If you are using active filtering and separate amps for the speakers the high pass is , obviously , set by the active filter preceeding the amp for the tweeter , and so is the response curve in frequency. If you then place a capacitor in series with that speaker it must be large enough to be a short circuit for the ac going to the speaker at least two octaves down because the tweeter doent just stop working and reproducing at , in your case , 3000 Hzit is down by 6 , 12 or 24 dB at 1500 Hzdepending on your filter response and it is down by 12, 24, or 48 dB at 750 Hz . assuming you have a filter with slope of 12 dB the 750 Hz is what you have to aim for , lower is better , if you do not want the capacitor to have any influence in the audible frequencies reproduced by said tweeter. If you use a Linkwitz-Riley with 24 dB then aim for 1500 Hz.or lower. then , for an 8 ohm tweeter the capacitor should be 22uF or larger , and with a 12 dB filter 47 uF or larger. Do not use electrolytics . I use WIMA film capacitors , from Mouser for example , and 100V rating , this is the wrong place to save money
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A few pics of my shelter for the homeless ChipAmps. Missing electronic parts will arrive tomorrow. Rolled & sanded with 1200 wet. Final Toroid will be bigger.
P.S. Maybe I'll replace/upgrade the tweeters. At the moment I've got Monacor DTM-104/8, but they already look a little shabby, and there is always the thought of replacing them. The seating is 104mm in diameter, a pair should cost 100€ max., crossover should be around 2500Hz or maybe a little lower.
The linked tweeters seem interesting to me. What would you suggest?
www.soundimports.eu/de/scan-speak-r2604-832000.html
Seas 27TDFC Hochtoner bestellen - SoundImports
Scan-Speak D2604/833000 Hochtoner bestellen - SoundImports
SB Acoustics SB29RDC-C000-4 Hochtoner bestellen - SoundImports
P.S. Maybe I'll replace/upgrade the tweeters. At the moment I've got Monacor DTM-104/8, but they already look a little shabby, and there is always the thought of replacing them. The seating is 104mm in diameter, a pair should cost 100€ max., crossover should be around 2500Hz or maybe a little lower.
The linked tweeters seem interesting to me. What would you suggest?
www.soundimports.eu/de/scan-speak-r2604-832000.html
Seas 27TDFC Hochtoner bestellen - SoundImports
Scan-Speak D2604/833000 Hochtoner bestellen - SoundImports
SB Acoustics SB29RDC-C000-4 Hochtoner bestellen - SoundImports
Attachments
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... you will be in heaven
There is an easy way to shorten the connection of the feedback resistor to the absolute minimum possible without much fumbling to get it done.
Luckily both pins 3 and 9 of the chip are in the "forward row" of pins of the chip which are bent forward and then down again. This creates a "groove into wich the resistor fits both in length and width.
So what I am doing is put the chip face down on a flat surface , then a little bit of clear contact glue along one side of the resistor which I then lay into the groove so that the glue touches the lower edge of the chip and intermediate pins , centering the body of the resistor between pins 3 and 9.
Leave to dry for some hours.
When the glue is dry and the resistor can´t move its very easy to bend its leads so they lie on the downsloping flat surface of pins 3 and 9 and cut them to about 2-3 mm . Now you can solder them to the two pins , or do that once the chip is soldered to the PCB . I do it once the chip is in place to minimize possible mechanical strain, and to remove heat from soldering the resistor faster to the PCB.
Doing it this way allows me to place it 100% straight , centered , the glue is invisble once dried , stays a bit flexible , and it gives me the shortest possible connections.
I hope you find it useful.
The resistor there is almost invisible too unless one has a very close up look so it is a neat way to get this done.
Luckily both pins 3 and 9 of the chip are in the "forward row" of pins of the chip which are bent forward and then down again. This creates a "groove into wich the resistor fits both in length and width.
So what I am doing is put the chip face down on a flat surface , then a little bit of clear contact glue along one side of the resistor which I then lay into the groove so that the glue touches the lower edge of the chip and intermediate pins , centering the body of the resistor between pins 3 and 9.
Leave to dry for some hours.
When the glue is dry and the resistor can´t move its very easy to bend its leads so they lie on the downsloping flat surface of pins 3 and 9 and cut them to about 2-3 mm . Now you can solder them to the two pins , or do that once the chip is soldered to the PCB . I do it once the chip is in place to minimize possible mechanical strain, and to remove heat from soldering the resistor faster to the PCB.
Doing it this way allows me to place it 100% straight , centered , the glue is invisble once dried , stays a bit flexible , and it gives me the shortest possible connections.
I hope you find it useful.
The resistor there is almost invisible too unless one has a very close up look so it is a neat way to get this done.
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Just to let you know that I, by accident, did some stability & endurance tests.
One stereo amp takes care of mid+treble in my active setup.
Crossover between the fullrange and tweeter is passive.
In a moment of "creativity" I wanted to bypass the filter for the fullrange (2nd order LC) and thought I can simply short the "L" temporarily for a sound-check.
That left the amp looking at an Alpair 7.3 in parallel with a 5.6µF film-cap.
The transformer hum was a little more obvious but no apparent changes otherwise.
I ended up leaving that setup for ~3weeks and forgot about the "mods".
After the very conservatively dimensioned fuse sometimes blew the 2nd time on turn-on it slowly dawned on me and I realized what I did...
Other than that the sound was totally fine so PCB+LM3886 were still doing their job!
Just so you know that the PCB is working just fine and the LM3886 is one rugged chip!
One stereo amp takes care of mid+treble in my active setup.
Crossover between the fullrange and tweeter is passive.
In a moment of "creativity" I wanted to bypass the filter for the fullrange (2nd order LC) and thought I can simply short the "L" temporarily for a sound-check.
That left the amp looking at an Alpair 7.3 in parallel with a 5.6µF film-cap.
The transformer hum was a little more obvious but no apparent changes otherwise.
I ended up leaving that setup for ~3weeks and forgot about the "mods".
After the very conservatively dimensioned fuse sometimes blew the 2nd time on turn-on it slowly dawned on me and I realized what I did...
Other than that the sound was totally fine so PCB+LM3886 were still doing their job!
Just so you know that the PCB is working just fine and the LM3886 is one rugged chip!
Hey People,
I've got happy News, I am the proud Mother of Sixlings! Ok, the Parts are not from the Mouser BOM, and some are soldered underneath the PCB, but they are alive and making Noise. First time I've got 6-Channel Stereo with all LM3886 left & right (+ 2x TDA7293 for the Sub). The second Box is far from finished, so I took it's Predecessor (the Mk I ) which is more or less the same Box just not as pretty as the Mk II. It's still work to do on the first Mk II, but I couldn't wait and had to hear it. I like what I hear. I really like it.
The Pics are small because of limited Bandwidth.
I've got happy News, I am the proud Mother of Sixlings! Ok, the Parts are not from the Mouser BOM, and some are soldered underneath the PCB, but they are alive and making Noise. First time I've got 6-Channel Stereo with all LM3886 left & right (+ 2x TDA7293 for the Sub). The second Box is far from finished, so I took it's Predecessor (the Mk I
) which is more or less the same Box just not as pretty as the Mk II. It's still work to do on the first Mk II, but I couldn't wait and had to hear it. I like what I hear. I really like it.The Pics are small because of limited Bandwidth.
Attachments
Hey people,
first, hearing music (right now Rainbow "Stargazer" ) with the open source LM3886's is really a joy! Many thanks @ all who helped !
But as I'm just a mechanic & an audio electronics newbie there is a little problem and I'd like to ask for advice.
It seems, sometimes the right box receives, or better, gets disturbed by my old cellphone. What should I do? Maybe the signal cables (microphone cable) are to long (5m)? I could shorten it by 2m.
Now for the better things. I've got a 2.1 constellation and the amp (2x TDA7293 parallel), the transformer and the caps of the Subwoofer were just standing on the floor. Now these parts have got a new home. I took two cases of old 2-way speakers and made a litte tower for the woofer. In the left case is the amp, transformator and caps are in the right one. Looks even a little like modern art .
first, hearing music (right now Rainbow "Stargazer"
) with the open source LM3886's is really a joy! Many thanks @ all who helped !But as I'm just a mechanic & an audio electronics newbie there is a little problem and I'd like to ask for advice.
It seems, sometimes the right box receives, or better, gets disturbed by my old cellphone. What should I do? Maybe the signal cables (microphone cable) are to long (5m)? I could shorten it by 2m.
Now for the better things. I've got a 2.1 constellation and the amp (2x TDA7293 parallel), the transformer and the caps of the Subwoofer were just standing on the floor. Now these parts have got a new home
. I took two cases of old 2-way speakers and made a litte tower for the woofer. In the left case is the amp, transformator and caps are in the right one. Looks even a little like modern art .Attachments
You may be getting radio infererence with your amplifier.
You can buy ferrite beads and clamp them on both ends of the audio cable that enters your amplifier. This would reduce the cable acting as an antenna to pick up the signal radiated by the mobile phone. Try to buy beads that match the diameter of the cable.
You can buy ferrite beads and clamp them on both ends of the audio cable that enters your amplifier. This would reduce the cable acting as an antenna to pick up the signal radiated by the mobile phone. Try to buy beads that match the diameter of the cable.