KT88SE, turning OPT

[mayky]

I bild a KT88SE amplifier and I want to turn a two output transformer.
I need count of primary turns and secondary turns, and size of wire.
I will using double C-core 9 cm^2
Someone can calulate the OPT data for me?
Thanks !

Sorry for my english

[schiller]

Originally posted by mayky
I bild a KT88SE amplifier and I want to turn a two output transformer.
I need count of primary turns and secondary turns, and size of wire.
I will using double C-core 9 cm^2
Someone can calulate the OPT data for me?
Thanks !

Sorry for my english

Hi, your core size is maybe good for 3-4 watt down to 20Hz. It will be a suboptimal design- if you try to put say 2500 turns in the primary, you will turn up with high DC resistance (loses)-.

Can you find a plate choke? Then you can make a desent parafeed 2,5k trans with this iron.

Without the dimensions of the bobbin you cannot calculate wire diameter/turns. You will not know if it fits.

Greetings
Konstantinos

P.S Is this a european or an american core?

[mayky]

Thanks !

I don't know what type this core, I got my frend.
Mayby some hungarien core, don't know. ~ sm85a

here a sizes.

I try turns primary 2400 turns 0,22 mm 5 section
and primary 136 turns 0,5 mm 4 section

This data from a hungarien diy book.

[mayky]

The usable size : 12,5mm x 52 mm

[schiller]

Originally posted by mayky
Thanks !

I don't know what type this core, I got my frend.
Mayby some hungarien core, don't know. ~ sm85a

here a sizes.

I try turns primary 2400 turns 0,22 mm 5 section
and primary 136 turns 0,5 mm 4 section

This data from a hungarien diy book.

2400 turns , 5/4 is quite o.k in terms of primary inductance and frequency responce in the highs, BUT:
with the wire sizes you posted (especially the sec. is way too thin), it will have (roughly estimated) about 2,8 Ohm DC resistance (reflected to the secondary). This is more than 50% power losses!

From your 8w from the KT88 more than 4 will just heat the trans, the rest will go to the speaker.

The core is too small for enough pri. inductance and 80mA DC. Try to stay under 150 Ohm DC for the primary AND under 0,5 Ohm sec. You will end up with fewer turns and sacrifice primary inductance.

4 pri/3sec is sufficient for the size and for about 1800 turns prim. You will not be able to put more than this, if you want to keep power losses under 20%.

My proposal: 1750 turns prim, 0,28 / 90t. sec 0,75 this is about 3k/8ohm instead of your 2,5k, but much better in efficiency. I am note sure that the primary will fit, so you may need to reduce turns a bit (depends on your bobbin)


Greetings
Konstantinos

[mayky]

Thanks Konstantinos!

Thanks for help.

If I not will be satisfied this iron, i try get a bigger iron.

What size is correct for 8-10 W output power ?

[schiller]

Try EI120/4 with 2100-2200 turns 0,35 primary 5/4 interlaving, 0,9 sec. Make each of the 4 secondaries 1 Ohm, like Sowter does. Expect about 30H pri. inductance, and -3db @ 60kHz.
Make pri. 1 and pri. 5 half the size of the others (see RDH4 about leakage inductance).
Undistorted power capability will be 20w by 20Hz at 80mA DC.

Greetings
Konstantinos

[mayky]

Thanks !

the new problem:
I need a SRPP shematic with ecc88 for drive my kt88 tube.
supply voltage: ~ 330 V

[Shoog]

the new problem:
I need a SRPP shematic with ecc88 for drive my kt88 tube.
supply voltage: ~ 330 V

No you don't. There are better drivers available. The SRPP is specifically not good in this role.

Shoog

[mayky]

What You think ? witch schem better for me by using Ecc88 (Mullard) ?
Max 1 piece condensatore in signal.