a fine line between stupid and clever


Postby nineno » Sat Aug 22, 2009 12:29 pm

Hi all -
I haven't done much in the way of tube-amplifying recently and I decided it was time to fix that.

Of course, I need another hi-fi amp like I need a whole in the head. However, for the past several months I've been hanging out with and running sound for my friends' band. Two of the band members are co-workers and pretty good friends. Coincidentally, they're also both guitarists that opt for tube equipment.

One guys has a Mesa Boogie Lonestar, and the other runs a Marshall JTM800 (i think). Both guys swear by tube amps, but know fairly little about them. I've been trying to learn a bit more about the circuit insanity that's common place in guitar amps (power section distortion?!), and I think I'm ready to try building a head.

The guitarists suggested building a Marshall Plexi-style or 1974-style amp. (The alternative way of looking at this is that they both would like access to either of these types of amps...)

Given the phenomenal success I've had with the DIY Tube PCBs, I thought I'd look for someone that provides the same type of product for guitar amps. After about 7-seconds of googling http://www.guitaramplifierpcbs.com cropped up. The guy posts all of the schematics on B-sized sheets, hyperlinked parts lists in Excel, and the PCBs are reasonably priced (about $30 + s/h).

Unfortunately, he's out of the Superlite PCB (a ~30wt variant of the Marshall 1974), that I was hoping to order, right now.

Has anyone every ordered one of these boards? Any thoughts, suggestions, tips or general advice?

Thanks all,
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Postby Cygnus X1 » Sun Aug 23, 2009 5:25 am

Paying for drawings?
They are everywhere, for free!

Google these sites for kits, and drawings:
Weber Speakers
Metro Amps
Cygnus X1
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Postby nineno » Sun Aug 23, 2009 8:23 am

Oops - I wasn't particularly articulate with my first post: All of the information (prints, schematics, chassis layouts, parts lists, etc) is free on the afore-mentioned website. The PCBs are about $30.

Thanks for the other suggestions, though. I know I've looked at a couple of those sites, but probably not all of them.
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Postby ChrisAlbertson » Sun Aug 30, 2009 1:43 pm

nineno wrote:Oops - I wasn't particularly articulate with my first post: All of the information (prints, schematics, chassis layouts, parts lists, etc) is free on the afore-mentioned website. The PCBs are about $30.

Thanks for the other suggestions, though. I know I've looked at a couple of those sites, but probably not all of them.

No. Don't do it. PCB based tube amps are not easy to repair or modify. And when you "modify" a guitar amp you might be adding a gain stage or something, not just replacing a cap or something that smple. Also many people think the sound of a PCB is different. When it comes time to sell it, PCB abased tube amps don't get a good selling price. (because they can't be repaired or modified.) As an example I just bought a "dead" Ampeg 120 watt tube amp (four power tubes, good trnasformers but burned PCB for $100 because the owner could not kind anyone willing to repair the amp. even here in Los Angeles. They all told him it's cheaper to buy a new amp then the hourly fee to repair a PCB amp.)

Also, why build one? They are cheaper to buy. I have a brand new Fender Champ 600 that I bought at Guitar Center for $149. I could not buy the parts $200. If you want a PCB amp just buy one. You will not save money by building. The reason to build is so you can have a quality amp that you could not buy. Either a replica of a vintage amp or a one-of design. Buying a PCB will not get you either of those.

Don't pay for a schematic or layout. All of the classic designs are available on-line. If you want to build a Marshal, build a Marshal, just like Marshal did. Use "Turrets" These make for the neatest and cleanest build. Example from "Watts Audio" http://www.turretboards.com/images/PROD ... _tmb_2.jpg Hoffman will sell the parts for turret style building too. (But McMaster-Carr) has the best price on GP10 material and wire)

There are some good web sites for building differnt kinds of amps. I would suggest building a smaller practice amp first. Google "AX84" and build on of the amps there. Do the 100W high gain monster as your second build.
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Postby S4XAmps » Thu Sep 10, 2009 6:31 am

While I would agree that turret boards amps are more durable and easier to mod, I have built one the PlexiSE and it is a nice sounding amp. The boards Stingray designed are much more rugged than one you would find in most production amps. They also can be modded provided you use caution not to overheat them and lift the traces. He makes it pretty simple with the parts list, layouts, and schematics. It is true that techs do not like to repair PCB but I am going to assume you would not take it to a tech sine you are a DIYer.

If you decide on a hand wired turret board I would suggest www.AX84.com. It is a geat forum and they sell kits for the the amps at shop.dobermanamps.com.
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Postby rock_mumbles » Fri Sep 11, 2009 11:12 am

I recently built a "Baby Will" a guitaramplifierpcbs.com LiteIIb design. I recieved the last of the first run of pcb's and built up a slightly modified LiteIIb, I wanted some clean headroom so I changed out the preamp plate resistor. Now it is not a real LiteIIb 18W, but it's an amazing amp.

I just got a new v2.3 "Baby Will" circuit board for a friend, it's more robust board and has much better grounding and larger traces. The newer designed boards use soldered connections, (no faston connectors) and look really nice and build up quiet amps.
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Postby cartoonweirdo » Sat Sep 12, 2009 11:43 pm

To PCB or not..
a long standing debate in the guitar amp community.

My take on it is this: If you are going to build it, send it out into the world, and forget about it until it's time comes and it goes back on your bench you need to ask two questions.

Am I being paid?, and

Do I have time for this crap?

If you are going to make your name as a legendary amp builder (step right up Mr. Fender..) you need to ask two other questions.

What does my future customer base think of PCB's?, and

If they don't like them can they afford to pay me to wire the amps by hand?

A PCB design will eliminate all lead dress and wire routing issues out of the gate as long as you connect the parts correctly. That's no small potatoes if your circuit is even slightly complicated (say a super-reverb).

Also (regardless of popular opinion) a properly designed PCB amp has BETTER treble response (ever seen a hand wired microwave, or cell-phone?), less RFI, and the ability to add features everyone wants (reverb, effects loop, chorus, phase, etc) at a low cost to you.

A hand wired amp will be MUCH easier to repair, much more time consuming to build and teeth, and have a "worse" sound. Guitar players like a "worse" sound and that is your current issue.

Old iron and glass running under duress make some of the most compelling sounds I have ever heard when routed through some old speakers. Those sounds all depend on the fingers producing them, and there begins your trouble.

If your guitar player friends play well it might not matter what they play through. If not, a classic design will help them sound better.

As a passable guitarist who did well for himself based on the sound of his equipment I have the following advice:

Keep it to "50" (usually an honest 20 or 30) watts or less

Don't make it complicated.

Limit Bass (I know guitar players want it, but it hurts them).

use a speaker, or combination of speakers, that rate close to the "max" output of your guitar players amp.

Beef up the PWR tranny, skimp on the OPT, use a choke, use a combination of speakers that allow the lowest possible impedance tap to be used on the OPT (2 ohms for a "fender" design, 4 ohms for a "marshall") Old tubes really do sound better (especially 6V6's)

If it sounds like it's going to blow up but it doesn't you have won.

Hope that helps,
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