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Old 15th November 2003, 02:27 AM   #1
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Question Need good 10-20watt design

Greetings,

I have been considering purchasing an amp kit, (about 10-15 watts per channel) but don't want to pay overhead instead of doing my research. Most of the schematics I have found seem rather non-informative. Almost all are missing component values, and needed info on curciut. Could anyone help? Needs something nice to listen to while exploring my hobbies.

Looking for 10-20 watts clean sound, not really concerned about config, mabye PP or SE, wish to avoid expense of OTL. Dosen't need to be tube rectified, just needs to sound darn good. Clone of simple amp with readily available parts would be nice. Feel free to contact me privately Thanx!!

Highest regards to the forum and users,
-Jason Grabo
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Old 15th November 2003, 10:32 PM   #2
PassFan is offline PassFan  United States
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Try this amp at Gabevee's site. He also sells a kit at a low overhead. It sounds great. http://members.tripod.com/~gabevee/maggie.html
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Old 15th November 2003, 11:36 PM   #3
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The Magnavox derivative that PassFan links above is a great little amp that can be built for low $ and sounds excellent (esp with Dyna 565 OPT's).

Better (and cleaner to my ears) can be had with the Vacuumstate PP1C and PSU
but it will cost more to build. There are however a number of mods to improve it's perfomance even further. If you want more power, then simply use KT88/6550 output tubes and drop the cathode resistors to 370 - 400R, and you'll get about 20W class A.

There are scads of other designs too, but I've built these two (the Magna with 6V6's too) and they sound good.
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Old 16th November 2003, 03:47 AM   #4
SHiFTY is offline SHiFTY  New Zealand
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Well I have found 807 class A Push-pull to be brilliant- at the moment I am running it with no negative feedback as it sounds better! 807s are cheap as and you can use any 6L6 schematic.

I used an EF37A front end, 6SN7 drivers and cathode biased 807s for about 15W out. SS diode rectifiers, 8K:8ohm output trannies, nothing special but it sounds better than my SET amp! Dammit, i have spent mucho $$$ on my SET....
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Old 16th November 2003, 12:17 PM   #5
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Quote:
Originally posted by ShiFtY
Well I have found 807 class A Push-pull to be brilliant- at the moment I am running it with no negative feedback as it sounds better! 807s are cheap as and you can use any 6L6 schematic.

I used an EF37A front end, 6SN7 drivers and cathode biased 807s for about 15W out. SS diode rectifiers, 8K:8ohm output trannies,
I'm not surprised you like the 807's in PP, and they're excellent value because people seem to have an aversion to non-octal sockets and top caps. Plus there are bazillions of them out there.

What op point are you running the outputs at to get 15W class A?

Quote:
nothing special but it sounds better than my SET amp! Dammit, i have spent mucho $$$ on my SET....
hehehe the SETheads have no idea what they're missing.
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Old 3rd April 2004, 09:18 PM   #6
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Hello Bret,

you say "Better (and cleaner to my ears) can be had with the Vacuumstate PP1C and PSU
but it will cost more to build. There are however a number of mods to improve it's perfomance even further. If you want more power, then simply use KT88/6550 output tubes and drop the cathode resistors to 370 - 400R, and you'll get about 20W class A.
"

A friend of mine would like to find a good 20W class A KT88 amplifier. Have you try this PP1C ? can you confirm that it work well and sound good ?

At this time the only schem I have find is an antique sound lab mgspm25 25W class A but i'm not sure of the primary of the output transformer http://ptsoundlab.jexiste.fr/depotimg/spm25.jpg

Thank you

Pascal.
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Old 4th April 2004, 12:19 AM   #7
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Hi,

Hello Brett,

Just to say hello...Welcome back.

Pascal,

The schematic you show is for a PSE amp with a pair of KT88s.
I think you obtain much better results with a PP using a pair of KT88s in Class A.

Cheers,
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Old 4th April 2004, 01:33 AM   #8
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Um...10-20W will be huge in SE so you'll want PP... easier too... Could go from a circuit like.. oh... my 6W6 amp (check the schematics collection off my sig), only, use 6V6s because in all fairness, the circuit *should* melt the 6W6s.

Iron is cheap and plentiful from places like Hammond. A 1600 series 10 or 15W 8 or 10k PP OPT will be perfect for 6V6s; as for the power transformer, I believe a 272BX will work great.
As for NFB (which you'll want given a pentode PP amp), that's a can of worms to open in another thread.

Tim
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Old 6th April 2004, 01:36 PM   #9
ICARE is offline ICARE  France
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Hello Grabo, and Pascal

If you are looking for a good SE 11 W maybe you can try the SE KT88, Im actually making this amp.
Of course it depens a lot of your speakers but I heard than its a really nice sound, and for only 600-700 .

If you want the shematics, refer to PTSOUNDLAB web site which is very well done and everything is clearly indicated (values etc..etc..)

See you
J-Y
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Old 6th April 2004, 05:53 PM   #10
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Hello Frank,

what do you think of this modified GEC30 KT88 ? http://personales.ya.com/lcardaba/projects/GEC/GEC.htm

I think I will build it but before I would like to have opinions.

Thanks

Pascal.

PS: Hello Icare, I have build this SE before, marvelous, and I build one for a friend.
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