Leolabs said:
Tyimo said:
Never mind the theory, seems far fetched to begin with. You can't make it DC coupled easily even with a dual power supply because of the DC voltage in the inductor and corresponding voltage drop. Of course, in the bridged versions there is no cap, which kind of makes one wonder about this INPOL stuff, no?
Personally, I tend to immediately distrust a designer who patents a trivial circuit. Choke loaded followers have been around since the beginning of the vacuum tube era, so there is a 'bit' of prior art there
Luke,
To my knowledge in Oz or NZ no 120mH DCR1R 4A continuous audio choke is available off the shelf. You must build your own. But if you use grain oriented silicon steel and find a competent winder it is not rocket science to have one made.
Start with transformer winders with an audio bent.....
Cheers,
Hugh
To my knowledge in Oz or NZ no 120mH DCR1R 4A continuous audio choke is available off the shelf. You must build your own. But if you use grain oriented silicon steel and find a competent winder it is not rocket science to have one made.
Start with transformer winders with an audio bent.....
Cheers,
Hugh
Luke,
No, not common. But if audio signals are the go, GOSS is the only way to get the headroom at moderate size so necessary in audio. A physically smaller choke will also keep the DCR down; it reduces copper, which you need for such a big inductor.
Most power transformers are wound close to flux saturation, typically 1.4 tesla. GOSS will almost double that, keeping size down and headroom up. And of course, you will have a standing current of three or four amperes, so you need all the advantages you can find.
Try Paul Voller, at 39 Advantage Rd, Highett, VIC 3190. Phone 61 3 9553 3222. He winds for mining companies mostly, but does all my trafos and is outstanding. Shipping will be expensive though.
Hope this helps,
Hugh
No, not common. But if audio signals are the go, GOSS is the only way to get the headroom at moderate size so necessary in audio. A physically smaller choke will also keep the DCR down; it reduces copper, which you need for such a big inductor.
Most power transformers are wound close to flux saturation, typically 1.4 tesla. GOSS will almost double that, keeping size down and headroom up. And of course, you will have a standing current of three or four amperes, so you need all the advantages you can find.
Try Paul Voller, at 39 Advantage Rd, Highett, VIC 3190. Phone 61 3 9553 3222. He winds for mining companies mostly, but does all my trafos and is outstanding. Shipping will be expensive though.
Hope this helps,
Hugh
Hi Luke,
Sure - voller -at- iprimus.com.au
My suggestions (having done just this a couple of years back):
Inductance (gapped, at 3A): 100mH
DCR: 1 ohm
Laminations: EI, Grain Oriented Silicon Steel
Paul will understand the requirements; sectioning will be required to minimise leakage capacitance.
These specs will give you a 6dB response into a nominal 8R load at around 13Hz. (This is 3dB down at 16Hz, close enough for government work!!) The upper frequency response point should be around 25KHz - that's adequate.
This is a serious piece of choke, around the size of a 500W mains transformer, and will cost around $AUD250. You'll need two, of course. This is quite a commitment!
If he has any problems, ask him to call me. We are good mates!
Cheers,
Hugh
Sure - voller -at- iprimus.com.au
My suggestions (having done just this a couple of years back):
Inductance (gapped, at 3A): 100mH
DCR: 1 ohm
Laminations: EI, Grain Oriented Silicon Steel
Paul will understand the requirements; sectioning will be required to minimise leakage capacitance.
These specs will give you a 6dB response into a nominal 8R load at around 13Hz. (This is 3dB down at 16Hz, close enough for government work!!) The upper frequency response point should be around 25KHz - that's adequate.
This is a serious piece of choke, around the size of a 500W mains transformer, and will cost around $AUD250. You'll need two, of course. This is quite a commitment!
If he has any problems, ask him to call me. We are good mates!
Cheers,
Hugh
Hugh thats very helpful, thank you for that.
That is rather expensive though and if I decide to build it, it will be in a few months. I have started my KSA100MKII
I guess I would just need 4 power supplies, B+ 12V for valves, 38V for output stage and 7.5V bias?
Ideally it would be a monoblock too as ther is a lot of stuff to fit in this amp I guess.
regards Arthur
That is rather expensive though and if I decide to build it, it will be in a few months. I have started my KSA100MKII
I guess I would just need 4 power supplies, B+ 12V for valves, 38V for output stage and 7.5V bias?
Ideally it would be a monoblock too as ther is a lot of stuff to fit in this amp I guess.
regards Arthur
O.K. now that we are done with the Christmas blitz, and before this thread dies... I'm interested in a Nelson Pass ZV9 type circuit with an inductor load(O.K. not exactly on thread but...) http://www.diyaudio.com/forums/showthread.php?s=&threadid=91922&highlight= . That would be a Common Source type amp. My experimentation shows 500VA+ Power Transformer primaries to work just fine in the high frequency domain(mostly the EI types)??? Even with small amounts of feedback. It's the low frequency area, as you might expect, where I see the problems... I've got my eye on a couple Hammond 195T5 power supply chokes as my next test load (55-60 $$$ USD Ea.)... What would be wrong with that? They are rated up to 5 Amps at 100mH and I'm only interested in 2-3 Amps...
Any comments that may guide me and the rest of you
Thanks
Any comments that may guide me and the rest of you
Thanks
Gargantuan gravedig!
Dredging through old HFN/RR mags and came across the twin towers review which got me to thinking...
Searched INPOL and found this...
SE MOSFET output stage with a choke load and cap coupled doesn't seem that revolutionary. Pretty much just a Pass Zen but with a choke instead of a CSS.
Can choke load a tube in SE, how was this deemed to be such a leap?
(or were they just the first to ask for a patent)
Dredging through old HFN/RR mags and came across the twin towers review which got me to thinking...
Searched INPOL and found this...
SE MOSFET output stage with a choke load and cap coupled doesn't seem that revolutionary. Pretty much just a Pass Zen but with a choke instead of a CSS.
Can choke load a tube in SE, how was this deemed to be such a leap?
(or were they just the first to ask for a patent)
Drew,
The INPOL patent is simple. Choke loading is almost universal in tube technology, though impedance transformation requires a transformer, but from the tube POV, much the same thing.
The question seems to be: How far can the choke punch above (or below, depending on the gender of the active device) the rail?
I generally count on punching to about 160% of rail voltage on a tube; this is all that's needed, as one is limited at the negative downswing by the saturation voltage of the tube, but with a mosfet this is more serious since Vsat is far, far lower.
IOW, how can we store sufficient energy in the choke to drive a load to well beyond the rail. Answer: more inductance, less DCR.
At least with the mosfet/choke combination you don't need to worry too much about leakage capacitance, since the active device has such low impedance.
Hugh
The INPOL patent is simple. Choke loading is almost universal in tube technology, though impedance transformation requires a transformer, but from the tube POV, much the same thing.
The question seems to be: How far can the choke punch above (or below, depending on the gender of the active device) the rail?
I generally count on punching to about 160% of rail voltage on a tube; this is all that's needed, as one is limited at the negative downswing by the saturation voltage of the tube, but with a mosfet this is more serious since Vsat is far, far lower.
IOW, how can we store sufficient energy in the choke to drive a load to well beyond the rail. Answer: more inductance, less DCR.
At least with the mosfet/choke combination you don't need to worry too much about leakage capacitance, since the active device has such low impedance.
Hugh
true, the downside is having a chunk of iron that won't saturate under SE conditions given the current being pulled through the inductor.
Current is small in tube output stages, usu sub 100mA, in INPOL you're talking multiple amps (which imposes a practical limit on the current that can be delivered to the speaker load on peaks)
Simple, yes. Elegant? Not sure... Guess it's no worse than an output tranny (if one ignores the coupling capacitor)
Hmm, guess you could put an 8 ohm winding on the choke and do away with the cap... Would it make things better or worse?
(of course that just makes it a PSE output stage with mosfets instead of tubes)
Current is small in tube output stages, usu sub 100mA, in INPOL you're talking multiple amps (which imposes a practical limit on the current that can be delivered to the speaker load on peaks)
Simple, yes. Elegant? Not sure... Guess it's no worse than an output tranny (if one ignores the coupling capacitor)
Hmm, guess you could put an 8 ohm winding on the choke and do away with the cap... Would it make things better or worse?
(of course that just makes it a PSE output stage with mosfets instead of tubes)
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