Are RV4 pots necessary?

[kseely]

All the circuits I put together use coupling caps, so there isn't a
constant current going through any of the pots, unless a cap fails and
leaks DC. I keep looking for RV4 (2 watt) pots and paying a small
fortune for them. I even settle for linear instead of audio when I
can't get audio taper.

One local store says they'll order them from Mexico, but they cost
hundreds of dollars per pound. I forget the figure he quoted but he was
talking "ounces" and when I went home and weighed them I figured I'd
need a few pounds a year. I don't care if they're "realy, REALY good
stuff" that's just too much to pay for potentiometers.

So can I use the cheapies in Mouser's catalogue? What is the lowest
wattage you'd recommend? I won't be using these for bias adjustments,
but if a cap *does* fail should the pots be RV4 rated?

Karl

[Mark]

"kseely" > wrote in message . com>...
> All the circuits I put together use coupling caps, so there isn't a
> constant current going through any of the pots, unless a cap fails and
> leaks DC. I keep looking for RV4 (2 watt) pots and paying a small
> fortune for them. I even settle for linear instead of audio when I
> can't get audio taper.
>
> One local store says they'll order them from Mexico, but they cost
> hundreds of dollars per pound. I forget the figure he quoted but he was
> talking "ounces" and when I went home and weighed them I figured I'd
> need a few pounds a year. I don't care if they're "realy, REALY good
> stuff" that's just too much to pay for potentiometers.
>
> So can I use the cheapies in Mouser's catalogue? What is the lowest
> wattage you'd recommend? I won't be using these for bias adjustments,
> but if a cap *does* fail should the pots be RV4 rated?
>
> Karl

The advantage of the 2 watt pots is the larger capacity in power they
will handle. I know they are not commonly used in circuits where there
is power involved, e.g. volume, tone, etc. For bias and hum balance,
the additional power capacity is needed. The best thing about the 2
watt pots is that they are sealed, no dirty contacts. They are also
much better constructed than cheap ones. I will use them in circuits I
build to ensure better quality. The rotation feel of them is also
noticed even when one cannot see the pot. I know Allied caries the
pots. The military versions are the best to get. Ohmite A/B, and
Clarostat make these pots and one is as good as the other. The cheap
pots are used in mass production only because of cost reduction. The
cheap pots are 1/2 watt for linear and 1/4 watt for audio taper.

[Brian McAllister]

On 9 Nov 2004 21:07:14 -0800, (Mark)
wrote:

>"kseely" > wrote in message . com>...
>> All the circuits I put together use coupling caps, so there isn't a
>> constant current going through any of the pots, unless a cap fails and
>> leaks DC. I keep looking for RV4 (2 watt) pots and paying a small
>> fortune for them. I even settle for linear instead of audio when I
>> can't get audio taper.
>>
>> One local store says they'll order them from Mexico, but they cost
>> hundreds of dollars per pound. I forget the figure he quoted but he was
>> talking "ounces" and when I went home and weighed them I figured I'd
>> need a few pounds a year. I don't care if they're "realy, REALY good
>> stuff" that's just too much to pay for potentiometers.
>>
>> So can I use the cheapies in Mouser's catalogue? What is the lowest
>> wattage you'd recommend? I won't be using these for bias adjustments,
>> but if a cap *does* fail should the pots be RV4 rated?
>>
>> Karl
>
> The advantage of the 2 watt pots is the larger capacity in power they
>will handle. I know they are not commonly used in circuits where there
>is power involved, e.g. volume, tone, etc. For bias and hum balance,
>the additional power capacity is needed. The best thing about the 2
>watt pots is that they are sealed, no dirty contacts. They are also
>much better constructed than cheap ones. I will use them in circuits I
>build to ensure better quality. The rotation feel of them is also
>noticed even when one cannot see the pot. I know Allied caries the
>pots. The military versions are the best to get. Ohmite A/B, and
>Clarostat make these pots and one is as good as the other. The cheap
>pots are used in mass production only because of cost reduction. The
>cheap pots are 1/2 watt for linear and 1/4 watt for audio taper.

I think that the best value in this style pot, currently, is in the
line made by Precision Electronic Components, Ltd. of Canada. I have
found them to be far superior to those being manufactured by Clarostat
in Mexico. I believe that NTE is distributing many of them in the
US. I don't know if they make them in other than linear pots.

Alps Blue Velvet pots are very nice, too, but physically quite
different (square body, PC type terminals).


Brian McAllister

Sarasota, Florida

email bkm at oldtech dot net