An externally hosted image should be here but it was not working when we last tested it.
Current Feedback Amplifier with Compensation
Stephen W. Moore
Current Feedback Amplification
🙂
I found a schematic of
The Elektor Current feedback amplifier based on NE5534 Op-Amp.
This is the one I refered to earlier in this thread.
It is from 1987. 20 years ago.
My guess was 15 years ago ......
The full article is here:
http://users.otenet.gr/~athsam/power_amplifier_for_loudspeaker_6W_8R.htm
The text is in a foreign language.
It is plain Greek to me 😉
But there is an English translation, as well!
You have the component values in the Parts List.
lineup
I found a schematic of
The Elektor Current feedback amplifier based on NE5534 Op-Amp.
This is the one I refered to earlier in this thread.
It is from 1987. 20 years ago.
My guess was 15 years ago ......
The full article is here:
http://users.otenet.gr/~athsam/power_amplifier_for_loudspeaker_6W_8R.htm
The text is in a foreign language.
It is plain Greek to me 😉
But there is an English translation, as well!
You have the component values in the Parts List.
lineup
Here are some pictures of the amp prototype.
A pair of boards, each a monoblock, will be used in a pair of active speakers I'm setting up.
The output stages are very sloppy looking, but that's because they are only for testing. When I have the hardware to mount proper heatsinks I'll be doing that and in a much neater fashion. I'll also be going to an adjustable Vbe multiplier to set the output bias instead of diodes.
A pair of boards, each a monoblock, will be used in a pair of active speakers I'm setting up.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
The output stages are very sloppy looking, but that's because they are only for testing. When I have the hardware to mount proper heatsinks I'll be doing that and in a much neater fashion. I'll also be going to an adjustable Vbe multiplier to set the output bias instead of diodes.
I present my schematic, hand drawn and scanned, of the working prototype as it stands.
An externally hosted image should be here but it was not working when we last tested it.
I prefer your schematic
to the Elektor.
It is not here easiest thing to get it work
when using output taken from Collectors of Power transistors.
Also very tricky to use the supply pins of Op-Amp, to bias these transistors.
A normal power follower stage, like yours, is a good way.
And a bit easier to get to work in a proper way.
What transistors you use?
Maybe you have told already, but I missed this information.
to the Elektor.
It is not here easiest thing to get it work
when using output taken from Collectors of Power transistors.
Also very tricky to use the supply pins of Op-Amp, to bias these transistors.
A normal power follower stage, like yours, is a good way.
And a bit easier to get to work in a proper way.
What transistors you use?
Maybe you have told already, but I missed this information.
I didn't mention which transistors I'm using in the amp.
All of the signal transistors are MPSA42, and the outputs are C3039 and A1077.
I know they are not a proper complimentary pair, but an intention of mine was to make this whole prototype from what I had in the immediate junk bin. Being that these are emitter followers and there's plenty of feedback, I'm not going to worry much about that right now. It's what I had on hand and it seems to perform very well anyway.
All of the signal transistors are MPSA42, and the outputs are C3039 and A1077.
I know they are not a proper complimentary pair, but an intention of mine was to make this whole prototype from what I had in the immediate junk bin. Being that these are emitter followers and there's plenty of feedback, I'm not going to worry much about that right now. It's what I had on hand and it seems to perform very well anyway.
An update:
The Transconductance boards are now in their intended application: Active amps inside a set of monitors.
In order to surprise myself, and others, I have use a pair of the sort of cheap speakers that came with a Sears all-in-one stereo from the seventies. Not bad as far as cabinets go, of course in brown with ugly brown grille cloth.
The driver compliment is what appears to be a semi-full-range 6x9 driver along with a pair of cheap 2" paper tweeters on a single capacitor filter.
I've disconnected the tweeters completely, and removed the backs of the speakers to allow for almost completely free-air loading.
The amplifiers each sit in the speaker cabinets and at the moment are powered from an external power supply located on the floor. (Later each speaker will have its own suppy but that has to wait until I have two sets of filter caps handy.)
The results are nothing short of amazing. I've had various people come listen and the term reference-monitor usually comes up.
They need a tiny bit of rise in the high end, but not as much as one might expect. The bass is extremely full and extends nicely quite low. Only a bit more extension is needed for true full range sound.
The mid and high range is where these are phenomenal. I can tell nothing of coloration to speak of, and not just me; my other auditioners mention the same thing.
Luckily, this experiment has really come off. They are now performing as my main system here in my basement suite while I live away from home for university.
The next installment shall involve adapting the amplifiers for continuously variable output impedance to even better damp the speakers. A later trial will be to add a very finely adjusted filter network on the amplifier board so that the speakers' high end is made inherently flat. This way, I need nothing at the signal source to tune the high end anymore. (Even running flat they sound excellent, but just need a tiny bit more detail. Something like a two pole 4dB/oct that has its low 3dB point at 15k and levels off at 20k is how I have my EQ set.)
More later!
The Transconductance boards are now in their intended application: Active amps inside a set of monitors.
In order to surprise myself, and others, I have use a pair of the sort of cheap speakers that came with a Sears all-in-one stereo from the seventies. Not bad as far as cabinets go, of course in brown with ugly brown grille cloth.
The driver compliment is what appears to be a semi-full-range 6x9 driver along with a pair of cheap 2" paper tweeters on a single capacitor filter.
I've disconnected the tweeters completely, and removed the backs of the speakers to allow for almost completely free-air loading.
The amplifiers each sit in the speaker cabinets and at the moment are powered from an external power supply located on the floor. (Later each speaker will have its own suppy but that has to wait until I have two sets of filter caps handy.)
The results are nothing short of amazing. I've had various people come listen and the term reference-monitor usually comes up.
They need a tiny bit of rise in the high end, but not as much as one might expect. The bass is extremely full and extends nicely quite low. Only a bit more extension is needed for true full range sound.
The mid and high range is where these are phenomenal. I can tell nothing of coloration to speak of, and not just me; my other auditioners mention the same thing.
Luckily, this experiment has really come off. They are now performing as my main system here in my basement suite while I live away from home for university.
The next installment shall involve adapting the amplifiers for continuously variable output impedance to even better damp the speakers. A later trial will be to add a very finely adjusted filter network on the amplifier board so that the speakers' high end is made inherently flat. This way, I need nothing at the signal source to tune the high end anymore. (Even running flat they sound excellent, but just need a tiny bit more detail. Something like a two pole 4dB/oct that has its low 3dB point at 15k and levels off at 20k is how I have my EQ set.)
More later!
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