Hi everyone;
a few weeks ago i received the boards for my SE-SE headphone-amp including PSU (thanks to OPC). As i am about to order all necessary parts, i took a close look into the BOM's and the schematic...and here is something i have never seen before: The PSU uses TWO negative regulators, that means a TPS7A3301 for the positive voltage-rail as well (output connected to GND)....
Sorry for my lack of knowledge but what is this design called and how does it work?
Regards,
Mickie
a few weeks ago i received the boards for my SE-SE headphone-amp including PSU (thanks to OPC). As i am about to order all necessary parts, i took a close look into the BOM's and the schematic...and here is something i have never seen before: The PSU uses TWO negative regulators, that means a TPS7A3301 for the positive voltage-rail as well (output connected to GND)....
Sorry for my lack of knowledge but what is this design called and how does it work?
Regards,
Mickie
Hi Mickie,
See a similar question from Nikitas here:
http://www.diyaudio.com/forums/vend...-here-bal-bal-se-se-lpuhp-16.html#post3700639
See my answer here:
http://www.diyaudio.com/forums/vend...-here-bal-bal-se-se-lpuhp-16.html#post3700727
Using dual negative (or positive) regs is a pretty old trick that you can easily play if you have control over the ground arrangement heading into the regulators. This trick is not possible if the input side of the regs has to share a common ground. This is why a dual secondary transformer is now a requirement for the new PSU.
Cheers,
Owen
See a similar question from Nikitas here:
http://www.diyaudio.com/forums/vend...-here-bal-bal-se-se-lpuhp-16.html#post3700639
See my answer here:
http://www.diyaudio.com/forums/vend...-here-bal-bal-se-se-lpuhp-16.html#post3700727
Using dual negative (or positive) regs is a pretty old trick that you can easily play if you have control over the ground arrangement heading into the regulators. This trick is not possible if the input side of the regs has to share a common ground. This is why a dual secondary transformer is now a requirement for the new PSU.
Cheers,
Owen
Something seems to have gone wrong here as I shipped your order out a very long time ago.
I haven't heard anything from anyone else about missing parcels, so yours might be the first to have been swallowed up in the void that is Canada Post and USPS.
If you send me an email, we can hopefully get things sorted.
Regards,
Owen
My BAL-BAL arrived today and all parts now soldered in place. Those heat-sinks are a pain in the bum to solder... Enclosure & a few other bits to get before it's ready to rock
They really are a pain, and probably not needed at lower rail voltages, but it's best to have them if you're running above +/-9VDC.
As an alternative, some builders have just sandwiched the whole board between two aluminum plates, which also works.
Looking forward to pics and listening impressions!
Cheers,
Owen
A complete stereo BAL-BAL will draw roughly 110mA from each supply rail at idle, and can draw a maximum of 530mA from each supply at full power.
The full power scenario assumes you are in full current delivery mode which is very unlikely with headphones.
These current draws will reduce somewhat at lower rail voltages.
Regards,
Owen
Hi Owen,
Do you have an update on the v3 ntd1 boards? I started planning a build, got hold of a v2 board but then put things on pause as I know you're working on an update. Is the change limited to the updating of the psu to the new regulators or are more changes afoot? If just the psu is it possible to order regs or reg boards from you and retrofit to v2 board? If the whole board is getting a re-think I may go ahead with the v2 build and then take a look at updating the whole thing later on. Any thoughts?
Cheers,
Crom
Do you have an update on the v3 ntd1 boards? I started planning a build, got hold of a v2 board but then put things on pause as I know you're working on an update. Is the change limited to the updating of the psu to the new regulators or are more changes afoot? If just the psu is it possible to order regs or reg boards from you and retrofit to v2 board? If the whole board is getting a re-think I may go ahead with the v2 build and then take a look at updating the whole thing later on. Any thoughts?
Cheers,
Crom
Hi Crom,
Work is coming along on the new NTD1 boards, and I'm guessing it will be about a month before I'm ready to release the boards to fab. After that, it should be a few weeks for delivery and testing.
Here's the current plan:
There will be 4 variants of the circuit, and the boards themselves will be offered as the output circuitry only, so no PSU on board. I will likely use the existing PSU V2 to power everything, so people can choose their supplies if they prefer. I may develop a higher voltage supply for the classic, but this may not happen.
The four variants will be:
NTD1 Classic
PSU will be off-board, and circuit/layout will be re-routed to optimized for four layers. This will allow users run any voltage rails they like, and use either the existing PSU V2 or a supply of their choosing. Circuit will remain the same as the current NTD1 but I may change the footprints for the output coupling caps to allow for more options.
NTD1 - DC Coupled
Uses a diff op-amp at the output instead of using coupling caps, so no caps in the signal chain. the NTD1 provides I/V conversion but has much less gain, allowing for lower value resistors, and much higher current with lower voltage rails. The diff op-amp provides a voltage gain of 4x to maintain the same 2VRMS @ 0dBFS gain of the current design. This allows the NTD1 to do what it does best (I/V) and lets the op-amp do what it does best (voltage gain). This circuit measures better than the NTD1 classic, but I know some people won't like the op-amp.
NTD1 - SERVO
This variant uses a servo to keep the input at exactly 1/2 AVCC and has sub 10 mohm input impedance. It requires no adjustment or biasing, and dissipates less power than the classic NTD1 while hopefully delivering significantly improved performance. I say hopefully because I've only simulated this one, and it looks incredibly promising. Proto boards are one the way soon for a real world test
NTD1 - EVO - DC
This will be a combination of the EVO and the DC coupled version. Again, I have only simulated this one, but performance is incredible and offers DC coupling. If you aren't afraid of op-amps in your circuits, and want the ultimate in performance, this will probably be the one to go with.
I will of course have test data for every one of these, so people can draw their own conclusions on which best suits their needs. I will also offer a "Chef's Tasting Menu" option where you can buy all four PCB variants for a little less. These things are dirt cheap to build up, so it might be fun to try them all and pick your own favorite.
I'm also considering doing a P-channel variant that is DC coupled and doesn't use caps or an op-amp on the output. The downside is that output voltage swing is limited to about 500mVRMS. This might be perfect for some headphones, so it will probably be done separately as a headphone specific option.
Cheers,
Owen