kevyjo said:
Check out www.plitron.com, under "tech notes" on the right side of the screen. Tells you what you need to know about transformers on one page.
I hope this is all ok dw8308, thought you might have transformer questions also, dont mean to hijack youre thread. What do you guys think of these guys, is there any reason these wouldnt work?
http://www.coilws.com/Toroidal Power Tx/Toroid_Pwr_PN.php
By the way, thank you for the help, I understand the specifications now
http://www.coilws.com/Toroidal Power Tx/Toroid_Pwr_PN.php
By the way, thank you for the help, I understand the specifications now
Yes, my understanding from Nelson's text is that he used the two 30 volt transformers because a transformer rated around 60 volts wasn't available. Since Plitron has 55 and 60 volt transformers, you only need one. I believe that Nelson uses the same transformer source for both channels. So, you could use only one 55 volt transformer for the whole stereo preamp, or use one per channel if you want to be super high end. As far as whether you want 60 volts or 55 or 50, I don't know. All I remember from a members post was that his circuit was getting really hot burning off extra power while regulating it.
Personally, since a single transformer is a lot cheaper generally than using 2, and since a transformer with double the power is only a little bit more expensive, I am tempted to use a more powerful unit than Nelson mentions. So, I'll probably use the 55 volt model.
Personally, since a single transformer is a lot cheaper generally than using 2, and since a transformer with double the power is only a little bit more expensive, I am tempted to use a more powerful unit than Nelson mentions. So, I'll probably use the 55 volt model.
SOOOO, Let me see if I have this right. I'll just talk about the piltron transformers for clarity. If one went the "standard" route, they would use two 30VA toroids with 30v output, and a current rating of .5A a piece. This is expensive though, for the same money one could buy one gigantic 500VA transformer at 55v output, and a current rating of 4.55A (#87052201). More practical price wise would be a single 300VA 55V output, and a 2.73A rating (#077042201). A "high end" route would be two 160VA at 30v output, with a huge combined current rating of 5.34A (57041201).
I dont know what the best route to go is. The one 300VA is cheaper than two 30VAs, so if it works just as well if not better, it seems it would be the way to go if one was trying to save money. For the high end route, two 160VAs is not really much more expensive than the standard route, and I don't know if one could use a 500VA one, would this fry other parts??
I don't know about other questions. Others have talked about metal cans, as far as i can see, the piltron ones dont have metal cans. I'm not overly concerned with asthetics INSIDE the preamp, but if it helped with noise then I would do it.
I dont know what the best route to go is. The one 300VA is cheaper than two 30VAs, so if it works just as well if not better, it seems it would be the way to go if one was trying to save money. For the high end route, two 160VAs is not really much more expensive than the standard route, and I don't know if one could use a 500VA one, would this fry other parts??
I don't know about other questions. Others have talked about metal cans, as far as i can see, the piltron ones dont have metal cans. I'm not overly concerned with asthetics INSIDE the preamp, but if it helped with noise then I would do it.
Righto I believe. I'm sure that others will correct me if I'm wrong.
A huge transformer will of course not "force" too much power into the circuit, EXCEPT for that somewhat higher voltage thing due to the lack of voltage sag that I mentioned before. (because the transformer it's so lightly loaded.) Which pretty much DOES "force" more power into the circuit. You can compensate for this by using slightly lower voltage. HOw much lower I don't know, but I am guessing the 55 volts
There seems to be general agreement that big transformers are good , even in preamps.
Personally, I'd be tempted by one 160 VA transformer per channel which are each twice what Nelson speced. Also he said two channels would run from what he speced, so you are in effect using 4 times the size.
Well, this is what I wouldn't do it I understand you correctly.
For high end I would use two 160 VA at 55 volts each. One for each channel. The question is: Does Plitron make a 55v 160 VA transformer? Using 2 per channel has no advantage to my knowledge
EDIT: Plitron seems to have dual 55 volt output 160VA transformers. The next size up is somewhat bigger jump in price.
Since 160VA is huge in this context, I'd use one of these for each channel (or one total for both channnels combined which should fine and half price)
A huge transformer will of course not "force" too much power into the circuit, EXCEPT for that somewhat higher voltage thing due to the lack of voltage sag that I mentioned before. (because the transformer it's so lightly loaded.) Which pretty much DOES "force" more power into the circuit. You can compensate for this by using slightly lower voltage. HOw much lower I don't know, but I am guessing the 55 volts
There seems to be general agreement that big transformers are good , even in preamps.
Personally, I'd be tempted by one 160 VA transformer per channel which are each twice what Nelson speced. Also he said two channels would run from what he speced, so you are in effect using 4 times the size.
Well, this is what I wouldn't do it I understand you correctly.
For high end I would use two 160 VA at 55 volts each. One for each channel. The question is: Does Plitron make a 55v 160 VA transformer? Using 2 per channel has no advantage to my knowledge
EDIT: Plitron seems to have dual 55 volt output 160VA transformers. The next size up is somewhat bigger jump in price.
Since 160VA is huge in this context, I'd use one of these for each channel (or one total for both channnels combined which should fine and half price)
Yes, if we are talking there standard transformers, Piltron offers 160VA 55v output, along with pretty much every other specification. I'm a little confused agan however, does the "standard" parts list include one or two 30VA transformers per side? If it is one, then it doesnt make sense to replace a 30VA, 30v output one with a 160VA, 55v output one, but if it is 2, then youre talking a total of 4 30VA, 30v output transformers, VERY expensive.
So if I'm understanding you correctly, you can use 4 30vas, which would have a total current rating of 2A, or 2 160vas 55w output, which would have a total current rating of 2.9A, or one 300va, 55v (or 50v??) output with a current rating of 2.73A. Is this right? Or could you possibly use the one 500VA, 50v output at a 5A rating?
So if I'm understanding you correctly, you can use 4 30vas, which would have a total current rating of 2A, or 2 160vas 55w output, which would have a total current rating of 2.9A, or one 300va, 55v (or 50v??) output with a current rating of 2.73A. Is this right? Or could you possibly use the one 500VA, 50v output at a 5A rating?
A couple of points/questions:Variac said:
1) Variac - I think you meant 30 VA instead of 30 volts - got me confused for a sec.
2) Why does a Plitron 30 VA trans cost twice as much as an almost identical Avel 30 VA trans? Is this a rip-off, or is there something I am missing?
3) If we want to increase the capacitance bank of the bosoz, do we just increase the caps (C101 and C102), or is there some other part that has to be changed accordingly? Does the same hold true for the AC filter cap? Is it a good idea to add a bigger AC filter cap? When adding a large capacitance bank, is it better to do so using a large number of smaller caps or a smaller number of larger caps? (I remember seeing something on this around the forum). Thanks.
Hi kevyjo,
You are very considerate. And yes, I find the transformer discussion very interesting. There is not enough discussion about the various transformer options and sonic quality differences between the manufacturers.
Wire question:
Could anyone comment on their thoughts for internal wire selection, both gauge, type, and possible brand?
Component question:
I'm looking for suggestions on resisters or capacitors as well to upgrade.
Thanks!
-David
You are very considerate. And yes, I find the transformer discussion very interesting. There is not enough discussion about the various transformer options and sonic quality differences between the manufacturers.
Wire question:
Could anyone comment on their thoughts for internal wire selection, both gauge, type, and possible brand?
Component question:
I'm looking for suggestions on resisters or capacitors as well to upgrade.
Thanks!
-David
dw8083 said:
I have asked a similar wire question somewhere, and from responces I understand the following:
Small guages rule out stranded, so solid only (probably will sound a little better too). Pure silver is great and will give a colder/brighter/more analytical sound, while copper and gold are on the worm side. I do not have tests to prove anything, but my guess is that the coldness of silver will complement the overall wormness of PASS designs... It should be a nice balance. The guage, contrary to my intuitions, should be as small as possible, but not so small that you are using jewler's tools to solder a piece of wire
. To me that means not the smallest available, but defenantly not the thickest. As far as insulation, many prefer bare wire. Teflon, I guess, would be the next best thing. To me, a little extra insulation can not hurt, and will probably keep me from frying a part or two. I have not looked too much, but the source that I have found so far is:http://www.a-msystems.com/physiology/wirerod/silvertef.aspx
Hope this helps.
kevyjo said:
No, using 500VA, even 1000VA for the correct voltage ratings would not fry the parts. Toroid transformer is just a voltage source. An ideal voltage source will provide a constant voltage regardless of the load impedance. So, assuming you are using 100VAC from the transformer secondary tap, with 10 Ohm load, then the current passing the load will be 100VAC/10 Ohm = 10A (AC)
Variac said:
I think the correct terminology for huge transformers is not "force too much power into the circuit", but as you said, bigger transformers have a good regulating factor. In plain english, it goes like this: the bigger (VA ratings) the transformer, the secondary voltage will tend to output the same (not changing) voltage over a wide range of load impedance.
So, I think there is no need to compensate the power that goes into the circuit. The power that goes into the circuit will only depend on the trafo (secondary tap) load and the output voltage of the trafo (sencondary).
What you need to anticipate though, is the voltage drop at the rectifier (diodes, filters, etc) and how much the DC voltage (after the rectification) will drop due to the load impedance and/or the regulating FET.
So the question:
Does the 55VAC secondary voltage will do the job? I think so.
Here's the reasoning:
Supposed that you use MUR860 as your diodes (high speed, soft recovery diodes) for the bridge rectifier. The max forward voltage drop is 1.5V. For half cycle, the current will pass 2 diodes, so the Voltage drop at diodes (Vdd) = 2 x 1.5V = 3V.
VDC (after rectification) = 1.41 x (55V - Vdd) = 73.32 Volt.
So, in our Bosoz, we have a margin of 73.32 - (7 x 9.1V, zenner drops) = 9.62 Vdc, which will be dropped at the FET acting as regulator.
For the preamp, I got the feeling that 1 big trafo is better than 2 medium size trafo. Using 2 trafo will create EM radiation affecting each trafos. But again, this subject is a never ending discussion. I guess you better try both and listen. In my case, WAF plays an important consideration, so I cannot try both
Hope this helps,
OK I think there is still some confusion.
Here is a quote are from Nelson Pass's instructions: "Because the voltages required by this project are higher than delivered by off the shelf transformers, I have chosen to use two transformers T101 and T 102 with secondary circuits in series...."
So the point is that Mr. Pass would be happy to run both channels together off of one transformer, but he couldn't find a small one that put out 60 volts on each leg of the supply so he puts two 30 volt transformer outputs in series to create 60 volts.
BUT, what we figured out was that if you buy a large transformer, they DO come in 60 watt + and 60 watt - configuration. AND it's often cheaper to get a single large transformer than two smaller ones.
Then I mentioned that a possible problem with the oversized transformer is that because it is under such a relatively small load, the voltage doesn't drop as much as it would with smaller transformers. A possible alternate explanation is that Plitron are pretty high quality so they don't drop their voltage much under load. Someone on this forum mentioned that he got a big Plitron and the volts ended up a little bit too high, so I thought I'd pass this warning along.
Plitron just raised their prices, so there are probably better deals out there. An Avel or Toroid or Victoria Magnetics with two 60v
outputs will work fine.
NOW: another subject:
If you make the supply with two transformers as Nelson mentions, AND you want a separate supply for each channel, THEN you WOULD end up buying 4 transformers. IF you do as I suggest and get a transformers with two 60 volt outputs then you need two transformers total- one for each channel power supply.
Whew, I need a beer....
Here is a quote are from Nelson Pass's instructions: "Because the voltages required by this project are higher than delivered by off the shelf transformers, I have chosen to use two transformers T101 and T 102 with secondary circuits in series...."
So the point is that Mr. Pass would be happy to run both channels together off of one transformer, but he couldn't find a small one that put out 60 volts on each leg of the supply so he puts two 30 volt transformer outputs in series to create 60 volts.
BUT, what we figured out was that if you buy a large transformer, they DO come in 60 watt + and 60 watt - configuration. AND it's often cheaper to get a single large transformer than two smaller ones.
Then I mentioned that a possible problem with the oversized transformer is that because it is under such a relatively small load, the voltage doesn't drop as much as it would with smaller transformers. A possible alternate explanation is that Plitron are pretty high quality so they don't drop their voltage much under load. Someone on this forum mentioned that he got a big Plitron and the volts ended up a little bit too high, so I thought I'd pass this warning along.
Plitron just raised their prices, so there are probably better deals out there. An Avel or Toroid or Victoria Magnetics with two 60v
outputs will work fine.
NOW: another subject:
If you make the supply with two transformers as Nelson mentions, AND you want a separate supply for each channel, THEN you WOULD end up buying 4 transformers. IF you do as I suggest and get a transformers with two 60 volt outputs then you need two transformers total- one for each channel power supply.
Whew, I need a beer....
The quality of the Plitron product is appreciated for its
mechanical quietness under the increasingly difficult
conditions that AC line sources offer. This makes them
more expensive.
Other brands of transformer deliver power very nicely, and the
reason that Plitron is used is that we find customers who
complain if they can hear anything when they put their
ear on the amplifier.
If you can put up with a little bit of mechanical hum under full
power conditions, then save yourself some money and don't
worry about it.
mechanical quietness under the increasingly difficult
conditions that AC line sources offer. This makes them
more expensive.
Other brands of transformer deliver power very nicely, and the
reason that Plitron is used is that we find customers who
complain if they can hear anything when they put their
ear on the amplifier.
If you can put up with a little bit of mechanical hum under full
power conditions, then save yourself some money and don't
worry about it.
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