Hi Guys,
I've just finished rebuilding the four output buffers in the big green monster, using the DIP-16 boards I posted in #130 above. I've only put two in for the present, since until the rest of the crossover/bi-amping project is done I only have two outputs. They got hot, but don't appear to get unreasonably hot. This should solve concerns juma had about long tracks and exposed gates, although there isn't any easily audible improvement in the sound. (Not on a quick listen, anyway.) More importantly, perhaps, I managed to get a much "cleaner" p2p layout on the back, and managed also to put everything in a smaller area on the board, which will be important later and which was for me the main issue. (I only save about 1/2 in, though...)
In case anyone would like to try this out, I've attached a .pdf file,which is the mirror-image of the copper on the board - ready to print out and iron onto the copper. I'm sure many or most of you could improve on it, though, if you had a mind to...
As always, all comments are welcome.
Meanwhile, this leaves me with the old boards, which I ought to do something with. I was thinking of making a couple of stereo preamps to give to friends, but it's only really practical if I can do it cheaply and (relatively) easily. So, since the largest expense seems to be the mosfets in the PSU, I'm wondering if the IRFP044 could be substituted by something cheaper without too much loss in performance. I read somwhere IRF610 is consdiered somewhat noisy, but how about IRF620, 540 and so forth. Opinions?
Cheers
Nigel
I've just finished rebuilding the four output buffers in the big green monster, using the DIP-16 boards I posted in #130 above. I've only put two in for the present, since until the rest of the crossover/bi-amping project is done I only have two outputs. They got hot, but don't appear to get unreasonably hot. This should solve concerns juma had about long tracks and exposed gates, although there isn't any easily audible improvement in the sound. (Not on a quick listen, anyway.) More importantly, perhaps, I managed to get a much "cleaner" p2p layout on the back, and managed also to put everything in a smaller area on the board, which will be important later and which was for me the main issue. (I only save about 1/2 in, though...)
In case anyone would like to try this out, I've attached a .pdf file,which is the mirror-image of the copper on the board - ready to print out and iron onto the copper. I'm sure many or most of you could improve on it, though, if you had a mind to...
As always, all comments are welcome.
Meanwhile, this leaves me with the old boards, which I ought to do something with. I was thinking of making a couple of stereo preamps to give to friends, but it's only really practical if I can do it cheaply and (relatively) easily. So, since the largest expense seems to be the mosfets in the PSU, I'm wondering if the IRFP044 could be substituted by something cheaper without too much loss in performance. I read somwhere IRF610 is consdiered somewhat noisy, but how about IRF620, 540 and so forth. Opinions?
Cheers
Nigel
Attachments
Hi gaborbela,
If you're inquiring about complete pcbs then perhaps you might want to take a look here:
http://www.diyaudio.com/forums/group-buys/158425-gb-bf862-based-preamp.html
Cheers
Nigel
Hi, gaborbela,
Well, looking at the board it *looks* to me like it is for a stereo preamp with one power supply powering both channels, but I didn't study it very closely, and I think you should ask the question there to be sure.
Cheers
Nigel
Hi gaborbela,
I understand your concern.... If you don't want to post the question on the GB thread, then why not send a PM to the organiser (who name is "npapp" on the forum) and ask him directly?
(Although they certainly look like stereo boards to me...)
Cheers
Nigel
Hi juma,
Our posts crossed... Funnily enough, I was thinking earlier (in another context) that no-one reads the whole thread anymore. I'm probably guilty myself sometimes...
What did you think of my new DIP-16 boards? Better than the previous version?
Cheers
Nigel
Volume pots...
Hi Guys,
I mentioned above that I now have several surplus boards soldered up, enough to make three extra stereo preamps, which I am thinking of putting into boxes for non-diy friends. The catch is that I don't want to spend a fortune on these, so I spent a couple of hours going through the stockroom at the Elec. Eng. dept. again, to see what I could dig up to help keep cost down. (I've mentioned elsewhere that I can sometimes get NOS/used/surplus stuff there... It's like Aladdin's cave...) So I lucked out and got two really nice 10-turn 31k wirewould pots ("Clarostat" is the brand name on them, which google indicates is now part of honeywell). These will do really nicely for the one I'm planning on keeping for my office system, but I was less fortunate with the others. In fact, most of the pots look worn out, or aren't sealed and are just too dirty to consider. I did find a really nice pair of miniature sealed pots, which have a really smoootthhh action (maybe conductive plastic?) but they are only 5k. This sounds a little low to me, what do you guys think? The idea is to put them before the preamp circuit just as Nelson has them before the bufer in the standard B1 article. I presume their value only makes a difference by defining the input impedance, right?
I'm probably gong to do the PSUs for these "giveaway" amps with IRF9610/610 9620/620 or 9630/630, since these are widely avaiable and cheap here. Anyone have any suggestions or preference? Or strong reasons to stay with IRFP044?
Cheers
Nigel
Hi Guys,
I mentioned above that I now have several surplus boards soldered up, enough to make three extra stereo preamps, which I am thinking of putting into boxes for non-diy friends. The catch is that I don't want to spend a fortune on these, so I spent a couple of hours going through the stockroom at the Elec. Eng. dept. again, to see what I could dig up to help keep cost down. (I've mentioned elsewhere that I can sometimes get NOS/used/surplus stuff there... It's like Aladdin's cave...) So I lucked out and got two really nice 10-turn 31k wirewould pots ("Clarostat" is the brand name on them, which google indicates is now part of honeywell). These will do really nicely for the one I'm planning on keeping for my office system, but I was less fortunate with the others. In fact, most of the pots look worn out, or aren't sealed and are just too dirty to consider. I did find a really nice pair of miniature sealed pots, which have a really smoootthhh action (maybe conductive plastic?) but they are only 5k. This sounds a little low to me, what do you guys think? The idea is to put them before the preamp circuit just as Nelson has them before the bufer in the standard B1 article. I presume their value only makes a difference by defining the input impedance, right?
I'm probably gong to do the PSUs for these "giveaway" amps with IRF9610/610 9620/620 or 9630/630, since these are widely avaiable and cheap here. Anyone have any suggestions or preference? Or strong reasons to stay with IRFP044?
Cheers
Nigel
Maybe this thread will be of interest: http://www.diyaudio.com/forums/pass-labs/156094-b1-active-crossover.html . It's not exactly what you asked for, but I'm using it to do stereo subs, which is close to your query...
Cheers
Nigel
feed each of the outputs through it's own resistor to an inverting opamp. This will sum the signals. Then filter to send to the bass.
Hi Everyone,
I mentioned above I was thinking of doing more of these - here's one I just finished for my office system...
Sorry massimo, I just couldn't help myself...
The preamp uses two of the boards I showed above, a 24 - 0 - 24 Vac trafo (with 7924 and 7915 regulator preregulating the negative voltage), and except for using a pair of LEDs instead of the 3v9 zener in the negative PSU is juma's schematic posted above. The box is 1.5mm steel box from something the Elec. Eng. dept. was throwing out; the transformer and preregulatoers and smoothing caps are under a screen/shield, also 1.5mm steel, although in this case cut out of an old (VEEERRRYY old...) computer PSU chassis. I went out of my way to keep costs down on this one - 10-turn 31k pots for left and right volume, output caps, brass standoffs, steel boxes and several other bits and pieces came from the Elec.Eng. junkboxes (many thanks to Cicero and the guys there...) I'm pretty happy with how it turned out. I still have to put a plexiglass window on the front, wire up the second input, and put a (red!!) LED on the front to show power.
The sixth photo show it with the BF862-mini-Aleph-J its powering...
Did I mention it sounds great?
As always, (constructive) criticism is very welcome.
Cheers
Nigel
I mentioned above I was thinking of doing more of these - here's one I just finished for my office system...
Absolutely famous all over the world and that will be the colour of my next Aston Martin!
But pls leave red to Italians and our Ferrari!....
Sorry massimo, I just couldn't help myself...
The preamp uses two of the boards I showed above, a 24 - 0 - 24 Vac trafo (with 7924 and 7915 regulator preregulating the negative voltage), and except for using a pair of LEDs instead of the 3v9 zener in the negative PSU is juma's schematic posted above. The box is 1.5mm steel box from something the Elec. Eng. dept. was throwing out; the transformer and preregulatoers and smoothing caps are under a screen/shield, also 1.5mm steel, although in this case cut out of an old (VEEERRRYY old...) computer PSU chassis. I went out of my way to keep costs down on this one - 10-turn 31k pots for left and right volume, output caps, brass standoffs, steel boxes and several other bits and pieces came from the Elec.Eng. junkboxes (many thanks to Cicero and the guys there...) I'm pretty happy with how it turned out. I still have to put a plexiglass window on the front, wire up the second input, and put a (red!!) LED on the front to show power.
The sixth photo show it with the BF862-mini-Aleph-J its powering...
Did I mention it sounds great?
As always, (constructive) criticism is very welcome.
Cheers
Nigel
Attachments
