I'm not a musician, but have several long-time friends who are. I'd like to build some small (<5 watt) practice amps to give as gifts. I've looked at many sites recently, but the more designs I see, the more I realize how little I know.
I've built and restored more than a few hi-fi amplifiers, but know nothing about guitar amps. I have no idea what 'crunch' or 'chime' refer to, nor what makes an amplifier 'bluesy' as opposed to 'metal'. All I know is that I have a basement workshop filled with parts, and the desire to build some really nice little amps that will be appreciated by guys who've played guitar for four decades.
I've looked at some of the projects on AX84, as well as numerous variations of Fender Champs and Princetons. I'm intrigued with Boozhound Labs' BHL-15. My goal is a little self-contained amp and speaker package in a small portable cabinet, which can be used in a residence without irritating the neighbors.
If any of you can recommend a simple all-tube design which fits this description, I'd appreciate your insights -- especially if you're a fifty-something serious amateur player, who still gets the urge to play some classic licks from John Mayall to Eric Clapton, or Duane Allman to Buddy Guy, at one o'clock in the morning.
I've built and restored more than a few hi-fi amplifiers, but know nothing about guitar amps. I have no idea what 'crunch' or 'chime' refer to, nor what makes an amplifier 'bluesy' as opposed to 'metal'. All I know is that I have a basement workshop filled with parts, and the desire to build some really nice little amps that will be appreciated by guys who've played guitar for four decades.
I've looked at some of the projects on AX84, as well as numerous variations of Fender Champs and Princetons. I'm intrigued with Boozhound Labs' BHL-15. My goal is a little self-contained amp and speaker package in a small portable cabinet, which can be used in a residence without irritating the neighbors.
If any of you can recommend a simple all-tube design which fits this description, I'd appreciate your insights -- especially if you're a fifty-something serious amateur player, who still gets the urge to play some classic licks from John Mayall to Eric Clapton, or Duane Allman to Buddy Guy, at one o'clock in the morning.
Crunch is how much distortion the sound has.
A guitar outputs a fairly mundane sine wave and doesnt sound good so musicians quickly found out that valve amps overdriven gave a much richer sound.
Before I could afford a valve amp I used a "soft limiter" that gave a similar distortion to a valve.
Nothing beats the sound of a valve amp being overdriven.
A guitar outputs a fairly mundane sine wave and doesnt sound good so musicians quickly found out that valve amps overdriven gave a much richer sound.
Before I could afford a valve amp I used a "soft limiter" that gave a similar distortion to a valve.
Nothing beats the sound of a valve amp being overdriven.
AX84
My first - and only - guitar amp project was an AX84 P1 (look it up under Classic Projects). It was meant for a classic/blues guitarist friend of mine. The guy plays mostly clean, with a mild crunch. He LOVES the sound.
Following his advise, I used a Jensen C12R speaker. Small speakers sound "tinny" he said. The result is a lively, chimey sound with "depth". Really sweet. Want some crunch? Up the volume a bit. I ended up replacing the pre valve with a 12AT7, cause the break up was a little too early for him. He LOVES the sound. Also with this thing you really hear differences when replacing valves. Sovtek=early dirt, ugly sound, Telefunken=too trebly, Ei,RFT=well balanced tone, Chinese=guano.
Generally, you need a decent box and a good 12' speaker, and you have a very sweet sounding thing that makes nice music. A cheap speaker will compromise the sound and in the end it won't be worth your effort. So, maybe it's not a cheap gift. It's a well thought out amp with its own special sound.
My first - and only - guitar amp project was an AX84 P1 (look it up under Classic Projects). It was meant for a classic/blues guitarist friend of mine. The guy plays mostly clean, with a mild crunch. He LOVES the sound.
Following his advise, I used a Jensen C12R speaker. Small speakers sound "tinny" he said. The result is a lively, chimey sound with "depth". Really sweet. Want some crunch? Up the volume a bit. I ended up replacing the pre valve with a 12AT7, cause the break up was a little too early for him. He LOVES the sound. Also with this thing you really hear differences when replacing valves. Sovtek=early dirt, ugly sound, Telefunken=too trebly, Ei,RFT=well balanced tone, Chinese=guano.
Generally, you need a decent box and a good 12' speaker, and you have a very sweet sounding thing that makes nice music. A cheap speaker will compromise the sound and in the end it won't be worth your effort. So, maybe it's not a cheap gift. It's a well thought out amp with its own special sound.
Oooh that looks sweeeeet.... I wonder how it would work with a GU50...
must.... resist....
I recently built a 5F1 copy and bought the transformers here:
Transformers for Tube Amps
Very reasonably priced and they sound just fine.
Transformers for Tube Amps
Very reasonably priced and they sound just fine.
This at least fits the not annoying the neighbors criteria: http://www.ecp.cc/mini_guitar_amp.html
Your neighbors may be happy but you won't. I'd rather play unplugged than hear my guitar through that speaker. The presence of that lovely Gibson adds insult to injury - she deserves better. The volume knob at 3 is OK for a Champ-like amp; you will be happy and the neighbors won't bang on the walls or call the police. I like pocket-sized amps though but only if they are cute:
JJS.at : Electronic Projects : Class A Subminiature Amp
freestompboxes.org • View topic - "Superfly" - submini tube version of Doug H's Firefly
People like to play these with 4X12 cabs. Oh the irony. Oh the contrast.
JJS.at : Electronic Projects : Class A Subminiature Amp
freestompboxes.org • View topic - "Superfly" - submini tube version of Doug H's Firefly
People like to play these with 4X12 cabs. Oh the irony. Oh the contrast.
Thanks to all for the suggestions and links. I'm going to work up a simple variant of a single-ended 6V6 amp. Instead of octals or nine-pin tubes, I'm going to use all compactrons.
A 5HC7 driving a 6HE5 is really nothing more than a 12AX7/12AU7/6V6 circuit, but the tubes are dirt cheap -- 10 or 12 bucks will buy a shoebox full of NOS compactrons. Lots of opportunity for tube-rolling.
The learning curve will come in trying different tone controls, and purposely undersizing the power supply. I've spent the last several years learning techniques for reducing distortion, now I have to learn how to cultivate it.
A 5HC7 driving a 6HE5 is really nothing more than a 12AX7/12AU7/6V6 circuit, but the tubes are dirt cheap -- 10 or 12 bucks will buy a shoebox full of NOS compactrons. Lots of opportunity for tube-rolling.
The learning curve will come in trying different tone controls, and purposely undersizing the power supply. I've spent the last several years learning techniques for reducing distortion, now I have to learn how to cultivate it.
I see some suggestions that don't look much like they'd meet your request that the amp put out less than 5 watts.
I also don't see anything that addresses the cost of the project.
For about what you might expect to pay for a single transformer for probably any (I didn't have time to read every reply) of the other suggested projects listed in this thread, you can buy an ENTIRE AMP KIT complete with transformers, tubes and all the necessary parts! And since you said that you were inexperienced, you won't have to sit there scratching your head to figure out what to do first and what to do next, since the kit comes with a very detailed step-by-step set of instructions with many, many photographs.
Here's what one customer said about the kit:
"Dear tubes_and_kits,
I do not want to beat it to death, but needed to tell you again how much I am liking this amp. I like it more and more. Perhaps I never had an amp I could turn up enough that it sounded good(while keeping the volume low enough). Though I have built others that just did not sound good.
I especially appreciate your good work after building a very similar kit. Yours wins in every category: quality of parts, completeness of parts, sound, volume, instructions, overall quality, fitandfinish. whatever.!" --M
And if you want to cultivate distortion, there is a complete explanation in the detailed instructions about how to modify the kit to change the threshold of distortion by swapping out the cathode resistor of the output stage. Oh, the tube? a 6EB7. Triode and Pentode in one bottle. One tube amp. Only one nine-pin socket needed. You can't build a guitar amp for less than this. Not no way. Not no how.
Only 69.95 COMPLETE! (Except for the speaker and the chassis)
Only 74.95 COMPLETE WITH SPEAKER! (If you build your own cabinet, all you need is a sheet of aluminum and some wire and tools.)
MTA-1E or MTA-1EX available on eBay.
Just search for Tube Amp Kit.
--tubekit
I also don't see anything that addresses the cost of the project.
For about what you might expect to pay for a single transformer for probably any (I didn't have time to read every reply) of the other suggested projects listed in this thread, you can buy an ENTIRE AMP KIT complete with transformers, tubes and all the necessary parts! And since you said that you were inexperienced, you won't have to sit there scratching your head to figure out what to do first and what to do next, since the kit comes with a very detailed step-by-step set of instructions with many, many photographs.
Here's what one customer said about the kit:
"Dear tubes_and_kits,
I do not want to beat it to death, but needed to tell you again how much I am liking this amp. I like it more and more. Perhaps I never had an amp I could turn up enough that it sounded good(while keeping the volume low enough). Though I have built others that just did not sound good.
I especially appreciate your good work after building a very similar kit. Yours wins in every category: quality of parts, completeness of parts, sound, volume, instructions, overall quality, fitandfinish. whatever.!" --M
And if you want to cultivate distortion, there is a complete explanation in the detailed instructions about how to modify the kit to change the threshold of distortion by swapping out the cathode resistor of the output stage. Oh, the tube? a 6EB7. Triode and Pentode in one bottle. One tube amp. Only one nine-pin socket needed. You can't build a guitar amp for less than this. Not no way. Not no how.
Only 69.95 COMPLETE! (Except for the speaker and the chassis)
Only 74.95 COMPLETE WITH SPEAKER! (If you build your own cabinet, all you need is a sheet of aluminum and some wire and tools.)
MTA-1E or MTA-1EX available on eBay.
Just search for Tube Amp Kit.
--tubekit
Every dog gets one bite. Every new member trying to sell something and using the non-commercial part of the forum to do so is given one warning not to do that. Don't do that or your posting privileges will be removed.
The driven pentode has a good bit of GM so I'm sure that with a hot guitar you might get to the edge of distortion, but to really scream you are going to need a stomp box. From the text he has posted so far it doesn't seem that the designer has even measured the power output, but he is sure that he can get 2.5 watts out of it.
If the intention is to make a single tube guitar amp worth using you almost have to use a compactron, either a 3 section tube, or a dual pentode. At least there will be enough gain so that the user can get some expression out of the guitar.
I think that it would be possible to build a real useful guitar amp for $69.99 not counting the cabinet or speaker. The real question is which way do I go. Either way it will have at least 2 tubes.
I looked at the description of the amp described in the auction listing. I am underwhelmed.
No chassis, no speaker, no cabinet. A spud amp with no possibility of changing driver tubes to experiment with gain. Three transformers -- therefore probably using two wired front-to-back to yield the B+, and one for an OPT. With shipping, this meager handful of parts comes to about eighty bucks. By the time it's on a board and in a box, with wiring, solder, and power cord, at least a hundred.
I'll take your challenge that a better amp cannot be built for less. And I'll sweeten the pot for anyone else who cares to join in. Here's my offer:
Design and assemble a tube low-power guitar amp (2.5 - 5 watts) for $100 or less. No speaker or cabinet, but a complete amplifier which can be plugged into the wall and produce a suitable output from a guitar plugged into its input jack.
Save your receipts. Parts can be from any source, or adapted from any other purpose, as long as they're available to the general public (e.g surplus vendors for transformers, discount store metal pan/box for chassis).
First person to submit pictures of a safe, working design, and a sound clip of the amp being played through, gets reimbursed for the total cost of the parts. In addition, I'll donate another $250 to diyaudio.com to help support this most excellent forum.
Have at it, gentlemen (and ladies).
No chassis, no speaker, no cabinet. A spud amp with no possibility of changing driver tubes to experiment with gain. Three transformers -- therefore probably using two wired front-to-back to yield the B+, and one for an OPT. With shipping, this meager handful of parts comes to about eighty bucks. By the time it's on a board and in a box, with wiring, solder, and power cord, at least a hundred.
I'll take your challenge that a better amp cannot be built for less. And I'll sweeten the pot for anyone else who cares to join in. Here's my offer:
Design and assemble a tube low-power guitar amp (2.5 - 5 watts) for $100 or less. No speaker or cabinet, but a complete amplifier which can be plugged into the wall and produce a suitable output from a guitar plugged into its input jack.
Save your receipts. Parts can be from any source, or adapted from any other purpose, as long as they're available to the general public (e.g surplus vendors for transformers, discount store metal pan/box for chassis).
First person to submit pictures of a safe, working design, and a sound clip of the amp being played through, gets reimbursed for the total cost of the parts. In addition, I'll donate another $250 to diyaudio.com to help support this most excellent forum.
Have at it, gentlemen (and ladies).
Pentode input and a 6AQ5 is a GOOD IDEA.
This sounds like fun but the winner must not be the quickest but the one with the cheapest and best SOUNDING project. IMO it has to sound as good or better than a Fender Champ otherwise it will be too easy. We probably will need a poll to judge which one sounds best even though too many variables come into play (guitars, speakers, recording gear...). Hmm.... maybe not so good idea after all. IMO 100$ is an easy target. Too easy. Not motivated enough, make it more challenging.
I posted this in another thread about low powered guitar amps. I built the 6AQ5 / 6AU6 amp several years ago. It is a valid contender and there are dozens of tube choices. In fact if if you wire the sockets right the 6AQ5 and the 6AU6 become pin compatible! I happen to have about 500 of each tube too.
The N-68X is good for 50VA and costs $11.20 at Mouser. You can use it as an isolation transformer and run an entire guitar amp heaters and all on the secondary. I have used them when restoring the old series string "shock box" guitar amps from the 1950's that used 50C5, 35W4, and 12AX7 or 12AU6 tubes.
You could run the secondary into a voltage doubler or you could just turn the transformer around wire the primary (now the secondary) for 230 volts and run it into a bridge (you still get 50 VA). I would tend toward the bridge and that is what I have used in the past with the N-68X. There are several 6.3 volt transformers available for under $10.
There are likely as many opinions on the circuit choice as there are circuits. My choice would take 2 tubes. Either a 12AX7 feeding a 6AQ5 or a 6AU6 feeding a 6AQ5 both derived from the appropriate Fender Champ schematic.
I would add that the purpose of this exercise is to provide the diyAudio members with a wealth of new choices in low cost guitar amp designs. Therefore the parts need to be available to the general public as stated, but one off Ebay trades should be prohibited as should be other parts that are only available for limited time (surplus or scrap). The price quoted should be for a realistic quantity.
I have dozens of transformers that I got free or cheap. These should not be allowed. I can build a 100 watt amp using OPT's that I got for $16 each and I have the receipt. I bought 200 of them.
Many of our members are scattered all over the globe. Consideration should be given for designs that can be built in Europe or Australia (tube and transformer availability).
I agree, even though I can have you pictures of a 6AU6 / 6AQ5 perf board amp as soon as I can find it. Pick a deadline say 2 or 3 months out and let everyone submit pictures, parts lists with sources, schematics, and a Youtube link to it working. Guitar playing skills (or lack thereof) should not count, but the features of the amp need to be seen and heard.
The amp should play clean at a reasonable power level and should get nasty when cranked. The $100 limit will impose reasonable limitations on power output, Do we need to impose a minimum. SE or P-P designs should be OK.
Not really. I imagine anyone wanting to build a real useful amp would be willing to spend $100. The skill comes from making the best $100 amp that can be copied by an average builder.
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