ericn
Temp
Balance Engineer
Posts: 14,935
|
Post by ericn on Jul 22, 2020 10:46:37 GMT -6
OK I’ll give you a little more history of the Delta Family as somebody who both used and sold them. The Soundcraft Delta / Venue family was the replacement for the 200/ 400/800 series. The most Basic was the Delta SR 4 buss 4, aux 3 band mid sweep EQ, the more standard Delta was 4 bus 6 aux on 4 knobs 4 band 2 mid sweeps. There was a very rare Delta 8 bus that was similar to the standard And deluxe Delta but had 8 bus routing. In addition the Delta also had stereo and a very rare digital stereo modules. All deltas used the same bus and master modules. There was also a Delta monitor console. The Venue was the 8 bus version with 6 aux on 6 knobs. The most versatile version is the Venue theatre ii, 6 auxes with pre/ post fader switches for each send. Otherwise pre/post aux selection is done via jumpers on each input. Frame sizes from the little baby frame like Wiz’s to a 52 module (Venue 40x8x2 with 2 empty slots). One of the great features of these is the fact that you can remove the side panels and bolt small frames together. These things even in stock form are not about color, they are punchy clean ( maybe the cleanest boards ever built). The mods will make these things even cleaner more dynamic and bring the all ready low noise floor even lower. I toured on all most ever version except the Theater ii and owned a Venue 24, the only reason I sold the Venue is My DDA has better routing for recording. Touring I loved these things, the only diss was I found I needed to bring some outboard pres to warm things up at times, unlike a Midas XL200 series but I always heard the sound of the VCA’s in the Midas so if I could do the show without VCA’s the Delta / Venue would be my first choice. Go big on the PSU, they love current stock and that goes double for modded. The only real complaint I can think of is the compact depth of these things makes the Venue modules a little tight, replacing the knobs with something a little smaller makes things better but it’s one area where some bigger boards feel more comfortable, though if you find yourself behind a Mackie for an hour the Delta family feels like a stretch limo. Most have fairly nice highend Alps faders, some have have P&G nicer and if you go whole hog with the JW recommendations TKD awesome! Unlike modern boards the modules are easy to work on through hole. The pots are pretty good but I know of a couple that were modded with higher end sealed pots that feel as smooth as the TKD faders. If you want a super cool little mixer buy Wiz’s I’ll bet you buy another frame and more modules. Both manuals and Schematics are easy to find online. THX for this info.
So the Delta 200 go very cheap here in Germany. If I do not mod anything and just clean and recap myself do you think its still a good deal?
If you want a clean sounding console yes, but it always comes down to condition
|
|
|
Post by mrholmes on Jul 22, 2020 10:51:54 GMT -6
THX for this info.
So the Delta 200 go very cheap here in Germany. If I do not mod anything and just clean and recap myself do you think its still a good deal?
If you want a clean sounding console yes, but it always comes down to condition
The one I have in spot is delta 200 / 8 looks like it was touring a lot the frame is deformed at the psu conector. Seller says all channels are working condition looks very used and he wants just 150 bucks.
Other seller offers the same modell but / 16 in very good conditon @ 400 bucks.
Picking up for 150 does not sounds like a big risk to me.
|
|
|
Post by welliwonder on Jul 22, 2020 11:00:32 GMT -6
Nice info on the Delta. Our's is a 24 channel (16 mono + 4 stereo channels-2 of each stereo module) Jim Williams modded 8 buss with meter bridge and custom JW PSU. I absolutely love it! Every now and then something cuts out, and then I have to pop a module and clean up the ribbon connectors. Other than that, it's been solid and sounds incredible! Looks incredible with the new housing!
|
|
ericn
Temp
Balance Engineer
Posts: 14,935
|
Post by ericn on Jul 22, 2020 11:06:17 GMT -6
If you want a clean sounding console yes, but it always comes down to condition
The one I have in spot is delta 200 / 8 looks like it was touring a lot the frame is deformed at the psu conector. Seller says all channels are working condition looks very used and he wants just 150 bucks.
Other seller offers the same modell but / 16 in very good conditon @ 400 bucks.
Picking up for 150 does not sounds like a big risk to me.
At that price going in I would assume that it is going to have some issues, but I would probably bite! I mean there is nothing like a pleasant surprise!
|
|
ericn
Temp
Balance Engineer
Posts: 14,935
|
Post by ericn on Jul 22, 2020 11:11:38 GMT -6
Nice info on the Delta. Our's is a 24 channel (16 mono + 4 stereo channels-2 of each stereo module) Jim Williams modded 8 buss with meter bridge and custom JW PSU. I absolutely love it! Every now and then something cuts out, and then I have to pop a module and clean up the ribbon connectors. Other than that, it's been solid and sounds incredible! View AttachmentView Attachment That looks fantastic! Only thing I would have done differently is I personally would have gone with a wooden armrest that matches the side panels with a routed grove to hold an Apple keyboard pens ect.
|
|
|
Post by mrholmes on Jul 22, 2020 13:14:06 GMT -6
The one I have in spot is delta 200 / 8 looks like it was touring a lot the frame is deformed at the psu conector. Seller says all channels are working condition looks very used and he wants just 150 bucks.
Other seller offers the same modell but / 16 in very good conditon @ 400 bucks.
Picking up for 150 does not sounds like a big risk to me.
At that price going in I would assume that it is going to have some issues, but I would probably bite! I mean there is nothing like a pleasant surprise!
I bought it..
I hope its not too hard to pull out a module for recapping....
|
|
ericn
Temp
Balance Engineer
Posts: 14,935
|
Post by ericn on Jul 22, 2020 14:40:56 GMT -6
At that price going in I would assume that it is going to have some issues, but I would probably bite! I mean there is nothing like a pleasant surprise!
I bought it..
I hope its not too hard to pull out a module for recapping....
Pretty easy, first pry up the scribble strip, then remove a blank panel, make sure you remove all the retaining screws including any on the back of the blank panel. Then with a flat head gently pry up the front of the panel and wiggle it out. Next start with a module next to the blank panel do the same except once you can manipulate the little levers that hold the ribbon cable squeeze with one hand and pull the connector from the module. The good news is the console will still work with missing modules (well the master pulled will severely limit the functionality as will buss modules to some degree.
|
|
|
Post by svart on Jul 22, 2020 14:44:24 GMT -6
Thank you for the reply Wiz. As far as I know the LM4562 and LME49720 are the same chip with different names. So the additional component values should be the same. I shall send you a message about your Delta. That's true. There's actually about 5 different opamp models that are internally the same part, although I don't remember which ones they are anymore. TI had multiple OEM models of the same LM4562 parts in addition to the pro audio version and the general purpose version. TI confirmed at some point that there's no difference at all between them even though some audiophiles had previously sworn they heard a difference..
|
|
ericn
Temp
Balance Engineer
Posts: 14,935
|
Post by ericn on Jul 22, 2020 14:47:29 GMT -6
Thank you for the reply Wiz. As far as I know the LM4562 and LME49720 are the same chip with different names. So the additional component values should be the same. I shall send you a message about your Delta. That's true. There's actually about 5 different opamp models that are internally the same part, although I don't remember which ones they are anymore. TI had multiple OEM models of the same LM4562 parts in addition to the pro audio version and the general purpose version. TI confirmed at some point that there's no difference at all between them even though some audiophiles had previously sworn they heard a difference.. Come on you know the different numbers silk screen Ed on those parts made a Huge sonics difference!
|
|
|
Post by svart on Jul 22, 2020 14:49:18 GMT -6
One thing to keep in mind.. The channels in these are not capable of supporting higher speed opamps without mods. Do not think you can just pop new opamps on the boards and it'll be fine. They'll oscillate and even if they don't the layout and trace widths cannot support the increased current draw, especially on power up. Many people have had to add power switches to banks of channels and power up the unit in sequence or else the over-current protection kicks on in the power supply and the whole thing goes into shutdown.
A re-capping should be safe though.
|
|
|
Post by welliwonder on Jul 22, 2020 15:19:02 GMT -6
One thing to keep in mind.. The channels in these are not capable of supporting higher speed opamps without mods. Do not think you can just pop new opamps on the boards and it'll be fine. They'll oscillate and even if they don't the layout and trace widths cannot support the increased current draw, especially on power up. Many people have had to add power switches to banks of channels and power up the unit in sequence or else the over-current protection kicks on in the power supply and the whole thing goes into shutdown. A re-capping should be safe though. Luckily I hadn't planned on going wild with opamps! I mostly just wanted to do the Line Input and EQ sections. From what I've researched I'll need to add decoupling caps from the power pins to ground, and fb compensation caps where they are missing, in order to keep them stable. In looking at Wiz's photo, I noticed there is an additional feedback network across the voltage follower portion of the Line Input, so I was curious which value cap and resistor are being used. As for the added current draw of the new chips, I have a 24-Channel Venue II Theatre with a CPS-750 power supply. The user manual states this PSU was made for the 40-Channel version so I'm assuming it should be ok with the upgrades, but is there anything else I should be concerned about? Assuming it powers up fine, what impact would improper trace widths have on operation?
|
|
|
Post by mrholmes on Jul 22, 2020 15:40:45 GMT -6
One thing to keep in mind.. The channels in these are not capable of supporting higher speed opamps without mods. Do not think you can just pop new opamps on the boards and it'll be fine. They'll oscillate and even if they don't the layout and trace widths cannot support the increased current draw, especially on power up. Many people have had to add power switches to banks of channels and power up the unit in sequence or else the over-current protection kicks on in the power supply and the whole thing goes into shutdown. A re-capping should be safe though.
What is wrong with the orginal OP AMPS? Why do people want to change them?
|
|
|
Post by kcatthedog on Jul 22, 2020 15:48:21 GMT -6
I have a modded 200 16/4/2, with delta eq. I have had 2 sets of professional mods (Jim William and Skip outside Nashville, Creationaudio labs)) and have upgraded psu.
Prior to getting my last professional mods done, I had a significant in surge problem due to oscillations (a previous non pro mod and a few parts were the problem).
Chris(svart) was very helpful, giving my guidance and helping me to understand the possible sources of the problem, but I opted for having a number of modules professionally remodded, to ensure acceptable and high quality performance.
You sound like you do have some idea of what you are embarking on, but, no offence , as I have a few original module and 2 gens of professional mods , I am not certain that replacing a few parts per module is going to affect your sound quality and or reduce noise that much?
You might want to start with one and then do a tough blind a/b and see if you can reliably tell the difference by ear?
Skip was very thorough and provided me with multiple before and after sound/performance measurements, which reassured me about value for money.
But have fun with it too !
|
|
|
Post by mulmany on Jul 22, 2020 15:55:09 GMT -6
kcatthedogWhat if any difference is there between the JW and CAL mods? Just two different ways to get to the same result?
|
|
|
Post by kcatthedog on Jul 22, 2020 16:14:17 GMT -6
They are similar but, somewhat proprietary, as well, I believe Skip has designed his own op Amps, he is ex Harmon kardon, so very deep in his knowledge of the board, circuits etc.
I have tended not to discuss this too much, as I think both Jim and Skip do excellent work, but they are located in very different parts of the country, so shipping costs can factor in too?
|
|
|
Post by kcatthedog on Jul 22, 2020 16:24:54 GMT -6
Ps, I have zero power up, in surge problems now and required no additional switches, but what svart said above is true for many who have modded.
Skip told me exactly what part in the non professional mod was the cumulative source of my in surge problem, so we changed that out and also went with his mod/ op amps on 8 of my modules, so I have a few original, 2 gens of Jim’s mods and Skip’s.
I honestly like them all for different reasons and initially worried about what module was passing which signal and then kind of embraced the idea that my board actually has some different textures which adds to the mix: literally and figuratively.
I use my ob pres and comps for tracking to my symphony mkii 16x16, and use logic’s i/o plug in to hybrid mix send/receive from/to logic to ob comps by group and also send receive my 2 buss to Audioscape ssl and wa732eq inserts for its 3 band eq , filters and British transformers.
|
|
|
Post by welliwonder on Jul 22, 2020 18:36:05 GMT -6
kcatthedog no offense taken! I appreciate you taking the time to share your experience. I am always open to hearing and learning from others. What you said about having fun is the most important part. I find a lot of enjoyment in buying broken gear to fix for my studio. A challenge for the mind but easy on the budget! I've learned alot about synths in the past few years, but must admit this is my first foray into consoles. Hoping to apply some of those skills, along with a lot of research, toward fixing up the Soundcraft! By chance would you be willing to share what the source of the in surge problem was?
|
|
|
Post by svart on Jul 23, 2020 6:57:25 GMT -6
One thing to keep in mind.. The channels in these are not capable of supporting higher speed opamps without mods. Do not think you can just pop new opamps on the boards and it'll be fine. They'll oscillate and even if they don't the layout and trace widths cannot support the increased current draw, especially on power up. Many people have had to add power switches to banks of channels and power up the unit in sequence or else the over-current protection kicks on in the power supply and the whole thing goes into shutdown. A re-capping should be safe though.
What is wrong with the orginal OP AMPS? Why do people want to change them?
Most of the time there is nothing wrong with the opamps. People read through threads like this and it gives them the notion that they can easily get higher quality for less money by just changing a few parts, but they tend to overlook the rest of the story. Honestly, the biggest upgrade you can do is usually local decoupling. A few 100nF caps on the +/- V legs of each opamp will help the opamps work as the opamp manufacturer designed them to. A lot of lower end designs never included these local decoupling caps due to cost. The performance suffers, but in cheap gear that's not a thing they care about. Even the cheapest audio opamp like the 4558 is perfectly capable of reproducing audio into the 100KHz range with gain and into the MHz range at unity. There's no lack of bandwidth available to have the cleanest audio signal.
|
|
|
Post by svart on Jul 23, 2020 7:13:46 GMT -6
One thing to keep in mind.. The channels in these are not capable of supporting higher speed opamps without mods. Do not think you can just pop new opamps on the boards and it'll be fine. They'll oscillate and even if they don't the layout and trace widths cannot support the increased current draw, especially on power up. Many people have had to add power switches to banks of channels and power up the unit in sequence or else the over-current protection kicks on in the power supply and the whole thing goes into shutdown. A re-capping should be safe though. Luckily I hadn't planned on going wild with opamps! I mostly just wanted to do the Line Input and EQ sections. From what I've researched I'll need to add decoupling caps from the power pins to ground, and fb compensation caps where they are missing, in order to keep them stable. In looking at Wiz's photo, I noticed there is an additional feedback network across the voltage follower portion of the Line Input, so I was curious which value cap and resistor are being used. As for the added current draw of the new chips, I have a 24-Channel Venue II Theatre with a CPS-750 power supply. The user manual states this PSU was made for the 40-Channel version so I'm assuming it should be ok with the upgrades, but is there anything else I should be concerned about? Assuming it powers up fine, what impact would improper trace widths have on operation? The power traces on each channel PCB are long and thin. Think of them as flat wire, because that's really what PCB traces are. As you might already know, the thickness of a wire determines how much current it can handle, but what you might not know is that the length of the wire adds resistance and inductance into the equation. So, if you have very long and thin traces, the resistance is very high which means that it restricts current to the parts that need the current in a very fast fashion (called instantaneous current). Adding small local decoupling capacitors can help with this fast current, but then once they are depleted of extra charge, you still have to rely on the traces to supply continuous current to the parts that need it. When there's dozens of opamps demanding current through those same traces, the resistance causes them to starve for current. Adding larger caps near the parts can help with this, but those caps need to charge up initially too and can pull a lot of current at power up through those thin traces which causes the current at the power supply to spike to very high levels in a very short period of time, which is called "inrush current". Inrush current can be a lot higher than the nominal current needed to power a device. Let's say your mixer needs 1A to work properly, but when you power on, you might see an inrush current of 10A over a period of 1ms as everything charges up. I'm probably exaggerating the total inrush current in this example, but you get the idea. But then we haven't even considered inductance, which admittedly will be low in a straight trace, but it can cause fast currents to be more restricted further causing issues with opamps drawing currents quickly and can add a "kick" effect that adds to the inrush current. So it's not really about the power supply at all, but the traces on the PCB that determine a lot of the issues with these kinds of mods. Anyway, I wouldn't worry about going ahead and adding the small decoupling caps to the opamps, but I wouldn't go changing the opamps or even really adding a lot of bulk decoupling (big electrolytics) without modifying the power traces with extra wires or something.
|
|
ericn
Temp
Balance Engineer
Posts: 14,935
|
Post by ericn on Jul 23, 2020 9:35:21 GMT -6
What is wrong with the orginal OP AMPS? Why do people want to change them?
Most of the time there is nothing wrong with the opamps. People read through threads like this and it gives them the notion that they can easily get higher quality for less money by just changing a few parts, but they tend to overlook the rest of the story. Honestly, the biggest upgrade you can do is usually local decoupling. A few 100nF caps on the +/- V legs of each opamp will help the opamps work as the opamp manufacturer designed them to. A lot of lower end designs never included these local decoupling caps due to cost. The performance suffers, but in cheap gear that's not a thing they care about. Even the cheapest audio opamp like the 4558 is perfectly capable of reproducing audio into the 100KHz range with gain and into the MHz range at unity. There's no lack of bandwidth available to have the cleanest audio signal. Everything is built to a price point, it’s the way of the world. The Delta family was built to maximize price/ performance , the consensus at the time and today is for the $ the eked as much as they could. This was a pretty common console until the Mackie 1604 changed everything!
|
|
ericn
Temp
Balance Engineer
Posts: 14,935
|
Post by ericn on Jul 23, 2020 9:41:26 GMT -6
Luckily I hadn't planned on going wild with opamps! I mostly just wanted to do the Line Input and EQ sections. From what I've researched I'll need to add decoupling caps from the power pins to ground, and fb compensation caps where they are missing, in order to keep them stable. In looking at Wiz's photo, I noticed there is an additional feedback network across the voltage follower portion of the Line Input, so I was curious which value cap and resistor are being used. As for the added current draw of the new chips, I have a 24-Channel Venue II Theatre with a CPS-750 power supply. The user manual states this PSU was made for the 40-Channel version so I'm assuming it should be ok with the upgrades, but is there anything else I should be concerned about? Assuming it powers up fine, what impact would improper trace widths have on operation? The power traces on each channel PCB are long and thin. Think of them as flat wire, because that's really what PCB traces are. As you might already know, the thickness of a wire determines how much current it can handle, but what you might not know is that the length of the wire adds resistance and inductance into the equation. So, if you have very long and thin traces, the resistance is very high which means that it restricts current to the parts that need the current in a very fast fashion (called instantaneous current). Adding small local decoupling capacitors can help with this fast current, but then once they are depleted of extra charge, you still have to rely on the traces to supply continuous current to the parts that need it. When there's dozens of opamps demanding current through those same traces, the resistance causes them to starve for current. Adding larger caps near the parts can help with this, but those caps need to charge up initially too and can pull a lot of current at power up through those thin traces which causes the current at the power supply to spike to very high levels in a very short period of time, which is called "inrush current". Inrush current can be a lot higher than the nominal current needed to power a device. Let's say your mixer needs 1A to work properly, but when you power on, you might see an inrush current of 10A over a period of 1ms as everything charges up. I'm probably exaggerating the total inrush current in this example, but you get the idea. But then we haven't even considered inductance, which admittedly will be low in a straight trace, but it can cause fast currents to be more restricted further causing issues with opamps drawing currents quickly and can add a "kick" effect that adds to the inrush current. So it's not really about the power supply at all, but the traces on the PCB that determine a lot of the issues with these kinds of mods. Anyway, I wouldn't worry about going ahead and adding the small decoupling caps to the opamps, but I wouldn't go changing the opamps or even really adding a lot of bulk decoupling (big electrolytics) without modifying the power traces with extra wires or something. I haven’t been inside one for years but if my memory is correct the power runs through the ribbon cable. This only adds to everything referenced above. It’s a pain in the ass but if you can by pass the ribbon for power and ground while still utilizing some easy higher current disconnects you can make a big improvement in just about any console!
|
|
|
Post by welliwonder on Jul 23, 2020 14:17:09 GMT -6
Luckily I hadn't planned on going wild with opamps! I mostly just wanted to do the Line Input and EQ sections. From what I've researched I'll need to add decoupling caps from the power pins to ground, and fb compensation caps where they are missing, in order to keep them stable. In looking at Wiz's photo, I noticed there is an additional feedback network across the voltage follower portion of the Line Input, so I was curious which value cap and resistor are being used. As for the added current draw of the new chips, I have a 24-Channel Venue II Theatre with a CPS-750 power supply. The user manual states this PSU was made for the 40-Channel version so I'm assuming it should be ok with the upgrades, but is there anything else I should be concerned about? Assuming it powers up fine, what impact would improper trace widths have on operation? The power traces on each channel PCB are long and thin. Think of them as flat wire, because that's really what PCB traces are. As you might already know, the thickness of a wire determines how much current it can handle, but what you might not know is that the length of the wire adds resistance and inductance into the equation. So, if you have very long and thin traces, the resistance is very high which means that it restricts current to the parts that need the current in a very fast fashion (called instantaneous current). Adding small local decoupling capacitors can help with this fast current, but then once they are depleted of extra charge, you still have to rely on the traces to supply continuous current to the parts that need it. When there's dozens of opamps demanding current through those same traces, the resistance causes them to starve for current. Adding larger caps near the parts can help with this, but those caps need to charge up initially too and can pull a lot of current at power up through those thin traces which causes the current at the power supply to spike to very high levels in a very short period of time, which is called "inrush current". Inrush current can be a lot higher than the nominal current needed to power a device. Let's say your mixer needs 1A to work properly, but when you power on, you might see an inrush current of 10A over a period of 1ms as everything charges up. I'm probably exaggerating the total inrush current in this example, but you get the idea. But then we haven't even considered inductance, which admittedly will be low in a straight trace, but it can cause fast currents to be more restricted further causing issues with opamps drawing currents quickly and can add a "kick" effect that adds to the inrush current. So it's not really about the power supply at all, but the traces on the PCB that determine a lot of the issues with these kinds of mods. Anyway, I wouldn't worry about going ahead and adding the small decoupling caps to the opamps, but I wouldn't go changing the opamps or even really adding a lot of bulk decoupling (big electrolytics) without modifying the power traces with extra wires or something. Thank you for that wealth of information svart. It's got me curious now if I could calculate the required trace width and compare it to the actual width on the modules. Would something like this be a suitable way to do so, assuming I knew the parameters? www.digikey.com/en/resources/conversion-calculators/conversion-calculator-pcb-trace-widthI know I could measure the trace thickness and length, but is there a way to calculate the current that would be running through it?
|
|
|
Post by welliwonder on Jul 23, 2020 14:17:28 GMT -6
The power traces on each channel PCB are long and thin. Think of them as flat wire, because that's really what PCB traces are. As you might already know, the thickness of a wire determines how much current it can handle, but what you might not know is that the length of the wire adds resistance and inductance into the equation. So, if you have very long and thin traces, the resistance is very high which means that it restricts current to the parts that need the current in a very fast fashion (called instantaneous current). Adding small local decoupling capacitors can help with this fast current, but then once they are depleted of extra charge, you still have to rely on the traces to supply continuous current to the parts that need it. When there's dozens of opamps demanding current through those same traces, the resistance causes them to starve for current. Adding larger caps near the parts can help with this, but those caps need to charge up initially too and can pull a lot of current at power up through those thin traces which causes the current at the power supply to spike to very high levels in a very short period of time, which is called "inrush current". Inrush current can be a lot higher than the nominal current needed to power a device. Let's say your mixer needs 1A to work properly, but when you power on, you might see an inrush current of 10A over a period of 1ms as everything charges up. I'm probably exaggerating the total inrush current in this example, but you get the idea. But then we haven't even considered inductance, which admittedly will be low in a straight trace, but it can cause fast currents to be more restricted further causing issues with opamps drawing currents quickly and can add a "kick" effect that adds to the inrush current. So it's not really about the power supply at all, but the traces on the PCB that determine a lot of the issues with these kinds of mods. Anyway, I wouldn't worry about going ahead and adding the small decoupling caps to the opamps, but I wouldn't go changing the opamps or even really adding a lot of bulk decoupling (big electrolytics) without modifying the power traces with extra wires or something. I haven’t been inside one for years but if my memory is correct the power runs through the ribbon cable. This only adds to everything referenced above. It’s a pain in the ass but if you can by pass the ribbon for power and ground while still utilizing some easy higher current disconnects you can make a big improvement in just about any console! The power and ground connections do run through the ribbon cable, and on my console there are also spade connectors with separate ground wires that run to a star point on the chassis. There is one wire placed on every 5th or 6th module. Would there be any benefit to installing one on every module?
|
|
|
Post by ragan on Jul 23, 2020 14:23:00 GMT -6
The power traces on each channel PCB are long and thin. Think of them as flat wire, because that's really what PCB traces are. As you might already know, the thickness of a wire determines how much current it can handle, but what you might not know is that the length of the wire adds resistance and inductance into the equation. So, if you have very long and thin traces, the resistance is very high which means that it restricts current to the parts that need the current in a very fast fashion (called instantaneous current). Adding small local decoupling capacitors can help with this fast current, but then once they are depleted of extra charge, you still have to rely on the traces to supply continuous current to the parts that need it. When there's dozens of opamps demanding current through those same traces, the resistance causes them to starve for current. Adding larger caps near the parts can help with this, but those caps need to charge up initially too and can pull a lot of current at power up through those thin traces which causes the current at the power supply to spike to very high levels in a very short period of time, which is called "inrush current". Inrush current can be a lot higher than the nominal current needed to power a device. Let's say your mixer needs 1A to work properly, but when you power on, you might see an inrush current of 10A over a period of 1ms as everything charges up. I'm probably exaggerating the total inrush current in this example, but you get the idea. But then we haven't even considered inductance, which admittedly will be low in a straight trace, but it can cause fast currents to be more restricted further causing issues with opamps drawing currents quickly and can add a "kick" effect that adds to the inrush current. So it's not really about the power supply at all, but the traces on the PCB that determine a lot of the issues with these kinds of mods. Anyway, I wouldn't worry about going ahead and adding the small decoupling caps to the opamps, but I wouldn't go changing the opamps or even really adding a lot of bulk decoupling (big electrolytics) without modifying the power traces with extra wires or something. Thank you for that wealth of information svart. It's got me curious now if I could calculate the required trace width and compare it to the actual width on the modules. Would something like this be a suitable way to do so, assuming I knew the parameters? www.digikey.com/en/resources/conversion-calculators/conversion-calculator-pcb-trace-widthI know I could measure the trace thickness and length, but is there a way to calculate the current that would be running through it? Ohm's Law!
|
|
ericn
Temp
Balance Engineer
Posts: 14,935
|
Post by ericn on Jul 23, 2020 14:34:32 GMT -6
I haven’t been inside one for years but if my memory is correct the power runs through the ribbon cable. This only adds to everything referenced above. It’s a pain in the ass but if you can by pass the ribbon for power and ground while still utilizing some easy higher current disconnects you can make a big improvement in just about any console! The power and ground connections do run through the ribbon cable, and on my console there are also spade connectors with separate ground wires that run to a star point on the chassis. There is one wire placed on every 5th or 6th module. Would there be any benefit to installing one on every module? On my DDA I noticed a bit less noise when I used the spades on everything module to connect to the ground bar using 12ga.
|
|