I've a question about the input capacitor for elliot's p3a. It's supposed to be a 4.7uF capacitor. Now, in a guide somewhere i read its supposed to be a di-electric (preferably) polypropylene/polystyrene
On digikey (where i'm getting the rest of my parts) the ony thing that come up w/ dielectric are ceramic caps. Also polypropylene/polystyrene only go up to 2.2uF i believe (and their physical size is quite large, so 2 wouldn't fit on the board ..).
Anyway, any comments as to which i should use (preferably the digikey part number).
Thanks.
would this one work (part number: 495-1131-ND)?
It does say in the data sheet its a dielectric.
http://ca.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=155228&Row=110246&Site=CA
On digikey (where i'm getting the rest of my parts) the ony thing that come up w/ dielectric are ceramic caps. Also polypropylene/polystyrene only go up to 2.2uF i believe (and their physical size is quite large, so 2 wouldn't fit on the board ..).
Anyway, any comments as to which i should use (preferably the digikey part number).
Thanks.
would this one work (part number: 495-1131-ND)?
It does say in the data sheet its a dielectric.
http://ca.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=155228&Row=110246&Site=CA
4.7 uF polypropylene is quite common...a search would do the trick.
If im not mistaken Farnell got some.
Magura🙂
If im not mistaken Farnell got some.
Magura🙂
Hi!
The digikey item you've selected would work for you. It is a MKT cap, which is considered inferior to types like MKP.
But MKP (preferred) or FKP are bigger than MKT/MKS caps.
For me, preferred order would be:
Polarized elko, bipolar elko, ceramics, MKS, MKT, MKP, FKP, Mica (and maybe paper-in-oil caps)
But FKP and Mica should be out of question (not in production in the needed value range, or way too expensive and too big).
You could even omit the input cap, if you've got no DC-offset from your pre-amp / source (but always check, otherwise you could destroy your speakers).
Oh, and the size does not really matter. I am using pretty big Mundorf caps, mounted "outside" of the PCB (you can always try using caps intended for loudspeaker XO designs, since they often have lower voltage ratings, and therefore are smaller).
Or get polarized BlackGate elkos, like a lot of people do for their GainClones...
Hope this helped,
Arndt
The digikey item you've selected would work for you. It is a MKT cap, which is considered inferior to types like MKP.
But MKP (preferred) or FKP are bigger than MKT/MKS caps.
For me, preferred order would be:
Polarized elko, bipolar elko, ceramics, MKS, MKT, MKP, FKP, Mica (and maybe paper-in-oil caps)
But FKP and Mica should be out of question (not in production in the needed value range, or way too expensive and too big).
You could even omit the input cap, if you've got no DC-offset from your pre-amp / source (but always check, otherwise you could destroy your speakers).
Oh, and the size does not really matter. I am using pretty big Mundorf caps, mounted "outside" of the PCB (you can always try using caps intended for loudspeaker XO designs, since they often have lower voltage ratings, and therefore are smaller).
Or get polarized BlackGate elkos, like a lot of people do for their GainClones...
Hope this helped,
Arndt
We have been through this for decades! If you want the 'best' then only teflon will do, next is polystyrene, then polypropylene, then polycarbonate, then down the road, is mylar. Significant DA is the most important difference.
Cradle22 said:
that was the answer i was looking for, thank you 🙂
btw, in my gc i'm using a BG cap ..
Magura: That's why I specified digikey .. i know i can get it from other places, but when you have to pay $10+ for shipping from each source, you want to have as few sources as possible (it'll turn out to be 1 in my case .. just digikey, which is only $8 in shipping charges)
I don't want to order from newark just for one cap if i don't have to ..
Elizard,
The cap you identified has 15mm lead spacing, you need a box cap with 5mm lead spacing.
The Epcos 50v 3.3uF will work and fit fine. That'll give you an F3 of 2hz, so you shouldn't lose any LF performance 😉
Cheers,
M
The cap you identified has 15mm lead spacing, you need a box cap with 5mm lead spacing.
The Epcos 50v 3.3uF will work and fit fine. That'll give you an F3 of 2hz, so you shouldn't lose any LF performance 😉
Cheers,
M
Ok, another question. For the cap/resistor connected in the mains in the following image, is it a connection that's between live/neutral? As well, does the resistor have to be any significant wattage, or just a simple 1/4watt?
http://sound.westhost.com/p3a-f2.gif
Also, is there a benefic to actually using the resistor/cap across the live/neutral? What is it?
oh yeah, and how "risky" would it be to use 35V capacitors in the power supply (i've some 33000uF lying around)? The rails should be around 30-32V (my transformer is 22v secondaries)?
http://sound.westhost.com/p3a-f2.gif
Also, is there a benefic to actually using the resistor/cap across the live/neutral? What is it?
oh yeah, and how "risky" would it be to use 35V capacitors in the power supply (i've some 33000uF lying around)? The rails should be around 30-32V (my transformer is 22v secondaries)?
I honestly can't recommend 35V types for this Power Supply. They are rated to 35V DC with no ripple. With the ripple coming out of the bridge (full wave rectified AC) the cap will be operating outside it's rating and will probably suffer overheating problems, leakage and even failure.
Digikey
I would not use resistor or signal capacitor purchased from Digikey. The Resistors metal film resistors have non-ferrous metal leads and the signal caps are not so hot either. Their power supply and decoupling caps or OK.
Checkout http://www.percyaudio.com/Catalog.pdf he sales the some of the best caps, many different bands and all types of films.
For resistors buy type RN55D or RN60D by Vishay, Reliable Capacitors or great just stay way from Solen.
www.mouser.com sales vishay resistors
I would not use resistor or signal capacitor purchased from Digikey. The Resistors metal film resistors have non-ferrous metal leads and the signal caps are not so hot either. Their power supply and decoupling caps or OK.
Checkout http://www.percyaudio.com/Catalog.pdf he sales the some of the best caps, many different bands and all types of films.
For resistors buy type RN55D or RN60D by Vishay, Reliable Capacitors or great just stay way from Solen.
www.mouser.com sales vishay resistors
Re: Digikey
When you're strapped for cash, ordering for a few different places means big $$$, so i don't have that option (and being a student, i'm always strapped for cash).
That's why i specified everything be from digikey.
Also, digikey is nice b/c all the customs and taxes are included in the price automatically.
jewilson said:
When you're strapped for cash, ordering for a few different places means big $$$, so i don't have that option (and being a student, i'm always strapped for cash).
That's why i specified everything be from digikey.
Also, digikey is nice b/c all the customs and taxes are included in the price automatically.
Not living North of the US I do not normally think about that problem. However, I just do not like to lower quality parts knowing that I will want to rebuild the hardware later and that always happens.
Grab a magnet and run it over you Digikey metal film resistors, it should not pick them up if the lead is truly non-ferrous metal. The lead material will end up degrading the sound. In addition, the Vishay RN55D or 60D are cheap from Mouser.
As for as caps use polystyrene, then polypropylene Teflon is very expensive. beware that all film cap are not created equal just there polypropylene.
Grab a magnet and run it over you Digikey metal film resistors, it should not pick them up if the lead is truly non-ferrous metal. The lead material will end up degrading the sound. In addition, the Vishay RN55D or 60D are cheap from Mouser.
As for as caps use polystyrene, then polypropylene Teflon is very expensive. beware that all film cap are not created equal just there polypropylene.
Re the P3A input cap: any variety of metal film that will fit in the holes and which has the right value will function. To the extent there is a resulting tonal difference it will bw minor. Most of us won't hear it even if its there. A bipolar electroltic would work too, but you want the lowersr ESR you can get - one way to get it is to go with higher working voltages.
Just to see if I could, I once used two 22uF tantalum caps with ploarity back to back - the two negative leads were soldered together the air. Ugly but it sounded just like a second P3A that used a metel poly cap. The point is that there is a certain latitude in how you do this.
An other consideration is the the capacitance value. The lower the value the higher the roll of frequency. 4.7uF is fine for most purposes, but if really need the amp flat down to 20Hz, 10uF is a better choice. You can go higher but its kind of pointless. By the same token, if these amps are going to power small or moderatly sized satellite speakers that go with a sub, 2.2uF is fine and it will be easier to find one that fits on the board.
Just to see if I could, I once used two 22uF tantalum caps with ploarity back to back - the two negative leads were soldered together the air. Ugly but it sounded just like a second P3A that used a metel poly cap. The point is that there is a certain latitude in how you do this.
An other consideration is the the capacitance value. The lower the value the higher the roll of frequency. 4.7uF is fine for most purposes, but if really need the amp flat down to 20Hz, 10uF is a better choice. You can go higher but its kind of pointless. By the same token, if these amps are going to power small or moderatly sized satellite speakers that go with a sub, 2.2uF is fine and it will be easier to find one that fits on the board.
Electrolytic cap work best at 80% of there working value. Most cap are underated and will work at their rated voltage. Having said that I have had some several premature failures runing electrolytic at there maximum working voltage bit only after years of operation.
If you use an electrolytic at say like 35% of it rated voltage you will lose volume and performance for the cap. This does not seem to be true for film caps.
If you use an electrolytic at say like 35% of it rated voltage you will lose volume and performance for the cap. This does not seem to be true for film caps.
Yep, that should be OK
A while back when I worked at TI one of the inspection processes used was to check the leads with a magnet. These resistors with non-ferrous metal leads can increase distortions, of course in some location they will not.
A while back when I worked at TI one of the inspection processes used was to check the leads with a magnet. These resistors with non-ferrous metal leads can increase distortions, of course in some location they will not.
This won't helpyou much, but I struggle with the same thing --trying to get everything on one order. Usually digikey is the best option, but sometimes it's mouser.
sam9 said:
yeah, i'm trying to set up the mouser order right now
i can get everything from digikey no problem, i already have my order made up
but, i guess i'll do a mouser order, and compare the prices ..
i'm also using vishay/dale resistors, so .. we'll see 🙂
if the prices are close, then i'll go mouser, if they're off by more than about $15-20, then i've no choice but to go with the cheaper.
the digikey order, btw (excluding the PS caps which i have at home) is about $60 🙂
although i do like the no-minimum quantities w/ mouser (on the items i saw so far)
- Status
- Not open for further replies.