Parallel GAINCLONE makes diaries

[digi01]

I will continue the new challenge,Make a 2X100W Parallel GC.
To me , research and analyse the characteristic of a circuit, and make it ,debug it to reach supreme performance. Full of infinite enjoyment just like looking for the eggs of Easter in the software.It is all very interesting to prepare materials and search for the informations.
I liked the chassis of Peter Daniel, very very much.but I do not have a very good craft

I bought the machine case of one oem finally.this case size is 435¡Á90¡Á340(mm) there is enough space to put the device.it has six input signal switched, I get without very interested inning this.Two tooth HEAT SINK inside are bought in addition, according to the reference of National Semiconductor Application Note 1192, it is enough for P-GC.
Action now:

[digi01]

I have a great interest in testing the delicate change brought to sound with different cable,plan to test two kinds of wire for interlink signal cable.One kind is 0.6mm silver wire,one is a colored belt cable used in lift control.
gain setting resistors is more troublesome,for setting the gain of each op amp for closer matched.I have chosen the lift control circuit 1% metal resistors, in order to match, I have bought 100 in everything.And then the resistors of output like a nightmare,1%3W0.1ohm, I have to buy 8 DALE for use.so expensive

some devices that I prepared:

[digi01]

Though the circuit of p-gc is simple, but make into the real thing, there are a lot of skills, who has experience finished it,please give me some suggestions. Thanks!

[banana]

Hi digio1,

I see some single sided PCB on your table, are you going to use them for your parallel clone?

I suggest using double sided PCB with ground plane.

My 3886 PCB:

[speaker]

Originally posted by banana

My 3886 PCB:

.....is very, very nice!



speaker

[digi01]

banana,I can not read your 3886PCB picture.
But I can see your yhaoo album Your Audio-general is very beautiful very neat! I see that you have used a lot of large capacitor for this gc. I feel like knowing the view that you choose to the capacitor.
In my first 3886IGC ,that every chip has used a pair of 1000uf, can work very well.So I may use the little for this P-GC to test.Though partlist of AN1192 mentions you should use such as 10000uf big cap for each rail.
I think,p2p welded is essential,so I consider the same as my original 3886igc, do not use pcb.shorten the distance of the power loop.

[Bill Fitzpatrick]

banana:

Very nice stuff! What is the software you are using that shows the subtractive low pass filter response?

[banana]

What is the software you are using that shows the subtractive low pass filter response?

That subtractive lowpass response is simulation only. I was using Microcap7 Evaluation version.
Link to Microcap7

[Hybrid fourdoor]

I have a question about parrelleling the chips.

If you put two chips in parrellel, they see (according to Nationals Application Notes Pg #2 1st Para.) # of chips*load. So if I had 2 LM3875's and a 8ohm speaker each would see 16ohms?

Now my real question is, even though seperatly there are putting out less power, together they are putting out the same.

So 2 LM3875's on a 8 ohm speaker (16 as seen by each chip) will put out half the power of 1 chip on a 8 ohm speaker, but because theres two, it adds back up. So basically you get the same output, but less strain on the chips...or rather greater thermal capacity


Is this right or is my brain oatmeal?

[digi01]

My understanding to GC output power:

Single LM3886T
Foundation on SINGLE-ENDED AMPLIFIER Pdmax EQUATION,

Pdmax = VCCtot^2/2*3.14*3.14*RL

Example:
1. VCC = +-28V, RL = 4ohm
Pdmax = VCCtot^2/2*3.14*3.14*RL= (28V)^2/2*3.14*3.14*(4ohm) = 39.7W


parallel-two LM3886 chips
When combining two IC outputs,you can get the double output current.But VCC peak value does not change. we can get following calculation.

Pdmax =U*(2*I)= 2*VCCtot^2/2*3.14*3.14*RL=VCCtot^2/3.14*3.14*RL

Example:
1. VCC = +-28V, RL = 4ohm
Pdmax = VCCtot^2/3.14*3.14*RL=(+-28V)^2/3.14*3.14*(4ohm) = 79.5W

So 2 LM3875's on a 8 ohm speaker (16 as seen by each chip)

Just a statement easy to understand, in fact the impedance of load has not changed.the load to each IC looks like a 1/2 load.
The advantage of P-GC is its ability to divide total power dissipation between ICs,and more than two ICs can be used,and when configured the same will share the power dissipation equally.--AN1192 mentions.