The C-DSP 6x8 is well priced and can work well for home use for a 3way pair + dual subwoofers.
On noise level with DSP, one big thing to consider when using a DSP is the tweeter sensitivity. In a passive design, if you need to pad the tweeter down by 5dB, you are padding down the noise floor with it. This doesn't really happen when you drop the signal level by 5dB on a DSP, so all things equal the noise floor is now 5dB worse in the high end as a result of using a DSP. You might consider using passive tweeter attenuation even when using a DSP to improve the SNR.
So, for us novice DSP guys how do you lock in the amplifier volume across 4 or 6 outputs? looks like I need a integrated amp for 6 channels? I'm not hot on measuring and tweaking every time I set these up at another location.
You can mix and match amps however you like as long as you can sort out the gain properly for your application. If you don't want to re-tweak all the levels for a different set of amps, take your amplifiers with you to set up at a new location in this scenario. Alternatively, if you design using 6 of the same amps, the relative levels will be the same using 6 of the same different amps as well.
As a benefit, you also have the ability to tweak at every location to make some compensations for the room or whatever.
Pe was selling a ton of the t-amp knockoffs back then so one 100x4 ran the tweeters and mids, while a 300x2 ran the woofers. They sound better than most HT receivers I've heard over the years and it was cheap.
Now the minis drive a pair of acurus a200x3 manufactured during the Mondial (aragon/krell) era.
yes, so from source (or preamp) to DSP - in DSP set levels for driver attenuation or gain to match the drivers and if you are using different amps to match the outputs of the amps - you measure the actual drivers with the actual amps that will be driving them and set the gain / attenuation in DSP for each output channel.
post that you set the overall volume form the source or preamp -> DSP input -> process signal and split into multi channel -> DSP sets gains/attenuation/XO/ PEQ/FIR for each channel as well as time delay (for matching acoustic centers) -> each output channel -> each amp -> each driver.
DSP can get tricky for videos if the chip is not very powerful and you have a lot of delays built in, the video may not be in sync with the audio, for music, no issues...
For the mini there may be a volume control similar to the dsp408 so a preamp isn't needed but I've never seen or used it. Been using that tube preamp Craig and Tom helped me build. Some of the mini products, like the 4x10hd, have volume control so no pre would be needed.
If you want a great sounding 8x8 DSP unit and are willing to do a little work building the configuration & a custom GUI, look for an older BSS Soundweb box. The 3088 (the one that I have) and 9088iis are older units that you can pick up for under $100 on ebay. The programming software is a little clunky by today's standards, but it allows for tons of options - even wired switches & pots to control various things. These were big bucks in their day and used for all kinds of things, from boardrooms & ballrooms, studios, & concert rigs.
The t-amp driving the Sadie bass bins clippes at <moderate volume due to an undersized smps and the larger power supplies are more than I want to spend; enter Mr. Carver. Pulled the hood on the carver 705x and fixed it again. The first time I fixed it, it smoked,
never really found any crispy parts but replaced a couple resistors that
measured ok but didn't look right. It is now driving the Sadie+Dog
House build (is that too korny of a name?).
Next up.
In the beginning, there wasn't a hum issue with the tube 4s pre but getting the larger coupling caps to fit meant moving some things around. Hello hum. Slightly rerouted grounding and lifted a grounding point so everything is grounded at only one point of the chassis. Hum gone.
Next.
Now how do I fix this pos dayton dsp408? As it stands, the top portion is passive with the 408 doing hand-off duties for the bass bins. After some trial and error, I was finally able to retain what I like of the top portion and now, as a whole, the system has bass, but the 408 hums louder than the tube pre ever did. No difference with either power supply. Rerouting the 12v input wire and patch cords yield no improvement. Winding it through a magnet, nuttin. Both 408 units hum. It's a 12v wall wort, could I try a car battery?
The resistor isn't necessary, but the cap will reduce ripple in the same method that any increase in capacitance in a linear DC power supply will. Probably not the issue if you are using a regulated switch mode power supply to begin with like most wall warts are these days.
What you need to determine is that the hum is coming from the power supply ripple. If it's from a ground loop a quiet power supply isn't going to fix that as the ground loop will still be there. Did you try plugging it in to something other than your DIY tube amp?
I would start by making sure any unused inputs are shorted to ground. I've got an old receiver with a phono amp, it has separate inputs for MC or MM, and you have shorting plugs that go on the unused inputs. The next thing I would try is to run a wire from the input ground to the output ground to connect them together, see if the problem is better, worse, or no change doing that. Just take some scrap wire and touch against the outside of the RCA plug.
No idea if the supplied wall wart is regulated. Tried different receptacles, swapping wire routing, wrapping with magnets, etc., no dice. Have two 408s' and both hum in any system they have been placed, some worse than others but always hum. The minidsp remains quiet in the same systems.
I've seen those shorting caps before, in Stereophile. Guess they're not snakeoil after all. If I understand correctly, jumper from the outer rca input sleeve to the outer rca output sleeve of the 408?
Could I diy some shorting plugs from cheap rca plugs by soldering their lugs together?
@Kornbread said:
No idea if the supplied wall wart is regulated.
Easy way to determine if its linear or switching is by size and weight. Is it small like a phone charger, or large and weight 1/2lb? switching supplies won't hum, if anything they would make a high frequency buzz or hiss if they're poorly regulated. Linear supplies can be regulated or unregulated, it's sometimes indicated on the label.
I've seen those shorting caps before, in Stereophile. Guess they're not snakeoil after all. If I understand correctly, jumper from the outer rca input sleeve to the outer rca output sleeve of the 408?
The caps are not for the audio signal, they're for the power supply. Adding a large cap to the audio signal is just DC blocking, most everything has this cap built-in to prevent DC offset through the audio chain.
Could I diy some shorting plugs from cheap rca plugs by soldering their lugs together?
Got tired of the hum. Copied the crossover and settings from the dsp408 to a basic minidsp 2x4 and viola, no hum. Even with my ear to the driver, no hum.
When bringing a creation to a diy event, what are some general guidelines for an active/passive setup? Are they allowed?
@Kornbread said:
Got tired of the hum. Copied the crossover and settings from the dsp408 to a basic minidsp 2x4 and viola, no hum. Even with my ear to the driver, no hum.
When bringing a creation to a diy event, what are some general guidelines for an active/passive setup? Are they allowed?
I've shown my active set up at DIY Iowa and MWAF. At Iowa I was the only active system so I set up everything under the table on stage so all I needed to do was connect the speaker cables to the speakers. All the cables were labeled so hook up could be done quickly. They gave the active systems setup time at MWAF but I still hooked all the cables I could before moving the equipment to the front.
At Iowa I think I played everything from the PC running the system. At MWAF I used their front end as input. The system uses Bodzio's Ultimate Equalizer which has the ability to EQ for my listening room. I turned that off for both demos and ran the system as is without any extra setup. It's really no different from a passive system in that respect.
PE didn't allow any tweaking at MWAF. The Unlimited category is for those projects. You just run it as you have it set up at home. It'd take forever if everyone adjusted thier setup for the room.
I'd wager knowing details of the demo room would be of advantage. Don't see any reason to bring along a budget based system to compete against the good stuff.
Knowing the room...Merideth measured the door to the closet in the room and built a cardboard subwoofer door. That irked a few people but didn't seem to help him.
@Kornbread said:
I'd like to get critiqued by others to find out if I'm on the right track.
That's where DIY events like Iowa and Indy really shine. You can (if you wish) get instant feedback from other DIY'ers instead of waiting weeks to get (sometimes questionable) score cards back from 3 judges who only heard your design for a 3 minute demo. At Indy and Iowa your design plays for 10 minutes (5 min house track/5 min your track), in a very different atmosphere. JMO
Comments
InDIYana Event Website
Can I run a line out (volume adjusted) from a preamp to the DSP then power amp?
post that you set the overall volume form the source or preamp -> DSP input -> process signal and split into multi channel -> DSP sets gains/attenuation/XO/ PEQ/FIR for each channel as well as time delay (for matching acoustic centers) -> each output channel -> each amp -> each driver.
DSP can get tricky for videos if the chip is not very powerful and you have a lot of delays built in, the video may not be in sync with the audio, for music, no issues...
https://bssaudio.com/en/product_documents/sw3088-dspdf
Will this circuit work to eliminate some of the noise from the 12v dsp408 wall wart? olcircuits.com/documents/olc_powerfiltering_guide.pdf
The resistor isn't necessary, but the cap will reduce ripple in the same method that any increase in capacitance in a linear DC power supply will. Probably not the issue if you are using a regulated switch mode power supply to begin with like most wall warts are these days.
What you need to determine is that the hum is coming from the power supply ripple. If it's from a ground loop a quiet power supply isn't going to fix that as the ground loop will still be there. Did you try plugging it in to something other than your DIY tube amp?
I would start by making sure any unused inputs are shorted to ground. I've got an old receiver with a phono amp, it has separate inputs for MC or MM, and you have shorting plugs that go on the unused inputs. The next thing I would try is to run a wire from the input ground to the output ground to connect them together, see if the problem is better, worse, or no change doing that. Just take some scrap wire and touch against the outside of the RCA plug.
On the linear power supply topic, this site provides some nice visualizations of what is going on in a basic linear DC supply:
https://www.changpuak.ch/electronics/power_supply_design.php
And this site provides some more in depth information of linear DC power supplies:
https://www.circuitlib.com/index.php/lessons/91-basic-linear-power-supply-circuits-design
No idea if the supplied wall wart is regulated. Tried different receptacles, swapping wire routing, wrapping with magnets, etc., no dice. Have two 408s' and both hum in any system they have been placed, some worse than others but always hum. The minidsp remains quiet in the same systems.
I've seen those shorting caps before, in Stereophile. Guess they're not snakeoil after all. If I understand correctly, jumper from the outer rca input sleeve to the outer rca output sleeve of the 408?
Could I diy some shorting plugs from cheap rca plugs by soldering their lugs together?
Easy way to determine if its linear or switching is by size and weight. Is it small like a phone charger, or large and weight 1/2lb? switching supplies won't hum, if anything they would make a high frequency buzz or hiss if they're poorly regulated. Linear supplies can be regulated or unregulated, it's sometimes indicated on the label.
The caps are not for the audio signal, they're for the power supply. Adding a large cap to the audio signal is just DC blocking, most everything has this cap built-in to prevent DC offset through the audio chain.
Yes, absolutely.
Got tired of the hum. Copied the crossover and settings from the dsp408 to a basic minidsp 2x4 and viola, no hum. Even with my ear to the driver, no hum.
When bringing a creation to a diy event, what are some general guidelines for an active/passive setup? Are they allowed?
I've shown my active set up at DIY Iowa and MWAF. At Iowa I was the only active system so I set up everything under the table on stage so all I needed to do was connect the speaker cables to the speakers. All the cables were labeled so hook up could be done quickly. They gave the active systems setup time at MWAF but I still hooked all the cables I could before moving the equipment to the front.
Ron
I assume the house preamp was used and everything after that you supplied, including the amps? Are you allowed to listen and tweak?
At Iowa I think I played everything from the PC running the system. At MWAF I used their front end as input. The system uses Bodzio's Ultimate Equalizer which has the ability to EQ for my listening room. I turned that off for both demos and ran the system as is without any extra setup. It's really no different from a passive system in that respect.
Ron
PE didn't allow any tweaking at MWAF. The Unlimited category is for those projects. You just run it as you have it set up at home. It'd take forever if everyone adjusted thier setup for the room.
Agreed...
InDIYana Event Website
I'd wager knowing details of the demo room would be of advantage. Don't see any reason to bring along a budget based system to compete against the good stuff.
Knowing the room...Merideth measured the door to the closet in the room and built a cardboard subwoofer door. That irked a few people but didn't seem to help him.
...it's not all about competing.
I'd like to get critiqued by others to find out if I'm on the right track.
That's where DIY events like Iowa and Indy really shine. You can (if you wish) get instant feedback from other DIY'ers instead of waiting weeks to get (sometimes questionable) score cards back from 3 judges who only heard your design for a 3 minute demo. At Indy and Iowa your design plays for 10 minutes (5 min house track/5 min your track), in a very different atmosphere. JMO