A schematic of Single Ended Kt88 power amp
without NFB is needed for my project.
It is difficult to seach one on the net, please help.

"·à¤l¤f" wrote in message
...

A schematic of Single Ended Kt88 power amp
without NFB is needed for my project.
It is difficult to seach one on the net, please help.

How about http://www.bonavolta.ch/hobby/en/audio/kt88_2.htm

You could always disconnect the NFB (after you've tried it, of course).

kyser wrote:

"·à¤l¤f" wrote in message
...

A schematic of Single Ended Kt88 power amp
without NFB is needed for my project.
It is difficult to seach one on the net, please help.

How about http://www.bonavolta.ch/hobby/en/audio/kt88_2.htm

You could always disconnect the NFB (after you've tried it, of course).

But then he'd have a pentode amp with no FB,
and very high Ro, and high thd, and maybe it'd sound like crap,
and have far too much gain.

I'd suggest the load value be changed to 7kohms,
B+ set for +450v, Iq at 73 mA, and the KT88 set for triode,
and the OPT needed should be 7k to 5 ohms.
Then the EF86 could be drop kicked over a fence,
and replaced with a decent triode, such as a 6CG7 with both halves
paralleled,
since it'd fit in the same socket, and does what 6SN7 does.
12AT7 would not be too bad, and any 2H from the input tube gets
cancelled
by that produced in the output tube.
Ro without FB would be Ra / ZR of the OPT = 1,100 / 1,400 = 0.7 ohms,
plus winding resistances, so say 1 ohm.
Thd will be around 5%, mainly 2H, at about 8 watts.
Maybe it sounds as good or better than 300B.

Patrick Turner.

Hi RATs!

I am listening to KT88 SE, triode, which is decent

OPT is 1.6K.

100mA at 240 volts on the plate.

Headroom

Happy Ears!
Al

PS Schema on request
Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

"TubeGarden" wrote in message
...

snnnneeeeeeppppppp

PS Schema on request
Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

ZM request schema of your Edgars...........
80Hz especially.........


--
..
Choky
Prodanovic Aleksandar
YU

"don't use force,
use a larger tube and IST"
- ZM
..

Hi RATs!

www.edgarhorn.com

Tell Bruce you need 80 Hz plans, he can help

Happy Ears!
Al

PS you have to wait til site is ready....


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

I know that already,ya silly RAT!

ps.just jokin'-I have article from SB,and numerous Tractrix calcs from net
..........


--
..
Choky
Prodanovic Aleksandar
YU

"don't use force,
use a larger hammer"
- ZM
..
"TubeGarden" wrote in message
...
Hi RATs!

www.edgarhorn.com

Tell Bruce you need 80 Hz plans, he can help

Happy Ears!
Al

PS you have to wait til site is ready....


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

"Patrick Turner" wrote in message
...

kyser wrote:

"·à¤l¤f" wrote in message
...

A schematic of Single Ended Kt88 power amp
without NFB is needed for my project.
It is difficult to seach one on the net, please help.

How about http://www.bonavolta.ch/hobby/en/audio/kt88_2.htm

You could always disconnect the NFB (after you've tried it, of course).

But then he'd have a pentode amp with no FB,
and very high Ro, and high thd, and maybe it'd sound like crap,
and have far too much gain.

I actually own zur Linde's book (from which the schematic is taken and
which, BTW, is full of typos) and omitted to mention that, as shown, the
KT88 can be connected

.. as a triode (tying the screen to the anode via R12, and omitting R13/Cx);
or

.. as a pentode, by removing R12, and inserting R13 and Cx for the screen
supply (shown dotted in the schematic).

Bona's page doesn't make this clear.

I'd suggest the load value be changed to 7kohms,
B+ set for +450v, Iq at 73 mA, and the KT88 set for triode,
and the OPT needed should be 7k to 5 ohms.
Then the EF86 could be drop kicked over a fence,
and replaced with a decent triode, such as a 6CG7 with both halves
paralleled, since it'd fit in the same socket, and does what 6SN7 does.
12AT7 would not be too bad, and any 2H from the input tube gets cancelled
by that produced in the output tube.
Ro without FB would be Ra / ZR of the OPT = 1,100 / 1,400 = 0.7 ohms, plus
winding resistances, so say 1 ohm.
Thd will be around 5%, mainly 2H, at about 8 watts.
Maybe it sounds as good or better than 300B.

Fair enough, but what's the problem with the EF86, anyway?

Two 1.75/3.5K primary, 0.9X4 secondary, 4 + 5 sections 150W
SE EI output transformers are ready here, but the power trans is
340-280-0-280-340V 800mA, 5X0-5-6.3 6A filaments,
70V 100mA negative bias, originally wounded for parallel or single 300B SE,
but now my aim is changes to KT88 parallel or single KT88 SE
Would you please send me a copy of your schematic for reference.
ps why you set the B+ so low? reducing the turn ratio of the OPT to gain a
better response at the high freq?

"TubeGarden" ¦b¶l¥ó
¤¤¼¶¼g...
Hi RATs!

I am listening to KT88 SE, triode, which is decent

OPT is 1.6K.

100mA at 240 volts on the plate.

Headroom

Happy Ears!
Al

PS Schema on request
Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

"Patrick Turner" wrote in message
...

snip
Maybe it sounds as good or better than 300B.

Patrick Turner.

A nice inquisitor is on the way over to your shed, he's bringin' some tools
of his own, to convince you otherwise... Just be frank and honest with
him - he's really open-minded....
-dim

"Patrick Turner" ¦b¶l¥ó
¤¤¼¶¼g...


kyser wrote:

"·à¤l¤f" wrote in message
...

A schematic of Single Ended Kt88 power amp
without NFB is needed for my project.
It is difficult to seach one on the net, please help.

How about http://www.bonavolta.ch/hobby/en/audio/kt88_2.htm

You could always disconnect the NFB (after you've tried it, of course).

But then he'd have a pentode amp with no FB,
and very high Ro, and high thd, and maybe it'd sound like crap,
and have far too much gain.

I'd suggest the load value be changed to 7kohms,
B+ set for +450v, Iq at 73 mA, and the KT88 set for triode,
and the OPT needed should be 7k to 5 ohms.
Then the EF86 could be drop kicked over a fence,
and replaced with a decent triode, such as a 6CG7 with both halves
paralleled,
since it'd fit in the same socket, and does what 6SN7 does.
12AT7 would not be too bad, and any 2H from the input tube gets
cancelled
by that produced in the output tube.
Ro without FB would be Ra / ZR of the OPT = 1,100 / 1,400 = 0.7 ohms,
plus winding resistances, so say 1 ohm.
Thd will be around 5%, mainly 2H, at about 8 watts.
Maybe it sounds as good or better than 300B.

Patrick Turner.

What the output power will be if 340V 73mA or 400V 73mA
is applied to a KT88, using a 3.5K output transformer,

"Shiva" ¦b¶l¥ó
¤¤¼¶¼g...

"Patrick Turner" wrote in message
...

snip
Maybe it sounds as good or better than 300B.

Patrick Turner.

A nice inquisitor is on the way over to your shed, he's bringin' some
tools
of his own, to convince you otherwise... Just be frank and honest with
him - he's really open-minded....
-dim


sounds like a poem, a tube amp should be like that

kyser wrote:

"Patrick Turner" wrote in message
...

kyser wrote:

"·à¤l¤f" wrote in message
...

A schematic of Single Ended Kt88 power amp
without NFB is needed for my project.
It is difficult to seach one on the net, please help.

How about http://www.bonavolta.ch/hobby/en/audio/kt88_2.htm

You could always disconnect the NFB (after you've tried it, of course).

But then he'd have a pentode amp with no FB,
and very high Ro, and high thd, and maybe it'd sound like crap,
and have far too much gain.

I actually own zur Linde's book (from which the schematic is taken and
which, BTW, is full of typos) and omitted to mention that, as shown, the
KT88 can be connected

. as a triode (tying the screen to the anode via R12, and omitting R13/Cx);
or

. as a pentode, by removing R12, and inserting R13 and Cx for the screen
supply (shown dotted in the schematic).

Bona's page doesn't make this clear.

I'd suggest the load value be changed to 7kohms,
B+ set for +450v, Iq at 73 mA, and the KT88 set for triode,
and the OPT needed should be 7k to 5 ohms.
Then the EF86 could be drop kicked over a fence,
and replaced with a decent triode, such as a 6CG7 with both halves
paralleled, since it'd fit in the same socket, and does what 6SN7 does.
12AT7 would not be too bad, and any 2H from the input tube gets cancelled
by that produced in the output tube.
Ro without FB would be Ra / ZR of the OPT = 1,100 / 1,400 = 0.7 ohms, plus
winding resistances, so say 1 ohm.
Thd will be around 5%, mainly 2H, at about 8 watts.
Maybe it sounds as good or better than 300B.

Fair enough, but what's the problem with the EF86, anyway?

Its a pentode, and has to make about 15vrms drive to the pentode output tube,
or about 30vrms for triode, and so will have a lot more thd if run as a pentode,

and so you have at least two cascades stages with a lotta thd and high Ro,
hence the NFB is required to clean up the mess, but it doesn't do that as well
as if there wasn't much thd to start with. You could could connect the EF86
as a triode. I'd prefer to go for the 6CG7, and a little kick of the 86
over a fence. EF86 as pentode are better when the signal doesn't exceed 2vrms,
but even then their Ro is high, so the stray C affects the response.
Quad use a pair in a sort of balanced input circuit, and they are being flogged
hard there,
but at least the balanced reduces the even order thd over the SE case.
The odd order thd remains.
I am picky I know, but then I lke the amps to be able to power 89 dB/w/m
sensitive speakers, and you need every bit of linearity that can be had,
when you only have 7 to 14 watts to play with, and the thd should be
nealy all 2H.

Patrick Turner.