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Commercial Gainclone kit- building instructions

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samsagaz

Member
Joined 2004
Peter Daniel said:
I'm using my standard chassis and start with mounting the chip to copper heatsink. The chip case is not insulated, so isolation pad is required as well plastic washers under the mounting screw (an aluminum oxide pad was used here).

I also install 3 famous resistors: 22K for input shunt and feedback and 1.5K gain setting Riken. The customer asked for lower gain that's why I didn't use 680R as usually.

You can also see input wires coming from RCA socket (23awg silver wire from DH Labs) and speaker output wire (19awg Kimber TCSS)
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How you calculate the GAIN?
 
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samsagaz

Member
Joined 2004
samsagaz said:



How you calculate the GAIN?
Click to expand...


I found it...

RF/R3 :)

Now, i was reading the LM3886 Datahseet and dont understand very well wich is the diference if set an gain of 33db (using 22k and 680ohms) and if for example use other res to set it at just 15db and other resistors to get 100db gain, what will this affect the sound?

Why ppl choice close to 30db instead set an higher GAIN?
 
MrTransistorm

MrTransistorm

Member
Joined 2003
samsagaz said:
I found it...

RF/R3 :)

Now, i was reading the LM3886 Datahseet and dont understand very well wich is the diference if set an gain of 33db (using 22k and 680ohms) and if for example use other res to set it at just 15db and other resistors to get 100db gain, what will this affect the sound?

Why ppl choice close to 30db instead set an higher GAIN?
Click to expand...

First of all the gain is not in dB. 100dB is 100000x gain! :xeye: Also, in non-inverting configuration, the gain = (Rf/Ri) + 1.

You wouldn't want your power amplifier to have too much gain since this would force you to keep the volume control turned way down. My amp has a gain of 21x, and I generally have my volume control at 9 o'clock. If the gain was much higher, the volume control have to be at almost minimum. It's very touchy in that range, and channel tracking is poor.
 
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samsagaz

Member
Joined 2004
MrTransistorm said:


First of all the gain is not in dB. 100dB is 100000x gain! :xeye: Also, in non-inverting configuration, the gain = (Rf/Ri) + 1.

You wouldn't want your power amplifier to have too much gain since this would force you to keep the volume control turned way down. My amp has a gain of 21x, and I generally have my volume control at 9 o'clock. If the gain was much higher, the volume control have to be at almost minimum. It's very touchy in that range, and channel tracking is poor.
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I see. So between 20 and 30 will be an safe value :)


btw if i use an higher gain, at maximun volume, will sound louder?

Thanks guys.
 
rabbitz

rabbitz

Member
Joined 2003
No. All it will do it supply maximum power with the volume pot at a lower position. The amp can only put out so much power before the protection cuts in.

I'd rather see lower gain so the pot is at a higher position like 11-12 o'clock (where tracking is better) at listening levels.
 
MrTransistorm

MrTransistorm

Member
Joined 2003
samsagaz said:
I see. So between 20 and 30 will be an safe value :)


btw if i use an higher gain, at maximun volume, will sound louder?

Thanks guys.
Click to expand...

It will be louder, but at some point you'll run in to clipping. If your source level (CD player, phono preamp, iPod, etc.) is low, you could make the gain in the power amp higher to make up the difference.

On the other hand, if you find that it's not loud enough when it reaches clipping, then you need more power. Chip amps are good for high-efficiency speakers or moderate listening volumes on less efficient speakers. They are cheap and easy to build, but power output is limited. If you aren't getting enough power, you'll have to go with discreet components.
 
S

samsagaz

Member
Joined 2004
MrTransistorm said:


It will be louder, but at some point you'll run in to clipping. If your source level (CD player, phono preamp, iPod, etc.) is low, you could make the gain in the power amp higher to make up the difference.

On the other hand, if you find that it's not loud enough when it reaches clipping, then you need more power. Chip amps are good for high-efficiency speakers or moderate listening volumes on less efficient speakers. They are cheap and easy to build, but power output is limited. If you aren't getting enough power, you'll have to go with discreet components.
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I see, so how can i measure when the chip enter into clipping? i mean, how many Volts into the input will put the Chip into clipping using for example 30x Gain? :)

Hope understand what im asking :)
 
R

Redshift187

Member
Joined 2008
MrTransistorm said:
They are cheap and easy to build, but power output is limited. If you aren't getting enough power, you'll have to go with discreet components.
Click to expand...


Or go with multiple chips bridged and/or parallelled. I have approximately 100W per channel with my bridged LM4780 (LM3886 x2) setup (gain of 11 per channel "side" or 22 per channel total). When using my DVD player, my ideal volume is around 12 - 1 o'clock on a 50k pot without a pre-amp. I don't know EXACTLY how much power per channel as I haven't measured supply droop at full output yet.
 
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samsagaz

Member
Joined 2004
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