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Old 28th April 2005, 06:54 AM   #1
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Default Calling behringer DCX2496 experts, new cheap implimentation

hi all i am after some peoples opinions on the way i am intergrating a behringer dcx2496 into my hifi system

firstly over at the gainclone forums i have been developing a new gainclone i dubbed the studio clone or SGC it is based on the lm1875 and features a lower gain for hi level audio inputs like the behringer and has a balanced input the scheamatic is attached below

Click the image to open in full size.

now my idea was to find a cheap simple way of intergrating the behringer into a simple hifi system with gainclones, as it was with a standard gainclone but i would of needed 4 channels of atenuation to run my 2 way bookshelfs, which as many people found can be a pain. Add to this the fact the studio clone has a balanced input i would need to attenuate 8 signals very accurately, which would prove time consuming and expensive


now heres where i need some second opinions i planned on using the 15db of digital gain on the behringer as my main volume controll, i have read and know well the bit definition loss that occurs when using the digital volume controll as an attenuator, but i wish to use the 15db of positive headroom to drive the amp but im not sure what strain this may put on the analogue stage inside or what negative effects it would have on the sound

my solution was to connect the behringer directly to the studio clone, i can do this safely as it only has a gain of 10. Now idealy with the behinger on 0db of gain connected directly to studio clone with no attenuation i get a "just below ideal listening level" on my bookshelfs

as i crank the gain up to 3-4db i get my ideal listening level

and as i crank the behringers gain from 5- 12db i get more dynamic to my loudest comfortable listening level

now to me this system is both cheap minimalist and performs extremely well. i have only built one experimental studio clone and it is being driven off the behringer not acting as a crossover but more a dac as this is still in develop ment

so the system works i dont need to worry about complicated attenuation issues the SGC is by far the best sounding and quietest gainclone i have ever built, it is absolutely pitch black but what is using the 15db of gain doing to the sound, from my understanding it is just increasing the digital loudness and giving a higher voltage at the xlr output that drives my amp

i am just concerned as the vu leverls seem to be pinned but i am not hearing any major clipping or distortion at the speaker end

your thoughts ? best regards keegan
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Old 13th February 2006, 02:54 AM   #2
Will is offline Will  Malaysia
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Is this balanced gain clone circuit a theoretical one or is it working practically ?
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Old 13th February 2006, 04:33 AM   #3
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YES, it has been working perfectly for at least 6 months now all day everyday. I am very happy with it although, i never got around to publishing photos and results here or at gainclone.com . Also found the ideal attenuation was 12db

regards keegan
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Old 13th February 2006, 04:53 AM   #4
Will is offline Will  Malaysia
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Quote:
Originally posted by mr_squeegs
YES, it has been working perfectly for at least 6 months now all day everyday. I am very happy with it although, i never got around to publishing photos and results here or at gainclone.com . Also found the ideal attenuation was 12db

regards keegan

Thanks. I also plan to build up something like this.

What about the 12dB attenuation ? Is it a balanced pot you install at the input of the amp or the DCX's gain setting ?
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Old 13th February 2006, 05:57 AM   #5
seoman is offline seoman  Netherlands
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Nice project!

About the pinned vu meter.
The DEQ has a limiter at it's outputs.
I suspect the DCX has them aswell.

Lower the gain of the DCX
(comment also based on the DEQ)

Regards Simon
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Old 14th February 2006, 11:16 PM   #6
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the only pots i use are alps and buying one for each output is costly, and adjusting them all together is madness.

i have the dcx2496 driving an lm1875 on the woofer and the tweeter

i have a tee resistor network of each output of the dcx2496 (a tee network hass 3 resistors and 2 are needed on each channel. 3 resistors on the hot, 3 on the cold, 6 in total.

i found 12 db of attenuation @50k is ideal.

you can calculate it here

tee resistor calculator

i then use the gain offset on my ultra curve as digital volume controll, which is all i ever need. 12db @ 50k is ideal but you may wanna play depending on your speakers efficiency etc

best of luck - keegan
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Old 22nd February 2006, 03:21 AM   #7
Will is offline Will  Malaysia
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Keegan,

How was your amp implemented ?


This is what I have in mind for an 8 channel amp with balanced input.

Single tx 625VA 25-0-25v
25A dual bridge rectifier
Rectified voltage to be filtered thru 100K uF of capacitors
All 8 channel balanced gainclone per your schematic (with 10uF cap)
All 8 channel powered with the 100K uF
Star Ground connected to earth thru 100ohm/0.1uf cap.
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Old 22nd February 2006, 04:00 AM   #8
ergo is offline ergo  Estonia
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You could use a 6channel ALPS pot in balanced shunt mode.....

check Borbely page for sample schematic.

This works - I have tried.

I dropped it only because I was using it right after DCX DAC's as a passive analog stage. There the signal was small already and I could not use a bigger series resistor, so I used 440ohm in front of 10k shunt pot. The problem was that 440 was too small and most of time I had to use the pot between 70-100% setting.

You could use some 2,2k resistor in both +/- line and a 10k pot as shunt. That should give a much better result.

Ergo
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Old 22nd February 2006, 04:11 AM   #9
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sorry I cant help you with the power supply, mine ran of two 24v NICAD aircraft batteries with .1 uf cap ! , nothing beats pure DC

one thing that is proven though is that your power supply will make or break the sound quality of your lm1875 amps, so put some thought into it

regards keegan
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Old 22nd February 2006, 04:11 AM   #10
Will is offline Will  Malaysia
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I forgot to mention that I actually myself a driverack dbx PA which only accepts balanced analog input, so I'll be driving it with either with a Balanced Zen linestage or just a passive balanced attenuator. My preference would be a passive one.

Actually my main question was on the 8 channel amp construction which I'm seeking opinion as to which implementation is the best for sonics. Do I go with a single large transformer to share its voltage across 8 channels or do I use dual mono construction (inside one single chasis) which might potentially induce more hum or ground loop problems etc.
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