Yes, you will get the latest version bds then (PCB's were updated in 2012/13 already).
The MRE will definitely be a good upgrade for the sx-Amp. You can get the MRE from here http://hifisonix.com/hifisonix-micro-ripple-eater/
The MRE will definitely be a good upgrade for the sx-Amp. You can get the MRE from here http://hifisonix.com/hifisonix-micro-ripple-eater/
I have all the semiconductors for this amp, the hfe for BC550b/560b is 400ish ,
for the ksa1381e and the 2sc3503e the hfe is 120ish.
3281 transistors have to match with the 1302 ones? That's going to be difficult...
I can match the 3281 with another 3281 and 1302 with another 1302 but not 1302 with 3281.
I will order the boards from Jim's soon... about that , why are YOU not selling the boards directly?
for the ksa1381e and the 2sc3503e the hfe is 120ish.
3281 transistors have to match with the 1302 ones? That's going to be difficult...
I can match the 3281 with another 3281 and 1302 with another 1302 but not 1302 with 3281.
I will order the boards from Jim's soon... about that , why are YOU not selling the boards directly?
I know I've mentioned this before to you, but I do have matching 2SC3503E and 2SA1381E. the KSA and 2SC do not match well.
Match all the small signal transistors. you will probably not be able to get matched gain grades for the 3503 and 1381 - just put the closest match pairs together on the same board. The original sx-Amp did not have these matched - your amp will work ok. The power devices (3281 and 1302) come with 10% gain match from ON - just use them as you get them - again, I never matched these on my original builds.
Attention: the sx and nx amps are DC coupled on the input. You must make sure your driving source has zero offset, otherwise you must fit a DC blocking capacitor.
The sx and nx amps were developed when I was working in Asia quite a few yrs ago. I never had the bandwidth to sell the boards so I just handed it over to Jim's Audio. I did the same with the kx2-Amp since he has better reach than me on this stuff. I am selling boards directly now but not on the ones I ceded to Jim's Audio - he will run with those. I don't make any money out of the boards I sell, but it funds new projects like the X-Altra mini II etc. I think nx, sx, kx (now discontinued) and kx2 have sold about 400-500 boards in total. Funny, I have a few doctors (medical and academic) building them for some reason and the X-Altra MC/MM phono preamps. AndrewT (RIP) built a nx for his main system amp and modified it. He never told me but gave some sharp feedback on my layout - another member now has it as his main amp.
I think mine are just as good as they can get. For the people in US interested in these pairs(2SC3503E and KSA1381E), I have maybe 50-75 I could let go.
Bonsai,
is it a good idea to use one power supply for each amp?
The trafos I am planning to use are 280VA 2x35V , one for each channel .
Thanks
Attachments
I received my boards from Jim's Audio. Collecting parts. It would be nice to have all the changes & updates in one place. Digging through 136 pages for this info is very time consuming. I still don't see a BOM for JIm's amp board. I also see the amp needs low DC voltage. Anyway like hearing from builders/fans... Cheers!
@Bonsai
Can you give any sonic impressions differences between the kx2 amplifier and the nx amplifier? Class A bias options are different (and more heavily biased in Class A for the kx2), however, output power into 8 and 4 ohms in Class AB is much higher on the nx amplifier and it is also direct coupled as opposed to cap coupled. I am guessing that the distortion spectra at low power levels are similar between the 2 designs given that they are both CFA topologies. The nx includes the option of speaker protection integrated onto the PSU board. A ripple eater doesn’t seem necessary with the nx (given the very lower Class A bias) whereas with kx2 it would be recommended although not required.
Best,
Anand.
Can you give any sonic impressions differences between the kx2 amplifier and the nx amplifier? Class A bias options are different (and more heavily biased in Class A for the kx2), however, output power into 8 and 4 ohms in Class AB is much higher on the nx amplifier and it is also direct coupled as opposed to cap coupled. I am guessing that the distortion spectra at low power levels are similar between the 2 designs given that they are both CFA topologies. The nx includes the option of speaker protection integrated onto the PSU board. A ripple eater doesn’t seem necessary with the nx (given the very lower Class A bias) whereas with kx2 it would be recommended although not required.
Best,
Anand.
Anand, I use my kx2 to listen to jazz (I like 3 piece stuff a lot, Ella Fitzgerald etc) and classical and I used the nx-Amp for stuff like Fourplay, Bill Frisell, Steve Gadd etc. I currently use one of my commercial amps (Model 1721) to drive my B&W703's for this kind of music and gave not used the nx-Amp for quite some time.
I am pretty pleased with the kx2. I hit a few bumps with the original kx but the kx2 really takes things up a notch or two. However, it's not for me as the designer to blow my own trumpet.
BTW, the nx-Amp is the basis of the Model 1701 (and the Model 1707 integrated) power amp reviewed by Hi-Fi World a few years ago. There are a few tweaks, but basically it's the same amp - you can read the comments here
https://www.ovationhifidelity.com/product/model-1701/
I am pretty pleased with the kx2. I hit a few bumps with the original kx but the kx2 really takes things up a notch or two. However, it's not for me as the designer to blow my own trumpet.
BTW, the nx-Amp is the basis of the Model 1701 (and the Model 1707 integrated) power amp reviewed by Hi-Fi World a few years ago. There are a few tweaks, but basically it's the same amp - you can read the comments here
https://www.ovationhifidelity.com/product/model-1701/
For NX, Q8 and Q10, Q9 and Q11 - BC546B and BC556B, I can only match to within about 30mv. what would the distortion look like? HFE is a close match
I have a supply BC547B and BC547B as well but can only match HFE to within 100
FWIW, and for me Ovation NX is well suited to a particular speaker rather than music Genre. Ovation NX sounds great with budget tweeters, makes them smoother. Good power for less efficient 2way as well.
I have a supply BC547B and BC547B as well but can only match HFE to within 100
FWIW, and for me Ovation NX is well suited to a particular speaker rather than music Genre. Ovation NX sounds great with budget tweeters, makes them smoother. Good power for less efficient 2way as well.
Joel,
this will not alter the distortion by more than a few ppm - its mainly the distortion profile that changes. If you match them perfectly, the 2nds cancel and you are left with mainly 3rds and 4th. If they are badly mismatched, you get higher 2nds. In any case, its mostly low order and drops off very steeply after 4th.
We are talking about c. 50ppm at 80W here on +-45V rails into 8 ohms - worst case c. 70 ppm.
You should try to match your small signal transistors a bit closer in my view - however, the mismatches you are seeing will not prevent you amp from working well.
this will not alter the distortion by more than a few ppm - its mainly the distortion profile that changes. If you match them perfectly, the 2nds cancel and you are left with mainly 3rds and 4th. If they are badly mismatched, you get higher 2nds. In any case, its mostly low order and drops off very steeply after 4th.
We are talking about c. 50ppm at 80W here on +-45V rails into 8 ohms - worst case c. 70 ppm.
You should try to match your small signal transistors a bit closer in my view - however, the mismatches you are seeing will not prevent you amp from working well.
asuslover,
apologies, I seem to have missed this. If you decide to use separate PSU's that's ok jut take note:-
Its easier to get cross channel ground loops if you are not careful with this approach. Make sure you have one and only one connection between the channels and that should be where the left and right signal ground bond together at the input connectors. Your bond to the chassis (important for safety) should come off this pointy as well and the incomming IEC safety ground tied tied there as well. This way, you will have no possibility of any internal ground loops. Place the connectors right next to each other and not on opposite sides of the rear panel.
3 different Omni Semi's complimentary batches that I have all show 30mv average VBE span from the NPN to PNP.
Average around 762mv vs 788mv.
This is with Atlas DCA Pro where its displays Vbe at IB=5.0ma
Am I missing something? Are my my batches typical or atypical? would be nice to solve this
Average around 762mv vs 788mv.
This is with Atlas DCA Pro where its displays Vbe at IB=5.0ma
Am I missing something? Are my my batches typical or atypical? would be nice to solve this