Tube and Voltage change on the TOS amp

[67polara]

Hello all.  I was thinking that when I build the T.O. special that I would use KT77 and up the voltage to 475v into a 4.2 k load.  What power out put might I expect and would it have any adverse effects on the existing circuit and or sound quality?

Tony

[stingray_65]

Hey Tony,

I don't know how I missed this post.

Check out the data sheet here. http://www.tubezone.net/pdf/kt77mov.pdf

It's interesting to see the note near the bottom of pg4 that mentions mounting distance of 3 1/2" minimum, I am unsure why.

I am not seeing anything in class AB1 fixed bias, but from looking at other charts we can guess between 60 and 70 watts.

The 4.2k impedance is a close enough match to the declare optimal 5.0k for P-P operation.

I would also consider tying pins 1 and 8 on your sockets so that other tubes might be installed

I could not imagine what tonal effects running KT77's would have. My only experience with these were in HI-FI equipment and even then they were ran ultra linear. (very loud VERY clean)

Ray

[67polara]

Thanks Ray.

I just noticed I can't find the exact spec's for my power transformer, that is current capabilities.  The part number is 029032 a fender part.  It is a bastard I guess.  

This is what I know:

355v no center tap
6.3 volt no center tap
54 volt bias windings
No 5 volt windings

I need to know the power handling capabilities and the 6.3 volt current available.  I need a little more than 4 amps 4.1 to be exact for the 6.3 windings. It came out of a fender super 60 red knob that had 2 x 5881's in it so I believe it is out of a 50 watt.  The KT77 require 1.4 amps each instead of .9 for 6l6's.  I think I will stay with cathode bias at first and see how that works out.  I don't want to stress the output tranny to much, but I want lots of clean headroom.

Can anyone help me please?

Tony

[Geezer]

Appears to be from a "Super 60"......that should give you an idea of the approx ratings/specs.

http://www.google.com/url?sa=t&source=web&cd=7&ved=0CDUQFjAG&url=http%3A%2F%2Fmusic-electronics-forum.com%2Fattachments%2F10360d1278030343-super-60.pdf&rct=j&q=029032%20PT%20fender&ei=TB-CTOauPNyBlgfXzdjPAw&usg=AFQjCNHXoR3-BZDaiRnJIVexRWs5r1CQHw

[67polara]

Thanks Geezer, but I already have that information what I need is the max filament current available for that transformer.  Can't seem to locate that information. 

Tony

[Geezer]

That info is probably lost to the sands of time.........

The Super 60 required ~~3A filament current

The TOS w/ KT77's will need ~~4A

If you're concerned about the PT's safety, you could run the big tubes off the PT filament supply, & get a small 6.3V tranny to run the little tubes.....they are very inexpensive. I think I paid ~~ $7 for one.....yep, here's the link to a 3A unit (Doug also sells them)

http://www.mouser.com/ProductDetail/Xicon/41FD030/?qs=sGAEpiMZZMv4oUrzpPKU3NKK6KmzX%252bbMxt1WBAv2nNQ%3d

[67polara]

Great idea I never thought of that!!!  That will fix everything 

Thank you Thank you

Tony

[67polara]

Can you point me to a place to buy the filament transformer please.  Seems like all I see they are really proud of and maybe I should just buy a new power transformer for a few bucks more.  I have a small power transformer also maybe I will just use that one this amp is gonna weight a ton anyways so what could a couple pounds more hurt LOL.

If I have the current I will probably add reverb and trem to it LOL the chassis is the size of a small car anyways LOL it's from a Smarvo 300 watt bass amp.  It had 6 KT88's on it but the iron was missing when I picked it up.  I got the chassis and case for free though.

Tony  

Never mind I didn't see the link you put on there for the tranny my bad.