Hello, first post here.
I recently built my first guitar tube amp. The amp was based on an AX84 20W Push-Pull project, but came out a bit different. I used a pair of 6L6 instead of the suggested 6V6 with minor modifications on the power amp, chokeless power supply (don't know if that was a very good idea), and amplimo toroidal transformers. So now it's about 40Watts, loud enough for me.
As a preamp i used the Lead schematic from the same site, which was total crap. Wait, to be honest it was not crap, it just wasn't what i wanted. What i wanted was modern American hi-gain tone, a bit like mesa/boogie.
So i'm thinking of replacing the preamp channel with this preamp section from the 2 channel Mesa Boogie dual rectifier. Here comes the hard part. I really don't think i should try this one on point-to-point. Does anyone have the pcb for this preamp? I've searched for a couple of threads, but i didn't see a pcb anywhere... An alternative is a mark IV. (which is, i think, identical with the mesa/boogie formula. I've tried this directly to the power amp and it sounds amazing...)
Any ideas?
thanx a lot
I recently built my first guitar tube amp. The amp was based on an AX84 20W Push-Pull project, but came out a bit different. I used a pair of 6L6 instead of the suggested 6V6 with minor modifications on the power amp, chokeless power supply (don't know if that was a very good idea), and amplimo toroidal transformers. So now it's about 40Watts, loud enough for me.
As a preamp i used the Lead schematic from the same site, which was total crap. Wait, to be honest it was not crap, it just wasn't what i wanted. What i wanted was modern American hi-gain tone, a bit like mesa/boogie.
So i'm thinking of replacing the preamp channel with this preamp section from the 2 channel Mesa Boogie dual rectifier. Here comes the hard part. I really don't think i should try this one on point-to-point. Does anyone have the pcb for this preamp? I've searched for a couple of threads, but i didn't see a pcb anywhere... An alternative is a mark IV. (which is, i think, identical with the mesa/boogie formula. I've tried this directly to the power amp and it sounds amazing...)
Any ideas?
thanx a lot
I took a quick look at the schematics and it's your basic Marshall preamp with a cascode gain stage, plus a long tail pair PI. This is your basic formula for Marshall tone.
The 6L6 power amp has negative feedback, which is going to give it a nice Fender clean sound, with the preamp distortion on top.
One simple mod may be to lower or disconnect the feedback, which usually adds grit.
Taking out the choke would make the amp more responsive, especially at high volumes.
The big question is what speaker are you using?
I'd recommend against the Mesa Boogie preamp. Stick with the well known: Fender/Marshall.
You may also want to ask on the Hoffman board, which is more for guitar
http://www.el34world.com/Forum/yabb2/nph-YaBB.pl?board=TubeAmpBuilding
The 6L6 power amp has negative feedback, which is going to give it a nice Fender clean sound, with the preamp distortion on top.
One simple mod may be to lower or disconnect the feedback, which usually adds grit.
Taking out the choke would make the amp more responsive, especially at high volumes.
The big question is what speaker are you using?
I'd recommend against the Mesa Boogie preamp. Stick with the well known: Fender/Marshall.
You may also want to ask on the Hoffman board, which is more for guitar
http://www.el34world.com/Forum/yabb2/nph-YaBB.pl?board=TubeAmpBuilding
spresv said:
You appear to be a beginner at this.
There's tons of info on Marshall/Fender tone stacks, and a lot of people can offer advice on mods to get the tone you want. Not so with the Mesa/Boogie.
Also, the preamp you chose is for the heavy metal sound. So, there must be something else going on.
I have one of those 10" Marshall speaker cabs (for the mini stack) and replaced the speaker with a Celestion, which sounds much better.
Have you tried major changes in the tone settings? It's not uncommon to have to put the bass and treble at 1 or 2, especially if you want thick mids.
Also, the easiest mod is to put in a lower value bright cap, or remove it. This usually changes a thin sound into thick and heavy.
The guitar is the last piece of the tone puzzle. Single coil guitars sound thinner that humbuckers.
Add all three (Strat, cheap speaker, bright amp) and voila ... a bright and thin amp!
if you built the HO preamp, I don't know why you had problems with it as it nails the early marshall tone dead on, and has loads of gain. You gotta have good tubes however. I have a JJ 12ax7 in V2 location and a '64 sylvania 12ax7 in V1. Replace V1 with a 12au7 and you've got vox ac-30 sounds. I have loads of early RCA cleartops that sound great in this amp 
the HO will not do mesa-boogie style distortion, but you should consider putting a pedal in front of it and see.
EDIT: My amp is the SE 5 watter... I have gigged with it live with a drumkit. Couldnt believe how loud it was through a 2x12 cabinet..( for 5 watts) till I checked the bias ... 60ma @ 275v!!!!!
Must have crept up on me.. Best of luck!
the HO will not do mesa-boogie style distortion, but you should consider putting a pedal in front of it and see.
EDIT: My amp is the SE 5 watter... I have gigged with it live with a drumkit. Couldnt believe how loud it was through a 2x12 cabinet..( for 5 watts) till I checked the bias ... 60ma @ 275v!!!!!
Must have crept up on me.. Best of luck!
If you strip away all the bells and whistles, the Dual recto preamp is just ripped off the Soldano SLO. Go to the SLOclone forums to find PCB and also turret layouts for it. I have built several variants of that style of preamps myself in both turret board and free wired true PTP, and it is just fine if you have the component layout and wire crossings right.
Thank you all for your replies!
What gave me away
I've done all that. along with a stopper resistor, plain 1.5K on the cathodes, 150 instead of the 470pF in the tone cotnrols, and a switchable cap in each gain control. It sounds much more bright, less harsh gain, more distortion, but it still isn't what i want. Great tone for classic rock though.
This is really interesting. I'm waiting authorisation from the admin to see if i can find anything usefull.
Thank you all!
PRNDL said:
What gave me away
I've done all that. along with a stopper resistor, plain 1.5K on the cathodes, 150 instead of the 470pF in the tone cotnrols, and a switchable cap in each gain control. It sounds much more bright, less harsh gain, more distortion, but it still isn't what i want. Great tone for classic rock though.
aletheian said:
This is really interesting. I'm waiting authorisation from the admin to see if i can find anything usefull.
Thank you all!
>> Great tone for classic rock though.
I'm finding the same thing with my builds, which are Matchless Spitfire clones.
They have a single preamp gain stage, tone stack and LTP.
The distortion is blues and rock, bordering on metal with the amp on 10 and the right speaker.
For my next build, I'm considering adding an additional preamp gain stage with the unused 1/2 of the first tube.
The secret for us beginners is to find an amp that is similar to what we want to build, so that we can be reasonably sure that it will sound cool when we're done.
I've been looking at Trainwreck Express schematics, which have 2 gain stages.
I'm finding the same thing with my builds, which are Matchless Spitfire clones.
They have a single preamp gain stage, tone stack and LTP.
The distortion is blues and rock, bordering on metal with the amp on 10 and the right speaker.
For my next build, I'm considering adding an additional preamp gain stage with the unused 1/2 of the first tube.
The secret for us beginners is to find an amp that is similar to what we want to build, so that we can be reasonably sure that it will sound cool when we're done.
I've been looking at Trainwreck Express schematics, which have 2 gain stages.
That I did wrong. I started the project without knowing what it would sound like at all. I figured "lead ch" would be kinda metal. Well, things are not so simple, i got that for sure.
Oh, almost forgot, i play on an Epiphone SG Limited edition blah blah, with humbuckers, and occasionally on a Gibson Les Paul Deluxe (built in 1972!)
Oh, almost forgot, i play on an Epiphone SG Limited edition blah blah, with humbuckers, and occasionally on a Gibson Les Paul Deluxe (built in 1972!)
Everyone does that to some degree or another.
I think the problem you're having has to do with overall volume. You really have to turn older amps way up to get heavy metal distortion, which is a combination of preamp, power tube and speaker distortion. This is fine for stage, but not so much fun for homes, unless you really hate your neighbors and like ringing ears.
You also bring up an important point - the AX84 lead preamp should put out some serious lead tones with gain 1 and 2 turned up.
Have you asked on the AX84 forum?
Also, have you compared your preamp voltages with those on the schematic?
Higher B+ would decrease the distortion.
I think the problem you're having has to do with overall volume. You really have to turn older amps way up to get heavy metal distortion, which is a combination of preamp, power tube and speaker distortion. This is fine for stage, but not so much fun for homes, unless you really hate your neighbors and like ringing ears.
You also bring up an important point - the AX84 lead preamp should put out some serious lead tones with gain 1 and 2 turned up.
Have you asked on the AX84 forum?
Also, have you compared your preamp voltages with those on the schematic?
Higher B+ would decrease the distortion.
Don't ask why, but the neighbors are fine with the jammin
The PSU is a bit different from the schematic... The first two caps are 200μF/450V each, and the other ones are 47μF. So, the first two voltages are about 390 and 375V. The rest are very close to the original design. Oh, and as i said there is no choke. Should i reconsider about that last one?
The PSU is a bit different from the schematic... The first two caps are 200μF/450V each, and the other ones are 47μF. So, the first two voltages are about 390 and 375V. The rest are very close to the original design. Oh, and as i said there is no choke. Should i reconsider about that last one?
I am not fond of Mesa at all.
Begin with an OS power-amp. Add rectifier tube, choke, cathode-bias and use lower cap values in the B+ section. This makes the amp sound less stiff and you will have something to begin with. A good forgiving power-amp is a good start.
I am not the person to listen to if you are after hi-tech stuff. But you must begin where all the others started to get your own sound, either it is hi-gain or OS.
My amps(www.myspace.com/eflatjumptessandersson) are built using technique from before Fender BF.
But..... most of your guitar-sound is in your fingers, not the amp or guitar!
Begin with an OS power-amp. Add rectifier tube, choke, cathode-bias and use lower cap values in the B+ section. This makes the amp sound less stiff and you will have something to begin with. A good forgiving power-amp is a good start.
I am not the person to listen to if you are after hi-tech stuff. But you must begin where all the others started to get your own sound, either it is hi-gain or OS.
My amps(www.myspace.com/eflatjumptessandersson) are built using technique from before Fender BF.
But..... most of your guitar-sound is in your fingers, not the amp or guitar!
I agree with revintage -- 200µF is WAY too much for a PS cap, and 47µ too.
My Matchless-based amp has three 30µF caps and no choke.
On 10, it pretty much nails vintage Marshall sounds (i.e. Living After Midnight, etc)
ThSpeakerDude88 also has good points -- vintage Marshall players use pedals to push the amp into metal territory. I use a Subdecay Blackstar.
I've found that the best way to describe things is what famous groups and players they sound like. For instance, like you, I built my first amp without knowing what it would sound like. It turned out to be a blues machine. I spent tons of time reading articles on the internet and asking questions on forums. The best, however, was finding that the amp was basically a Matchless Spitfire with an AC-15 bright switch, except one cap in the tone stack was different. I changed that cap from .01 to .1 and voila ... blues became heavy metal!
The difficult part is your amp is completely different, so our suggestions are vague and may not apply, especially since we can't really hear your amp. Also, tube amps respond to players ... some people really know exactly what to do to get serious tone from whatever they play. They pull out killer sounds ... grunge/punk from cheap amps, blues from vintage gear, metal from high gain.
My Matchless-based amp has three 30µF caps and no choke.
On 10, it pretty much nails vintage Marshall sounds (i.e. Living After Midnight, etc)
ThSpeakerDude88 also has good points -- vintage Marshall players use pedals to push the amp into metal territory. I use a Subdecay Blackstar.
I've found that the best way to describe things is what famous groups and players they sound like. For instance, like you, I built my first amp without knowing what it would sound like. It turned out to be a blues machine. I spent tons of time reading articles on the internet and asking questions on forums. The best, however, was finding that the amp was basically a Matchless Spitfire with an AC-15 bright switch, except one cap in the tone stack was different. I changed that cap from .01 to .1 and voila ... blues became heavy metal!
The difficult part is your amp is completely different, so our suggestions are vague and may not apply, especially since we can't really hear your amp. Also, tube amps respond to players ... some people really know exactly what to do to get serious tone from whatever they play. They pull out killer sounds ... grunge/punk from cheap amps, blues from vintage gear, metal from high gain.
@PRNDL
They are actually two of those chassis mounted 100+100μF electrolytics. You thnink i should lower them to 100μF each, for start? I've recorded some samples, but i don't have them here with me.
Anyway, i think i'll try the part of the schematic that aletheian posted, on ptp. Should be easy, i already have all the components. I'll keep the thread posted!
They are actually two of those chassis mounted 100+100μF electrolytics. You thnink i should lower them to 100μF each, for start? I've recorded some samples, but i don't have them here with me.
Anyway, i think i'll try the part of the schematic that aletheian posted, on ptp. Should be easy, i already have all the components. I'll keep the thread posted!
Lowering the electrolytics allows the amp to react to how hard you play ... this is described as the amp "breathing" or being "alive". A good guitar player can "push" a tube amp into singing leads.
HiFi amps want "stiff" power amps, which means chokes and higher value electrolytics.
I would recommend experimenting ... drop the caps to 100µ and see how it sounds, then bypass the choke and test again. If it sounds better, you could order appropriate caps (20µ or so).
HiFi amps want "stiff" power amps, which means chokes and higher value electrolytics.
I would recommend experimenting ... drop the caps to 100µ and see how it sounds, then bypass the choke and test again. If it sounds better, you could order appropriate caps (20µ or so).
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