On Bajazzo TS5411 (http://www.diyaudio.com/forums/analog-line-level/146693-john-curls-blowtorch-preamplifier-part-ii-1642.html#post2734795 ) , global feedback is from output transformer secondary tap, from the same coil that the speaker is driven (typical).
On Bajazzo TS301 and TS105 ( http://www.diyaudio.com/forums/analog-line-level/146693-john-curls-blowtorch-preamplifier-part-ii-1642.html#post2734760 ) global feedback is from output transformer secondary coil. This coil is only to provide the global feedback signal.
The speaker is driven through taps on the primary of the transformer. Quite odd.
It was BV post that made me look closer to the schematics.
On Bajazzo TS301 and TS105 ( http://www.diyaudio.com/forums/analog-line-level/146693-john-curls-blowtorch-preamplifier-part-ii-1642.html#post2734760 ) global feedback is from output transformer secondary coil. This coil is only to provide the global feedback signal.
The speaker is driven through taps on the primary of the transformer. Quite odd.
It was BV post that made me look closer to the schematics.
Yes, it's significant.. (What is the OLG of the driver and output stage.)
Pavel this is the distortion of a single 1/4 watt miniature metal film resistor. It has ninth order distortion all by itself. If you use a bunch of these at closer to rated power in even a preamp operating at 100mV or so I think you could get -80dB of 9th, with even a decent circuit topography.
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So we were talking about keeping emitter followers stable by adding RB to Rb. For the transformer coupled design we are adding not just RB but also some RL to a common collector circuit. What effect does that have?
What happens on an emitter follower if the RB is in parallel with a small capacitor?
What happens on an emitter follower if the RB is in parallel with a small capacitor?
Ed, in case I do not measure such plots on a completed amplifier/preamplifier, then I probably do not have this kind of problems, right? The smallest resistors are metal 0.6W 1%, and none of them is operated at power dissipation close to its rated power. In fact 10x less and more. So I do not see any problem here.
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I would consider this Bajazzo circuit as a reminiscence of 'good ol' days'. Nothing serious for highend design
Pavel,
I assume you don't have the problem,as you understand the issues. But it was surprising to find reputable brands (two of them actually) of resistors that I have seen used in others' circuits do have these properties.
We will disagree about the significance of the "good ol' days" circuit. Using transistors that are considered much worse than today's, the designers got quite listenable sound. I think it is worth looking at what was really going on.
Yes, your position is that if you get rid of all the distortion there are no problems, and that is true. Mine is that in the end you always have to live with some and let us look at what kinds are more acceptable. I also am not sure we are yet making all of the right measurements. For example I think the limited bandwidth of many recordings limits them.
Then there are those who like distortion... look at all the fuzz pedals available!
I assume you don't have the problem,as you understand the issues. But it was surprising to find reputable brands (two of them actually) of resistors that I have seen used in others' circuits do have these properties.
We will disagree about the significance of the "good ol' days" circuit. Using transistors that are considered much worse than today's, the designers got quite listenable sound. I think it is worth looking at what was really going on.
Yes, your position is that if you get rid of all the distortion there are no problems, and that is true. Mine is that in the end you always have to live with some and let us look at what kinds are more acceptable. I also am not sure we are yet making all of the right measurements. For example I think the limited bandwidth of many recordings limits them.
Then there are those who like distortion... look at all the fuzz pedals available!
If it hurts don't do it. Pointing out the result of bad design practice is admirable but some perspective is needed. There are any number of all SMT sound cards with >20dB better performance at full scale out, pre-amps too for that matter.
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DBT? Don't think so.
BTW Ed I found my copy of the Weston Instruments 1950 app guide. It shows at length how they measured power, power factor, etc. with "real" analog meters. I remember you were interested in this, I think. It belongs on Jan's site an amazing document of lost technology.
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ONE MORE TIME !
Distortion is not cumulative !
You may (or not) have ninth order cancel ninth order ...
A friend found an analog true power meter at a flea market. Quite an interesting device. That plus a voltage / current meter would show you wonders. I was good, I didn't kill him for it. Not sure that wasn't a mistake!
DBT! Don't give me no stinking DBT if you can't see the emperor's shiny new clothes you are unworthy. All it takes is three high limit credit cards to prove you can hear -160 artifacts.
I think a case can be made that with typical mismatching of 20 db that distortions of -100 THD are picked up by some listeners.
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Without an inverting stage distortion from the same mechanism is in phase and does add. (Keep in mind double the voltage is only 6 db.) But the third also passing through the second device goes to ninth. If you look at the plot you will see fifth! A result of the second and third.
I find the Telefunken Bajazzo portable radio to be an example of unique engineering and the result of decades of experience in what 'works' and what does not. In previous years, I have had difficulty finding a portable radio or even a small AC powered radio that sounds as good, with the exception of the equally dated KLH mono radio or similar design.
While most of the engineering details may be next to useless to duplicate, in this late age of about 50 years later, from the initial design, it is interesting, at least to me, how 'listenable' this radio is, compared to any reasonably sized competition. I attribute this, myself, to transformers vs ceramic caps for coupling between stages, Germanium transistors, and good loudspeaker design. Still, I would like to know further, what it 'is' with these Bajazzo designs that I like so much.
While most of the engineering details may be next to useless to duplicate, in this late age of about 50 years later, from the initial design, it is interesting, at least to me, how 'listenable' this radio is, compared to any reasonably sized competition. I attribute this, myself, to transformers vs ceramic caps for coupling between stages, Germanium transistors, and good loudspeaker design. Still, I would like to know further, what it 'is' with these Bajazzo designs that I like so much.
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