Hello all, sorry for will probably turn out to be another newbie question, but hopefully from a slightly different angle...
Firstly, I know very little about tubes. I know they use lots of voltage, and glow nicely... I am pretty happy playing with electronics, and have some background in pro-audio although not in a design capacity.
So, some years ago I was given a small pile of valves, which I then stashed away in a cupboard at my parents place. Over Christmas said pile has come back to light and started me thinking what I could do with them. They are all mullard tubes with the following markings:
ECC83
EZ80
EF86 (x3 off)
EL84 (x2 off)
These numbers seem to correlate to a number of mullard designs (3-3, 5-10, 5-20) that I have dug up on the internet, but none of which do quite what I want to do as a first valve project. So, I have a few questions...
Since the best thing o start of with is something you actually want, I would like to build a small amp for my ipod (don't laugh). I have a couple of pairs of speakers available for use (one pair are 6 ohm and one are 8 ohm impedence).
So question 1:
All the designs I have found which use these tubes all also talk about a preamp being required. I am assuming that by using my ipod at line level as a source I don't need to worry about preamps... does that hold true?
question 2:
Are there any better designs for amps which utilise the tubes I have which give me a stereo amp or reasonable output? I am not averse to aquiring some more if required, but would really like to make use of these tubes.
question 3:
Can anyone suggest any good sources of transformers and bases for these tubes in the UK?
question 4:
How much does the impedence of the speakers matter to the overall performace of the amp? In the big stuff that I use, everything is at least 8 and some is 16 ohm impedence...
As I said, probably some really dumb newbie questions, but please be gentle...
Cheers
Mark
Firstly, I know very little about tubes. I know they use lots of voltage, and glow nicely... I am pretty happy playing with electronics, and have some background in pro-audio although not in a design capacity.
So, some years ago I was given a small pile of valves, which I then stashed away in a cupboard at my parents place. Over Christmas said pile has come back to light and started me thinking what I could do with them. They are all mullard tubes with the following markings:
ECC83
EZ80
EF86 (x3 off)
EL84 (x2 off)
These numbers seem to correlate to a number of mullard designs (3-3, 5-10, 5-20) that I have dug up on the internet, but none of which do quite what I want to do as a first valve project. So, I have a few questions...
Since the best thing o start of with is something you actually want, I would like to build a small amp for my ipod (don't laugh). I have a couple of pairs of speakers available for use (one pair are 6 ohm and one are 8 ohm impedence).
So question 1:
All the designs I have found which use these tubes all also talk about a preamp being required. I am assuming that by using my ipod at line level as a source I don't need to worry about preamps... does that hold true?
question 2:
Are there any better designs for amps which utilise the tubes I have which give me a stereo amp or reasonable output? I am not averse to aquiring some more if required, but would really like to make use of these tubes.
question 3:
Can anyone suggest any good sources of transformers and bases for these tubes in the UK?
question 4:
How much does the impedence of the speakers matter to the overall performace of the amp? In the big stuff that I use, everything is at least 8 and some is 16 ohm impedence...
As I said, probably some really dumb newbie questions, but please be gentle...
Cheers
Mark
Mark,
Just so you know, if those tubes are NOS (new old stock), you are looking at money. Mullard made tubes are QUITE desireable.
You could build a "5" WPC, single ended, pentode mode, stereo amp from the ECC83/12AX7 twin triode, the 2X EL84 power pentodes, and the EZ80/6V4 rectifier.
Selling the EF86s off could provide a nice "chunk of change" to help cover your expenses.
Sowter plus Stevens and Billington are UK sources of tube amp magnetics.
Just so you know, if those tubes are NOS (new old stock), you are looking at money. Mullard made tubes are QUITE desireable.
You could build a "5" WPC, single ended, pentode mode, stereo amp from the ECC83/12AX7 twin triode, the 2X EL84 power pentodes, and the EZ80/6V4 rectifier.
Selling the EF86s off could provide a nice "chunk of change" to help cover your expenses.
Sowter plus Stevens and Billington are UK sources of tube amp magnetics.
You mentioned the Mullard 3-3 among the designs that don't do what you want to do. Why is that? You could buld it without the tone control.
I agree, you shouldn't need to use an active preamp if the input signal is at line level. A volume control should do the job.
Regarding the speaker impedance, the only difference it makes is what ratio output transformer you need to use to match it to the OP tube loading requirement.
I agree, you shouldn't need to use an active preamp if the input signal is at line level. A volume control should do the job.
Regarding the speaker impedance, the only difference it makes is what ratio output transformer you need to use to match it to the OP tube loading requirement.
Thanks for the replies chaps, much appreciated.
The mullard valves are all boxed, and I believe them to be new (except the ecc83, which is in the wrong box), but I hadn't realised they were particularly valuable - does anyone have any links or ideas of what they might be worth? I am curious
ray_moth - the 3-3 I had not entirely discounted, other that in the versions I had found it is only a single mono amp as I haven't found a stereo version of it yet. Also the 3W output is a little low. Stereo versions of the 10 or 20W version seemed more appropriate. Thanks for the confirmation on the other points.
planet10 and Eli - your suggestions sound good, although I may have to do some reading to fully translate! Does anyone have any links for schematics or circuit designs for these systems or would it be a case of having to design something myself?
As I said, I am really a novice at the design side of this...
Thanks for your help, any more suggestions gratefully recieved.
Thanks
Mark
The mullard valves are all boxed, and I believe them to be new (except the ecc83, which is in the wrong box), but I hadn't realised they were particularly valuable - does anyone have any links or ideas of what they might be worth? I am curious
ray_moth - the 3-3 I had not entirely discounted, other that in the versions I had found it is only a single mono amp as I haven't found a stereo version of it yet. Also the 3W output is a little low. Stereo versions of the 10 or 20W version seemed more appropriate. Thanks for the confirmation on the other points.
planet10 and Eli - your suggestions sound good, although I may have to do some reading to fully translate! Does anyone have any links for schematics or circuit designs for these systems or would it be a case of having to design something myself?
As I said, I am really a novice at the design side of this...
Thanks for your help, any more suggestions gratefully recieved.
Thanks
Mark
Mark,
You can't get more than 5 WPC from 2X EL84s. The Laws of Physics are totally unyielding.
Extracting the value from the NOS would give you a financial head start on a project whose O/P power is more to your liking.
A very, very, very, nice 12 WPC ultralinear (UL) mode "El Cheapo" could be built employing Sowter's model U082, for the O/P trafos. The LENGTHY saga of "El Cheapo" is here.
BTW, a stereo amp is simply 2 mono channels. The power supply has to be competent and, as a consequence, that portion of "classic" designs must change. However, the signal topology is, with a few minor modernizing modifications, merely replicated twice.
You can't get more than 5 WPC from 2X EL84s. The Laws of Physics are totally unyielding.
Extracting the value from the NOS would give you a financial head start on a project whose O/P power is more to your liking.
A very, very, very, nice 12 WPC ultralinear (UL) mode "El Cheapo" could be built employing Sowter's model U082, for the O/P trafos.
The LENGTHY saga of "El Cheapo" is here.BTW, a stereo amp is simply 2 mono channels. The power supply has to be competent and, as a consequence, that portion of "classic" designs must change. However, the signal topology is, with a few minor modernizing modifications, merely replicated twice.
Search "Completed Listings" (Small box on the left) in eBay for Mullard EL84 or Mullard EF86 to see what kinds of prices people have been paying. You might need to register with eBay to do this. Then come to your own decision about what price to ask either here on the forums or eBay.BusShed said:
Also: What efficiency are your speakers? That should be the first and most fundamental question when deciding what kind of tube amp to build.
fwiw...
build with what you have. Forget about what you want in terms of output power - its going to be irrelevant once you get hooked on tubes anyway. The research and practice involved in simply building anything with those tubes will be the most valuable part of the whole experience. Best bit is - if you don't like what you hear at the end, the tubes are still resellable - they are not irrevocably committed to the circuit. Don't forget to keep the boxes pristine!!!
There are heaps of real simple EL84 based SE circuits around that will match your tube line-up, a couple of which have already been mentioned here. Choose one you like, and build it.
build with what you have. Forget about what you want in terms of output power - its going to be irrelevant once you get hooked on tubes anyway. The research and practice involved in simply building anything with those tubes will be the most valuable part of the whole experience. Best bit is - if you don't like what you hear at the end, the tubes are still resellable - they are not irrevocably committed to the circuit. Don't forget to keep the boxes pristine!!!
There are heaps of real simple EL84 based SE circuits around that will match your tube line-up, a couple of which have already been mentioned here. Choose one you like, and build it.
I don't understand what you mean. The 3-3 is just as capable of fulfilling a stereo function as any other design. The 'stereo version' of any amplifier is just two identical 'mono' amps working side by side to power the left and right channels respectively. Of course, you have the choice of building two completely independent mono amps, each with its own chassis, power supply and volume control, or a stereo amp on one chassis with a higher-capacity shared power supply and a dual-gang stereo volume control, or some combination. Whichever way you do it, though, you can still get stereo.
As for 3 watts not being enough, you're not going to get much higher power than that from a single EL84 per channel. If you need more power, you could buy an extra pair of EL84s and build two push-pull amps. Since the EL84 is such a popular tube (for good reasons), there are dozens of designs using it, giving mostly 3 to 5 watts single-ended (e.g. Mullard 3-3) or 10 to15 watts push-pull (e.g. Mullard 5-10).
Thanks for your comments chaps.
I realise that a stereo amp is really just 2 mono amps with a shared power supply and a common volume control, I suppose I am really being lazy and hoping that I could find a tried and tested design where the power supply had been designed to run both channels and them both integrated onto the same chassis.
Having spent a large chunk of time yesterday reading some of the sites mentioned in the newbies thread, I have a lot better understanding if what is required, but mostly that I seem to need to do a lot more reading!
I like the idea of building with what I have; these valves, the speakers I have kicking around (Wharfdale diamond 7 Shelfstanders or a pair of small Denons - efficiency of which I have no idea) so I will start there. The idea of a stereo 5-10 seems to suite what I want best so I will see what can be done to achieve that. if anyone has a link to a power supply schematic that would achieve that it would be much appreciated...
Eli, I need to invest some time in your el cheapo thread... my initial glances over it have piqued my interest somewhat, even if it isn't applicable to my current pile of tubes...
I may go quiet now, while I do some reading and come up with some more dumb questions to bug you guys with.
Thanks again
Mark
I realise that a stereo amp is really just 2 mono amps with a shared power supply and a common volume control, I suppose I am really being lazy and hoping that I could find a tried and tested design where the power supply had been designed to run both channels and them both integrated onto the same chassis.
Having spent a large chunk of time yesterday reading some of the sites mentioned in the newbies thread, I have a lot better understanding if what is required, but mostly that I seem to need to do a lot more reading!
I like the idea of building with what I have; these valves, the speakers I have kicking around (Wharfdale diamond 7 Shelfstanders or a pair of small Denons - efficiency of which I have no idea) so I will start there. The idea of a stereo 5-10 seems to suite what I want best so I will see what can be done to achieve that. if anyone has a link to a power supply schematic that would achieve that it would be much appreciated...
Eli, I need to invest some time in your el cheapo thread... my initial glances over it have piqued my interest somewhat, even if it isn't applicable to my current pile of tubes...
I may go quiet now, while I do some reading and come up with some more dumb questions to bug you guys with.
Thanks again
Mark
BusShed said:
Well it sort of is. You can use the EL84s instead of 12AQ5*. The 12At7/ECC81 is a critical part of the design. If you are going to do a PP amp, you need 2x as many EL84s and since you'd really need to have them all the same, you should be flipping the NOS Mullards.
We built a Class A EL84/triode version of Eli's amp that is stunning (and 3.2 W).
For your 1st amp, consider that an SE amp, which you can build with the parts you have, uses half as many tubes and is this simplier.
dave
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