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Old 3rd September 2012, 02:59 AM   #1381
Rush is offline Rush  United States
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Quote:
Originally Posted by buzzforb View Post
Here is MY Franken6. I got most of the way, but alas,not finished. Switched caps to the on hand 220uF. Ill try to throw it together, but things are going to get thick around here for a week or so, so we will see.
Pretty transformers!
Nice wok. The master will be jealous.

Rush
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Old 3rd September 2012, 03:20 AM   #1382
lhquam is offline lhquam  United States
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Is the glass with the ice there to put out the fire?

Quote:
Originally Posted by buzzforb View Post
Here is MY Franken6. I got most of the way, but alas,not finished. Switched caps to the on hand 220uF. Ill try to throw it together, but things are going to get thick around here for a week or so, so we will see.
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Old 3rd September 2012, 04:55 AM   #1383
BudP is offline BudP  United States
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Thanks for that ZM,

I will proceed to provide the putative 2.8kz items. For those who might not understand what Zen and I are poking at here let me post an email response that may give you a better view, or just a headache.

When you have a given load, let's use 1kZ ohm, you must divide that load by 2 x Pi and the frequency you want to extend to. That resultant number is the amount of inductance that the transformer must develop, at that frequency, to provide a -3db roll off from 1kHz.

Then you have to decide where in the power band you want to achieve that frequency roll off. This because core material, at low frequencies, below 100 Hz, gains in it's ability to produce inductance, from rest to full inductance (this is known as permeability, by a factor of 8 for commercial iron manganese core, the M series, to 10 for 48% nickle. The more expensive 80% nickle does not provide more permeability, it just has a steeper slope of onset and less tolerance, by 1/3. for voltage/amperage increase. The most inductance/permeability, for all core material I know of, is found at 27 Hz. Almost all permeability charts are designed to show permeability for 50/60 Hz. There are very few in existence.

Designing these things is either a science, read Jensen, Edcor, Cinemag and many others here, or an art, read Tribute, Intact Audio, Sowter, Lundahl and O-Netics here. The difference in audio between the two groups is much greater than the difference in measurement would lead you to believe, with the nod for music reproduction going to the art group and the nod for specification justification going to the science group. Both approaches are valid.

To obtain a -0.5 db roll off at the frequency and power point you choose you must increase the inductance by 2.76 times the -3db number.

When I say that my Dac Buffer transformers are designed for a 1kZ ohm load in the primary, I am saying that at just off rest voltage, down in the micro volt/amp range, at 20 Hz, I am able to support a -0.5 db roll off. Other designers will choose otherdesign points and criteria when meeting the very same specs.

So, except for Langford Smith showing, in Radiotron Designers Handbook volume three, that the ideal amount of inductance, for lowest distortion is to be limited to twice that needed for -3 db roll off, at frequencies below 100 Hz, exact impedance match is a complete waste of time. So long as you can support the frequency of interest at the power level desired, all other concerns are moot. Unless you go for gaped core of course and apply an appropriate DC bias current. At which point almost everyone throws their hands up in the air and run's away....

My question came about because I do not design or build amplifiers and so am not always certain what is the limiting specification that would disqualify one design from another.

Bud
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Old 3rd September 2012, 08:11 AM   #1384
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Quote:
Originally Posted by lhquam View Post
Is the glass with the ice there to put out the fire?
Safety first!.

Thanks Rush. My wife is jealous

I will be trying one of Buds transformers and will happily share the results. Needless to say, i am feeiling good about the results as he has played with them off and om gor just a couple of years. Sort of like Nelson with amps.
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Last edited by buzzforb; 3rd September 2012 at 08:15 AM.
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Old 3rd September 2012, 11:49 AM   #1385
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Quote:
Originally Posted by buzzforb View Post
Here is MY Franken6. I got most of the way, but alas,not finished. Switched caps to the on hand 220uF. Ill try to throw it together, but things are going to get thick around here for a week or so, so we will see.
Buzzforb: Neat, and a neat build. Did you move away from the Beast of a Thousand Jfets front end?. Are you using CCS's on the main power board? What is your conceptual enclosure going to look like?
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Old 3rd September 2012, 01:16 PM   #1386
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This is just a throw together. Nothing like the original. I am working on a board that will allow for all types of variations on both FE and output, feedback, no feedback. I will not go too far until i have actually heard the thing and see what it sounds like. These are ADC transformers similar to the Jensens, but capable of little more current. BudP's transformers will present an easier load to the FE,being 2K vs 600R, and will just require tweaking on the output. I have CCS on bias section of output feeding LED's. I will play with Salas shunt feeding input pairs 10V vs. Full rail voltage into Joachim's FE vs. full rail voltage and 10R degeneration. Dropping the degeneration resistor lowers the Zout of FE, as well as lowers the noise, but Bud's transformers relieve that problem. Doubling up FE jfets takes care of it as well. Who knows. I just try to avoid making the magic smoke.
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Old 3rd September 2012, 01:40 PM   #1387
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Originally Posted by buzzforb View Post
This is just a throw together. Nothing like the original. I am working on a board that will allow for all types of variations on both FE and output, feedback, no feedback [flexibility, and scope . I hope that you'll have it available in the Store] . I will not go too far until i have actually heard the thing [Franken6] and see what it sounds like. These are ADC transformers [I hope that you'll move them off the heat sink when operating] similar to the Jensens, but capable of little more current. BudP's transformers will present an easier load to the FE,being 2K vs 600R, and will just require tweaking on the output. I have CCS on bias section of output feeding LED's. I will play with Salas shunt feeding input pairs 10V vs. Full rail voltage into Joachim's FE vs. full rail voltage and 10R degeneration. Dropping the degeneration resistor lowers the Zout of FE, as well as lowers the noise, but Bud's transformers relieve that problem. Doubling up FE jfets takes care of it as well. Who knows. I just try to avoid making the magic smoke.
You've put a lot of thought and work in it.
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Old 3rd September 2012, 02:27 PM   #1388
lhquam is offline lhquam  United States
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I hope that there isn't anything flammable in the glass.

Quote:
Originally Posted by buzzforb View Post
Safety first!.

Thanks Rush. My wife is jealous

I will be trying one of Buds transformers and will happily share the results. Needless to say, i am feeiling good about the results as he has played with them off and om gor just a couple of years. Sort of like Nelson with amps.
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Old 3rd September 2012, 03:19 PM   #1389
lhquam is offline lhquam  United States
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Does anyone know what sound Nelson achieved with his F6? Has he managed to create the sound of a class of tube amplifiers using FETs?
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Old 3rd September 2012, 03:54 PM   #1390
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by lhquam View Post
Does anyone know what sound Nelson achieved with his F6? Has he managed to create the sound of a class of tube amplifiers using FETs?
fragment from M2 User Manual , as illustration of line of thinking :

Quote:
So here we have a no-feedback Class A FET power amplifier with transformer voltage gain. Does it have any similarities to no-feedback Class A tube amplifiers with an output transformer? Yes and no.
It does have some of the qualities that SET aficionados look for. The auto-former does bring its own signature to the sound, although in smaller doses than we usually experience. The midrange has a lush, warm character that I associate with tubes and transformers, but subtly so. Part of this is due to the limited bandwidth of transformers, and part of it is the lack of feedback artifacts.
On the other hand, there is considerably less harmonic distortion than with no-feedback SETs, and if you really do like that distortion then the M2 might not be what you want. Also, there is more power than usual and a relatively high damping factor, so the M2 is different in that regard.
The M2 strikes a balance in the performance space between the extremes of big behemoth solid state power amplifiers and little tiny single-ended triodes.
I think you will find the M2 a very pleasant amplifier to listen to. It is relaxed and lively with a slight softness to both the bottom and top frequencies. I hope that you will find as I do that it disappears and leaves the music for you to enjoy. I also hope that it will make you go back through your entire record collection and make you listen to it all over again.
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