Used as a driver tube for a 300b, any opinions or experiences of setting the plate current for best sound? It will dissipate 7w and the data sheet shows 50ma at 200V. I have it at about 10ma which is just on the edge of it's linear operating range.
Brian Cherry
Brian Cherry
I've used this tube with fixed (battery) bias of 2.3V and plate voltages between 165 and 225.
Current comes out to about 30-35mA depending on the sample of tube you are using. This operating point sounds good to me. Applications are: as driver for a 2A3 loaded with a Lundahl 1668 plate choke, and in a line stage, loaded with a 5K:8 transformer.
The Munich guys have pointed out that 2.3 VBias is low for linestage use and they are probably right but the sound is good so I won't let it keep me up too many nights.
-j
Current comes out to about 30-35mA depending on the sample of tube you are using. This operating point sounds good to me. Applications are: as driver for a 2A3 loaded with a Lundahl 1668 plate choke, and in a line stage, loaded with a 5K:8 transformer.
The Munich guys have pointed out that 2.3 VBias is low for linestage use and they are probably right but the sound is good so I won't let it keep me up too many nights.
-j
Hi J,
Thanks. I'm also using a battery bias, 2.6V and 200V on the plate. What value grid leak resistor?
I used it to replace the 6SL7 and really like the sweet sound and grip it has. It's been said that it get a little grainy/glary at high plate currents.
How did you calculate the effective load the plate choke presents?
Brian
Thanks. I'm also using a battery bias, 2.6V and 200V on the plate. What value grid leak resistor?
I used it to replace the 6SL7 and really like the sweet sound and grip it has. It's been said that it get a little grainy/glary at high plate currents.
How did you calculate the effective load the plate choke presents?
Brian
With the linestage, I am using grid chokes (actually small line transformers wired with the windings in series.) With the power amp, I am using 18K but that is in parallel with a very low DC resistance coming from a transformer volume control so the effective DC resistance is only a few ohms here. I ran into a situation where 18K was too low a value for a certain preamp to feed, so I used something like 100K for that setup. The lower the better, but it depends what you are feeding it with how low you can go. A grid choke is ideal.
Well, I didn't actually: first I had on hand a Lundahl interstage transformer and I tried it and it worked well. Then a friend was ordering from Lundahl a bunch of stuff and I piggybacked on his order and got the corresponding plate chokes.
The rp of the 6C45P is so low that you don't need a tremendously high inductance to load it: almost anything meant as a plate choke should do fine, I think.
I tend to use what I have on hand, at least at first. I really didn't expect the line stage to work, it's a bit extreme (high mu/huge step-down), so I just slapped it together. Then it turned out I liked it, so it just sort of stayed slapped.
I'm also coming from a transformer volume attenuator, but with 75K in the gridleak position. A lower value resistor to get a little more voltage on the grid is something I'll try. I just put a choke on the plate, 50h/250ma with quite nice results. Only dropped 7 volts so still 195V at the plate.
Lots of different opinions out there. Just reading a thread that says battery on cathode is worse sounding than usual cap/resistor and better to use on the grid. I'll have to go back to test that one out.
Thanks for your comments.
Brian
Lots of different opinions out there. Just reading a thread that says battery on cathode is worse sounding than usual cap/resistor and better to use on the grid. I'll have to go back to test that one out.
Thanks for your comments.
Brian
6C45P driver stage and low-pass filter
Is it possible to obtain a 12dB low-pass filter properly adjusting the characteristics of plate choke and/or those of cathode resistor in a driver stage employing a 6C45P (receiving an input signal of about 2-3 volt)?
If so, may that be utilized in a biamping systems ?
Is it possible to obtain a 12dB low-pass filter properly adjusting the characteristics of plate choke and/or those of cathode resistor in a driver stage employing a 6C45P (receiving an input signal of about 2-3 volt)?
If so, may that be utilized in a biamping systems ?
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