Consider that 3W and up metalfilm resistors are 5% accurate, as the Pana ECG type that's used by most.
Means your DMM can read a lower bias, but the actual idle current is higher than scheduled. (unless you measured the drain resistors)
Metalplate meanderband drain/collector resistors, the common white blocks in Asian power amps, usually have an accuracy of 10%.
Hi Steve,
Consider Canare's star quad 4S11. It uses 4 runs of 14g. You can leave one run unterminated for shielding.
Speaker Cable at Blue Jeans Cable
Umbillical
Hey alazira,
Thanks for the heads up.
I have no problem with 4 conductors. But, I was hoping to find a cable with an outer shield.
Parts Express has 3 conductor power cables in different gauges at reasonable prices. But, none had an outer shield. The only one they have with an outer shield is a 12 gauge teflon one. And that one is very expensive.
Thanks,
Steve
Hey alazira,
Thanks for the heads up.
I have no problem with 4 conductors. But, I was hoping to find a cable with an outer shield.
Parts Express has 3 conductor power cables in different gauges at reasonable prices. But, none had an outer shield. The only one they have with an outer shield is a 12 gauge teflon one. And that one is very expensive.
Thanks,
Steve
Steve, you can also ground one end of that extra cable which will help shield even more. Leave the other end hanging.
Umbillical
Hey udailey,
I could try that. But wouldn't it be better to find a cable with an outer shield? Wouldn't that give better shielding than grounding the extra conductor of a 4 conductor cable?
Thanks,
Steve
Hey udailey,
I could try that. But wouldn't it be better to find a cable with an outer shield? Wouldn't that give better shielding than grounding the extra conductor of a 4 conductor cable?
Thanks,
Steve
Hi Steve,
If you really want an outer shield you can use metal mesh sleeves
McMaster-Carr
You can use it with 3 conductor cables, just ground one end.🙂
What he means is leave one of the conductors unterminated (i.e. you will have 2 wires connected to the ground on one end and only one connected at the other). It will act as a shield. Shields don't work if you have them grounded on both ends.
As far as 4 conductor vs 3+mesh, the mesh will be slightly better.
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I thought it would be safer to use outer shield with F5, in repect to "noise sensibility", but maybe I have misunderstood
If you dont like to use the shield fore signal you can do a pseudo balanced cable, which was common in the old days
Its a 2 conductor with outer shield
Outer shield is electrically connected in one end only
I have always found it best to connect the shielded end to preamp
If you dont like to use the shield fore signal you can do a pseudo balanced cable, which was common in the old days
Its a 2 conductor with outer shield
Outer shield is electrically connected in one end only
I have always found it best to connect the shielded end to preamp
Hi Tinitus,
He's talking about power connectors, for which shielding is usually less of an issue. For signal I have found that a mesh shield works better than a tightly braided shield wire.
Umbillical
Thanks alazira,
Gottcha -- and thanks for the link. I'll take a look at the outer shield braids.
Steve
Thanks alazira,
Gottcha -- and thanks for the link. I'll take a look at the outer shield braids.
Steve
Oh 😱 thanks
Too little time to read these days, I must learn that 😉
Anyway, someone once said that shielded mains wire was a nono, but now ...😕
Umbillical
Hey Tinitus,
I wans't talking about the mains either. I was talking about the cable that would run between the power supply case and the amp case -- if I used a separate box for the power supply and a separate box for the amplifier.
However, I was going to use a shielded cable for the mains as well. I do not know the pros and cons of this. But, I did have a 5 foot section of shielded cable lying around that I was going to use for the mains.
Steve
Hey Tinitus,
I wans't talking about the mains either. I was talking about the cable that would run between the power supply case and the amp case -- if I used a separate box for the power supply and a separate box for the amplifier.
However, I was going to use a shielded cable for the mains as well. I do not know the pros and cons of this. But, I did have a 5 foot section of shielded cable lying around that I was going to use for the mains.
Steve
I once used 4core shielded to take the mains from the back of the IEC socket to the 2pole switch at the front of the chassis to try to improve the hum performance of an amp. It made absolutely no difference.
I now know that I knew nothing about bad grounding way back then.
I now know that I knew nothing about bad grounding way back then.
bobbodioulasso --
If I was to go that route, then the next step would be to get up the pole and shield the drop line coming into my house -- I'm kidding of course.
Andtew T -- I have no idea if shielding is going to make a difference or not. Conceptually it seems to make sense. But in reality it may make no audible difference. The mains cable I had lying around. So, I figured I'd try it. However, my assumption is that after the transformers it may start to yield improvements. I would think that picking up noise in the umbillical ( at a point after most of the supply filtering) might be heard. So shielding at that point may be beneficial. But again, I have no practical experience.
Steve
If I was to go that route, then the next step would be to get up the pole and shield the drop line coming into my house -- I'm kidding of course.
Andtew T -- I have no idea if shielding is going to make a difference or not. Conceptually it seems to make sense. But in reality it may make no audible difference. The mains cable I had lying around. So, I figured I'd try it. However, my assumption is that after the transformers it may start to yield improvements. I would think that picking up noise in the umbillical ( at a point after most of the supply filtering) might be heard. So shielding at that point may be beneficial. But again, I have no practical experience.
Steve
if you do go for separate PSU and amp chassis then I suggest the rough smoothing be done in the PSU box. Fit the secondary smoothing right next to the amplifier power terminals. This creates an rCrC type power supply, not quite as good as RCRC, but certainly better than rC which most builders use.
The transformer and rectifier resistances are the first "r", the umbilical cable is the second "r". It is obvious that really thick umbilical wires defeats the benefit of creating the rCrC. Use a double thickness or more for the ground link and use another dedicated wire for the Safety Earth. You are now up to 5core in the umbilical.
The transformer and rectifier resistances are the first "r", the umbilical cable is the second "r". It is obvious that really thick umbilical wires defeats the benefit of creating the rCrC. Use a double thickness or more for the ground link and use another dedicated wire for the Safety Earth. You are now up to 5core in the umbilical.
long wires are often trouble in power amps
Short answer, don't do it.
16ga is way too small even in the same box, imo.
The long PS wiring increases the potential for parasitics and RFI pick up. I would be concerned about the Vdrop from the longish runs, and the effect on the hum & noise floor.
Otoh, if you don't care about these things, it will likely function as an amplifier, but probably not quite optimal.
YMMV.
_-_-bear
Short answer, don't do it.
16ga is way too small even in the same box, imo.
The long PS wiring increases the potential for parasitics and RFI pick up. I would be concerned about the Vdrop from the longish runs, and the effect on the hum & noise floor.
Otoh, if you don't care about these things, it will likely function as an amplifier, but probably not quite optimal.
YMMV.
_-_-bear
Andrew --
Actually, I was going to do CLC in the PS box. Then I was going to add a final (of lesser value capacitance) bank of caps close to th eamp board in the amp case. So, ther should be CLCrc (I think).
I was thinking of just running a seperate safety earth wire between the two chassis. This way the Umbillical would only be 4 conductor if I doubled up on the ground (or 3 conductor if I did not doubleup on the ground).
How does all that sound?
Steve
Actually, I was going to do CLC in the PS box. Then I was going to add a final (of lesser value capacitance) bank of caps close to th eamp board in the amp case. So, ther should be CLCrc (I think).
I was thinking of just running a seperate safety earth wire between the two chassis. This way the Umbillical would only be 4 conductor if I doubled up on the ground (or 3 conductor if I did not doubleup on the ground).
How does all that sound?
Steve
the last C must be big.
It has to deliver the transient current demand and that can be enormous.
so you have CLCrCC
The last CC determines the audio quality, that's where to spend the money. I believe the two earlier C & C have little effect on the audio quality
It has to deliver the transient current demand and that can be enormous.
so you have CLCrCC
The last CC determines the audio quality, that's where to spend the money. I believe the two earlier C & C have little effect on the audio quality
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