I'm just about done with my first GC! Before I plug it in, though, I wanted to clear up something about the power supply.
I looked at the schematic for Peter and Brian's GC kit. As you know this uses a dual secondary TX to get dual rails, a full bridge rectifier for each rail (4 diodes per rail, total of 8), and these two rails are referenced to ground between the two.
The PS I've built is different.
I'm using a dual secondary transformer, but only one bridge (4 diodes). I'm paralleling the dual secondary stages to increase current.
From there, the + pin of the rectifier supplies the + power for both the left and right channels. Similarly, the - pin of the rectifier supplies the - power for both the left and right channels.
With this type of setup, do I need to reference anything to ground? That is, do I need to tie the + and - pins of the rectifer together and bring this to ground? If so, would I place a small cap (4.7uF) between each pole and ground?
I'm confused because I've seen a schematic for a single rail supply that ties both rails to ground like this, but it used a center tapped transformer (center tap was also tied to ground).
Transformer I'm using is dual secondary, but not center tapped.
Thanks a lot,
KT
I looked at the schematic for Peter and Brian's GC kit. As you know this uses a dual secondary TX to get dual rails, a full bridge rectifier for each rail (4 diodes per rail, total of 8), and these two rails are referenced to ground between the two.
The PS I've built is different.
I'm using a dual secondary transformer, but only one bridge (4 diodes). I'm paralleling the dual secondary stages to increase current.
From there, the + pin of the rectifier supplies the + power for both the left and right channels. Similarly, the - pin of the rectifier supplies the - power for both the left and right channels.
With this type of setup, do I need to reference anything to ground? That is, do I need to tie the + and - pins of the rectifer together and bring this to ground? If so, would I place a small cap (4.7uF) between each pole and ground?
I'm confused because I've seen a schematic for a single rail supply that ties both rails to ground like this, but it used a center tapped transformer (center tap was also tied to ground).
Transformer I'm using is dual secondary, but not center tapped.
Thanks a lot,
KT
KT,
although it might seem easy to establish a "single rail" topology like you were suggesting or planning, it is simply not possible. For a ground referenced amplifier you will need two supply voltages. You cannot parallel the secondaries, etc.
But you can use a single 4 diodes bridge only (two lines to the bridge and the oher two to ground). Only beware of the phases of the transformer's secondaries (must be in line).
Wasn't that not the Gaincards/Humpties orginal schematic to use only one bridge? And wasn't that you who opened the PowerHumpty first? Or was it somebody else named KT?
Klaus
although it might seem easy to establish a "single rail" topology like you were suggesting or planning, it is simply not possible. For a ground referenced amplifier you will need two supply voltages. You cannot parallel the secondaries, etc.
But you can use a single 4 diodes bridge only (two lines to the bridge and the oher two to ground). Only beware of the phases of the transformer's secondaries (must be in line).
Wasn't that not the Gaincards/Humpties orginal schematic to use only one bridge? And wasn't that you who opened the PowerHumpty first? Or was it somebody else named KT?
Klaus
Thank you for the advice, everyone.
Yes, I was thinking of using a single 4 diode rectifier bridge as seen in the 47 Labs gear. Obviously, I will need to do some more research before I finish the amp up.
I greatly appreciate the insight from Carlos regarding voltage limits. I was under the impression that 22v secondaries would be acceptable for the LM1875. I will look for a suitable transformer before I continue.
It was me who opened up the Power Humpty. I have it in my system now, so I haven't cracked it open for some time. I was planning on sharing some photos, so maybe when I successfully complete my first GC I will have a chance to pull the Humpty out of the system and open it up.
I can't promise how long that might be, however. Soon, I hope!
Is there any site that will give me a good tutorial on putting together a suitable 4 diode supply? I can pick things up fairly quickly, but I'm definitely not an engineer. Glad to have all of your help. Safety first, of course!
Best,
KT
Yes, I was thinking of using a single 4 diode rectifier bridge as seen in the 47 Labs gear. Obviously, I will need to do some more research before I finish the amp up.
I greatly appreciate the insight from Carlos regarding voltage limits. I was under the impression that 22v secondaries would be acceptable for the LM1875. I will look for a suitable transformer before I continue.
It was me who opened up the Power Humpty. I have it in my system now, so I haven't cracked it open for some time. I was planning on sharing some photos, so maybe when I successfully complete my first GC I will have a chance to pull the Humpty out of the system and open it up.
I can't promise how long that might be, however. Soon, I hope!
Is there any site that will give me a good tutorial on putting together a suitable 4 diode supply? I can pick things up fairly quickly, but I'm definitely not an engineer. Glad to have all of your help. Safety first, of course!
Best,
KT
If you had two seperate transformers with single secondaries you can connect the secondaries to create a center tap.
And lohk says its possible to do this with a single transformer as well, and im sure hes right
Do some research on the windings though, if its two seperate transformers you just take the opposite wires and tie them together (hot to cold) to make the ground. Maybe one is more complicated.
Here is a power supply diagram: Full Wave (only the top left part)
You can make it simpler or as complicated as you want (take out the regulators).
Oh and it should have equal capacitance on each rail (I guess that pictures not a great one).
And lohk says its possible to do this with a single transformer as well, and im sure hes right
Do some research on the windings though, if its two seperate transformers you just take the opposite wires and tie them together (hot to cold) to make the ground. Maybe one is more complicated.
Here is a power supply diagram: Full Wave (only the top left part
)You can make it simpler or as complicated as you want (take out the regulators).
Oh and it should have equal capacitance on each rail (I guess that pictures not a great one).
kt, the lm3875 chip will work with 22v secondaries. (about +-31vdc)
there is an illustration of a single bridge / dual secondary psu here, http://gainclone.com/ps_gc_1.gif
it will be good to see photos of the inside of the humpty when you have time. i quite enjoy seeing kimura's approach.
there is an illustration of a single bridge / dual secondary psu here, http://gainclone.com/ps_gc_1.gif
it will be good to see photos of the inside of the humpty when you have time. i quite enjoy seeing kimura's approach.
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