Looks interesting. I would probably skip one relay, 32 attenuation steps is probably enough, IMO. My laptop gets away with only 17 steps and it feels enough. My own R-2R attenuator has 64 steps but I am now thinking to reduce it to 32. You may also wish to reduce the onboard capacitor bank. It may create significant inrush current for RPI at start. I use a single 100uF capacitor next to the relay controller and with 7 relays total (6 for attenuation + mute) I do not have problems. Which relays do you plan to use? The least current hungry ones are not the smallest as far as I know. The small Omron G6K series would require ~20mA per relay when engaged so in your configuration it will result in ~120 mA max current (when all relays are ON). I could not quickly find the specs for RPI power capability through its pins but I would check if 120 mA is not stressing the RPI too much. Also what is the reason for a second I2C expander?
Regards,
Oleg
Regards,
Oleg
Hi ,
yes we plan on using the Omron Gk6 relays , the RPI can easily source 1A
Why do you use mute relay...there is enough attenuation with resistors..
yes we plan on using the Omron Gk6 relays , the RPI can easily source 1A
Why do you use mute relay...there is enough attenuation with resistors..
Good question. Some people swear that they need the mute function. I thought I'd rather have it and not need it, than need it and not have it
I can always remove the relay and short the pads. But there is an advantage when you need to turn the sound off for a moment and resume with the same level afterwards. There the mute relay comes handy. In my system mute is the default standby state. In your case it is probably easier to engage the mute on the digital side, so no mute relay is needed.I'm looking at getting an RPI 3 + Allo Boss combo. This will be my first foray into SBC/DAC land and I'm unsure of how best to control volume if I'm going directly from the DAC analog out to a Carver solid state power amp.
From my limited reading I have a few options:
1) Software volume control - Boss analog out directly to the power amp with the application (volumio, Moode, etc.) controlling the volume.
2) Allo stepped attenuator - Boss analog out -> stepped attenuator -> power amp. Would this even work or is this attenuator just for the Allo Volt/Volt+ amp?
3) Allo LDR attenuator - Not sure I understand this concept of volume control. The way I read this, I would need a second RPI with the LDR to control the volume. So is this how the chain would look:
RPI(1) with Boss -> RPI(2) with LDR -> Power Amp.
Couple of additional questions:
Are there any other options for volume control that I'm missing?
And are any of these preferred over the others if sound quality is the primary factor?
Thanks in advance.
Sorry I missed your post.
The best way to control volume depends on your setup. If you are using your own AMP , I would recommend either relay attenuator ( we should have it before end of the month on sale) or LDR . However LDR is much more expensive and needs its own SBC. Both relay attenuator and LDR will give you an excellent volume (hardware) controller.
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How can I make this work as a standalone solution with Volumio (i.e., without an ALLO DAC shield)?
Volumio is supported with the use of a plug-in developed by Allo. Take a look here: Amazon Drive
I have a Hifiberry DAC+ Pro. It does have the holes to add a pass through pin header. But I am not sure if the necessary pins are available after the Hifiberry (will have to look it up in the Hifiberry docs). Also, the relay attenuator does not have the "full" pin header, so it's a bit unclear where to put it. Which pins are used by the attenuator?