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Old 20th April 2002, 11:05 PM   #1
Gabster is offline Gabster  Canada
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Default Aleph P's unblanced inputs and volume

Hi,

I was looking at the schematics of the Aleph P and I was wondering where are the unbalanced (RCA) inputs? I can only see XLR inputs. Reviews I've read over the net on the P were mentioning such inputs.

The other thing I found curious is the usage of relays for volume attenuation. The concept is cristal clear to me, but I was wondering what kind of noise the mecanical contacts are doing while increasing/decreasing volume.

regards,
Gabriel
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Old 20th April 2002, 11:49 PM   #2
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http://www.taelektroakustik.de/eng/t.../pa_1220_r.htm

they do volume control with metalfilm resistor network and relais. belive, there are no mechanical sound in the signal line. maybe they put a large restistor parallel to the relais switch. I think about building such volume control one for my preamp i want to build too. Im not shure at the moment if build it with a ttl grave of 74xxx or with an atmel microcontroller. Another thing is, its easy to control it with Up and down Keys, but how to manage doing it with a poti? ADC before the atmel?
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Old 21st April 2002, 12:12 AM   #3
Gabster is offline Gabster  Canada
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I was talking about sound emerging directly from the relays as they switch.

For my part, I was thinking about using a Microchip PIC microcontroller. If you want to use an ADC, many PIC's have some built-in. However, I believe a rotary encoder would be better suited, especially is you want to have a remote!
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Old 23rd April 2002, 01:14 AM   #4
Gabster is offline Gabster  Canada
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Default Re: Aleph P's unblanced inputs and volume

Quote:
Originally posted by Gabster

I was looking at the schematics of the Aleph P and I was wondering where are the unbalanced (RCA) inputs? I can only see XLR inputs. Reviews I've read over the net on the P were mentioning such inputs.

The other thing I found curious is the usage of relays for volume attenuation. The concept is cristal clear to me, but I was wondering what kind of noise the mecanical contacts are doing while increasing/decreasing volume.
Should I ask the master himself?

ciao,
Gabriel
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Old 23rd April 2002, 01:39 AM   #5
jam is offline jam  United States
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Gabriel,

The unbalanced input is tied to the + input of the XLR (pin2). When using the unbalanced input, the - input (pin 3) is shorted to ground (pin 1) with a piece of wire.

Jam
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Old 23rd April 2002, 01:46 AM   #6
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Hi Gabster! Do you have a design for your relais - restor array based volume control? could you post it please?

I dont want to use some remotes, motorpoti or some modern and not absolute necessary and functional stuff.

I think i want only one poti or two keys.

As simple as possible... (thinking on build one more of this lifgh bulb amps, because it is a really aesthetically design.)
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Old 23rd April 2002, 02:00 AM   #7
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lots of possibilities discussed here:

Relays in input and volyme switch...

Jake
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Old 23rd April 2002, 02:29 AM   #8
Gabster is offline Gabster  Canada
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Jam, thanks for the explanation.

till, Look at the Aleph P 1.0 service manual. The schematic is very explicit and shows how to use the good old ADC0804 for that application.

ciao,
Gabriel
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Old 23rd April 2002, 02:02 PM   #9
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Default Aleph P volume contr.

I have used for my ZLS the same volume control than the Aleph P,but I run it into 8 bits instead of 6.I have experienced instability of the position of virtual wiper.I solved it using a 1K pot to feed the ADC,with a 4013 mounted on the last bit output.So,if there is instability,this bit changes constantly from 0 to 1,then the 4013 sends back 1/2*bit (1/2 of 5V/256) to the bottom of pot.

With this little trick the maximum instability latence is 3 oscilations,after what the pot is always stable.

This is intended to the one who would like to use the ADC.

Otherwise use a microcontroller.....

I asked this guy how he eliminated switch noises in the relays
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Old 23rd April 2002, 02:05 PM   #10
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Default Re: Aleph P volume contr.

Quote:
Originally posted by nar
I have used for my ZLS the same volume control than the Aleph P,but I run it into 8 bits instead of 6.I have experienced instability of the position of virtual wiper.I solved it using a 1K pot to feed the ADC,with a 4013 mounted on the last bit output.So,if there is instability,this bit changes constantly from 0 to 1,then the 4013 sends back 1/2*bit (1/2 of 5V/256) to the bottom of pot.

With this little trick the maximum instability latence is 3 oscilations,after what the pot is always stable.

This is intended to the one who would like to use the ADC.

Otherwise use a microcontroller.....

I asked this guy how he eliminated switch noises in the relays
He told me.........
"We programmed the microcontroler for minimum swiching noise."....
I haven't tried the microcontroller version,because I'm an **** in programming.
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