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Old 19th November 2009, 07:04 PM   #1
cr0wl3y is offline cr0wl3y  United Kingdom
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Default 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
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Old 20th November 2009, 12:01 AM   #2
K.A.B is offline K.A.B  Sweden
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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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Old 20th November 2009, 01:13 AM   #3
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2 resistors...
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 20th November 2009, 01:35 AM   #4
cbdb is offline cbdb  Canada
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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).
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Old 22nd November 2009, 02:22 AM   #5
cr0wl3y is offline cr0wl3y  United Kingdom
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Quote:
Originally Posted by cbdb View Post
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!
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