If one on a tight budget wants to build a great-sounding tube power amplifier for stereo music listening, which valves/tubes are cheapest? Most important is that it should be a tube that you expect will still be manufactured many years from now. Also it must be considered that the valve/tube is not costly to implement since that would defeat the purpose of choosing a cheap tube. I will try to edit op with your candidates. They can be for fleawatt lowwatt or highpowered amps. Cheers!
6L6 -20 dollars each. Use Push-Pull or single ended Pros: used widely in guitar amps so should be available a long time.
EL 34- Pros: Same as above
6BM8- Pros: triode and pentode in one so no need for preamp tube.
EL 84- Dirt cheap Pros: Same as above?
6L6 -20 dollars each. Use Push-Pull or single ended Pros: used widely in guitar amps so should be available a long time.
EL 34- Pros: Same as above
6BM8- Pros: triode and pentode in one so no need for preamp tube.
EL 84- Dirt cheap Pros: Same as above?
Last edited:
Use a 6L6 P-P or SE. All of the guitar amps out there that use these will likely ensure that they will be made for years to come. New ones start at less than $20 US each. Of course transformers are the single largest expense in a tube power amp build but using a 6L6 means a low cost of re-tubing. About the same situation with EL34s too.
Steve
Steve
I would look at the 6BM8 tube.
It has a triode and a pentode in the same tube so it saves you the cost of not only buying a preamp tube, but it also saves on the cost of tube sockets and chassis space.
The runner up would have to be an EL84. They are cheap, plentiful, sound great in both pentode and triode mode, and there are tons of designs available for them.
It has a triode and a pentode in the same tube so it saves you the cost of not only buying a preamp tube, but it also saves on the cost of tube sockets and chassis space.
The runner up would have to be an EL84. They are cheap, plentiful, sound great in both pentode and triode mode, and there are tons of designs available for them.
Lots of good advice already, but I agree with Steve that the transformers are a greater cost, usually.
And, as Electrix said, it's hard to give a sensible answer without knowing more parameters about this hypothetical build project.
I try to stick to common 'guitar amp tube types' with my builds. After I'm dead my amps will probably end up in the dump, but like many, I like to imagine they will be treasured for many many years....and will need replacement tubes.
And, as Electrix said, it's hard to give a sensible answer without knowing more parameters about this hypothetical build project.
I try to stick to common 'guitar amp tube types' with my builds. After I'm dead my amps will probably end up in the dump, but like many, I like to imagine they will be treasured for many many years....and will need replacement tubes.
Its only possible to optimize for one parameter.
Either you want a good circuit on a budget or you want the cheapest circuit.
Either you want a good circuit on a budget or you want the cheapest circuit.
Any of the tubes suggested can make a good, maybe even a great, sounding amp. Determine what sort of a system you want to use them in and what budget you have available. New transformers will likely consume half of the budget. I don't know the situation where you live but charity shops, yard sales or what the Brits call car boot sales might yield old amps that can be used for donor iron (transformers). I've "harvested" some decent iron from old Heathkits this way.
Good luck, Steve
Good luck, Steve
I have a certain system in mind where I want to use an amp, but I made this thread for my self and others new to tube amps to get an overview of affordable builds with parts that are not likely to be unavailable too soon. So that they wont have to make a thread about the same. I actually have an old radio that I bought from lions club. It was stripped from valves, but may have a useable transformer (iron?)
Last edited:
What speakers are going to be employed? The amp and the speakers are "joined at the hip". A modest cost amp will have low O/P power. In turn, speakers with mid 90s sensitivity or better will be needed. TANSTAAFL!
If the power transformer is still functional, it may be of use in a low power stereoblock. The output transformer has little (no?) potential. A pair of O/P transformers are needed for stereo.
If the power transformer is still functional, it may be of use in a low power stereoblock. The output transformer has little (no?) potential. A pair of O/P transformers are needed for stereo.
What Eli said. Do you know what valves were used in the radio or at least the output valve? This way you will know the filament voltage the power trans is putting out. Chances are with three valves, for instance two EL84 and one ECC83 you could make an ~2 watt per channel SE amp. A pair of fairly inexpensive OPTs and you could have a nice little amp for a desktop system. Or maybe a flea watt 6SN7 setup like Ling's. See his thread on this forum.
Steve
Steve
Did they sell console stereos in Denmark in the 1950s and 1960s?
Here in the U.S. that's the cheapest way to go by far. I've pulled parts from various console stereos, typically for $20 to $30. Tubes used are pretty common and it's not unusual to find units where all the tubes still test good. Spend another $30 or so on some new caps and resistors and you're good to go.
Are you actually trying to put something together? Your post, especially the comment about how it can be anything from flea power on up, seems like it might just be a theoretical question on your part.
Here in the U.S. that's the cheapest way to go by far. I've pulled parts from various console stereos, typically for $20 to $30. Tubes used are pretty common and it's not unusual to find units where all the tubes still test good. Spend another $30 or so on some new caps and resistors and you're good to go.
Are you actually trying to put something together? Your post, especially the comment about how it can be anything from flea power on up, seems like it might just be a theoretical question on your part.
Last edited:
One could also make the argument that OTLs can be cheap. 6as7gs are still being made and usually go for ~20 bucks a tube. You might need a couple per channel, so you might be spending a little more money in tubes, but you could save on transformers.
Tubes like the 6as7gs need low voltage and high current, so cheaper toroid transformers can easily be used for the power transformer, but I have no clue how to handle the PSU filtering. The current draw will be so high that you will either need monster chokes or power resistors that can handle more than 20 watts.
Tubes like the 6as7gs need low voltage and high current, so cheaper toroid transformers can easily be used for the power transformer, but I have no clue how to handle the PSU filtering. The current draw will be so high that you will either need monster chokes or power resistors that can handle more than 20 watts.
Old Radios are unlikely to have a suitable output transformer.
If you are worried about using common tubes with good long-term availability, stick with the EL34, 6L6, 6V6, El84/6BQ5, KT88, KT66 or something along those lines. the 6L6, 6V6, EL34 and EL84 in particular are probably the four most common power tubes in the world and will be around for a long time. Iron is pretty obtainable for these. There is a bit of gap in the market when it comes to great output transformers suitable for the 6L6 at reasonable prices- the Dynaclones that are suitable for 6BQ5, EL34 and KT88 are not suitable for 6L6s, so you're limited to Edcor or Hammond, neither of which are as good as the Dynaco iron.
If you can wait, Edcor iron is a pretty good option for what it costs. Finding used iron can be a bit hit or miss depending on your luck and where you live.
If you are worried about using common tubes with good long-term availability, stick with the EL34, 6L6, 6V6, El84/6BQ5, KT88, KT66 or something along those lines. the 6L6, 6V6, EL34 and EL84 in particular are probably the four most common power tubes in the world and will be around for a long time. Iron is pretty obtainable for these. There is a bit of gap in the market when it comes to great output transformers suitable for the 6L6 at reasonable prices- the Dynaclones that are suitable for 6BQ5, EL34 and KT88 are not suitable for 6L6s, so you're limited to Edcor or Hammond, neither of which are as good as the Dynaco iron.
If you can wait, Edcor iron is a pretty good option for what it costs. Finding used iron can be a bit hit or miss depending on your luck and where you live.
The thread is as I said for an overview of affordable designs. For me, but also other interested. Personally when I have have finnished renovations and mods of a few too many speakers. I would like to build a low watt poweramp to drive only the tweeters from maybe 3000hz in a 3 way speaker with active croossover. It might very well end up with being the one that Eli contributed a lot to in the 3-5watt tube amp thread
For sure I will not be designing a new amp. Only use one of the designs that I find in this forum. Whichever iron i can salvage might of coarse tip the scale to suitable tube
Including this kind of info will get you more appropriate responses. Many designs might be relatively cheap to build but totally inappropriate for use as a tweeter amp using an active crossover.
Here's a build I did last summer based on one of the little Magnavox console amps.
Flea Power SET - Magnavox 12BH7 Mod
It works great with high efficiency speakers in any room or moderately efficient speakers in a small room and pretty much any speaker in a near field desktop setup. I'm actually using it exactly as you envision at the moment, running tweeters using an active crossover.
The cool thing about this design is that it is a true SET, not a triode wired pentode and, unlike Dave Gillespie's well known mod of this amp, you don't replace the stock OTs. NOS and strong used 12BH7s are fairly plentiful and at least two companies, JJ and EH, make new production versions which sell for under $20. The 6EU7 can also be found in new production or the socket can be rewired to accept 12AX7s.
While I doubt you'd find an old Magnavox console for $25 in a thrift store in Denmark, you might find something similar. And, of course, there is always eBay but it won't be as cheap - maybe $100 or so unrestored. But using an existing amp is definitely the way to go. No need to build a chassis, buy new sockets etc, just replace out of spec parts and you're all set.
As others have mentioned, transformers are typically a much larger expense than tubes which is why I always look for gear to scrounge transformers from. One source you might watch for is old reel to reel tape recorders which used low power SE amps.
Since you are based in Denmark - I am in Sweden - I have been picking up cheap tube powered Tandberg reel-to-reels. They seem quite plentiful in these parts.
If you get a stereo one, you get 2 ECC83's, 2 ECL86's, 2 EAM86 magic eyes and an ECC82 (Model 74).
It even has a switch to play from input as an amplifier, a preamplifier, and the internal speakers are quite reasonable. It is a single-ended design, with around 4W total power per channel.
The foot print is surprisingly small, and did I mention it comes in a solid teak case?
Unfortunately it is too nice to cannibalise!
If you get a stereo one, you get 2 ECC83's, 2 ECL86's, 2 EAM86 magic eyes and an ECC82 (Model 74).
It even has a switch to play from input as an amplifier, a preamplifier, and the internal speakers are quite reasonable. It is a single-ended design, with around 4W total power per channel.
The foot print is surprisingly small, and did I mention it comes in a solid teak case?
Unfortunately it is too nice to cannibalise!
- Status
- Not open for further replies.