Very interested in the new Amp+. Several rooms in my home are pre-wired with 8ohm "in-ceiling" speakers. A RPi B+ with Amp+ and Adafruit touch screen (the GPIOs don't clash!) will all fit in a double-gang wall box and could be an interesting home audio solution.
I have 2 questions...
1) The Amp+ has 6 connectors. 4 are obviously for the speakers, are the other two optional power inputs instead of using the barrel plug?
2) The 25W output of the Amp+ I assume is into 4ohm speakers? It that the total output or per channel? What is the per channel output when connected to 8ohm speakers?
Kind Regards
Date
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20 comments
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HiFiBerry team Hi Ian,
the 25W is per channel. However you can't get 25W sine wave on both outputs in parallel. This is not an issue in the real world as you won't play sine waves ;-) Just think of it as a 2x25W amplifier to get an idea about the output volume.
With 8 Ohm speakers the power per channels is about 17W.
You're right that the 3rd connector is for the power supply.
Note that the Amp does not have a stacking header and for thermal reasons you should not mount another board on top of it. Connecting another board to the amp will need soldering on the board. You can do this, but there is no warranty for boards that have been modified (even if you only solder cables onto it).
Best regards
Daniel -
Simon Fischer Hello HiFiBerry team,
could you please give a short summary of recommendations for the power supply of the Amp+. Still 12V/3A or 18V/4A? What are the indications for 12V vs. 18V? And what size is the inside diameter of the barrel plug 2.1mm or 2.5mm (outside diameter 5.5mm)? Inner pin still + and outer pin still –?
Best regards
Simon -
HiFiBerry team Hi Simon,
the recommendation is still 12V/3A or 18V/4V. The voltage depends on the power you need. If you don't need much power, 12V will be enough, otherwise go for 18V.
Inner pin is still "-", diameter is 2.1mm. However you can also connect the power to a screw terminal. Have a look at the following diagram:
Best regards
Daniel -
hifi Actually Adafruit 3.5 TFT LCD has a conflict with DAC+ which I faced recently:
https://forums.adafruit.com/viewtopic.php?f=47&p=329067
Resolved by cutting off pin GPIO18 from LCD.
Probably AMP+ uses GPIO18 as well. -
Ian McAlpine Many thanks for the heads up hifi. I actually have the original Adafruit 2.8" TFT touch screen display and this only uses GPIO 24 & 25. However it has four optional hard switches on GPIO 18, 21, 22 and 23 that I was hoping to make use of.
I thought I read somewhere that AMP(+) only used I2S and that GPIOs (typically found on the original 26-pin header) were left unused? Your experience would suggest otherwise... but at least you had an easy workaround.
I don't want to go off topic, but I'd be interested to know what software you are using and what are you displaying on your TFT.
Thanks -
hifi I have 2.8 as well but I destroyed its touchscreen when I connected cable to it in a wrong way.
Even though LCD doesn't use some GPIO pins it can affect your devices connected to them. For
example both LCDs 2.8 and 3.5 block IR sensor connected to any spare GPIO pin:
https://forums.adafruit.com/viewtopic.php?f=47&t=64007
I suspect there is the bug in LCD driver.
I'm making Wi-Fi Internet Radio right now. For hardware I use RPi B+, DAC+, Adafruit Amplifier and
3.5" TFT LCD, Sony 4 Ohm speakers, couple rotary encoders (volume & tuning) and IR sensor for remote
control. Software based on 'mpd'. For mpd client I use Pygame for GUI, python-mpd to talk to mpd,
pylirc for IR remote. I'm writing my own client/GUI which will display station logo, name, navigation
and so on. The software is almost done. The usual problem with hardware is case/enclosure :) -
HiFiBerry team Interesting projects. Note that there is no second line of header pins on the Amp (space is too limited), wich means soldering cables is not so easy.
GPIO 18-21 are reserved exclusively for the sound interface:
http://www.hifiberry.com/guides/gpio-usage-of-the-hifiberry-products/
Best regards
Daniel -
hifi That was the main reason to use DAC+ as it has place to solder GPIO connector
to which you can connect additional devices (TFT LCD in my case). Otherwise
Amp+ would be much better choice. -
DCLXVI About the pin 18 issue, all piTFT's, that make use/or can make use of GPIO18, have two little solder pads on the back with a trace in the middle, marked "#18", you can cut/solder to disconnect/connect it to the GPIO. if you disconnect it you can even solder a jumper wire from one of the solder pads to another GPIO pin, so you can still control the backlight (on/off). -
Marcsek András I have Quadral Rubin/QuintasT200 speakers. (3-way, bass-reflex 4-8Ohm stand)
Unfortunately I couldn't find any sensitive data about this speakers.
Somebody has any experience or any knowledge, that 2x25W is it enough the speakers?.
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GAbriel Can anyone confirm whether the HifiBerry can drive ceiling speakers properly? 25W seems very low, I was looking at some 8ohm speakers which are 35-140W...Klipsch R-1650-C??? any help appreciated.
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HiFiBerry team Unfortunately I can't say what sensitivity these speakers have. Klipsch just says "good sensitivity". Therefore I think, it should be >80db/W which would result in at least 94dB at 25W power. For most people this will be enough.
Best regards,
Daniel -
Marcsek András I told directly with Quadral and it was sad that my Quintas T200 speakers sensitivy is 89db.
So if I write well the previous post, this value seems to work with Amp+ well
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GAbriel Thanks Daniel. I got this from their datasheet:
frequency response 57Hz-20kHz +/- 3dB
power handling 35 watts (140 watts peak)
sensitivity 91dB @ 2.83V/1meter
nominal impedance 8 ohms compatible
drive components Two-way system using one 1” (2.5cm) polymer dome, tweeter and one 6.5” (16.5cm) poly woofer
dimensions 9.5” (24.1cm)
cutout dimensions 8.3” (21cm)
installation kit IK-650-C (sold separately)
weight 5.1 lbs (2.3 kg)
accessories ME-650-C fire-rated enclosure (sold separately)
built from 2006
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GAbriel This one says Recommended Amplifier POwer : 80W, so I think that's what makes me wonder how 25W is going to be doing the speakers justice? But I don't really understand how wattage/impedance/voltage all works...
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HiFiBerry team Hi Gabriel,
The power rating of a speaker only tells you how much power the speaker can accept before it gets damaged. In most environment you will never use the maximum power. Your speaker with 92dB sensitivity rating will be already very loud even at 1W power.
You won't have any issues that they are not loud enough if you use them in a normal living room.Best regards
Daniel -
David Archer Hello HiFiPerry,
I have similar questions/clarifications to those above but really don't want to blow my first Amp+ setup. So...
- if I connected 1 x 8ohm impedience speakers to each of the two outgoing connectors, will my Amp+ be ok, i.e., not blow, overheat or other?
- the total output to the two 8ohm speakers would be 50w, via 25w sent to each of them, correct?
Don't mean to be silly or repetitive, just want to make sure I won't fry something.
Thanks very much.
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HiFiBerry team Yes, connecting a single 8 Ohm speaker to each output will work fine.
With 8 Ohm speakers, music power will be around 18W with an 18V power supply.
Best regards,
Daniel -
Jörg Putzgruber Hello
Ist it possible to set the outputs in series to get one 50W output?
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HiFiBerry team It is not possible to bridge the channels.
Best regards,
Daniel
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