Hi All-
I'm not a draftsman so I won't begin to try and draw the output boards.
But if we can make them the same length as the main board I can probably have them made with the main board as a "snap apart" piece for the same or very slightly more.
I will get price estimates this week on 25, 50 and 100 boards.
I'm not a draftsman so I won't begin to try and draw the output boards.
But if we can make them the same length as the main board I can probably have them made with the main board as a "snap apart" piece for the same or very slightly more.
I will get price estimates this week on 25, 50 and 100 boards.
Hi Jan-
How about something like this?
It is from the Pass forums but it may work for us too.
http://www.diyaudio.com/forums/attachment.php?s=&postid=10783&stamp=1008529779
This is the thread it was "borrowed" from..
http://www.diyaudio.com/forums/showthread.php?s=&threadid=1489
Now I'm not advocating the theft of their board... Just showing it as an example of what may work for this Clone also.
How about something like this?
It is from the Pass forums but it may work for us too.
http://www.diyaudio.com/forums/attachment.php?s=&postid=10783&stamp=1008529779
This is the thread it was "borrowed" from..
http://www.diyaudio.com/forums/showthread.php?s=&threadid=1489
Now I'm not advocating the theft of their board... Just showing it as an example of what may work for this Clone also.
Attachments
not quite...
With a capacitively loaded rectifier the DC rating of the transformer is approx 1.4 x the AC rating. To get 45-50 DC you need 30-32v AC, 50v ac will give you 73+v DC, and much bigger problems heatwise. And yes 1kva is a nice round number...I'm probably going to use a pair of 600va toroids I've already got, 1 per channel. 45v is nice, lets you use 50v caps safely, and coincidentally I have literally hundreds of nice little 50v/4700u snap ins....and a couple of cases of 66000u/50v cans.
The amp will be quite heavy by the time you are done...like 50+lbs per pair of channels. I think it was Nelson Pass said you should get approx. 1# of amp per watt...seems like we should be able to make those numbers...
Stuart
With a capacitively loaded rectifier the DC rating of the transformer is approx 1.4 x the AC rating. To get 45-50 DC you need 30-32v AC, 50v ac will give you 73+v DC, and much bigger problems heatwise. And yes 1kva is a nice round number...I'm probably going to use a pair of 600va toroids I've already got, 1 per channel. 45v is nice, lets you use 50v caps safely, and coincidentally I have literally hundreds of nice little 50v/4700u snap ins....and a couple of cases of 66000u/50v cans.
The amp will be quite heavy by the time you are done...like 50+lbs per pair of channels. I think it was Nelson Pass said you should get approx. 1# of amp per watt...seems like we should be able to make those numbers...
Stuart
Balanced in?
If you want to change the input to another front end that is fine. But the circuit is being built as a clone, so single-ended it is for now. Major changes to the circuit were discussed and nixed early into this.
Changing the circuitry around for a differential input should not be too difficult, the dual rail supply will make it fairly easy.
One thought, if you have a balanced source, consider using an input transformer to convert from balanced to single ended. Many people swear by using transformers to couple.
In fact I plan on trying it in my Krell Clone when built to check the results. I have them on the input of my linestage now, but have not decided if they will stay. So far the results are not as expected.
George
Repute said:
If you want to change the input to another front end that is fine. But the circuit is being built as a clone, so single-ended it is for now. Major changes to the circuit were discussed and nixed early into this.
Changing the circuitry around for a differential input should not be too difficult, the dual rail supply will make it fairly easy.
One thought, if you have a balanced source, consider using an input transformer to convert from balanced to single ended. Many people swear by using transformers to couple.
In fact I plan on trying it in my Krell Clone when built to check the results. I have them on the input of my linestage now, but have not decided if they will stay. So far the results are not as expected.
George
Re: not quite...
Output voltage (for me) is no problem, moreso the heat that we have to dissapate!!! Do you suggest any higher than 30-0-30? Not sure if they are made, but 35-0-35? or 40-0-40? I definately don't want 73+vdc on the rails!!! However i was interested if people knew the output of the original Krell transformer? I'd like to keep this as original as possible!
Thanks
Aaron
Stuart Easson said:
Output voltage (for me) is no problem, moreso the heat that we have to dissapate!!! Do you suggest any higher than 30-0-30? Not sure if they are made, but 35-0-35? or 40-0-40? I definately don't want 73+vdc on the rails!!! However i was interested if people knew the output of the original Krell transformer? I'd like to keep this as original as possible!
Thanks
Aaron
good question...
Aaron,
If your goal is to keep it stock, you are gonna end up with rails a bit less than 50v, after all the amp was only rated at 50w into 8ohms. It was a total over achiever... Lets see 50v with minimal sag, deduct a few volts for emitter resistors, transistor saturation and you still get, say 45 volts peak into 8, this is still over 120w RMS... not bad for a 50w amp. IMHO there's no way Krell would use more volts unnecesarily when what they were known for was more amps.
To make 50w into 8 ohms only needs 20v RMS, about 29 peak, so adding another 16v for supply sag is being quite generous...they make the KSA100 for more than that.
I bet if someone has one and can measure it the ac voltage is less than 30...
Stuart
Aaron,
If your goal is to keep it stock, you are gonna end up with rails a bit less than 50v, after all the amp was only rated at 50w into 8ohms. It was a total over achiever... Lets see 50v with minimal sag, deduct a few volts for emitter resistors, transistor saturation and you still get, say 45 volts peak into 8, this is still over 120w RMS... not bad for a 50w amp. IMHO there's no way Krell would use more volts unnecesarily when what they were known for was more amps.
To make 50w into 8 ohms only needs 20v RMS, about 29 peak, so adding another 16v for supply sag is being quite generous...they make the KSA100 for more than that.
I bet if someone has one and can measure it the ac voltage is less than 30...
Stuart
Re: good question...
I do not know if it will work, but I would like to try 25 volt rails. This will have a lot more power than I need. The dual rail power supply will give the 50 volts required.
I cannot imagine that a limited voltage swing, almost unlimited current swing amp has high voltage rails. Seems it would go up in smoke with +/- 50 volt rails.
Stuart Easson said:
I do not know if it will work, but I would like to try 25 volt rails. This will have a lot more power than I need. The dual rail power supply will give the 50 volts required.
I cannot imagine that a limited voltage swing, almost unlimited current swing amp has high voltage rails. Seems it would go up in smoke with +/- 50 volt rails.
careful now...
the choice of output transistors is a somewhat sensitive subject, close to religion or politics...
The schematics I have show mj15003/4 pairs, and the era of the amp would have made these an obvious good choice. I plan on using them simply because they are very reliable, easily available, and not too expensive. The fact that they are relatively low bandwidth and so on didn't bother Dan, not sure why it should bother me...personally I hate drilling to3 mounts, I always seem to screw the last one up...
Stuart
the choice of output transistors is a somewhat sensitive subject, close to religion or politics...
The schematics I have show mj15003/4 pairs, and the era of the amp would have made these an obvious good choice. I plan on using them simply because they are very reliable, easily available, and not too expensive. The fact that they are relatively low bandwidth and so on didn't bother Dan, not sure why it should bother me...personally I hate drilling to3 mounts, I always seem to screw the last one up...
Stuart
Re: careful now...
That's the problem i usually have, so i'm going to invest in a drill press
(we are making 2 4 channel versions!)
We've decided 800va (each channel, so 4 per unit) should be about right for our needs, so that should be fine, plenty of amperage and voltage!
Aaron
Stuart Easson said:
That's the problem i usually have, so i'm going to invest in a drill press
(we are making 2 4 channel versions!)We've decided 800va (each channel, so 4 per unit) should be about right for our needs, so that should be fine, plenty of amperage and voltage!
Aaron
