Carlos,
This was your amplifier.
There was a subconcious urge gnawing away in the back of your mind to take this path, and you worked at the design until it became what you wanted.
Besides, you probably don't have any cartridges left for your shotgun now. LOL.
I cannot fault you for wanting to leave 'well' alone, for indeed the protection circuit might change reproduction. However there is also the chance that the little bit of local negative feedback introduced by say 22 to 47 ohms in the VAS circuit could further improve reproduction.
Though as you say there are more important things to sort and spaces to organise at the moment.
Guess the amplifier development will be a little quieter now, but a thread full of happy constructors will be nice reward.
Cheers ............ Graham.
This was your amplifier.
There was a subconcious urge gnawing away in the back of your mind to take this path, and you worked at the design until it became what you wanted.
Besides, you probably don't have any cartridges left for your shotgun now. LOL.
I cannot fault you for wanting to leave 'well' alone, for indeed the protection circuit might change reproduction. However there is also the chance that the little bit of local negative feedback introduced by say 22 to 47 ohms in the VAS circuit could further improve reproduction.
Though as you say there are more important things to sort and spaces to organise at the moment.
Guess the amplifier development will be a little quieter now, but a thread full of happy constructors will be nice reward.
Cheers ............ Graham.
I don't think sonics require any more adjustment in this amp... sure I went with a hybrid of Graham and Carlos's suggestions.. Like the use of the VBE multiplier and huge capacitors on board, but I can't think mine sounds all that diffrent from Carlos', i.e. astonishingly good.
If you can draw a picture of what you mean, I might try it out after getting more familiar with the new DX's sound...
If you can draw a picture of what you mean, I might try it out after getting more familiar with the new DX's sound...
Is the sensitivity lower than the vanilla?
DVD player ias fine.... but it puts out a fat signal... probably about 2V at peak... sounds nice and comfy with the buffer pot at about 12 o' clock.
But my other sources sounds alot softer than with the vanilla...
maybe it is just because it is only 1 channel playing now......with the vanilla the panels in my frontdoor starts vibrateing at 12 o' clock.
My word Carlos I was so caught up in the near perfect trebles, I didn't even notice the bass, absolutely gobsmacking. Among the best of the best.... you can hear the tone of the drums perfectly... man!, I wish my dad was still around to hear this...
DVD player ias fine.... but it puts out a fat signal... probably about 2V at peak... sounds nice and comfy with the buffer pot at about 12 o' clock.
But my other sources sounds alot softer than with the vanilla...
maybe it is just because it is only 1 channel playing now......with the vanilla the panels in my frontdoor starts vibrateing at 12 o' clock.
My word Carlos I was so caught up in the near perfect trebles, I didn't even notice the bass, absolutely gobsmacking. Among the best of the best.... you can hear the tone of the drums perfectly... man!, I wish my dad was still around to hear this...
Yes, sensitivity is different, and you know where to tweak to adjust to your audio
source output level.... those resistances were you have the treble boost....increase them and the sensitivity will reduce...decrease them and you will have bigger sensitivity..
Are you really sure daddy is not listening.... you are constantly remembering him...do you think this is your memory?
Maybe not my dear...maybe not.... there are other things to learn in this world my dear nephew.
regards
Carlos
.......................................................................................................
Graham
Yes, dear Graham, i will be back...needing some time only...i will test those things...i promisse.
regards,
Carlos
source output level.... those resistances were you have the treble boost....increase them and the sensitivity will reduce...decrease them and you will have bigger sensitivity..
Are you really sure daddy is not listening.... you are constantly remembering him...do you think this is your memory?
Maybe not my dear...maybe not.... there are other things to learn in this world my dear nephew.
regards
Carlos
.......................................................................................................
Graham
Yes, dear Graham, i will be back...needing some time only...i will test those things...i promisse.
regards,
Carlos
Carlos,
No credit for your amp is due to me, it is yours, and yours alone. Graham it seems agrees; his contribution was considerable, and his advice about the VAS protection is something I should carefully listen to as well!! Using a single VAS in my AKSA and Lifeforce amps, I think I've had about three failures in many hundreds being sold and I suspect that brutal abuse might have a hand in this, though I can't be sure of course.
I would like to contribute more than I do, but prefer to work behind the scenes with individuals. This is for a good reason.
Patents cost tens of thousands of dollars, and are unviable and ineffective for the little guy. The only way to protect ones intellectual property is to remain silent about it. Integrated circuits were a godsend forty years ago because they enabled companies to hide away their clever tricks. But today there are companies around the world, and particularly the Far East, who specialise in reverse engineering large chips for a fee!
I find that revealing circuit details to individuals is normally OK, particularly with hobbyists of integrity, but a forum like this one is carefully watched by research teams from the large manufacturers who note down anything of significance, and I can assure anyone here that clever circuits frequently appear. The trick is to recognise them!! If you believe that advances in audio come only from the research departments of large corporations and universities, you are naive, probably more than half come from guys like us whose work gets out, is refined, and soon appears in contemporary products. Big companies are little companies that got it right, and determined, systematic paranoia leads to success in many fields. I have no doubt that Carlos' amp will now appear somewhere in a mass market product, but none of us here will ever know.........
The contemptuous exchanges between the objectivists and subjectivists are still raging decades on, and if anything worsening. At the engineering level, measurement and strong credentials are proof, but at the consumer level, only marketing and its alter ego of 'perceived quality' closes sales. This will always be so for most technical products; a product is usually NOT sold on engineering quality, only on X factors such as looks, appeal, 'sexiness', etc. Price has an impact, certainly, but in any market there will be a spectrum of price points, lots of people buy simply for image, so a higher price product can still survive if it's talked up, and made to appeal specifically to that market. For example, the snob/class appeal of the Rolls Royce, where fuel consumption and cost of ownership is dismissed as unimportant in such moneyed company.
So, Carlos, congratulations, you have reached a watershed with your design, and now you can move on to the next project. How many new amps will you finish this week?
Cheers,
Hugh
No credit for your amp is due to me, it is yours, and yours alone. Graham it seems agrees; his contribution was considerable, and his advice about the VAS protection is something I should carefully listen to as well!! Using a single VAS in my AKSA and Lifeforce amps, I think I've had about three failures in many hundreds being sold and I suspect that brutal abuse might have a hand in this, though I can't be sure of course.
I would like to contribute more than I do, but prefer to work behind the scenes with individuals. This is for a good reason.
Patents cost tens of thousands of dollars, and are unviable and ineffective for the little guy. The only way to protect ones intellectual property is to remain silent about it. Integrated circuits were a godsend forty years ago because they enabled companies to hide away their clever tricks. But today there are companies around the world, and particularly the Far East, who specialise in reverse engineering large chips for a fee!
I find that revealing circuit details to individuals is normally OK, particularly with hobbyists of integrity, but a forum like this one is carefully watched by research teams from the large manufacturers who note down anything of significance, and I can assure anyone here that clever circuits frequently appear. The trick is to recognise them!! If you believe that advances in audio come only from the research departments of large corporations and universities, you are naive, probably more than half come from guys like us whose work gets out, is refined, and soon appears in contemporary products. Big companies are little companies that got it right, and determined, systematic paranoia leads to success in many fields. I have no doubt that Carlos' amp will now appear somewhere in a mass market product, but none of us here will ever know.........
The contemptuous exchanges between the objectivists and subjectivists are still raging decades on, and if anything worsening. At the engineering level, measurement and strong credentials are proof, but at the consumer level, only marketing and its alter ego of 'perceived quality' closes sales. This will always be so for most technical products; a product is usually NOT sold on engineering quality, only on X factors such as looks, appeal, 'sexiness', etc. Price has an impact, certainly, but in any market there will be a spectrum of price points, lots of people buy simply for image, so a higher price product can still survive if it's talked up, and made to appeal specifically to that market. For example, the snob/class appeal of the Rolls Royce, where fuel consumption and cost of ownership is dismissed as unimportant in such moneyed company.
So, Carlos, congratulations, you have reached a watershed with your design, and now you can move on to the next project. How many new amps will you finish this week?
Cheers,
Hugh
I am finishing appartment organization...i have moved
Constructing nothing...but i will be back soon...with double power.
Thank you by the Market analisis and all informs...a nice text, very well written..something only you can do.
thank you to visit us.
You are humble...you have influenced me a lot...thanks by that.
regards,
Carlos
Constructing nothing...but i will be back soon...with double power.
Thank you by the Market analisis and all informs...a nice text, very well written..something only you can do.
thank you to visit us.
You are humble...you have influenced me a lot...thanks by that.
regards,
Carlos
Hugh, Carlos,
In theory I think VAS protection makes of course alot of sense, now if someone wishes to dare to do so they should design protection that doesn't adversely affect the sonics. This was an issue for me when I tried Grahams suggestion for protection on the Blameless VAS, it sounded compressed, edgy and overall quite bad by comparison to an unprotected VAS without bjt cotraception.. Theoretically though a marvellous idea but has an unfortunate downside in the most important area, sonics, I feel. But I only tried one configuration and there could be others that work better with different topologies, after all anything is possible in this strange world of Audio. Now if anyone can offer an insight, some explanation into this as to why it is what it is its more than welcome and very appreciated.
Best Wishes
Colin
In theory I think VAS protection makes of course alot of sense, now if someone wishes to dare to do so they should design protection that doesn't adversely affect the sonics. This was an issue for me when I tried Grahams suggestion for protection on the Blameless VAS, it sounded compressed, edgy and overall quite bad by comparison to an unprotected VAS without bjt cotraception.. Theoretically though a marvellous idea but has an unfortunate downside in the most important area, sonics, I feel. But I only tried one configuration and there could be others that work better with different topologies, after all anything is possible in this strange world of Audio. Now if anyone can offer an insight, some explanation into this as to why it is what it is its more than welcome and very appreciated.
Best Wishes
Colin
I think there are a few issues that could make the VAS protection audible.vynuhl.addict said:
1.) the added capacitance of the CE across the VAS. This may require a slight reduction in the Cdom value but more importantly a low capacitance transistor must be used. What are typical CE capacitances for To92 small signal transistors?
2.) the transistor curves show that the transistor starts to conduct when Vbe is around 400mV. This voltage must not be exceeded during normal audio signal handling. For the 22r value shown earlier the protection transistor is starting to have an effect at 400/22=18mA. It would be unwise to adopt the more usual Vbe= 600 to 650mV as the trigger point if one desires inaudibility.
3.) the VAS quiescent current can be any where in the range 3mA to 30mA. Let's assume 10mA for this example.
The drivers require current to operate. (I lost someone with this discussion previously, I'm trying again). The drivers draw and inject a quiescent current that nearly cancel when no signal is present. Therefore the VAS current is almost identical to the CCS or load resistor current.
As signal is passed the VAS modulates the current passing through it. Theoretically none of this variation passes through the CCS or the load resistor.
The variation passes to the drivers.
Firstly to the upper driver as it increases it's collector current to feed the outputs and as the VAS current reduces towards quiescent. Secondly the lower driver injects current into the CCS/load resistor. The VAS MUST pass less current to allow the lower driver to inject that extra current.
Let's assume that a reasonable range for the VAS modulation is 100% of the VAS Iq, i.e. 10mA in this example.
The VAS passes a range of current from 0mA to 20mA while the CCS/load resistor passes a steady 10mA. All the variation goes into or out of the drivers.
Notice how close the maximum VAS current is to the protection transistor turn on current. What if the protection transistor starts to conduct at a lower Vbe than 400mV? maybe 350mV? This could be the trigger point for the protection transistor.
My contention is that all protection systems should be inaudible. They should be designed to NOT limit a valid audio signal.
For the example above with a VAS Iq=10mA I would use a sensing resistor of 20r. I arrive at this by taking the conventional Vbe=600mV and applying 3times the VAS Iq. i.e. 600/(3*10)=20r.
4.) what about asymmetric audio signals? What if the positive going (with respect to the PNP VAS) current is bigger than the negative going current? Could the protection transistor trigger on the positive going current but apparently never drop to the near zero current required for the negative current output?
Any other views on possible audibility senarios?
Vynuhl,
do you have details of your audible protection?
A good way to avoid sonic intrusion might be the Baker clamp.
It relies on the voltage output from the VAS. As this voltage approaches the rail, a diode chimes in and prevents further excursion. It sounds terrible I'm reliably informed when this happens, but it occurs just shy of clip and has no audible effect at lower voltage.
I don't have a circuit handy but there was one in this forum kicking around a couple months back.
Cheers,
Hugh
It relies on the voltage output from the VAS. As this voltage approaches the rail, a diode chimes in and prevents further excursion. It sounds terrible I'm reliably informed when this happens, but it occurs just shy of clip and has no audible effect at lower voltage.
I don't have a circuit handy but there was one in this forum kicking around a couple months back.
Cheers,
Hugh
Hi Andrew,
Well discussed. The BC547, or BC549 has low capacitance, and I've not 'heard' them in this position. I've also not heard the higher capacitance BC546 in this position either, though the Vbe is a little higher.
The value of the VAS emitter resistor does of course need to match 2x VAS collector current before developing clipping potential, so 22 ohm should be a reasonable match for Carlos' HR, and if audible try the next E12 value of 18 ohm.
Hi Hugh,
The voltage amplitude limit won't help for output stage overloading where the amplifier cannot achieve max output swing because the load prevents voltage development for output current available. The VAS will still attempt negative overdrive and a smelly silence will be the outcome.
Cheers ........... Graham.
Well discussed. The BC547, or BC549 has low capacitance, and I've not 'heard' them in this position. I've also not heard the higher capacitance BC546 in this position either, though the Vbe is a little higher.
The value of the VAS emitter resistor does of course need to match 2x VAS collector current before developing clipping potential, so 22 ohm should be a reasonable match for Carlos' HR, and if audible try the next E12 value of 18 ohm.
Hi Hugh,
The voltage amplitude limit won't help for output stage overloading where the amplifier cannot achieve max output swing because the load prevents voltage development for output current available. The VAS will still attempt negative overdrive and a smelly silence will be the outcome.
Cheers ........... Graham.
To our friends that feel interest to enter the group buy
Do not be afraid.... modifications suggested will be tested in advance, and if aproved will be included into the next model.
I think will sound compressive, because the way this over current works..of course, limiting...sound will be limited too...but this will be tested..... for the next model.... the board made will be good till december.
This will happens, in December.
So.... if you want to listen that nice sonics...go ahead into the group buy Nordic is organizing.
It is a non profit movement.
Guaranteed your satisfaction with the sonics.
regards,
Carlos
Do not be afraid.... modifications suggested will be tested in advance, and if aproved will be included into the next model.
I think will sound compressive, because the way this over current works..of course, limiting...sound will be limited too...but this will be tested..... for the next model.... the board made will be good till december.
This will happens, in December.
So.... if you want to listen that nice sonics...go ahead into the group buy Nordic is organizing.
It is a non profit movement.
Guaranteed your satisfaction with the sonics.
regards,
Carlos
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