FireFly tube amp

[ErikMiller]

I feel weird putting "OT" in front of a topic that is so often discussed around here.

Can't we just say that the FireFly is an "effect." :-)

Anyway, I'm having trouble with a couple of components, resistors actually.

R13 is called out as a "440" ohm resistor. I have a pile of 470's, and even a few 430's, but the 440 is a rare beast indeed. Is this value that critical? Or do I need to take one of my 430's and put it in series with a 10?

Also, the cathode resistor, 1.8K seems something of a rarity in the world of 1/2W resistors. Is it really taking that much power? I suspect it might, being on the cathode and all....

I'm really excited to get this thing going. Building a tube amp is a whole other level of DIY-itude, one that I've been wanting to check out for over 10 years.

[Lurco]

440 = 2 times 220, if this helps.
Absolutely don`t know which circuit you refer to,
but maybe it`s a questionf of parting voltage or
power over the shoulders of 2 resistors?

[smoguzbenjamin]

You don't know the firefly! :| You need to check out Doug's site! Uhm... I don't know the URL but try ggoling for "Doug hammond firefly" that should get you some results.

[Doug H]

R13 is called out as a "440" ohm resistor. I have a pile of 470's, and even a few 430's, but the 440 is a rare beast indeed. Is this value that critical? Or do I need to take one of my 430's and put it in series with a 10?

Also, the cathode resistor, 1.8K seems something of a rarity in the world of 1/2W resistors. Is it really taking that much power? I suspect it might, being on the cathode and all....

.

I used 2 220's in series for the 440. 470 should work fine, I just didn't have any on hand and drew the schematic the way I built it.

You should be able to get 1/2W 1.8k resistors at mouser. As a rule, I use at least 1/2W resistors in tube circuits.

Doug

[Paul Marossy]

I used a 470 ohm instead of the 440 ohm, and it sounds fine to me.

For the 1.8K, I used a 1.5K and a 330 ohm in series, which gets you pretty close to 1.8K

Most of my resistors are a couple in series to more or less match the schematic, I just didn't have most of those exact values lting around...