Hi!
Please tell me what mod numbers I must NOT implement if I plan to use stock EL34 tubes with 8ohm speakers?
From my point of view - mods # 2, 4, 11(?), 12, 14
Am I right?
Regards!
Please tell me what mod numbers I must NOT implement if I plan to use stock EL34 tubes with 8ohm speakers?
From my point of view - mods # 2, 4, 11(?), 12, 14
Am I right?
Regards!
2) of course, not
4) yes, but not mandatory
11) replaced by 17: see schematic values for the three bias resistor values
12) 5Z4 is at limit (125 ma) better 5V4 rectifier or even GZ34 for less sag and additional voltage.
14) why not? depend on loudspeaker and it is always good to make flat impedance
I have also replaced the 10 ohm series resistor with a small inductor (less than 1mH).
I have replaced the cathod bias resistor of the double triode with a red vintage led unbypassed. Anode resistor is now 56 K instead of 75K.
Thank you very much for the answer!
Please can you tell me where I can see the correct Zobel RC Network circut diagramm or equations to calculate it's parameters by myself?
Whats the result and the matter of your latest changes 10 ohm and 56 ohm resistors?
Please say a few words about it...
Regards!
Please can you tell me where I can see the correct Zobel RC Network circut diagramm or equations to calculate it's parameters by myself?
Whats the result and the matter of your latest changes 10 ohm and 56 ohm resistors?
Please say a few words about it...
Regards!
by eliminating the 10 Ohm in power supply, you gain extra few volts in power supply (so less sag and more dynamic), replaced by a 600 uH toroid choke (to clean RF in power supply). I have the space and doesn't bring additional sag. I like the sonic results.
The 10 ohm resistor I think would act as a fuse is something went wrong and protects the rectifier if you switch the power on with tubes still warm. I added several fuses everywhere in any case...
lowering to 57K ohm the plate resistor rotates clockwise the load line of the parallel triodes which run hotter and fits perfectly with the use of the red cathode vintage led (instead of the bypassed cathode resistor): I measured the second harmonic even more dominant vs odd harmonics
Tips for EL34, KT66, KT88, etc
My A10 is Wiring version.
Enjoy for KT88 tube.
I changed the bias method to CCS(Constant Current Source).
CCS circuit is TL783KCS(125Volt) with Ceramic Heat sink.(The IR thermometer indication approximately 25'C...very cool)
Cathode resistor 500 ohm exchange to CCS 50mA(1.25Volt/25 ohm 1%).
It is not necessary to calculate a bias resistor every Power tubes.
* Voltage tube to 12AX7 with Socket.
* Rectifier tube to 5AR4.
* Power tube to KT88.
Best Regards.
My A10 is Wiring version.
Enjoy for KT88 tube.
I changed the bias method to CCS(Constant Current Source).
CCS circuit is TL783KCS(125Volt) with Ceramic Heat sink.(The IR thermometer indication approximately 25'C...very cool)
Cathode resistor 500 ohm exchange to CCS 50mA(1.25Volt/25 ohm 1%).
It is not necessary to calculate a bias resistor every Power tubes.
* Voltage tube to 12AX7 with Socket.
* Rectifier tube to 5AR4.
* Power tube to KT88.
Best Regards.
Attachments
TL783 CCS circiut for Any tubes...
Hello Dear.
TL783 buy from ebay, amarzon, aliexpress...or TI free sample(max 5pcs).
with Ceramic heat sink(cool pad).
The heat sink is not necessary for a fact if I calculate thermal resistance of TL783. It is not hot even if I touch it by finger.
Firstly I bought it to work in LM317.
Because LM783 is FET structure, thermal resistance is good.
However, in LM317 a heat sink is necessary for the NPN Transistor structure.
Best Regards.
Hello Dear.
TL783 buy from ebay, amarzon, aliexpress...or TI free sample(max 5pcs).
with Ceramic heat sink(cool pad).
The heat sink is not necessary for a fact if I calculate thermal resistance of TL783. It is not hot even if I touch it by finger.
Firstly I bought it to work in LM317.
Because LM783 is FET structure, thermal resistance is good.
However, in LM317 a heat sink is necessary for the NPN Transistor structure.
Best Regards.
Attachments
Tips for EL34, KT66, KT88, etc
Note:
1. Power filter cap replace to NICHICON 330uF 400V 105'C(EKMQ401VSN331MR35S = 30mm/D x 35mm/L) or your PCB size and height check pls.
2. To revise bias at 70mA later ... When at least 330uF becomes if it is going to supply power enough, I feel relieved.
3. Resistor value to 18 ohm 1% 1/4W
4. Because EL34 is relatively cheap, there are few burdens shortening life even if it becomes.
Keep the fire burning EL34, and let's enjoy a healing sound.
Best Regards.
Note:
1. Power filter cap replace to NICHICON 330uF 400V 105'C(EKMQ401VSN331MR35S = 30mm/D x 35mm/L) or your PCB size and height check pls.
2. To revise bias at 70mA later ... When at least 330uF becomes if it is going to supply power enough, I feel relieved.
3. Resistor value to 18 ohm 1% 1/4W
4. Because EL34 is relatively cheap, there are few burdens shortening life even if it becomes.
Keep the fire burning EL34, and let's enjoy a healing sound.
Best Regards.
