Welcome! Need support, you got it. Or share you ideas and experiences.
70.158.128.52
In Reply to: RE: Transformers posted by Paul Joppa on September 25, 2009 at 13:45:03
Hammond has a couple of high inductance, low current chokes which may be usable as suitable plate loads for the Quickie's 3S4s.
155C, 60H, 8 mA, DCR = 2750 ohms, about $14 each.
156C, 150H, 8 mA, DCR = 3700 ohms, about $15 each.
Since these are both below the nominal 4.02K plate resistor value, one could insert an LED in series between the B+ line and the choke's "hot" side, for a pilot light, or tube activity indicator. Depending on the LED color, it will introduce between 1.6 and 3.6VDC voltage drop, which is pretty much minimal. Don't connect the LED on the plate side, it could introduce some unwanted noise into the equation.
Now, these inductors aren't going to be of Magnequest quality, but at the cheap prices, they may be a good deal for this application, along with the SPECO matching trannies. I'd SWAG that 2.2 to 3.3 uF would be a good coupling cap value , into the reflected 4K ohms. Voltage rating could be as low as 100V, but I'd probably go with 250V (basically because I have lots of such caps in my stockpile).
This topic alone has intrigues me to the point that I put in an order for not just one, but two, Quickies ;-)
Being one who can never leave "well enough" alone, these Quickies are a very interesting and readily modifiable project, which I just can't resist.. A little research indicates that 1S4s can be used with a simple re-conenction of the filament leads (use pins 1 and 7, leave 5 open). Just becuzz....
All of this talk of "quickies" reminds me of a very old, rude joke involving a pastor and a nun, but since this is a polite family-oriented site, I won't post it here ;-)
/ed B in NC
real radios glow in the dark
Follow Ups:
I was also looking at the 156C (hey, 90 more henries for a dollar). My initial thought, without doing any calculation, was that a CCS (C4S) would necessitate adding a bunch of voltage, as well as adding 1-2 ma overhead, which would drain the batteries.
I too ordered 2 of them. I justified one for my low pass filter and the other for a portable headphone amp to work with my Blackberry. But like you (if I get your drift correctly), I find this to be a very exciting experimenter's platform. It also provides all kinds of incentive to try cheap tricks. I've always gone for high end components on my other builds, and this one is very well suited to trying bang for the buck upgrades, at least for me at this time.
Thanks again for the help before.
Triamp... Take a load off!
"Why use the 3S4" you ask? The new AES catalog shows 1S4 for $2.90, 3S4 for $2.80. 'nuff said? :^)
I've got both 3A4s and 1S4s in my toob-stash, as well as 3Q4s, these olde style battery tubes often showed up for dirt cheap at the local NE flea markets and swapmeets.
As you state, this IS an experimenter's delight!
/ed B in NC
real radios glow in the dark
I have a stash of 1T4's. Though the pinout and construction seem the same as 3s4, Duncan Amps lists them as pentodes with an Ra of 500K. They seem to consume half the heater current of the 3s4's. I'll probably try them when (if) I find the time.
Triamp... Take a load off!
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: