I am looking to put together a guitar amp as I sold my last one off (which was a big 100W thing that I never really liked) a while back and now I need one again. I am looking, I think, for low watts, probably single ended, and would like more of a vintage sound, but also the ability to overdrive a bit.
To this end, I am thinking of starting with the 5F2 at Angela.com, but maybe making some mods to this as I'd like to build it with stuff i have around, and I am an audiophile, so I feel like the PS needs some more filtering. But, since I m totally green w/r/t/ what a guitar amp needs, I could use some friendly suggestions.
First, here's the schematic.
The project can be found at http://www.angela.com/
For the output iron, I have some edcor 10K:8 transformers that I'll start with. Angela recommends the Fender iron, so I may try that as well. I am also thinking about using a 300b as the output tube as I have them, but if this is a bad idea then I won't.
Aside from those things, I have a few other questions. The first is, could anyone explain what goes on between the two sides of the 12ax7? I take it it is a tone control and a volume control, but I don't really understand the circuit. Also, (and I know this is a dangerous thing to ask) is there a better tube to use than the 12ax7? i do have them, so it is good for that, but if something else is better then I am happy to experiment.
Second, what is the connection from the transformer's secondary to the 12ax7's cathode?
Third, how would I add reverb to the amp?
Oh, and last, any speaker suggestions? Cheap and easy to find would be the criteria -- nothing vintage unless you have a source.
Thanks,
-d
To this end, I am thinking of starting with the 5F2 at Angela.com, but maybe making some mods to this as I'd like to build it with stuff i have around, and I am an audiophile, so I feel like the PS needs some more filtering. But, since I m totally green w/r/t/ what a guitar amp needs, I could use some friendly suggestions.
First, here's the schematic.
An externally hosted image should be here but it was not working when we last tested it.
The project can be found at http://www.angela.com/
For the output iron, I have some edcor 10K:8 transformers that I'll start with. Angela recommends the Fender iron, so I may try that as well. I am also thinking about using a 300b as the output tube as I have them, but if this is a bad idea then I won't.
Aside from those things, I have a few other questions. The first is, could anyone explain what goes on between the two sides of the 12ax7? I take it it is a tone control and a volume control, but I don't really understand the circuit. Also, (and I know this is a dangerous thing to ask) is there a better tube to use than the 12ax7? i do have them, so it is good for that, but if something else is better then I am happy to experiment.
Second, what is the connection from the transformer's secondary to the 12ax7's cathode?
Third, how would I add reverb to the amp?
Oh, and last, any speaker suggestions? Cheap and easy to find would be the criteria -- nothing vintage unless you have a source.
Thanks,
-d
dsavitsk said:
The whole point of the 'valve sound' is that the power supply is crappy, and it 'sags' under load, introducing lots of distortion and colouration.
The 1meg is the volume control, the 250K is a crude tone control, remember quality isn't an issue here - cheap and nasty is what people want!.
They plug in, and generally double triodes all have the same connections - so you can try different ones.
It's negative feedback.
The usual way is to use opamps to drive the reverb (no point using valves) - but reverb will probably be more complex than the entire existing circuit.
There are plenty of 1x12's intended for guitar - from that it's just a question of picking one you like the sound of, it's a VERY subjective choose - not a question of 'quality', but of 'the sound'.
Hi all,
I share nigel ideas on almost any points.
For the speaker I recently tried the new Eminence series (blue & red).
and found them good for guitar use. And they come at a very fair price. They are available in many sizes & Z & responses.
PS: sure, a tube/spring reverb is almost the same effort as the whole amp.
I share nigel ideas on almost any points.
For the speaker I recently tried the new Eminence series (blue & red).
and found them good for guitar use. And they come at a very fair price. They are available in many sizes & Z & responses.
PS: sure, a tube/spring reverb is almost the same effort as the whole amp.
Re: Re: First Guitar Amp Help
Thanks for the link, that's quite helpful.
Sags is fine, but that is different from ripple isn't it? I was just thinking of throwing an extra pi filter in to try to kep the hum to a minimum, but I won't if that's a bad thing to do. Actually, I'll probably try both and see what happens unless this is just a terrible idea.
It looks like reverb will have to wait.
So, I think I am going to add a second pot between the 12ax7 and the output tube and otherwise leave it pretty much as is and tweak once I have something that makes noise. I never found having lots of tone controls particularly useful, so I think I'll try with just the one as I like the minimalist design. But as a last thought, anyone see any reason to use, or not to use, a 300b on the output?
aletheian said:
Thanks for the link, that's quite helpful.
Nigel Goodwin said:
Sags is fine, but that is different from ripple isn't it? I was just thinking of throwing an extra pi filter in to try to kep the hum to a minimum, but I won't if that's a bad thing to do. Actually, I'll probably try both and see what happens unless this is just a terrible idea.
By different tubes, i meant hidden things that manufacturers don't use. So, in hifi, something like subbing in a 12sn7 or 7n7 instead of the ubiquitous 6sn7 to get higher quality while saving a few bucks. It looks like the 5751 is one option here, but I am just looking for others. Also, how about using an octal?
It looks like reverb will have to wait.
So, I think I am going to add a second pot between the 12ax7 and the output tube and otherwise leave it pretty much as is and tweak once I have something that makes noise. I never found having lots of tone controls particularly useful, so I think I'll try with just the one as I like the minimalist design. But as a last thought, anyone see any reason to use, or not to use, a 300b on the output?
A single ended (or any class A) amp won't sag with the signal since it's already drawing max current at idle. I would increase the PS caps to 15 or 20 microF. You'll get less hum.
I really like this type of tone control on small amps. It's very interactive with the volume control. You can eliminate or reduce the feedback for a more lively response. I've used your master volume idea and it definitely gives you more tonal options. Experiment with bypassing the cathode resistor in all three stages. You might like something small in the first stage to control the voicing of the amp.
With that OPT either a 6V6 or EL84 would be good choices. A 6L6, EL34 or 6550 into a 4 ohm load would work well, but you would want a more current from your power supply. I'm too cheap to know anything first hand about the 300B.
Have fun!
Fred
I like this circuit, have built it a couple of times with various mods.
The first section of 12AX7 is pure gain stage- remember the guitar output is very low level. This is where you should use shielded cables, DC filament and site the 12AX7, input sockets etc far away from the power and output transformer and connections. You don't want hum in this stage! Also star grounding.
12AX7 is great for this, nice tone, quiet, loads of gain. You *could* use 6SL7 but it doesn't have as much gain and may be noisier. you could try EF86 if you were really keen! SN7 would not have enough, you would need two of them or more to get the necessary amplification.
The tone and volume stages simply "bleed off" the signal to ground. The second 12AX7 stage is the output tube driver stage. You could use 1/2 a 6SN7 here if you really needed to.
You can use a 500K pot for the volume and tone pots, no probs. A mod to consider is using a 6L6 or even better, EL34 instead of a 6V6- you need more voltage and bigger transformers but the amp will give a fair bit more power. You could use a 300B but it would give the same power as the 6V6 (triodes are less efficient)
Reverb- use a pedal
or buy a reverb tank and build another fender amp with a reverb driver (usually 12AT7??)
BTW if you put a 4 Ohm guitar speaker on that transformer, it presents a 5K impedance to the output tube. So you have some options there. For speakers just use any old thing- 95dB efficient or above- an old speaker out of an organ or even a tube radio would work ok for starters.
The first section of 12AX7 is pure gain stage- remember the guitar output is very low level. This is where you should use shielded cables, DC filament and site the 12AX7, input sockets etc far away from the power and output transformer and connections. You don't want hum in this stage! Also star grounding.
12AX7 is great for this, nice tone, quiet, loads of gain. You *could* use 6SL7 but it doesn't have as much gain and may be noisier. you could try EF86 if you were really keen! SN7 would not have enough, you would need two of them or more to get the necessary amplification.
The tone and volume stages simply "bleed off" the signal to ground. The second 12AX7 stage is the output tube driver stage. You could use 1/2 a 6SN7 here if you really needed to.
You can use a 500K pot for the volume and tone pots, no probs. A mod to consider is using a 6L6 or even better, EL34 instead of a 6V6- you need more voltage and bigger transformers but the amp will give a fair bit more power. You could use a 300B but it would give the same power as the 6V6 (triodes are less efficient)
Reverb- use a pedal
or buy a reverb tank and build another fender amp with a reverb driver (usually 12AT7??)BTW if you put a 4 Ohm guitar speaker on that transformer, it presents a 5K impedance to the output tube. So you have some options there. For speakers just use any old thing- 95dB efficient or above- an old speaker out of an organ or even a tube radio would work ok for starters.
Most guitar players want the ability to crank it to eleven. The 12AX7 has the most gain of all of the common 12**7 tubes. Any guitar amp built commercially must use tubes that are available to musicians at a music store. That limits the designer to about 10 different tubes. A DIY guitar amp doesn't have this limitation, although it must be considered if you ever want to sell the amp. I have tried other tubes in the input stages (TV tuner tubes, pentodes) but I have always returned to the 12AX7 (or its variants like the 5751). You can always plug in the other 12A*7 tubes, for less gain and then drive the snot out of the amp with a distortion pedal for a unique sound.
The above statement is technically correct, but as soon as the amp is driven into hard clip it is no longer a class A amp and the current goes all over the place. The power supply in a guitar amp has a lot to do with the sound. A zillion microfarads of filtering will give the amp a more solid sound (some call it sterile) while raising the output power. Small filter caps allow the B+ voltage to "sag" as the amp is overdriven causing the total amp gain to drop. As the note dies out the amp comes out of clip allowing the B+ to rise. The amp gain slowly rises causing the note to have a longer "sustain". A good guitar player can modulate this effect with the volume knob on the guitar or a volume pedal. All of this is a matter of personal taste, so don't be afraid to experiment. The hum is less of a problem on amps using a small speaker.
I tried a 300B based guitar amp, and I wasn't too happy with the sound. I used one of my TubelabSE amps with a guitar preamp. It did the clean sounds great, but I couldn't get it to sound right with heavy overdrive. I may have been able to if I experimented further, but I gave up early on.
Most guitar amps are pentode wired for two reasons. It gives the most power per dollar (important if you are a manufacturer) and it has a lot of inherent distortion which allows for a lot of flexibility for feedback based tone controls (the "Presense" control on a Marshall amp). I put a triode - pentode - UL (if available) switch on my amps for flexibility, but triode is mostly used by acoustic players).
I have used Edcor iron in a guitar amp, and it sounded great. It has a UL tap which is good for a loud clean sound. For my small amps I prefer the Hammond 125CSE, because it has 4 different impedance taps. I put a switch here to allow intentional load mismatching for tonal flexibility. Do not operate the output tube at or above its maximum voltage rating with a high (10k) load impedance. I have summons up the fire gods this way. It sounded cool right before it blew up though! Fender always used undersized iron. This cuts hum (and allows the 8uF caps) and is partly responsible for the Fender sound (transformer saturation).
My favorite output tubes for guitar amp are 6L6 and EL84 for small amps (bluesy tone) and 6L6 or EL34 for most amps (rock, blues and metal). For the crank it to eleven crowd I use a KT88 or 6550. I have used sweep tubes in some of my own amps (150 watt P-P), but a gigging musician wants an amp that can be fixed on the road.
A few years ago I built a few very flexible amps based on the Fender Champ. The schematic can be found here:
http://www.tubelab.com/Turbo_Champ.htm
Many of the amps that I built (probably all of them) were modified from that schematic. Most of the modifications were capacitor value changes. I had to replace the screen and cathode resistors on at least one amp. Use 3 or 5 watt resistors for these parts. The cathode cap should be at least 50 volts for 6L6 and bigger tubes.
Note the .047 cap on the grid of the output tube. Resist the temptation to put a bigger cap here. This can lead to blocking distortion (known as farting out to a guitar player) and an unstable amp.
The above statement is technically correct, but as soon as the amp is driven into hard clip it is no longer a class A amp and the current goes all over the place. The power supply in a guitar amp has a lot to do with the sound. A zillion microfarads of filtering will give the amp a more solid sound (some call it sterile) while raising the output power. Small filter caps allow the B+ voltage to "sag" as the amp is overdriven causing the total amp gain to drop. As the note dies out the amp comes out of clip allowing the B+ to rise. The amp gain slowly rises causing the note to have a longer "sustain". A good guitar player can modulate this effect with the volume knob on the guitar or a volume pedal. All of this is a matter of personal taste, so don't be afraid to experiment. The hum is less of a problem on amps using a small speaker.
I tried a 300B based guitar amp, and I wasn't too happy with the sound. I used one of my TubelabSE amps with a guitar preamp. It did the clean sounds great, but I couldn't get it to sound right with heavy overdrive. I may have been able to if I experimented further, but I gave up early on.
Most guitar amps are pentode wired for two reasons. It gives the most power per dollar (important if you are a manufacturer) and it has a lot of inherent distortion which allows for a lot of flexibility for feedback based tone controls (the "Presense" control on a Marshall amp). I put a triode - pentode - UL (if available) switch on my amps for flexibility, but triode is mostly used by acoustic players).
I have used Edcor iron in a guitar amp, and it sounded great. It has a UL tap which is good for a loud clean sound. For my small amps I prefer the Hammond 125CSE, because it has 4 different impedance taps. I put a switch here to allow intentional load mismatching for tonal flexibility. Do not operate the output tube at or above its maximum voltage rating with a high (10k) load impedance. I have summons up the fire gods this way. It sounded cool right before it blew up though! Fender always used undersized iron. This cuts hum (and allows the 8uF caps) and is partly responsible for the Fender sound (transformer saturation).
My favorite output tubes for guitar amp are 6L6 and EL84 for small amps (bluesy tone) and 6L6 or EL34 for most amps (rock, blues and metal). For the crank it to eleven crowd I use a KT88 or 6550. I have used sweep tubes in some of my own amps (150 watt P-P), but a gigging musician wants an amp that can be fixed on the road.
A few years ago I built a few very flexible amps based on the Fender Champ. The schematic can be found here:
http://www.tubelab.com/Turbo_Champ.htm
Many of the amps that I built (probably all of them) were modified from that schematic. Most of the modifications were capacitor value changes. I had to replace the screen and cathode resistors on at least one amp. Use 3 or 5 watt resistors for these parts. The cathode cap should be at least 50 volts for 6L6 and bigger tubes.
Note the .047 cap on the grid of the output tube. Resist the temptation to put a bigger cap here. This can lead to blocking distortion (known as farting out to a guitar player) and an unstable amp.
The original Champ sounds great but when the volume is at maximum the hum noise is probably too much for an audiophile
Guitar players usually don't mind.
Maybe this is the right one for you:
http://www.diycustomamps.com/rem_champ.htm
Guitar players usually don't mind.
Maybe this is the right one for you:
http://www.diycustomamps.com/rem_champ.htm
you can't go wrong with this one.
classic leo, at least partially cribbed from the old tube manuals.
what you can expect is a great low volume practice and world-class recording amp if you use the right stuff in it.
my $.02
do yourself a favor and buy carbon comp resistors from mouser, at least for the high voltage plate loads. don't go above 20mf each for the PS caps and use low-end electrolytics.
the noisiest link in the guitar system is always the guitar/cable anyway
if you like higher gain, bypass the 12ax7 cathode resistors w/ 25mf electrolytics...or reduce that value to roll off low end and make it appear brighter...
thoses eminence speakers are quite good and not expensive. i have tried them all and found a few that are great for specific sounds...theere is quite a range of choices. too many actually.
what size speaker are you going with?
classic leo, at least partially cribbed from the old tube manuals.
what you can expect is a great low volume practice and world-class recording amp if you use the right stuff in it.
my $.02
do yourself a favor and buy carbon comp resistors from mouser, at least for the high voltage plate loads. don't go above 20mf each for the PS caps and use low-end electrolytics.
the noisiest link in the guitar system is always the guitar/cable anyway
if you like higher gain, bypass the 12ax7 cathode resistors w/ 25mf electrolytics...or reduce that value to roll off low end and make it appear brighter...
thoses eminence speakers are quite good and not expensive. i have tried them all and found a few that are great for specific sounds...theere is quite a range of choices. too many actually.
what size speaker are you going with?
pretty much everything has been tried. active, balanced, lo-z, you name it.
once, when i was messing with cable to try to reduce the cable/volume control interactions, i ended up building a mosfet buffer and mounted it in the guitar.
it sounded sterile. too much bandwidth.
in the end, the old classic circuits and components are the building blocks of the sound of amplified guitar, as we know and like it.
even cables that are "too good" distress some musicians. we are used to the rolled off, noisy sound of hi-z unbalanced with a 20 foot cable.
i still prefer good cable and fidelity, but not active circuits. they sound "wrong" to me, and most players, hence the popularity of vintage amps and amp repros...
once, when i was messing with cable to try to reduce the cable/volume control interactions, i ended up building a mosfet buffer and mounted it in the guitar.
it sounded sterile. too much bandwidth.
in the end, the old classic circuits and components are the building blocks of the sound of amplified guitar, as we know and like it.
even cables that are "too good" distress some musicians. we are used to the rolled off, noisy sound of hi-z unbalanced with a 20 foot cable.
i still prefer good cable and fidelity, but not active circuits. they sound "wrong" to me, and most players, hence the popularity of vintage amps and amp repros...
Same answer. There are acoustic guitars with a preamp onboard, and even a 3 band EQ. The most frustrating thing about these is having your battery die in the middle of a performance.
There were a few amplified electric guitars arround in the 1970's but they didn't catch on. I have seen amplified electronics kits for the Stratocaster, but I have never tried one. I know of one performer who mounted a Rocktron (belt mounted effects preamp) in his guitar.
I built an electric guitar with a preamp and a fuzz box in it back in the 70's. It worked pretty good, but it is no longer alive (too much abuse). I am contemplating a modernized version though.
There were a few amplified electric guitars arround in the 1970's but they didn't catch on. I have seen amplified electronics kits for the Stratocaster, but I have never tried one. I know of one performer who mounted a Rocktron (belt mounted effects preamp) in his guitar.
I built an electric guitar with a preamp and a fuzz box in it back in the 70's. It worked pretty good, but it is no longer alive (too much abuse). I am contemplating a modernized version though.
my mosfet thingie was straight-up follower, no gain, just simple buffer and very low drain. i remember at the time i calculated the drain time on a 9 volt battery, for the # of hours i played, was basically longer than the battery shelf life. dead batteries are a bummer
it worked great. the guitar basically ignored cable issues and sounded the same at all volume settings, rather than rolled-off in the treble at lower settings as you would expect. only problem - too aggressively bright
that was a fun minute. i tried every cable available at the time, including some mhz bandwidth video stuff.
nice antenna!
finally settled on canare gs-6. wide, but not too wide
it worked great. the guitar basically ignored cable issues and sounded the same at all volume settings, rather than rolled-off in the treble at lower settings as you would expect. only problem - too aggressively bright
that was a fun minute. i tried every cable available at the time, including some mhz bandwidth video stuff.
nice antenna!
finally settled on canare gs-6. wide, but not too wide
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