Class A
I am only posting this here because, for the life of me, I cannot find a "New Post / New Thread" tab anywhere, sorry.
I remember that in the late 70s or 80s there was in one of Popular Electronics - Audio - Stereo Review a Class A amp project. I tried to find it on the net, looked up collections of magazines and got nowhere.
Does anyone know what I am talking about or where I can find a copy of?
I recently came across a bunch of attractively shaped massive heatsinks (actually from JVC D-ILA projector lamps) and thought I could fashion them into a wasteful class A amp...for cold winter nights.
I am only posting this here because, for the life of me, I cannot find a "New Post / New Thread" tab anywhere, sorry.
I remember that in the late 70s or 80s there was in one of Popular Electronics - Audio - Stereo Review a Class A amp project. I tried to find it on the net, looked up collections of magazines and got nowhere.
Does anyone know what I am talking about or where I can find a copy of?
I recently came across a bunch of attractively shaped massive heatsinks (actually from JVC D-ILA projector lamps) and thought I could fashion them into a wasteful class A amp...for cold winter nights.
i dont really understand what is Highly recommended German Amplifier Schematic ! when is working with Highly dead semiconductors and Highly dead schematic ....
what i am trying to say is that teqniques like the above have been tested and failed so many times in the past due to so poor Darligton performance that strugle to keep safe with a full time VI limmiter that might works but kills all your sonics ( at least the above apply to a hifi or even a high end amplifier )and is absolutelly unaxeptable
cause if we talk anything more like a very light PRO use its simply out of the question ....
on the other hand this looks like a version of the ILP modules ....( also RIP ) that have been performing a bit ( no vi limmiter i think ) but having a reputation on failing so easy
so whats the catch here ????
what i am trying to say is that teqniques like the above have been tested and failed so many times in the past due to so poor Darligton performance that strugle to keep safe with a full time VI limmiter that might works but kills all your sonics ( at least the above apply to a hifi or even a high end amplifier )and is absolutelly unaxeptable
cause if we talk anything more like a very light PRO use its simply out of the question ....
on the other hand this looks like a version of the ILP modules ....( also RIP ) that have been performing a bit ( no vi limmiter i think ) but having a reputation on failing so easy
so whats the catch here ????
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Hi,
help needed! If that thing should be generally regarded as a masterpiece of german engineering I´d like to emigrate and humbly search for asylum
jauu
Calvin
Tried the 7 .. garbage!!!! so if it is the same , then it is a waste of time .......
Darlington was not bad if you smart and inteligent enough
This model used 4 Pairs of darlington type and they're enough for 120Wrms.
Please see my first picture I found something wrong, a correct schematic used 45V zener diode in a palce of 1N4148 he he he)
I got this schematic from service manual of these module.
Now it work fine with my Pass X0.2 preamp, too (Do you like to see my copy ?)
Thanks
Anadigit
This model used 4 Pairs of darlington type and they're enough for 120Wrms.
Please see my first picture I found something wrong, a correct schematic used 45V zener diode in a palce of 1N4148 he he he)
I got this schematic from service manual of these module.
Now it work fine with my Pass X0.2 preamp, too (Do you like to see my copy ?)
Thanks
Anadigit
work fine ???? how come ???? its like you have a Mercedes with wheels from skateboard .....
get your shelf a DX amplifier a P3A or anything like that make a blind test and get back to us
the only way that your amp is better is probably a bit more diry power ....
I wonder doesnt ring a bell to you that there is NOT EVEN ONE comercial design builted like that ????
Please explain me everything which you mark as "skateboard"
Do you ever listen to it before, as same as fox and sour grapes
Thanks
Anadigit
if you have the time i can explain you a number of reasons why an amp like that suffers of a number of problems ....
---Darligtons are very nice ...with B1000 or more are very easy to drive ... bearly an OP amp is enough ...BUT !!!
--- devices with so much gain suffer from drive and temprature issues like : if one is driven by any tolerance 3% more calculate this with times B1000 and check the result ...then again if for any reason one of the tranistors has more or less colling where its installed warm up a bit more than the others calculate the error by a high gain device and check the results .... a warmer device will drain more power than a cooler one
----then again in any case any slight oscillation is present either this is coming allready from the amplifier or else where a very high gain device obviously will multiply this more than any other tranistor ....
---- same goes if you need to drive a very reactive load or very long cables a high gain device will suffer more than a low gain device ....
---- Draligton behaviour cause all the above is almost unpredictable ...of course using high quality semis will help but will not solve the problem
----finally the cure is very simple ::: use a sophisticated VI limmiter to guard the drive and be on the safe side ....well for your information this limmiter has to be very very sophisticated +multislope + multi sense ( from all transistors ) to be able to protect the amp properly and still have as less effect is possible to sound ....Presumably that is NOT your case .....
there is actually no point on looking on soa plots of the specific darligton device or Ft ....i take it as a fact that a modern device will perform about 100 times better
it could be more but this what comes up with the first few thoughts
---Darligtons are very nice ...with B1000 or more are very easy to drive ... bearly an OP amp is enough ...BUT !!!
--- devices with so much gain suffer from drive and temprature issues like : if one is driven by any tolerance 3% more calculate this with times B1000 and check the result ...then again if for any reason one of the tranistors has more or less colling where its installed warm up a bit more than the others calculate the error by a high gain device and check the results .... a warmer device will drain more power than a cooler one
----then again in any case any slight oscillation is present either this is coming allready from the amplifier or else where a very high gain device obviously will multiply this more than any other tranistor ....
---- same goes if you need to drive a very reactive load or very long cables a high gain device will suffer more than a low gain device ....
---- Draligton behaviour cause all the above is almost unpredictable ...of course using high quality semis will help but will not solve the problem
----finally the cure is very simple ::: use a sophisticated VI limmiter to guard the drive and be on the safe side ....well for your information this limmiter has to be very very sophisticated +multislope + multi sense ( from all transistors ) to be able to protect the amp properly and still have as less effect is possible to sound ....Presumably that is NOT your case .....
there is actually no point on looking on soa plots of the specific darligton device or Ft ....i take it as a fact that a modern device will perform about 100 times better
it could be more but this what comes up with the first few thoughts
There is no comparison, all the stuff by DX are entry-level DIY projects with evident design mistakes from someone with huge enthusiasm but nothing else (except a flat learning curve, ie: no ability to learn anything new). When you look at DX schematics, you never know if he is reinventing electronics/physics laws, if he is kidding, or if he just does not know what he is doing.
P3A comes from someone with an open and scientific mind (who does far more things than just bipolar class AB amplifiers, the list of projects is always growing) trying to make a simple yet well behaved circuit with classic parts. It's far better.
The amplifier described in this thread looks like a travel in time back to the best 1985 high end audio. The travel costs $4000 and the other $1000 is the cost of the amplifier (I suppose splif were invented to do similar travel without expending that much money
).No, innovation works that way. There is always a first time, when something good and new is put together. I'm working on innovative stuff, circuits that don't look like anything else on the market, with innovative performance too. When I find myself doing something that does not satisfy this criteria, it means that I'm doing it the wrong way. The funny case is when you put together something that would only have been innovative 25 years ago.
BTW: 0.006% THD at 50W/4 ohm is not bad at all, it's quite good, considering that THD figures from DX stuff are never published and are probably 5-10 times worse.
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Comparisons are dangerous.
At least, the amplifier discussed in this thread seems to have some careful electronic/mechanical design work and engineering behind. Also, I suppose they don't use boom-box speakers with paper cone tweeters to evaluate its "sonic qualities" (like the ones shown in DX threads).
In P3A schematic, the current source feding the LTP is a true current source, not a capacitance multiplier made by mistake. There are no useless capacitors and resistors spread across the circuit either (that are later removed because they are found to reduce phase margin).
If you want it stable into capacitive loads, add the usual coil-paralleled-with-resistor in series with the output. But don't place the coil near the LTP or the VAS, and don't put the coil in the same spatial plane PCB traces are laid out, or you will have problems like DX, requiring an improvised shield! (until a new PCB is laid out with all these mistakes corrected).
Professional work is not the same as trial and error work from someone that is trying random ideas and learning.
At least, the amplifier discussed in this thread seems to have some careful electronic/mechanical design work and engineering behind. Also, I suppose they don't use boom-box speakers with paper cone tweeters to evaluate its "sonic qualities" (like the ones shown in DX threads).
In P3A schematic, the current source feding the LTP is a true current source, not a capacitance multiplier made by mistake. There are no useless capacitors and resistors spread across the circuit either (that are later removed because they are found to reduce phase margin).
If you want it stable into capacitive loads, add the usual coil-paralleled-with-resistor in series with the output. But don't place the coil near the LTP or the VAS, and don't put the coil in the same spatial plane PCB traces are laid out, or you will have problems like DX, requiring an improvised shield! (until a new PCB is laid out with all these mistakes corrected).
Professional work is not the same as trial and error work from someone that is trying random ideas and learning.
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P3A was choosen by a costumer of mine .... cause he listen to at home and said to me that this is the amplifier i would like to have in my Italian restaurant
3 stereo amplifiers where constructed based on rod's schematic ( just a few minor changes mostly regarding the pcb ) each amplifier is working in 4 Ohm load driving stereo 4 speakers each a total load of 12 speakers for 3 stereo amps ....
you can imagine that we talk about distance of 40 or 50 meters from the amplifier with very cr***py 2X0.75 cable that was installed from the electrician of cource all cables run together with electric telephonelighting and dimmers or any other cables you can imagine
for more technical amplifier still has no inductor in the output and the duty weekdays is to play background music no heavy loads but arround the weekend the units as is work as a "support " to a small live band that is working there with Italian music ...
By the way all systems is female waitress operated and probably blond meaning that whens she shuts down the PC or CD player she things that all music systems ar off ...
that means that amplifiers are working 24/7 for 2.5 years now ...
it will not get mor "capacitive " than that ....ever ....
3 stereo amplifiers where constructed based on rod's schematic ( just a few minor changes mostly regarding the pcb ) each amplifier is working in 4 Ohm load driving stereo 4 speakers each a total load of 12 speakers for 3 stereo amps ....
you can imagine that we talk about distance of 40 or 50 meters from the amplifier with very cr***py 2X0.75 cable that was installed from the electrician of cource all cables run together with electric telephonelighting and dimmers or any other cables you can imagine
for more technical amplifier still has no inductor in the output and the duty weekdays is to play background music no heavy loads but arround the weekend the units as is work as a "support " to a small live band that is working there with Italian music ...
By the way all systems is female waitress operated and probably blond meaning that whens she shuts down the PC or CD player she things that all music systems ar off ...
that means that amplifiers are working 24/7 for 2.5 years now ...
it will not get mor "capacitive " than that ....ever ....
You better not tell that to Rod Elliot, but your e wrong here. I helped my sisters 12 year old kid put one together and did some testing like I do on my own designs, yes it can handle capacitive loads even when built by a 12 year old.
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