DIY Guitar amp

[lassoharp]

Do you think it's a case of changing the bias point of the AX7/ AU7?

No.


It has more to do with output headroom.  Champ is simple SE 6V6.  Switching to Au7 does keep things cleaner only because you are losing gain.  The limits of the output stage are already set.  Just guessing here but like most all Fender amps I would assume that Fender designed the Champ to be as clean as possible for the given circuit.


But yes, a SE 6V6 can be ran somewhat clean but only at very low volumes - much lower than most guitarists are accustomed to using them at.  But still call that semi-clean when compared to a Twin Reverb.  If just for recording this may work fine for your needs.


You may want to consider the 5E3 Deluxe (PP 6V6).  Yes, they are know for dirty gnarly Neil Young tones but like a Champ will be somewhat clean at very low volumes.  The bigger speaker and higher power will afford slightly better volume in the cleaner range.

The one thing that will help greatly in keeping a Champ or Deluxe clean sounding under higher volume conditions is by using a BIG PA type speaker like a JBL or near equivalent such as the Weber High Powered Ceramic series.  Also,  avoid OT saturation by using a hefty OT.  Some people purposely use a small core OT for distortion effects.  The original Champ OT is probably midway between oversized and undersized.

 

[alexc]

> But still call that semi-clean when compared to a Twin Reverb

Never was truer a word spoken!

Is there anything in the known universe as painfully clean as a 70s silver face Twin ?

You can shave with one of those.  ;D

I'm pretty sure I still have hi-freq ringing in my ears from a single night in the 80s on stage with one of those only half way loud.

 

[lassoharp]

Is there anything in the known universe as painfully clean as a 70s silver face Twin ?

Maybe a Roland Jazz Chorus.  8)  . . . oops that's a SS amp!

 

[usekgb]

My JC120, loaded with JBL E120's is the loudest and cleanest amp I'm ever played!  But, it's SS.  It still kicks some ass though! 8)

 

[alexc]

Have to say I was a big fan of the JC120.  With a 335, finger pickin  ..

Pure Smiths.. 80s style ..

Sigh .. wish I was there again  :'(

 

[pstamler]

Do you really want clean? Or do you want some nice dirt?

If the latter, looks for a really skimpy output transformer, Champ style. Then think about pushing it with a single-ended EL84, driven by a 12AX7 or maybe a 6SL7. Suddenly, you're in Chicago and it's 1961 all over again.

Peace,
Paul

 

[AMZ-FX]

The AX84/Champ sound will also vary based on the speaker choice. I built one of the first AX84 amps when it was being developed, and used a 10 inch speaker with a big magnet.  It is quite loud, and (mostly) clean.  Single coils will be a bit cleaner than humbuckers, usually.

http://www.muzique.com/ax84.htm

Best regards, Jack

 

[Junction]

If you haven't checked these guys out before, you should http://www.ceriatone.com, I have 5 of Nik's amps and have just ordered another one. Pricing is great, if you let them build it, their build quality is the best or as good as anything I have seen anywhere in handwired amps. I have a Ceriatone JCM800 and Marshall JCM800 and many guitarists have tried both in the studio and can't pick the difference in tone, however the Ceriatone is a much better build than the Marshall.

 

[DaveP]

Speakers and cabinets have more influence on the sound with clean amps.

Try the Celestion speaker sound sample site, Celestion blues sound wonderful.

Open back cabs a la vox have twice the output except where the bass cancels.

Vox circuit has no feedback but is cheap to implement with just a pair of EL84 (15W)

Same with Marshall and you can scale down a 4x12 closed cab dimensions for one G12 greenback

best
DaveP

 

[lassoharp]

Speakers and cabinets have more influence on the sound with clean amps.

I'll ditto that and emphatically add that that holds true for dirty amps.  I would actually say even more so on dirty amps like a Fender Champ.  Can't emphasize that enough - night and day, sink or swim, smash or suck kind of deal there most of the time.  The speaker breakup is crucial to final sound and cab type can fence it in or let if fly.

And don't forget about the OT.  When they're too lopped off at the ends saturation might give you more 1K centered response than you want.

Most Marshall heads depend on the massive low end boom the Marshall cabs provide so it's a great compliment.  Marshall head through Fender 2 X 12 sounds very tinny and brittle.  Fender head through Marshall cab has you reaching to turn the bass down all the time.

 

 

[JohnRoberts]

Guitar amps are an extension of the musical instrument so everything is in play, and reproduction linearity is not the top design goal. The difference between making musical sounds and reproducing existing sounds.

JR

 

[bahrens]

I think a tweed deluxe would be a good option.  It's not that much more complicated than the champ and you could gig it if you wanted to, plus you'd have a lot more headroom to work with than you would with the champ. 

My first build was a scratch-built 100W two-channel amp.  I'm not saying that's a great first project but if your solder skills are decent and you can follow directions you can build just about anything, so I recommend finding the amp you want, then building that, rather than picking a project based solely on how easy it is. 

Ampgarage, as mentioned, is a really cool place, or at least it was when I used to hang out there ages ago (I haven't been back in a few years).  Never hurts to take a site like that, start with the oldest posts in the "technical discussion" subforum, and just start reading. 

 

[analogstud]

Is there anything in the known universe as painfully clean as a 70s silver face Twin ?

Yes. Ampeg V-4 (with better reverb, to boot!)

 

[Dr_J]

maybe checkout www.tube-town.net

 

[ethervalve]

Some nice info on this thread (I wasn't aware of AX84.com).
Got me thinking about something:
I recall reading a recording book a few years back where the author said that it was fairly common for session guitarists in Nashville to have a Jensen transformer fitted into their Teles. I'd assume they were using this balanced out for DI purposes, but I'm curious if any of you have ever experimented with a transformer balanced system with your DIY amps (with modded guitars)?

 

[deuce42]

I agree with the Tweed Deluxe option - its commonly called the 5E3 circuit and is usually a starting point that most people who make guitar amps undertake if they dont do the champ. On ebay or any of the guitar amp building sites (i.e. equivalent sites to this but focused on guitar amps), you can buy a premade turret board for the 5E3. All you need to do is add components and wire up. Its got a few more components that the champ but is a lot more versatile and should retain clean character far more than the champ.  Its truly got a classic fender tweed sound to it. Using good sprague caps and cloth wire will make it sound far superior to the current fender factory produced models. I think you will be honestly surprised by just how high end boutique it sounds if you build it.  It will go from beautiful old school crystal fender chime to a thick ZZ Top crunch just with the guitar's volume control - just ask Billy Gibbons, Neil Young or Derek Trucks who famously use this setup and have made their signature sound from the 5E3 this way.

As noted above, the output transformer is the most important thing electronically (that is, the cabinet and speaker are usually more important still) and I think you can get the best gear/price balance for output xformer's at Magnetic Components in their "Classictone Range".

Truly, there's so many layouts, diagrams, parts easily purchased and info about the 5e3 it's almost the benchmark for most people's initial tube guitar amp builds.

As for clean headroom, the fender twin reverb retains complete clean all the way through because it's a very high wattage output amp for its  preamp and power amp circuit - that is to say that the Deluxe Reverb, Super Reverb and Twin Reverb are all the same circuit using exactly the same circuit board - the difference is their output wattages are different and their cabinet size and speakers are different.  The lower wattage Deluxe and Super's distort more accordingly.  The twin reverb also imparts permanent lower back damage to the poor schmuck musician who carries one around.....

 

[chipss36]

Built champs, ax84, just did not do it for me , dig in on the low strings and
It distorts, if I could do it again knowing what I know now , the tweed deluxe would be the
Best starting point, many great kits for it , not a whole lot more to it than a champ, and useful tones
Still have my deluxe , and still dig it, my champ and the ax84 all sold off long ago.

 

[letterbeacon]

In the end I decided to build a 5E3.  I used Mercury Magnetic transformers and a Jensen P12Q and I'm getting nice warm clean tones.  In fact I can't seem to get it to overdrive at all, which suits me!

Here are a couple of pictures.  It's yet to be covered, and I need to countersink the screws holding the speaker in still.

 

[chipss36]

Very nice work, looks great, tasty tube choices ......well done my friend.

 

[letterbeacon]

Thanks!  It's so well documented that it was a bit of a no-brainer build really.  Can't wait to get it covered!