KT88 SE schematic wanted.

[Hojvaelde]

Hello

I just got 2 chokes 10H 300mA 50 Ohm and 2 mail trafoes
330VAC 300mA ( ~ 400 VDC with solid state rectifiers ) + 70VAC 25mA (bias) + 6,3V 5A. ( under 80 USD brand new ) 😀

I think this is OK for a SE KT88 mono amplifier, but I need a schematic. Can You help me with that.

Regards

Benny

 

[EC8010]

I just did a search for KT88 SE (exact phrase) in the "Tubes" forum and came up with 21 results. Please search before starting a new thread...

 

[Mikael Abdellah]

Since I've got new IP for my server a couple of times, the links I've posted to my schematics doesn't work anymore. Here is the new URL: http://81.224.66.34/se_kt88.gif

Should work for you. I think you should be able to use it for starters and modify it for your needs.

 

[Hojvaelde]

Thanks Mikael

That was what I want.

I got 400 VDC from the power trafo. 😎

I can see that the current is under 100 mA.

Do You know the exact current?

How does it sound?

Regards

Benny

 

[Mikael Abdellah]

I think the draw was about 75mA. The sound is really wonderful with very detailed highs and a lots of dynamic and warm bass. The project has been on hold for over a year now, but I hope to finnish it in the next year. No point in rushing things 😉

 

[Sherman]

Since I've got new IP for my server a couple of times, the links I've posted to my schematics doesn't work anymore. Here is the new URL: http://81.224.66.34/se_kt88.gif

Should work for you. I think you should be able to use it for starters and modify it for your needs.

I can vouch for Mikael's design! I built it as a pair of monoblock power amps rather than integrated and it sounds great. It is simple to build and it appears you have the parts. Mine are biased at 75mA with a B+ of ~400V. (I used tube rectification but with your trafos I think you'll have to go SS to get the 400V.)

The only issue I've had was some oscillation on a particular piece of music. I think I've cured that by following the advice of analog_sa and decoupling the PS ahead of the input tube.

 

[JojoD818]

Mikael,

Just one question sir about the cathode resistor (470R/25W), I can't seem to find a source for such a high wattage resistor locally.

Can I use 3 pcs of 1500R/10W in parallel? Are there any special considerations for this resistor? I mean should it be a certain type such as those non-inductive types?

Please bear with me....

Thanks!
JojoD

 

[Mikael Abdellah]

There's really no need for 25W. The actual power running through the resistor is closer to 5, but when i tried with 15W it got awfully hot so I put in a 25W instead. It's a regular wirewound kind since low inductive metal film types aren't available at those power ratings. I could send you a pair of 470R/25W if you want. Just let me know. We enthusiasts and diy:ers gotta stick together 😉

 

[JojoD818]

Mikael,

Thanks very much for the kind offer! I will first see if the other parts can be sourced here locally. I already have some 6N1P tubes here and will also have access to the KT88 tubes soon. 😎

Thank you and will keep you guys posted.

JojoD

 

[Simpleton]

Hmm... would this be enough for using in the car with Hertz 91dB 2-way speakers? i already have a sand powered sub in there.
😀