like this?
Can this idea be taken to parallel more transformers?
An externally hosted image should be here but it was not working when we last tested it.
Can this idea be taken to parallel more transformers?
There are NO advantages to that layout. Will not get any more power than a single transformer.
I would suggest either doubling the voltage by grounding the "inside legs" (-24 & +24) of the transformers or doubling the current delivery by seperating the center tap and then paralleling the secondaries.
I showed pictures of how to do it to a toroid elsewhere in this forum.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=42705
I would suggest either doubling the voltage by grounding the "inside legs" (-24 & +24) of the transformers or doubling the current delivery by seperating the center tap and then paralleling the secondaries.
I showed pictures of how to do it to a toroid elsewhere in this forum.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=42705
asgorath said:
Looks like a step down connection that wastes half the windings.
I do not like parallel connection of transformers. But it is done everyday with output transformers. Look at the Lundahl transformers. It takes a genius to wire one up without detailed instructions.
If you parallel two indentical transformers it should double the current handling. Real world conditions, maybe not.
George
0.1% Resistors
Hi. I'm in trouble with these 0.1% resistors locally.
The partslist specifies a couple of sizes (22k and 47k) resistors in 0.1% tolerance that I have not been able to source locally - Jaycar etc say they only buy them in for large orders.
I can get hold of a LCR meter (dunno if it gets to 0.1% accuracy tho) - If I inspect a heap of 1% tolerance resistors and select some that are within 0.1% of spec (if there are any) will that be good enough?
I make the 22k at 0.1% as 21978 - 22022, and the 47k as 46953 - 47047 ohms.
Michael
Hi. I'm in trouble with these 0.1% resistors locally.
The partslist specifies a couple of sizes (22k and 47k) resistors in 0.1% tolerance that I have not been able to source locally - Jaycar etc say they only buy them in for large orders.
I can get hold of a LCR meter (dunno if it gets to 0.1% accuracy tho) - If I inspect a heap of 1% tolerance resistors and select some that are within 0.1% of spec (if there are any) will that be good enough?
I make the 22k at 0.1% as 21978 - 22022, and the 47k as 46953 - 47047 ohms.
Michael
Re: 0.1% Resistors
You will need a meter that reads higher accuracy than most. My LCR meter only reads in 100 ohm increments on the 20k - 200K range. This is 0.5 and 0.25%.
I got lucky and found some precision resistors locally.
George
maf_au said:Hi. I'm in trouble with these 0.1% resistors locally.
The partslist specifies a couple of sizes (22k and 47k) resistors in 0.1% tolerance that I have not been able to source locally - Jaycar etc say they only buy them in for large orders.
I can get hold of a LCR meter (dunno if it gets to 0.1% accuracy tho) - If I inspect a heap of 1% tolerance resistors and select some that are within 0.1% of spec (if there are any) will that be good enough?
I make the 22k at 0.1% as 21978 - 22022, and the 47k as 46953 - 47047 ohms.
Michael
You will need a meter that reads higher accuracy than most. My LCR meter only reads in 100 ohm increments on the 20k - 200K range. This is 0.5 and 0.25%.
I got lucky and found some precision resistors locally.
George
Re: 0.1% Resistors
Michael, just get a dozen or so of 1% metal film each and match them as closely as you can with your multimeter. That will be close enough.
That is what I did on my prototype with no ill effects.
Also note, you are matching them to eachother, not to their supposed value.
Cheers.
maf_au said:Hi. I'm in trouble with these 0.1% resistors locally.
The partslist specifies a couple of sizes (22k and 47k) resistors in 0.1% tolerance that I have not been able to source locally - Jaycar etc say they only buy them in for large orders.
I can get hold of a LCR meter (dunno if it gets to 0.1% accuracy tho) - If I inspect a heap of 1% tolerance resistors and select some that are within 0.1% of spec (if there are any) will that be good enough?
I make the 22k at 0.1% as 21978 - 22022, and the 47k as 46953 - 47047 ohms.
Michael
Michael, just get a dozen or so of 1% metal film each and match them as closely as you can with your multimeter. That will be close enough.
That is what I did on my prototype with no ill effects.
Also note, you are matching them to eachother, not to their supposed value.
Cheers.
do it the same every time
Michael, If you do some preparation and check resistances carefully, you will increase your chances for success. Try to use some form of holder or clip on the end of your test leads. You want the quality of connection to be the same for each resistor checked. Keep your fingers out of the mix during the test. (stray path to ground) Be patient, let the meter "settle" to a final reading. Even with that, you may see some values "toggle" back and forth a notch or two. Select the resistors that most closely match each other. Don't overlook matching enough for 2 channels.
Agreed, you want equity, a balance in the system, more than an absolute value.
Michael, If you do some preparation and check resistances carefully, you will increase your chances for success. Try to use some form of holder or clip on the end of your test leads. You want the quality of connection to be the same for each resistor checked. Keep your fingers out of the mix during the test. (stray path to ground) Be patient, let the meter "settle" to a final reading. Even with that, you may see some values "toggle" back and forth a notch or two. Select the resistors that most closely match each other. Don't overlook matching enough for 2 channels.
Agreed, you want equity, a balance in the system, more than an absolute value.
George, Russ, Ed.
Thanks for the feedback, most appreciated
I'm matching them, and finding pairs and quads of the same values to the resolution of the meter. I'll do it with all the components I can test - can't hurt.
My 1 ohm resistors are more like 1.4 according to the meter!
I've started assembling the Mauro PCB while I wait for my BrianGT kit to turn up. Parts will eventually stop me, but I should get 90% there... If I get a chance, I'll post a pic for you experts to critique - might prevent a fireworks display
Michael
Thanks for the feedback, most appreciated
I'm matching them, and finding pairs and quads of the same values to the resolution of the meter. I'll do it with all the components I can test - can't hurt.
My 1 ohm resistors are more like 1.4 according to the meter!
I've started assembling the Mauro PCB while I wait for my BrianGT kit to turn up. Parts will eventually stop me, but I should get 90% there... If I get a chance, I'll post a pic for you experts to critique - might prevent a fireworks display
Michael
Member
Joined 2003
Since someone brought up the .1% resistors I must add that the resistors that Brain has included in the parts kit are not the exact value required, due to lack of availability. They are 22K1 and 47K5 instead of 22K0 and 47K0 so they are precision .1% tolerance resistors that are at the top end of 1% of the value asked for in the design. Therefore I must come to the conclusion that using 1% tolerance resistors in place of the .1% resistors is acceptable. Or at least precision resistors that are both +1% or both -1% of the requred value.
Hope that makes sense.
Hope that makes sense.
Member
Joined 2003
Progress so far
With a bit of luck, caps on tonight...
Comments welcome, good or bad
Theres a back piccy where you can see my warty soldering on my gallery here
Michael
With a bit of luck, caps on tonight...
An externally hosted image should be here but it was not working when we last tested it.
Comments welcome, good or bad
Theres a back piccy where you can see my warty soldering on my gallery here
Michael
Member
Joined 2003
Looking good, hoever I would put a blob of non-conductive glue on the caps that aren't flush mounted to the board to keep them from vibrating. I had mounted a capacitor on my subwoofer amp as per the last two pictures on this page and just today was scared to death when it sounded like my subwoofer was shot. It sounded like the speaker cable had fallen loose. It turned out to be that due to the constant vibration of the capacitor (the plate amp is mounted externally, so I thought vibration would not be a problem), the resistor leg it was soldered to had broken off.
All I am saying is that even the smallest vibration over time can break a component leg. Also be sure to either drill the holes for the faston connectors larger, or mangle the square legs of the connectors so they are round.
All I am saying is that even the smallest vibration over time can break a component leg. Also be sure to either drill the holes for the faston connectors larger, or mangle the square legs of the connectors so they are round.
Re: Progress so far
Good Job Michael,
One thing I always do is I keep the hot or positive lead of my polarized pin hearders on the right (assuming the guide part of the header is the back). This help tremendously when wiring your connectors, as they all will be the same.
You would simply need to flip conn2 to get it that way.
Cheers!
Russ
maf_au said:With a bit of luck, caps on tonight...
An externally hosted image should be here but it was not working when we last tested it.
Comments welcome, good or bad
Theres a back piccy where you can see my warty soldering on my gallery here
Michael
Good Job Michael,
One thing I always do is I keep the hot or positive lead of my polarized pin hearders on the right (assuming the guide part of the header is the back). This help tremendously when wiring your connectors, as they all will be the same.
You would simply need to flip conn2 to get it that way.
Cheers!
Russ