I have been using it for a while and i like it. just for fun i changed The op amps to LM4562 and i actually noticed the noise level did go down as well as what i perceived to be a sound quality improvement over the other op amps i was using.
It is being used between EMU 0404 on quiet computer and GC with full range speakers or Event self powered near field studio monitors (20/20p) and also powers headphones (hd25) directly sometimes
now i can hear a radio station in one of the channels when i turn it up full. now i never hear it at normal listening level but it bothers me that it is there i would like that channel to be as quiet as the other one.
any idea how to fix it? i have no idea if the radio is being picked up by the new op amps or it was there before and i just couldn't hear it because of the noise that was masking it.
It is being used between EMU 0404 on quiet computer and GC with full range speakers or Event self powered near field studio monitors (20/20p) and also powers headphones (hd25) directly sometimes
now i can hear a radio station in one of the channels when i turn it up full. now i never hear it at normal listening level but it bothers me that it is there i would like that channel to be as quiet as the other one.
any idea how to fix it? i have no idea if the radio is being picked up by the new op amps or it was there before and i just couldn't hear it because of the noise that was masking it.
I suspect it's a shielding issue. What kind of case is the Kook mounted in?
I have a radio tower on a hill near my house (about .3 miles, line of site). I typically use aluminum cases with earth ground tied to the case, but completely seperated from my PSU and audio grounds. Seems to solve any interference issues.
I have a radio tower on a hill near my house (about .3 miles, line of site). I typically use aluminum cases with earth ground tied to the case, but completely seperated from my PSU and audio grounds. Seems to solve any interference issues.
neutron7 said:
Hello,
If you are still picking up RF junk you could form a simple low pass filter at the input. Just add something like a 1-3.3K (depends on how low you want to filter) resistor followed by a 240pf capacitor to Signal GND.
You could do this right at the input jack.
Cheers!
Russ
Yes i have swapped the inputs, and the radio still comes from the same input.
the case is an aluminium box which used to be a hard drive enclosure/cooler it has earth ground from mains connected to the box.
it is not great priority because i never listen loud enough to hear it but i will try the input filter next.
thanks for help everyone.
the case is an aluminium box which used to be a hard drive enclosure/cooler it has earth ground from mains connected to the box.
it is not great priority because i never listen loud enough to hear it but i will try the input filter next.
thanks for help everyone.
Has anyone experimented with soft recovery rectifier diodes for the Kookaburra?
I put RC accross the stock rectifier diodes (Epcos polyprop. 47nf+47R first - that's all I had ; then 47nF +1R) and sound improved a lot, IMHO
Less agressive, softer sounding highs, warmer midrange, better textures.
47R is maybe too high: sound a bit "slow".
At first I thought that being "digital", power supply would be less critical, but it surelly responds to better caps and better rectifiers, IME.
I will have to make the time and place to experiment with better V regulators. Shunts anyone?
Appart that, no output buffer for me, thanks...
Cheers,
M
I put RC accross the stock rectifier diodes (Epcos polyprop. 47nf+47R first - that's all I had ; then 47nF +1R) and sound improved a lot, IMHO
Less agressive, softer sounding highs, warmer midrange, better textures.
47R is maybe too high: sound a bit "slow".
At first I thought that being "digital", power supply would be less critical, but it surelly responds to better caps and better rectifiers, IME.
I will have to make the time and place to experiment with better V regulators. Shunts anyone?
Appart that, no output buffer for me, thanks...
Cheers,
M
kookaburra board as 5.1 preamp
around post 115, people were discussing daisy-chaining a few of these boards to use as a HT preamp. From this discussion and the data sheet, the code needs to be rewritten to keep the CS input
" low for 16 x N SCLK periods, where N is the
number of devices connected in the chain, in order to allow
enough SCLK cycles to load all devices."
First of all, is this an issue with the current set up?
Second, although I understand this in theory, I would not be able to change the code or reprogram the chips. Is there a hardware solution?
Third, If not, can someone program a chip for me to manage 3 boards?
Nice job on all of your stuff guys. If I only had deeper pockets. . .
around post 115, people were discussing daisy-chaining a few of these boards to use as a HT preamp. From this discussion and the data sheet, the code needs to be rewritten to keep the CS input
" low for 16 x N SCLK periods, where N is the
number of devices connected in the chain, in order to allow
enough SCLK cycles to load all devices."
First of all, is this an issue with the current set up?
Second, although I understand this in theory, I would not be able to change the code or reprogram the chips. Is there a hardware solution?
Third, If not, can someone program a chip for me to manage 3 boards?
Nice job on all of your stuff guys. If I only had deeper pockets. . .
Banned
Joined 2002
Member
Joined 2003
Modifications
Just thought I'd put in here some of the modifications I have done to the basic Kookaburra kit. I don't have the most recent PCB revision (might even be the first PCB rev) so some of this may not apply to new Kookaburra boards. The first thing I did was jumper a wire from pin3 to pin1 on the PGA2311 because the PIC used for this project cannot set pin3 high on it's own. This enables the zero-crossing detector and is supposed to reduce the switching noise when changing the volume, although I can't say that I could notice any difference at all.
The next thing I did was replace the 1n4004 diodes with MUR140 fast recovery diodes. I did this the same time I changed the rectifier on my Mauro My_Ref amp to MUR820 diodes. I also don't have the latest rev of PCB for the My_Ref, so I didn't have nice proper pads to solder the MUR820's to the My_Ref, so it was a bit of work, but fairly easy as the diodes are a big part and easy to solder.
The hard soldering came with replacing the OPA2227 with LM4562. I had to remove the 100nF caps on the power supply rails next to the op-amps, and even then it was fairly difficult replacing the SOICs because I had to hold the iron vertical as to not melt anything.
Next on the agenda is the regulators. I plan to replace the 7812/7912 regulators with LM317/337 optimized for low noise. I will construct the regulator on veroboard, and solder the veroboard in place of the 7812/7912. If all goes will it should end up being only slightly chunkier than the current regulators. I'll replace the 12V zeners on the My_Ref with these as well if they turn out okay. Here's what I have for low noise regulator design. I think it's about as good as you can ask for with the LM317/337 regulators:
Just thought I'd put in here some of the modifications I have done to the basic Kookaburra kit. I don't have the most recent PCB revision (might even be the first PCB rev) so some of this may not apply to new Kookaburra boards. The first thing I did was jumper a wire from pin3 to pin1 on the PGA2311 because the PIC used for this project cannot set pin3 high on it's own. This enables the zero-crossing detector and is supposed to reduce the switching noise when changing the volume, although I can't say that I could notice any difference at all.
The next thing I did was replace the 1n4004 diodes with MUR140 fast recovery diodes. I did this the same time I changed the rectifier on my Mauro My_Ref amp to MUR820 diodes. I also don't have the latest rev of PCB for the My_Ref, so I didn't have nice proper pads to solder the MUR820's to the My_Ref, so it was a bit of work, but fairly easy as the diodes are a big part and easy to solder.
The hard soldering came with replacing the OPA2227 with LM4562. I had to remove the 100nF caps on the power supply rails next to the op-amps, and even then it was fairly difficult replacing the SOICs because I had to hold the iron vertical as to not melt anything.
Next on the agenda is the regulators. I plan to replace the 7812/7912 regulators with LM317/337 optimized for low noise. I will construct the regulator on veroboard, and solder the veroboard in place of the 7812/7912. If all goes will it should end up being only slightly chunkier than the current regulators. I'll replace the 12V zeners on the My_Ref with these as well if they turn out okay. Here's what I have for low noise regulator design. I think it's about as good as you can ask for with the LM317/337 regulators:
An externally hosted image should be here but it was not working when we last tested it.
Banned
Joined 2002
DcibeL: Good lucj with the regulators. Let us know how it turns out.
Jason: Do you want to use these for balanced or SE inputs? You could use a pair for balanced stereo, and link the PIC outputs from one board to both boards. They do work well as a preamp. Can even use the LM4563 instead of OPA2227 since the current demands for a pre are much lower than for a head amp. BTW, they have on-board PSUs.
Jason: Do you want to use these for balanced or SE inputs? You could use a pair for balanced stereo, and link the PIC outputs from one board to both boards. They do work well as a preamp. Can even use the LM4563 instead of OPA2227 since the current demands for a pre are much lower than for a head amp. BTW, they have on-board PSUs.
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