Simple summing circuit needed for DIY audiophile grade mixer

cr0wl3y · 19th November 2009, 07:04 PM

Hi there,

I'm in the process of making a dual valve phono pre-amp to get rid of my DJ mixer and I was wondering if people could advise on what the best way to get the two signals into one output is.

I am basing this on Jan Lodström's REMUS design (3 ECC83s and 2 ECC82s). Essentially, I will be building two complete separate amps in the same chassis. Now, the idea is that the outputs from the two pre-amps is then fed into a simple, clean summing circuit - no need for individual attenuation or panning, the former will be done at the pre-amp stage and the latter I have no need or desire fot. Importantly, I want to minimise all influence to the sound from the circuit.

Can anyone suggest something?

Thanks a lot!

Nikos

K.A.B · 20th November 2009, 12:01 AM

Hello Nikos,

I wonder why you should build two pre-amps it is enough that you build one and have two relays and a switch that you can switch between the two inputs I have this in my pre-amps I have built.

Cheers
Anders

PeteMcK · 20th November 2009, 01:13 AM

2 resistors...

cbdb · 20th November 2009, 01:35 AM

Quote:

I wonder why you should build two pre-amps it is enough that you build one and have two relays and a switch that you can switch between the two inputs I have this in my pre-amps I have built.

He probably wants to cross fade between the two turntables.

The 2 resistors will work, just need to figure out the values, which depend on the input impedance of your power amp, and the output impedance of the pres (if there not low enough to neglect).

cr0wl3y · 22nd November 2009, 02:22 AM

Quote:

Originally Posted by cbdb

He probably wants to cross fade between the two turntables.

The 2 resistors will work, just need to figure out the values, which depend on the input impedance of your power amp, and the output impedance of the pres (if there not low enough to neglect).

First off, thanks everyone for the input.

cbdb is spot on, I want to be able to crossfade between the two turntables, which is why switching is not an option.

I'll do a little homework on impedance:resistor values and may check back with you for advice, till then, thanks!

19th November 2009, 07:04 PM	#1
cr0wl3y diyAudio Member Join Date: Sep 2009	Simple summing circuit needed for DIY audiophile grade mixer Hi there, I'm in the process of making a dual valve phono pre-amp to get rid of my DJ mixer and I was wondering if people could advise on what the best way to get the two signals into one output is. I am basing this on Jan Lodström's REMUS design (3 ECC83s and 2 ECC82s). Essentially, I will be building two complete separate amps in the same chassis. Now, the idea is that the outputs from the two pre-amps is then fed into a simple, clean summing circuit - no need for individual attenuation or panning, the former will be done at the pre-amp stage and the latter I have no need or desire fot. Importantly, I want to minimise all influence to the sound from the circuit. Can anyone suggest something? Thanks a lot! Nikos

20th November 2009, 01:13 AM	#3
PeteMcK diyAudio Member Join Date: Feb 2002 Location: Sydney	2 resistors... __________________ ‘today… there lives alongside the twentieth century the tenth or thirteenth. A hundred million people use electricity and still believe in the magic power of signs and exorcisms” Trotsky

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20th November 2009, 12:01 AM	#2
K.A.B diyAudio Member Join Date: Nov 2005 Location: Sweden	Hello Nikos, I wonder why you should build two pre-amps it is enough that you build one and have two relays and a switch that you can switch between the two inputs I have this in my pre-amps I have built. Cheers Anders

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