Accuphase MCS

Havenwood · 14th February 2010, 10:06 PM

Hi, I don´t understed how MCS (Multipli Circuit Summing-up) improve the S/N ratio or THD.
Accuphase Laboratory, Inc.?MCS

We get at the input v(t)+noise(t), 3 linears amps with gain A1, A2 and A3, then ouput is: (A1+A2+A3)*v(t) + (A1+A2+A3)*noise(t)

Or noise is not corralated and I can´t sum A1*noise(t)+A2*noise(t)+A3*noise(t)?

How improved the distorsion?

ilimzn · 15th February 2010, 01:11 AM

You have a number of errors in your reasoning that come from not understanding some basic circuit rules.

Amplification factors do NOT sum unless amplifiers 1, 2, 3 are in series - NOT in parallel.
For the signals to simply add as is shown in this circuit, amplification factors of 1, 2, 3 MUST be the same, i.e. A1=A2=A3=A. The total amplification factor of such amps in parallel remains the same as that of a single amp, A.
A*noise(t) as well as distortion(t) are not correlated so they have to add as random vectors. Assuming noise(t) is of equal amplitude but not correlated between amplifiers 1, 2, 3, the total noise is noise(t)/(square root of 3), as is total THD.In reality, noise does behave as uncorrelated, distortion less so, so the drop in distortion is usually less than the theoretical 1/(square root of number of identical amps in parralel).

Bonsai · 15th February 2010, 08:59 AM

Good summary ilimzn.

Havenwood · 15th February 2010, 11:45 AM

Yep, very clear ilimzn, thanks.

Accuphase

Quote:

The crucial point here is that circuits as a whole and not simply active components (such as transistors or FETs) are connected in parallel.

Why use 2 input stage and not 2 transistor/FET in parallel?
What´s the crucial point?

15th February 2010, 08:59 AM	#3
Bonsai diyAudio Member Join Date: Aug 2006 Location: Taipei, Taiwan	Good summary ilimzn. __________________ bonsai http://www.hifisonix.com/

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15th February 2010, 01:11 AM	#2
ilimzn diyAudio Member Join Date: Feb 2005 Location: Zagreb	You have a number of errors in your reasoning that come from not understanding some basic circuit rules. Amplification factors do NOT sum unless amplifiers 1, 2, 3 are in series - NOT in parallel. For the signals to simply add as is shown in this circuit, amplification factors of 1, 2, 3 MUST be the same, i.e. A1=A2=A3=A. The total amplification factor of such amps in parallel remains the same as that of a single amp, A. A*noise(t) as well as distortion(t) are not correlated so they have to add as random vectors. Assuming noise(t) is of equal amplitude but not correlated between amplifiers 1, 2, 3, the total noise is noise(t)/(square root of 3), as is total THD.In reality, noise does behave as uncorrelated, distortion less so, so the drop in distortion is usually less than the theoretical 1/(square root of number of identical amps in parralel).

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