Swinik VS Quad -- where is your Bridge, gentlemen?

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Here is the Quad 405-2 schematics (thanks for the link!),

http://www.dc-daylight.ltd.uk/Valve-Audio-Interest/Schematics/QUAD-405-Evolution.pdf

here is the Swinik:

swinik.gif


Main difference: they used 4 transistors in a voltage amplifier, I used only 2 as fastest as was possible that time. And mine worked with more current than their. Also, mine had 2 times less of a voltage amplification. The result is, I could use a global feedback on the whole frequency band, they could not, they had to fight against parasitics EVEN WITHOUT a global feedback, while I used only one RC network (not shown on the schematics). Also, I limited gain of the OpAmp by a third feedback on the whole band except lower end (and DC, corresspondently, for less DC offset on output), for better control of transcient processes. Also, I used better impedance match for less POWER amplification of the whole amplifier taking more CURRENT from the OpAmp. As the result, Swinik was faster and had LESS distortions in the hearable frequency band, despite I used Soviet transistors and OpAmp that only were available for me that time. Their quazi - complementary output with additional phase asymmetry on high end of spectrum when complementary pairs were already available...

And I did not discover famous "Bridge" that gentlemen criticizing Swinik mentioned... Just the same resistor (R1 in Swinik, R38 in Quad) for transfer function approximation that was obvious long before 1975... However, I don't know if they could patent an approximation instead of "Current Dumping", I believe... ;)
 
The swink is a very basic idea that has been preceeded to an even better level by such amplifiers as the crown dc 300/phase linear 400/700b as well as many other high power pa amplifiers
the clasiffication would be for the swink A/C where the crown would be AB/C
As for the quad if you visit quad world you will find the (bridge)
it may not be obvious but carefull study will reveal it !
I have tested the Quad and under steady state sine waves the distortion was so low as not to be measurable with my equipment "Radford/sugden" this not the same for the others i have mentioned I wish it was so easy we would all be making Swinks
regards Trev
 
With respect
The quad bridge has been very well documented over the last 25 years
this is a Gm correcting device! I suggest that you look it up I am reluctant to do so for you if you dont study you wont learn. I have here amongst my papers the origional treatise on the 405 and the current dumping concept but it will take me to long to sort it out for you
If you look on the forum you will find even more comments re the amp
I am not a fan of the 405 myself I prefer more conventional amplifiers
I will if I can find the time send you a copy of the origional article
Regards Trev
 
Wavebourn said:


I also choosed R1 resistor and all feedbacks according to load impedance and don't see something extraordinary that may be patented. Just an understanding what and why do you do something...

The bridge components are not selected for load impedance. There is a long thread called 'Death of Gainclone' here, IIRC there is a lonk to the original documents and a longer treatise called 'error feedforward' in it. Use the Search function...
 
ilimzn said:


The bridge components are not selected for load impedance. There is a long thread called 'Death of Gainclone' here, IIRC there is a lonk to the original documents and a longer treatise called 'error feedforward' in it. Use the Search function...

Thank you ilimzn. I understand what do you mean; transfer function of the C - class stage as if don't depend on a load impedance. Unfortunately it is not true.
If to use imagination it is possible to find a Gainclone jumping from the London bridge, as well as Anna Karenina jumping under the train of dumped current. But if to look from another side, approximation means several functions that continue each other as smoothly as possible. For example, A class amplifier with gain G1 and output resistance R1, C class symmetrical emitter follower with gain G2 and output impedance R2, and symmetrical source followers with output impedance R3. Despite of such smoothness additional global feedback helps to reduce nonlineariries, as well as faster amplifiers help to minimize their impact on audible frequencies.

--Anatoliy
 
edl said:
Dear Wavebourn,

This design looks me so exciting.
Have you got full schema? I would look into that in my simulator.

Regards,


What do you see on the picture, IS the "full schema" of the amplifier as it was built back in 1977. However, there was also a RC-network to stop parasitics and power regulators for OpAmp.
In the original design A - class stage was loaded by couple of 390 Ohm/20W resistors in series, it's own gain was 5. Today I would use a CCS on a fast PNP transistor instead of resistors with a positive feedback through a capacitor that increases distortions. Input resistor was 10K, global feedback resistor was 300K, I don't remember values of resistors across OpAmp and OpAmp+Class A amp, I played with them using pots to obtain results I liked the best. I remember I used 1 MOhm pots with 0.1 MF caps in series. But I do not remember final values of resistors.
You are free to play with details to obtain your optimal results, they will be yours. ;)

Or wait untill I decide to disclose the current 3-step approximation version that uses vacuum tubes instead of OpAmp and additional FETs on output.
 
Hi,

Thanks for the replies!

I really appreciate creative, innovative circuts. I think yours is that! Uses a brainy idea.
I studied Quad-405 a lot (many hundreds - oh not, thousands (!) of clone were bulit, that's the most popular diy project here since 1980...) so I interested to any error-correction - or similar, not conventional - design.
Thanks for sharing the values you remembered.
I starting to look into your circut deeper.

About the hybrid amp:
Hey, that firm wasn't soviet, but hungarian - as me! :) Unfortanetly after the change of regime, in the early 90's BEAG closed down.
I have some BEAG gear at home: a 100W all-tube monoblock (PP PL509), a 100W/100V solid state industrial amp, and many parts... PCB's, shassis, ...
The Beag goods are seeing my life through.
So thanks for link, I saved the schematic!

Best regards,
 
I would like to see if you have any distortion figures for your amp
I myself produced 30 or so amplifiers using a class A/AB/C scheme in the 70s ,These were used at a local disco for about 10 years and though they sounded ok. You could see on a scope the change of tranfer function as the boosters switched on/off!
They sounded ok but I am sure that the distortion figures would not have been that good .
I am not being negative but I know that if it was so simple we would have a world full of skwings!
regards Trevor
 
latala said:
I would like to see if you have any distortion figures for your amp
I myself produced 30 or so amplifiers using a class A/AB/C scheme in the 70s ,These were used at a local disco for about 10 years and though they sounded ok. You could see on a scope the change of tranfer function as the boosters switched on/off!
They sounded ok but I am sure that the distortion figures would not have been that good .
I am not being negative but I know that if it was so simple we would have a world full of skwings!
regards Trevor


Trevor;

unfortunately beliefs and fashions rule the world that's why you may see some not very best topologies repeated, and may disregard yours, despite people say they sound brilliant. Also, don't forget of patents that sometimes work like a dog on a hay: don't eat, but don't permit.

To tune up Swinik I used a triangle from a functional generator on 20 KHz. Unfortunately, THD measurement appliances were not common in design of military analog control systems, so I could not measure percentage of distortions. Also, as I told before, I myself did not believe that I build something extraordinary, I just "cheated to get satisfactory results using cheap methods", as we did in our laboratory works with control systems. However, I was intended to build such an amp in a hybrid IC, but I did not, because refused the work offer for Hybrid IC Laboratory of Tomsk Institute of Semiconducter Devices, because was young and too hot.
 
I seem to remember application notes from National for the LM380 series of amplifiers that used the same scheme as the Swinik where output ransistors were connected in the same way
as in your swinik across a resistor as per R1
I do agee with your basic philosopy re distortion measurements after all we listen to amplifiers with music for 99.9999% of the time
My amplifier that I use at the moment on my personal system is a Crown Dc300a But if you study there distortion figures they are very cunning They quote low leveles up to 50 mW and then low levels at 160 watts and as I have said this is an AB/C design
I wonder what the distortion is at 0.5 watt?
If you like your amp then build it it certainly is simple and potentialy stable
I would always rather pay the penalty in slightly higher distortion figures if it is more reliable
During the early 70 I could not afford good test equipment but by using what was then the latest in op amps built my own distortion analyser using the then latest hi performance op amp TL071
this was a simple arrangement where the out put from the amp was attenuated and then fed into the inverting input to the opamp
the input signal to the pwer amp was also connected to the non inverting input
with carefull adjustment i coulsd resolve to better than 0.1% distortion
the outut of the op amp was measured on a voltmeter /scope
Try something like that on your amp and I feel sure you will see a slow Xover disparity all though I am sure you will not generally hear it
Regards Trev
 
edl;

of course BEAG was Hungarian!
Also, I saw a professional audio studio gear EAG, is it the same?

What do you think of my line arrays, do they look familiar? ;)

http://wavebourn.com/images/pyramid/concert_speaker_4.jpg

They are full - range and handle 10 times more power than BEAG vocal line arrays, but smaller in size.

Also, I have a new crazy idea, to combine 2 of my projects, Swinik and Nuclon, in the single amp. Most probably, I'll have to fight against parasitics since 2 high gain stages with 100% NFB differs from the single emitter follower...
 
Trev, I actually did not need a distortion measuring equipment for Swinik because it was the inverting amp by nature, but I never had an idea to measure percentage of distortions then, I used it for a bass guitar, so visual strightening of a triangle on a screen of oscilloscope corellated well with what I heard from speakers.

Also, I especially used such tricks so a speaker box and a crossover were designed such a way they had peaks around 500 and 2800 Hz, for the best musicality. No need to fight against resonances if you understand how to use them for good. ;)

Also, I used to generate distortions trying to satisfy my friend, a guitarist of our university band, but never satisfied him completely, he knew what he wanted, but could not explain (I played then bass guitar), also an analog synthesizer was built in a leasure time by my friend, an engineer, who worked on Technology cathedra, using lots of my ideas of what distortions are needed for what sound, and how to get them. ;)

Distortions are my friends. We understand well each other. :D
 
Well I have to agree re guitar amplification that is an entirely differant matter!I play a little myself and have a few friends that play in bands as such I am always pleased to help with amp repairs etc .
In this case we are making the sound not reproducing these are indeed a very differant animal any - thing goes
Regards Trev
 
latala said:
Well I have to agree re guitar amplification that is an entirely differant matter!I play a little myself and have a few friends that play in bands as such I am always pleased to help with amp repairs etc .
In this case we are making the sound not reproducing these are indeed a very differant animal any - thing goes
Regards Trev

Currently I listen at home through the system I use for sound reinforcement on performances for singers with acoustic guitars, however except microphones and Yamaha MX400-24 mixer. :)

Here is the subwoofer (isobaric double-speaker loaded by a Low-Q horn):

http://wavebourn.com/images/pyramid/sw_5.jpg

Small speakers on top of it represent improvised "central speaker" for a cinema theater (Sony VPL-PX30 projector)
 
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