"John Byrns" <byrnsj@[EMAIL PROTECTED]
> wrote in message
news:byrnsj-D6B303.08411522042008@[EMAIL PROTECTED]
> In article <824Pj.340419$G71.82199@[EMAIL PROTECTED]
>,
> "Iain Churches" <IainNG@[EMAIL PROTECTED]
> wrote:
>
>> Can I suggest a topic for you? A current limiter for tube heaters.
>> People are keen to use voltage regulation, which doesn't seem to
>> me to be so im****tant. Heaters are specified at +/- 5% so
>> anything between 6V and 6V6 for a 6V3 heater is within tolerance,
>> and with a wirewound pot between two 'lytics one can get it spot on.
>> But heaters draw huge currents at switch on. Do you have a circuit,
>> using those funny black things with ****ny legs, that could current
>> limit? Two circuits would be of interest. One at say 1.2A
>> (a pair of B9A's) and one at 3A (a pair of EL34's)
>
> Your comment "one at 3A (a pair of EL34's)" suggests that you are
> contemplating running the EL34 heaters in parallel, this seems like a
> singularly bad idea to me. Unless the heaters in both tubes are
> identical the current will divide unequally between the two heaters.
> There is also no guarantee that you will get 6.3 volts across the
> heaters, so the heaters will likely not be operating at either rated
> voltage or current.
Please explain, John. Everywhere I measure the heater
voltage in my amp I get 6V3 spot on, with no variation
anywhere. I have always connected heaters in parallel
without any kind of current regulation. All European
makers seem to have done this. So far I have found
no ill effects.
> If I were using current regulation I would connect
> the two heaters in series so that I would be guaranteed that the heaters
> would operate at their rated current.
Thanks John. That's the kind of info I was looking for.
Iain
|
