who knows about guitar amps?

[Tom Mobley]

friend of mine has heard my DIY LaScalas, Belle and the big DBB Cornscalas. He's bugging me to build him a guitar amp. I've got enough stuff to build a decent 6BQ5/7189 P-P amp and was thinking to use a Crites cast frame 15". It won't have any tone controls or other effects, he'll do all that with his pedals.

I was thinking to build a traditional open back box, direct radiator setup. Will the K-33 type driver go high enough to do a guitar? Or do I need some other driver completely? I've heard that you can't use quality stereo components in a guitar amp but nobody sez why? I mean, they'll play a guitar from a recording, right?

I need to go look up the range of the k-33 type woofer and see how that compares with an electric guitar.

Any bright ideas?

[Guest " "]

almost all the guitar heads I know would rather have 12" or 10" drivers rather than 15" or 18" drivers. The diameter of the driver has a lot to do with the upper frequency limit of the driver and as you go bigger in driver size, the upper frequency limit gets lower, resulting in an incomplete tone. On the tube front, the tube of choice amoung guitar heads is the el-34 tube, again, for the best tone.

[artto]

friend of mine has heard my DIY LaScalas, Belle and the big DBB Cornscalas. He's bugging me to build him a guitar amp. I've got enough stuff to build a decent 6BQ5/7189 P-P amp and was thinking to use a Crites cast frame 15". It won't have any tone controls or other effects, he'll do all that with his pedals.

I was thinking to build a traditional open back box, direct radiator setup. Will the K-33 type driver go high enough to do a guitar? Or do I need some other driver completely? I've heard that you can't use quality stereo components in a guitar amp but nobody sez why? I mean, they'll play a guitar from a recording, right?

I need to go look up the range of the k-33 type woofer and see how that compares with an electric guitar.

Any bright ideas?

Tom, the reason for not *usually* using quality stereo components in a guitar amp (or *musical instrument* amp) is primarily two-fold.

One, musical instrument/pro audio equipment is usually designed to take a lot more abuse. Reliablity is major factor. Repairs take time and time is money for professionals who make a living with it. The equipment is usually designed for heavier duty and heavy duty doesn't always go hand in hand with fidelity and may in fact come into direct conflict with it (think dump truck verses Cadillac CTS ~ they might both have the same horse power but the engine/drivetrain is made and tuned quite differently and suits a different purpose).

Two, musical instrument amplifiers, guitar amps in particular usually are designed with a particular coloration or signature in mind. They are sources of sound *production*, not reproduction. The amplifier/speaker combination is part of the electric instrument's "sound".

Are there exceptions? Of course. And nowadays, there are certainly a lot of "boutique" amps out there, usually costing $$$$. And there are also some vintage amps that were made that way too. But overall it's usually a coloration and application issue.

[Marvel]

Tom,

Triode Electronics has some guitar amp kits (there are others available on the net as well). At least you would know the type of sound you wouldbe getting. Tons of schematics are also floating around, so you couldpick the kind of amp you want to build.

Bruce

[Tom Mobley]

Thanks for taking time to reply guys.

Looks like it needs to be able to get up to at least 3KHz, maybe 4, that's going to be tough on a 15. I looked at the 15s at PX, looks like if they go up near there they're 10 or 20dB down.

artto, your comments are well taken, as always.

can a P-P EL-34 make 30 watts?

[Marvel]

Tom,

My older son (Invidiosulus on here) had a Mesa Boogie amp with a single EVM12L (if I am remembering correctly) that sounded incredible. Plenty of high end.

Bruce

[artto]

I forgot to mention that it may also depend on the kind of music it will be used for. For instance, a lot of rockers seem to like 4x12 cabinets. A lot of the pop and jazz guys I know seem to like 2x10 or 2x12. Many of the blues guys like a beefier sound and often use a single 15.

[dwillie]

I agree with SF on the 15" being too big a speaker. Most guitarists I know seem to prefer single 12, dual 12 or quad 12's. Celestion makes a great speaker for RnR or Blues. Marshall amps used this brand almost exclusively. Jensen was also used in Fender amps forever. You can buy these speakers pretty cheap from the big box music stores. Fender used a lot of open back boxes, while Marshall used sealed backs. Tubes sound wonderful on guitar amps. The tubes and pre-amp sections color and saturate the sound on purpose. You'll find el-34's in Marshall's and 6l6-GC's and 12AX7's in Fender and Mesa Boogie. d.

[mustang guy]

I built my son a Bill Fitzmaurice XF-212, and connected a tube head to it. The drivers used were the Eminence Swamp Thang's:

http://www.eminence.com/speakers/speaker-detail/?model=Swamp_Thang

The drivers are mounted on a motorboard which tilts them upward, and crosses them, which provides an incredible soundstage. The back is removable, for open and sealed operation. I could have used rare earth magnet drivers to lighten them up.