assistance requested for building schematic (150 w guitar)

[a man called country]

okay. i'm crazy, but i know for what i need it would cost me at least 6 grand to have someone else build it to my specs - so what are they?

single channel
6 6L6s
? 12AX7s (PreAmp)
Switchable to 2/3 and 1/3 power (or half if that's all i can do)

controls:
-single input
-volume
-gain
-treble
-middle
-bass
-master volume
-power/standby switch
-wattage switch (50/100/150, 75/150)

driving 1-15" + an ext. sp. driving maybe 4-8"

okay, first off - how much of this is possible?
second off, is it possible just to use the output tubes for gain?
next, transformers capable of doing 150 watts?
last, a general schematic.

tall order, i know - in fact, ridiculous - but it's what the music calls for... so any suggestions (besides 'dream smaller') are much appreciated!

diggity:)

[dhuebert]

Interesting specifications, I wonder how you came up with them. 150 watts is HUGE for a guitar amp, I can't imagine ever needing more than 100 Watts and even that seems like alot.

Kevin O'Connor has a series of books called "the Ultimate Tone", maybe they can be helpful.

Driving a single 15" speaker is pretty doubtful here, most high watt setups use 4 or 8 - 10" or 12".

second off, is it possible just to use the output tubes for gain?

Why?

Keep talkin, this sounds kind of interesting.

BTW have you posted @ duncanamps.com?

Don

[a man called country]

well, as far as using the output tubes for gain, i guess the idea is something like 'jumping channels' on an old fender or peavey, whereby you've got the signal running back through the amp - and, well, 12AX7s can sound a little 'metalheadmarshall'

the idea here is something with the massive bright clean gusto of a steel amp - and those guys were running at least 150 watts back in the day through a good 15", but i also need it to break up really good - all i want is a really good clean amp that with the gain at 3 will just bite out - a real good dynamic sound, always with clean and gain to spare

i'm constantly finding myself drowned out, whether by some dude with a fender 165 watter or by a drummer who just can't hear where the music's at over his own playing - 150 watts is just so i have the power when i need it - and, besides, the best sounding amp i've really ever heard was the Fender Super Twin, made in the late 70s until 1981 and it was pushing almost 175 watts all-tube - a *sic* mitherfrickin amp

i will try and find these kevin o'connor books as well - thanks

[a man called country]

and, no, i haven't posted at Duncan Amps yet - should i?

(you're hammertone, yeah? the reason i found this site: seeking out the hammertones that the perp-people play)

[dhuebert]

Well now this is getting intereting! You say you've seen the Perpetrators, but you don't say where. If you're in Winnipeg we can get together with Randy Jamz, I'd be very interested to hear what he would say. Until then you can check out his website @

http://tone-lizard.com/

This sounds like a cool project, which is the only kind of project I'm interested in.

Don

[a man called country]

why did i ever take out library books for a girl??

man i wish i could just go scoop up a ton of books on elecrical and electronic theory right now - it was all in my head at one point!

i had a beautiful view, the first time i say nowicki play, but the times how they change(d);)

(oh, and thanks for your interest!)

[Shannon Parks]

.... the best sounding amp i've really ever heard was the Fender Super Twin, made in the late 70s until 1981 and it was pushing almost 175 watts all-tube - a *sic* mitherfrickin amp

http://www.ampwares.com/ffg/schem/super ... _schem.jpg

Good grief, that's an amp! Quite an ambitious project. Maybe you could build a 5F1 instead and mike it? :)

[a man called country]

well, the amp i plan to build isn't meant to havr circuits - just hand to hand wiring - i was just using the Super Twin as an example of a 165W amplifier:)

if i was going to build a little guy, i'd just go straight buying a blues jr - this amp i'm building in my head is a differnt thing - it's MY amp - and i play in a rock band, with a little amp that i mic, and it doesn't work - i wish it did, but, nope - it's time for the point to point hand wired 150w 'MAN CALLED COUNTRY' amp:)

[Gingertube]

What you need is a Hammond 1650T Output Tranny.
It a 1850 Ohms Raa unit with 40% Ultralinear taps and rated to 120W full power bandwidth for HiFi which means that you can easily get 200 Watts out off it in Guitar Amp use and 150 Watt for bass amp use..

Aside it will deliver 120W at 30Hz so will manage 240W at 60Hz and you don't need lower than that for guitar.

I have run the 1650T with 4 x KT88 in Ultralinear and +500V rails in a HiFi Amp. I got 122W at the onset of clipping and 138W in solid overdrive. At 50W Output response was flat down to 20Hz with waveform distortion due to output transformer saturation below 18Hz. That means it would deliver a full 150W down to about 3 x 18 = 54Hz.

For more output you need higher voltage rails than the +500V I ran with the 4 x KT88 OR (better idea) use your suggested trick and run 6 output tubes.

With 6L6GC in Ultralinear Mode you would not want to go above say 480 volts as you are starting to seriously stress the screen voltage rating. In any case use 1K 5W wire wound individual screen resistors on each output tube.

You will need cathode follower drives of the output tubes and the Super twin power amp section would be a good starting point for your design.

A caution:
I repaired a Fender Super Twin recently and the guy loaned it to his brother who turned it full wick with a Bass Guitar. Those flexible wire feeds to the voice coils on the speakers burst into flame - really, smoke, flames the works. So 2 x repalcement 100W 12" Fender speakers later it was going again (The Power Amp did'nt even blink and will still perfect after incinerating its speaker load).

6 x 6L6GC will drive the Hammond 1650T with ease. If its for Guitar run them Pentode Mode, if for bass then seriously consider running them in Ultralinear Mode (as per the fender Super Twin).

In either case - 2 x 100W 12" Fender speakers will probably not have enough power handling for it turned up to 11 (which by the way is ear bleeding - blow a way Marshall Stack volume). You will need to go to 4 x 10" speakers or 2 x 12" but of higher power rating.

For lower power setting there are 2 options:
1) Switch out 1 or 2 of the output tube push pull pairs. This can be done in 2 ways: either use a MOSFET switch in the cathodes OR remove the screen voltage from the tube pair.

2) Switch Tubes to Triode Mode - that will give a "warmer" sound at about 1/2 power.

Maximum Flexibility and easiest solution would be via a Triode / Ultralinear / Off switch for the screens on each push pull pair of tubes.
Hope there is something useful in this "rave". That would give the option of running anywhere from 25W to 150W and also some tone options such as one pair in triode mode with the other 2 pairs in Ultralinear.

Cheers,
Ian

[a man called country]

wow - i mean, i am the layman of laymen, so i only really understood about half of that, but i'll learn the rest - i mean, i already know two of the most important things now, the least of which is the output tranny - awesome!

yeah, that rant'll be mighty useful - i think i may even copy and paste it for easy access:)

thanks (gingertube) ian!

rnr

[sorenj07]

just my 2 cents: I've been running Sovtek 6L6WXT+ tubes in PP Ultra-linear fixed-biased for 55mA with a B+ of 500V on the dot, and they've lasted for a few weeks already.

[dhuebert]

I've been running Sovtek 6L6WXT+ tubes in PP Ultra-linear fixed-biased for 55mA with a B+ of 500V on the dot

55mA @ idle with 500V sounds kinda hot to me, I usually set them up at 35 mA @ idle. Opinions anyone?

I have run the 1650T with 4 x KT88 in Ultralinear and +500V rails

Sounds like you're describing the Hammertone BFA. With a 278CX and a 1650T I get ~ 160 W @ 1KHz running 535 V B+ and 55mA @ idle. But I sure wouldn't try this with 6L6s.

Don

[sorenj07]

the WXT+, by general consensus, is equivalent in construction to other GC's, and 27.5W of dissipation including screens should be well within tolerances. the screen voltage rating is another matter, but those 220 ohm 3w resistors in series with them ought to help a bit. if I had 470-ohm 3W resistors, i'd have used those instead.