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Old 2nd December 2003, 09:59 PM   #21
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Strange, I thought I had made this post, but it didn't show up. Here's another try.

One classic marketing technique is to label something with an offensive name thereby making unsuspecting viewers see the product in a negative way without giving much thought. Labelling conventional CFs as Miss Piggy may be this type of technique (although one cannot be certain). Once the viewer agrees to the negative image caused by the label, then the seller offers a better solution, sometimes simply with a better name.

The use of CCSs as loads is a tried and true technique in some circumstances. There is nothing new here. The question is, does adding a CCS to a well designed CF add much to its behavior. My guess is no, not much, if anything. Now, there are probably alot of poorly designed CFs out there which, when compared to something that is loaded and biased correctly, sound like *******.

My question still is why does this design with its CCSs Rk and its bootstrapped plate load sound better or work better than an equivalent, well designed CF? I believe those who say that it does, but I would like to know why since I can't find any discernable reason for this to be so. I want to learn something that I don't know because if I do, I can use it in my future designs.

Improving a design over 20 years seems dubious to me. Tubes have been around for a long time and tube designers of old understood most if not all of what we understand today. There are some new things around, but not much. So what are people actually discovering or improving? My guess is that SS equipment has improved principally because of the continuous improvement and availability of new components (although there have also been advances in design). But, new devices also permit new designs. I would very much like to hear some other opinions about this as I may be quite ignorant on this subject.

Frank, I remember your line amp from a previous thread, but I don't remember which one. Please remind me.

However, I can easily believe that a properly designed WCF will be better than an equivalent CF. It will operate in class A push-pull mode, even harmonics will cancel, Zo will be about half the CF, and current delivery will be double for the same idle current. The price is another triode and a higher B+ (not at all unreasonable with today's components).

Federico, I changed the parameters to match published plate curves better than the originals from Norman. I think my values are a little better, but this depends on how good the published curves are to begin with.
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Old 2nd December 2003, 10:32 PM   #22
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Hi Alex,

Here it is:

FRANK'S ULTIMATE PREAMP.

And another WCF I drew up but never built using one of my all time favs:

Cheers,
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Old 2nd December 2003, 11:31 PM   #23
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Quote:
Originally posted by runeight
One classic marketing technique is to label something with an offensive name thereby making unsuspecting viewers see the product in a negative way without giving much thought. Labelling conventional CFs as Miss Piggy may be this type of technique (although one cannot be certain). Once the viewer agrees to the negative image caused by the label, then the seller offers a better solution, sometimes simply with a better name.
How does that work when the designer publishes the designs, and is happy for people to try them at no fiscal benefit to himself?
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Old 2nd December 2003, 11:34 PM   #24
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Hi,

Quote:
How does that work when the designer publishes the designs, and is happy for people to try them at no fiscal benefit to himself?
It's a technique called "Market penetration".

Not saying this is the case here though...

Cheers,
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Old 3rd December 2003, 01:29 AM   #25
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Quote:
How does that work when the designer publishes the designs, and is happy for people to try them at no fiscal benefit to himself?
A fair question, which Frank has mostly answered. I guess I stepped into this because I want to know why this works, but I don't want to be dis-ing Mr. Wright or his business practices unfairly because I have had absolutely no dealings with his company except through reading the website and seeing what is stated there (and I haven't read everything either). I'm sure there are many satisfied customers given the longevity of the company.

But, to answer the general question, marketeers can do a lot of things that appear to be fair and reasonable and they, in fact, are. At the same time alot of the reasons we buy things are subjective (a very well understood phenomenon). So, the marketeer, while being fair and reasonable, frequently only has give us the subjective impression that what he is selling is actually better. If we believe it and, especially if all else seems quite fair and equal, we may be very inclined purchase the product. And if we do that's all the seller needs us to do. I also believe it is true (but would have to go find supporting research) that allowing a customer to "test-drive" builds a stronger inclination in the customer to buy the product, as he sometimes feels an obligation because the seller has been so reasonable.

So, while I appreciate that all businesses must do good marketing and ( having been in many tech companies) that the marketing department sometimes "embellishes" the product's qualities (in fact I've given some of those presentations myself ), I just want to know why this topology is better than a regular, well designed CF for driving reasonable audio cable and loads. So, instead of calling the regular CF Miss Piggy, I would like the designers to actually tell me why their design is better. OTOH, they clearly don't have to do this for the rest of their customers, so maybe it's just me.

If the answer is simply "try one for yourself and compare", that is an answer and maybe someday I'll have the opportunity to do that. But, even if I say "wow, this is the best preamp I've ever heard driving a 5K/1u load at the end of a 100ft radio shack cable", I'll still want to know "why?" and this particular manufacturer has not, insofar as I have explored the website, answered my question and I cannot figure it out based on what I know. Hence, assuming that the problem is mine, I'm asking for the generous help of those who are far better at this than I am.
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Old 4th December 2003, 12:01 PM   #26
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Quote:
Originally posted by runeight


A fair question, which Frank has mostly answered. I guess I stepped into this because I want to know why this works, but I don't want to be dis-ing Mr. Wright or his business practices unfairly because I have had absolutely no dealings with his company except through reading the website and seeing what is stated there (and I haven't read everything either). I'm sure there are many satisfied customers given the longevity of the company.

But, to answer the general question, marketeers can do a lot of things that appear to be fair and reasonable and they, in fact, are. At the same time alot of the reasons we buy things are subjective (a very well understood phenomenon). So, the marketeer, while being fair and reasonable, frequently only has give us the subjective impression that what he is selling is actually better. If we believe it and, especially if all else seems quite fair and equal, we may be very inclined purchase the product. And if we do that's all the seller needs us to do. I also believe it is true (but would have to go find supporting research) that allowing a customer to "test-drive" builds a stronger inclination in the customer to buy the product, as he sometimes feels an obligation because the seller has been so reasonable.

So, while I appreciate that all businesses must do good marketing and ( having been in many tech companies) that the marketing department sometimes "embellishes" the product's qualities (in fact I've given some of those presentations myself ), I just want to know why this topology is better than a regular, well designed CF for driving reasonable audio cable and loads. So, instead of calling the regular CF Miss Piggy, I would like the designers to actually tell me why their design is better. OTOH, they clearly don't have to do this for the rest of their customers, so maybe it's just me.

If the answer is simply "try one for yourself and compare", that is an answer and maybe someday I'll have the opportunity to do that. But, even if I say "wow, this is the best preamp I've ever heard driving a 5K/1u load at the end of a 100ft radio shack cable", I'll still want to know "why?" and this particular manufacturer has not, insofar as I have explored the website, answered my question and I cannot figure it out based on what I know. Hence, assuming that the problem is mine, I'm asking for the generous help of those who are far better at this than I am.
Hi Runeight,

Don't start showing frustration by discrediting the designers
of this wonderful CF. I know both Allen and Joe, they are very
innovative designers. I have used variations of these followers in
tube and SS circuits myself and they are very transparent.

Your PC modelling obviously misses the finer points of tube
characteristics, better to turn the PC off, take a good look
at some good old fashioned tube data sheets. These followers
DO measure extremely well compared to std CF's. I've measured
them myself with proper tools such as AP and with moderate
loads and voltage swing they can challenge the AP1's residual
if done right.

I recommend checking u versus voltage across tube and u
versus current. In real life the cathode doesn't REALLY follow the
grid because all these parameters change.
The bootsrap makes the follower tube operate in constant
voltage mode and the CCS enables much higher operating
current versus current modulation due to load. All this adds to
LINEARITY. Also in your simulation you forgot to feed the
followers with real world Z of 10k or so.

There's more than meets the eye, so first fully understand the
circuit or email the designers at vacuumstate for an explanation
before theorising about marketing.

Better still, build it and listen to it compared to a std CF.

Cheers,

Terry
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Old 4th December 2003, 11:31 PM   #27
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Hi,

Quote:
There's more than meets the eye, so first fully understand the circuit or email the designers at vacuumstate for an explanation before theorising about marketing.
Certainly.

Let's forget about the marketing aspects here for a moment; I can already come up with a few still manufactured valves that can possibly beat the venerable and over-used 6922 as a CF in the same topology both on paper and sonically.

Whether that will yield even better CFs I'll leave open to debate for the time being but logical thinking tells me it should.

Innovative design is a very relative term in my book, I don't see all that many of those when it comes to valved circuits.

Maybe I missed something but so far, nothing new under the sun I'd say?

Cheers,
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Old 5th December 2003, 02:03 AM   #28
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Terry, thanks much for you thoughtful and helpful reply.

I rather wish that I hadn't gotten off on the marketing tangent, but some number of posts back someone mentioned that the CF was entitled Miss Piggy and I figured I'd seen that movie before.

Nevertheless, I do understand what the circuit is doing and I must admit that I can read plate curves (although less easily as the years go by ). I thought this was quite an interesting combination of ideas (although not really new I don't think) so I decided to simulate it to how it worked in detail. Then I compared it to an ordinary CF at about the same operating condition and I saw no real difference. So, my original post was simply, "I don't see that this works better than an equivalent CF can someone please help me understand why it is better." To which, I got several very helpful replies that didn't seem to think the design was much better, if at all, and some that said I could only really tell by listening to it.

With regard to simulations, I have said many times here that they are not perfect, but they are much better than many give them credit for. The triode models easily take into account the principle effects of changing mu, gm, etc. with operating point. So this behavior would naturally be included in the simulation results without any effort on my part and it would be included quite accurately I believe. I have simulated other published designs where specs and schematics were available, such as some of the Transcendent Sound designs, and I am able to get very good correlation.

So, when I ran the simulated experiment I expected to see much better LINEARITY, but I didn't.

When you compared the measurements, was the ordinary CF at an equivalent operating point with the same Rk? If so, may I ask what the difference in behavior was?

Regarding the real world Z, can I assume you mean that the signal sources should include some source impedance? If so, you are quite correct and I should have done this. Trying the simulations again with a source impedance of 10K, however, seems to make no difference in my results.

Thanks again for this help.
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Old 5th December 2003, 10:46 AM   #29
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Quote:
Originally posted by runeight
Terry, thanks much for you thoughtful and helpful reply.

I rather wish that I hadn't gotten off on the marketing tangent, but some number of posts back someone mentioned that the CF was entitled Miss Piggy and I figured I'd seen that movie before.

Nevertheless, I do understand what the circuit is doing and I must admit that I can read plate curves (although less easily as the years go by ). I thought this was quite an interesting combination of ideas (although not really new I don't think) so I decided to simulate it to how it worked in detail. Then I compared it to an ordinary CF at about the same operating condition and I saw no real difference. So, my original post was simply, "I don't see that this works better than an equivalent CF can someone please help me understand why it is better." To which, I got several very helpful replies that didn't seem to think the design was much better, if at all, and some that said I could only really tell by listening to it.

With regard to simulations, I have said many times here that they are not perfect, but they are much better than many give them credit for. The triode models easily take into account the principle effects of changing mu, gm, etc. with operating point. So this behavior would naturally be included in the simulation results without any effort on my part and it would be included quite accurately I believe. I have simulated other published designs where specs and schematics were available, such as some of the Transcendent Sound designs, and I am able to get very good correlation.

So, when I ran the simulated experiment I expected to see much better LINEARITY, but I didn't.

When you compared the measurements, was the ordinary CF at an equivalent operating point with the same Rk? If so, may I ask what the difference in behavior was?

Regarding the real world Z, can I assume you mean that the signal sources should include some source impedance? If so, you are quite correct and I should have done this. Trying the simulations again with a source impedance of 10K, however, seems to make no difference in my results.

Thanks again for this help.
Hi,

I used AP series 1 with a residual of 0.0005% THD and
have ran distortion tests on both SS and tubed OP stages
with bootsraps and current sources. Both bootstrap and
CCS lower the THD for any given current and it seems
to make more difference at high frequencies and when
driven from 10~20k source. This is particularly true for SS. The
currents are obviously same for all arrangements to allow level
playing field.

I have measured as little as <0.001% THD for this arrangement
when the quiescent current is high and load is not too heavy.

In the scheme of things, I really recommend just building
them and listening to them. If you are after a tubey
sound look elsewhere, transparency is the rule here.


Cheers,

Terry
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