

[J M Fahey]

Short answer: no.
Could write pages saying exactly the same so why waste time?

[Gregg]

Mesa is doing it in many of their amps but it only looks so because it's not exactly class A.
Some time ago I had an Express 25/5 on my bench. Well, it's neither 25 nor 5. The class A power was around 1.5 Watts. I contacted them to ask if there was a problem with that and they said it was OK.

[J M Fahey]

No.
Besides, what does

single ended 4 ohm load?

mean?

Loads are not single ended, they are always symmetrical ... unless you wire a diode in series with speaker that is

[cjenrick]

Fender Vibro Champ has a 4 ohm load.

[cjenrick]

Fender Vibro Champ has a 4 ohm load.

as long as you do not exceed the maximum flux density for the core then you are alright.

B max for silicon is 18 KG. Non Grain barn roof is 21 KG.

compute AC and DC flux.

what is max RMS volts? for a SE amp with 300 on the plate it will be about 100 volts.

how many primary turns? worst case for DC would be around 2000 for the full primary. (the more turns the more amp-turns = more DC flux)

how much DC current? probably about 40 ma.

what is the cross sectional area of the core in cm^2? what is the MPL?

now just crunch the numbers and see how close to 18 KG you are.

measure the core dims, x y and z. we can then figure out which EI lam it is and finish the math.

in this case there is much less AC voltage swing with SE as opposed to P-P so you have more iron to handle DC.

[g1]

can you use a single ended transformer for a push-pull circuit? that's what they do in the Tweed DeLuxe.

How does that work? The schematic shows a center-tap in the primary of the OT. Single ended OT's don't have that.

[cjenrick]

they use a gapped core, so you would safe off the CT lead when using it for an SE amp.

Triad 108

kind of a "one size fits all" marketing approach from the 50's.

notice the I bar inside the u frame.

notice the weird sec wire soldered to the frame.

[Enzo]

can you use a single ended transformer for a push-pull circuit? that's what they do in the Tweed DeLuxe. some people e really like the sound of the Tweed DeLuxe.

Single ended means no center tap, which is impossible to use in a push pull amp. WHich means the Deluxe did not use one.

[Randall]

Man, tough room. I'll be here all week, try the veal!

[cjenrick]

"Man, tough room..."

welcome to the internet

Randall, if you give me the dimensions of the core of the transformer you want to use i can crunch some numbers and predict what it will sound like,


here is how you use a P-P xfmr in a SE circuit>

[dstrat]

here is how you use a P-P xfmr in a SE circuit>

[ATTACH=CONFIG]44419[/ATTACH]

I have thought about trying that before but never got around to it, have you tried to tie center tap to the screen for distributed load or UL?

[cjenrick]

that is a very cool idea!