Some time ago, me and friends decided that we make a few prototypes with GU50. The idea was to test as many different combinations. For input tube we decided for 6SN7, 6SL7, 6N1P, 6N23P, 6N6P, D3a, 6C3P, ECC83, ECC85, ECC81.
We made some SE prototypes, one of the PSE and the PP one. As the input tube we test: D3a, 6C3P (the best two), 6N23P, 6SN7, 6N6P (also very good - not enough gain), ECC83, ECC85 (not so good). The project is continuing. Now I'm working on the development of housing.
We found that the GU50 is one of the best, for me better than EL34 or EL84.
A couple more pictures of prototypes:
We made some SE prototypes, one of the PSE and the PP one. As the input tube we test: D3a, 6C3P (the best two), 6N23P, 6SN7, 6N6P (also very good - not enough gain), ECC83, ECC85 (not so good). The project is continuing. Now I'm working on the development of housing.
We found that the GU50 is one of the best, for me better than EL34 or EL84.
A couple more pictures of prototypes:
Attachments
Hi, my prototype is a mix of Fender AB763 with 12Ax7 as phase inverter, and two Gu50 at the power.
ry50 - 80W - YouTube
Only volume pot.
Almost finished!
ry50 - 80W - YouTube
Only volume pot.
Almost finished!
Me too.
Also I found that it is better than that 6L6 clones like KT-88.
Here are my prototypes:
Last edited:
Hi, I would state some "strange" behavior of my ampli.
When I cranck (or close cranck) the volume pot, it starts a riiiiiiizzzzzzz. Obvioulsly the amplifier is totally saturated and crunched. It happens without the guitar plugged too.
Some Ideas what could cause this effect. The circuit was based in the Fender 6G8 circuit end AB763. The PI tube is a 7025 as in 6G8.
Thanks a lot who try give-me an explanation!
I'm sending some pictures.
FAB
When I cranck (or close cranck) the volume pot, it starts a riiiiiiizzzzzzz. Obvioulsly the amplifier is totally saturated and crunched. It happens without the guitar plugged too.
Some Ideas what could cause this effect. The circuit was based in the Fender 6G8 circuit end AB763. The PI tube is a 7025 as in 6G8.
Thanks a lot who try give-me an explanation!
I'm sending some pictures.
FAB
Attachments
Last edited:
Hi DJNUBZ,
Plate Voltage 700V
OT 100W 6KOhms primary (Plate to plate impedance). Secondary 4 and 8 Ohms. I
Tube in pentode config, as 6L6. I changed the decoupling capacitor of output stage from 0,1uF (normally used in Fenders) to 0,022 as in Marshall 1959 model (plexi). The ampli was super super bass before change de capacitors. Bias voltage is -35V and tube current is 40mA (for each tube). Problems with NF, as related in other post of this section (ZZZZZZZZUUUUUUUUUU). So I don't use NF. I have the same problem wih a Plexi 1959. I don't know whow to fix this problem. The ampli seems stable and works well. Very loud. Good lucky, and let me know you experiences if you built a prototype.
Plate Voltage 700V
OT 100W 6KOhms primary (Plate to plate impedance). Secondary 4 and 8 Ohms. I
Tube in pentode config, as 6L6. I changed the decoupling capacitor of output stage from 0,1uF (normally used in Fenders) to 0,022 as in Marshall 1959 model (plexi). The ampli was super super bass before change de capacitors. Bias voltage is -35V and tube current is 40mA (for each tube). Problems with NF, as related in other post of this section (ZZZZZZZZUUUUUUUUUU). So I don't use NF. I have the same problem wih a Plexi 1959. I don't know whow to fix this problem. The ampli seems stable and works well. Very loud. Good lucky, and let me know you experiences if you built a prototype.
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