Hello
I have several question about 300B SE DIY tube amp.
I have a pair Transcendar 3.5K 10W transformer, a 325ACV power transformer more than enough for a Stereo..
In case if the voltage to low for the 300B I can connect the 100V or 110V primary of the transformer??
I know in that case I will have to use regulator for the heater, because I will get more than 12V..
Do the 300B better with DC or AC heater??
I have a 200VA choke, I think that is enough..
For driver tube I have D3a Siemens , or 6SN7 but what ever circuit I get I can get driver tubes..
I would like to avoid to use a inter-stage transformer..
NOW
All these parts was collected for a GU50 SE amplifier but I changed my mind.
I think from the GU50 tube I never give that quality sound what 300B can offer.
Please correct me if I'm wrong!
Another question if someone can help me a proven great sounding (built and tested not over complicated) circuit for the 300B SE ??
Please help me with that or any advise....
Thank you
Greetings Gabor
I have several question about 300B SE DIY tube amp.
I have a pair Transcendar 3.5K 10W transformer, a 325ACV power transformer more than enough for a Stereo..
In case if the voltage to low for the 300B I can connect the 100V or 110V primary of the transformer??
I know in that case I will have to use regulator for the heater, because I will get more than 12V..
Do the 300B better with DC or AC heater??
I have a 200VA choke, I think that is enough..
For driver tube I have D3a Siemens , or 6SN7 but what ever circuit I get I can get driver tubes..
I would like to avoid to use a inter-stage transformer..
NOW
All these parts was collected for a GU50 SE amplifier but I changed my mind.
I think from the GU50 tube I never give that quality sound what 300B can offer.
Please correct me if I'm wrong!
Another question if someone can help me a proven great sounding (built and tested not over complicated) circuit for the 300B SE ??
Please help me with that or any advise....
Thank you
Greetings Gabor
The Solen capacitors are excellent. I'd stick with that. As others have pointed out, you'll probably need a C-L-C filter to get the hum down -- or do what I do and use a voltage regulator. The 21st Century Maida Regulator I built (see my website) works very well with my 300Bs.
Finding an electrolytic can that can take 600 V is a bit of a challenge. There are some 500 V types out there, but most top out in the 400~450 V range. You can always use two in series, provided that you add a ballasting resistor across the capacitor. You'll need the resistors to bleed off the charge when you turn the amp off anyway, so there's no harm in this.
I tend to run my 300B fairly hot. 85 mA, 400 V or so. This requires a transformer with about 320~330 V RMS AC out. If you're using a voltage regulator, you'll need a bit more voltage as some voltage is dropped across the regulator. This assumes that you're using fixed bias and have the 300B cathode at ground potential. If you're using cathode bias, you'll have to add 70-ish V to that, which, would require a transformer that puts out 380~400 V.
I always use DC heaters (see regulators for this on my website) as DC heating is the best way to avoid hum in directly heated triodes.
~Tom
Finding an electrolytic can that can take 600 V is a bit of a challenge. There are some 500 V types out there, but most top out in the 400~450 V range. You can always use two in series, provided that you add a ballasting resistor across the capacitor. You'll need the resistors to bleed off the charge when you turn the amp off anyway, so there's no harm in this.
I tend to run my 300B fairly hot. 85 mA, 400 V or so. This requires a transformer with about 320~330 V RMS AC out. If you're using a voltage regulator, you'll need a bit more voltage as some voltage is dropped across the regulator. This assumes that you're using fixed bias and have the 300B cathode at ground potential. If you're using cathode bias, you'll have to add 70-ish V to that, which, would require a transformer that puts out 380~400 V.
I always use DC heaters (see regulators for this on my website) as DC heating is the best way to avoid hum in directly heated triodes.
~Tom
I saw the page and everything seems fine, but you have to cc
work and the AC voltage is 6.3v no load, I rectified and a
bridge rectifier and a capacitor-50V 3300UF with 5 + - 5.15v DC
as it is connected to the circuit and the improvements are good.
by the way I put it back and takes away the Solen capacitor by Sprague
electrolytic 40uf-500v axial.
a greeting
work and the AC voltage is 6.3v no load, I rectified and a
bridge rectifier and a capacitor-50V 3300UF with 5 + - 5.15v DC
as it is connected to the circuit and the improvements are good.
by the way I put it back and takes away the Solen capacitor by Sprague
electrolytic 40uf-500v axial.
a greeting
Last edited:
Miguel please do not post multiple threads on the same topic, I have merged the second thread you created with your original.
I would go with the Solen. The're incredible bang for the buck in the polypropylene category.
~Tom
Hello
Good to know 400 or 4250V enough for the 300B. I saw couple circuit but over 500V or 550V.
From my 325V-AC I can get 400-425VDC even if I use a choke, 65Ohm.
To me the Solen capacitor to me sound very dark, muddy flat (missing some dynamics).
I purchased a set for a 3way X-over, I lost a lot of money on them.
I compared some of them in my amplifier and another speaker I sold them all.
Also I tried the white Solen caps - I don't like them, sound very thin.
Of course some poly caps compare to the electrolytics way better.
If you can get Mundorf or something similar category that would be better.
I'm not a big fan of Solen after I tested them (lost money on them).
There are better capacitors out there for that money.
Greetings Gabor
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