I will try to keep this brief
My main listening room is my kitchen, and I am making some DMLs to hang from the ceiling paired up with a subwoofer to cover the full range. I have been cycling through some components but I was thinking about building an integrated amp with a custom enclosure.
Here is what I want:
I think I could handle the middle of the road interface build myself... my main question there is what, if anything, I would need between all those sources and the input signal to the amp. I will be honest- I know basic electric circuit stuff and can solder, but I don't know anything about electronics. I'm a mechanical engineer, not an electric one. Anyway I see some places calling for a buffer to the amp and other places selling kits that feed RCA ins right to the board. I honestly don't know what a buffer is. Is one way better than the other? Will I have to do something about different source impedances? Will any old source switch work? Etc. etc.
I also have 4 channels @ 4 ohm, and the DMLs are admittedly a bit inefficient with the DSP changes. With this setup being in the kitchen, audiophile grade SNR is out the window, so I'm looking for recommendations on cost effective amp boards. I just found this for example, but I have no idea if it's worth buying or any good. The connections seem small for 2 (?) TPA3255s. So any recommendations are welcome.
Other question I guess is if anyone could recommend someone to build this for me 😀 I would just build the case as that would be a pain to ship.
My main listening room is my kitchen, and I am making some DMLs to hang from the ceiling paired up with a subwoofer to cover the full range. I have been cycling through some components but I was thinking about building an integrated amp with a custom enclosure.
Here is what I want:
- Sources- Volumio stream (USB DAC), turntable (has built in pre-amp, NBD), occasional BT
- Connection for DSP (don't know where it's best to run for least noise)
- Volume controlled RCA outs for powered sub
- Minimal interface- potentiometer volume knob, rotary source switch
- Middle of the road interface- above + RPi touch screen for Volumio controls
- Ideal interface- above with digital volume + source select and display integration with RPi touch screen
I think I could handle the middle of the road interface build myself... my main question there is what, if anything, I would need between all those sources and the input signal to the amp. I will be honest- I know basic electric circuit stuff and can solder, but I don't know anything about electronics. I'm a mechanical engineer, not an electric one. Anyway I see some places calling for a buffer to the amp and other places selling kits that feed RCA ins right to the board. I honestly don't know what a buffer is. Is one way better than the other? Will I have to do something about different source impedances? Will any old source switch work? Etc. etc.
I also have 4 channels @ 4 ohm, and the DMLs are admittedly a bit inefficient with the DSP changes. With this setup being in the kitchen, audiophile grade SNR is out the window, so I'm looking for recommendations on cost effective amp boards. I just found this for example, but I have no idea if it's worth buying or any good. The connections seem small for 2 (?) TPA3255s. So any recommendations are welcome.
Other question I guess is if anyone could recommend someone to build this for me 😀 I would just build the case as that would be a pain to ship.
IMHO, you've way overspec'd your input source requirements which is driving most of the electrical difficulty. Any chance you can do BT and BT only? That would simplify things. "USB DAC" comes from somewhere (RPi?) and that link could be BT as well, straight into the amp.
They make amplifiers with integrated DSP, 4 channels of output - so that removes the "where do I put the DSP in the signal chain" issue. In these amps, it's in the best spot - still within the digital domain, before the audio ever gets converted to analog.
I'll guess the DMLs have two exciters per panel - hence the need for 4 channels. What does the DSP curves going to them look like? Depending on that, it may be easy to generate a sub signal from two of the speaker outs by simply using a capacitor and a couple of resistors to ground - put that with a potentiometer, and there's a variable sub analog output.
If the DMLs can be connected into just two channels, then you have two more channels to drive a sub design using two drivers or a single driver with dual VCs. As an ME, you might be interested in sub cabinet design, versus expending so much energy on all the electrical hooey. Hanging DMLs from the ceiling is an interesting ME / acoustic problem to make sound good. Best of luck with it!
They make amplifiers with integrated DSP, 4 channels of output - so that removes the "where do I put the DSP in the signal chain" issue. In these amps, it's in the best spot - still within the digital domain, before the audio ever gets converted to analog.
I'll guess the DMLs have two exciters per panel - hence the need for 4 channels. What does the DSP curves going to them look like? Depending on that, it may be easy to generate a sub signal from two of the speaker outs by simply using a capacitor and a couple of resistors to ground - put that with a potentiometer, and there's a variable sub analog output.
If the DMLs can be connected into just two channels, then you have two more channels to drive a sub design using two drivers or a single driver with dual VCs. As an ME, you might be interested in sub cabinet design, versus expending so much energy on all the electrical hooey. Hanging DMLs from the ceiling is an interesting ME / acoustic problem to make sound good. Best of luck with it!
This is where I started and finished...
So basically three different sources, line level analog (since the TT got a built in RIAA amplifier), digital stream from Volumio, could be digital (like I2S) or analog (DAC) and digital stream from BT (like I2S). I found I2S between RPi and DSP being a challenge due to master clock issues so I went the DAC route for Spotify (RPi, Shairport-sync and HiFiBerry DAC+). Lets say you add a BT board to a DSP like the one from 3e Audio you can then program the DSP to auto-switch on signal detection (or use a switch through GPIO). Switching between TT and DAC can be as easy as a DPDT switch (or with a DPDT relay).
Use the DSP as the preamp and you can use if for a lot, like EQ, volume control etc.
Why RCA? Is it a line level out? Why not balanced XLR to the sub/s? Volume control can easily be implemented in the DSP if the DSP is used as the preamp. The one from from 3e Audio even got amplified balanced outputs.
Easily implemented with the DSP via GPIO, use a one gang 10k pot, a rotary switch or up and down buttons. I guess you could use GPIO to control a source switching DPDT relay if you want.
Use the RPi and interface it with the DSP through GPIO.
Use the RPi and interface it with the DSP through GPIO.
I would use a DSP and GPIO to switch sources internally and interface a simple relay switching board (could be made on a Veroboard) through GPIO for external switching, but could also be as easy as a DPDT switch.
A buffer is very useful in audio to separate stages from each other and to provide high input impedance and low output impedance between the stages. It can be as simple as an op-amp.
2ch DML and 2ch subs OR 4ch DML and 2ch subs (or 1 ch sub)?
Why is the kitchen not worthy of audiophile grade SNR? 😉
I have found my 3e Audio boards very cost efficient and well built. But there are a lot of cost efficient options out there, just not as many well built. My 3e Audio amp boards got 12V aux power. It can be used to power a DSP and it could also power a source switching relay for example.
I would do some research, read as much as you can find about different boards...
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I have another project I'd like to do afterwards that will be BT only. I'd like to have some hard connectivity to the board, at least for the turntable. And even with my old mediocre setup I noticed a decent improvement by going from BT to the Volumio streamer.
The 4 channel need is due to having 4 DMLs- they are relatively small (2x2') and output is generally low. But they are 4 ohms which either means finding a 2ch amp that can run a 2 ohm load or just going with 4 channels. The point about keeping the DSP in the digital domain is appreciated, though kind of canceled out if I have to D-A the Volumio into the board. I would like something like that if a) I can input the Volumio to the board digitally and b) the DSP has all the bands I need (the DMLs need a lot of tuning). My sub (Dayton Audio 10er) already has a variable LPF + level control and I'm happy with it- don't really want to build another one. So for its signal a full range output is fine.
The 4 channel need is due to having 4 DMLs- they are relatively small (2x2') and output is generally low. But they are 4 ohms which either means finding a 2ch amp that can run a 2 ohm load or just going with 4 channels. The point about keeping the DSP in the digital domain is appreciated, though kind of canceled out if I have to D-A the Volumio into the board. I would like something like that if a) I can input the Volumio to the board digitally and b) the DSP has all the bands I need (the DMLs need a lot of tuning). My sub (Dayton Audio 10er) already has a variable LPF + level control and I'm happy with it- don't really want to build another one. So for its signal a full range output is fine.
Or wire two pairs in series and find a 2ch amp that can run a 8 ohm load?
With the right setup, would you actually manage to hear the extra DA conversion in the kitchen? I2S is another option but often not as easy as one may think...
From an RPi I assume, a weak I2S candidate. What other options do you consider to get a digital stream from the RPi to a power amp? A power amp board with digital inputs? A DSP with digital inputs?
How many bands do you need?
A 3ch DSP would be enough with two pairs of DML in series and one sub, right?
EmuMannen I had and lost a long reply to your initial post, but you had my assessment about 99% right so I'm probably going to go with the recommendations you made.
Some follow up comments-
Regarding the number of bands I need, honestly the more the better. I am using a DSP-408 now which is limited to 10 PEQ bands with a max range of +12dB and frankly that is not enough to get the DMLs fully set up. They can cover ~80-20kHz but they need help to cover that with a flattish response. They are super strong from maybe 1kHz-9kHz so something like a combo of a -6dB cut across that plateau with boosts at the ends and some notch filters for random dips and peaks is enough. 10 bands just barely covers it all, though I may be able to optimize that through better setup. This is my first REQ rodeo.
After reading your posts over and over I think I understand what I need to get/do. Thanks so much, that was extremely helpful!
Some follow up comments-
Regarding the number of bands I need, honestly the more the better. I am using a DSP-408 now which is limited to 10 PEQ bands with a max range of +12dB and frankly that is not enough to get the DMLs fully set up. They can cover ~80-20kHz but they need help to cover that with a flattish response. They are super strong from maybe 1kHz-9kHz so something like a combo of a -6dB cut across that plateau with boosts at the ends and some notch filters for random dips and peaks is enough. 10 bands just barely covers it all, though I may be able to optimize that through better setup. This is my first REQ rodeo.
After reading your posts over and over I think I understand what I need to get/do. Thanks so much, that was extremely helpful!
I really don't know if there is a hard limit in the ADAU1701 except for available MIPS? I am running a 2 x 7 bands PEQ for the speaker EQ and another 2 x 4 bands PEQ for the headphones. I also got a bunch of filters and functionality in the DSP and I still got some MIPS to spare. I am running it at 48kHz, you get less MIPS if you up the sample rate. You got a pretty wide range in the DSP core but a bit less out of the DACs.
There are far more powerful DSP boards out there, some with both analog and digital inputs. Just do your research. I have found the DSP from 3e Audio very convenient since it exposes a lot of useful ports making it easy to integrate the board with other gear. Some other boards tie you in a bit. Just make sure you get a board flexible enough for your intended use cases and a development tool like SigmaStudio.
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Ps. If you go the DSP route, note that some DSP boards only got max 0.9 Vrms on the output DACs. That might be a bit on the shy side depending on your power amps input sensitivity. The one from 3e Audio is around 3.0 Vrms on the differential output (about 1.5 Vrms single ended).
You might want to consider this. I bought this unit but haven't had the chance to try it out yet.... Fits almost everything you asked for I think except for the input. Looking that you are trying to power DML, I think it should be good enough...
ZOUDIO AIO4CH: 4-channel amplifier with DSP and Bluetooth
Oon
ZOUDIO AIO4CH: 4-channel amplifier with DSP and Bluetooth
Oon
Thanks for this... this could actually work for another project I want to do as well. I'll start reading reviews