An alternate 36v supply... (9v are sooo expensive!)

[corndog71]

My amp is a modified version of the Dynaco ST35.  You can read more about it here:http://www.bottlehead.com/smf/index.php/topic,1990.msg15355.html#msg15355


Mark, stay tuned.  I have an idea for tidying up those batteries.

[Grainger49]

Eric,

One of you guys has to post a thread with all the quintessential Quickie tweaks.

Start a new thread and just list them then sort out the order of magnitude of the impact it has.

[earwaxxer]

not a bad idea!

[Alonzo]

I'm running a 36v supply with 3 SLA's and it runs great, tomorrow I'm going to try Graingers suggestion of adding some film caps to each tube so I'd thought I'd also try to get the D-cells out of the Quickie too.  Here's my idea, Fry's has some 6v/1.4AH batteries for around $10.  Any opinions of hooking this battery up like this; would this work?
  SLA ===>1 Ohm 1/2watt====>=>====1 Ohm 1/2watt===> Gnd
                                                   ll
                                                   ll
                                                  / \
                                                 /   \
                                      red LED    red LED
                                           /             \
                                       3s4             3s4
I'm thinking the voltage divider gives me 3 volts to the LED's, which should drop about 1.7 volts, leaving 1.3 to the tube heaters.
Now this is thinking after a good snifter of JohnnyW and a long day at work. It gets rid of the rechargeable Dcells, I also get a nice indicator led and there 's room in my battery bank for the small SLA. 
This seems too easy, what am I missing?

[Paul Joppa]

You show a voltage divider of 2 ohms across a 6v battery, so it's drawing 3 amps. Each 1/2 watt resistor is dissipating 9 watts and the 1.4Ah battery would last not quite a half hour if the resistors didn't explode. Trust me, they will!

The main issue though, is that each tube needs a floating independent heater power source. If you want to use a higher voltage than 1.5 (or 1.2 for NiCd or NiMH) then it's best to get two batteries, and place a chip regulator between each of them and its tube. You can even get 2-volt SLAs in a D cell package, which would work with a low-dropout regulator at 1.2 or 1.5 volts.

But a good NiMH D cell has 10Ah capacity; why replace it with 1.4Ah? (Note many "D cells" are actually AA cells in a big can - don't get those ones!)

[Grainger49]

I haven't looked at the specs.  Wouldn't the NiCad/NiMH 1.2V be within spec for the tube?  Seems ideal, except, possibly for the AH rating.

Is there a way for Quickie owners to know the difference between the true rechargeable D cells and those made from AA cells?

[earwaxxer]

I've been using AA rechargeables from the get go. It doesnt seem to be a problem.

[Paul Joppa]

For the longest life between recharging, you want "true" D-cell size rechargeable cells. The same applies to primary (non-rechargeable) cells of course. The full-capacity D cells cost more and are harder to find. But any NiCd/NiMH, alkaline, or even carbon-zinc cell will work while its charge holds. You just re-charge (or replace) the lower capacity ones more often.

As I said recently, it's hard to find good specifications on the required voltage, but here's a summary:

1.0 volts seems to be the minimum

1.2 volts is the nominal for NiCd and NiMH, both of which hold that voltage closely throughout their discharge

1.25 volts is the average spec; some hearing-aid tubes (which ran off of carbon-zinc or alkaline cells) are specified at this voltage

1.4 volts is the specification point for the 3S4 and most all of its relatives designed for portable radios

1.5 volts is the nominal voltage of a fresh alkaline or carbon-zinc cell (it drops linearly as it drains, I call them dead for audio when they hit1.0 volts, but they are rated to 0.8 volts for use in flashlights)

1.6 volts is the absolute maximum for the 3S4 and its relatives

I feel that 1.2 volts is ideal for Quickie, giving full performance and the longest possible filament lifetime. Because Quickie doe not demand anything like the maximum plate current, it can operate at the lower end of the recommended voltage range without depleting the space charge, and the low plate voltage reduces the risk of cathode poisoning in any case.

[galyons]

Thanks Paul,
This is most helpful!!!!

Cheers,

Geary

[Alonzo]

Thanks for the lesson Paul!! 

[Grainger49]

My interest here is more than academic, I think that battery supply pre-amps are the bees knees.

I have gathered a short list of pieces to sell.  This should help with the Orcas and maybe a Quickie.  

There are two systems that I care about, then the AV system which makes sound.  I have a system in the work room and the "big rig" in the listening room.  My last 4 houses have had to have a listening room.  It took a number of houses with our realtor to get the definition of "Listening Room" across to her.  But being the only Professional Realtor I have ever known, she go it.  Anyone in the Atlanta metro area should contact me.  Linda is on top of her game.

[4krow]

Man, Does THAT ever ring bells! Listening room, shop, dark room, even garage are not readily understood as to their purposes. When I say shop, I want 220, I want lots of 110v outlets, I want ROOM, and so on. Some people get that. But say I want a listening room, and they give you a cube, or a hallway, or a cube with 4 doors. The only reason that I hate my dance studio is that I easily bruise my shins on the coat rack. Ok, ok so I'm not a dancer, and no, not even a closet dancer, but you get my point boys, 5 6 7 8....dip me,, in sulpher. Man this is great coffee.