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Low Powered Guitar Amp Head

92.12.235.191
Posted on March 2, 2015 at 05:28:37
Stephen R
Audiophile

Posts: 1428
Joined: January 11, 2002
 I've been asked if I could make a low powered guitar amp head. The guys have asked that the speaker in their combo be used but could a low powered valve head make the sound they want without blowing the walls down.

I'm not entirely sure where to start but I'm thinking a few watts max. Maybe single ended, maybe PP. Possibly using some of the cheap Hammond OPTs.

I've seen some commercial offerings using 12AX7 front end and even 12AU7 PP output or 6SN7 outputs. Maybe EL84 SE.

Most of the components I have already to see what will happen.

Sound wise I think they're not after a super clean sound. They're bluesy/rock in their preferences. The idea being it can make the sound they're after with a Mex Strat.

All sounds pretty vague to me so any ideas, places to start and so on appreciated. Also bear in mind, I don't play or own a regular guitar although I do have a bass (which may not be much use here)

cheers,

Stephen

 

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RE: Low Powered Guitar Amp Head, posted on March 2, 2015 at 05:49:04
Blackdog
Manufacturer

Posts: 1505
Location: Ontario
Joined: March 20, 2006
 A good place to start


Dan Santoni

 

How Low Is Low?, posted on March 2, 2015 at 06:20:05
FlaCharlie
Audiophile

Posts: 940
Location: Gville, FL
Joined: June 1, 2003
 Hi Stephen - Exactly how little power are they after? The obvious suggestion would be to build a Fender Champ clone, or one of the many variations on that theme, for about 5 watts.

Is that too much power? What are they using now? Do they use distortion pedals or go straight into the amp?

. . . Charlie

 

5F1 tweed era Champ clones, posted on March 2, 2015 at 06:25:06
FenderLover
 A good starting point. Many DIY's out there for this amp. Triode, Mojotone, Weber, and Marsh have some nice kits.

Mojotone link:

http://www.mojotone.com/amp-parts/amp-kits-tweed-style/Mojotone-Tweed-Champ-Style-Amplifier-Kit

Marsh link:

http://store.marshamps.com/product_info.php?cPath=21&products_id=28


Weber link:

http://wiki.diyrecordingequipment.com/projects/weber-5f1-fender-champ-kits/

 

RE: 5F1 tweed era Champ clones, posted on March 2, 2015 at 06:36:21
FenderLover
 Original layout and schemo. I like this circuit. No tone stack. Very nice vintage OD tone.


Triode layout:

site.triodestore.com/5F1layout40-18019.pdf

 

Love the small ones..., posted on March 2, 2015 at 07:46:04
Gordon Rankin
Manufacturer

Posts: 2928
Joined: June 9, 2000



Stephen,

I have made over 120 20W or under amps now. I have two favorites right now the MPC (Magnetic Phase Coupled) PP 6V6 ~18W seen here used by Barenaked Ladies front man Ed Robertson Orange/Light Blue (That's Keith the Guitar Tech). Or my RFC (Reactor Follower Coupled) direct coupled SET output stage KT88 ~12W Purple/Black. The Black amp is a 300B SET amplifier, really nice for jazz guys.

I have made amps with EL84 (not really my fav), 6V6 (really like), KT88/6550, 7591 (nice sound, far better than the EL84, same vibe), ECL86 really cool 3W amp.

After building tons of amps with 12AX7's I find they really suck the life out of amps. I use the 6072A now for everything and it works so much better. You could easily make a 6072A to a 7591A and make it work great. Use a rectifier tube, solid state makes things suck.

I just finished a number of all silver mega $$$ amps and they were all killer some pics over on the MageneQuest forum.

Thanks,
Gordon
J. Gordon Rankin

 

RE: 5F1 tweed era Champ clones, posted on March 2, 2015 at 09:59:54
FlaCharlie
Audiophile

Posts: 940
Location: Gville, FL
Joined: June 1, 2003
 I based the junkbox Champ that I built several years ago on this circuit and it sounded really good. I made a few changes because I built it in the chassis of a SE 6BQ5 console stereo which only had 9 pin sockets so I used an EZ81 rectifier instead of the 5Y3 and 12AB5 output instead of the 6V6. One of the original OPTs was replaced with a 12.6v filament transformer to power the 12AX7 and 12AB5. Used a 10" speaker from a console stereo. Gave it to a former student as a graduation present.

. . . Charlie

 

RE: Low Powered Guitar Amp Head, posted on March 2, 2015 at 11:38:51
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 Put an L-pad in a box and have them try that first. If it's the amplifier distortion that they like, that will do the trick. If it's the speaker's breakup character that they are after, that won't really happen with a small amp anyway.

 

RE: Love the small ones..., posted on March 2, 2015 at 12:18:32
Stephen R
Audiophile

Posts: 1428
Joined: January 11, 2002
 Thanks Gordon. There's some great ideas in there. I've never really liked the AX7 but thought as it's a guitar amp, I may have to use them. The 6072A I really like so that's good news as I have some of them too. I was going to use a rectifier valve as I dislike SS rectification.

This will be interesting as guitar amps are I believe, kinda like instruments too of a sort. So it will be a complete departure from the sudio stuff I've built to date. Never done single ended either so that should be fun.

Is your reactor follower coupled concept a choke loaded cathode follower direct coupled to an output valve? Of course you don't have to say if that's something you want to keep to yourself ;)

cheers,

Stephen

 

RE: Low Powered Guitar Amp Head, posted on March 2, 2015 at 14:40:28
sony6060
Audiophile

Posts: 1465
Location: USA
Joined: August 8, 2014
 A simple single-ended 6V6 design like a Fender Champ. I like the octal base single section 6SF5 preamp tube sonics vs the common 12AX7s. Ceramic coupling capacitors makes for more of a Marshall sound.

 

RE: Low Powered Guitar Amp Head, posted on March 2, 2015 at 15:00:53
Russ57
Audiophile

Posts: 3754
Location: South Florida
Joined: November 16, 2001
 Never built such a thing....but I have to vote for 6V6 too. I have come to develop a love affair, albeit triode wired.

 

Champ variants, posted on March 2, 2015 at 15:14:10
FenderLover
 I have the 5C1 Champion with the 6SJ7 input tube. Sometimes, I like it better than my 5F1. Browner, creamier tone. Great with humbucker pickups.

5C1 is about as simple an amp you can make. 8^)

 

RE: Low Powered Guitar Amp Head, posted on March 2, 2015 at 18:20:38
REL54
Audiophile

Posts: 1944
Location: Virginia Coast
Joined: January 3, 2003
 I was going to suggest the AX-84 but Blackdog beat me to it. I built a clone of the Fender Vibro-Champ for our son. Worked great. It had a little hum that I could have eventually gotten rid of but as soon as he got it, I could never get it back to work on it.

I used a 5U4 for the rectifier instead of the 5Y3 because I had a box full of the old "coke bottle" type 5U4s. I also used a 6L6G as the output tube instead of the 6V6. I just dig the groovy look of the "S" shaped tubes.

Actually, he would change the output tube from the 6L6G to the 6V6 to get a different sound.

One good thing about Fender amps is that all of the schematics and layouts are FREE online.

In any case, I wish you luck and please do keep us up to date on your progress.

cheers,
roN

 

RE: Love the small ones..., posted on March 3, 2015 at 00:30:12
Stephen R
Audiophile

Posts: 1428
Joined: January 11, 2002
 In looking about the net, I think I the answer to my question thanks.

cheers,

Stephen

 

Lots of Ideas Here, posted on March 3, 2015 at 06:45:02
FlaCharlie
Audiophile

Posts: 940
Location: Gville, FL
Joined: June 1, 2003
 Here's a link to a cool website dedicated to lower powered guitar amps - which they define as anything up to 15 watts. Not all the amps listed are still being produced and many designs were likely never produced commercially, but it's a good source for ideas.

. . . Charlie

 

Vox Lil Night Train amp, posted on March 3, 2015 at 08:45:47
FenderLover
 Always intrigued me. Never did get to play on one.

 

5C1 demo, posted on March 3, 2015 at 11:46:52
FenderLover
 Best YT link I could find that demos the more "rounded-off" tone of the 6SJ7-6V6GT driven Champ. Really, a very sweet tone. BTW... I like the red RCA 5693 in place of the 6SJ7.

----

 

RE: Vox Lil Night Train amp, posted on March 3, 2015 at 12:22:32
Stephen R
Audiophile

Posts: 1428
Joined: January 11, 2002
 It was something along those lines that got me started looking at this.

 

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