Quote from: Paul MarossyOK, I have one more question:
The 1uF caps on V1a and V1b, can I use a 50V cap there?
And the 10uF cap on V2a, a 50V cap there as well?

For v1b and v2a 50V is fine. I would go at least 100v for the v1a cap.

Doug

Quote from: smoguzbenjaminSo how would you go about selecting where the tubes/transformers go? :? I mean after you drill holes etc it's kindof a pain in the ass to move stuff around.

Layout is a big subject in and of itself. This is why you should hang out at places like ax84 and ask the experienced people there. I'm not trying to blow you off, it's just my layout for this evolved on the fly and it is messy, but it happened to work. So I didn't provide a layout for this project but I will for the next one. The main thing is to use star grounding, avoid running wires in parallel (cross them at 90deg angles if they have to cross), keep wire runs as short as possible, and things like that. A good thing to do is to visit some amp sites and study the layouts there. You will start to see familiar patterns in them. A few recommendations for studying layouts would be ax84.com, house of jim, and the fender amp field guide to name a few. RG covers star grounding at his site, he has an excellent article on it.

Doug

Quote from: Alex C
I didn't mean to imply that the circuit is the problem!     I that's what it sounded like though.  I asked a few days ago about the squealing problems and everyone told me how much it would depend on the physical layout of the components.  I just haven't had time to get in there again.  I was trying to say that besides my own problems, the amp is sweet!  Sorry for the misunderstanding.  

Alex

No misunderstanding here.  I didn't read any implication at all into what you said. I was just trying to help, because squealing and oscillation can be a major PITA to solve!

One thing you can try is the "chop stick" test. Use an INSULATED stick, like a wooden dowel or chop stick (I use one of my wife's artist paint brushes). Fire up the amp and with one hand behind your back use the INSULATED stick to gently move wires around inside the chassis. When the squealing changes in pitch, you have probably found the sensitive spot in the circuit where the feedback is occuring. Use this to give you clues about what you might change to eliminate it. Sometimes all you need to do is move the position of a wire slightly.

Please be CAREFUL when doing a live voltage test like this! It can be deadly!!

Doug

Well, I got the chassis about 50% wired. Just waiting for my transformers, 400V filter caps, tube sockets and a few other parts to complete the chassis. I think tonight I'll start on the enclosure. Oh boy this is fun!  

http://www.diyguitarist.com/Images/FF-ChassisWiring1.jpg">

Wow, Paul..
looks good so far.. did you go by the Rev3 schematic? (with the boost)

And did you do your own layout?

You're giving me the itch!!
"-)

Rev. 3 with a little mod, a resonance control. I'm adapting a turretboard layout that was sent to me to point-to-point wiring. It's sort of my own layout because it's adapted to my chassis, but the physical layout is more or less the same as the layout sent to me.

Excellent work, Paul!  That looks fantastic!

And I got the enclosure done last night. This is a cut down Crate bass amp enclosure which has been re-covered with some cloth I had laying around from an unrelated project. All I need now is my parts to finish the chassis...

http://www.diyguitarist.com/Images/FF-EnclosureNew.jpg">

Wow, looks really great!

I wish my stuff looked like that!

Doug

Yeah, that's very nice.  I especially like the "PJM" logo.  Very professional-looking.

Alex

Thanks.

The "PJ" part of the logo is actually forms the glass envelope of a power tube. On top of the "PJ" is the pins and base. It's hard to see in that picture, though. I made this logo about a year ago when I was toying around with trying to do some of this stuff on a professional level and needed a logo. I have a business card designed using this logo, but I never actually had the cards made up - yet.

In a pinch you can use the much touted Radio Rat line transformeras an OT.I used it for my FireFly and costs $2.
Also another idea for the PT,if you find a small transformer that puts out only 120V or so you can always do a voltage doubler power supply.
Aharon

QuoteIn a pinch you can use the much touted Radio Rat line transformeras an OT.I used it for my FireFly and costs $2.

What??  :shock:
How does it sounded? Does it had the same power output?

Do you know the part number?  

THANKS
Kleber AG

Hey, whatabout grounds? On all tube amp schematics I find, there's a ground connection to the 'earth' part of the mains. Whatabout if that earth isn't there? Will the circuit still work? Or can't the current flow?

Quote from: Paul Marossy

The "PJ" part of the logo is actually forms the glass envelope of a power tube. On top of the "PJ" is the pins and base. It's hard to see in that picture, though.

I see it now, WOW!  That's even more impressive!  Very, very nice.  I love it!


Alex

smoguz-

It'll still work, but you can potentially get electrocuted (and get killed) with the main power supply not being grounded. It's happened before. It's a safety thing.

for that enclosure - do you have to mount it upside down?
"-)

Upside down? When the chassis is inside the enclosure, it's just like any other amplifier. Transformers and tubes on the underside of the chassis. Since these are just preamp tubes, I don't think that is a problem, as far as heat goes.

What??  :shock:
How does it sounded? Does it had the same power output?

Do you know the part number?  

THANKS
Kleber AG[/quote]

I lost the part #,some Radio Shack stores may still have it or maybe on-line.
The USA version is 10W and the canadian version (the one i got) is 5W.
Sounds cool,maybe not as much bass,maybe......I have to tweak the power supply to give me more juice and I'll report back.Sounds really nice especially on cascode mode.Like I've said,I still have to tweak it.
The good thing is that if you use a 16 ohm load an connect it to the 8 ohm tap of the RS tranny you get the 22K impedance that Doug specified on the schem.
Regards
Aharon

Check the RS tranny in the back:


http://f1.pg.photos.yahoo.com/ph/liv_energy/detail?.dir=/My+Photos&.dnm=FireFly.jpg

Quote from: Paul Marossysmoguz-

It'll still work, but you can potentially get electrocuted (and get killed) with the main power supply not being grounded. It's happened before. It's a safety thing.

:shock: Holy crap! :shock: is there any way I could wire this so it won't electrocute me?