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TGM5 has only a single output pair, no parallel outputs. It does have an extra pair of driver transistors making the output a Triple. I guess this is more complex, but I feel it's worth the effort because this output stage does not load the VAS like a 'regular' Double output. You could leave that out and go with the Double. You can also chop out the input cascode devices. Athough this would no longer be the LazyCat front end, it would behave the same and be the simplest possible arrangement. Simpler even than the original SSA. It might be interesting to give this a try.
TGM = 'The Great Machine', a reference to the Krell.
TGM = 'The Great Machine', a reference to the Krell.
dah..... maybe i really have no idea how to breakdown a circuit operations....
what will cascode input does, compare to normal pairs ? The double/triple VAS, what will help ? saw a Q7 in the middle , is it the Vbe Multiplier ?
Well.... maybe its more simpler, but the sound quality is not worth of doing that ? but i agree that it is interesting...... anyone can do the simulation, or teach me how to use simulator (by using which ? previously used simulation software are complicated.....)
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I think you have a pretty good idea about circuits, but sometimes the way they are drawn makes them look complex.
I've never used Cascode before so I don't know much about it - it came with the Lazy Cat design so I've decided to use them. As far as I know, they are simply another stage of amplification after the input devices, only they are in 'common base' configuration. When used like this these cascode devices lower the voltage and reduce fluctuations in the voltage at the collector of the input devices, allowing them to operate at higher current without overheating (good for increasing transconductance and linearity) and they reduce the affect of parasitic capacitance (good for lower phase shift and h.f. roll off). You kind of get them for 'free' in this design because the bias circuit for them is used to bias the emitters of the input devices so deleting them only saves you two transistors - which is less than $2 where I live.
The Triple helps in several ways. The TGM5 is all-BJT whereas the original SSA in this thread has a FET output. FETs isolate the amplifier from the load impedance, they have a high input impedance. The VAS has to drive the output stage, so an output stage with high input impedance like a FET is good. The disadvantage of FETs is that their inputs are essentially a capacitor, which has to be charged and discharged so at high frequencies they need current. Anyhow with TGM5 the output is a BJT and it has a relatively low input impedance compared with a FET. By having a Triple with 3 stages there are more devices to buffer this impedance. The VAS now has an easier job and distortion will be lower. In a Class AB amplifier the output devices are rarely both active at the same time, but alternatively switching from one output device to the other, they present a non-linear load to the VAS so it helps a lot to isolate it with a Triple. I've used a particular kind, I've used a Sziklai pair/CFP for the drivers. Compared with two emitter follower stages this offers less voltage drop (so you can swing closer to the supply rails), is vastly more linear at high signals. Triples aren't all plain sailing, they can be susceptible to local oscillations which is why I have a pair of capacitors in there.
Is the sound quality better ? - I've no idea ! - haven't built it yet and I don't have a lazy cat version to compare with. The Roender amplifier uses the same output stage I am using and those that have heard it say it sounds superb - I regard it as one of the benchmark designs on this Forum. I've used this output stage before, on my TGM3 amplifier, the best sounding solid state amplifier I've made so far, it also has current feedback so TGM5 is more a less an extension of TGM3 to a symmetric input - I think it's going to sound just fine
I've never used Cascode before so I don't know much about it - it came with the Lazy Cat design so I've decided to use them. As far as I know, they are simply another stage of amplification after the input devices, only they are in 'common base' configuration. When used like this these cascode devices lower the voltage and reduce fluctuations in the voltage at the collector of the input devices, allowing them to operate at higher current without overheating (good for increasing transconductance and linearity) and they reduce the affect of parasitic capacitance (good for lower phase shift and h.f. roll off). You kind of get them for 'free' in this design because the bias circuit for them is used to bias the emitters of the input devices so deleting them only saves you two transistors - which is less than $2 where I live.
The Triple helps in several ways. The TGM5 is all-BJT whereas the original SSA in this thread has a FET output. FETs isolate the amplifier from the load impedance, they have a high input impedance. The VAS has to drive the output stage, so an output stage with high input impedance like a FET is good. The disadvantage of FETs is that their inputs are essentially a capacitor, which has to be charged and discharged so at high frequencies they need current. Anyhow with TGM5 the output is a BJT and it has a relatively low input impedance compared with a FET. By having a Triple with 3 stages there are more devices to buffer this impedance. The VAS now has an easier job and distortion will be lower. In a Class AB amplifier the output devices are rarely both active at the same time, but alternatively switching from one output device to the other, they present a non-linear load to the VAS so it helps a lot to isolate it with a Triple. I've used a particular kind, I've used a Sziklai pair/CFP for the drivers. Compared with two emitter follower stages this offers less voltage drop (so you can swing closer to the supply rails), is vastly more linear at high signals. Triples aren't all plain sailing, they can be susceptible to local oscillations which is why I have a pair of capacitors in there.
Is the sound quality better ? - I've no idea ! - haven't built it yet and I don't have a lazy cat version to compare with. The Roender amplifier uses the same output stage I am using and those that have heard it say it sounds superb - I regard it as one of the benchmark designs on this Forum. I've used this output stage before, on my TGM3 amplifier, the best sounding solid state amplifier I've made so far, it also has current feedback so TGM5 is more a less an extension of TGM3 to a symmetric input - I think it's going to sound just fine
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Yes, they isolate the parasitic caps like would do a ground between two wires. About removing them, i think it would be a bad idea, as bandwidth is an issue, and parasitic caps is an open door for instability, and less bandwidth induces IM distortion. I know no other way to design a good fast Amp driving power Fets without cascodes. And they sound transparent. That i love with "Crazy Cat" ;-) is his choices respect all i've experienced on my side in matter of good sound and good design practices: Cascodes, Current feedback, over sized currents sources, symmetrical design, power FETs and keeping-it simple with good parts.
SSA !
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Hi Nico, Can i use irfp240/9240 output in your mosfet design? (LazyCat/Nico Ras) I have a pair of irfp240/9240. What modification should be made? Thanks in advance.
Note: I have a pcb design by alex mm with your mosfet schematic (LAZY CAT-NICO RAS AMPL/Lazy Cat Refined R01)
Regards,
Boyet
Less bandwith does not induce IM distortion, where did you get this belief that it does or maybe you´d care to prove this ???
Read up on the subject by well known professionals youll find on this forum, Bob Cordell, D Self, Scott Wurcer and many others.
Sorry, but i do not want to argue about such an evidence, known by every knowledgeable people in audio, and, for sure, by those people you are referring to like god.
When your amp is unable to follow your signal transients, if it uses CR, that's what happens. So, you will have to reduce the bandwidth of the signal applied to it before it enters in active devices if you want to get rid of IM. And that is all the purpose of Current feedback (or error correction) designs: higher slew rates.
I'm not well known by you, but, as a "professional" during 40 years, i don't care with "well known" or not, audio electronic is not a matter of fashion or VIPs. Unless you are a consumer of special sounding loudspeaker's cables ;-)
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You dont have to be a professional or well known, only versed in electronics,be it RF or audio, you wont find one single textbook written since the dawn of electronics which will substantiate your statement, you may find unsubstantiated staments like that from snake oil vendors. There is more to it than your statement.
I strongly recommend you follow Dadods suggestion and follow that up with some reading on Bob Cordells website.
I do not listen to vendors, they where listened to us, as in the research and department of the most important audio manufacturer of my country, i was yet working in as an engineer during the 70 th, we provided both the equipment they sold and the statement they should use to sell them.
This mister Cordells was not in my degrees program as an author, but Ohm's law and mathematics... and, why, if you refer to him not asking-him to explain my (obvious) statement to you ? If he state the contrary (i really doubt on that), i will make my opinion on his credibility, not change my mind that experience and studies had build.
Take a real amp change the amp stage for a slow part, and compare real measurements,as we done in my research and department laboratory for years ?
With the second frequency near the limit of the amp capability (1000 and 20 000 for an amp with a cut-over of 20 000 for an example). Or make a simple spice simulation ? And try to understand why ?
You will see that, adding those two waves, the upper one at the limit of the slew rate of the amp produce at a signal with faster slew rate than the amp will be able to follow. See ? So the amp will be unable to reach the top level of this sum when the mounting or descending edges are adding themselves, and that will happens in regular intervals. Agree ?
Now, if you filter the highest frequency away, you will discover that there is a modulation of the 1000 hz frequency at a lower frequency, what they called IM in my schools yet before 1970. (Sorry for my poor English, it is difficult for me to be brilliant in this language).
End about this subject, for me, now, people in real life have more respect than you about my knowledge in audio.
Try to learn at least the basis before to be injurious, please.
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This is funny, as my last play with the Crescendo, modifying-it to SSA design, demonstrate exactly what i pretend (and presumed).
Slew rate had gone from 200V/µs to 1500V/µs (yes sir ;-). There is no other place to understand the sonic amelioration that this mod had produced, on an existing amp, with exactly the same parts and global design: Improvement in slew rate of a yet performing amp (1Mhz bandwidth) had reduced the yet very low level of IM. And you can hear the slight difference in a more transparent and fluid sonic signature.
PS: i do not pretend this physical phenomena is the only source of IM, i hope nobody had understand my statement to said so ? There is several sources in non linearity, specially with thermal effect in semi-conductors.
This is too an explanation why so many people prefer the sound of tube amps: tubes have a high bandwidth.
Slew rate had gone from 200V/µs to 1500V/µs (yes sir ;-). There is no other place to understand the sonic amelioration that this mod had produced, on an existing amp, with exactly the same parts and global design: Improvement in slew rate of a yet performing amp (1Mhz bandwidth) had reduced the yet very low level of IM. And you can hear the slight difference in a more transparent and fluid sonic signature.
PS: i do not pretend this physical phenomena is the only source of IM, i hope nobody had understand my statement to said so ? There is several sources in non linearity, specially with thermal effect in semi-conductors.
This is too an explanation why so many people prefer the sound of tube amps: tubes have a high bandwidth.
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Great looking SSA amp module, congratulations Alex.
This is really unexpected gift to the DIY community and it will serve the job with all demanding speakers as intended. Please give me some time to check the layout & connections and then give the error list to you. I'll do it on Friday morning.
Hello LC,
Any headway on going over Alex's layout ,
Regards,
Just a quick look at the Bob Cordell's web site( i was curious) where i read:
Another View of TIM
Audio
February 1980
This article was published in Audio magazine in February, 1980 at the height of the controversy surrounding Transient Intermodulation Distortion and its relationship with negative feedback. The article discusses the origins of TIM and the transient nature of music that can bring it on. It points out that amplifiers with inadequate slew rate margin are the ones prone to TIM."February 1980
Who is ridiculous, now, the one witch had not read-it, but knows that since 1970, or the ones who cannot even understand what they read ?
It is EXACTLY what i said, and i had even noticed feedback to be a part of the problem in my first answer to your disrespectful ones.
Quoting myself about IM: "When your amp is unable to follow your signal transients, if it uses CR, that's what happens"
forums can be the best (with people like Lazy Cat) and the worse places (Guess who ?) in the same time..
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To music across horns, oh yes ! Definitively. May-be you would be surprised listening to them, so realistic, so natural, non aggressive and so dynamic ?ESP all that knowledge and you still listen to Horns .....
with class-D...
I had worked on a spherical waves exponential curves calculations, long years ago with a friend of mine, it is near what designed LeCleac'h some years later and look the same. Had-you even listened to some of them with a good driver in a well designed system ?
Or did you believe it sound as horrible as bad PA or studio horns ? Or that Mr Hiraga is crazy too ? Don't you believe that, as a sound engineer, i had listened to a lot of various equipments (quite everything witch exists) and, when i make a choice for myself, it is not without very good reasons and some knowledge of how sound real instruments i was paid to record?
For class D, not yet, my project is precisely to deeply explore this new domain (new for me) i want to discover by myself with my soldering iron. May-be i will find-it bad, may-be not.Their principle is just as accurate as your delta sigma digital recordings and lies on the same principles.
The only issue is filtering the clock, a little too close to the signal high frequencies for the moment (speed of available power Mosfets) to be rejected enough without phase problems. Reason why, in a first time, i will explore them in the low and low middle range where their high efficiency, high damping factor and minimal distortion is a must. Then, if i reach the sound quality i expect, i will try different solutions for filtering in the treble domain.(i have some ideas about what to experiment).
And, as i said, i have a perfect CFB 2X140W SSA as a spare part. and an other less powerful SSA in progress for treble. The D amp will have to sound better to be chosen.;-). I believe in what i hear and measure. Will stay-you informed.
But did i make a mistake, feeling some kind of irony in your question ?
Are-you this kind of audiophile thinking there is no salvation without vinyl records, Quad speakers, tube amps and silver plated wires Teflon isolated with cryogenic treatment?
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Real live music feel... gone ?
Esperado, You are maybe one of the last Mohican's who can easily hear in a second, feel, and know what the real life like sound is and how to perceive it easily with ears and also feel it with body without looking on the computer screen graphs and till after judge the sound. . . I understand what You mean.
Recently I visit locally HiEnd Audio show. What I was hear there is what I suppose is todays reality in home music-audio playback, it is a IPod, web or notebook streaming music fashion, mostly listening of a thin sound even with the very well known English manufacturers of audio equipment. I see and hear also the setup using sonically the very high quality audio equipments. I was shocked knowing the price for the best cables "on the planet" theirs Jewelled cost was some 120 000 EUR !! only for cables!!! Active electronics used was an additional cost. It was currently the best avail. Spectral setup - preamp and the latest monoblocks, speakers were from very high praised US manufacturer made of the best avio-grade aluminum, and an ultra-fi LP-playback source . . . After hearing this setup I was ask my self where is the real live music gone ??. . . .
To my experience with live music I was surprised that todays HiFi fashion is like listening music throe the hole of an old doors lock and looking throe it with one eye what's going on the other side. . . where the real orchestra is and theirs musicians are seating on the stage and playing real, live music. This throe hole listening music effect is so evident with quite a lot of exhibitors, no matter what kind technology they represent - Tubed or SS. I'm sure, all are manufactured under strictly followed the best possible rules of the EDA design phases. They really miss somewhere the connection and most of them don't know any more what the real power and feel of a live music is..
These are my personal feelings of what is perhaps todays reality in quite a lot home music playback systems..
You mention speed, this is the key to a real live music feelings and here the Lazy Cats SSA Amp design shines from the others.
We lose the precious audio informations all the time along the way to the speakers from the whatever music source and add some others not really related to orig. source.
What I really like is a simple, dead noise quiet, fastest, short and elegant analogue playback chain with shortest possible path to perceive as much informations possible with minimum changes from one state to another till the speakers end.
Esperado, You are maybe one of the last Mohican's who can easily hear in a second, feel, and know what the real life like sound is and how to perceive it easily with ears and also feel it with body without looking on the computer screen graphs and till after judge the sound. . . I understand what You mean.
Recently I visit locally HiEnd Audio show. What I was hear there is what I suppose is todays reality in home music-audio playback, it is a IPod, web or notebook streaming music fashion, mostly listening of a thin sound even with the very well known English manufacturers of audio equipment. I see and hear also the setup using sonically the very high quality audio equipments. I was shocked knowing the price for the best cables "on the planet" theirs Jewelled cost was some 120 000 EUR !! only for cables!!! Active electronics used was an additional cost. It was currently the best avail. Spectral setup - preamp and the latest monoblocks, speakers were from very high praised US manufacturer made of the best avio-grade aluminum, and an ultra-fi LP-playback source . . . After hearing this setup I was ask my self where is the real live music gone ??. . . .
To my experience with live music I was surprised that todays HiFi fashion is like listening music throe the hole of an old doors lock and looking throe it with one eye what's going on the other side. . . where the real orchestra is and theirs musicians are seating on the stage and playing real, live music. This throe hole listening music effect is so evident with quite a lot of exhibitors, no matter what kind technology they represent - Tubed or SS. I'm sure, all are manufactured under strictly followed the best possible rules of the EDA design phases. They really miss somewhere the connection and most of them don't know any more what the real power and feel of a live music is..
These are my personal feelings of what is perhaps todays reality in quite a lot home music playback systems..
You mention speed, this is the key to a real live music feelings and here the Lazy Cats SSA Amp design shines from the others.
We lose the precious audio informations all the time along the way to the speakers from the whatever music source and add some others not really related to orig. source.
What I really like is a simple, dead noise quiet, fastest, short and elegant analogue playback chain with shortest possible path to perceive as much informations possible with minimum changes from one state to another till the speakers end.
.....thanks ,I hope this time it's better layout
Alex.
Hi Alex,
Could you create a 4 power output transistor version PCB and also the Power supply if you get a chance? I think there will be more interest on this than the V12 version, which I think so expensive to build.
Thanks and appreciate for sharing your skill/talent on designing PCB in this forum.
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