• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

6C33 Internal Impedance (rp)?

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#2
Hesky said:
Hello, does anyone know the rp value of this tube?
Thanks

Hesky
Click to expand...

Hello ,
Ra is >150 ohms depending on the operating point , refer to the curves . Take any measurements from the curves with a pinch of salt , 6C33 are very variable electrically and may bias differently in-circuit

cheers 🙂

316a
 
#4
Curves

Hesky said:
Thanks 316,
ah, so you get this figure off the anode characteristic curve. I will check it out.

cheers
hesky
Click to expand...

Hello ,
Don't go overboard with the dissipation , high slope valves like the 6C33 can be tricky to tame at times . Chose an operating point between 180V-250V around 40-45 watts dissipation . What is this for ? OTL ? SE ? Pushpull ? I can always model the output stage if you let me know what you have in mind

cheers 🙂

316a
 
#5
Hello, the operating voltage is 250 Volts with a quiescent current of approximatly 100 to 120mA per tube. dissipation will be low, its for a pp amplifier. I just need all the parameter necessary to get a custom made output transformer made up by Sowter.

Thanks🙂
Hesky
 
#6
SIMS

Hesky said:
Hello, the operating voltage is 250 Volts with a quiescent current of approximatly 100 to 120mA per tube. dissipation will be low, its for a pp amplifier. I just need all the parameter necessary to get a custom made output transformer made up by Sowter.

Thanks🙂
Hesky
Click to expand...

4k a-a 250V -103V 100mA 18w class A 3% 3rd harmonic distortion
3k5 a-a 250V -100V 120mA 20w class A 2.9% 3rd harmonic

These will require a driver with it's own HT unless you're brave and use +/- 250V rails and direct couple 😉 A 6SN7 with 47k loads and 500V HT may be marginal . Advise looking at a driver such as 6BX7 , ECC99 , 5687 , 12B4A or maybe even 12BH7 . Note : the distortion quoted above is for the output stage only , assume that feedback will be required . I've gone for class A1 , let me know if you want me to shoot for another operating point in AB1

cheers 🙂

316A
 
#8
Hi,

The driver tube is an ECC99 with its own 310V ht.
Click to expand...

Not only that, it needs a stabilised B+ to work optimally as well.
SRPP stage is used as a splitter/driver, you see.

The OPT has a Zprim of 600 Ohm.

If you let go of the pot at the input you can drive the amp from a balanced source as well...Interesting idea.
I must say I quite like the way it's been thought out.

Cheers, 😉
 
#9
Hi Frank,

I'm still sticking closely to the schematic, took weeks to track down the discontinued VB408 reg IC's used to regulate and stabilize the driver HT supply. I'm sure it could have been done using a different method though.
Once i've gained enough knowledge and confidence I'll have a go at putting together a tube amp circuit all of my own 😀 , but not before I've read Morgan Jones valve amp book 10 times over. far to dawnting at the moment :xeye:

Hesky
 
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