I'd like to hear from those of you using a 46 as driver or output tube. I'm lucky to have a small number of them.
Schematics, operating points and experiences would be very welcome.
Schematics, operating points and experiences would be very welcome.
HI Andy!
If you remember, I implemented the 46 with filament bias (yes crazy I know) to drive the 814 SE amplifier. Sounded amazing and I think alongside the 45, is one of my preferred DHTs.
I have the plan to get the 46 back into my 300B. At the moment I use the D3a which marries very well with the 300B. I can get 37dB gain in my amp but surprisingly isn't enough to get the 300B at maximum output power. My amplifier has direct coupling source follower which can even provide a tad of positive grid current, not that I'm looking to operate it in A2, but good to have the headroom for dynamic response at loud volume.
I hooked up the 01a preamp which I was keen to due to its detail and sound. The gain is too much so had to add the volume control at the output of the 01a. I'm very happy with the amplifier and not likely to change it.
Still, will add the 46 for fun at some point with SUT to get it to a gain of about 45. I will still need the preamp though.
I always ran it at about 30mA/200V, that was the best performance I get out of it.
Here is how I'd do it again:
46 driver – Bartola(R) Valves
Cheers
Ale
If you remember, I implemented the 46 with filament bias (yes crazy I know) to drive the 814 SE amplifier. Sounded amazing and I think alongside the 45, is one of my preferred DHTs.
I have the plan to get the 46 back into my 300B. At the moment I use the D3a which marries very well with the 300B. I can get 37dB gain in my amp but surprisingly isn't enough to get the 300B at maximum output power. My amplifier has direct coupling source follower which can even provide a tad of positive grid current, not that I'm looking to operate it in A2, but good to have the headroom for dynamic response at loud volume.
I hooked up the 01a preamp which I was keen to due to its detail and sound. The gain is too much so had to add the volume control at the output of the 01a. I'm very happy with the amplifier and not likely to change it.
Still, will add the 46 for fun at some point with SUT to get it to a gain of about 45. I will still need the preamp though.
I always ran it at about 30mA/200V, that was the best performance I get out of it.
Here is how I'd do it again:
46 driver – Bartola(R) Valves
Cheers
Ale
Hello Ale
Yes - I remember your 814 amp. Must have sounded very nice - I don't remember hearing it.
A few questions....
- How well does a x8 SUT work?
- I'm a bit light on bass with my unbypassed 200R resistor and the 126B plate choke. What's contributing to this?
- In filament bias, a smaller resistor means less heat. I was thinking a 6R resistor putting 9v on the cathode at 1.5A filament current. Your operating point is 17v. Did you try less than that, closer to 9-10v?
Good to hear from you as always!
Yes - I remember your 814 amp. Must have sounded very nice - I don't remember hearing it.
A few questions....
- How well does a x8 SUT work?
- I'm a bit light on bass with my unbypassed 200R resistor and the 126B plate choke. What's contributing to this?
- In filament bias, a smaller resistor means less heat. I was thinking a 6R resistor putting 9v on the cathode at 1.5A filament current. Your operating point is 17v. Did you try less than that, closer to 9-10v?
Good to hear from you as always!
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Hi Béla
Sorry, not sure if I wasn’t clear. My DAC has a very low output. The D3a can drive 200Vpp in my case, but gain isn’t enough due to the DAC low output level. I need about x120 I think.
Ale
Hi Andy
I have a SUT 1:8 and the mu of the 46 is about 5.
I can unbypass the cathode resistor as the stage is a hybrid mu-follower and that doesn’t impact the bass. If you choke-loaded, then yes, a different story
You can try about 9V, I think I play down to 10 or 12V in my early experiments but can’t remember. If it’s for a pre-amp, then absolutely.
Hope you’re keeping well. This lockdown is driving me insane with the kids around 🙂
Cheers
Ale
Hi Ale
Is this your standard gyrator in the stage? I have some I could use.
I do have a NP Acoustic amorphous choke which is 180H instead of the 126B's 44H. That should make a difference. And anyway, I can go to filament bias. I think it's worth getting this 46 stage exactly right. It's a great sounding tube. You don't see it used too much, and dealers don't seem to have much stock.
Is this your standard gyrator in the stage? I have some I could use.
I do have a NP Acoustic amorphous choke which is 180H instead of the 126B's 44H. That should make a difference. And anyway, I can go to filament bias. I think it's worth getting this 46 stage exactly right. It's a great sounding tube. You don't see it used too much, and dealers don't seem to have much stock.
This is my measured power output / distortion chart from when I fooled around with cathode biased 46 a few years ago. The base amplifier is a Tubelab SSE board, hacked to take directly heated tubes.
The OPT was a cheap 5K Edcor XSE. Distortion is two tone IMD, 4:1, with tones of 200 Hz and 6K to compensate for the poor low frequency response of the Edcor OPT. I didn't check for THD. My test equipment is pretty mediocre.
46 makes a very good triode, and I'm surprised it is not more popular. I don't recall the operating point, and my notebook is not here with me, but I think Rk was about 1200 ohms, so I was probably using a pretty high B+.
It may be heresy, but I recall that it responded well to local plate to grid feedback.
Hope this is useful.
edit: added 45 and 47 for comparison, same hacked SSE, although driver tube and operating points will be specific to each type tube
The OPT was a cheap 5K Edcor XSE. Distortion is two tone IMD, 4:1, with tones of 200 Hz and 6K to compensate for the poor low frequency response of the Edcor OPT. I didn't check for THD. My test equipment is pretty mediocre.
46 makes a very good triode, and I'm surprised it is not more popular. I don't recall the operating point, and my notebook is not here with me, but I think Rk was about 1200 ohms, so I was probably using a pretty high B+.
It may be heresy, but I recall that it responded well to local plate to grid feedback.
Hope this is useful.
edit: added 45 and 47 for comparison, same hacked SSE, although driver tube and operating points will be specific to each type tube
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IMO, 46 is an optimal tube for driving the 300B. Triode connected obviously.
Plate resistance is proper for strong drive (no thanks to the tired AX7 or SN7 drivers) and the tone is right, being direct heated.
As long as you select optimal operating conditions, the distortion is extremely small. It's the 300B output stage and OPT which has all the distortion. If you don't want to spend the bucks on 45's, use the 46.
Plate resistance is proper for strong drive (no thanks to the tired AX7 or SN7 drivers) and the tone is right, being direct heated.
As long as you select optimal operating conditions, the distortion is extremely small. It's the 300B output stage and OPT which has all the distortion. If you don't want to spend the bucks on 45's, use the 46.
if your speakers are sensitive enough, you can simply use the 46 in triode.
I use Tango FE-12s with them.
I use Tango FE-12s with them.
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46 is excellent PP driver for an Aurora style amplifier - it is better in this role than 45 suggested by Lynn Olson. It is also great as AB2 driver. 30-35 mA 250 V would be a sweet spot safe enough WRT plate dissipation power.
BTW, 46 is 47 sans suppressor grid. Triode-connected 47 is pretty much the same as 46, and 47 is not as rare and expensive as 46.
As A1 output tube, 46 has only 1/2 power output of 45, which pretty much limits it's use to headphone amplifiers.
BTW, 46 is 47 sans suppressor grid. Triode-connected 47 is pretty much the same as 46, and 47 is not as rare and expensive as 46.
As A1 output tube, 46 has only 1/2 power output of 45, which pretty much limits it's use to headphone amplifiers.