anyone know where i can get a 5k P/P DPDT?

[daz]

A 5k push/pull pot with a DPDT switch? I know they make those ones you can get most anywhere for guitars in 250 and 500k, but i need a 5k. Last one i had to make from one of those and the resistive part of a 5k pot of the same size. But it was a real PITA, so i'd like to avoid that route this time if i can.

[jrfrond]

Mouser Electronics

Part#: 313-1601F-5K

[daz]

I usually stay away from mouser, but in this case it's one of the only places i'd probably find such a unlikely pot. Anyways, i ordered it. Thanks.

[Chuck H]

I usually stay away from mouser.

Why?

I buy from them all the time. But if there's some reason not to (moral? environment?) I'd like to know.

Chuck

[jrfrond]

I'd like to know why too. I've been purchasing from Mouser for over 15 years. Great customer service, great products, very comprehensive catalog. Nothing wrong with their pots either. Probably one of the best off-the-shelf selections of pots anywhere.

[daz]

Because i recall trying to buy parts there before and the shipping costs seemed high for small parts. Didn't seem to bad now, so maybe they changed it. Tho the ship was still almost double the part. But like i said it was a hard part to find.

[Enzo]

The minimal shipping is going to be a pound, and that could be a pound roll of solder or one tiny transistor. I can count on shipping being something like $8 minimum. If I order $2 worth of parts that seems large, but for the same money I can also ship $200 worth of semiconductors.

[jrfrond]

Shipping is shipping. Mouser has two warehouse, one in NJ and the other in TX, so it is what it is. They charge the going rates for whichever method you choose. One-zy Two-zy orders are going to have a large shipping to materials cost ratio, but like Enzo said, a pound is a pound. Since you seem like you might need this pot again, I suggest ordering 10 pieces to get second-column pricing, which is $.63 cheaper than first column, and next time you will have it on hand.

One of the tricks that people like Enzo and myself who manage and/or own shops use when ordering small parts is to order a bunch a lower cost. For instance, if we need a particular resistor for a repair that we don't have, I am likely to order a hundred or even a thousand, at a fraction of the cost each for a single. With pots, I will generally order second-column, which is usually 10-99 pieces.

[Enzo]

Yes, I have mentioned this before. With something like resistors, look at the 100 lot price versus individual resistors. The price tends to drop like a stone. ANd unless you are doing one amp project and never more, things like 100k, 1.5k, 220k, 1 meg, and a few other values will come up again and again and again in tube amps. When 100 resistors of a value costs only a dollar or two, why not?

ANy time I order some commodity part, if it is something I think I might need again, I always order more than the immediate need.

[Chuck H]

I always have a supply of caps and resistors (of the type and make I like to build with) in the common values for many guitar amps as well as the values I most often use for my own circuits or tweaking. But it still seems like I need to order something every time I build or proto something. Still, it's a big time saver because I usually have enough parts to keep me busy while I wait for my new order to arrive. No down time.

Also, since I know what componants I go through the most I keep more of those on hand. I mean, you can use 10 or 15 1M 1/2 watt resistors in one amp if it's a complex circuit. So I always take an inventory before I place my order for the needed part and restock at the same time. I don't build much but I've been doing it awhile. So no one order is ever that expensive and I add stock to my drawers 10 to 30 pieces at a time.

FWIW the parts I usually end up needing are the filter caps. I like to get them fresh since I've had problems with them getting old hangin around. That was before I knew that they actually have a shelf life. I've never tried to reform caps, but I should figure it out and do it for each build regardless of when I buy the caps (since you never can know how old they are).

Point is...It's not as hard as it seems to keep a running inventory of parts and save on shipping. Even for a small time tweaker like me.

Chuck

[pvsage]

Here's a couple pages about reforming electrolytic capacitors:
http://www.nmr.mgh.harvard.edu/~reese/electrolytics/
http://www.vmars.org.uk/capacitor_reforming.htm

By the way, those little cathode bypass caps also deform when sitting on the shelf, but I'd wager that they safely (if s l o w l y) reform at the low voltage across them.

[Chuck H]

By the way, those little cathode bypass caps also deform when sitting on the shelf, but I'd wager that they safely (if s l o w l y) reform at the low voltage across them.

Thanks for the links. I'll check it out. I've always known the info was "out there" I just haven't had enough trouble using newly bought caps to look into it yet.

As far as preamp tube bypass caps, I like to use dry tants, so no worries there. I saw them in a Messy Booger once and thought it was a good idea. I actually don't like Boogers but I do think the tants sound better than the common aluminum caps. Also, I've been doing this long enough that I've had to recap several builds for myself and friends. On the amps with tantalums I don't trouble with the preamp. It's nice when it comes up.

Chuck

[jrfrond]

Tantalum caps are amongst the most problem-ridden type there is, if not THE most. They just love to short and change value. Personally, I'd steer clear of them for reliability's sake.

[Enzo]

I agree, the only advantage they offer is their small size for a given value. And that hardly matters in a tube amp.

Tantalums have ZERO tolerance for reverse voltage.

I generally replace failed ones with something else.

[Chuck H]

the only advantage they offer is their small size for a given value.

C'mon, thats not exactly true. Tants do have the advantage of much lower ESR and longer life. You also don't need to worry about how long they've been sitting around before YOU got them because there's no electrolyte crystalyzing.

But I wasn't aware that they have a higher failure rate. If the guys who do repairs say it's so, then I believe it.

I said that I think they sound better. Well...Lets face it. In a preamp bypass cap application where the circuit uses a 1000 ohm cathode R a few ohms of ESR probably can't be heard. But it seemed like a good idea at the time.

I haven't had any failures yet. I'll have to open up one of my older builds and see if there's any value drift. But perhaps I'll switch back to aluminum anyway. I was just reading the specs for some newer Nichicon aluminums that have a very low impedance and a life expectancy of 6000 hours!

Thanks for the heads up.

Chuck