Amp Camp Amp - ACA

I’m sorry Nelson I was being sarcastic there when I said the amps are similar because they both use resistors and semiconductors. It should also be pointed out that the polarity on my schematic is also wrong. Perhaps it’s best to think of it as the bottom (negative side) of an F5.

B.T.W.
You have stated:

Consider the two power resistors going from the Source of the CS to the
Drain of the primary gain device. The voltage across these resistors and
their added resistance sets the DC bias of the current source. Where you
tap between them sets the gain. You could easily imagine a string of 0.1
ohm resistors, 10 in series forming 1 ohm but the output to the load is
tapped arbitrarily. Then you can adjust to your heart's content either for
low distortion or a particular ratio of 2nd to 3rd harmonic.
:cool:


Would I be right in assuming tapping it closer to Q1 produces more 2nd harmonic and closer to Q2 produces more 3rd harmonic ? (Just guessing here)


I always like to speculate as to your motivation for picking a particular topology. Though I guess if everyone just used the basic diff-pair -> voltage gain -> follower topology it would be a fairly boring world which would sound mostly the same. You have probably forgotten more topologies then I ever understood and most of the ones I have learned about have been from your articles. Would I be correct that you had a dream about riding on the back of a seahorse through a kelp forest triggered by latent memories from childhood camping trips as the motivation for making R1 0.47 Ohms or did you just have a lot of them laying around?

Leve
 
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no xover at all

:rofl:

(OK - you can sneak one simple cap and just maybe one resistor in )
Your statement applies only to a wide-band [full range] single driver. An earlier thread recommended [to the novice DIYer] using the Emken loudspeaker which fits this description. Your statement is valuable nonetheless. Now you are giving the DIYer specific and much needed advice. Still, a full range or multi way drivers maybe a boxed loudspeaker. The low DF of the Camp Amplifier may require suggesting an optimal Qts for the loudspeaker. What can/should it be; under, critical or over damped so as to squeeze the best performance there is of the ensemble?
 
The one and only
Joined 2001
Paid Member
Would I be right in assuming tapping it closer to Q1 produces more 2nd harmonic and closer to Q2 produces more 3rd harmonic ?

I always like to speculate as to your motivation for picking a particular topology.

...as the motivation for making R1 0.47 Ohms or did you just have a lot of them laying around?

1) I wouldn't assume too much, as it depends on everything. There
generally will be a sweet spot where the 2nd nulls and where the total THD
is lowest, and on either side of that the 2nd comes back.

2) The topology chooses me.

3) I have lots of them, but it's a convenient value.

:cool:
 
Official Court Jester
Joined 2003
Paid Member
easy

just use T0-220 cased mosfets , set current to ~70mA

Voila!

make R1 // R2 = 3R8

make R3 // R4 = 5R5

or so

math is simple

in case that you want bigger current , calc Iq as 0V65/ ((R1//R2)+(R3//R4) and maintain same ratio between these two groups

IRF510 , IRF610 are good candidates ..... or fancy Toshiba ones
 
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Official Court Jester
Joined 2003
Paid Member
difference between 0V55 and 0V65 is bias difference between 478mA and 565mA ..... so , around 16% increase

which one will be better to your ears ......... well - those are your ears :clown:

Mighty Dumb ZM ;

didn't saw that there are 2 pcs of 0R47 and 0R68

so - current is double ....... say 0V65/((0R47+0R68)/2) = 1A13

so , dissipation is in range of 21W5

:rofl:
 

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I think this would be a good intro. THere is a thread with the Tilte EMKEN. Check it out.
Great advice. Zen Mod agrees with you [several threads earlier] to use a full range like the Emken as you suggested to mate with this Camp Amp. I checked the Emken site; but JRKO did not mention the amplifier [I probably missed it] he used to drive his loudpeaker creation. Does anyone else know the nature of JRKO's amp? Is it a voltage or a modulated current source?
 
diyAudio Editor
Joined 2001
Paid Member
Papa sez it would be easy to change the feedback of the amp to get 6.5 ohm output resistance. Then it would work perfectly with this awesome full ranger:

http://www.diyaudio.com/forums/diyaudio-com-articles/158899-arpeggio-loudspeaker.html

the new version of the Fostex driver is very similar to the old but not identical. We should check the math and see if it is significant. He gave us all the tools

Whao; a one-stop experience/diy article to understand, appreciate and build an awesome full range loudspeaker to mate with the Camp Amp.
 
The one and only
Joined 2001
Paid Member
A thumbnail calculation sez that R12 = 100K would just about do it.

I often quote myself as I find it adds spice to my conversation. ;)

Oh look! I found a couple of stills from the Amp Camp footage.

On the left, moderator Variac and on the right Jason, the founder of DIYAudio.

:cool:
 

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Funny you should ask about the 3PD02200. In my testing, it's typically 20'C above the ambient temperature, plus or minus 2'C.

My Hero.

Goes to show what the Modushop heatsinks are really capable of, diddly squat better than e.g. a Fischer SK47.
Aka 1C/W for 80mm implies that the 200x40x210 mm heatsinks can do no better than 0.60C/W (and the 250mm wide no less than 0.50C/W)