AudioFreak said:
Sure. But the main allure is that you get everything done with a single solution. Want more power? Get a bigger chip. Here, try this guy:
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<img src="http://216.253.197.8/mainsite/products/pages/opimages/pa03.jpg">
</center>
Make yourself a 1,000 watt Gainclone.
Though technically it's not a "chip amp" in that it's hybrid rather than monolithic.
se
I believe Nelson Pass gave the beginning to a similar project, although with different chips.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=11205
http://www.diyaudio.com/forums/showthread.php?s=&threadid=11205
leadbelly said:
What I meant was that the underlying philosophy behind the Gaincard from whence all the varied and sundry Gainclones have sprung has been simplicity. Remember? "Only the simplest can accommodate the most complex"?
That's all I'm getting at. Not saying everyone has to stick to that philosophy.
Maybe this is the hot new area? A fully complementary output stage?
Well, if you go with a hybrid device (not necessarily the PA-03, the PA-02 and PA-16 are much more affordable), you'll have a fully complimentary output stage.
se
Variac said:
The PA-03 is as simple as any other power opamp. Just a few external parts, a power supply, bolt it to a heatsink and you're done. The only difference is that the PA-03 is a hybrid device instead of monolithic and it can shove up to 30 amps of current down the throat of your your load.
se
Re: Re: Adding Output Transistors to LM3875???
amplifier.
Not completely. When you are drawing up a completely new amp from scratch, at first you can't be sure anything works properly. If you build it around an amp chip at least that part of it is completely debugged giving you a better chance of getting the whole thing going. After you have been emboldened by conquering *this* project, then you can go on to make a *real*Steve Eddy said:
amplifier.
Re: Re: Re: Adding Output Transistors to LM3875???
But that will anger the spirit of Gaincard. Bad ju-ju. Will require many virgin sacrifices.
se
Circlotron said:Not completely. When you are drawing up a completely new amp from scratch, at first you can't be sure anything works properly. If you build it around an amp chip at least that part of it is completely debugged giving you a better chance of getting the whole thing going. After you have been emboldened by conquering *this* project, then you can go on to make a *real*
But that will anger the spirit of Gaincard. Bad ju-ju. Will require many virgin sacrifices.
se
SE: I wasn't clear at all. I do like that all in one Apex chip.
Do you think it would be the ticket for a fan cooled PA amp?
BUT when I mentioned using a chip amp as the first stage in an amp I meant the original idea with discrete output devices.
I was pointing out that Apex is a bit pricey- is there a cheaper alternative by using a hybrid approach-could the parts count still be kept to about 10 components?
Here is one answer, but it has only been heard by it's designer at this point- not a very big sample
http://www.diyaudio.com/forums/showthread.php?s=&postid=171157#post171157
Do you think it would be the ticket for a fan cooled PA amp?
BUT when I mentioned using a chip amp as the first stage in an amp I meant the original idea with discrete output devices.
I was pointing out that Apex is a bit pricey- is there a cheaper alternative by using a hybrid approach-could the parts count still be kept to about 10 components?
Here is one answer, but it has only been heard by it's designer at this point- not a very big sample
http://www.diyaudio.com/forums/showthread.php?s=&postid=171157#post171157
Variac said:
Actually I was only being facetious about the PA-03. That 1,000 watts is rather misleading. The PA-03's maximum power supply voltage is +/- 75 volts. Even if it could swing the whole 75 volts, into an 8 ohm nominal load, that's only about 350 watts. Though into a 4 ohm load it'd be about 700 watts which is a bit closer to 1,000 watts.
Though if that's something you'd want in a PA amp, the PA-03 would offer a rather simple, if rather expensive solution. I mean, you're talking over $600 just for a pair of those critters and that doesn't count the power supply, heatsinking, chassis, etc.
It all really depends on what exactly it is you want to achieve.
Tacking on some output transistors really only gives you the ability to source more current which would only be of benefit if you needed to drive lower impedance loads. Remember, the 3875 can only swing so much voltage and a follower on the output isn't going to give you any voltage gain.
At least that's for a single device. Output followers would help with a bridged configuration, allowing more current so you wouldn't have to parallel multiple devices to handle the additional current required by bridging.
So again, it depends on exactly what it is you're hoping to achieve.
se
jam said:
Not that I'm aware of.
What exactly are you expecting a Vbe multiplier to do in this instance? Are you ulitmately just wanting to add another voltage gain stage between the opamp and the followers?
If so, now you're yet another step closer to a discrete power amp.
How 'bout just using a high voltage power opamp instead?
se
jam said:
Ah, ok.
Well, you can do the kinda sorta somewhat class A trick with a power opamp same as with other opamps if you want kinda sorta somewhat class A.
Anyway, don't mean to come off as such a wet blanket on this issue, but it's a bit like adding a bunch of band-aid solutions instead of just getting the solution you want from the start.
Okie doke. Transformers aren't cheap and they're not to everyone's liking so a good period of deliberation is definitely a good thing. Ewwww. Did I just utter a Martha Stewart catch phrase?
Excuse me while I go wash my mouth out with soap.
se
Careful Steve! I am more concerned about you sounding like Fred than Martha Stewart.......
Since you work for Coda how about starting a new thread about their ideas. I am paticularly interested in their use of a control amp driving a buffer situated close to the speakers and zero (global feedback) designs.
Regards,
Jam
Since you work for Coda how about starting a new thread about their ideas. I am paticularly interested in their use of a control amp driving a buffer situated close to the speakers and zero (global feedback) designs.
Regards,
Jam
jam said:Careful Steve! I am more concerned about you sounding like Fred than Martha Stewart.......
WILLLLLLLLMMAAAAAAAAAAAAA!!!!!!!!
Oops. Wrong Fred.
Ugh. That'd be too much like work.
Besides, I don't think it would be very appropriate. It smacks too much of commercial exploitation, particularly given that The Powers That Be at Coda aren't too keen on making schematics and whatnot available to the public.
The control amp/buffer scheme is really nothing more than a matter of geography. The System 100 and System 200 are fundamentally no different from our regular stereo amps. Just that everything upstream of the output stage is placed in a separate chassis. Something most any DIYer can pull off with most any discrete amplifier circuit.
se
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