new build -- advice, please

[jimipage]

I feel ready to build my first Wreck. I don't have the necessary components to build a fixed-bias circuit, so what's the best route to take with cathode-biased: Express, Rocket, or __? Tube or SS rectifier? I will be using 6v6's. I also have the option of building single-ended, as well.

let the beatings begin

[Normster]

It's just a couple of diodes, caps, and resistors.

[jimipage]

um, don't I need a transformer with a bias tap?

[stoo]

Have a look at any of the TW schematics! They just take one side of the secondary and do a half wave rectification filter and voltage divider and Walla! bias!
Stew

[jimipage]

when I said, "let the beatings begin", it was in jest. Seems like I'm getting some hostility here, and neither one of you answered my original questions. Though I've built several amps, I'm still learning about all this, so back off!

[jimipage]

I don't have the necessary components to build a fixed-bias circuit...

when I said that, I meant it. I don't have the correct potentiometer for a bias adjust, and I don't have the 1ohm resistors to test my work. I'm attempting to build an amp with the materials I already have. I asked for some advice about making a Wreck that's cathode-biased. I apologize for getting defensive in my last post. I come here for help because most here seem to know way more than I do.
again, sorry.

[stoo]

when I said, "let the beatings begin", it was in jest. Seems like I'm getting some hostility here, and neither one of you answered my original questions. Though I've built several amps, I'm still learning about all this, so back off!

Sorry dude! Didn't mean to PO ya! Don't know 'bout the cathode biasing. I like the adjustable fixed bias cause I'm always playing with different op tubes.
Stew

[jimipage]

everything's cool here; I hope everyone's cool with me.

[Normster]

Why don't we just start over again. Just pretend that I'm not a smartass and that I genuinely didn't know what you meant by "not having the necessary components."

You don't need a bias tap on the PT. You can take the bias voltage from one of the secondaries. As Stoo said, look at the Express schematics and layouts in the "Files" section. That's the way Ken did it. If you're trying to build the amp with stuff you've got on hand, you may still be able to pull it off. (I've used everything from 10K to 50K for bias pots.)

Cathode bias might be an option, but I've only tried it on 18watt-style amps. However, the TW breaks up pretty quickly already so no idea what the headroom will be like.

I believe the Rocket was the only amp that KF ever built with a tube rectifier, but I could be wrong. IIRC, it was 4 x EL84s and ran pretty low plate voltage.

[rfgordon]

I did my Express as cathode bias EL34s (with each cathode going to a 300 ohm/100 mF combo), and it was still ginormously loud, so don't worry about losing volume! That said, if you cathode bias big bottles like 6L6 or EL34, they do tend to yield more grind than crunch than do fixed bias tubes. The preamp is still pretty much the same.

[jimipage]

thanks for the replies, guys. I'll probably just go ahead with what I know regarding cathode bias. I'll give the fixed-bias a go the next time I order some parts. Still don't know if I'll try a tube rectifier or not.


Normster, no hard feelings. I'm sorry for being prickly. I usually try to keep my not-so-good moods away from these boards. BTW, I'm probably the biggest smart@ss I know

[KGW]

Any pot could be used for a bias pot. Once you get the pot adjusted for the proper bias voltage (-33 VDC), you could replace it with a fixed resistor (just disconnect and measure the pot).

As for the 1 ohm resistors, they are nice, but you don't need them (the Komet amps have these but the TWs did not - as far as I know).

In Kevin O'Connor's first TUT book, he talks a lot about cathode vs. fixed bias. You may want to get that book if you really want to learn about amp building. However, like most amp builders, he is opinionated, so don't take everything as "the best way to do it." I just have the first book now, but I plan to get the others. Great stuff (I think others will agree).

As for having parts, where I live, I have to order everything. I'm getting quite a nice assortment of extra parts though. Sometimes, one has to compromise having the "right" parts in order to fine tune an amp by using what you have on hand. Once you have the amp working how you want, you can buy the better parts later.

I hope that helps.

[jimipage]

In Kevin O'Connor's first TUT book, he talks a lot about cathode vs. fixed bias. You may want to get that book if you really want to learn about amp building. However, like most amp builders, he is opinionated, so don't take everything as "the best way to do it." I just have the first book now, but I plan to get the others. Great stuff (I think others will agree).

As for having parts, where I live, I have to order everything. I'm getting quite a nice assortment of extra parts though. Sometimes, one has to compromise having the "right" parts in order to fine tune an amp by using what you have on hand. Once you have the amp working how you want, you can buy the better parts later.

I hope that helps.

Thanks, KGW. I do have TUT#1 (I'll be getting #'s 2 and 3 soon), and as much time as I spend reading it, I should obviously study it more. I find I need to take him a few paragraphs at a time, though. I think what his book lacks is that certain get-to-the-meat-and-potatoes approach that I really enjoy in Dan Torres' book, the "here's the components, take this out, put this in, measure it -- is it ok? go!" style.
I do have quite a collection of books, some that get studied more than others. So far I've built nine amps in the last year. I've got a fairly well-stocked shop, just not everything. I don't consider myself a newbie, just a beginner whose obsession is turning into a new life's path.

I see you live a few hours north of me. I know what you mean about having to order everything; the nearest hardware store to me is 60 miles away!
Checked out your site: very cool. You build some very sweet looking amps. One day we'll have to meet up, neighbor.

[KGW]

Sounds good sir.

Thanks for the complement on my DIY.

I'll have all my parts to finish my Express build next week except for the wire (solid silver plated copper with teflon jacket) as it seems to be lost in the mail. I have lots of wire but not the nice stuff like this.

cheers - Kevin