New Tim Mellows OTL project

[victor dascalu]

Nice work, congrat.
Can you post your final schematics with balanced input?
Have you tried a CCS stage on the triode cathods?

 

[victor dascalu]

I think you haven`t any chance to match 33`s from batch of 10. Need 100 tubes 🙂
I preburn 33`s with heater 6-9-12 VDC for 12 hours each step.
Also I decrease bias to 50 mA in OTL and burn some hours before 100 mA and 200 mA...

Why 6-9-12 vdc and why dc ?

 

[Black Jack]

It`s "training"
Because 6C33C work with 12.6 Vrms heaters in Tim Mellow`s design.
And applying standard voltage for new tube is not good.

 

[victor dascalu]

ok, let say trainning, but why dc instad of ac?

 

[Black Jack]

No matter AC or DC for training. VAC_rms = VDC
And using 12.6 VDC the same as 12.6 VAC

 

[Tyimo]

Hi!

How many Vrms needs the 6C33C output stage for full output power?

Greets:
Tyimo

 

[multi-volti]

Does anyone know if the 6C33C-V socket reliability problems are limited to the filament/heater pins?

I mistakenly assumed the one large pin (~0.123” diameter) was the high current pin common to both filaments but datasheet indicates all 4 filament pins are separate.

I would hope & assume the heater pins are the problematic area on the sockets but may not have been paying attention to prior discussion as I wasn’t actively concerned at those times.

Thank you

 

[atmasphere]

The large pin is the plate. The reliability issues are indeed related to the filaments. I don't think I've seen one of the other pins fail.

 

[victordascalescu54]

My "Tim Mellow" OTL
Some minor changes
- Balanced Inputs
- Valvo ECC808 Input Triodes
- MCU controlled High-voltage delay (15 min. pre-heat )
- More capacitance in power supply
- Total star wiring (Hi-Volt, ground, heaters) - no hum with ears close to speaker at max. volume.

Thanks Tim, Perfect design!



[IMGHAD]

Hi,
How did you manage to do balanced input to the Tim's project?
I did not find a practical way to do it and I am very interested to do it.
Regards,
Victor

 

[platon.rado]

Hi everyone.

Can i use an amplifier with a 4 ohm load ???

Thanks

 

[fdegrove]

Hi,

Yes, you can but keep in mind you'll only have about have the power you'd have at 8 ohm load.

Cheers, 😉

 

[zoran2303]

HI
just wonder, can auto bias such as
https://www.audioamp.eu/kategorie/modules-adaptive-bias-control/
be implemented in Mellow circuit?
Q-tron otl did that somehow
Zoran

 

[mbrennwa]

Why not?

 

[zoran2303]

Thank you mbrennwa