hi all
you will be pleased to know i have finally finished my firefly!!!
it has exceeded my expectations. it sounds absolutely AWESOME!!! i couldnt believe it when i discovered the problem lay in my not insulating the bottome of the tagboard properly, and the B+ voltage was going through a resistor straight to ground. i thought i was getting little tingles. so anyway i stuck some bits of plywood under the board and it works like a charm.
i added a marshall tonestack to it. it cuts the volume a bit, but its worth it. the mids knob acts a little like a drive control when its being pushed by a distortion box, its a nifty little feature.
my only complaint is that is not quite as loud as i would have liked it to have been. is there any way to make it louder, like add an EL34 stage on the end or something? but that will lead to having to get a more hardcore output transformer i suppose, and theyre not cheap.
i have to get a decent speaker though, im just running it through a $10 PA extension speaker from jaycar. im sure ill stumble across a good deal sooner or later.
but overall, build one NOW. it makes everything you play sound better. in the transistors vs. tubes debate, transistors suffer a horrible, brutal, humiliating defeat.
cheers
Jim
there is a 7 watt pentode that is a dual similar to the 12au7. also you could make it stero.
Guitar speakers normally have a high efficency. This means more sound from the some wattage. Get a good speaker first and see how this turns out.
I have a 5W 6V6 single ended amp, with a Celestion Vintage 30 and it's very, very loud.
Bye,
Joep
Congratulations! 8) :D
You have a couple of options for boosting the power. The first is without question using an efficient guitar speaker as Joep mentioned. That's essential. I have a 10" Celestion from a little Marshall combo that I blew up ;) a while back. It makes quite a difference comparing loudness between this and other "general purpose" 10 inch speakers.
You can always change the tube as well. Try a 12BH7 ONLY IF you have the heater current to run it. It pulls twice the heater current but will be louder and has the same pin-out. Switching to an octal base, you could use a 12SN7.
If you add enough filament capability, you could also use two EL84s in the same circuit. See: http://www.triodeel.com/compact.html
You should also try different brands of 12AU7. I would suggest an ECC81 from Ei because of its big plate size.
Take care,
-Peter
Quote from: jimmyhi all
you will be pleased to know i have finally finished my firefly!!!
Congratulations!
Quote from: jimmy
my only complaint is that is not quite as loud as i would have liked it to have been. is there any way to make it louder, like add an EL34 stage on the end or something? but that will lead to having to get a more hardcore output transformer i suppose, and theyre not cheap.
Peter beat me to the punchline, but he is right, try a 12bh7 but make sure you have the budget for it with your heater current. According to the reports, tonally it will sound the same but it will be louder.
Quote from: jimmy
i have to get a decent speaker though, im just running it through a $10 PA extension speaker from jaycar. im sure ill stumble across a good deal sooner or later.
Right now, Avatar Speakers (www.avatarspeakers.com) has Celestion G12H80's for $42 ea. I just bought a G12H30 from them and couldn't be happier with my sound. The Firefly absolutely smokes through this speaker. I have not personally heard the G12H80 (80W version) but in soundclips it sounds similar to my 30. Anyway, this has been the last missing element in my sound to completely cop that hi-gain marshall tone in one and half watts. :D
Quote from: jimmy
but overall, build one NOW. it makes everything you play sound better. in the transistors vs. tubes debate, transistors suffer a horrible, brutal, humiliating defeat.
cheers
Jim
Thanks! I will add that if you get at least a 1x12 closed-back cab with a celestion you will not be disappointed.
(Also, I just did a minor tweak I love- sub the .68u cathode bypass cap in the 2nd stage with a 10uf. This really fattens up the bass. I'm debating whether I'm going to add back the "bass resonance" control from the original schem or leave it as is.)
Doug
congrads jimmy~
if you don't mind, i am curious as to how much you have invested $ wise into this project.. i am looking at that or the P1.. but i am jobless for a couple more weeks..
also:
is this little amp gigable, with a good house PA?
thanks,
weeeeell, i think all up i put about $300 AUD into this. it was $100 in bits and pieces, as high voltage caps arent cheap. then there were the important bits like the output transformer and tubes. i needed 4 tubes; i smashed one, and i have a spare now. they cost about 150 bucks, 50 for the transformer, and about 20 each give or take for the tubes. and then theres misc stuff, knobs, lights etc. well worth it in my opinion. and the experience was priceless :D it was my first tube, amp, and high voltage build and i feel all the more capable for it.
i think you probably could gig with it under the right conditions, definately get the louder tube, find a tonestack (if any) that doesnt eat much power, and get a good speaker. make sure your PA is well capable of delivering the extra wattage if you need it though.
cheers
Jim