To answer my own question: http://www.diyaudio.com/forums/tubes-valves/152600-black-6v6gt-originals.html#post1935611
The black coating in the 6V6s may be to prevent electrostatic charge buildup on the glass surface. Maybe for quieter operation?
I think there are a few of us here who are just building a small amp of whatever size for fun with cheapest one of a kind parts. My OT supplier doubled the price on the xfmrs after I bought mine besides. I'm more interested in trying some harmonic effects with a beam deflection tube multiplier or two for the amp. Who says the amp has to distort the same way they traditionally do. With two squarer circuits I should be able to generate 2nd and 4th harmonics to get string like sounds. Also looking at more like 20 Watts with some small sweep tubes.
I think there are a few of us here who are just building a small amp of whatever size for fun with cheapest one of a kind parts. My OT supplier doubled the price on the xfmrs after I bought mine besides. I'm more interested in trying some harmonic effects with a beam deflection tube multiplier or two for the amp. Who says the amp has to distort the same way they traditionally do. With two squarer circuits I should be able to generate 2nd and 4th harmonics to get string like sounds. Also looking at more like 20 Watts with some small sweep tubes.
As I said I don't play. Actually, I took lessons at too young of an age but did learn the basics. I don't really have any interest in playing, what I enjoy is the design aspect. OK, I'll probably want to learn something to play just to test out the amp - that's fine. My son will do the more advanced testing.
It is not often worth scratch building to save money. I expect that people will do it for the learning experience or the ability to customize it as they want.
Last edited:
Great point
I would have much rather seen an innovative design contest instead of a cost point amp.
Since nobody is putting a price tag on labor(which would put all entries over budget) the idea of just grabbing one of the $99.99 specials at the gear outlets makes the most sense.
The guitar amp market is a funny place, I could see the guys here like tubelab coming up with a great design & maybe a DIY PCB amp, but really, PCB amps are pretty much less than desirable in the grand scheme of things.
Maybe I have been hanging out to long on the gear forums reading some/most of the info on boutique and custom amps.
I can recall several PCB based DIY amps that came and went, one in particular was extremely well done 18W Marshall type amp.
Beautiful boards, excellent documentation yada yada.
The gear snobs tore it up just for being PCB.
YMMV
My amp keeps coming out 8+ bucks over budget, I am getting bored trying to beat the $100.00 mark because I know the sound I prefer and 110.00 gets me there
It is fairly obvious that you cannot beat mass production made in China as far as price goes for much of anything - period. It is absurd to consider labor, obviously you have to do this for the enjoyment.
In case anyone hasn't noticed all of the specialty guitar amp shops charge more than even the authorized distributors for many parts such as resistors, caps, knobs, etc. I'm specing Allied power transformers, but resistors, caps and knobs were also cheaper there, sometimes cheaper than the surplus houses, LOL!
In case anyone hasn't noticed all of the specialty guitar amp shops charge more than even the authorized distributors for many parts such as resistors, caps, knobs, etc. I'm specing Allied power transformers, but resistors, caps and knobs were also cheaper there, sometimes cheaper than the surplus houses, LOL!
Last edited:
I had a desire to do something like this amp to give some local guys a small amp for home use. One guy I know has an old line powered amp that he wanted to recap and fix up along with add a transformer for isolation. I thought it almost not worth while as you could build a better one for little more than the same cost.
I did not have a dollar figure in mind but thought $50 would be reasonable given some recycled parts such as computer line cord, power switch, 12V wall wart, and the like. I did want to use common tubes so that they would have no trouble getting replacements. While not as low buck as could be I settled on a 12AX7 and 12AQ6's. I would have gone for a PI and wanted to use a MOSFET, but in the spirit of this thread I dropped the stage to keep in around the $100 mark. Not sure if I can do it though but it would not bother me to come up with something I am satisfied with that cost $125.
As of now I am more or less satisfied I have something worth building and hopefully one day someone will look at my amp and decide to make one similar. To me that would be winning. I am just as interested in seeing how others would go about skinning this cat. And hopefully after all is said and done we can revisit what we done and maybe attempt some add-on's. Some extra features cost very little once you have the basic amp running (effects loop, headphone out, maybe even foldback reverb).
Most of all I am doing this is to challenge myself.
I did not have a dollar figure in mind but thought $50 would be reasonable given some recycled parts such as computer line cord, power switch, 12V wall wart, and the like. I did want to use common tubes so that they would have no trouble getting replacements. While not as low buck as could be I settled on a 12AX7 and 12AQ6's. I would have gone for a PI and wanted to use a MOSFET, but in the spirit of this thread I dropped the stage to keep in around the $100 mark. Not sure if I can do it though but it would not bother me to come up with something I am satisfied with that cost $125.
As of now I am more or less satisfied I have something worth building and hopefully one day someone will look at my amp and decide to make one similar. To me that would be winning. I am just as interested in seeing how others would go about skinning this cat. And hopefully after all is said and done we can revisit what we done and maybe attempt some add-on's. Some extra features cost very little once you have the basic amp running (effects loop, headphone out, maybe even foldback reverb).
Most of all I am doing this is to challenge myself.
And some of the HiFi amp guys aren't anti PCB? When I started Tubelab 6 years ago I got more hate mail than positve input for using PC boards and poluting tube "purity" with mosfets. A funny thing happened. A few people built my amps because they were easier than PTP wiring. Then they discovered that they sounded good. Then......
There will always be tube purists that shun PC boards and sand state assistance, so be it. As with my other projects I will post the schematic and parts list on my web site and anyone is welcome to PTP it if they want. Just don't cry to me if it hums. I like PCB designs because they are repeatable. Once the PCB is done right it can be built over and over again and they will all sound the same. The proto however is made on perf board. But the purists don't like that either, but turret boards are OK, go figure.
I can say that a $100 price point for a guitar amp is easy. A good sounding guitar amp is easy. A good sounding amp for $100 in parts that is so easy to build that "even a drummer could do it" IS a challenge.
I dug out all my books and spent dozens of hours scouring the web. It seems that a lot of my weird ideas have been done before. I found some really oddball tubes that would allow building a Champ like design WITH a tube rectifier for under $60 in parts. While digging through an old guitar amp book, there it was, made by Magnatone in the early 60's. One of the tubes turns out to be quite rare so that idea got trashed. Is it possible to do a Marshall 18 watt like design for $100? I haven't found THAT in any books or web sites yet.
Yeah, I was looking for an answer there too. I am going forward assuming that the large surplus houses that list parts in a printed catalog and have 1000+ of that item in stock are OK.
I think the numbers "2 to 5 watts" were stated somewhere, but I don't know who stated those numbers. The original poster (and the person who put down his money to start this challenge) wanted a small practice amp. OK, I look at it this way, if the amp puts out say 18 watts, but has a built in attenuator to drop the power to 2 watts, then it is still a "2 watt practice amp" with more versatillity. When you start pricing each stage in your amp the output stage comes in at about $25 regardless of the power level. Most of the cost is in the OPT. The only limitation on output power comes from the transformers.
I think that's what the OP started here. We will see several designs that hit the $100 price point. There will be a few that miss the $100 mark but I (and others I'm sure) would like to see them all posted. We will get to see a few unique designs, and a few unique takes on how to do a modern version of a classic design with a target price in mind. If a builder down the road a while decides to take bits and pieces from several designs, and make his own amp, then the information is there.
I am looking to make an amp that hits the $100 mark. There are obvious compromizes needed to hit that mark. The future builder can decide to use cheap transformers, pots and tubes to hit the price point, or spend a few more bucks for the good stuff. We are here to provide the information.
I have a 100 watt Park (Marshall made) and a 2 X 30 watt Guild amp. Both are stuffed in the warehouse because I don't have the space for them here, and they are kinda LOUD! I WILL design something in the $100 range that I WILL use myself. Of course anything is an improvement over the Panasonic boom box that I use for a guitar amp. One of the guys in my wood shop class saw me making the speaker cabinet. He now wants amp #2.....
Surely for a 2watt design even a mismatched OTL design would do - eliminating the OPT completely..?
Actually I think I am running at little less than a watt output, would like a little more for the 8" speaker, the 10" and the 12" are more than bedroom levels. I still want to up the voltage and possibly try a phase inverter. Might deviate from the design parameters (no semiconductors) but then again I have always had a problem with rules.
Even at 2 watts the peak currents into an 8 ohm speaker are in the 1/2 amp range. Maybe the OPT goes away, but the power transformer just got more expensive. Tubes that can pass this current tend to have hungry heaters. You are free to experiment and prove me wrong.
If you want something easy, then buy the box from China, rip it up, mod the $*#@%^ out of it and post your results. It may not fit the contest, but it is a valid way to get started. Google around and you can find several cheap amps from China for less than $100.
I expected from the beginning that there will be a lot of talk but probably only a few amps built. It has always been this way. If you look at the amp design threads in the past that have several hundred posts and a dozen or more posters all talking about building an amp, only one or two actually get built.
First off, I have yet to see a list of posted "rules". Most true contests state exact rules and judging criteria up front.
Second, this isn't about the contest. Does "winning" really matter? I have already spent over $500 on parts to "win" $100. I knew that when I posted the two words that started it all. This was the motiviting factor that got me started on something that has been in the back of my mind for a long long time.
So if you don't like the rules, build your amp your way and show us what you made. Maybe you won't get $100, but you will still get your amp, and we get to see another persons viewpoint on what their ultimate amp is. Google the guitar amp building world, 90% of the amps being built are still derivatives of the SOS. It's time for some new stuff.
Those who have followed the Tubelab designs know that there will be a PC board and one or more mosfets. I am making the prototype in modular form so that the preamp, power amp, and power supply are all designed independent of each other. So when this contest is done, the preamp will get used for something a little bit BIGGER.
For those looking for a reasonable cost 12" speaker, I see these popped up on ebay again.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1506268929
$12.99us
It IS an Eminence speaker, but appears to be some kind of OEM overflow unit. They seem to pop up about every 4-6 months.
The speaker specs sheets leads me to believe it is a possibly custom 12 inch version of the Legend series?
NO AFFILIATION, just a bargain I located last night.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1506268929
$12.99us
It IS an Eminence speaker, but appears to be some kind of OEM overflow unit. They seem to pop up about every 4-6 months.
The speaker specs sheets leads me to believe it is a possibly custom 12 inch version of the Legend series?
NO AFFILIATION, just a bargain I located last night.
Just trying for a bit of humor, upfront I said I did not considered being a contender. I think we might even get more participation if we just skip the contest thing and just keep the idea of building a bedroom practice amp. Use spare parts, build it in a cardboard box (well maybe not cardboard). I will not bother searching out prices of every last part, might give the rough values of items, any more than that and it will seem like I am still at work. That takes all the fun out of it.
This thread spun off of one where someone was selling a cheap amp kit for for somewhere around $70-80 (too lazy to look it up). Some felt it not worth the money and you can do better on your own. Well it seems not as easy as first thought if you want to make something better and are paying retail. I would not spend the $70 on the advertised amp but I would spend the equal amount building mine.
I am not breaking new ground with my build, just taking ideas from other amps and incorporating them.using to come up with something playable.In the end I will be using it so I am more concerned with pleasing myself rather than anyone else at this time.
Power stage and phase splitter finished. I'm using an SE OPT salvaged from tube radio. It has several primary tabs, 0-0.8K-1.6K-3.2K. Secondary is 3.2Ohms. My amp has a tube rectifier - Telfunken AZ11. Surprisingly I have no hum (OPT severely unbalanced), my phase splitter is a paraphase design stolen from an Ampeg amp. It's good for 6SL7's and 6SN7's. Money spent so far ~ 50 bucks. Preamp still in the designing process.
It's not about the money, ancient Greek Olympic champs did only get an olive crown still they felt happy gods because of the glory and honor achieved.
I want to be voted, if I win the money would go to the next legal design with the highest rank. I think this is a good idea for all of those who want to participate outside the rules.
Leader? Perhaps instigator would be a better term. 'Leader' implies superior knowledge and experience, and I hardly qualify on either count.
Yes, the game is still on. I never did post a hard-and-fast set of final rules, and for that I apologize. Let's call these guidelines, instead -- the intent and spirit of the challenge is pretty straightforward:
1.) The goal is to construct a low-power tube guitar amplifier, from commonly available parts, for less than $100. The total cost excludes the chassis, cabinet, and speaker, as well as the shipping cost for the parts.
2.) The intent is to develop a robust, easily-modified basic design which can be constructed by someone with basic electronic assembly skills. The design can then be modified and expanded to taste, but the basic functional circuit
needs to meet the $100 parts-cost limit. For example, I'm experimenting with a basic pentode-drive-SE pentode topology. No innovation here; just trying different combinations of off-the-shelf parts. Once I have a functioning amplifier which satisfies me, then I may play with tone stacks or component upgrades. Think of a Fender 5C1 and how it evolved -- my first objective is to build the simple version first, and have it sound good within its limitations.
3.) The deadline for submission of your circuits and (hopefully) photos is October 30th of this year. This should give people time to narrow down their design concept, and breadboard a prototype. Whether the designs fade into oblivion, or grow legs, has yet to be determined.
4.) Above all, this is supposed to be an enjoyable diversion, not work. No one gets called into the office if they decide to abandon their project. No one gets a letter of reprimand if they go over budget, or decides to go off on a completely different tangent. The original trigger for this whole thread was one person's absolute pronouncement that a better practice amplifier than his could not be built for the same price. Many people thought, and one person responded, "Wanna bet?". And the challenge was launched...
*******************************************
My own tinkering with this project has been both fun and enlightening. I've never built a guitar amplifier before, and I'm learning about a whole new genre with a very different set of criteria than amps built for accurate reproduction of recorded music. I've never used a pentode for an input stage before, and I've never purposely overdriven a tube. I've never built a minimally-sized power supply, which loses current and/or voltage regulation (sags) when the amp is driven hard. I've never used tone controls (although one won't be in my core design, I'm going to experiment with them later).
In short, I'm learning, I'm having fun, and I'm doing it on the cheap. I hope that others will do the same.
I did not realize the date was extended, I must have missed that.
From page #1
Maybe I can still make it.
BTW, I am working on PP 6W6BT ($3.00 ea) which gives further options for using salvage PT's combined with 12W6GT & 25W6GT.
Or it could be converted to 6V6 if desired,
The part that keeps me going over budget is the VVR which I really want to use to get it to bedroom / headphone levels easily.
I have mine partially assembled, Chassis punched, sockets mounted/wired, eyelet board made and ready to complete.
Money for winning? Heck, I would just donate it or use part for a paid membership here.
Speaker link corrected
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150626892938
From page #1
Maybe I can still make it.
BTW, I am working on PP 6W6BT ($3.00 ea) which gives further options for using salvage PT's combined with 12W6GT & 25W6GT.
Or it could be converted to 6V6 if desired,
The part that keeps me going over budget is the VVR which I really want to use to get it to bedroom / headphone levels easily.
I have mine partially assembled, Chassis punched, sockets mounted/wired, eyelet board made and ready to complete.
Money for winning? Heck, I would just donate it or use part for a paid membership here.
Speaker link corrected
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150626892938
Last edited: