Differences?
MPSW's easier to find right now except at OnSemi.
Found MPSA 42/92 at: http://www.newark.com/
Mostly not much difference in cost.
Prosit
MPSW's easier to find right now except at OnSemi.
Found MPSA 42/92 at: http://www.newark.com/
Mostly not much difference in cost.
Prosit
acenovelty said:Differences?
MPSW's easier to find right now except at OnSemi.
Found MPSA 42/92 at: http://www.newark.com/
Mostly not much difference in cost.
Prosit
As I said, I ordered 50 pairs, if anyone interested, send me a self addressed envelope, I can send 2 pairs to you. Limit to first ten senders. ;-)
I have several Shielded/ potted Toroids from Adcom's 555II/ These can be wired primaries in series to get 30-0-30 vac on my home AC line of 124vac, on normal lines it will do 28-0-28 or so. Each one is 700VA. They are all prepped, i.e. Clips etc.
4 of these = 2.8kVA. You will get DC rails of about 39vdc to 42vdc depending on your home AC line. They are VERY quiet and painted black.
If interested let me know... PS, I wont let them go as cheaply as Steve.
One TO3 and 1 2SA1302 on top for scale.
4 of these = 2.8kVA. You will get DC rails of about 39vdc to 42vdc depending on your home AC line. They are VERY quiet and painted black.
If interested let me know... PS, I wont let them go as cheaply as Steve.
One TO3 and 1 2SA1302 on top for scale.
Attachments
You can get all transistors for digikey except the 2SA970, 2SC2240 and 2SC3955.
I got them at a very good prices from:
http://www.electronicsic.com/Default.htm
They accept PayPal. Great store and fast shipping. Recommended.
I got them at a very good prices from:
http://www.electronicsic.com/Default.htm
They accept PayPal. Great store and fast shipping. Recommended.
K-amps said:
Actually Steve said his had dual inputs too! I never thought of putting them in series! That would produce roughly 18-20 VAC on my 117VAC and would produce 25 - 28 VDC rails!!
Are 25 VDC rails too low for this amp? I don't need 50 WPC @ class A, I will be happy with > 25WPC class A into 8 Ohms.
K-Amps-
You said let you know, but you have email turned off on this forum...
25v rails...
If the 25 volts is under load or rock solid, 25 watts is no problem, 30+ is possible, so it really depends on the regulation of the transformer, or how it was rated...you only need 20v peak to get to 25w RMS.
As an example, the Passlabs aleph3 and 30, each with 25v rails, were rated 30w/8ohm, class A. The transformer was used at ~30% of it's nominal capacity, which gave great regulation, plus 120,000uF (or 60,000uF, depending on where you look) helped.
Using bipolar outputs instead of hexfets should also allow the krells to get a little closer to the rail before clipping, so you may do better using the same power supply.
Stuart
If the 25 volts is under load or rock solid, 25 watts is no problem, 30+ is possible, so it really depends on the regulation of the transformer, or how it was rated...you only need 20v peak to get to 25w RMS.
As an example, the Passlabs aleph3 and 30, each with 25v rails, were rated 30w/8ohm, class A. The transformer was used at ~30% of it's nominal capacity, which gave great regulation, plus 120,000uF (or 60,000uF, depending on where you look) helped.
Using bipolar outputs instead of hexfets should also allow the krells to get a little closer to the rail before clipping, so you may do better using the same power supply.
Stuart
transformers...
Just a quick comment regarding those adcom transformers, they are very nice pieces of equipment, I've used a few from amps that I didn't want to repair, and as mentioned they are completely silent, and shielded as well...
But, and it's a big but, if you put the primaries in series, you will get half the secondary voltage as expected, but you can't get twice the current. Using a 700va transformer this way effectively reduces its rating, a lot, down to 350-400va. Doubling the output current quadruples the internal losses, the extra heat this implies makes the transformer even hotter, which increases the basic copper losses further. A 700va transformer that normally generates +/-70v rails is good for ~5amps from the secondary. I think the nominal 5 or 6 amps is important to the safety and longevity of the amp...flames are bad...In a class A amp, the current being drawn continuously will cook an 'underrated' transformer. Using one of these for a pair of 2.2amp channels is as far as I would go, and I think high end manufacturers would probably use one per channel to get better regulation, and safety margins.
Stuart
Just a quick comment regarding those adcom transformers, they are very nice pieces of equipment, I've used a few from amps that I didn't want to repair, and as mentioned they are completely silent, and shielded as well...
But, and it's a big but, if you put the primaries in series, you will get half the secondary voltage as expected, but you can't get twice the current. Using a 700va transformer this way effectively reduces its rating, a lot, down to 350-400va. Doubling the output current quadruples the internal losses, the extra heat this implies makes the transformer even hotter, which increases the basic copper losses further. A 700va transformer that normally generates +/-70v rails is good for ~5amps from the secondary. I think the nominal 5 or 6 amps is important to the safety and longevity of the amp...flames are bad...In a class A amp, the current being drawn continuously will cook an 'underrated' transformer. Using one of these for a pair of 2.2amp channels is as far as I would go, and I think high end manufacturers would probably use one per channel to get better regulation, and safety margins.
Stuart
First thanks K and Stuart for the time and explanation.
The toroids Steve has are rated for 16 amps on the secondary.
If I series the inputs it will reduce the secondary from 35 V @ 16 amps to 18 V @ 8 amps.
The toroids are single secondary so I would require 2 toroids for a +/- 25 VDC supply with a current capacity of 8 amps.
I have 5 x 12k uF (60k total) for each rail and I am contemplating Steve's 8mH chokes that are rated for 16 amps to drop in between some of the caps. Two in front of the coils, 3 after.
The toroids Steve has are rated for 16 amps on the secondary.
If I series the inputs it will reduce the secondary from 35 V @ 16 amps to 18 V @ 8 amps.
The toroids are single secondary so I would require 2 toroids for a +/- 25 VDC supply with a current capacity of 8 amps.
I have 5 x 12k uF (60k total) for each rail and I am contemplating Steve's 8mH chokes that are rated for 16 amps to drop in between some of the caps. Two in front of the coils, 3 after.
not quite...
Troy,
If you series the primaries to make the secondary voltage half of the parallel rating, you can still pull the *same* current from the secondaries, so you would still be able to use the full 16amps, but not 32amps, so the rating of the transformer has effectively been halved. In fact you can probably pull more current, but the losses in the transformer increase at a little more than the square of the current, so you have to be careful, especially if it's gonna run at high current levels all the time.
A couple of the transformers I have are protected by embedded 75c cutouts in the primary, so I assume somewhere below this temp is considered 'safe'. If you have the means, you might try a load test and monitor the temp to see where your limits are...
Stuart
Troy,
If you series the primaries to make the secondary voltage half of the parallel rating, you can still pull the *same* current from the secondaries, so you would still be able to use the full 16amps, but not 32amps, so the rating of the transformer has effectively been halved. In fact you can probably pull more current, but the losses in the transformer increase at a little more than the square of the current, so you have to be careful, especially if it's gonna run at high current levels all the time.
A couple of the transformers I have are protected by embedded 75c cutouts in the primary, so I assume somewhere below this temp is considered 'safe'. If you have the means, you might try a load test and monitor the temp to see where your limits are...
Stuart
Not only Mouser. Digikey shows zip, Newark wants 10 days lead time.
Made by http://www.mcmelectronics.com/
specs:
Toshiba Transistor, Voltage: 120 V, Current: 50 mA, Power: .3 W, Frequency: 100 MHz
1465 available
$.27 ea.
How about the 2N5401/2N5551 or the 2N6515/2N6520 as reasonable replacements? Higher voltages. No problem?
About $.21 ea. at DigiKey
Prosit
Made by http://www.mcmelectronics.com/
specs:
Toshiba Transistor, Voltage: 120 V, Current: 50 mA, Power: .3 W, Frequency: 100 MHz
1465 available
$.27 ea.
How about the 2N5401/2N5551 or the 2N6515/2N6520 as reasonable replacements? Higher voltages. No problem?
About $.21 ea. at DigiKey
Prosit
acenovelty said:Not only Mouser. Digikey shows zip, Newark wants 10 days lead time.
Made by http://www.mcmelectronics.com/
specs:
Toshiba Transistor, Voltage: 120 V, Current: 50 mA, Power: .3 W, Frequency: 100 MHz
1465 available
$.27 ea.
How about the 2N5401/2N5551 or the 2N6515/2N6520 as reasonable replacements? Higher voltages. No problem?
About $.21 ea. at DigiKey
Prosit
IMHO higher voltage devices sound hard and have glare... generally.
http://www.mcmelectronics.com/
has 1,465 2sc2240's available.
Suit yourself. Already got my parts to make the original version.
Prosit
has 1,465 2sc2240's available.
Suit yourself. Already got my parts to make the original version.
Prosit
Re: transformers...
So Stuart,
1) knowing these are protected by thermal breakers, would one of these per channel be ok for the Krell clone? i.e. two in total for stereo? (Knowing they are peak rated for 1440VA per Adcom?
2) Second question, since the size of the core has not reduced, would the toroid still provide 700 to 1440 on a peak basis (and lower on continuous)?
3) So for a given 8 ohm speaker load in the case of the Krell, the Toroid would be subjected to about 200 watts continuous and 50 to 200 on a dynamic basis, surly unless 1 ohm loads are used, these toroids shold be well enough... right?
Stuart Easson said:
So Stuart,
1) knowing these are protected by thermal breakers, would one of these per channel be ok for the Krell clone? i.e. two in total for stereo? (Knowing they are peak rated for 1440VA per Adcom?
2) Second question, since the size of the core has not reduced, would the toroid still provide 700 to 1440 on a peak basis (and lower on continuous)?
3) So for a given 8 ohm speaker load in the case of the Krell, the Toroid would be subjected to about 200 watts continuous and 50 to 200 on a dynamic basis, surly unless 1 ohm loads are used, these toroids shold be well enough... right?
Absolutely
I think one of these should work fine for two channels, especially if 1 ohms loads are not really on the agenda. After all if they are originally 1440va, even conservatively rated at 720va they still have margin. At a constant draw of 4.4 amps, they are well within their original rating, and still under 720.
The sheer size and weight of the transformers, and thereby thermal inertia and dissipation, means their continuous and peak capabilities will be larger than a normal 720va device.
If the thermal cutout is functional, I'd test one of them at the theoretical 40% increase in current that would double the internal losses, measure the temperature over an hour or so every couple of minutes using a digital kitchen thermometer. You'll lose a volt or two, but my guess would be it'll work fine, and more current is good for krells.
I've been beating on some 500va transformers, rated at 5.5amps. They hum at that level, and over the course of an hour are about 10c above ambient. I've pulled the transformer from a 555, it's a much nicer, bigger unit, they'll do a ksa50 no problem, I'd be more concerned about testing them before using them for both channels of a ksa100...
Stuart
I think one of these should work fine for two channels, especially if 1 ohms loads are not really on the agenda. After all if they are originally 1440va, even conservatively rated at 720va they still have margin. At a constant draw of 4.4 amps, they are well within their original rating, and still under 720.
The sheer size and weight of the transformers, and thereby thermal inertia and dissipation, means their continuous and peak capabilities will be larger than a normal 720va device.
If the thermal cutout is functional, I'd test one of them at the theoretical 40% increase in current that would double the internal losses, measure the temperature over an hour or so every couple of minutes using a digital kitchen thermometer. You'll lose a volt or two, but my guess would be it'll work fine, and more current is good for krells.
I've been beating on some 500va transformers, rated at 5.5amps. They hum at that level, and over the course of an hour are about 10c above ambient. I've pulled the transformer from a 555, it's a much nicer, bigger unit, they'll do a ksa50 no problem, I'd be more concerned about testing them before using them for both channels of a ksa100...
Stuart