chipamp pcb?

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CJ900RR

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Looks like it follows Nationals standard circuit, should sound "normal". Would not recommend them for a BPA300 design cause they dont have any output resistors, no zobel network and no DC-circuit. They would most likely oscillate (spelling?), overheat and burn if paralleled.

Im working on a pair of boards, not finnished yet. Might order in a week or so.
 

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coldfuzion76

coldfuzion76

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Joined 2008
yeah, i knew about the output resistors, was going to add them externally. I'm new to this stuff, though and didn't know about the other stuff. I actually originally started out just going to build a simple amp, but then I got this great deal on a dual center tapped 1000va transformer, and I got some killer older 12" Kenwoods to drive now. Figured I needed to ramp it up a bit.
 
Tripmaster

Tripmaster

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Joined 2008
Gainclone PCBs

I am hoping some of you may be able to help. I am new to Gainclones and electronics.

Does any one know if I can buy the Chipamp.com or Audiosector.com PCBs in the UK? It would be easier to follow one of these kits.

I am really keen to make my own PCBs if someone has a simple yet reliable PCB design I could use.

I have purchased some copper boards and intend using the photo glossy paper method.

Which size toroidal transformer will give me the greatest flexibility with future upgrades? I have seen some at http://www.airlinktransformers.com/toroidal-transformers.asp

Which amp configuration will best suit my these speakers?

B&W DM601 S2
Crossover is at 4 kHz, efficiency is rated at 88dB/1W/1m, Impedance is said to be 8 Ohms nominal, 4.3 Ohms minimum
Response 70Hz-20kHz +/- 3dB on axis
Harmonic distortion below 1% 88-20.000 Hz at 90dB SPL at 1m.
Power handling is said to be 25-100W continuous of unclipped programme into 8 Ohms nominal

I really appreciate your help.
 
coldfuzion76

coldfuzion76

Member
Joined 2008
Ok, so here's a question. I already have a couple of Peter Daniel's boards. If I got some more of those and used the Zobel option, and then added the output resistors externally, would that prevent the oscillation? I may not go for the full 300, I was thinking more of only using 4 chips per channel.
 
jackinnj

jackinnj

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Joined 2002
tech-diy.com
coldfuzion76 said:
Ok, so here's a question. I already have a couple of Peter Daniel's boards. If I got some more of those and used the Zobel option, and then added the output resistors externally, would that prevent the oscillation? I may not go for the full 300, I was thinking more of only using 4 chips per channel.
Click to expand...

Yes, you can use the inductor externally -- it (or the Zobel) should be close to the LM3875 or LM3886.

Use a 1/2 dowel as a form to wind 10 turns of #18 magnet wire as the inductor -- you can even use RS PVC insulated wire -- slip a 10 ohm resistor through the coil -- this will lower the coil's "Q" dramatically
 
C

CJ900RR

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Joined 2006
vectorplane said:



What do you mean by "DC-circuit" ?

I'm reading the National literature, trying to understand this, but they don't mention any DC circuit.
Click to expand...


Sorry, my bad. I should have written "servo circuit" witch is the correct name for it. Instead of using cap's to minimize DC-offset, you can use OP-amps to keep it low. Look at Nationals AN-1192 (http://www.national.com/an/AN/AN-1192.pdf) at page 13.
 
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gainmona

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vectorplane

vectorplane

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Joined 2005
CJ900RR said:



Sorry, my bad. I should have written "servo circuit" witch is the correct name for it. Instead of using cap's to minimize DC-offset, you can use OP-amps to keep it low.
Click to expand...

Oh, a servo circuit. I see

I know about the National paper on using multiple chips, but this is a single-chip amp.

I've bought boards from Peter Daniel, and Chip-Amp before, but I don't know if they have this "servo amp" on them.

I'll have to check when I get home.
I'll have to check to see if they have the Zobel as well.

Cheers
 
coldfuzion76

coldfuzion76

Member
Joined 2008
I have both now, and they don't include the servo, but they do have the zobel. I bought 6 of BrianGT's boards to use in my amp, and I have a quick question, Would I want to use the zobel on every board or just connect one single one after the resistors on the output? I'm going to use 3 per channel.
 
vectorplane

vectorplane

Member
Joined 2005
Sorry to be an idiot.
Help me understand this:

If you parallel 3 amps per channel, is it because you want to drive loads lower than 4 ohms?
Or you just want a wider margin of safety?

Or do the chip amps have better THD performance if you keep each one working at a lower current level?
 
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