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On the FireFly, is there any specific make and model on the main power transformer and heater supply transformer? I thought I remembered someone talking about this, but I can't seem to find it...

I've got my chassis all ready for point-to-point and I am going to build the enclosure while I'm waiting for parts. This is going to be fun! I'm ready to roll!  8)

Hey Paul,

Please post your results as I'm thinking of making a firefly :D

cheers
Ben

OK, I will. I've messed with tube amps some, but this will be my first build. It's not too complicated of build, so I think it's a good starter project.

I'm doing a preliminary chassis layout right now. I have a 14"x6.5"x2" chassis I pulled from a piece of _____ Crate amp. I'm going to recycle it. I need to figure out the physical placement of the transformers most of all. The ones that Doug used look fairly small in size and I would like to use something similar.

Quote from: Paul MarossyOn the FireFly, is there any specific make and model on the main power transformer and heater supply transformer? I thought I remembered someone talking about this, but I can't seem to find it...

I asked about the transformer(s) and was told that I needed one that would do 200V. Since then I've been hunting and haven't been able to find something that I am sure will work.

I just don't know enough about spec'ing transformers, so I probably need part numbers.

If someone who's built one could go to Antique Electronics' web page and pick 'em out, that's the amount of hand-holding I need.

Hey, I built the Firefly with the Hammond 269EX, which can run at 190V, based on Doug's recommendation.  It includes a 6.3V tap for the heaters, and it works just fine.  I'm having some trouble with oscillation at some settings, but those on which it works sound incredible!  Listen to Doug's new sound clips and let your jaw drop.  This thing sounds awesome.  Build this amp immediately!  

Alex

The Hammond 269ex is available at Mouser //www.mouser.com
and Antique Electronic Supply  //www.tubesandmore.com  .

I believe it's a few bucks cheaper at Antique Electronic Supply.  Hope that helps.

Alex

Thanks for the tip Alex.

Looking at the specs found at http://www.tubesandmore.com on the Hammond 125A output transformer, it doesn't quite do the full range of audio - 150Hz to 15kHz. That's OK on the high end since the highest harmonics a guitar can produce is around 3kHz, but the low end of guitar is 82Hz. So, that would mean a reduced bass response, right? But, the transformer they suggest, the P-T1627SE does. But at $98, I think I can live with the 125A.  8)

Also, on that Hammond 269ex, the secondary is center-tapped. I assume that the center tap is not used?

Yes, the center tap is not used.   I'd say I could live with the 125 A also.   :)

Thanks, Alex!

That's just what I needed to know.

I wonder what the differences are between the 125E and 125A.

It's going to be hard getting used to paying upwards of $30 for a single component.

Wow -
I've been thinking about an amp in the back of my mind for a while.. and was thinking that the Firefly would be a good place to start..

but I never thought it would sound like THAT... the sound clip on the rev 3 (doing the EVH licks) sounds AMAZING.. it's the 'brown sound'.. it's amazing..

good work as usual, Doug... and I think a Firefly build is in my NEAR future.
"-)

As you go down the alphabet, the wattage ratings increase.

a = 3 Watts
b = 5 Watts
c = 7 Watts
d = 10 Watts
e = 15 Watts

The basic difference is more iron and thicker wire.

The best prices I've seen on Hammond trannys is from http://www.angela.com  (It was hard to get used to people here calling transistors as trannys after coming from tube land). Great cap selection there too. :D Check out the FastCaps!!!

For power, there's a lot of flexability. You could use a 115/230 step up/down transformer too. The higher the voltage, the cleaner the sound. The only thing you might have to adjust is the cathode resistor on the 12AU7.

Best of luck on your FireFly! I will be surprised if you don't end up loving it! :D

Take care,
-Peter

So if I used a 125d instead of a 125a, would I get more power just like that, or would some circuitry have to be adjusted?

You need larger tubes to get more power. The wattage is rated like a resistor.... use too much and you let the blue smoke out. :)

If you use a larger transformer, you can use different tubes. If you use the 125A, you are fairly stuck with lower power.

The 125C would be a good choice for a self-split EL84 amp. If you want to experiment, I would get a larger transformer like the 125D or E, as that will keep all of your options open.

Take care,
-Peter

So low wattage tubes + 125E will make no difference except that I could throw more power at it in the future if i wanted to. Okay makes sense... :? Got to get my head around all this new info though.

Here are some transformers that will work:

Power:
---
Mouser Stock No: 546-186B120
Mfr. Part #: 186B120
Mfr. / Suppler: Hammond


Description: Hammond Power Transformers
115/230, 6VA,120VCT (50ma)

$ 10.53

You will need 18ma for the output stage and few more ma for the
preamp. Something that puts out 50ma gives a good safety margin.

----

Filament:
---

Mouser Stock No: 41FD010
Mfr. Part #: 41FD010
Mfr. / Suppler: Hi-Q


Description: HIQ Heavy Duty Power Transformers
TRANS FIL 6.3V 1A
Product Category: Power Transformers

$ 4.79

You will need about 900ma for the tube filaments (300ma x 3 tubes),
so 1A should cover it.
---

So for approx $15 you can get a separate filament and power
transformer for it. Not bad, since I paid $14 for my surplus
transformers and thought that was a good deal.

---

If you want a combination filament and power transformer try this:

http://www.tubesandmore.com/new/scripts/silverware.exe/moreinfo@d:/df
s/elevclients/cemirror/ELEVATOR.FXP?item=P-T269EX

B+ will be a little lower but it should be okay.

---

For an output transformer I used a hammond 125a. I like it because
the 22.5k primary Z sounds real good (and I think its easier on the
tube).


So you have some options for transformers. I need to put this info up on my site.

Doug

Quote from: Alex CHey, I built the Firefly with the Hammond 269EX, which can run at 190V, based on Doug's recommendation.  It includes a 6.3V tap for the heaters, and it works just fine.  I'm having some trouble with oscillation at some settings, but those on which it works sound incredible!  Listen to Doug's new sound clips and let your jaw drop.  This thing sounds awesome.  Build this amp immediately!  

Alex

Thanks!

If you're having oscillation problems, check your layout. It should not squeal at all on any setting.

Doug

Quote from: Alex CYes, the center tap is not used.   I'd say I could live with the 125 A also.   :)

If you have the center tap you can wire it as a full wave rectifier instead of a bridge and save 2 diodes.

Doug

OK, 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?

As a side note, I used to want to get one of those Allen Amp kits, but I just don't have the extra $1000-1200 right now. But, this project should satisfy my desire to build a tube amp, and is something I can actually use. The other thing I like about the FireFly project is that I can design the layout and choose what parts I want to use for it. I already have the layout designed, I just have to decide what transformers I want to use.

Quote from: Doug H
If you're having oscillation problems, check your layout. It should not squeal at all on any setting.

Doug

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

So 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.

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. :D  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! :D

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!  8)

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...

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?  8)

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?  8)

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?

smoguz:

Quoting the electric shock section at www.guitarnuts.com

"Failure of the guitarist's own amplifier places a lethal voltage on the "ground" side of the jack and thus on the strings.  This scenario is usually only encountered on early vintage equipment.  Even then such failures are extremely rare but when they occur they can place hundreds of volts DC on the "ground" side of the jack and the failure may be difficult to detect until the shock knocks you on your backside.  This failure is basically impossible with modern three-prong equipment plugged into a properly grounded three-prong mains outlet.  Never use ground lift adaptors on power cords!  
The shock path is from the amplifer, through the guitar chord to the guitar bridge and strings, to the guitarist's fingers.  From there the shock path either goes through the guitarist to the floor through his feet or through the guitarist to a grounded piece of equipment such as a microphone.  Even the first path through the resistance of shoes and floor covering may sometimes be lethal because the voltage potential is so high.  The second path is easily lethal because the path from the guitarist to earth ground has very little resistance to the flow of current."

I really don't know much about the electrical systems in Europe, I just know that it's higher voltage than we use in the U.S.
In theory you would have to ground the electrical system in your house in order to use a 3-prong power cord.

That's kinda hard, gonna have to tell my guardians to ground the place and I'm sure they won't do that. ;)

However, my SS amp has a grounded plug, and all the sockets in my room are ungrounded, but does that mean that I'm at the risk of being shocked? :shock: This is confusing... :roll: And it's kinda putting me off makin a tube amp simply 'cause I'm scared :lol:
Gonna suck up to the local tube amp man next week. Maybe he'll help me, he obviously lives in europe he must know more about the electrical system here... No offense to you Paul ;)

By the way, what's a 'ground lift adaptor'?

A ground lift adapter is a little thing you plug your 3-prong cord into, which effectively disables the ground connection to the wall receptacle - there is no connection to ground with this type of adapter. They are actually designed to enable one to plug a 3-prong cord into a 2-prong wall receptacle which doesn't have a ground. There is a little tab on the adapter that is supposed to be fastened to your j-box behind the receptacle faceplate, which will only work if it's made out of metal. Here in the U.S., all of those j-boxes in residences recently built are plastic, so the adapter is useless unless you run a wire from the adapter to some ground point, which can create hazards, too. But, all of the new buildings being built these days have a ground system, it's required by the building codes.
It's a common "trick" that people here use to try to get rid of hum problems. What people should be doing is finding the source of the ground loop causing the hum and dealing with that (if it is indeed a ground loop). Sometimes poor power filtering won't get rid of hum.

Anyhow, no offense taken.  8)

I could use a 30 foot grounded extension cord and run it from the laundry room to my bedroom, only when I wanna play through my tube amp or something like that. The laundry room (with the desired grounded plugs :twisted:) is right next door to my bedroom :D

But out of curiosity, if you don't connect the ground to the earth socket, where's all the current gonna go? It's not gonna disspate into nowhere... :roll:

The equipment that you plug into the wall receptacle will draw only what power it needs to operate. Grounding is a seperate issue. All your equipment has to do is make a complete circuit somewhere in its circuitry for it to operate.

The extension cord is a good idea.

That was the entire problem :roll: I can't see a circuit in the schemmos. Just a collective ground, but nowhere fro that ground to go. Am I missing something here?

does the 3rd prong of the AC plug go to the chassis along with all of  the star-grounding?
"-)

smoguz-

Electricity always wants to complete a circuit. In a circuit, ground is a common connection between everything in the circuit that goes to ground.
When you ground your main power supply, you are creating a path for the electricty to flow somewhere besides thru your body to ground in the event of a failure in the main power supply.

That is exactly what I was thinking. So without the grounded plug, the electricity would go through me and not anything else to ground, correct?

If that's true, europe's AC is wierd. Lemme check up on plugs here...

Correct.

As far as the wiring in Europe, it depends on how old your electrical system is I imagine. I would assume stuff being built today would be grounded, this should be an international standard today as far as I know.
There are older buildings in the U.S. with the same problem.

That is completely wierd because my SS 10W amp doesn't fry me without the grounded plug. There must be one hot and one cold pole or something similar.

This house is 25 years old... :? Maybe that has to do with it. The energy company's website is most uninformative too. :evil: Time for some extensive research ;)

Well, like the quote said, it's extremely rare to get electrocuted with those vintage amps that weren't made with grounded power cords, but it can happen.

Just pointing that out is all. It's a safety thing.  :wink:

Yeah I know but I'm rather safe than dead if you see what I mean ;)

But the whole problem for me is that the schematics for tube amps are all based around grounded plugs. Without the grounded plug, where's the current gonna go besides through me? :D I'd need to convert 'em somehow.

The chassis is acting as your ground. Where the problem comes in is if you have a failure inside the amp of some sort that puts a voltage on the ground side. It's going to want to take some path to ground, and it could be your body, if the power cord isn't grounded and conditions are right. It's rare, but it can happen.

:? :? :? Now I'm confused. The only chance of getting electrocuted, is when your amp fails and shorts, so there's a voltage on ground. OK, fine. But in electronics, there should always be a full circuit, right? Now look at the ax84 P1 schematic: http://ax84.com/media/ax84_m37.pdf

All those ground points connect to eachother, OK. Does the center point of all those points coming together act as ground? If so, no current can flow... :? So my guess was, OK it goes to the ground of the wallsocket. But now there is no grounded wallsocket... Am I missing a valuable piece of information here? Or will the current just flow to the ground point and somehow disappear? Could you explain that please, Paul? Where does the current flow back to?

Quote from: Paul MarossyWhen you ground your main power supply, you are creating a path for the electricty to flow somewhere besides thru your body to ground in the event of a failure in the main power supply.

in the event of a failure in the main power supply But whatabout when everything's working fine?

When everything is working fine, there is no problem. Agreed.
If you put a device between the hot and neutral in your wall receptacle, it completes the circuit and current will flow. These are the two prongs on an ungrounded power cord.

Okido. :mrgreen: But what about the DC from the power transformer? That goes to the chassis, right, after coming through tubes/resistors and whatnot.