Capacitance multiplier: which Darlington to choose?

[thor.zmt]

We agree far more than disagree

I suspect so.

THD was adequate for characterizing magnetic tape path linearity. SMPTE IMD was adequate for back when 7kHz was considered a HF (long ago).

Indeed. THD is sufficient to charaterise simple systems (e.g. electromechanical transducers or single ended class A circuit without looped feedback.

In my judgement this "good sound" metric is still subjective so different listeners will be focussed on different sonic characteristics. Some may even prefer more euphonic distortions.

Aphex anyone (I love subtle use of Aphex)

I have seen plenty of these "new" distortion metrics promising to zero in on some intangible sonic flaw. They came and left because at the end of the day it comes down to simple linearity (output is same as input just amplified).

No amplifier is truly linear. And modern multistage looped feedback amplifiers in class B/AB/D have peculiar nonlinearities that are really problematic.

Of course with your experience designing power amps you know there are plenty of other ways to drop the ball. Several are involved with recovery from overload conditions (clipping, current limiting, slew limiting, etc).

Yes, plentiful gotchas, but despite them we can have such an Amp give 0.005% THD at 1/2 rated power.

Almost time for me to start shooting squirrels up in my pecan trees, coming soon.

Gut Kimme und Korn!

Thor

 

[JohnRoberts]

Aphex anyone (I love subtle use of Aphex)

I am not a big fan of adding distortion. Perhaps they were a little heavy handed when it was the new thing. I would find myself trying to tune in the radio station better to reduce the excess distortion. I really ticked off the inventor in my "Audio Mythology" column when I called it a fuzz box. He wrote a letter to the editor complaining, but since I was a regular columnist I got to respond to his letter in print. I tried to be my normal gracious self, as usual.

No amplifier is truly linear. And modern multistage looped feedback amplifiers in class B/AB/D have peculiar nonlinearities that are really problematic.

Being able to hear stuff can be a curse. I hear more annoying stuff in the productions, TV and movies... I don't listen to much new music.

Yes, plentiful gotchas, but despite them we can have such an Amp give 0.005% THD at 1/2 rated power.



Gut Kimme und Korn!

Thor

I have a scope on my air rifle. At my age I am not a great shot but have planted my share of squirrels over several years.

JR

 

[thor.zmt]

I am not a big fan of adding distortion. Perhaps they were a little heavy handed when it was the new thing.

Yes. I like to use it for club Sound systems. Not at home.

I would find myself trying to tune in the radio station better to reduce the excess distortion.

I fitted AFC to the tube fm tuner in our "Dampfradio"...

I really ticked off the inventor in my "Audio Mythology" column when I called it a fuzz box.

It is kind of a fuzz box. Used right, everything sounds more dynamic and louder, without more SPL.

Being able to hear stuff can be a curse. I hear more annoying stuff in the productions, TV and movies... I don't listen to much new music.

I'm an "switch off" critical listening on demand.

I have a scope on my air rifle. At my age I am not a great shot but have planted my share of squirrels over several years.

Yeah, I have a laser and red dot on my .22 cal vermin pistol. The critters don't stand a chance. From the hip.

There is a 'sope on the rifle, but 8mm Mauser is overkill for the usual pests. Or most things at that. And not that cheap. But at least it's not an AR-15. That would be scary.

Thor

 

[JohnRoberts]

It is kind of a fuzz box. Used right, everything sounds more dynamic and louder, without more SPL.

thus me calling it a fuzz box...

I'm an "switch off" critical listening on demand.

I try to dull my perception with beer. I find the splicing noise from poorly executed time compression/expansion (to squeeze in more commercials) pretty annoying.

Yeah, I have a laser and red dot on my .22 cal vermin pistol. The critters don't stand a chance. From the hip.

I would be apprehensive about using a laser dot with real bad guys. That kind of shows them where you are.

There is a 'sope on the rifle, but 8mm Mauser is overkill for the usual pests. Or most things at that. And not that cheap. But at least it's not an AR-15. That would be scary.

The M-16 they issued me when I was drafted used open sights. Indeed that would be over kill for varmints. I have no trouble getting them to take the dirt nap with my .177 Gamo air rifle, if I can manage to hit them center mass. My "squeeze the trigger" discipline is sorely lacking these days.

JR

Thor

 

[thor.zmt]

I would be apprehensive about using a laser dot with real bad guys. That kind of shows them where you are.

Hence the red dot. Mind you, I'd probably not use .22 with real bad guys either, except silenced, point blank from behind to the head, in wich case laser or red dot are superfluous.

Same time, .22LR gets them varmints just dandy.

The M-16 they issued me when I was drafted used open sights.

I trained with Dragunov, I prefer optics and a good standoff distance to customers.

Thor

 

[ruffrecords]

The schematics of the .1 series are standard Mullard, the same as used other british marques. They have the same distortion as other amplifiers using the same design. There is nothing in the .1 series that makes it lower distortion than other products on the market using the same Mullard designs.

Interesting. The Mullard circuits were first published in 1959. Leak launched their type 15 amplifier, which became known as the original point one amplifier, a full 10 years earlier in 1945 and it used a pair of KT66 just like the Williamson circuit (published in 1947 two years after Leak launched the type 15) which also aimed for 0.1% distortion.

The Mullard circuit uses the EL84 which did not appear until 1955. The Leak TL/12, still using KT66 tubes, was launched in 1948. You can clearly see them in the picture you posted. It seems to me the Mullard circuits were based on the Leak and Williamson circuits rather than the other way round. Sure, Leak updated their designs to use more modern and cost effective tubes but who wouldn't.

What is different is that nominal output levels / power are lower than Mullard Spec and Distortion is also lower. The Mullard 5-10 actually was rated at 14 Watt & 1% THD, Leak TL12 which is essentially identical was rated at 10 Watt & 0.1% THD.

And this low distortion (which is the same as any other product using the same design) is advertised.

Not really. The Williamson stated clearly that it achieved 0.1% at its rated output of 14 watts.

Cheers

Ian

 

[Walter66]

Gentleman,
this is a Shindo Aurieges PSU circuit. For the transistor, can an IRF 830 be applied here, too? Or is there a better solution?

 

[thor.zmt]

this is a Shindo Aurieges PSU circuit. For the transistor, can an IRF 830 be applied here, too? Or is there a better solution?
View attachment 109681

Can be used, as said, as a minimum 1K gate stopper and the 15V zener is recommended.

The 220uF can be omitted. The time constant of RC looks like 23 seconds. So 820k -> 18M, 120k -> 2M7, C = 10uF (film).

Thor

 

[thor.zmt]

Interesting. The Mullard circuits were first published in 1959. Leak launched their type 15 amplifier, which became known as the original point one amplifier, a full 10 years earlier in 1945

Did anyone ever see one? Is there a photo or schematic?

and it used a pair of KT66 just like the Williamson circuit (published in 1947 two years after Leak launched the type 15) which also aimed for 0.1% distortion.

Williamson was not a commercial product claiming low HD for marketing.

It was presented as "high fidelity" design and used a test of jangling keys in front of a microphone and played back via the Amplifier (amongst other tests such as pipe organ music) to validate fidelity.

Not really. The Williamson stated clearly that it achieved 0.1% at its rated output of 14 watts.

So it did. And?

It does not change that low distortion as measure of fidelity as actual marketing macguffin goes back to Leak and was done using generic circuits that were simply rated at a lower power output than the competition, who rated power ay 3% or 10% which remained common practice for decades longer, into the solid state era where 3% or 10% THD at rated power were no longer appropriate.

Thor

 

[JohnRoberts]

Williamson was not a commercial product claiming low HD for marketing.

well known, I am not a tube guy and I have heard of his work (also in radar RF during WWII).

It was presented as "high fidelity" design and used a test of jangling keys in front of a microphone and played back via the Amplifier (amongst other tests such as pipe organ music) to validate fidelity.

The jangling keys is popular test for HF IMD. Jangling keys can generate content an octave above the typical 20kHz upper limit.

So it did. And?

It does not change that low distortion as measure of fidelity as actual marketing macguffin goes back to Leak and was done using generic circuits that were simply rated at a lower power output than the competition, who rated power ay 3% or 10% which remained common practice for decades longer, into the solid state era where 3% or 10% THD at rated power were no longer appropriate.

Thor

Various metrics have been used in marketing... for a while slew rate was a focus until that reached ridiculous extremes.

JR

 

[JohnRoberts]

Dragunov

I am not familiar with old soviet union sniper rifles... the AK47 was more popular during Viet Nam conflict.

The M16 was not a precision weapon, the only good thing about it was relative light weight. The mechanism was so likely to jam it had a forward assist push mechanism designed in.

JR

 

[thor.zmt]

I am not familiar with old soviet union sniper rifles... the AK47 was more popular during Viet Nam conflict.

More DMR than sniper.

What I liked was that you can use the armor piercing rounds from the heavy Russian machine gun. Good if critters try hiding behind cover or wear bod armor (body armor wearing squirrels!? ).

Plus, it's straight recoil and has a great reticle on the scope that lets you instantly judge range to target and engage. Instant follow up shots, when I was a lot younger, three rapid shots at 500m in a close group.

Thor

 

[JohnRoberts]

I had to search DMR (designated marksman rifles), sounds like a sniper rifle.

I was never in the sh__ myself, but I met a guy who was a LRRP (long range reconnaissance patrol), aka sniper over in the Nam. AFAIK the US "designated marksmen" preferred older M14s as more accurate weapons than the M16s. The light weight M16 rounds could be deflected by jungle vegetation in Viet Nam's jungle while the heavier M14 rounds flew truer.

Soldiers in later military actions were outfitted with more sophisticated dedicated weapons for long range marksmanship.
===

I was a good enough shot to easily qualify (I grew up with a .22 long rifle in the house for killing woodchucks)... I was a squad leader during basic training and one of my squad was a horrible shot. While at the rifle range to qualify I put good shooters on either side of him, and had them each drop one or two rounds into his target. It worked well enough to get him qualified to graduate from basic training.

JR

 

[Walter66]

Gents, could this be one of the first cap multipliers /choke emulators? IRT V81 from 1964.

 

[abbey road d enfer]

Gents, could this be one of the first cap multipliers /choke emulators? IRT V81 from 1964.

That's exactly what it is. The schemo looks somewhat confusing because of the use of PNP transistors (probably Germanium), but it's a simple capacitance multiplier.

 

[Walter66]

Thank you. TF80/60 had a Beta of approx. 50 in this circuit, think thats enough for good filtering of the push pull output stage of this 10W power amp.
Is there something better available today with bipolar transistors?

This isn't a high voltage type, but it's employed in a high voltage PSU. Has this been achieved because it's placed in the negative part of the PSU?
Can someone use a modern type of PNP low voltage transistor and replicate this PSU for a tube amp easily?
Does this type of transistor in general eliminate the need for a high voltage bipolar transistor in tube amp PSU? It would have been a clever idea.

 

[thor.zmt]

I had to search DMR (designated marksman rifles), sounds like a sniper rifle.

Well, kinda like an AR-15 is an assault rifle, I guess.

The Drag is meant for rapid and reliable engagement of high value targets out to 600m with a high first round kill probaility. It's very much a battle rifle with good optics.

You don't sit around in a ghillie suit peeing into a bottle for days waiting for a target.

I was never in the sh__ myself,

I managed to be stupid enough to do it for cold hard cash. Decided after a while that the money is too hard earned and too dirty. Mind you, paid me through my second degree and down payment for a house.

but I met a guy who was a LRRP (long range reconnaissance patrol), aka sniper over in the Nam. AFAIK the US "designated marksmen" preferred older M14s as more accurate weapons than the M16s. The light weight M16 rounds could be deflected by jungle vegetation in Viet Nam's jungle while the heavier M14 rounds flew truer.

Yeah, in the WarPac we had the 5.45mm Soviet round in the AK-74. Similar story, soft shooting, lighter and probably better for relatively unskilled groundpounders to get roundx on target. But fairly weak results at distance.

Now armorpiercing 7.62mm x 54mmR is a different proposition. It will go through fairly thick steel at 500m. Accurate enough to hit the steel.at 500m too.

Of course major over penetration and overkill for home defense and to keep pigeons sh!tting all over my garden. At 20m there will be nothing left of the poor critter and instead of a little dent on the 'crete there would be a new ventilation hole in the wall.

Soldiers in later military actions were outfitted with more sophisticated dedicated weapons for long range marksmanship.

WarPac after the Russian experience in WW2 had a DMR on squad level. Plus SAW (Squad Automatic Weapon = light machine gun) and anti tank/fortified position RPG (Bazooka).

And mounted on an armoured tracked personel carrier packing a 4" cannon, machine gun and Sagger anti tank missiles.

At least on paper it gave a standard WarPac squad a lot of native capabilities in field. Shame that most of the cannon fodder was not good for more than that. Better motivation and leadership, the WarPac armies should have been seriously scary. The gear was pretty decent.

I was a squad leader during basic training and one of my squad was a horrible shot. While at the rifle range to qualify I put good shooters on either side of him, and had them each drop one or two rounds into his target. It worked well enough to get him qualified to graduate from basic training.

In some ways good leadership. I hope he improved later. Otherwise, in the field he would have been a liability.

Better for him to wash out early than to be killed because in the field you could not sent two others along with him to take care of his targets.

War sux. I wish they would stop this stupid war business. But until then defense is sadly neccessary.

Thor

Thor

 

[abbey road d enfer]

Thank you. TF80/60 had a Beta of approx. 50 in this circuit, think thats enough for good filtering of the push pull output stage of this 10W power amp.
Is there something better available today with bipolar transistors?

No doubt you can get better performance from almost any modern Si transistor.

This isn't a high voltage type, but it's employed in a high voltage PSU. Has this been achieved because it's placed in the negative part of the PSU?

No. In permanent regime, the voltage across the transistor is low enough, but during the initial charge phase, the C-E and C-B voltage could be very large. This seems very risky to me. However it seems the test of time has proved it works. I don't know for sure what mechanism is at work here.
I can only speculate that the C-B junction goes in avalanche, thus reducing the voltage to a sustainable level. It seems the 100r 8W resistor is there to absorb the transitory overvoltage.

Can someone use a modern type of PNP low voltage transistor and replicate this PSU for a tube amp easily?

Certainly, but rearranging the circuit for a NPN transistor woud be preferrable. Actually a N MOSFET is a much better option.

Does this type of transistor in general eliminate the need for a high voltage bipolar transistor in tube amp PSU? It would have been a clever idea.

Again I can only speculate. It seems the designer has taken advantage, knowingly or serendipitiously, of a particular characteristic of the period transistor, but this can't be extended to modern transistors.
Capacitance multipliers are well documented; using low volt transistors is a receipe for failure.

 

[JohnRoberts]

In some ways good leadership. I hope he improved later. Otherwise, in the field he would have been a liability.

I met several who were liabilities. I remember one army cook who couldn't spell his own name, but it was a difficult name.

Better for him to wash out early than to be killed because in the field you could not sent two others along with him to take care of his targets.

He wouldn't have washed out, just repeated the training course until he passed. FWIW I never had to use my training in anger.

War sux. I wish they would stop this stupid war business. But until then defense is sadly neccessary.

Thor

Thor

Business is right, its all about the Benjamins, don't look now but China is on the move (and India has expanded their navy).

JR

 

[metalockpick]

No measurement gives an indication how to fix an issue, it merely shows that there is an issue.



YET the equipment being engineered will ultimately be judged subjectively.


I am not sure what "transparent" means in your use. Does it mean "low THD&N" or "audibly transparent". As Earl Geddes (among others) showed, relatively low measured distortion (0.01% THD with a full scale signal) does not guarantee audible transparency (in fact the distortion was highly audible and objectionable) while relatively high measured distortion (nearly 10% THD with a full scale signal) does not reliable cause a lack of audible transparency.

http://www.gedlee.com/Papers/The Perception of Distortion.pdf

Personally, for example, I found that a system using non-feedback single ended tube circuitry with ~ 0.3% THD @ 1W/8R and 3% THD @ 10W/8R driving a 97dB/2.83V sensitive 16 Ohm speaker appears subjectively transparent with a huge range of music, more-so than many highly regarded solid state amplifiers with very low measured distortion.

Of course, if we listen to music with decent dynamic range and to a stereo pair of speakers in a "normal" setup with ~105dB Peak SPL (THX playback level setting) most of the music will be happening 18dB below 10 Watt with 3% THD at around 87dB average SPL (which is quite loud really) at ~ 0.16 Watt or lower, where the THD of the Amplifier will be ~ .1% or lower and thus pretty much reliably inaudible, because of auditory masking, as HD of this amplifier is pretty much only H2 & H3.

So in this system context, a horribly distorted and broken by design Amplifier (objectivist view) nevertheless passes the psychoacoustic requirements for audible transparency (truly objective view accounting for context and human hearing) and "sounds realistic, dynamic and engaging, more-so than many solid state amplifiers" (subjectivist view).

Surely it would seem that to allow such a dichotomy to exist and persist is highly undesirable and that it should be resolved?

Thor

One problem is that measurement doesn't always translate to good sound, or even accurate measurements.
For years, "distortion analyzers" were misused to read "Distortion" in audio amplifiers by means of inputting a sine wave into an amplifier, and reading the distortion (aberration in the wave shape, compared to true sine) at the output. High feedback amplifiers would yield lower distortion readings. What was actually happening is that the feedback would help "learn" the sine wave and correct for frequency or amplitude deviations over a few cycles. This nonsense started around the introduction of the "Williamson" circuit and continued until the advent of personal computers and plug in cards to enable FFT measurement (late 1980s), which showed that while a steady state sine wave could be smoothed out with huge amounts of feedback, the resultant garbled sound and smeared transients from an amplifier with global feedback after a transformer (Big time delay), or even several series capacitors (Still a delay) was pure trash. Ya can't turn back time. If you have 20 dB of feedback with one of these and you go one dB into clipping, congratulations! you've gained 21 dB of distortion. If you can't hear that, you may live a very blissful and happy life.
If you don't properly test what happens when you overdrive the circuit, you are a useless fool as an engineer of audio products, or your customers don't care about high quality sound reproduction
I find that many engineers who worked in audio prior to the 80s and were taught "feedback fixes everything" still don't get it.
Having sensitive hearing isn't always a gift, it's often a curse, as you hear awful sound and deeply suspect the engineer who either can't hear or doesn't care.
I've recently changed my longstanding belief about the HP 330 series of distortion analyzer. It's a good tool for checking the quality of sine waves produced by HP analog oscillators. Just garbage for testing amplifiers.
High quality sound doesn't necessarily translate into sales. The McIntosh products sold very well, until the test equipment proved they were good looking rubbish. Same goes for Japanese hi fi of the 70s...".0001% distortion"...HA!