Almost all amplifiers are 0degrees phase shift. across the audio band. A minority will have 180 shift, but few will have (mentionable) shift, and definitely not to affect a bi/triamped system where the shifts of the crossover and drivers are far more dominant. The few amps that has 180degrees shift can easily be compensated by wiring them out of phase. At very low frequencies the phase relationships may differ, but then the change of phase (i.e. group delay) of the preceding electronics and electro-mechanical effect of the driver in the box will dominate once more.
In short: don't worry about it. What IS an issue is the different gains of different amplifiers. Most are in the 20dB region, but there's no fixed gain for all amps. Even the Krells differ - the KSA50 has a 23.9dB gain, and the KSA100 28dB; i.e. 4dB higher. That should be compensated for (add/remove gain of one of the two before the amps, or pad the higher gain one if you know what you're doing, or design the crossover with the gain difference calculated in. The last option is the most elegant with no active circuitry or power loss, but naturally limit the speaker to the particular amp combo.
In short: don't worry about it. What IS an issue is the different gains of different amplifiers. Most are in the 20dB region, but there's no fixed gain for all amps. Even the Krells differ - the KSA50 has a 23.9dB gain, and the KSA100 28dB; i.e. 4dB higher. That should be compensated for (add/remove gain of one of the two before the amps, or pad the higher gain one if you know what you're doing, or design the crossover with the gain difference calculated in. The last option is the most elegant with no active circuitry or power loss, but naturally limit the speaker to the particular amp combo.
Hi Guys,
Sorry for the Faux pas. I must learn that I don't have to type everything I'm thinking. I surely didn't mean to take the thread off course. I am very interested in the KSA 100 and am looking forward to building one. I built two of the Ksa 50 klones, one with Jan's boards and T-03 outputs and one with the Pinkmouse boards and plastic outputs. I now plan to use the tunnel and outputs from the first unit for one side of the KSA 100. I'll try and keep on subject.
Blessings, Terry
Sorry for the Faux pas. I must learn that I don't have to type everything I'm thinking. I surely didn't mean to take the thread off course. I am very interested in the KSA 100 and am looking forward to building one. I built two of the Ksa 50 klones, one with Jan's boards and T-03 outputs and one with the Pinkmouse boards and plastic outputs. I now plan to use the tunnel and outputs from the first unit for one side of the KSA 100. I'll try and keep on subject.
Blessings, Terry
Hi Guys,
I want to start looking for components for this amp and just want to confirm some details here.
Am I correct in assuming that I can use MJL21193 + MJL21194's for the outputs transistors? Should I rather use MJ15003 + MJ15004? I'm thinking of using 4 pairs per channel. For the drivers, I can use MJ15030 + MJ15031 (It looks like that in the previously attached scematic). Do you guys have any idea what kind of heatsink I would need for a channel on this? I had a look what some of our eastern friends use on their amps. They appear to be using the Fischer SK108 or SK109 sinks. These are around $35 unanodised in 100mm lengths each and they use 7 of them for a complete amp. That is quite pricey for heatsinks!!! I don't like the idea of fans, but I might end up having to use them...
Any thoughts would be appreciated!
I want to start looking for components for this amp and just want to confirm some details here.
Am I correct in assuming that I can use MJL21193 + MJL21194's for the outputs transistors? Should I rather use MJ15003 + MJ15004? I'm thinking of using 4 pairs per channel. For the drivers, I can use MJ15030 + MJ15031 (It looks like that in the previously attached scematic). Do you guys have any idea what kind of heatsink I would need for a channel on this? I had a look what some of our eastern friends use on their amps. They appear to be using the Fischer SK108 or SK109 sinks. These are around $35 unanodised in 100mm lengths each and they use 7 of them for a complete amp. That is quite pricey for heatsinks!!! I don't like the idea of fans, but I might end up having to use them...
Any thoughts would be appreciated!
Hi,
building a ClassA amp from scratch is expensive.
Building a big one (KSA100) is much more expensive.
The cost of the "amplifier" is quite (very) small compared to the cost of the transformer + the smoothing capacitance + the case + the heatsinks.
If you want to save significant sums of money then try to source suitable components for the "big costs" secondhand. (I have used Ebay for this).
I would prefer to go with 21193/4 rather than 15003/4 due to the better SOA at the higher voltages found in the KSA100 (for a 50Klone either would do)
They are also more than twice as fast (with half the Cob) and Onsemi divulge more data and that reassures me. ONsemi seem almost secretive about 15003/4 data and that worries me, I begin to wonder what they are hiding.
building a ClassA amp from scratch is expensive.
Building a big one (KSA100) is much more expensive.
The cost of the "amplifier" is quite (very) small compared to the cost of the transformer + the smoothing capacitance + the case + the heatsinks.
If you want to save significant sums of money then try to source suitable components for the "big costs" secondhand. (I have used Ebay for this).
I would prefer to go with 21193/4 rather than 15003/4 due to the better SOA at the higher voltages found in the KSA100 (for a 50Klone either would do)
They are also more than twice as fast (with half the Cob) and Onsemi divulge more data and that reassures me. ONsemi seem almost secretive about 15003/4 data and that worries me, I begin to wonder what they are hiding.
Advantage of 15004/3 is their low fT and thus less chance for instability with long wires. The 21193/4 are slightly faster, or else go for the 3281/1302 and all the other newer ones.
MJ15030/15031 are the easiest (and also original) for drivers, or their higher gain 32/33 and 34/35 siblings.
The FET debate is still open, but the board has provision for 3 different types to experiment with.
For LTP transistors the original 2SC/2SA ones or BC546/556 are nice fast choices, slower alternatives would be MPS8099/8599 and MPSA42/92.
For heatsinks you can always use thyristor blocks with slow-moving fans, at low cost and space. Those metal Papst ones are very quiet and cheap at about <$40 each at the agents. Even though they're 20years old, the ones in the original MK2 are so quiet you cannot even hear if the amp's on or off except in the most silent environment.
MJ15030/15031 are the easiest (and also original) for drivers, or their higher gain 32/33 and 34/35 siblings.
The FET debate is still open, but the board has provision for 3 different types to experiment with.
For LTP transistors the original 2SC/2SA ones or BC546/556 are nice fast choices, slower alternatives would be MPS8099/8599 and MPSA42/92.
For heatsinks you can always use thyristor blocks with slow-moving fans, at low cost and space. Those metal Papst ones are very quiet and cheap at about <$40 each at the agents. Even though they're 20years old, the ones in the original MK2 are so quiet you cannot even hear if the amp's on or off except in the most silent environment.
@AndrewT
Thanks for your help! I have no doubt that this will be an expensive amplifier. I have not built a Class A yet, so this will be new for me. Unfortunately we have to import everything from Europe and with the excahnge rate as it is things are pretty expensive. I like the look of the Fischer heatsinks, but at that price I'll make another plan, hence I'm wondering what rating is required so that I could try and source something else from a local manufacturer.
@Jozua
We can definately do that, but your PM button is disabled. Pierre has my private E-mail as well. I got the pricing from Electrocomp in Midrand as they import all the Fischer heatsinks. I think if we put our heads together, including Pierre, we could source something locally. I'm going to buy the semi's in bulk, so we could join forces on that as well...
Cheers
Gert
Thanks for your help! I have no doubt that this will be an expensive amplifier. I have not built a Class A yet, so this will be new for me. Unfortunately we have to import everything from Europe and with the excahnge rate as it is things are pretty expensive. I like the look of the Fischer heatsinks, but at that price I'll make another plan, hence I'm wondering what rating is required so that I could try and source something else from a local manufacturer.
@Jozua
We can definately do that, but your PM button is disabled. Pierre has my private E-mail as well. I got the pricing from Electrocomp in Midrand as they import all the Fischer heatsinks. I think if we put our heads together, including Pierre, we could source something locally. I'm going to buy the semi's in bulk, so we could join forces on that as well...
Cheers
Gert
What heat sink, a tip?
Hello Gert and welcome to the project.
Regarding heat sinks, are your intention to build a stereo amp or two mono-blocks ?
If your intention are to build a stereo amp using no fans it will be a BIG amp due to the heavy heat sinks you will need (total heat dissipating will be >500 Watts). A better choice will be to build two mono blocks but its more expensive as you had to use two totally separated power supplies (double of everything as transformer, caps, soft start etc...).
But if you decide to build mono blocks as I intend to do, then its easier to use natural convection heat sinks. One mono block had to get rid of ca 260W of heat and if using say two heat sinks on each side of the chassis they could have a K-value of ca 0.23. It means the heat sink temperature will rise 0.23 x 130Watts = 30 degrees C above ambient. If your ambient is 22 degrees C, heat sink temperature will then rise to ca 52 degrees C.
This is an example calculated when using this heat sink (MF35, L=151.5 millimeter):
http://www.conradheatsinks.com/products/flat100_350.html#MF35
This is a very pricey heat sink and you will need four of this model (or a similar sink).
regards
Hello Gert and welcome to the project.
Regarding heat sinks, are your intention to build a stereo amp or two mono-blocks ?
If your intention are to build a stereo amp using no fans it will be a BIG amp due to the heavy heat sinks you will need (total heat dissipating will be >500 Watts). A better choice will be to build two mono blocks but its more expensive as you had to use two totally separated power supplies (double of everything as transformer, caps, soft start etc...).
But if you decide to build mono blocks as I intend to do, then its easier to use natural convection heat sinks. One mono block had to get rid of ca 260W of heat and if using say two heat sinks on each side of the chassis they could have a K-value of ca 0.23. It means the heat sink temperature will rise 0.23 x 130Watts = 30 degrees C above ambient. If your ambient is 22 degrees C, heat sink temperature will then rise to ca 52 degrees C.
This is an example calculated when using this heat sink (MF35, L=151.5 millimeter):
http://www.conradheatsinks.com/products/flat100_350.html#MF35
This is a very pricey heat sink and you will need four of this model (or a similar sink).
regards
In order to get the group buy going we need to know what type of PCB everyone wants. I;m am going to order .093 thickness no matter what. I would personally like to see a black board with gold plate traces... no solder mask and white silkscreen for parts placement. I think this type of board would be reminiscent of the boards found in older H-P test euipment. The only thing is that great care neds to be taken while soldering some of the parts in place... mainly the input and mosfet semi's. These pads are VERY close together and the smallest tip available for your iron is required to do this no matter what or you'll end up with a mess. The rest of the board is quite easy to solder with good size solder pads and the through holes are adaquate for up to 1/2 watt resistors.
PWatts would like a black board with soldermask that reveals the whole trace and these traces would also still be gold plated... I think that black with gold would look excellent and typically audiophillic but he points out that black does show the dust very fast so I was wondering about blue.....
At any rate until everyone involved that wants boards agrees I'm not ordering anything.
Lets all battle this out here and make a decision on it by next week so we can get boards made and amps built......
Mark
PWatts would like a black board with soldermask that reveals the whole trace and these traces would also still be gold plated... I think that black with gold would look excellent and typically audiophillic but he points out that black does show the dust very fast so I was wondering about blue.....
At any rate until everyone involved that wants boards agrees I'm not ordering anything.
Lets all battle this out here and make a decision on it by next week so we can get boards made and amps built......
Mark
Hi Flodstrom.
Thanks for the tip. I'm just curious as to how you would mount the output transistors if you have heatsinks on both sides of a monoblock amp? Would the negative set be on the left and the positive set be on the right?
I can get a heatsink that looks identical, just 300mm wide by 150mm high for around $45. If I understand you correct you will be using 4 of these in a monoblock? Whew! That is a LOT of heatsink
This is also a Fischer unit. I have not tried a local manufacturer yet, I have a feeling I might get a simple type like that for less.
The caps and toroids aren't too expensive, although the caps are not the best quality available.
Cheers
Gert
Thanks for the tip. I'm just curious as to how you would mount the output transistors if you have heatsinks on both sides of a monoblock amp? Would the negative set be on the left and the positive set be on the right?
I can get a heatsink that looks identical, just 300mm wide by 150mm high for around $45. If I understand you correct you will be using 4 of these in a monoblock? Whew! That is a LOT of heatsink
This is also a Fischer unit. I have not tried a local manufacturer yet, I have a feeling I might get a simple type like that for less. The caps and toroids aren't too expensive, although the caps are not the best quality available.
Cheers
Gert
Mark
I prefer Blue with gold plate traces... with a solder mask and white silkscreen for parts placement.
Alternatively the boards can have the same appearance of the Pinkmouse boards which I thought was very good looking.
Let not make it look too radical different from the original. A Blue board with silver Aluminium heatsink should look cool. Black and silver just does not have the same effect.
But I am prepared to dictated to by the groups decision....
Jozua
I prefer Blue with gold plate traces... with a solder mask and white silkscreen for parts placement.
Alternatively the boards can have the same appearance of the Pinkmouse boards which I thought was very good looking.
Let not make it look too radical different from the original. A Blue board with silver Aluminium heatsink should look cool. Black and silver just does not have the same effect.
But I am prepared to dictated to by the groups decision....
Jozua
Mounting TO-3s to a flat backed heat sink:
Hi Gert
Yes its exactly how I will do it. Also Im going to mount all the driver to the two output sinks.
This picture does not show the drivers but only the power devices because this was an earlier version than it is today when I also have included the drivers to the boards (I have designed two mirrored power boards for the TO-3s and drivers) The positive rail side also include the bias temperature sensing device (Q13). I intend to use 3 pair of drivers an 6 pair of outputs.
I will use two of these sinks per mono block making it 4 sinks total for two mono blocks.
Mark,
Hi Mark, I like your idea about 0.093", black and gold, no solder mask but if you could stand it with a blue board, gold plated, no solder mask -well, I would be very happy (I was born and grown up in Sweden you know ).
Regards
Hi Gert
Yes its exactly how I will do it. Also Im going to mount all the driver to the two output sinks.
This picture does not show the drivers but only the power devices because this was an earlier version than it is today when I also have included the drivers to the boards (I have designed two mirrored power boards for the TO-3s and drivers) The positive rail side also include the bias temperature sensing device (Q13). I intend to use 3 pair of drivers an 6 pair of outputs.
I will use two of these sinks per mono block making it 4 sinks total for two mono blocks.
Mark,
Hi Mark, I like your idea about 0.093", black and gold, no solder mask but if you could stand it with a blue board, gold plated, no solder mask -well, I would be very happy (I was born and grown up in Sweden you know
).Regards
For those who might be interested, I've just measured up the boards of the original Mk2. They're stock except for the driver transistors that was changed to MJE15032/33 and the feedback cap to a single Black Gate NX 1000uF.
With 30V rails and very low bias (less than 30mA) with a 1kHz 500mVrms sine input, THD is a very respectable 0.003%. This is of course partly due to the high gain that subsequently raises the fundemantal above the noisefloor. The noisefloor is a whopping 140dB below the fundamental, and the highest harmonics (2nd and 3rd) are at -90dB. This makes it clear that this amp without output transistors is highly suitable as headphone amp or other low-power applications due to its low noise and distortion. Higher bias, higher DC rails, locally regulated supplies, better layout etc. will raise the bar even higher.
50Hz is still an issue though as usually is with unbalanced stuff (and no it isn't improper grounding of the setup), which obviously gets much worse when an output stage is added and more so if the board is powered off the main DC bus. In this particular application it is more than acceptable at the same amplitude as the other harmonics of the input frequency.
I'll continue doing some tests, but my preliminary conclusions after measuring up the full amp as well is that separate or at least subregulated supplies for the front end and driver stage will make a much bigger difference than many of the other tweaks, and at far lower cost. Not that it's any surprise of course, but especially with a high-cost project such as this the separate supplies are cheap in comparison and highly recommended.
With 30V rails and very low bias (less than 30mA) with a 1kHz 500mVrms sine input, THD is a very respectable 0.003%. This is of course partly due to the high gain that subsequently raises the fundemantal above the noisefloor. The noisefloor is a whopping 140dB below the fundamental, and the highest harmonics (2nd and 3rd) are at -90dB. This makes it clear that this amp without output transistors is highly suitable as headphone amp or other low-power applications due to its low noise and distortion. Higher bias, higher DC rails, locally regulated supplies, better layout etc. will raise the bar even higher.
50Hz is still an issue though as usually is with unbalanced stuff (and no it isn't improper grounding of the setup), which obviously gets much worse when an output stage is added and more so if the board is powered off the main DC bus. In this particular application it is more than acceptable at the same amplitude as the other harmonics of the input frequency.
I'll continue doing some tests, but my preliminary conclusions after measuring up the full amp as well is that separate or at least subregulated supplies for the front end and driver stage will make a much bigger difference than many of the other tweaks, and at far lower cost. Not that it's any surprise of course, but especially with a high-cost project such as this the separate supplies are cheap in comparison and highly recommended.
@Flodstroem,
I see what you propose and I think I'll take this route as well. I'm curious, if I'm reading right you have made output boards for your amps? If so, would you mind sharing at all? I hate doing these thing point to point and would prefer a proper board. That should be a simple board that I could easily have made locally, or maybe we could inlcude this in the GB?
OK, so you have 2x 350x150mm sinks per monoblock. These shouldn't be TOO expensive here. Thanks!!
@Mark
Originally I thought of black boards, but think that blue mask would be a better idea as well...
I see what you propose and I think I'll take this route as well. I'm curious, if I'm reading right you have made output boards for your amps? If so, would you mind sharing at all? I hate doing these thing point to point and would prefer a proper board. That should be a simple board that I could easily have made locally, or maybe we could inlcude this in the GB?
OK, so you have 2x 350x150mm sinks per monoblock. These shouldn't be TOO expensive here. Thanks!!
@Mark
Originally I thought of black boards, but think that blue mask would be a better idea as well...