It's alive! Cranked my L C R outputs down -12 db from where they were...holy crap the MiniDSPs sound A LOT better when you only ask them for that level of output.
One problem, though. Noise. Lots of it.
Check it out: https://www.youtube.com/watch?v=YbGOQ3nSoLI
One problem, though. Noise. Lots of it.
Check it out: https://www.youtube.com/watch?v=YbGOQ3nSoLI
Did you connect the grounds of the miniDSP power supply and the power supply for the gain stage boards together, and if so how did you do that?
What power supply did you end up using for the miniDSP? If it is a switching supply it can be radiating the noise into the gain stage PCB...
Apart from that, you should be aware that the gain stage board doesn't differentiate between signal and noise... it raises both by (in your case) 12dB. Was there a gentle hiss before, which now has become very noticeable?
The other thing you can do to reduce noise a bit is switch the miniDSP board output level to the 0.9v configuration (if your board has jumpers for that).
I did not connect the grounds together. I can try that, if it might help. Would it be as simple as running the ground from the dsp phoenix plug up to the ground on the board, like I had it before when I was trying to power both from the little trafos, or is there a better way?
The supply I added for the MiniDSP is (was) a wall wart, but it's a linear type. It has a regulator, a cap and a couple of diodes on it's board. It gave 12v unloaded and around 10v with both boards connected to it. It was labelled as 9 vdc.
I'm aware - and was expecting the boards to bring the noise floor up as baggage with everything else. They hissed a little before, but it seems to have crossed the barrier between "it doesn't annoy me" and "ok, now it's annoying." DSPs are set to 0.9v at the moment. I wonder if the cure might be trimpots, so I could dial back the gain a little on the main channels? Might help strike a balance between gain vs dsp noise.
Overall though, despite the noise, I have to say that the whole dsp arrangement sounds a lot better now, when I crank the volume up to rocking levels and the MiniDSP is still in the green. Bass in particular seems much improved at higher levels. Tons of kick that it didn't have before.
Yes, just run a wire like you described.
OK, sounds like a basic unregulated PS. A regulated one might be better in terms of noise, not sure though.
Sounds like a volume control might be better for your setup. I thought I might have seen a compression driver tweeter in your setup. Is that right? These can make noise very evident if gain structure is not carefully controlled.
You now have lots of headroom at higher volume levels where before the miniDSP may have been starting to clip on peaks. Of course you also have more output to drive the amps harder as well. It all translated into better dynamics at the higher output levels.
Yep, it's a compression driver on a 10" waveguide. I essentially dismantled a few Peavey PR-10s into what sort of resembles an econowave. They do really well, but yeah, the tweeter is pretty sensitive, which puts a laser pointer on noise.
I tried the ground wire just now, doesn't seem to have changed anything for the better or worse.
I guess my next step is a bunch of pots...or maybe something like this: 8-Gang Audio Potentiometer, .05W, 20kΩ, 3BM Taper, 6x15mm Shaft, NOS [POT8-.05W-3BM] - $19.50 : ElectronTubeStore.com, Raw Materials and Components
I tried the ground wire just now, doesn't seem to have changed anything for the better or worse.
I guess my next step is a bunch of pots...or maybe something like this: 8-Gang Audio Potentiometer, .05W, 20kΩ, 3BM Taper, 6x15mm Shaft, NOS [POT8-.05W-3BM] - $19.50 : ElectronTubeStore.com, Raw Materials and Components
See attached. Note C24 is connected backwards in the schematic (I labeled this in the pic) - I corrected this with a sharpie on the board I sent out.
Attachments
The board includes an onboard regulated power supply except for the transformers, which connect at the two terminal marked "AC". If you don't want to use the onboard PS, you can leave off all the PS parts except C22 and C32 and connect your power supply to the "DC Power" terminal. I envisioned it the other way around - that the board would export DC power via this terminal, but either way can work.
Sorry typo I guess. It's obviously C23 and C33.
Good idea, I've attached the parts list.
Hi Patrick,
The output of the gain stage can be set by the builder - I use 68R resistors in series with each output for instance. There is a HF feedback path before this resistor, and the gain setting feedback path is taken after.
The parts list is posted above (using Mouser part numbers). I could sell you the PCB, however, I have to warn you that the shipping cost is expensive - about US$25 to where you live. If you are still interested, send me another PM and we can go from there.
Thanks,
-Charlie
OK, I guess I'll have to live with the shipping costs, Mouser's are not low either, anyway. I'll sent you a PM! /patrick
neilI have started a new thread for the gain stage board design in the analog line level section here:
http://www.diyaudio.com/forums/anal...channel-gain-stage-power-supply-new-post.html
This is a revised design of the gain stage that I previously made.
I have received several inquiries about the original boards. Unfortunately I don't have any more, but i can offer this new design for those who would like a gain stage for the MiniDSP. I will post the gerber files in the near future, suggest a pcb fab, and let people run with it if they would like.
http://www.diyaudio.com/forums/anal...channel-gain-stage-power-supply-new-post.html
This is a revised design of the gain stage that I previously made.
I have received several inquiries about the original boards. Unfortunately I don't have any more, but i can offer this new design for those who would like a gain stage for the MiniDSP. I will post the gerber files in the near future, suggest a pcb fab, and let people run with it if they would like.
UPDATE: the gain stage board has been redesigned and improved. The gerber files have been posted in the thread linked to above, in this post:
http://www.diyaudio.com/forums/anal...el-gain-stage-power-supply-4.html#post4600044
Feel free to produce the pcb, build the board, and use this project in any personal/non-commercial applications.
3D rendering of the fully populated board:
http://www.diyaudio.com/forums/anal...el-gain-stage-power-supply-4.html#post4600044
Feel free to produce the pcb, build the board, and use this project in any personal/non-commercial applications.
3D rendering of the fully populated board:
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