Hi Andrew,
Thanks for the reply. The capacitance multiplier seems like such a novel solution to me that I am very tempted to try it here. Hum does appear to be a problem - or at least something people are trying to improve on as the Krell-o-Tracker shows a lot of people cranking up capacitance or even using inductors. I have very efficient speakers and I'd like to avoid hum as much as possible.
If I use the capacitance multiplier, I will be able to get KSA-50 rail voltages from a 39-0-39 transformer. If remove the multiplier and use an unregulated high capacitance supply, I will have almost KSA-100 rail voltages, but according to my results with the Class A spreadsheet, this will only increase idle dissipation and probably render my heatsink insufficient and my listening area very warm. I suspect moving to an unregulated supply after the fact will mean a whole new transformer to avoid dissipating an extra 60-70 watts per channel. In light of this I'd like to use the multiplier but add a large capacitance on its output - to give back some of the reserve it would have access to in the unregulated supply. Is there any reason not to put large capacitance after the multiplier? There will already be plenty of capacitance before the multiplier.
If I give the input stage a separate power supply, should it have higher or equal supply voltage relative to the output stage? Also, will I encounter problems running two pairs of output devices from one driver, and three from the other driver for a simultaneous five pairs?
Thanks for the reply. The capacitance multiplier seems like such a novel solution to me that I am very tempted to try it here. Hum does appear to be a problem - or at least something people are trying to improve on as the Krell-o-Tracker shows a lot of people cranking up capacitance or even using inductors. I have very efficient speakers and I'd like to avoid hum as much as possible.
If I use the capacitance multiplier, I will be able to get KSA-50 rail voltages from a 39-0-39 transformer. If remove the multiplier and use an unregulated high capacitance supply, I will have almost KSA-100 rail voltages, but according to my results with the Class A spreadsheet, this will only increase idle dissipation and probably render my heatsink insufficient and my listening area very warm. I suspect moving to an unregulated supply after the fact will mean a whole new transformer to avoid dissipating an extra 60-70 watts per channel. In light of this I'd like to use the multiplier but add a large capacitance on its output - to give back some of the reserve it would have access to in the unregulated supply. Is there any reason not to put large capacitance after the multiplier? There will already be plenty of capacitance before the multiplier.
If I give the input stage a separate power supply, should it have higher or equal supply voltage relative to the output stage? Also, will I encounter problems running two pairs of output devices from one driver, and three from the other driver for a simultaneous five pairs?
Most amps that I have seen that use seperate supplies use a larger voltage for the input stages. I believe for the extra head room.
However if you want a cheap solution but at a lower voltage than the output stage look at how Carlos designed the DX amp. He got better results by regulating the front end.
However if you want a cheap solution but at a lower voltage than the output stage look at how Carlos designed the DX amp. He got better results by regulating the front end.
Proper front-end regulation, even if just by a simple zener-follower without feedback, is still much better than using nothing or just a zener. I've described a few months ago a method of using a high-voltage opamp, a stable reference from TI's REFxxxx range and two OPA548's to create a simple yet very effective regulated front-end. It has enough power to even drive the drivers, but the front-end, LTP stage in particular, is the most important. I haven't tested it yet in a Krell, but on its own with a bad supply the regulation is superb. The other method described with the LM317/337 is also very good. If you only want to replace the critical LTP stage's zener you can sub-regulate from the main bus, although a separate supply is of course better.
The Krell KSA150 beast I have with me now has a massively verbose separate power supply for the front-end which surely must have counted as it takes up almost 1/3 of the entire chassis.
The Krell KSA150 beast I have with me now has a massively verbose separate power supply for the front-end which surely must have counted as it takes up almost 1/3 of the entire chassis.
jacco vermeulen said:
Actually, if memory serves me correctly, there are about 6 boards in my KSA250. I just have to figure out how to pull them and copy them. By the way, is that legal. I mean the amp is from the 90s, so.... are there any problems with that? Do I have to change them a little bit?
Well,
Most of my life I had been considered a 'pushover', or maybe a little too nice. But lately, I have grown tired of people that have nothing but excuses. Too often people simply do not do what they say they will do. This time it's thievery. It's only 50 bucks - but it's still thievery and I'm not gonna stand for it.
http://www.ic3.gov/
Anyone else?
Most of my life I had been considered a 'pushover', or maybe a little too nice. But lately, I have grown tired of people that have nothing but excuses. Too often people simply do not do what they say they will do. This time it's thievery. It's only 50 bucks - but it's still thievery and I'm not gonna stand for it.
http://www.ic3.gov/
Anyone else?
I doubt very much Mark is desiring to steal anything. If memory serves me correctly, he put his own money out for the boards in the first place. I think he just got completely overwhelmed by all of it. I have a couple of boards I will part with. I thought I would like to build this amp but I didn't realize at the time that I none of my heatsinks or transformers would be sufficient and I'm not in the position to lay out that kind of money right now. So, I paid $45 and shipping is probably $5 so if someone wants them for $50 just email me and I'll send you a PayPal invoice.
Note; When I got the boards, one of them had a small scratch on the back that had been repaired by whoever made the boards. (They had brushed on some of the masking over the scratch.) It doesn't affect anything other than the appearance and you have to look for it, but I wanted you to know it was there.
Blessings, Terry
Note; When I got the boards, one of them had a small scratch on the back that had been repaired by whoever made the boards. (They had brushed on some of the masking over the scratch.) It doesn't affect anything other than the appearance and you have to look for it, but I wanted you to know it was there.
Blessings, Terry
still4given said:
well - if memory serves me well - Mark participated in first batch more than satisfactory ; nobody denies amount of good will he put in all thing ;
but - job, marriage , and similar - everyday - things , primary subjective , can't be excuse ;
ppl sent money to him ;
ppl didn't received goods for what they payed .
fact is a fact ; nobody pushed him in that adventure
Mark is a cinema tech. I would assume the holidays (Nov- Jan) are the busiest time for him.
Job or hobby, I wonder which one pays his bills.
Very rarely do the people who complain about group buys ever host one. They let others do the work and just enjoy the benefits.
Mark has done several GB's and all were good until very recently. More than likely there is a reason and I'm sure he will make it good if he can, when he can.
I'm not being negative, I'm saying Marks reputation is good and I'm sure there is a reason for the delay. I don't think anyone is dying waiting for PCB's.
Job or hobby, I wonder which one pays his bills.
Very rarely do the people who complain about group buys ever host one. They let others do the work and just enjoy the benefits.
Mark has done several GB's and all were good until very recently. More than likely there is a reason and I'm sure he will make it good if he can, when he can.
I'm not being negative, I'm saying Marks reputation is good and I'm sure there is a reason for the delay. I don't think anyone is dying waiting for PCB's.
First, let me state that I've received everything I've ever ordered from Mark. (i.e. the 50 and 100 klone boards) For that matter, I've had mostly good luck with all my purchases through this forum. However ...
Having just found out that I'm part of another group buy that is on the brink of going south, perhaps we could create a thread, a 'sin bin' if you will, of less-than-expected service/value by folks in the DIY trade? This may be bad form ( but that's why the moderators get paid the big bucks, to make that call, right?) but it would/could save many of us some frustration and money. I'm still more frustrated by getting ripped off by a business like Welborne Labs (there's a thread in this forum on that) than I am by errant group buys. The money is painful either way.
Perhaps things like this particular GB.having started out fine, would get through the cracks, but at least folks could get put on notice.
Sorry, just my way of venting ...
Ryan
Having just found out that I'm part of another group buy that is on the brink of going south, perhaps we could create a thread, a 'sin bin' if you will, of less-than-expected service/value by folks in the DIY trade? This may be bad form ( but that's why the moderators get paid the big bucks, to make that call, right?) but it would/could save many of us some frustration and money. I'm still more frustrated by getting ripped off by a business like Welborne Labs (there's a thread in this forum on that) than I am by errant group buys. The money is painful either way.
Perhaps things like this particular GB.having started out fine, would get through the cracks, but at least folks could get put on notice.
Sorry, just my way of venting ...
Ryan
