Paramount 220v version
- Thread starter Demsy
- Start date
Paul Joppa
Moderator
Sorry for the delay; several of us have been absent off and on and out communication is a little haphazard!
I have given Doc B a draft writeup which he will probably post on the site once we are all agreed it's satisfactory. Meanwhile, for the specific problem of a Paramount on 220v, the best solution is fairly simple:
1) Wire the filament power choke as if it were for a 2A3. This will reduce the DC resistance from 0.6 ohms to 0.15 ohms, raising the voltage about 0.55v. The exact change depends on some uncontrollable variables such as the amount and type of distortion on the power line voltage.
2) It will also increase the hum a bit; if this is a problem you can place a 10000uF/10v to 16v cap across the output of the choke (positive to choke terminal 6, negative to terminal 1). This capacitor can be used with any Paramount to reduce the very small residual filament hum.
I have given Doc B a draft writeup which he will probably post on the site once we are all agreed it's satisfactory. Meanwhile, for the specific problem of a Paramount on 220v, the best solution is fairly simple:
1) Wire the filament power choke as if it were for a 2A3. This will reduce the DC resistance from 0.6 ohms to 0.15 ohms, raising the voltage about 0.55v. The exact change depends on some uncontrollable variables such as the amount and type of distortion on the power line voltage.
2) It will also increase the hum a bit; if this is a problem you can place a 10000uF/10v to 16v cap across the output of the choke (positive to choke terminal 6, negative to terminal 1). This capacitor can be used with any Paramount to reduce the very small residual filament hum.
Demsy said:
I would recommend trying the choke rewiring. If it does elevate the hum, then pop the cap across the output of the choke. (10,000uF/16V)
Paul Joppa
Moderator
With 105dB speakers (!) I would certainly add the capacitor. It will then be much quieter than the normal (240v) stock build.
In the proposal I made (the draft article) I tried to avoid using complicated or difficult modifications. The suggested mod will work well *5.00 +/- 2.5%) for voltages in the range 220-230 volts. There are different versions for 230-240v and 240-250v, and the stock circuit is excellent at 250-260v. In my opinion greater precision is not warranted in light of fluctuations in available power.
In the proposal I made (the draft article) I tried to avoid using complicated or difficult modifications. The suggested mod will work well *5.00 +/- 2.5%) for voltages in the range 220-230 volts. There are different versions for 230-240v and 240-250v, and the stock circuit is excellent at 250-260v. In my opinion greater precision is not warranted in light of fluctuations in available power.
Paul Joppa
Moderator
No, the 2A3 is different and more complicated.
Sorry to hijack this thread, but I'm about to assemble my Paramount 240V 300b kit and I'm more or less in the same situation. Our line voltage here can be stabilized at 220V +/- 5V with a voltage regulator and based on what I have read here it's not ideal for the Paramount kit.
How should I proceed with my build? Should I follow PJ post here, wiring the the choke using the 2A3 scheme and add in the caps later if necessary? Anything else I need to worry about? What should I expect for the resistance and voltage measurement?
Thanks!
How should I proceed with my build? Should I follow PJ post here, wiring the the choke using the 2A3 scheme and add in the caps later if necessary? Anything else I need to worry about? What should I expect for the resistance and voltage measurement?
Thanks!
Paul Joppa
Moderator
The stock circuit, with a 300B, is +/-5% over the range 235v to 260v. The rewired choke is optimal in a 300B version at 225v input, and within +/-5% over the range 215 to 235v.
