This is how I would kill the Baby-Huey
!
The amp will be built with ECL86 and mains toroids as OPTs 9k:8ohm. With EL84 I would go lower and use 6H30 or 6DJ8 as driver.
The local feedback was a total dead-end so it is gone, but feeding from the anodes remains, no decoupling cap needed.
Instead of feedback loops the drivers working-points should be optimized. To get the desired sensitivity(0,5V) the input transformer is connected 2:1CT.
As I like cathoderesistors I will try a biasservo to equal the currents in the toroid. Sims as good as CCS.
I have done quite a few sims to find that cathode-caps to ground will be the first to try.
!The amp will be built with ECL86 and mains toroids as OPTs 9k:8ohm. With EL84 I would go lower and use 6H30 or 6DJ8 as driver.
The local feedback was a total dead-end so it is gone, but feeding from the anodes remains, no decoupling cap needed.
Instead of feedback loops the drivers working-points should be optimized. To get the desired sensitivity(0,5V) the input transformer is connected 2:1CT.
As I like cathoderesistors I will try a biasservo to equal the currents in the toroid. Sims as good as CCS.
I have done quite a few sims to find that cathode-caps to ground will be the first to try.
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Shoog said:
A cathode follower can be more transparent and better sounding than a transformer, if well made.
For years I have been reading ludicrous things about CF, first of all by certain gurus.
It is certain that if you write something really wrong for 100 times and nobody replies then it becomes truth!!
After such brainwashing, now people don't use it because the suspicion is enough to sentence that it is not good...Bahhhhh!
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Shoog said:
Rather limited experience. The CF is like any other topology and does have limitations. If it doesn't work well in a specific situation that means: 1) it has badly designed 2) is not suited for driving that load.
In the latter case at 99% there is some problem with the load whose requests are simply too much....it's a bit like trying to get 20W out a 300B SE, where the request for the driver is 10W output and 300V P-P!!?!
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Welcome to the wonderful world of audiophoolery. There's a whole bunch of folk "wisdom", old wives' tales, and other nonsense out there. Believe may be 50% of what you see, and 25% of what you read, and you can't go too far astray.
This nonsense about CF's got its start with that "all NFB is bad" BS. Someone heard that all CF's have 100% NFB, and took it from there. Of course, they completely ignore the fact that all transistors and VTs have NFB and that there isn't thing one that anyone can do about it (otherwise you'd have infinite gain -- a clear physical impossibility).
More BS to ignore. I include followers where they'll do the most good. So far, no problems.
Allen, see my Heretical Preamp article at my website. Or go listen to a Marantz 9. Or Fisher 50A. Or any of the numerous classic WE power amps that use cathode followers. I experimented with more elaborate buffers in both my power amp and preamp, but didn't find any real difference compared to a well-engineered conventional cathode or source follower.
Have you seen the very elaborate buffer in Horowitz and Hill? It uses all of the Tektronix buffer concepts that you've successfully adapted and adds a few extra twists to them. I personally think that it's overkill and unnecessary for audio applications, but it's an interesting intellectual exercise.
Have you seen the very elaborate buffer in Horowitz and Hill? It uses all of the Tektronix buffer concepts that you've successfully adapted and adds a few extra twists to them. I personally think that it's overkill and unnecessary for audio applications, but it's an interesting intellectual exercise.
Hi SY,
Just curious, haven´t seen any WEs with CFs. Do you have links or schematics. As WE did so many good solution, it would be nice to see how they handled CFs.
.
Hi Allen,
Back to the subject. How does the resistor(68ohm) connected cathode caps sound compared to caps connected with the resistor shorted (ie caps directly to ground)?
Just curious, haven´t seen any WEs with CFs. Do you have links or schematics. As WE did so many good solution, it would be nice to see how they handled CFs.
.Hi Allen,
Back to the subject. How does the resistor(68ohm) connected cathode caps sound compared to caps connected with the resistor shorted (ie caps directly to ground)?
Lars,
>Back to the subject. How does the resistor(68ohm) connected cathode caps sound compared to caps connected with the resistor shorted (ie caps directly to ground)?<
I suggest you try it - hard to tell from a sim...
SY,
Just 'cause some amps using plain CFs sound good to you doesn't mean (to me at least) that they wouldn't sound a LOT better if they used a SLCF.
I have nothing more to say on this matter - I call a plain CF "Miss Piggy" in my TubePreamp CookBook" and have no reason to change that opinion.
Regards, Allen (vacuum State)
>Back to the subject. How does the resistor(68ohm) connected cathode caps sound compared to caps connected with the resistor shorted (ie caps directly to ground)?<
I suggest you try it - hard to tell from a sim...
SY,
Just 'cause some amps using plain CFs sound good to you doesn't mean (to me at least) that they wouldn't sound a LOT better if they used a SLCF.
I have nothing more to say on this matter - I call a plain CF "Miss Piggy" in my TubePreamp CookBook" and have no reason to change that opinion.
Regards, Allen (vacuum State)
I have no intention to offend in what I am about to say, but I think it is pertinent to this debate.
I had the opportunity to listen to Francis Morrans implementation of the RED LIGHT DISTRICT amp at a shoot out. It was up against ECL86 Baby Huey from John Kenny and my transformer coupled 6080 amp. Both mine and Johns amps had issues, but they were both better recieved than the RLD. Now of course there are many factors which may not have made the comparison fair, especially the difficult QUAD ESL speakers which they were driving. The overall impression was that both would have been easier to live with than RLD.
At the same time the Headphone amp been discussed here came out top over three other headphone amps, one commercial and two diy.
However it makes me think that SY's analytical approach may not be the only way to perfection and therefore his firmly held belief and statements aren't to be taken without reservations by me.
Shoog.
It is all about psychology,
There is a "concept", you have good experiences with it (it was better than the other things you tried, your parents/teachers or the pope or a Guru told you that this it the way to go). After this "peak experience" you decide for yourself that this is it, you saw the light. You will stick to it, because it is your "believe" and it gives you a nice feeling.
Than you meet other people, they have different experiences, and thus different believes.
You both think that you have an absolute truth: CF is rubbish, or PP does not sound good, x y z is the only way that works or sprouts tastes bad, .....
You cannot accept that there are more truths, because then you would lose "something". You are certainly not going to experiment with or take even serious the ways of the other party, perhaps you even feel yourself attacked.
This process can connect to a favourite food or brand of beer, or to things of higher importance as cathode followers or followers of certain religions or ways of life.
no intention to be a moralist, just observing the "laws" of how human beings operate, including myself.
What I hope to be true is that every food can be cooked in such a way that everybody can enjoy it. Perhaps sometimes you have to get used to it or go through a learning cycle. But you cannot say that food x or y always is nasty. Al least this is what i tell to my children.
In the same way i do not accept on forehand that a cathode follower or ...... (fill in what you like) can never sound good or is always inferior to ........
There is a "concept", you have good experiences with it (it was better than the other things you tried, your parents/teachers or the pope or a Guru told you that this it the way to go). After this "peak experience" you decide for yourself that this is it, you saw the light. You will stick to it, because it is your "believe" and it gives you a nice feeling.
Than you meet other people, they have different experiences, and thus different believes.
You both think that you have an absolute truth: CF is rubbish, or PP does not sound good, x y z is the only way that works or sprouts tastes bad, .....
You cannot accept that there are more truths, because then you would lose "something". You are certainly not going to experiment with or take even serious the ways of the other party, perhaps you even feel yourself attacked.
This process can connect to a favourite food or brand of beer, or to things of higher importance as cathode followers or followers of certain religions or ways of life.
no intention to be a moralist
, just observing the "laws" of how human beings operate, including myself.What I hope to be true is that every food can be cooked in such a way that everybody can enjoy it. Perhaps sometimes you have to get used to it or go through a learning cycle. But you cannot say that food x or y always is nasty. Al least this is what i tell to my children.
In the same way i do not accept on forehand that a cathode follower or ...... (fill in what you like) can never sound good or is always inferior to ........
This is why comparisons are valid and important. If I had of found the RLD to be superior, then without a doubt I would now have one. I am not personally attached to any belief if the proof of my own ears cast doubt on it.
I do not trust measurements as an arbitor of results, though it obviously can give you valuable pointers.
Shoog
I do not trust measurements as an arbitor of results, though it obviously can give you valuable pointers.
Shoog
Certainly not to offend you !
But this is what my children say when I like them to eat spinach. They tried it, they trust their own judgment and in fact they have the opinion that they know a lot more than their old parents on all possible subjects.
I counter that with the saying that I have more life experience but this is not really convincing to them.
The problem is that you cannot do enough different experiments under all possible circumstances. So you cannot say that you will never like spinach. Perhaps there is a way of cooking spinach that you don't know of yet or haven't tried yet.
So if I hear absolute statements I have my doubts. A scientific theory is only valuable till the next one arrives.
so what about a mosfet cathode follower for a PP ecl82 ?
But this is what my children say when I like them to eat spinach. They tried it, they trust their own judgment and in fact they have the opinion that they know a lot more than their old parents on all possible subjects.
I counter that with the saying that I have more life experience but this is not really convincing to them.
The problem is that you cannot do enough different experiments under all possible circumstances. So you cannot say that you will never like spinach. Perhaps there is a way of cooking spinach that you don't know of yet or haven't tried yet.
So if I hear absolute statements I have my doubts. A scientific theory is only valuable till the next one arrives.
so what about a mosfet cathode follower for a PP ecl82 ?
I fully appreciate what you are saying, but when people say that they can find no measurable difference with a CF and my experience differs I will say so.
I will always be open to different experiences and opinions and when someone shows me a good idea I adopt it. Hence my interest in input transformers - which I was initially dead set again for all the reasons that people role out about their limited band width. The reality seems to be that they went out of favour for reasons of cost.
People tried to convince me that a bit of peaking out at 70kh would be unnoticable - my experience was different so I said so.
The ECL82 sounds harsh because people tend to overload the triode grid - guess what - I try to save them the trouble of repeating my mistake.
Anything I say is derived from comparisons and listening to people who have gained respect and can be trusted to have performed the comparisons so I don't have to. Hence a lot of my work is based on the ideas of Allen Wright, Gary Pimm and Mr Olsen - all highly respected designers.
A lot of people quote from recieved wisdom without testing the alternatives. You Jaap have at least tested new ideas and the hard won experience will result in excellent results.
My design philosphy is keep it simple, avoid negative feedback and extra gain stages.
Unfortunately i cannot comment on the use of Mosfets because I have never used one in this capacity. Tubelabs uses them in his powerdrive circuit and they are well respected in this application. My experience with Mosfet is in the Zen amplifiers which I built as my first project, also in two of those Diy headphone amps I compared. My experience is that they all had a destinct and quite likeable "Mosfet" blush. However these were all in drain followers and source followers are different and not subject to the same capacitancs. So find someone you really respect and follow their opinion, or suck it and see. They may represent a good solution for you to achieve a good transition into class B operation, though I don't know how it will effect the partial feedback - though it will probably work.
Don't listen to anyone least of all me - learn for yourself and chalk up the mistakes to experience.
Shoog
I will always be open to different experiences and opinions and when someone shows me a good idea I adopt it. Hence my interest in input transformers - which I was initially dead set again for all the reasons that people role out about their limited band width. The reality seems to be that they went out of favour for reasons of cost.
People tried to convince me that a bit of peaking out at 70kh would be unnoticable - my experience was different so I said so.
The ECL82 sounds harsh because people tend to overload the triode grid - guess what - I try to save them the trouble of repeating my mistake.
Anything I say is derived from comparisons and listening to people who have gained respect and can be trusted to have performed the comparisons so I don't have to. Hence a lot of my work is based on the ideas of Allen Wright, Gary Pimm and Mr Olsen - all highly respected designers.
A lot of people quote from recieved wisdom without testing the alternatives. You Jaap have at least tested new ideas and the hard won experience will result in excellent results.
My design philosphy is keep it simple, avoid negative feedback and extra gain stages.
Unfortunately i cannot comment on the use of Mosfets because I have never used one in this capacity. Tubelabs uses them in his powerdrive circuit and they are well respected in this application. My experience with Mosfet is in the Zen amplifiers which I built as my first project, also in two of those Diy headphone amps I compared. My experience is that they all had a destinct and quite likeable "Mosfet" blush. However these were all in drain followers and source followers are different and not subject to the same capacitancs. So find someone you really respect and follow their opinion, or suck it and see. They may represent a good solution for you to achieve a good transition into class B operation, though I don't know how it will effect the partial feedback - though it will probably work.
Don't listen to anyone least of all me - learn for yourself and chalk up the mistakes to experience.
Shoog
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