Hey, quasi ..I meant for that to just state an absurd example
of the BS that I was responding to.
Your " brother of Quasi" is still shakin' the house as a sub amp
and your "power amp under development" brought me to
explore further (D. self ,leach) a sound topology.
I've recommended your amp to many newcomers...
Please forgive me
Just a subconscience reverberation of Wasim and our other
indian friends doing the "burning amp" thing.
OS
of the BS that I was responding to.
Your " brother of Quasi" is still shakin' the house as a sub amp
and your "power amp under development" brought me to
explore further (D. self ,leach) a sound topology.
I've recommended your amp to many newcomers...
Please forgive me
Just a subconscience reverberation of Wasim and our other
indian friends doing the "burning amp" thing.
OS
Quasi,
I think of your amp as turbocharged, driving a dyno in a fully protected, ventilated room with the exhaust manifold and turbo glowing cherry red and producing 1000 Kw!!
I think you've licked the cross-conduction problem completely!!
When are next in Melbourne? We need to pow wow.....
Hugh
I think of your amp as turbocharged, driving a dyno in a fully protected, ventilated room with the exhaust manifold and turbo glowing cherry red and producing 1000 Kw!!
I think you've licked the cross-conduction problem completely!!
When are next in Melbourne? We need to pow wow.....
Hugh
Hi folks.
Interesting and entertaining thread.
Ow. My brain now hurts from the sheer amount if info I've just digested.
And to think tracking down the problems in my commercial preamp were complex (And I have have help that I've enlisted from professional people for the stuff that's beyond my basic knowledge!) I think I'll cut my teeth on lesser projects before embarking on my own (passive) preamp design. I don't want to turn the poweramp into a smoking ruin.
I can fully agree on the free info line of thought though - some information on the most basic of schematics / layouts etc should be public domain imo - just the basics to stop people frying themselves - but once you start swapping out components / redesigning pcbs then sure you should protect that if it's a commercial venture. That simply makes good business sense.
Cheers.
Interesting and entertaining thread.
Ow. My brain now hurts from the sheer amount if info I've just digested.
And to think tracking down the problems in my commercial preamp were complex (And I have have help that I've enlisted from professional people for the stuff that's beyond my basic knowledge!) I think I'll cut my teeth on lesser projects before embarking on my own (passive) preamp design. I don't want to turn the poweramp into a smoking ruin.
I can fully agree on the free info line of thought though - some information on the most basic of schematics / layouts etc should be public domain imo - just the basics to stop people frying themselves - but once you start swapping out components / redesigning pcbs then sure you should protect that if it's a commercial venture. That simply makes good business sense.
Cheers.
It is very very strange that all three of you have 10 posts or less at diyAudio and have used the majority of your posts to complain about Hugh's thread, or in the case of 777 promote a company that rips off Nelson Pass's designs against his wishes.
You are very self-rightious about his thread yet I can't see any contributuions that any of you have made to help people.
We like people here who make stuff and help out in some way- even a small way. Generally people aren't allowed to demand that others do things. People that just post to complain aren't appreciated. Perhaps there are other DIY sites that you would like better? Audio Asylum maybe?
For aksa, an amplifier that aims to stay away from being complicated,
i would use a simple 'normal' current mirror = 2 transistors
but I would add two 100 Ohms emitter resistors for those mirror transistors.
This would only 'steal' like 0.5mA x 100 Ohm = 0.05 Volt from the 0.65 Volt
I would also use <=100 Ohm emitter resistors in the PNP LTP pair.
The use of mirror alters AKSA.
Input stage will have twice ( x2 ) gain.
And so the feedback factor will increase with a similar amount.
Using emitter resistors in the LTP pair will reduce gain a bit
while making it even easier to achieve close 50%-50% balance of the current in the differential pair.
While changing from only one resistor to VAS to use of a current mirror
may seem like a very small change,
it will have a considerable impact on the overall circuit.
But mainly this change will improve the electrical performance.
What it will do to perceived sound, I cant tell.
Hopefully will still give pleasure to listeners
i would use a simple 'normal' current mirror = 2 transistors
but I would add two 100 Ohms emitter resistors for those mirror transistors.
This would only 'steal' like 0.5mA x 100 Ohm = 0.05 Volt from the 0.65 Volt
I would also use <=100 Ohm emitter resistors in the PNP LTP pair.
The use of mirror alters AKSA.
Input stage will have twice ( x2 ) gain.
And so the feedback factor will increase with a similar amount.
Using emitter resistors in the LTP pair will reduce gain a bit
while making it even easier to achieve close 50%-50% balance of the current in the differential pair.
While changing from only one resistor to VAS to use of a current mirror
may seem like a very small change,
it will have a considerable impact on the overall circuit.
But mainly this change will improve the electrical performance.
What it will do to perceived sound, I cant tell.
Hopefully will still give pleasure to listeners
He tried Lineup, of course he did...and i have tried too
Do not sound better line up.... i have made and compared with the standard Aksa... have made into my amplifier too.. the bootstrap sounded better.
Your suggestion will measure better...instruments will dance... Hugh amplifier and a lot of other folks do amplifiers for humans to dance.
Of course was tested.... do that you too... build a bootstrapped one and built another one with your improvements..then call other guys to evaluate..blind testing to be fair..not you!....if you make it we gonna have a change that "Human biased factor" will influence evaluations.... those things we do not need to discuss or believe one to each other..just hold soldering iron and build units and test them.... easy... half day working.
Off course, to spend only a couple of hours you may have to accept prototype dirty construction...P2P or something alike, nothing to a beauty contest... a male amplifier for a macho man doing a serius research, not to show pretty pictures.... doing to increase know how....to know real thing in place to imagine or accept numbers as answers.
regards,
Carlos
Do not sound better line up.... i have made and compared with the standard Aksa... have made into my amplifier too.. the bootstrap sounded better.
Your suggestion will measure better...instruments will dance... Hugh amplifier and a lot of other folks do amplifiers for humans to dance.
Of course was tested.... do that you too... build a bootstrapped one and built another one with your improvements..then call other guys to evaluate..blind testing to be fair..not you!....if you make it we gonna have a change that "Human biased factor" will influence evaluations.... those things we do not need to discuss or believe one to each other..just hold soldering iron and build units and test them.... easy... half day working.
Off course, to spend only a couple of hours you may have to accept prototype dirty construction...P2P or something alike, nothing to a beauty contest... a male amplifier for a macho man doing a serius research, not to show pretty pictures.... doing to increase know how....to know real thing in place to imagine or accept numbers as answers.
regards,
Carlos
The use of a mirror might double gain, but improves CMRR
over just resistors.
Would be like not using a current source on the other side
of the LPT.
Its all about keeping "them dirty rails" away from our input
stage.
So the diode is not bad and would NOT create gross linearity
problems?? (I just want to try it without major board changes)
OS
Ok, most posts in this thread regarding current mirrors have mysteriously been split to here:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=133018
http://www.diyaudio.com/forums/showthread.php?s=&threadid=133018
G.Kleinschmidt said:
I assume your simulation also used a low capacitance diode.
Thinking about this further I tend to agree with your analysis.
As you pointed out, the lowest capacitance would be the most optimum because the signal current peaks can diminish the LTP currents to near zero thereby reducing the reference base current to near zero (at -ve current peaks). As the diode current approaches zero the dynamic resistance also approaches infinity. This should have the effect of making the mirror a little more sluggish but to just what extent obviously depends heavily on junction capacitance and perhaps also on VAS / LTP gain distribution, and even the load impedance. You would want LTP emitter degeneration and the smallest workable Cdom to minimise working into the undesired region.
At this point I'm going to actually modify my amp with CB diode and with the 3rd transistor + resistor and will report back on what the sonic differences are - if any.
VM
VHF man said:
All this theorisation has been great - but no real answers - so I
simulated that mirror - with and without diode - actually in an
amplifier running 35V pk OP swing at 20kHz.
I designed up a quick and dirty ULD (theoretical) design for the
purpose. I figured it needed decent linearity to show any effects
from the mirror.
Results:
35V pk / 4 ohms / 20kHz / no diode / THD = 0.000107%
35V pk / 4 ohms / 20kHz / 4148 diode / THD = 0.000107%
In isolation, the mirrors do measure differently. The more CM
voltage is applied the worse the diode model gets. With zero
CM voltage and only differential voltage the diode wins.
However, in the context of an amp, all the other non linearities
appear dominant.
cheers
Terry
OK that was interesting.
With CB diode (IN914) the treble seems slightly softer but nicer overall than the typical CB short. The 3 transistor + resistors also sounds nicer than a shorted CB but there's a tad more air and immediacy than a diode on its own. I think this is the best sounding of the 3. The current mirror devices are MPSA-18 and the mirror bias transistor is a 2N2240. LTP are 2SA970. The LTP is fed from a 2 transistor current source.
FTR IMO, the CB shorted mirror presents a slightly etched signature in the treble but this may be induced by aspects of my amp's design so feel free to maje your own judgements.
FTR the system used for evaluation is comprised of Infinity Renaissance 90 speakers that have been modded with RAAL tweeters and Mundorf caps + inductors. The CD player is a Marantz SA-11 and the preamp a Krell KSP-7B modded with Elna Silmic's. For comparative purposes I use a Meridian 556 commercial amp. FWIW Meridian sounds very inferior at HF compared to the DIY amp. It's really chalk and cheese. I have no idea of this amp's design but it has the reputation of a good all round performer.
With CB diode (IN914) the treble seems slightly softer but nicer overall than the typical CB short. The 3 transistor + resistors also sounds nicer than a shorted CB but there's a tad more air and immediacy than a diode on its own. I think this is the best sounding of the 3. The current mirror devices are MPSA-18 and the mirror bias transistor is a 2N2240. LTP are 2SA970. The LTP is fed from a 2 transistor current source.
FTR IMO, the CB shorted mirror presents a slightly etched signature in the treble but this may be induced by aspects of my amp's design so feel free to maje your own judgements.
FTR the system used for evaluation is comprised of Infinity Renaissance 90 speakers that have been modded with RAAL tweeters and Mundorf caps + inductors. The CD player is a Marantz SA-11 and the preamp a Krell KSP-7B modded with Elna Silmic's. For comparative purposes I use a Meridian 556 commercial amp. FWIW Meridian sounds very inferior at HF compared to the DIY amp. It's really chalk and cheese. I have no idea of this amp's design but it has the reputation of a good all round performer.
thanks Terry for that analysis. I'll need to think about why the CM Vs Diff dominance produces those results. Actually the lack of any real measured difference is not unexpected and ties in with some live measurements I made on a diy preamp a few years ago. Both with and without a diode gave identical results on my pc based analyser. Either way the THD+N was below -110dBr0 at all tested frequencies (1 -10 KHz).
Cheers,
V man
Cheers,
V man
G.Kleinschmidt said:
Yes but you might start to impare the speed of the device at very high currents. It's a moot point anyway becaue the 3 T solution is the obvious way to go.
I see that this thread was moved, but in any event the topic is, or should be resolved. Thanks for your input.
Cheers,
vm
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