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I have a boss DSP that requires a 800mA PSU at 12VDC. I can't find it's PSU so i tried a 9VDC/500mA PSU I had and it;s been working fine for the couple week i've been using it. But I'm wondering how that may affect performance. The effects sound fine so thats a non issue. But it's in the passive effects loop of my amp so i have to wonder how this will affect the in/out amps. Will i lose headroom? Any other thoughts on this are welcome. I'd just buy the proper one but being out of work and living on a shoestring has me watching every penny.
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Boss DSP what?
If it runs off of a 9Vdc battery, well.............. -
No, like i said it requires 12v/800mA and it's a rack DSP.Originally posted by Jazz P Bass View PostComment
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It is working...
Any idea what the actual voltage coming out that 9v supply might be? Until they are max loaded, their voltages usually run quite high.
The internal circuits work on some lower voltage than the adaptor, unless it has a DC/DC converter inside. The DSP will need 5v and 3.3v most likelyEducation is what you're left with after you have forgotten what you have learned.Comment
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You are not that much on a shoestring if you have a Rack type DSP processor.
And you worry about *your headroom?*
If I were counting pennies I bet I´d have far more pressing and immediate problems in my mind.
Just sayin`
How many pennies will you need to repair something misused?Juan Manuel FaheyComment
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I need to update this because i realized i was wrong about the adapter rating and DSP spec, and also because i am having an issue that may be related. So let me rephrase the original post. And don't ask me how i missed the specs because its a mystery to me too. First, the unit's spec for a PSU is 14VAC (yes, AC) at 800mA. The supply i'm using is 12VAC at 500mA. The thing works fine as far as all it's functions and if i run a second amp for effects only and set it 100% wet things are fine.The probalem lies with what happens with the DSP in the amp's effects loop. There it adds distortion and compression above what i hear when bypassed, and it's not good distortion.compression. If i A/B the amp with the loop bypassed them with the loop in but no effect, just a patch cable, the tone is the same both ways. It only happens with the DSP. And the level meter is set so it reads right in the middle and i have tried even lower and higher and every imaginable way to gain stage the setup but the issue remains. Theres also a +4/-20 switch and the loop is designed for +4 so thats where i use it. The question is, can i be sure the reason for this issue is the PSU or could it just be the unit's gain stages are not quality? I don't want to buy an adapter only to find not change. I just have no idea whether 2v and 300mA under the spec is definitely going to manifest in that way when the unit otherwise works fine. This by the way is not the loop i posted about a few months back. This loop is a clone of the SLO loop and the amp is exactly the same as a SLO from the last preamp stage thru the CF, tone stack, loop and PI aside from a DPDT loop bypass i put in.Comment
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While it is always advisable to use the correct power supply (lower voltage means higher current), I doubt if it makes much difference in this case. Digital stuff either works or it doesn't. I guess it's possible some analog buffer circuit is affected, but I doubt it. What you are describing is why many of us do not use DSP effects....Originally posted by daz View PostComment
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Thats what i was talking about....the analog amplifiers in it. I figured if they are starved maybe they might distort.Comment
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It isn't that precise. As long as the AC voltage going in has enough headroom, it will be OK, The analog voltages are regulated, so as long as the raw supply can make about 17vDC, we are OK.
It may help you to measure the AC voltage at the power jack while it is running, I'd wager your 12v supply is providing more than that.Education is what you're left with after you have forgotten what you have learned.Comment
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Ok, so i guess as olddawg suggested it's just a typical issue with digi effects.Comment
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- The digital circuitry most likely uses very low supply voltages in order of 5VDC and/or 3.3VDC. Most likely these are also derived from a regulated source so as long as the input voltage provided to the power supply is higher than that then supplying enough volts to the digital circuitry shouldn't be a problem. There's still a lot of headroom with 12VAC input to generate 5.5VDC or less.
- Despite the unit being "digital" it most likely features some analog circuitry, such as input and output stages preceding the AD/DA CODEC chip. These are likely designed to operate at higher supply voltage than the digital circuitry (e.g. +/-12VDC) , regulated or not, and in their case lower input voltage will lead to lower operating voltages that in turn reduce maximum signal voltage swing and therefore headroom of the stages in question, resulting to earlier clipping and distortion. Yep, "strarving" is a nickname sometimes used for that. However, these stages most likely will not stop completely working with minor supply voltage "mismatch" such as dropping from 12VAC to 9VAC. Even more so if teir part of the power supply happens to be unregulated.
Since they are also likely tuned to signal levels of the CODEC and/or for "line level" outputs and inputs they will not generally even feature very high voltage swings to begin with. (Expect something like 3Vpeak maximum). Not to mention, some A/D interfaces deliberately clipping limit the signal so that it never exceeds the lower voltage the digital circuitry works with. So, basically as long as you are operating the unit within typical signal levels then you most likely detect no significant difference in performance even if the rail voltage of the analog stages drops a few volts. It only poses a problem if regulator circuits stop working.
- Current draw is likely your main concern. If the unit draws more current than the supply can supply the result is voltage sag, and if it is significant it might begin to interfere with operation of the regulator circuitry. If that supply voltage sags below levels where the power supply can no longer generate proper voltage for the digital or analog circuitry then most likely those circuits stop working alltogether. Or they begin to work "randomly", such as "booting" your unit every now and then. Range of quirks introduced by improerly operating hardware / soft can be vast. Just think about in how various ways ordinary computers can "crash".
Your unit obviously works - for now - but how about in those special occasions when the unit gets dialled so that it draws the maximum current, assumably that 800 mA or close...? At that point I would expect problems. ...And that digital stuff is often way more hungry for current than "small signal" analog circuitry.Comment
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