A twisted tale about a logarithmic relay attenuator

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#461
that IR-D15A Is very flexible

because It offers 14 digital outputs represented by remote butons It would handle source switching
does anybody tried that
I would like to know how I can couple ICs outs to source relays
Do I need extra logic elements
 
#463
hey guys,

I am noticing a pretty loud pop at around the 64th step. I have no idea if I'm counting correctly, but if the pot starts at 6:00 the loud pop is at 11:00-11:30. This is very loud comparatively and happens in both channels. Is this a case where you're going from 01111 to 10000 or something like that in the encoder? Also, is it normal for the 0 volume position to leak some sound?

All-in-all I'm extremely happy with both of my JT, but just curious about these two things...

Thanks!
 
#464
luvdunhill said:
hey guys,

I am noticing a pretty loud pop at around the 64th step. I have no idea if I'm counting correctly, but if the pot starts at 6:00 the loud pop is at 11:00-11:30. This is very loud comparatively and happens in both channels. Is this a case where you're going from 01111 to 10000 or something like that in the encoder? Also, is it normal for the 0 volume position to leak some sound?

All-in-all I'm extremely happy with both of my JT, but just curious about these two things...

Thanks!
Click to expand...

Hello, almost every source has at least a tiny bit of DC. What you are hearing is a quick change in impedance as quite a few relays switch at that step. This presents itself as a small pop. 🙂 The only way to avoid it, is to eliminate the DC, which means a series cap. Personally I try to avoid input caps, so I don't mind it.

Cheers!
Russ
 
#469
#470
Russ White said:


Hello, almost every source has at least a tiny bit of DC. What you are hearing is a quick change in impedance as quite a few relays switch at that step. This presents itself as a small pop. 🙂 The only way to avoid it, is to eliminate the DC, which means a series cap. Personally I try to avoid input caps, so I don't mind it.

Cheers!
Russ
Click to expand...

Russ:

I've looked a bit more into this. If the zero point is at 6:00, I get the pop at 11:00. Also, it seems that I get a faint hum. This hum continues until around 1:00 and then I get another pop and the hum disappears from that point to "max" volume. I've tried this with sources that are DC coupled as well as contain coupling caps. Any ideas what this could be?
 
#472
BrianDonegan said:
I think you want two chips. One of the IR-D15A for volume, and one IRX10A for relay drive.

http://www.rentron.com/IRX10A.htm

Should be pretty simple.

[EDIT] Schematic of their board shows how they drive relays from the IRX chip:
http://www.rentron.com/Files/IRX-10ASCH.pdf
Click to expand...


Hi Brian

If I want to control only relays and not motor can I use Ir-d15A outputs and relay driver, like Is showed here

http://www.diyaudio.com/forums/showthread.php?postid=316000#post316000
 
#476
Yes please! I was already planning on writing an IR controller and source selector for the JT (or perhaps replacing the JT controller). This would save me a whole lotta work.

How many output pins are left of the JT controller after IR and LCD are added?

Kind Regards,
Jonathon

Russ White said:
If anyone is interested I can publish the firmware I wrote to use an IR decoder and an LCD (or PLED) with the JT.

Its actually pretty simple to modify our original JT controller to do IR remote control.

You can see the display here, but almost any 2 x 20 LCD would work as well.

http://www.diyaudio.com/forums/showthread.php?postid=1227199#post1227199

Cheers!
Russ
Click to expand...
 
#477
DC offset?

Hi Russ and Brian,

I have just ordered a Joshua tree. I'm going to put it in a Starfish preamp (see Pink Fish forum) where there are coupling caps before and after the pot. I'm sure the JT will be great here.

However I have just made a preamp using the AD815 using CarlosFM's circuit. I am not using any caps here so there's DC offset to the pot. Will the Joshua tree be OK if I try it in this preamp?

cheers

Aidan
 
#478
Re: DC offset?

chalkandtalk said:
Hi Russ and Brian,

I have just ordered a Joshua tree. I'm going to put it in a Starfish preamp (see Pink Fish forum) where there are coupling caps before and after the pot. I'm sure the JT will be great here.

However I have just made a preamp using the AD815 using CarlosFM's circuit. I am not using any caps here so there's DC offset to the pot. Will the Joshua tree be OK if I try it in this preamp?

cheers

Aidan
Click to expand...


It will work fine, but you will get noticeable clicks on volume changes because of the DC.

Cheers!
Russ
 
#479
Thanks Russ. When I use it with the AD815 I'll use a cap between it and the JT. Those clicks sound unpleasant.

Another question.

In my Starfish preamp I am using a 50K Alps pot. Will the impedance of the JT be a difficult load for the preamp, as it's a Naim circuit? Is the impedance of the JT about 2K? Will I need to use different value resistors?

cheers

Aidan
 
#480
chalkandtalk said:
Thanks Russ. When I use it with the AD815 I'll use a cap between it and the JT. Those clicks sound unpleasant.

Another question.

In my Starfish preamp I am using a 50K Alps pot. Will the impedance of the JT be a difficult load for the preamp, as it's a Naim circuit? Is the impedance of the JT about 2K? Will I need to use different value resistors?

cheers

Aidan
Click to expand...


Is the 50K pot before or after the preamp?

I am not familiar with that pre.

If the pot is before the preamp, then you should be just fine so long as your source can handle the minimum impedance of about 2.5K(ish).

Cheers!
Russ
 
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