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In Reply to: RE: Sonically, its called the " choir effect ". posted by SteveBrown on December 10, 2016 at 02:29:48
OK, so I think by "smeared" or "Choir effect" people here mean to say that a second signal is produced due to the unmatched delay of the two tube sections?
Essentially adding a delayed signal back to the un-delayed signal which would produce an echo effect? Right?
Yet nobody to date has shown us the output of such a circuit on a scope where a delay would be very obvious!
Can't be measured? I disagree. We can easily measure time differences down to the pico-seconds on commodity bench scopes. Yet in order to hear such a delay, we are talking tens of not hundreds of milliseconds. That's based on our hearing deficiencies.
Furthermore when you consider the physics in tube construction, the standard manufacturing tolerances are magnitudes lower than would be required to produce such a long electrical delay.
This is layman's logic! Plain and simple. There is no evidence of this phenomenon that can be measured and quantified - because it doesn't exist at audio frequencies.
I don't doubt people hear things they don't like when paralleling tube sections. But I have to ask if the circuit parameters have been adjusted for the good old LCR changes the additional tube section makes? because that's most likely what you are hearing.
Follow Ups:
It would be very easy to see if measured, as we can measure far lower time based discrepancies on modern test equipment. Two triode sections paralleled act as a uniform composite device even when not perfectly balanced with respect to current and gain. Look at the very well regarded RCA 2A3 as an example, the dual plates. Those are internally connected paralleled sections and they have no issues produced from that construction technique.
Zarni, by now you have been around here long enough that no physical proof will sway a religious fanatic. Take the stuff you may have read about Dennis Fraker's amps...specifically how some magical new term 'transfer efficiency' or some such dreck allows a 2.3641 Watt amp to run circles around more powerful amps in terms of delivered SPL. Makes no sense...and yet you hear it constantly, with no definition given to this new term...only, 'come hear it'.
Hopefully, belief in such things will result in the expected consequences...LOL
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
On a good state of the art, or close to it high fi sytem, there is an audible difference between a single triode, and two paralleled.
In your example, a common NOS bi plate 2A3 will never match the sonics of a single plate 2A3, such as the original HARP 2A3, and the modern EML versions.
Of course, the original Harp 2A3, and the EMLs have symmetrical filament structures, and large emitting filaments, as does the modern JJ 2A3-40, so that is a very large advantage, over a " W" or "V" shaped filament in the standard NOS bi plate.
But people do hear differences, on better audio implementations, parallel versus a single triode. The only instrument that can detect it, is our ears.
No need to discuss Chinese manufacture 2A3s, they are not good enough. Maybe this " single triode in a bottle " is why people with high efficiency speakers like a 45 over a biplate 2A3. Again, "the" measuring device of-choice is a good hi fi, and the parts on either side of our cranium.
Have fun,
Jeff
I'm not going to debate a possible difference in sound between single triode tubes and paralleled section or paralleled separate tubes. People claim they hear all kinds of subtle differences between this that and the other thing.
I just object to calling the inferior sonic quality "smear". That implies some kind of time based latency across paralleled sections giving rise to the music signal that is different from a pure signal. This makes little sense if you know that the electrons involved in carrying the audio signals are moving close to the speed of light, and hence any time discrepancy from taking one different, but very very short path, is of no consequence to the, relatively, very slow audio signal that eventually is produced in your speakers or headphones. Some people tried to use the same logic with feedback loops and time smear was largely debunked as a source of the lesser quality.
I guess same thing with the filament structure. One might be better than an other, but its not due to a lack of time delay effect because of its symmetry.
Hey, you over simplified it, and your conclusions, theoretical, are bogus in practice. I do not mean to offend you in any way. Really !!
The ear can detect many things, and others will support my observations, it is smearing and it is a choir effect. Your "theory " and reasoning would be correct perhaps, if both tube sections were identical in spacing. They never are !!
1 plus 1 equals 2, not 1.
Jeff
"But I have to ask if the circuit parameters have been adjusted for the good old LCR changes the additional tube section makes? because that's most likely what you are hearing."
When paralleling the two triodes of a 6sn7 does the Miller capacitance go up vs. one triode?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
x
.
Have Fun and Enjoy the Music
"Still Working the Problem"
It goes up but how significant it is depends on the rest of the system.
The preceding stage in my case has output impedance of about 47 ohms and I use a 470 ohm grid stopper. A paralleled 6SN7 has about 8pF of plate to grid capacitance and in the case of using a CCS, a mu of about 20, so about 168pF miller.
I say "about" because the two sections of a 6SN7 don't have the same input capacitance and even with a CCS the mu can vary tube to tube.
So yes it affects the FR but whether it makes a difference is up to the builder and the application.
" So yes it affects the FR but whether it makes a difference is up to the builder and the application."Yes, that's why I brought it up.
If the drive impedance was high and someone switched to parallel from single and noticed a difference in sound, the sound difference could be do to that.
"The preceding stage in my case has output impedance of about 47 ohms"
but not in your case.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 12/13/16 12/13/16
If I were starting an amp from scratch, I might not opt for a paralleled driver. If I were modding an existing amp, I would look at how much effort is is to change the the driver to something completely different. Also, I have a lot of tubes sitting around here that need a home and that could influence the choice. Starting with a blank page, I am liking the 6EJ7 recently. Nice little pentode that sounds good run as is or triode connected.
In the case of the offending 300B amp mentioned in this thread, it started with a 6SJ7 driver, which sucked, so I tried a variety of other octal tubes so I could use the same size socket.
I will say this, a paralleled driver sounds better to me than a cascade whether DC or cap coupled. The extra stage takes more away than the paralleled version adds.
IME, the EL84 is a *VERY* fine signal tube. Very fine indeed...:) High ratio plate/g2 current. Good gm at low g2 voltages( around 100V ), and with a variable g2 voltage responds very well to tuning the tube characteristics to match a chosen plate load.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
I agree. I first was made aware of the EL84 as a driver by an article by Thorsten Loesch. I just copied his version with a 300B and it absolutely is a great driver. It helps that I've got lots of them as well.
I would be very interested in how your latest amps are designed Douglas. You've had some great ideas in the past and I feel that they align with my view more often than not. I haven't done a PP amp for years but I'm thinking that I would like to apply some of the things I've learned to one now. The SE thing is a bit of a dead end for anyone that likes to listen to music at more than background volumes or that enjoys realistic bass. That should stir up the natives:)
hey-Hey!!!,
Another liddle power tube I plan to examine is the 2E24. It is a DH number about the size of a 6V6 and given the performances of other DH tubes ought to work quite well.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
I would not question your electronics acumen and as some suggested there may be places where this works just fine, like bi-plate 2A3s, though I note that single plate versions seem in higher demand. When I've paralleled sections it has only been in driver circuits of SE amps, so my experience is limited to that and yes, the circuits in my case were optimized for things like the reduced Rp, why else do any of this? Maybe "smeared" (my term) is a poor application of language to what my ears perceive. What I've experienced are things like less clarity in placement of instruments and less ability to hear individual instruments- as in the case of massed strings, etc. Makes no diff to me if it is measurable because I do this for the enjoyment of music, not because I'm making precision test equipment or such. So if one circuit sounds better to my ears, that's what I will build and yes I'm quite familiar with the engineering theory behind it all.
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