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152.131.10.193
I know about the schematic of the audio note ankoru....but would like a little more information on the proper execution.
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I believe SS is much better suited to this service. You want a full-wave doubler, of course. Each series capacitor sees 60Hz ripple thus make sure the ripple current rating of the cap is up to the job. About any 600-800uF caps usually will be ok for up to a 100-watt or so output power amplifier. The higher the voltage rating usually correlates with higher ripple current capacity.
I like a low DCR choke after a doubler. A cap on the output reduces ripple (hum). Use Dungon Amps PSU Designer II power supply simulator to model your proposal.
Sorry to say that I doubt if a primer on tube voltage doublers exists. Why would anyone write such a thing, when SS diodes are the obvious things to use?
Edits: 12/31/08
hey-Hey!!!,
The tube circuit would work just the same as a SS one. One would need to observe the same device limitations. The SS devices are far more tolerant of the high input capacitance a doubler requires to operate with decent regulation. It de facto rules out tube diodes for best performance. However, HV Schottky diodes deliver the goods w/o needing heater power.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
'Keep it simple' is a good formula. The sonics benefits of tube and no choke vs SS in a doubler with a low DCR choke should result in a better PS with the SS & choke combo. No more expensive and the required chassis space is smaller.
I'll go even further. Use high PIV Schottky diodes in the doubler and SS rectification is better in all categories, except the "SOFT" start damper diodes offer.
Acceptable regulation requires huge value caps., in the doubler stack. No vacuum diode I'm aware of can operate under those conditions. Large doubler stack caps. equate to tiny conduction angles. Tiny conduction angles imply lots of high order ripple overtone energy. Therefore, the low DCR choke and (perhaps) additional "hash" control measures are highly appropriate. Schottky diodes ensure that SS switching noise can't sneak into the amp via heater windings, as the noise doesn't exist to begin with.
BTW, 1 H. is plenty for that low DCR choke. Remember, the primary target is "hash", not the ripple fundamental.
Eli D.
hey-Hey!!!,
The HF is fairly easy to target. The lower inductance/high current chokes are made in such a way as to deliver good HF performance. This is due to less turns and the accompanying capacitance. The lower C leaves a higher self resonant point and thus a wider BW for the choke behaviour( and not the capacitive stuff from post-SRF point ).
I used a secondary HF inductor in series with the ripple-reduction choke in my latest design. Big doubler caps, a 2.5 Hy choke followed by a 1 mHy in series and terminated with a big capacitance. I saw no difference with a small film cap at the node between chokes but left it in anyway...:) For reasonable audio tube finals, B+ is well within the capability of a pair of 600V diodes( B+ at no load of 500V ).
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
.
In fact, I can't tell whether you agree with yourself or not {)
JMO, voltage multipliers are best done with SS, not vacuum, diodes. Anything resembling decent regulation requires the use of LARGE filter capacitors. Caps. large enough in value cause vacuum diodes to arc over, at power on. ;> ( Another consideration is the matter of multiple forward drops.
The suggestion employ damper diodes is as good as it gets, using vacuum rectification, as they are reasonably tolerant of capacitance and exhibit comparatively small forward drops. A pair of 6AU4s, along with 2X dedicated 6.3 VAC heater windings MIGHT yield a satisfactory result.
Eli D.
hey-Hey!!!,
Also examine the heater-cathode ratings. The diode with its plate attached to ground will probably exceed the ratings. The solution to that is a heater supply biased to that voltage( give or take ). That will likely create issues for other tubes in the circuit.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
A solution to that may be to use a pair of single diodes, especially TV dampers like the 6D22S, which allows up to 600v heater-cathode voltage.
and sounded much better than the supplied 1n4007's. This was not a reference amplifier. Certainly not as delivered, it made everything sound the same. I once read it cast a golden glow on everything and I would guess this is as good a way to describe it as there is.
The good old AUDIO CYCLOPEDIA is where I looked for the very little information I used. There is not much to doing it other than observing polarities. I would recommend a separate heater transformer for each of the tubes.
I liked that they offered the slow ramp-up of the B+, too.
In the case of the MD-811 they were asked to produce around 300 volts so the heater/cathode relationship was not a problem.
If one needs to use this, instead of a larger transformer, I would say it is a worthwhile approach.
These tubes give a great science project look to any amplifier. Funny plate cap size, unfortunately.
I have since modded the amplifier into extinction.
Good choice, 6DL3 is even better and quite cheap and reliable. I'm getting over 1000V at 200mA out of them with no probs for years. High capacitance doesn't bother them either.
Cheers,
Naz
Try the PSUD2, freeware on net :)
Happy Ears!
Al
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