| A3rd.Zero |
I am using a Hammond 261c6 power transformer for my tube pre amp and I only need 110v out of it (it is a 220V centertapped). If I just use the centertap and one end of the winding can I clip the other end of the winding short and just tape it?
Primary 1___.......___+110V
.................) || (
.................) || (___ 0V
.................) || (
Primary 2___) || (____-110V
Thanks for the help.
Milo
edit: formatting |
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| SY |
Yes.
What is it you're trying to do? Maybe there's a better approach. |
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| A3rd.Zero |
The tube pre amp that I am building is much like the Morgan Jones one over on Headwize, except it uses a 12au7 and two 6Dj8's insted of three 6dj8's. In the power supply section of the schematic it calls for a 110V secondary winding and a 6.3V secondary winding. The transformer that I have on hand is the 261c6 which is setup to give 220V but I though that because of the center tap I could use it for the 110V required by the schematic.
The Preamp is a clone of the Radii HAP-03 incase that helps. I could email you the schematic if you are interested.
Thanks for your help.
Milo |
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| SY |
| Yes, I'd like to see a schematic. Thanks! |
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| choky |
mebbe is better solution to use both halves ?
CT to ground,and wo diodes (one per half) to + output-just like good ole vacuum rectifier?
in that case your tranny will run colder |
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| stormy |
| quote: | Originally posted by choky
mebbe is better solution to use both halves ?
CT to ground,and wo diodes (one per half) to + output-just like good ole vacuum rectifier?
in that case your tranny will run colder |
I agree with this
better not to leave floating windings ;) |
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| ShiFtY |
| Yes, you should use a full wave rectifier, then you only need 2 diodes! Less sand in your system! :D |
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| A3rd.Zero |
Ok, here is the schematic. I know that there are better ways to do this but Im trying to stay as close to "cloning" the amp as possible. I plan to use 4 FREDS for the fullwave rectifier, each is rated to 12A and 1200V so even if I parallel the winding I won't be heating up the FREDS. Is there a problem with supplying twice the amperage to the amp, or will it only draw what it needs anyway?
Thanks for your help guys.
Milo
edit: spelling |
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| A3rd.Zero |
oops, here it is.
Milo |
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| fdegrove |
Hi,
That looks alot like a headphone amp I've seen on Headwize.
Runeight, was that yours?
An anode follower DC coupled into a WCF, nice.
It's very easy to add a bigger cap on the output and a jack so you'll be driving your cans with it as well.
Here's something similar I toyed with a while ago:
Cheers,;) |
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| A3rd.Zero |
Yeah, its alot like the Morgan Jones on headwize but it differs in a few ways. It is the HAP-03 made by RADII out of China. Its a real POS but if you can get it to work it sounds really nice with Senn HD-600's. Ill be using mostly High ohm cans so I think that I can keep the Output Cap low, if not however Ill just add it to the headphone jack.
Thanks
Milo |
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| fdegrove |
Hi,
| quote: | | I plan to use 4 FREDS for the fullwave rectifier, each is rated to 12A and 1200V so even if I parallel the winding I won't be heating up the FREDS. Is there a problem with supplying twice the amperage to the amp, or will it only draw what it needs anyway? |
Someone once advised against the use of HEXFRED diodes, I forgot why exactly but I suppose they were misbehaving.
Either way, if you can't get Schottkys to do the job I'd put some snubber caps across the diodes.
12A is way too much but it'll only hurt the bank, I suppose.
The preamp will only draw whatever it need, so while it's overkill it won't do any damage.
Cheers,;) |
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| A3rd.Zero |
I thought that was the way it was with current. So do I need to rectify each side of the 220V winding seperatly or is there a way that I can rectify it at the same time and still get 110V with twice the current? Basically do I need to buy 4 more freds? The 12A ones were the same price as the 6A ones and I figured that it will just keep the heat down so what the hey. What would you recommend as snubber caps, type, rating? I know that that is an absurdly broad question but I only know enough to know that the question is broad not what I should use.
He he, at least im not asking "What is the best capacitor ever?"
Thanks,
Milo |
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| A3rd.Zero |
CHOKY
Im interested in that solution but im still to new at this. could you draw me a picture. Ill post it on my refridgerator :)
Thanks
Milo |
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| choky |
| quote: | Originally posted by A3rd.Zero
CHOKY
Im interested in that solution but im still to new at this. could you draw me a picture. Ill post it on my refridgerator :)
Thanks
Milo |
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| A3rd.Zero |
oooo fancy!
So I gather that the schematic has good PS noise rejection right? Thats why you can get away with just using a full wave rather than a bridge rectifier. Or am i missing the point.
Thanks for the help.
Milo |
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| fdegrove |
Hi,
| quote: | | Thats why you can get away with just using a full wave rather than a bridge rectifier. Or am i missing the point. |
Both the graetz bridge and the FW rectifiers are errr...FW rectifiers.
It's just that the bridge is much more efficient, something you don't want here.
Both need to be filtered adequately just the same.
Cheers,;) |
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| A3rd.Zero |
Thanks Fdegrove,
Could you explain the efficienty issues? Why dont i want the more efficient solution?
Thanks
Milo |
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| fdegrove |
Hi,
| quote: | | Why dont i want the more efficient solution? |
Efficient in the sense that it would put out a higher voltage, since you said in your opening post that you only need 110V I assume
there's little point in turning excess voltage into heat.
You'll already see close to 125 VDC max on the filter caps.
Using a FW bridge and NOT grounding the CT would give you twice as much volts in theory.
If that's what you want then that's fine by me. ;)
Cheers,;) |
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| A3rd.Zero |
I dont know if the powersupply section calls for delivery of 110V or if that is just the winding of the transformer that they used (the schematic is a little unclear because they never give voltages at test points). If I were to construct a powersupply as below, wouldnt I have basically 110V (not taking into account RMS due to the rectifier or the caps) and just twice the amperage that each side of the winding could produce? Again sorry if I'm totally missing something.
Thanks,
Milo |
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| stormy |
| quote: | Originally posted by A3rd.Zero
I dont know if the powersupply section calls for delivery of 110V or if that is just the winding of the transformer that they used (the schematic is a little unclear because they never give voltages at test points). If I were to construct a powersupply as below, wouldnt I have basically 110V (not taking into account RMS due to the rectifier or the caps) and just twice the amperage that each side of the winding could produce? Again sorry if I'm totally missing something.
Thanks,
Milo |
Come on guys how can you connect a transformer winding like that!.
you can only wire seperate windings in paralel if you connect a winding with a centre tap like that you have effectivly shorted
out the winding Come on look @ it.
Regards stormy |
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| A3rd.Zero |
Ok, right I see that, sorry.
thanks,
milo |
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| fdegrove |
Hi,
Milo,
The xformer on the diagram you posted states 110V 40mA.
With 0-110V + FW bridge rectifer that gives us about 150VDC, after the RC filtering it's even less but so be it.
So, with the 110V-0-110V xfromer you'll need to hook up a bridge just as in the diagram and all you that you can't do is ground the the CT.
Personally I'd work with at least twice that B+ but that would require a redesign of most Rs in the schem.
Cheers,;)
P.S. What I don't understand is that if the 110V is AC then the 12.6 V for the heaters must be DC or else it'll be way too high.
If the 110V is DC then the powerxformer is a 0-80 V one.
In that case a simple FW rectifier with two diodes as Choky showed would come closer to 110VDC with your xformer. |
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| stormy |
| quote: | Originally posted by fdegrove
Hi,
Milo,
The xformer on the diagram you posted states 110V 40mA.
With 0-110V + FW bridge rectifer that gives us about 150VDC, after the RC filtering it's even less but so be it.
So, with the 110V-0-110V xfromer you'll need to hook up a bridge just as in the diagram and all you that you can't do is ground the the CT.
Personally I'd work with at least twice that B+ but that would require a redesign of most Rs in the schem.
Cheers,;)
P.S. What I don't understand is that if the 110V is AC then the 12.6 V for the heaters must be DC or else it'll be way too high.
If the 110V is DC then the powerxformer is a 0-80 V one.
In that case a simple FW rectifier with two diodes as Choky showed would come closer to 110VDC with your xformer. |
I am looking for a diagram here where that would work and I cant see one.
If you connect the bridge across the two outer points on the winding and grounding the centre tap then every half cycle
a diode in the bridge would be shorting out half the winding
The only way posible here with a bridge, is to fit it across the
centre tap and one side of the winding. which leaves a floating
winding,
you could always add a second bridge.:hot:
regrds stormy |
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| fdegrove |
Hi,
Stormy,
| quote: | | If you connect the bridge across the two outer points on the winding and grounding the centre tap then every half cycle |
I said:
"as in the diagram and all you that you can't do is ground the the CT."
The diagram is here:
STILL NOT BIG ENOUGH...
| quote: | | The only way posible here with a bridge, is to fit it across the centre tap and one side of the winding. which leaves a floating winding, |
No, you can use a bridge just the same provided you DO NOT ground the CT.
Hey, it's even an hour later for me here, ya know.:smash:
Cheers,;) |
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| stormy |
Just had a thought for your spare winding.
you could fit a smaller stepdown transformer on that winding and supply your heater. :devilr:
hehe
i think shiftys 2 diode and center tap ground is going to be
your best bet.
regards stormy. |
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| stormy |
| quote: | Originally posted by fdegrove
Hi,
Stormy,
I said:
"as in the diagram and all you that you can't do is ground the the CT."
The diagram is here:
STILL NOT BIG ENOUGH...
No, you can use a bridge just the same provided you DO NOT ground the CT.
Hey, it's even an hour later for me here, ya know.:smash:
Cheers,;) |
Verry sory mr Fdegrove,
The problem I had with can and can't is the way your english dialog came across the way you aproached the centence , a
"can" is more apropreate.
sorry for the missunderstanding.
regards stormy (insomniac) is what i should have called myself |
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| fdegrove |
Hi,
| quote: | | i think shiftys 2 diode and center tap ground is going to be |
In which case he's going to end up about ten volts short of the target voltage.
Cheers,;)
EDIT: Just spotted your last posting.
| quote: | | regards stormy (insomniac) is what i should have called myself |
Don't kill yourself, will you?:clown:
No worries.;) |
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| stormy |
| quote: | Originally posted by fdegrove
Hi,
In which case he's going to end up about ten volts short of the target voltage.
Cheers,;)
EDIT: Just spotted your last posting.
Don't kill yourself, will you?:clown:
No worries.;) |
ok I can see it got to be 1 of the lesser evils here:cannotbe:
modify the circuit with "shortfall" on half the winding, or
modify the circuit with "excesive" voltage using bridge across
full winding (or disapate a lot in heat.
if he shoves the bridge across just one side of the winding
then he has less to dissapate.
regards stormy;) |
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| A3rd.Zero |
Ok so I did some reading up and here is where I am. The full wave rectifier setup with a centertapped transformer like choky drew would work except for the fact that the secondary winding is rated at 45ma and I would need 56ma to allow for the full wave(non brdige) circuit. So is the only other option to only use half of the winding and cut off the other half or is there an option that I have missed?
Could I do a split supply using a bridge rectifier and use half of the supply for the left channel and half of the supply for the right channel. Does it matter that the left or right channel would be using a -V relitave to the ground. It seems like that might be a problem but I have learned that my initial assumptions regarding electronics are almost always wrong.
Thanks
Milo |
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| fdegrove |
Hi,
Let's not forget that 1/2 winding implies also 1/2 of the available current of the total secondary.
Cheers,;) |
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| A3rd.Zero |
Fedgrove, oh yeah, shoot. Ok well maybe I need a different transformer.
Thanks for all your help by the way!
Milo
edit:tired |
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| fdegrove |
Hi,
| quote: | | Thanks for all your help by the way! |
You're welcome.
What exactly is the current rating of the xformer you have for that secondary winding alone?
The reason I ask is that whatever way you rectify, peak current may differ depending on how you rectify but you just can't pull more current steady state than the xformer can deliver.
Cheers,;) |
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| stormy |
| quote: | Originally posted by A3rd.Zero
Ok so I did some reading up and here is where I am. The full wave rectifier setup with a centertapped transformer like choky drew would work except for the fact that the secondary winding is rated at 45ma and I would need 56ma to allow for the full wave(non brdige) circuit. So is the only other option to only use half of the winding and cut off the other half or is there an option that I have missed?
Could I do a split supply using a bridge rectifier and use half of the supply for the left channel and half of the supply for the right channel. Does it matter that the left or right channel would be using a -V relitave to the ground. It seems like that might be a problem but I have learned that my initial assumptions regarding electronics are almost always wrong.
Thanks
Milo |
Hi
You could fit 2 bridges and this would give you 2 positive and a comman ground to do that but it still wont help you get the power
you need.
I think you might have to sourse another transformer for the
solution.
regards stormy |
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| fdegrove |
Hi,
O.K....I looked up the Hammond 261C6, this is a 250VAC CT xformer so in essence you should have 125-CT-125 @ 45mA + 6.3V @ 1A for a heater.
The circuit you showed draws 40mA avg, so what's the problem?
A full wave (sans bridge) will give you...where's the calc.....177 VDC max (peak) and 112.6 VDC (avg).
Ain't that grand?
Cheers, ;) |
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| stormy |
| quote: | Originally posted by fdegrove
Hi,
O.K....I looked up the Hammond 261C6, this is a 250VAC CT xformer so in essence you should have 125-CT-125 @ 45mA + 6.3V @ 1A for a heater.
The circuit you showed draws 40mA avg, so what's the problem?
A full wave (sans bridge) will give you...where's the calc.....177 VDC max (peak) and 112.6 VDC (avg).
Ain't that grand?
Cheers, ;) |
Hi,
Nice work Mr Fdegrove :D you da man
regards stormy:rolleyes: |
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| A3rd.Zero |
Fedgrove,
Ok right, thats all well and good but in my trusty Horwitz & Hill (which I need to read more i know) it says that with the setup that choky drew (sans bridge right?) that yo0u need a transformer with a current rating 1.4 times as large as with a bridge rectifier. Seeing as how the 110V winding goes through a bridge rectifier if I was to use a 110V winding on a sans bridge then wouldnt I need 56ma insted of 40ma?
Thanks
Milo
edit: I know, I know, Im sure that Im missing something else. |
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| fdegrove |
Hi,
| quote: | | Ok right, thats all well and good but in my trusty Horwitz & Hill (which I need to read more i know) it says that with the setup that choky drew (sans bridge right?) that yo0u need a transformer with a current rating 1.4 times as large as with a bridge rectifier. |
Remember when I brought up effeciency?
What Horowitz & Hill mean is peak current and voltage. By which I assume they compared it to a half wave rectifier.
Since the output waveform is essentially a sine wave with both alternations at the same polarity, the average current or voltage is 63.7 percent (or 0.637) of the peak current or voltage.
So, when we do the equations we'll see that this type of rectifier isn't very effecient, in fact compared to a FW bridge we lose about half the voltage.
But, and this is what you're missing, we have 125-CT-125, so it almost amounts to doing the same math with a 0-125 volt xformer and using the formula for a FW bridge:
125 * 1.141 = 142.625.
The math I did on your xformer arrived at about 112 volt for the FW using the entire xformer.
As you can see it's not that far apart but the FW is dreadfully inefficient at just 63.7% which is why a FW bridge is almost universally used in modern electronics: 114% efficiency.
So the FW bridge produces the same peak voltage as the half wave rectifier but with the same frequency of the FW rectifier.
Neither of the equations included the voltage drop of the diodes ( 0.6 V per diode usually) as it is neglible for all practical purposes.
Hope this helps,;) |
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| A3rd.Zero |
Yeah, it helps alot. Thank you!
I know that Im ok with voltage but what about current? Wont I need 1.4 times the current?
Thanks again I know that this is likely getting annoying.
Milo |
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| fdegrove |
Hi,
| quote: | | I know that Im ok with voltage but what about current? Wont I need 1.4 times the current? |
No you won't. Your circuit's only drawing 40mA, you have 45mA to start with, nothing got stolen in the process.:whazzat:
I=V/R so R=V/I.
Cheers,;) |
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| A3rd.Zero |
Ok, Thanks.
Sorry for being so dense about this stuff. I appreciate all your help! Thanks again.
Milo |
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| A3rd.Zero |
Nice wayne! thanks.
Milo |
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| cogsncogs |
Your very welcomeness! :D :D :D
Wayne |
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