Relay Attenuator, another Allo game changer


Allo has done it again: when you believe your system already sounds good enough, and you can sit back and enjoy the music quietly you see that Volumio has implemented a plugin for Relay Attenuator. So you buy this new device because in a message from this forum Allo said that I needed one.

The first thing you need to know is that if you use the Volumio volume control, you are missing things because only 100% of volume you will have all the bits (sure the experts will be able to explain this better than me), but even if you use a preamplifier, Relay does the different things with the volume.

The testing team:
-Raspberry Pi 3 powered with linear power supply, Allo isolator with LiFePO4 batteries, Allo Boss, Relay Attenuator
-Professional speakers Neumann Kh120A and subwoofer kh805. My 18 meter room has some acoustic treatments and it sounds great. This equipment is designed to mastering, I can perceive the smallest changes.

You have to burn relay a few hours, at least 50 hours, I know what you’re thinking, but without burning relay slows down the music very fast.

What I’ve noticed on the Relay to love it:

  1. The sound of the Boss with Isolator I thought it was very analogue, but now scale, not one, but many steps to make a sound that I can not imagine more analogue, not even with a turntable, unless you spend many (many) thousands of euros.
  2. The focus on the sound scene is much better, there is more separation between instruments, although the scene is not wider, compared to no Relay everything is more together and confusing. The air sounds, it’s hard to explain, if you close your eyes there’s space around each instrument
  3. There is more detail, and I do not speak of absurd details like a breath or fingers stroking the strings, I talk about reverb, and you hear that sound in the right channel and see how now they move to the left channel to disappear (decay, I do not know if it says so and n English)
  4. There is more and better bass, very good bass. This can be a bad point if you don’t like Boss’s bassr or think you are short of sharp. Also note that I have a great subwoofer capable of great things.
  5. The Boss is very musical, the sound is very nice, as Relay multiplies this, the voices are sweet, wonderful. You can only enjoy similar with tubes.

With piano 2.1 and Relay you will have very good things, and although piano scene 2.1 is better and is more detailed, it does not have the sweetness and magic of the Boss with Relay.

And all this for a ridiculous price. I tell you what Allo said: You need a Attenuator Relay.

Remember that it is only my experience and that I do not work for Allo or have any economic interest. My only interest is that you enjoy the music as I do.

Congratulations Allo! You’ve done it again.

Best regards.

Wow!! Beam down the attenuator Scotty[emoji3]

Joking aside first: do you seed an isolator first? Second: wll in fit top or under the Boss?

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From the looks you can tell that it must be connected to the Boss and another pair of rca to the amp. Right?

And does it support Picore as well as Volumio?

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Hi Captain Kirk :wink: hahahaha.

You put first Rpi3, then Isolator (with much better lifepo4), after Boss and then Relay. You connect the rca to your power amplifier or amplifier to the two connectors on the right side of relay (the other two are input of another input device, but it is not as good as if you used Boss).

Right now you only can control relay with volumio without adding more hardware. If you want to use other software that add buttons, or hifiduino or IR receiver in rpi and remote controller, and install and configure more software on their Rpi. You can find the Guide on this page of Allo.

Best regards


I’m new here and like so many other trying to make up my mind abouth how my first raspberry Pi and volumino based streamer+amp setup should look like. Actually It will go to my dad but I will give it a thorough try first :wink: .

As I have learned that the volume control is one of the more critical components in the audio chain, I’ve thought about a setup with Pi3+BOSS+Relay feeding a DIY power amp without volume control. Do you more experienced guys have any comments on a setup like that?

My concern is the relay as the only volume control. I’m worried it’s too easy to accidentally turn the volume too much up… How convenient is it to control the relay board via the Volumino plugin? Does it remember the volume setting from last session when powering up? Is it possible to set a max volume on the relay to elimiate any finger slips leading to blown eardrums…?

Br. Zleepy


I use it with self-powered speakers, which is the same as using it with a power stage. It’s very good for that.

You can limit the volume in the Volumio options.

The volumio plug-in volume control for me is correct, if you want more precision you will have to use hardware components.

The volume is zero when you power on, if you use volumio plug-in.

Best regards.

Thanks Jazz, very helpful info!

Br, Zleepy

Jazz can I ask; is it possible to have it on top of Boss, and at the same time have a second source connected to the input connectors, and if I need to hear this second source I just pause in Volumio and start the source? Also, am I wrong that the resistor principle ought to result in a higher output impedance (possibly much higher)? My power amp has a 6000ohm input impedance, so from the rule of thumb I should definetly not exceed 600ohm output impedance from the source.

Well, there must be some big holes in my understanding, as the attenuator apparently will use from 0ohm - 10kOhm. So I will exceed the rule of thumb by an order of magnitude. I guess that can’t be right… :frowning:

Hi Knudsen,

Yes, it is possible that you have a second source connected, I have not had good experience with that. I do not like the sound. Regarding the other issue, I think like you, and in this case can make the bottleneck attenuator, but I do not have enough knowledge of electronica to ensure it 100%.

Best regards

Not a good idea to have both sources connected in the same time. Always use only one analog input

Regarding your AMP, the best it to ask the manufacturer what value of pot they recommend . Its actualy a bit complicated.

The AMP will see the DAC + POT in parallel . so that usually 100Ohm (dac) + 2500KOhm(1/4 of max 10k from pot) = about 99Ohm

Your DAC will see the AMP + Pot in parallel = 5.9K

I was wondering when using the Allo Attenuator with the Piano 2.1 in subwoofer 2.1 mode, will it attenuate the subwoofer level as well?

It only attenuates the LR channels…the attenuation for sub is done in software

So, when using a Push-button switch on the attenuator both the volume of the Sub and LR are operated by the attenuator at the same time (sub by software, LR by the relays)?

Thanks a lot Jazz and allo. I am surprised the impedances should be calculated as in parallel, though I have no doubt you are correct. Is this specific to the attenuator, or would replacing that with a standalone potentiometer still mean parallel?

For my concrete setup I’ve ordered a cheap jfet zero-gain buffer, just to see if I have impedance issues


I don’t know where to post this question as it’s about a suitable case but since I’m planning on using the attenuator, I’m asking here:

Is there a suitable case for RPI3 + kali + piano2.1orBOSS +relay attenuator?
What if I throw in an isolator :slight_smile: …where would it go (between RPI and kali or between kali and DAC?) and is there any cases to fit all these modules…?

Also, when piano2.1 is used in dual mode, the relay attenuator controls these LR outputs right? I was wondering if the other DAC chip outputs to the sub channels (?) then maybe the attenuator does not control the other channel?

Br, Karl

Hi Karl

The isolator would be placed between Rapsberry and Kali (or Boss). I have not noticed improvement with that with piano 2.1, very nice with Boss.

It is not possible to dual mono and relay attenuator directly. You could connect dual mono outputs to relay attenuator inputs, but it has not been good either. I do not use relay attenuator for piano 2.1 nor isolator. You do not have better sound with those elements. But that’s just my experience and with my team. Unfortunately the synergies between components (amplification and loudspeakers) also play here, and what may not work for me may work for you. You will only know if you try.

Best regards

Hi Jazz,

Thanks for the info! I am a bit dissapointed to learn that relay attenuator does not work with piano2.1 in dual mono.

I was planning on feeding a power amp directly from the attenuator, it is the exact same power amp as users knudsen and Yatsushiro on this forum, a ICEPower 50ASX2.

I wanted to keep software volume control at 100% and let relay attenuator do the attenuation via its high quality resistors. I have to think again how to do this. There’s also the aspect that I’m afraid that using only software volume attenuation it’s very easy to blow either your eardrums or the speakers with the slip of a finger…

Do you like Boss or piano2.1 better? I read a review somewhere that piano2.1 in dual mono has better soundstage and imaging than BOSS.

How do you mean by isolator going between RPI and Kali (OR BOSS)? Is kali unnecessary if using BOSS as dac?

Br, Karl


The Boss is a master dac, does his own reclocker, does not need another reclocker as is Kali. Piano 2.1 is dac slave, needs a clock, either kali or evil the Rapsberry clock.

Boss or piano 2.1 (with kali): both. Boss is magic, pleasant sound that you can hear hours without tiring your brain or your ears. The price you pay is that you are missing high frequency details. Piano 2.1 dual mono is more detail, more balance, there will be magic in the voices like with Boss. When my friends want one of these two teams almost always like more Boss but in the end they want for their system Allo kali, piano 2.1 dual mono and very very important, linear feeding. It is more balanced and more for all kinds of music. You know you’re not losing anything. I prefer to have both and sometimes one and the other :slight_smile:


Installed it today. Using volumio and its dedicated plugin.

But why am I not hearing any difference whether its on or off??

Can anyone here point me to some instructions on how to attach a volume knob to the Attenuator?

Is it as simple as just purchasing a knob and connecting it to the pins on the board, or does it need some advanced knowledge?