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
 
http://www.taelektroakustik.de/eng/ta2/r_system/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. I´m 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?
 
Gabster said:

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
 
Hi Gabster! Do you have a design for your relais - restor array based volume control? could you post it please?

I don´t 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.)
 
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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Re: Aleph P volume contr.

nar said:
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.
 
Going back to the original question...

the physical noise is kind of funny to me and my family since it is a fast
kind of mutted tiny bell 'klinging' (kind of 'struggling' wet sea/river pebbles.
in your hand).

My kid (2 years old) loves to make Daddy box go into 'little noise' without
regarding of the ill effects to the speakers (going too loud, no mechanical
induced noise)

Also, I believe that without using a microprocessor it is better to use the
six most significant bits from the ADC in order to avoid the 'vibration' of
the less significant bits (and having it simple)...

-MKT-
 
I meant noise occuring on output line,not the mechanical noise.
According to Nelson it is due to different time rise up/down for the relays.
I reduced noise by applying DC voltage 120% of the nominal tension on the relay coil.

Anyone has an idea like RC time alignement to completely get rid of this problem?:confused:
 
Back to the relais stuff: which relais should be used? there are differences in min load, contact materials Ag/Au/Pd/Pt materials etc. possibly 5V types for direkt drive from the IC or with smaller drivers than TIP29.

I investigated the relais TA uses, TAKAMISAWA RY24W-K .. a type i find no information about and are not able to buy.

Omron, not exactly to see the type, looks like G6A series.

Any suggestion which type is fine?
 
Relays!

In my aleph P-L variant I am using the TAKAMISAWA RY12W-K simply necause these happened to be easily available locally and very cheap too(1,5euro/pc). Afterwards I found out that www.schuro.de stock these but alot more expensive though reasonably priced, they also got the pdf specifications about these.
If u are lucky enough u may order these from Scuro ;-).

I provide the relays with 12v driven by a BC550 with a 4K7 resistor between the base and ADC0804 and works perfectly.
I have to admit I love the cliking sound these produce when changing the volume. My pcb solution is located on

http://www.diyaudio.com/forums/attachment.php?postid=22925

Regards,

Panos:cool:
 

Nelson Pass

The one and only
Paid Member
2001-03-29 12:38 am
The relays are shunt-to-ground devices, and the
lowest noise is achieved in make-before-break
arrangements, so we engage one or more relays
before breaking others. Experimentation will get you
the lowest transient, and a little programming will
do anything you want.

Myself, I don't mind a little "zipper" noise on my volume control.
When I was young, I recall that zipper noise was one of the
goals of having a good sound system.

Hmmm... Now that I think about it, it still is. :)
 
i built the volume control with adc0804 like at the link gabster posted below, and i´ve no problem with the little noise at some of the volume-change points. only i would like more range at the silent end. lowest position is a little loud at night, i think about an addintional switch for less volume. (bypass preamp or so)