1st build hemming and hawing

General discussion area for tube amps.

Moderators: pompeiisneaks, Colossal

Cliff Schecht
Posts: 2629
Joined: Wed Dec 30, 2009 7:32 am
Location: Austin
Contact:

Re: 1st build hemming and hawing

Post by Cliff Schecht »

TBH I would recommend against putting a tap switch on there. IME these switches WILL fail over time. Most all switches are really meant to handle AC voltages at high currents, not large DC voltages at low current. I've had this fail enough times to never do it again.

Instead you can mismatch the output transformer secondary loading either by running a 4 Ohm speaker into an 8 Ohm cab or an 8 into a 16. What this does is effectively reflects back twice the impedance that is expected and causes the OT primary winding to look twice as large as it is. So 5k becomes 10k. Or you can go the other way (8 Ohms into 4 Ohm speaker, etc.) to cause that 5k to look like 2.5k. Within limits this is usually alright to do, as long as the OT can handle the increased power that it will be seeing and the bias is set appropriately. Cathode biased amps tend to be self-limiting and thus are pretty hard to blow up unless you are really pushing the dissipation (either via hot bias, high plate voltage or extreme mismatching).
Cliff Schecht - Circuit P.I.
Smokebreak
Posts: 1391
Joined: Tue Dec 18, 2012 5:53 pm
Location: Texas

Re: 1st build hemming and hawing

Post by Smokebreak »

Phil_S wrote: That's not right. Everyone needs another guitar and another guitar amp. Stop kidding yourself. This isn't about what you can use. After you build one, you'll understand this truth better. It's the Dynaco's that are nice to have. Either way, learn how to do it and you can build what you like.
This cracked me up Phil! Though perhaps never truer words have ever been written.

Scooter: go crazy with the switches(bearing in mind what Cliff said)NFB, tone stack lift(though maybe you could go for the 5F2a: champ with a tone control), cathode bypass. Something I like to do on these kinds of amps is put in an Orange style FAC rotary switch, which simply changes out coupling caps for different flavors . If you ever want to hang out, build an amp together, or see living proof of what Phil speaks of, even after only a year of amp building in my case, I'm in 78704.
Cliff: if you ever need some company I'd love to see what you are working on! I've got family in Georgetown and get up that way often, and would make the trip regardless.
I'll be up at The White Horse tonight at midnight playing my Express if either of you want to grab a beer. Please forgive my over-zealousness, I'm just a bit tickled at the prospect of amp building friends in town.
Anyone in Austin have a pair of 22M resistors?
Cliff Schecht
Posts: 2629
Joined: Wed Dec 30, 2009 7:32 am
Location: Austin
Contact:

Re: 1st build hemming and hawing

Post by Cliff Schecht »

What few 22M resistors I have are 3W carbon comps that I'm holding onto. I use them occasionally and like you're experiencing resistors are hard to find over about 5 meg.

I'd definitely be down to hang out and talk shop sometime. I don't really have a lot going on right now (can't find a job :-/) so I'm just sort of bumming around trying to figure out ways to make money. I moved a bit over a month ago and lost all of my customers in Lubbock. I actually have some stuff to do tonight but I'm usually pretty free.
Cliff Schecht - Circuit P.I.
User avatar
Scooter Thomas
Posts: 32
Joined: Sat Aug 10, 2013 9:40 pm
Location: Austin, TX

Re: 1st build hemming and hawing

Post by Scooter Thomas »

78704, it's not a zip code, it's a way of life! :lol:

That's kinda late, even for me! I'd make it except I'm prepping for a 9am colonoscopy tomorrow, seriously. TMI, I know.

I don't think I'm ready for a chassis crowded with options. I'd consider Nik's kit if I wanted to go that route but I appreciate what you're saying.

Re tone stacks, there's nothing to lift on a 5F1, right?
Cliff Schecht
Posts: 2629
Joined: Wed Dec 30, 2009 7:32 am
Location: Austin
Contact:

Re: 1st build hemming and hawing

Post by Cliff Schecht »

Not unless you have a tone control, no there's nothing to lift. All you need to do to bump up the gain is add capacitors to the V1A and V1B cathodes.
Cliff Schecht - Circuit P.I.
User avatar
Scooter Thomas
Posts: 32
Joined: Sat Aug 10, 2013 9:40 pm
Location: Austin, TX

Re: 1st build hemming and hawing

Post by Scooter Thomas »

Well, I pulled the trigger on the Triode 5F1 kit and chassis today so maybe I'll be wiring this guy up next weekend or so. As discussed, I went with the 15w OT and included the 10w cathode resistor.

The kit comes with push-back wire. I've never used push-back, and I've read discussions here, so I'm a little concerned. On the order form I asked 'em to sub teflon or something else but I don't know if they can. And the "double D" strain relief? Never done that either. Hope I don't need a special tool!

Anyway, I'm not gonna blog this (admittedly banal to you guys) build but I'll be shooting some iPhone pics as I go. I plan to take my time, no hurry at all. Should be fun!
User avatar
JazzGuitarGimp
Posts: 2357
Joined: Mon Jul 23, 2012 4:54 pm
Location: Northern CA

Re: 1st build hemming and hawing

Post by JazzGuitarGimp »

Scooter Thomas wrote:Well, I pulled the trigger on the Triode 5F1 kit and chassis today so maybe I'll be wiring this guy up next weekend or so. As discussed, I went with the 15w OT and included the 10w cathode resistor.

The kit comes with push-back wire. I've never used push-back, and I've read discussions here, so I'm a little concerned. On the order form I asked 'em to sub teflon or something else but I don't know if they can. And the "double D" strain relief? Never done that either. Hope I don't need a special tool!

Anyway, I'm not gonna blog this (admittedly banal to you guys) build but I'll be shooting some iPhone pics as I go. I plan to take my time, no hurry at all. Should be fun!
The special tool for the strain relief does make the installation go a bit easier, but it can be done with a pair of slip-joint pliers.
Lou Rossi Designs
Printed Circuit Design & Layout,
and Schematic Capture
User avatar
Blackburn
Posts: 1765
Joined: Tue Feb 05, 2013 8:39 pm
Location: Texas

Re: 1st build hemming and hawing

Post by Blackburn »

I'd highly recommend investing in these, or else...

http://www.newegg.com/Product/Product.a ... 02V0S76428

Don't think I've tried slip joint pliers. They work okay for you, Jazz? I had a hell of a time with everything else, until I got the device.
tubeswell
Posts: 2337
Joined: Thu Mar 27, 2008 6:42 am
Location: Wellington. NZ

Re: 1st build hemming and hawing

Post by tubeswell »

Scooter Thomas wrote:Well, I pulled the trigger on the Triode 5F1 kit and chassis today so maybe I'll be wiring this guy up next weekend or so.
Happy amp building days ahead! 5F1 is perfect place for starting to learn about it. You'll soon be building a pile of amps in next to no time.
He who dies with the most tubes... wins
User avatar
JazzGuitarGimp
Posts: 2357
Joined: Mon Jul 23, 2012 4:54 pm
Location: Northern CA

Re: 1st build hemming and hawing

Post by JazzGuitarGimp »

Blackburn wrote:I'd highly recommend investing in these, or else...

http://www.newegg.com/Product/Product.a ... 02V0S76428

Don't think I've tried slip joint pliers. They work okay for you, Jazz? I had a hell of a time with everything else, until I got the device.
Yes, slip them into the large jaw and they work pretty well. I have the proper tool (Heyco) these days, but I used pliers for years before I got the real deal.
Lou Rossi Designs
Printed Circuit Design & Layout,
and Schematic Capture
User avatar
Scooter Thomas
Posts: 32
Joined: Sat Aug 10, 2013 9:40 pm
Location: Austin, TX

Re: 1st build hemming and hawing

Post by Scooter Thomas »

During hardware assembly I ran into this bugaboo. The nut for the nylon fuse holder just threads a rev or two and stops. Is there a trick? I thought about getting a better part but Hoffman's looks the same and i didn't look further.

What's with the notch on the nut? It kinda looks like a keyway?
You do not have the required permissions to view the files attached to this post.
User avatar
M Fowler
Posts: 14036
Joined: Wed Jan 16, 2008 2:19 am
Location: Walcott ND

Re: 1st build hemming and hawing

Post by M Fowler »

The notch allows the nut so slide over the solder tabt easier especially if it has been bent out ready for soldering.

I've installed over 70 of these fuse holders and never had problems with tightening them. The chassis and backplate (if used) shouldn't be too thick I wouldn't think as there seems to be plenty of thread on these units. :)

Mark
Smokebreak
Posts: 1391
Joined: Tue Dec 18, 2012 5:53 pm
Location: Texas

Re: 1st build hemming and hawing

Post by Smokebreak »

Shouldn't be a trick. Maybe try it with pliers . The notch in the nut is so it can slip over the lug on the body of the fuse, as it can protrude from the body once it's bent up for soldering.
Firestorm
Posts: 3033
Joined: Fri Jan 25, 2008 7:34 pm
Location: Connecticut

Re: 1st build hemming and hawing

Post by Firestorm »

Might be cross-threaded a little. See if you can get it squared up outside the amp. Nylon only gives you a couple of chances.
User avatar
Scooter Thomas
Posts: 32
Joined: Sat Aug 10, 2013 9:40 pm
Location: Austin, TX

Re: 1st build hemming and hawing

Post by Scooter Thomas »

I put pliers on the nut and, holding the barrel in my hand I was able to force it up to maybe 4 threads but that's still not even close. And I swear it's not cross-threaded. I think I'll try a vise, cause it seems like it wants to thread but it's just super tight.

So Mark, you can thread these by hand? Maybe I got a funky piece.

Thanks guys!
Post Reply