Admittedly, and I forgot to mention earlier, Isolating the psu 0v from earth ground was a major help. As far as the other grounding issues, I don't know exactly, it was just a matter of spending time moving things around in there. Everything does go back to the alu bar at the psu caps however. My toroid still does buzz a bit but I'll be darned if I can hear it at more than 1 inch from the speaker..or maybe I'm deaf
Did I mention that I really like this amp
Did I mention that I really like this amp
Hi everyone!
Everything is ok and I'll send you all an Email with info of how to pay for the badges. To make sure that I have all necesary info I would like for everyone to be sure that your correct adress is stated in the paypalreciept.
The exeption is your dear moderator
So, Pinkmouse, Al, could you send me an E-mail so that I can get past the spamfilter or whatever it is?
Everything is ok and I'll send you all an Email with info of how to pay for the badges. To make sure that I have all necesary info I would like for everyone to be sure that your correct adress is stated in the paypalreciept.
The exeption is your dear moderator
So, Pinkmouse, Al, could you send me an E-mail so that I can get past the spamfilter or whatever it is?
Heatseakers
For those still in need of heatsink (& fan), I found this on eBay. Could be of interest to some?:
http://cgi.ebay.co.uk/Large-Heatsin...3QQihZ017QQcategoryZ36332QQrdZ1QQcmdZViewItem
I am still gathering parts for this amp, and will soon be there but have yet to get any output transistors. I don’t really know anything about transistor specifications, but from what I have read so far, the MJL4281A seems to get most people’s approval. I plan to order 6 pairs and intend to mount them directly to the heatsinks, but would like to know that they would work if I decide to use the output boards.
...so could anyone, please confirm that these would be a good choice and are compatible with the Pinkmouse output boards if need be? Thanks
For those still in need of heatsink (& fan), I found this on eBay. Could be of interest to some?:
http://cgi.ebay.co.uk/Large-Heatsin...3QQihZ017QQcategoryZ36332QQrdZ1QQcmdZViewItem
I am still gathering parts for this amp, and will soon be there but have yet to get any output transistors. I don’t really know anything about transistor specifications, but from what I have read so far, the MJL4281A seems to get most people’s approval. I plan to order 6 pairs and intend to mount them directly to the heatsinks, but would like to know that they would work if I decide to use the output boards.
...so could anyone, please confirm that these would be a good choice and are compatible with the Pinkmouse output boards if need be? Thanks
Thanks Andrew,
Would you not recommend using 6 pairs?
Also it seems to me from looking at the spec charts for these transistors that there is a difference between 4281 and 4302 and yet they always seem to be bracketed together as the same. Is one a better choice over the other for this application?
Is there a preference between the lead free devices and the standard?
Would you not recommend using 6 pairs?
Also it seems to me from looking at the spec charts for these transistors that there is a difference between 4281 and 4302 and yet they always seem to be bracketed together as the same. Is one a better choice over the other for this application?
Is there a preference between the lead free devices and the standard?
Hi,
6pairs sounds nice, but why?
to drive lower impedance loads?
to dissipate more quiescent current?
to run at lower temperature?
If you are not sure why more pairs might suit you then don't change the design, copy what you have been given.
BTW. if you do NEED a 6pair output stage for your proposed use then you will need to spend even more money on the PSU than already specified for the standard Klone.
6pairs sounds nice, but why?
to drive lower impedance loads?
to dissipate more quiescent current?
to run at lower temperature?
If you are not sure why more pairs might suit you then don't change the design, copy what you have been given.
BTW. if you do NEED a 6pair output stage for your proposed use then you will need to spend even more money on the PSU than already specified for the standard Klone.
The reason for six pairs is mainly to suit the heatsinks I have, it would work out at one transistor per sink, and help lower the temp per device.
Yes, I don’t NEED six pairs but I would like to make this amp as future proof as possible, and would like to have the option to drive low impedance loads if need be.
I am very new to this game and this will be my first electronics project, so you are right I would be much better off sticking to the original design. But with 625VA, 30V transformers per channel I gather it is safer to have an extra output pair or two to deal with the extra dissipation, and with the heatsinks I have it seemed natural to go for 6 pairs to enable a device per sink.
So for ordering the transistors do I need half of one type and half the other, i.e. (3-No. MJL4302 & 3-No. MJL4281)?
When you say spend even more money on the PSU, is that for higher rated components or extra components to allow for the extra output devices?
Your assistance and comments are greatly appreciated.
Yes, I don’t NEED six pairs but I would like to make this amp as future proof as possible, and would like to have the option to drive low impedance loads if need be.
I am very new to this game and this will be my first electronics project, so you are right I would be much better off sticking to the original design. But with 625VA, 30V transformers per channel I gather it is safer to have an extra output pair or two to deal with the extra dissipation, and with the heatsinks I have it seemed natural to go for 6 pairs to enable a device per sink.
So for ordering the transistors do I need half of one type and half the other, i.e. (3-No. MJL4302 & 3-No. MJL4281)?
When you say spend even more money on the PSU, is that for higher rated components or extra components to allow for the extra output devices?
Your assistance and comments are greatly appreciated.
Hi,
your 30Vac transformer is slightly over voltage compared to the original and Klone but well within an acceptable spec.
It will, as you have already surmmised, increase your dissipation and here higher Pq can be alleviated by bigger sinks and/or more pairs or higher rated devices.
Pd KSA = 2*250W=500W
Pd Klone=3*150 to 250W depending on device chosen = 450 to 750W
Pd 4281/302 = 3*230=690W, you are already onto a winner.
and 4pair is even better. The Klone PCB allows for 3pr of To147 or To264.
I plan to use 5pr or 6pr 2sa1943/c5200 giving 750W or 900W allowing ClassA into 6.5r at full output voltage (about 120Wrms into 6.5r) but this commits me to three large sinks and hardwiring which will not be nearly as neat.
The big downside to plastic packaged devices is the lower Tj of 150degC cf. 200degC for the To3 devices.
At the elevated temperatures of ClassA, this limits the useful Tc(max) to about 60degC to 70degC plus a small factor of safety for slight imbalances in current flows, thermal conductivity, device variations etc.
your 30Vac transformer is slightly over voltage compared to the original and Klone but well within an acceptable spec.
It will, as you have already surmmised, increase your dissipation and here higher Pq can be alleviated by bigger sinks and/or more pairs or higher rated devices.
Pd KSA = 2*250W=500W
Pd Klone=3*150 to 250W depending on device chosen = 450 to 750W
Pd 4281/302 = 3*230=690W, you are already onto a winner.
and 4pair is even better. The Klone PCB allows for 3pr of To147 or To264.
I plan to use 5pr or 6pr 2sa1943/c5200 giving 750W or 900W allowing ClassA into 6.5r at full output voltage (about 120Wrms into 6.5r) but this commits me to three large sinks and hardwiring which will not be nearly as neat.
The big downside to plastic packaged devices is the lower Tj of 150degC cf. 200degC for the To3 devices.
At the elevated temperatures of ClassA, this limits the useful Tc(max) to about 60degC to 70degC plus a small factor of safety for slight imbalances in current flows, thermal conductivity, device variations etc.
Once again thanks for your reply Andrew,
The transformer was a choice between 625VA 30V or 500VA 25V, I thought it would be best to go for the higher power & voltage and try to tailor the amp to be more like a KSA-80. I appreciate with my skill level this could be getting myself into deep water, but while I’m at it I figured that I’d give it a go. It may not be too late to exchange the transformers and go for the 25V but would prefer to go for higher voltage rails instead of lower given the option.
Your point about hard wiring has also been playing on my mind, but with my sinks, I fear I have no option, and hence while I’m at it I figured it is another reason to use more devices. The distance between first and last output device will be approx 300mm, do you know if this will cause any problems and is there anything I should take into consideration with the layout, for example do devices need to be evenly spaced from one another?
Is your last point another argument to use more devices so as to lower the device operating temperature, or have I miss understood this?
The transformer was a choice between 625VA 30V or 500VA 25V, I thought it would be best to go for the higher power & voltage and try to tailor the amp to be more like a KSA-80. I appreciate with my skill level this could be getting myself into deep water, but while I’m at it I figured that I’d give it a go. It may not be too late to exchange the transformers and go for the 25V but would prefer to go for higher voltage rails instead of lower given the option.
Your point about hard wiring has also been playing on my mind, but with my sinks, I fear I have no option, and hence while I’m at it I figured it is another reason to use more devices. The distance between first and last output device will be approx 300mm, do you know if this will cause any problems and is there anything I should take into consideration with the layout, for example do devices need to be evenly spaced from one another?
Is your last point another argument to use more devices so as to lower the device operating temperature, or have I miss understood this?