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Old 29th June 2013, 10:48 AM   #591
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Could not agree more!

Congrats Rod!
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Old 7th July 2013, 12:18 AM   #592
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Hi
I am looking at building a DHT amp using the Coleman Filament Regulators.

I plan to make this amp using the Tubelabs SE (TSE) board, ordered one the other day.

I would like to make the amp work with both 300b and 45 tubes, hopefully without too much effort to switch between the two.

With the TSE, I can change the bias for each tube. B+ of may 320V.
So I just need to worry about the different heater voltages for these tubes.

It looks like the regs are adjustable, so I can adjust them for either tube.
I think I would need to use a 9V, 50VA tranny per the 300b requirement, so the input voltage will be high when using a 45, so I will need large enough heat sinks go compensate for the higher input voltage.

Does this sound reasonable?
Did I miss anything?
Any other comments?

As always, any advice is appreciated.

Randy
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Old 7th July 2013, 05:02 AM   #593
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hi Randy,

the Coleman Regulators can be adjusted for current, and the current-range can be set up for 300B (adjusts 1.1 - 1.4A) or 45 (1.4 - 1.7A) by adding one resistor for the 45.

For the raw dc supply, a transformer with a 7.5V secondary (for 45) or a 9V rms (for 300B) is needed - or the 9V rms winding can be used for both, if an extra 1.5 ohm of series resistance is added to the raw dc while the 45 is in use.

Lots of application information available for filament heating of these DHTs - please send me some email to have copies.
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Old 7th July 2013, 04:57 PM   #594
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Hi Rod
Thanks for the help.

I want to use the same tranny for both tubes, so I will use a 9v tx, and add a resistor for 45 tubes.

Is this OK for the tranny?
Hammond 9v 166m18 tx

I will send a PM about the 300b and 45 app notes.

Thanks
Randy
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Old 17th July 2013, 02:00 PM   #595
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So I received my regs in the mail yesterday, have been figuring out what I need to buy for the raw PS.

Wondering if people have an opinion of CRC versus CLC for this? I can make the space for an inductor, if it improves performance.

I have a balanced power conditioner from BPT that will most likely be feeding this amp.

Randy
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Old 17th July 2013, 03:45 PM   #596
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The CRC will require a different transformer with higher voltage as the voltage drop across the resistor will be higher than the drop across the inductor to achieve the same ripple rejection.
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Old 17th July 2013, 05:27 PM   #597
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Hi Randy,

If you are using a power conditioner, I would hope that common-mode noise will be rejected better than before.

The Coleman Regulator does not usually need extra (differential-mode) ripple-rejection, so CLC will not make much difference, except maybe on very low level stages in phono amps.

However, a plain LC filter has scope to improve the system overall, not due to any effect on the filament supply, but because the choke-input will calm down the peak recharge-pulse currents into the rectifier's capacitor. High recharge pulses can pollute the local mains, if the local network impedance is unfavourable (makes little difference for me, but will be supply dependent).

In practice, a CLC made up of (eg) 10uF MKP at the rectifier, a choke of 10mH, 160mOhm, 5A (Hammond 159ZJ) and 10000uF/35V will be very quiet, and take the recharge current right down.

PSUD2 must be used to design the raw supply, and choose the right transformer.

I usually have some example PSUD2 files for choke-input supplies, if you need them.

I don't think that any of this amounts to major effects - but some folks like to build things the absolute best way possible, and if this is you, a choke-input raw supply is worth a look.
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Old 17th July 2013, 08:02 PM   #598
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Here is the simulation I did in PSUD for a 45.

But, to complicate things, I would like to be able to use either 300b or 45's in the same amp.

I think if I change R1 to 1 ohm, should give around 10v at the 300b load.

BTW, I would rather "overdesign" and not have to worry that I could make it better by adding a LC later.
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Old 17th July 2013, 08:37 PM   #599
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Hi Randy,

For choke-input version please try C1=10uF, rather than 10mF in the PSUD2. The transformer voltage will need to be increased to about 12V, but with only about 2.5A rms capacity.

Comparing the peak currents in (eg IT1 or ID1) will show the potential for what choke-input can offer.
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Old 17th July 2013, 10:06 PM   #600
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What is the voltage input range for a DHT heater for 6B4G,the min and the max voltage?
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