I assume this is a GEC or Mullard design, no?

Looks very good....I'm wondering if a starter amp project wouldn't be
better advised to use some tubes less expensive than KT88s though.

Did the original paper cover winding the OPT? Do any wind houses do
them (I doubt many people really want to wind their own...)?

I assume this is a GEC or Mullard design, no?


** Bits of this and bits of that.


Looks very good....I'm wondering if a starter amp project wouldn't be
better advised to use some tubes less expensive than KT88s though.



** What prices have you seen KT88s for ??

Sovtek brand ones are cheap here in Aussie - A$39.50

You can also use 6550s - from Sovtek and others.




................ Phil

wrote:

I assume this is a GEC or Mullard design, no?

The basic topolgy for the power amp part is
SET input and LTP driver triodes and UL output.
Its what Mullard and Leak and VTL and countless others have used.

I have added phase tweaking to improove bass and treble stability,
and a CCS tail to the LTP, which automatically balances the LTP
with equal output voltages if the R used are 1% types.

The CCS tail is also taken to a -ve supply, allowing
a nice high operating EA for the LTP triodes.
There is no direct coupling between the input SET and the LTP;
it is better my way.

The input stage is just a typical simple line gain preamp stage
built into the power amp to allow sensitivity to be good.


Looks very good....I'm wondering if a starter amp project wouldn't be
better advised to use some tubes less expensive than KT88s though.

6550EH is OK.

But why worry about the cost of the tubes???

To build 5050, the cost is quite high whatever you use,
so the extra cost of KT88 is worth it.


Did the original paper cover winding the OPT? Do any wind houses do
them (I doubt many people really want to wind their own...)?

The 5050 that I have supplied a few folks has 60 mm stack
x 38 mm tongue E&I core, or 50 mm stack x 44 tongue
core, GOSS, and the windings are similar to what is shown
for OPT No1, which is used for a sample design at my web pages
in the OPT section.

But perhaps a 5 Kg Hammond OPT will be OK.

I don't know, I have never used a Hammond yet.

Patrick Turner.