Nope. Not a true apples-to-apples comparison. I'm using a DC-DC converter to boost the main rails by 12V, then filtering with a RCRC filter that drops about 6V for a final boost of +6V.
So what I understand from the last comments, it will at least not hurt to keep the cap multiplier as is?
You lose the voltage drop across it.
If you keep it, I'd put it before the VAS so it filters the supply to the IPS & VAS.
If you keep it, I'd put it before the VAS so it filters the supply to the IPS & VAS.
It is fine, nothing to change. I am having similar thoughts to Brain, run the output from the raw DC and the upconvert the driver stage by a voltage doubler followed by a regulator. The front end needs be clean.
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I think the original THD values are pretty good already. For me, no need to add more complexity to lower more.
Brian and Nico! I agree with both of you, and as far (which is not very far) as I understand we ar nitpicking at this point.
The HV is well regulated, and in my case, probably includes a cap multiplier, My IPS will most happily accept an additional small voltage drop from the multiplier, while the VAS is the stage that needs the extra voltage (super regulated, that is). Will there be any audible or measurable difference at all?
The HV is well regulated, and in my case, probably includes a cap multiplier, My IPS will most happily accept an additional small voltage drop from the multiplier, while the VAS is the stage that needs the extra voltage (super regulated, that is). Will there be any audible or measurable difference at all?
I had the same feelings on drivers. The added complexity didn't seem worth it.
I think loosing 2nd harmonic will make it sound too dry. A little body is a good thing
So I guess, this thing is complete, It is what was set out to be and I think will turn into a great sounding amp, thanks all and a special thanks to Brian for his design and patients and trying all the different configs and suggestions.
Morten, would you say your PCB is at revision for build? You have done an excellent job too, many thanks. A true artist in more ways than one.
As a complete amateur I am really pleased to have conversations with audio erudites who knows what you are talking about! Thank you for spending your time.
Brian: Yes, I will make Gerbers tomorrow when I am sober and awake. I usually make PCBs at NexPCB, but my last order stalled as they asked for all sorts of peronal data, VAT numbers and what not. Can anyone recommend a cheap manufacturer? I have plenty of time but not that much money, hehe.
Brian: Yes, I will make Gerbers tomorrow when I am sober and awake. I usually make PCBs at NexPCB, but my last order stalled as they asked for all sorts of peronal data, VAT numbers and what not. Can anyone recommend a cheap manufacturer? I have plenty of time but not that much money, hehe.
The improved PSRR (from Cap-X) shouldn't improve performance. Rather, it helps it from degrading if the supply isn't clean.
For the voltage boost, in sims I found at least 3V to be of benefit. For some reason, my models for SC3503/SA1381 responded well to the boost. TTC004B/TTA004B didn't seem to care. Not sure if this is simply a simulation quirk or a reality.
There's two reasons to boost the IPS/VAS rails from my perspective:
Keep in mind the voltage rating of the input FETs. In my version using LSK489/LSJ689, they are rated for 50V. Taking into account PSU regulation and mains regulation, I'd try to keep the IPS-VAS rails are 45V or less. You have different devices, so you'll need to assess this yourself.
Regarding power levels, I targeted for 30V main rails because that provides 40W of class AB output. But more importantly, the output in the first 25W is very clean. Distortion seems to rise more above this point. I can't see needing more that 25W, so this works for me.
For the voltage boost, in sims I found at least 3V to be of benefit. For some reason, my models for SC3503/SA1381 responded well to the boost. TTC004B/TTA004B didn't seem to care. Not sure if this is simply a simulation quirk or a reality.
There's two reasons to boost the IPS/VAS rails from my perspective:
- To allow for a filter (Cap-X or RC filter) to improve PSRR without loosing voltage.
- To allow the MOSFETs to swing closer to the rails which increases Class AB output potential without actually raising the OPS rails. The main reason this is a benefit is when running a large Class A region where dissipation is a concern. You can run a bit more Class A for the same Class AB output potential.
Keep in mind the voltage rating of the input FETs. In my version using LSK489/LSJ689, they are rated for 50V. Taking into account PSU regulation and mains regulation, I'd try to keep the IPS-VAS rails are 45V or less. You have different devices, so you'll need to assess this yourself.
Regarding power levels, I targeted for 30V main rails because that provides 40W of class AB output. But more importantly, the output in the first 25W is very clean. Distortion seems to rise more above this point. I can't see needing more that 25W, so this works for me.
Brian, I know this is not a military project but can your simulator automatically step all components under worst case condition and tolerance spread, say over voltage as well and a failure analysis. If I could I would because that will already beat any design I have ever seen on DIY for integrity and design with a near 100% probability of success. It all depends if it will do it automatically, else don't do it you will be and old man at the end.
LT Spice doesn't have a Monte Carlo analysis that I'm aware of. At least not an automated one. I think you need to use fancier professional simulators for those bells and whistles.
I try look at the design and theorize which components might need precise values. Then adjust them manually to confirm my suspicions.
I try look at the design and theorize which components might need precise values. Then adjust them manually to confirm my suspicions.
Did not see an answer to this...
The VAS transistors run at almost 1W (with current 23mA) and the TO-220 has a thermic resistance around 100 K/W to ambient, so yes, they should be on a heatsink.
I don't know if I am going to break a DIY golden rule, but my suggestion would be for Morten to get pricing for the prototype and then give us his banking detail so that we can help him finance it, Even a dollar some times help, lets call it crowd funding. I wanting to sell kits as well then Brian and Morten select their share for either a kit or fully built product. Open a bank account BRIATEN and the business kicks off.