Spurite
Do a search.. What you have is seperate bridges for each side +an -. Do a search on the Aragon amps as I recall they used them
CL 60's can be found at Mouser/Digikey
Side note
On my 100,s, I used .47 ohm er's instead of 1 ohm. The factory used 1 ohm to cover themselves and eliminate current hogging even though they pulled them from the same date codes. I seriously doubt they matched every TO3.
I had good matching of the TO3's with the resultant change in bias levels. I might reduce this even more but it ,s been running fine now going on almost 3 years without a hiccup.
Took a long time to break in,about 80 hours before it opened up completely
Regards
David
Do a search.. What you have is seperate bridges for each side +an -. Do a search on the Aragon amps as I recall they used them
CL 60's can be found at Mouser/Digikey
Side note
On my 100,s, I used .47 ohm er's instead of 1 ohm. The factory used 1 ohm to cover themselves and eliminate current hogging even though they pulled them from the same date codes. I seriously doubt they matched every TO3.
I had good matching of the TO3's with the resultant change in bias levels. I might reduce this even more but it ,s been running fine now going on almost 3 years without a hiccup.
Took a long time to break in,about 80 hours before it opened up completely
Regards
David
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Possible misprint
Were you aware that there is some questions when comparing the schematic to Jim's Audio PCBs with the resistors above 2SA9 and diode 1N4754A. That the resistors should be both 4.7k, not 47k and 20k.
Were you aware that there is some questions when comparing the schematic to Jim's Audio PCBs with the resistors above 2SA9 and diode 1N4754A. That the resistors should be both 4.7k, not 47k and 20k.
Reading some older stuff, I ran into DIYCable.com where they sell toroidal transformer 115v X 40V @ 12VA for a current price of $65.00 (pricing in 2008 was around $125.00). Anything on this? Plus, they have Panasonic TSHA 10,000uF, 63VDC, 105c Temperature with 10mm lead spacing and 3.5mmx50mm can size for $10.47. They use these components for their own Power Supply. DIYCable.com : Intro » Home » Exodus/Hypex Amps » Amp Parts »
That's a very nice transformer at a great price.
However, after rectification and smoothing the 40v secondary is going to give you 55v rails...if you still intend to bias for 4ohm Class A, you are going to be generating more heat.
The flipside is you could keep the bias low and have far more peak power...
If you are really shooting for 100W into 8 ohms, you only need ~30V secondaries, perhaps 33 to be safe (you'd need to know the the 'sag' the transformer experiences under load to calculate this more precisely)...This should give you ~45v rails, and then you can use 50v caps, which will be smaller or cheaper or both.
If you haven't done so I'd recommend starting figuring out heat-sinks...with 2.5A and 55v rails it's going to be a bigger challenge. I can help with what I know (pretty much all learned here), but in any case I wouldn't assume this is 'no problem'.
Stuart
However, after rectification and smoothing the 40v secondary is going to give you 55v rails...if you still intend to bias for 4ohm Class A, you are going to be generating more heat.
The flipside is you could keep the bias low and have far more peak power...
If you are really shooting for 100W into 8 ohms, you only need ~30V secondaries, perhaps 33 to be safe (you'd need to know the the 'sag' the transformer experiences under load to calculate this more precisely)...This should give you ~45v rails, and then you can use 50v caps, which will be smaller or cheaper or both.
If you haven't done so I'd recommend starting figuring out heat-sinks...with 2.5A and 55v rails it's going to be a bigger challenge. I can help with what I know (pretty much all learned here), but in any case I wouldn't assume this is 'no problem'.
Stuart
1N5309
AMERICAN POWER DEVICES|1N5309|CURRENT REGULATOR DIODE, 600mW | Newark.com
I found 1N5309s at this this site, but it's in the U.S. and they are not cheap --
AMERICAN POWER DEVICES|1N5309|CURRENT REGULATOR DIODE, 600mW | Newark.com
I found this at another Krell KSA 100 thread (although the schematic is from 11/2004) and it shows a power supply 41V seconary for 52VDC rails. http://www.diyaudio.com/forums/atta...l-transformer-europe-gb-ksa100mk-ii-power.pdf
I correct? At the same time, I've found other posts where others have gone down to 27V secondary to control the heat issue. So the 33Volts you advise seems a good compromise. I will start to look for the heat-sinks ASAP.
Spurlte, I am working on the same project. I bought xslavics boards, I also got the 40v transformers. But have 75lbs of heat sink for monoblocks to dissapate heat. I bought them at a wholesale/retial metal distributer. Maybe you have one in you area. I paid 3.80 a pound. That is how they sale, copper was close to 14 a pound. But from what I have read. Heat sink, Heat sink and Heat sink some more. I want the extra head room becuase I am driving 3.8ohm load multi-way speakers. I hope this amp does the trick, these speakers are hungry, they never seem to have enough power. hmm
Instead of 1n5309 for current source you can use LM334 and 22 ohm resistor (look at the PCB). It will give you the same 3mA current and it's much cheaper.
Toroidal Trans
Antek - AN-15432
Please, if you have a chance, review this toroidal 2x32v/23.4A, 18V/2A, 12V/2A, 1500VA transformer and please check out the PDF specification sheet at this ANTEC website. Priced at $155.00 ---
Antek - AN-15432
SST03 Softstart for toroid transformers
Stuart What do you think of this soft start. I am building mono blocks and running a smaller 100va transformer to power the 62v dc for the boards, I got some high voltage pcb boards for that supply but was going to use the soft start and just a rectifier for the out put supply which is a 1000va transformer and two 56000uf 100v cans. I am doing the best I can to put things together, so a little in the dark, but trucking along. Would greatly appreciate your thoughts. Thanks
Stuart What do you think of this soft start. I am building mono blocks and running a smaller 100va transformer to power the 62v dc for the boards, I got some high voltage pcb boards for that supply but was going to use the soft start and just a rectifier for the out put supply which is a 1000va transformer and two 56000uf 100v cans. I am doing the best I can to put things together, so a little in the dark, but trucking along. Would greatly appreciate your thoughts. Thanks
Chris,
As far as I can tell from the schematic and description, this will do just what you need. It is also a high capacity power switch, which is a useful function to have in it's own right.
I'm a klutz and have a natural aversion to circuits where everything is live, and this one falls into that category, but he goes to some lengths to warn users, so just be careful. A more important concern is his choice of relay, he used considerably smaller transformers than you with twice the supply voltage (240v) so for him the relays are overrated by a factor of ~3...I'd argue the relay is not big enough for your transformer on 110v. He also mentions he has not properly tested one particular, very important, capacitor for 110v, not surprising since he has 240v, but again, you need to be careful.
62v for the front end boards is quite high, but it will remove any chance of the input stages clipping before the output. Make sure you have big enough heat-sinks for the driver transistors, they are basically working pretty hard, and need to be kept in class A in their own right. My experience is that the driver transistors running in class A is at least as important for overall quality (if not more so) than the output stage.
We ended up using a toroid, rectifier and caps for the entire amp, and as mentioned we went with a pair of CL60 to perform softstart duties. We used an output protector circuit, so the output is not connected to the speakers for about 3 seconds after the power is applied, and it also checks for DC offset. We also added an 85c overheat cutoff. Over the course of a couple of weeks we accidentally tested every 'safety' feature of the amp...oops. Luckily everything worked and survived.
Good luck
Stuart
As far as I can tell from the schematic and description, this will do just what you need. It is also a high capacity power switch, which is a useful function to have in it's own right.
I'm a klutz and have a natural aversion to circuits where everything is live, and this one falls into that category, but he goes to some lengths to warn users, so just be careful. A more important concern is his choice of relay, he used considerably smaller transformers than you with twice the supply voltage (240v) so for him the relays are overrated by a factor of ~3...I'd argue the relay is not big enough for your transformer on 110v. He also mentions he has not properly tested one particular, very important, capacitor for 110v, not surprising since he has 240v, but again, you need to be careful.
62v for the front end boards is quite high, but it will remove any chance of the input stages clipping before the output. Make sure you have big enough heat-sinks for the driver transistors, they are basically working pretty hard, and need to be kept in class A in their own right. My experience is that the driver transistors running in class A is at least as important for overall quality (if not more so) than the output stage.
We ended up using a toroid, rectifier and caps for the entire amp, and as mentioned we went with a pair of CL60 to perform softstart duties. We used an output protector circuit, so the output is not connected to the speakers for about 3 seconds after the power is applied, and it also checks for DC offset. We also added an 85c overheat cutoff. Over the course of a couple of weeks we accidentally tested every 'safety' feature of the amp...oops. Luckily everything worked and survived.
Good luck
Stuart
Stuart
OK. I have come around to your thinking about the heat problems with higher voltages. Especially with the weight of the heatsinks. I am willing to back off, either to a 30V at 800VA or a 32V at 600VA (no 800VA for 32V through Antec.com), for the KSA100. One for each channel. Also, the 30V comes with or without extra secondaries, 12v and 18v, both at 2A. Will soft-starts, fans and/or speaker-protection demand this high of an amperage? Or is it better to get the trannies without the extra secondaries and get smaller trannies for these other components? There is also a 35V @ 1000VA (14.8A) with four 35V secondaries--two for each channel, weighing in at 18 pounds. This way I can get one transformer for both channels but at only 500VA per channel. At 35V, ~48V at the rails, I can picture your forhead and eyebrows raised and might reason, "I have to admit it can get quite cold in Chicago."
Thanks Stuart, did you guy's use the protection circut from the original schematics, or a modified. I don't remember anything from Marks thred. Do you thinks I should go with 10amp relay's or just try stuff out. I have emailed sjostrom about my concerns with the differences, he just stated to stick with the 110 version schematics he posted. I already bought all the resistors for the boards and some of the diodes, My little surplus store did not have everything. I held off on the relay's for the reasons you mentioned. I think I should at the very least go with the higher amperage relay's. But I want to get the boards in first. I imagine that shipping should take a couple of weeks from last friday. Thanks for your input.
spurlte, If you are making a single chassis for both channels, the 1KVA/35v x 4 would be a fine main power transformer. I used a separate small 6VA/12v transformer for control circuits, since you need power to be applied without softstart for control purposes.
Chris, we used a little board much like the connex one, actually supplied as a kit. I don't think I found that board when I was looking a couple of years ago, but it seems perfect. The one I used was similar but used discrete transistors instead of a control IC. Obviously the relay is the big deal, since it is directly in line with the output, and Doug Self has documented that relays with steel frames that are in the circuit add measurable amounts of distortion. Ours, like the one you show here, does not include the frame in the circuit.
Stuart
Chris, we used a little board much like the connex one, actually supplied as a kit. I don't think I found that board when I was looking a couple of years ago, but it seems perfect. The one I used was similar but used discrete transistors instead of a control IC. Obviously the relay is the big deal, since it is directly in line with the output, and Doug Self has documented that relays with steel frames that are in the circuit add measurable amounts of distortion. Ours, like the one you show here, does not include the frame in the circuit.
Stuart
Notice that the relay doesn't switch off at full current unless for very rare occasions. Through reports it works good with 110-120 VAC.