I have just built my first amplifier , and I am very very happy with it! Here are some pictures, just for interest:
There is still one more part to finish, that being volume attenuation. I need a way to adjust all 6 channels at the same time to the same degree. One option is a 6 gang 10k log pot, but they are expensive. I have found this device: http://www.st.com/stonline/products/literature/ds/9227.pdf, but I have no idea about digital electronics, so I dont know how to implement it. I am very willing to learn about the digital ways, so prehaps someone could point me in the right direction as to how I would gain the required knowledge to use such a chip. If anyone has any implementation ideas on how to get that 6 channel volume control chip working with a simple 5xLM3886 based amp I would be very grateful.
My amp design was based around this: http://dogbreath.de/Chipamps/ThreeResAmp/ThreeResAmp.html
Thanks for your help!
Dan 😀
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
There is still one more part to finish, that being volume attenuation. I need a way to adjust all 6 channels at the same time to the same degree. One option is a 6 gang 10k log pot, but they are expensive. I have found this device: http://www.st.com/stonline/products/literature/ds/9227.pdf, but I have no idea about digital electronics, so I dont know how to implement it. I am very willing to learn about the digital ways, so prehaps someone could point me in the right direction as to how I would gain the required knowledge to use such a chip. If anyone has any implementation ideas on how to get that 6 channel volume control chip working with a simple 5xLM3886 based amp I would be very grateful.
My amp design was based around this: http://dogbreath.de/Chipamps/ThreeResAmp/ThreeResAmp.html
Thanks for your help!
Dan 😀
Member
Joined 2009
Paid Member
Nice looking amp. I'm curious, can you describe what you have on the back panel ?
The stm link isn't working ?
The stm link isn't working ?
apologies, i added a comma at the end of that datasheet link. here it is fixed. http://www.st.com/stonline/products/literature/ds/9227.pdf
on the back panel you can see 3 LED's, and 2 voltage regulators. one at 5v and 1 at 12v. these are connected up to a molex plug, and is used to power the LED's and the fan on top! Easy to plug/unplug when you take the top off the amp. heres a closer look:
on the back panel you can see 3 LED's, and 2 voltage regulators. one at 5v and 1 at 12v. these are connected up to a molex plug, and is used to power the LED's and the fan on top! Easy to plug/unplug when you take the top off the amp. heres a closer look:
An externally hosted image should be here but it was not working when we last tested it.
Nice bugsplat design! 
I did one for a friend with 15 amps, 7 transformers, 40,000uF of capacitance, and an active crossover in a slightly bigger case. Much cleaner than my effort.
Look in the Solid State forum for the "Lightspeed attenuator" thread. It's a pretty straightforward design that can easily be expanded from two to six channels. It only requires a single pot of no particular quality, a power supply (you can probably use the 5 or 12v you already have there), and 6 or 12 LDRs (light dependant resistors). And it sounds better than most any pot, IMHO. Also, you could look at the article on diyparadise.com "All about volume controls" for the basics of a LDR attenuator.
The LDRs will be the most difficult part to source. I thought I saw a group buy a while ago, but I'm not sure if it went through. The hardest part is matching the LDRs.
Edit: it looks like someone has already done a 6 channel volume control with LDRs:
http://www.diyaudio.com/forums/showthread.php?postid=1545782#post1545782
I did one for a friend with 15 amps, 7 transformers, 40,000uF of capacitance, and an active crossover in a slightly bigger case. Much cleaner than my effort.Look in the Solid State forum for the "Lightspeed attenuator" thread. It's a pretty straightforward design that can easily be expanded from two to six channels. It only requires a single pot of no particular quality, a power supply (you can probably use the 5 or 12v you already have there), and 6 or 12 LDRs (light dependant resistors). And it sounds better than most any pot, IMHO. Also, you could look at the article on diyparadise.com "All about volume controls" for the basics of a LDR attenuator.
The LDRs will be the most difficult part to source. I thought I saw a group buy a while ago, but I'm not sure if it went through. The hardest part is matching the LDRs.
Edit: it looks like someone has already done a 6 channel volume control with LDRs:
http://www.diyaudio.com/forums/showthread.php?postid=1545782#post1545782
Member
Joined 2009
Paid Member
The TDA7448 looks like a nice chip, but the distortion spec. aren't that great if you want the best possible quality. You'll need a pcb and a means to set the volume via the serial bus. It doesn't seem like a simple approach - unless I'm misunderstanding something.
The Lightspeed is currently the favoured approach for maximum sound quality. But do you need this - it's always tempting to follow the excitement of others on the forum in picking the ultimate solution. The Lightspeed requires you to match non-linear resistors that suffer from a lot of manufacturing variations. For 6 channels it might be expensive as you'll have to buy a larger batch to get matching units. Having said that, I'm going in this direction myself.
There are multiganged potentiometers. Even though they aren't cheap the price probably compares favourably with these other solutions. I believe for sound quality you need to choose a good ganged pot. There are some known brand names. I was looking at the Vishay linear ganged pots as an economical choice but with reasonable quality. To make up several channels you may have to buy several dual ganged pots and disassemble and reassemble them - but it looks trivial to do this. http://www.vishay.com/docs/51047/p9.pdf
You mention a fan. I know at my work the fan from the LCD projectors cause a lot of EMI noise on our conference phones if placed nearby. I don't know what kind of fan you are using, or if you have noticed any EMI on the sound output of your amp ?
The Lightspeed is currently the favoured approach for maximum sound quality. But do you need this - it's always tempting to follow the excitement of others on the forum in picking the ultimate solution. The Lightspeed requires you to match non-linear resistors that suffer from a lot of manufacturing variations. For 6 channels it might be expensive as you'll have to buy a larger batch to get matching units. Having said that, I'm going in this direction myself.
There are multiganged potentiometers. Even though they aren't cheap the price probably compares favourably with these other solutions. I believe for sound quality you need to choose a good ganged pot. There are some known brand names. I was looking at the Vishay linear ganged pots as an economical choice but with reasonable quality. To make up several channels you may have to buy several dual ganged pots and disassemble and reassemble them - but it looks trivial to do this. http://www.vishay.com/docs/51047/p9.pdf
You mention a fan. I know at my work the fan from the LCD projectors cause a lot of EMI noise on our conference phones if placed nearby. I don't know what kind of fan you are using, or if you have noticed any EMI on the sound output of your amp ?
thankyou very much fenris! that is a really good solution. you my friend have just saved my *** about 100 quid lol. ill read up on all of that info and give an update on what the plans are =]
dannybeckett said:
My Lightspeed Attenuator LDR one will send you nutz trying to make all 6 channels track.
There is this one not as good sounding, also not cheap, but you need something that all 6 channels will track equally.
http://www.goldpt.com/dims.html
Cheers George
I have the same "need" but haven't yet gone througn the options.
Is there any reason why we cannot simply use this:
source => single preamp/pot => active xo => amp
and why you need 6x attenuator like this:
source => active xo => 6x pots => amp
The 1st method is used in linkwitz orion etc. so they can't be that bad (??)
Is there any reason why we cannot simply use this:
source => single preamp/pot => active xo => amp
and why you need 6x attenuator like this:
source => active xo => 6x pots => amp
The 1st method is used in linkwitz orion etc. so they can't be that bad (??)
If you use something like DCX2496, there'd be a 'problematic' addtional A/D converter in front of each channel 🙁
If all analog, it's of course no problem to have the control in front of xover.
If all analog, it's of course no problem to have the control in front of xover.
Some of those here have not used a DCX before, I agree with CLS that using a DCX requires a 6 channels pot, I am using one.
A simple explanation is this, the digital output from CD or any digital source goes into the DCX which takes this digital signal and filters it into low, medium and high freq. signals in accordance to x-over specified by the user. The signal o/ps are analog ie 6 channels(left and right). The x-over is done digitally inside the DCX.
DCX a useful tool for speaker development before designing active analog/passive x-over.
A simple explanation is this, the digital output from CD or any digital source goes into the DCX which takes this digital signal and filters it into low, medium and high freq. signals in accordance to x-over specified by the user. The signal o/ps are analog ie 6 channels(left and right). The x-over is done digitally inside the DCX.
DCX a useful tool for speaker development before designing active analog/passive x-over.
Looking at the OPs amp and reading the original post, he's not running stereo guys. He's running a 5.1 surround system that requires 6 volume controls, not a stereo split into three frequency ranges. I'd worry about "slop" between channels of any 6 ganged pot or attenuator.
For a LDR type controller, I'd worry more about getting two good matching pair for the front L-R, two more good pair for the rears, and the center/sub need only be close and not exact. The close matching is to keep the image properly aligned left to right. Rear channels are less used and therefore matching them to the front probably isn't as critical. Center and sub are independent - it would be nice to have them track closely, but it's not as critical.
For a LDR type controller, I'd worry more about getting two good matching pair for the front L-R, two more good pair for the rears, and the center/sub need only be close and not exact. The close matching is to keep the image properly aligned left to right. Rear channels are less used and therefore matching them to the front probably isn't as critical. Center and sub are independent - it would be nice to have them track closely, but it's not as critical.
You might wanna try the Maxim/Dallas . If you're interested, i've got a small pcb done in Eagle for one of these, as per Pedja Rogic's schematic.
i haven't noticed any emi due to the fan, the output is great (apart from the 1V dc offset when its plugged into my computer due to no input cap!)
It seems like lightspeed is the way to go, but matching the outputs is the most difficult part. what about purchasing a load of low ohmic trimmer pots, and trimming each ldr to the correct output?
It seems like lightspeed is the way to go, but matching the outputs is the most difficult part. what about purchasing a load of low ohmic trimmer pots, and trimming each ldr to the correct output?
What software opens the "lay" files?
Could you add a description of the operation?
What is IC2_10
Could you add a description of the operation?
What is IC2_10
What is this?
is there something missing off the end?
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