Improvements for the Mikael Abdellah KT88???

[Nikon1975]

Heater supply

A quick question: I have two 6.3 secondaries in my power transformer.

How would you connect them ? Left and right or preamp and amp ?

Thanks,

Davide

 

[alexg]

A quick question: I have two 6.3 secondaries in my power transformer.

How would you connect them ? Left and right or preamp and amp ?

Thanks,

Davide

Either way should be ok.

 

[alexg]

Alex, could you kindly post the scheme of the lm317 cathode mod? Did you put capacitors in the diode mod? What value of snubbers did you use? I think by next week my ampli should be ready to be plugged 🙂

Thanks,

Davide

Here's how you use the LM317 for current sink:

diyparadise - YH's Lazy Man Constant Current Source

 

[bklossner]

Eight years later......

I have decided to build this amp as my first tube amp project and wanted to pop in to thank everyone for this thread and their incredibly helpful comments.

 

[Martyblackeye]

Hi, I built that amp.

If you use motor run capacitors (ASC preferably) on the power supply, it sounds way better than the Nichicon electrolytic.

I omitted the 5H choke on the LC filter going to the 6n1p and replaced it with a 100R resistor (on some 6n1p, am getting oscillations and replacing the 5H with a resistor cured the problem).

I also bypassed all the cathode bypass electrolytic capacitors with polypropylene, and it seemed to help a bit.

Another change that I did which I did not submit at Gio's site is I replaced the cathode resistor of the 6n1p with an LM317 current sink, you can also try using two red leds to bias the 6n1p (both seems to sound better than the 1K resistor).

I have not updated the schematic at Gio's site, with the tweaks I did.

Look for Sherman and porkchop's thread on this forum, they described how they built this amp and the tweaks they did.


HTH,

AlexG

Sherman,

Quick question about replacing the 5H choke with a 100k resistor. What watt resistor should be placed here and how do you calculate that?

Thanks!

 

[gerrittube]

You will need 100 Ohm (not 100K). I don’t know the current through the resistor, but a 1 or 2 Watt will be fine.