Re: Re: Exact lead info
I agree with your comments. Sorry I didn't pay attention to the wiring colours. That's certainly it.
Though it might be worth peel up the 24v wires to see if they are not thin. That might be dangerous or at least affect the toroid's specs.
It's interesting that today I opened a thread at "Solid State" asking if someone had added more spires to an existing toroid to get more voltage. My intention was exactly what you described: feed the frontend on an amp I have.
jaycee said:
I agree with your comments. Sorry I didn't pay attention to the wiring colours. That's certainly it.
Though it might be worth peel up the 24v wires to see if they are not thin. That might be dangerous or at least affect the toroid's specs.
It's interesting that today I opened a thread at "Solid State" asking if someone had added more spires to an existing toroid to get more voltage. My intention was exactly what you described: feed the frontend on an amp I have.
From the descripition "4 pairs of wires" I would read that there are no internal connections (that is, 4 true seperate windings), and the voltages are spec'd per pair, so it could be wired as 44-20-0-20-44, not as 24-20-0-20-24 (but as 24-0-24 plus 20-0-20 and many other variations).
I would definitely go ahead and do some measurements, checking DC-R and internal connections/shorts, maybe inductances and then actual voltages. If the the windigs are seperate and voltages/inductances and DC-Rs match within a few percent (for the 20V pairs and the 24V pairs, resp.), they can be paralleled (but get the phases right: parallel only one side, and check for close to zero volts on the other, if you get 40V or 48 you have do reverse one winding). Also, if the DC-R of the 24V windings is about 1.2 times that of the 20V windings they will be able to carry the same current/power (being the same wire gauge). Thus you can get the whole 300VA from the tranny (if you don't use all wingings -- in case the are really seperate --, you can only draw about 1/2 to 2/3 power to not overheat the secondaries). If it's a LM3886 (or other National chip) CG, you can run it with slighty assymetric supplies with not problem. The bigger voltage (from the 24V) should feed the positive rail for these chips.
Regards, Klaus
I would definitely go ahead and do some measurements, checking DC-R and internal connections/shorts, maybe inductances and then actual voltages. If the the windigs are seperate and voltages/inductances and DC-Rs match within a few percent (for the 20V pairs and the 24V pairs, resp.), they can be paralleled (but get the phases right: parallel only one side, and check for close to zero volts on the other, if you get 40V or 48 you have do reverse one winding). Also, if the DC-R of the 24V windings is about 1.2 times that of the 20V windings they will be able to carry the same current/power (being the same wire gauge). Thus you can get the whole 300VA from the tranny (if you don't use all wingings -- in case the are really seperate --, you can only draw about 1/2 to 2/3 power to not overheat the secondaries). If it's a LM3886 (or other National chip) CG, you can run it with slighty assymetric supplies with not problem. The bigger voltage (from the 24V) should feed the positive rail for these chips.
Regards, Klaus
IIRC, the old Velodyne stand alone amp was 350W/4R, a class G or H design.
350W/4R = 37.42V RMS, 52.9V Peak.
44-20-0-20-44 RMS will be about ±62V and ± 27V.
If the 24V windings may be used by themselves, they would probably be too much for a GC driving "a pair of current hungry ATC 4ohm" (unless you paralleled the GC part for each channel).
350W/4R = 37.42V RMS, 52.9V Peak.
44-20-0-20-44 RMS will be about ±62V and ± 27V.
If the 24V windings may be used by themselves, they would probably be too much for a GC driving "a pair of current hungry ATC 4ohm" (unless you paralleled the GC part for each channel).
Hi,
the 24Vac windings are not a big problem.
build up the first amp with it's dual rectifier and smoothing off the pair of 20Vac windings.
Check the unloaded DC voltage and then the quiescent DC voltage and finally the full power DC supply voltage. If you have an oscilloscope you can also measure the full power rail ripple voltage.
With this information, you can decide if the 24Vac windings will be about right for the less sensitive driver or if too high.
It it transpires that 24Vac is too high then simply unwrap the transformer and remove half a dozen turns from each 24V winding. remeasure the 20Vac and lowered24Vac windings and calculate how many more turns should be removed to get to your highest tolerable AC voltage.
The 20Vac winding is 70VA so the pair are 140VA. This is just about enough for a pair of amps running @ 50W to 60W per channel. The adjusted 24Vac winding will end up between 140VA and 168VA. Again enough for two channels of 50W to 60W.
I presume you are building a 4channel amplifier to passively bi-amp the ATCs. That means each pair of windings will be supplying two amplifier channels. The only way I can keep these quiet is to run separate windings for each amplifier. I think you will need to follow other chipampers advice on minimising hum for a stereo amp on single transformer. You effectively will have a stereo amp running off each pair of windings.
the 24Vac windings are not a big problem.
build up the first amp with it's dual rectifier and smoothing off the pair of 20Vac windings.
Check the unloaded DC voltage and then the quiescent DC voltage and finally the full power DC supply voltage. If you have an oscilloscope you can also measure the full power rail ripple voltage.
With this information, you can decide if the 24Vac windings will be about right for the less sensitive driver or if too high.
It it transpires that 24Vac is too high then simply unwrap the transformer and remove half a dozen turns from each 24V winding. remeasure the 20Vac and lowered24Vac windings and calculate how many more turns should be removed to get to your highest tolerable AC voltage.
The 20Vac winding is 70VA so the pair are 140VA. This is just about enough for a pair of amps running @ 50W to 60W per channel. The adjusted 24Vac winding will end up between 140VA and 168VA. Again enough for two channels of 50W to 60W.
I presume you are building a 4channel amplifier to passively bi-amp the ATCs. That means each pair of windings will be supplying two amplifier channels. The only way I can keep these quiet is to run separate windings for each amplifier. I think you will need to follow other chipampers advice on minimising hum for a stereo amp on single transformer. You effectively will have a stereo amp running off each pair of windings.
Thanks to all!
Some of the info above is over my newbie head. But the important basics will get me the stereo GC built.
Sorry - only using GC as two channel with another amp (I'll use a stereo kit)
Talking to Toroid Inc. engineer, said yes there are 4 separate windings.
Lead wires are 14 guage.
Yes I think the Velodyne ULD18 had a MOSFET op stage.
I believe it was rated at 400W (mono).
Some of the info above is over my newbie head. But the important basics will get me the stereo GC built.
Sorry - only using GC as two channel with another amp (I'll use a stereo kit)
Talking to Toroid Inc. engineer, said yes there are 4 separate windings.
Lead wires are 14 guage.
Yes I think the Velodyne ULD18 had a MOSFET op stage.
I believe it was rated at 400W (mono).
400W output from a 300VA transformer.
That is certainly not a continuous output specification.
5% duty cycle maybe, but that is cheating.
300VA can support 150W to 300W of reasonable quality output.
I would use 300VA for a 100W +100W two channel amp, or four/five channels of 50W each.
Which bits need further explanation?
When you're ready just ask.
Hi,
unloaded DC is the peak voltage on the smoothing capacitors, when there is no load connected. This and all that follow should be corrected from actual mains input voltage to nominal mains supply voltage.
Quiescent DC is the PSU voltage when the amplifier/s are connected and drawing their quiescent current.
There will be a small amount of ripple in this condition, maybe around 10mVpp. Some DVM can obtain an approximate measure of this ripple when set to mVac even though the DC voltage across the probes is many tens of volts. The AC voltage will be approximately 30% of the Vpp displayed on a scope.
When a load is driven the PSU supply voltage drops. The ripple also goes up. the useful voltage is the average voltage measured by the DVM less half the peak to peak ripple voltage (half of Vpp~=1.5*mVac measured by the DVM).
These numbers can tell a lot about how the PSU is performing.
unloaded DC is the peak voltage on the smoothing capacitors, when there is no load connected. This and all that follow should be corrected from actual mains input voltage to nominal mains supply voltage.
Quiescent DC is the PSU voltage when the amplifier/s are connected and drawing their quiescent current.
There will be a small amount of ripple in this condition, maybe around 10mVpp. Some DVM can obtain an approximate measure of this ripple when set to mVac even though the DC voltage across the probes is many tens of volts. The AC voltage will be approximately 30% of the Vpp displayed on a scope.
When a load is driven the PSU supply voltage drops. The ripple also goes up. the useful voltage is the average voltage measured by the DVM less half the peak to peak ripple voltage (half of Vpp~=1.5*mVac measured by the DVM).
These numbers can tell a lot about how the PSU is performing.
This weekend the case gets put together, toroid mounted.- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.