Greeting fellow members,
This is my first post, my principal interest is (for now) is comparing GM-70 amp schematic, the "contemplative state" before considering building, anyways, what do you guys think of this circuit regarding these aspects :
1 - input impedance?
2 - the use of a output transformer as an input (yes you can warn me about not to go this way, ahah)
3 - is the simplicity of the circuit worth exploring?
4 - the possibility of using a higher plate voltage
5 - the cost (of course I would look for cheaper trans than Tango)
Here is the link to the original page : http://www.ononet.jp/~micky/gm70s.html
Here are the published characteristics
Happy building and listening!
Olivier
This is my first post, my principal interest is (for now) is comparing GM-70 amp schematic, the "contemplative state" before considering building, anyways, what do you guys think of this circuit regarding these aspects :
1 - input impedance?
2 - the use of a output transformer as an input (yes you can warn me about not to go this way, ahah)
3 - is the simplicity of the circuit worth exploring?
4 - the possibility of using a higher plate voltage
5 - the cost (of course I would look for cheaper trans than Tango)
Here is the link to the original page : http://www.ononet.jp/~micky/gm70s.html
Here are the published characteristics
Happy building and listening!
Olivier
Ooops I forgot to include this detail, he is using an regulated ps for the filament
Look at the rear of the amp
Thanks for you reply TheGimp ;-)
Look at the rear of the amp
Thanks for you reply TheGimp ;-)
What signal source is driving the 8 Ohm to 3.5k input transformer?
A solid state power amplifier?
Or,
A tube power amplifier?
Are those signal sources stable when they are loaded by nothing other than an essentially unloaded 8 to 3.5k transformer?
A solid state power amplifier?
Or,
A tube power amplifier?
Are those signal sources stable when they are loaded by nothing other than an essentially unloaded 8 to 3.5k transformer?
1. source impedance must be very low unless you strive for a Sakuma style effect box;
3. depends on what you expect: serious "hifi" amplifier? Not worth exploring IMO;
5. you might consider Lundahl LL9202 (6k5 primary impedance - 85mA - 57H).
When you build: take care of correct connection of the capacitors in the negative grid supply (not like in the schematic....).
3. depends on what you expect: serious "hifi" amplifier? Not worth exploring IMO;
5. you might consider Lundahl LL9202 (6k5 primary impedance - 85mA - 57H).
When you build: take care of correct connection of the capacitors in the negative grid supply (not like in the schematic....).
Thanks for all your reply, I understand better now, looks like a booster amp like directdriver mentioned, so for me, not worth building
Interesting polarity of some of the negative rail caps. The negative regulator will not support the current in the wrong direction if GM70 driven into positive grid current.