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Old 16th February 2012, 08:46 PM   #661
generg is offline generg  Germany
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hi Zen Mod,

yes thank you, I understood what Papa said not completely to be honest.....

.....he says he took the Mu only because the R100 has the lower Vgs and the Aleph is not working good with the R100 for this reason.....

or does he say, the Mu is at any case better than the Aleph no matter if you take the R100 or the IRF240..........?

there I feel my bad English........ not understanding fully what he says............
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Old 17th February 2012, 11:35 AM   #662
flg is offline flg  United States
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generg, english is my first language, electonics is my education, and I still don't always fully understand what he is trying to say. I beleive, we are not seeing the forest through the trees?
My take is; N.P. was responding to a question regarding replacing the IXTH6N part with an R100 device. I think he is saying if you want to use the R100, the mu follower topology is easier/better than an Aleph configuration. He only sites the lower Vgs as a reason? He also says that in mu follower the IRF240 does as well as the R100. For that reason why waste $25 on the CCS with an R100 when a $2.50 IRFP240 does as well.
I'm not sure that he is ranking the mu follower higher/better than a similar Aleph circuit
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Old 17th February 2012, 01:02 PM   #663
Zen Mod is offline Zen Mod  Serbia
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Pa is sayin' - if you're making a choice between Aleph CCS and mu - be aware that SS R100 is having lower Ugs (than mosfet) and that's the reason that little bjt in Aleph CCS will be starved ; so - mosfet is preferable

further - in mu , there is no significant difference between SS R100 vs. mosfet , so neither one is preferable from tech/sounding point of view

off course - each of them demands different mu conditions ( values of source resistors)
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Old 17th February 2012, 01:52 PM   #664
generg is offline generg  Germany
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Hello my friends,

Thank you for your explanations and interpretations of the problem I saw....

Zen Mod says that the source resistors must be fitting to the demands of the different MU conditions, that is for sure correct.....

But how to calculate these resistors for R100 or IRF240 or even for the partner for instance the Sk82....?
Yes I saw some formula, very complicated, by the favor of Zen Mod, but it is very difficult to find the data to fill in.....

I think in two weeks I will start again my experiments with the SIT again, in my new experimental environment, and my heatsinks for the testbuildings have arrived......finally!
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Old 17th February 2012, 05:34 PM   #665
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Well your right. The how to calc the necessary R values is the key knowledge we need? The case of the enhancement mode vs depletion mode is also opposite or different. In terms of enhancement mode, R100/IRF240 we need a voltage refrence not self generated, or more precisely generated above the output node. I beleive there is a function in these things where you can approach what the Aleph does with the mu follower type configuration.
I havent been taught or read all this theory yet but it really seems like the depletion mode part is set up for mu follower. Ideally, I believe the Drain of the lower FET should have something like a 1 ohm at the output node, and another 1 ohm to the Source of the top FET if your doing a R085 type mu follower. The Output is between the 1 ohms. The connection to the upper FET source is at the bottom of the 1 ohm. Another member has commented on this and I believ his comment to be valid that the top R shoult be ever so slightly higher value. You would realy need the best H.S. possible to do any better and lower D.F./output Z with the R085 but I think I might be able to pull that off?
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Old 17th February 2012, 06:06 PM   #666
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That would be... the connection to the upper FETs Gate (not source) is at the bottom of the 1 ohm resistors...
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Old 19th February 2012, 03:56 PM   #667
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I've forgotten who I promised this to, but here's the info on the Hammond 193V.

Not bad, and we get a nice efficency boost from the lower DCR iron core. You can put those 24V supplies to use now. I didn't experience any loss of inductance at 2A (or the rated 3A for that matter).

You could even run this one with a 20V supply @ 1.4A for a nice little 7W amp with 2% THD at full power.

No, I haven't listened to them. The measurements are in the pdf. Have fun.
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Old 19th February 2012, 04:40 PM   #668
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michael, thank you again this is a nice simple alternative as i can use the same 18V transformer just running the secondary in parrallele instead of series as you know i'm a big fan of your first version with source resistor and bypass cap. i enjoy it every day , never have a SET tube amp sounding like that! i will try the hammond alternative soon and tell you my findings
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Old 20th February 2012, 01:07 AM   #669
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Here's an idea for any of you who might be interested. A considerable drawback of SE amplifier design (there aren't many) is power supply noise finding its way to the output. That noise includes the obvious rectification artifacts, but even worse any noise generated by power supply capacitance. Electrolytic capacitors are for me the worst offenders in audio. A CCS helps with power supply noise, but adding a CCS introduces complexity and feedback into an otherwise simple, non-feedback amplifier. What to do?

One method is to operate two SIT devices in SE class-A balanced push-pull on the output using transformer loading and a single B+ supply. This would allow full or near-full cancellation of load currents through the two SIT devices, while summing power supply noise on the output. And it allows one to ditch the output electrolytic. The devices, of course, must be operated in balanced mode, which will require a balanced or transformer-fed input.

The resulting circuit departs from pure-SE design, but may offer more by way of benefits than disadvantages for those loving the simplicity of simple circuits.

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Old 20th February 2012, 08:00 AM   #670
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I "tend" to prefer the power supply organized with 2 secondaries and bridges in series and caps filtering each bridge .
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