I see why you would want an isolation transformer, but so long as you know your house is not wired backwards I do not see why you need it (and then even a simple relay wired across neutral to ground switching the hot would protect you); unless of course you did not have plans to ground the amp... If these amps are floating, then how big of an isolation transformer should I get?
I get it with the ccs now, knew it was going to b+ but didn't realise that it would replace the inductor, I like that idea
BTW The filament transformers are EI construction
Thanks!
I get it with the ccs now, knew it was going to b+ but didn't realise that it would replace the inductor, I like that idea
BTW The filament transformers are EI construction
Thanks!
Are you willing to bet your life and the lives of other people in the house that the house wiring is all done correctly, cannot fail, has a perfectly secure ground that cannot fail, and is free of anything else drawing significant current? Get an isolation transformer, and I would be conservative and get one rated for 2x the anticipated load, at minimum.
Good advise SY. Its not worth the saving to risk your life. Frankly if your not prepared to take the risks of tube voltages seriously then I advise you to give up now.
Using EI's as outputs will be the weak link in the whole setup. There will be significant interwinding capacitance which will kill the top end response. Still it will give you a fair idea of what to expect with better transformers. I originally used some massive EI's as outputs and was amazed at the difference toroidals made.
Shoog
Using EI's as outputs will be the weak link in the whole setup. There will be significant interwinding capacitance which will kill the top end response. Still it will give you a fair idea of what to expect with better transformers. I originally used some massive EI's as outputs and was amazed at the difference toroidals made.
Shoog
I am fully aware of the dangers of the voltage used in this amp (which by the NEC definition is far from high voltage btw), and I am experienced in high (many of thousands of volts) voltage. I have yet to have any accident and do not foresee one anywhere in the future. I do appreciate you concern in the matter.
As to the comment to about it not being safe to use a device without mains isolation, you can use a few relays to make a device that is non-isolated fault proof as a device using an isolation transformer, and this technique is completely legal for use in the US, but I am not going to argue with you; isolation transformer it is.
Back to the amp design, I would need a isolation transformer that is rated for 80va? (assuming 4w out at 20% efficiency for 2 channels and a 100% operating)
Also, do you have a preferred css source for parafeed? Just a single DN2540 with a resistor from gate->drain?
Also, having decided on the output configuration, what should I use for the driver stage?
Thanks!
As to the comment to about it not being safe to use a device without mains isolation, you can use a few relays to make a device that is non-isolated fault proof as a device using an isolation transformer, and this technique is completely legal for use in the US, but I am not going to argue with you; isolation transformer it is.
Back to the amp design, I would need a isolation transformer that is rated for 80va? (assuming 4w out at 20% efficiency for 2 channels and a 100% operating)
Also, do you have a preferred css source for parafeed? Just a single DN2540 with a resistor from gate->drain?
Also, having decided on the output configuration, what should I use for the driver stage?
Thanks!
I'am glad to hear you have experience with high voltages. Its just the best solution to use the right part for the job.
In terms of CCS I would have a little difficult advising on a solid state one as I used a Pentode for mine. I seem to remember that the DN2540 would be the right part for the jo, though Gary Pimm recommends a cascade of two for much improved performance.
Take a look at this;
http://audioroundtable.com/Tubes/messages/929.html
In order to decide on the driver you need to know what input swing of the 6080 you will need.You will also need to know how hard it is to drive the grid of the 6080, this should be expressed as a wattage. From there you can search the net for something suitable to provide it. Its going to be a little difficult because you will have only a 130V +B for the driver. This suggests either a low voltage tube (6922 can work well at low voltages), or loading it with another CCS which would improve performance and lower the voltage requirement.
Shoog
In terms of CCS I would have a little difficult advising on a solid state one as I used a Pentode for mine. I seem to remember that the DN2540 would be the right part for the jo, though Gary Pimm recommends a cascade of two for much improved performance.
Take a look at this;
http://audioroundtable.com/Tubes/messages/929.html
In order to decide on the driver you need to know what input swing of the 6080 you will need.You will also need to know how hard it is to drive the grid of the 6080, this should be expressed as a wattage. From there you can search the net for something suitable to provide it. Its going to be a little difficult because you will have only a 130V +B for the driver. This suggests either a low voltage tube (6922 can work well at low voltages), or loading it with another CCS which would improve performance and lower the voltage requirement.
Shoog
Iam not convinced that the DN2540 will work in this application. Sourcing 200mA requires a very low bias resistor which will be prone to thermal drift and so current drift. It will also be extremely hard to set the bias point accurately in the first place.
Tubelabs reports good results with the IXYS 10M45.
Shoog
Tubelabs reports good results with the IXYS 10M45.
Shoog
I like the ixcp10m45s as the constant current source (mainly because they are not obsolete...), would I just use a simple resistor from gate->drain or do I still need to cascade 2 of them?
So, back to driving the tubes, what is the input swing I need for the 8060? This stage is really why I am coming to you guys, the calculating the values for everything...
Thanks!
So, back to driving the tubes, what is the input swing I need for the 8060? This stage is really why I am coming to you guys, the calculating the values for everything...
Thanks!
The 10m45 will work by itself. All it needs is a setting resistor and another resistor for stability. Do a search on Google and you should find tubelabs page on there use as a plate load.
My estimate of the situation with running your 6080 at 100V 100mA, says that the grid needs to be at about -35V.
This should be in the range of a medium Mu triode such as the 6922/ECC88, but I only like to run these at 7mA which may not be enough drive for the 6080. I have used the 5687, which has a lower gain but is happier running with a bit more current. Since you are getting some 10m45s I would simply get another two and load the triodes with them. This will allow you to get by with the +B you have, will cut down on power supply hum, and will allow the the 5687/6922 to give its maximum gain and its maximum linearity. It also saves on having to run unusual low voltage tubes in some type of cascade.
It depends a great deal on what preamp you are using. If the preamp you have is unity gain then the 5687 might struggle to give the voltage gain you need. If your preamp has some small gain then the 5687 should be fine. The only issue I might have with the excellent sounding 5687 is that it might need DC heaters otherwise it might suffer from heater induced hum.
Shoog
My estimate of the situation with running your 6080 at 100V 100mA, says that the grid needs to be at about -35V.
This should be in the range of a medium Mu triode such as the 6922/ECC88, but I only like to run these at 7mA which may not be enough drive for the 6080. I have used the 5687, which has a lower gain but is happier running with a bit more current. Since you are getting some 10m45s I would simply get another two and load the triodes with them. This will allow you to get by with the +B you have, will cut down on power supply hum, and will allow the the 5687/6922 to give its maximum gain and its maximum linearity. It also saves on having to run unusual low voltage tubes in some type of cascade.
It depends a great deal on what preamp you are using. If the preamp you have is unity gain then the 5687 might struggle to give the voltage gain you need. If your preamp has some small gain then the 5687 should be fine. The only issue I might have with the excellent sounding 5687 is that it might need DC heaters otherwise it might suffer from heater induced hum.
Shoog
I was looking at doing a similiar project, but to use the amp for a home surround sound Subwoofer. I have a couple extra 12" car subs and was just looking to d o it as a hobby. Whats the best place to start? I was thinking of getting an old Mirantz just to learn with, but figured it would be as easy to locate a schematic and orer some parts. I have a Mech. Engineering degree and had to take a year of circuits, so I'm somewhat famaliar with the designs. I tried starting a thread on this, but it keeps telling me to search first.
xirxious said:
That's right. If there are 49,000 members, and perhaps 1000 are interested in valves/tubes, then perhaps 800 of them are newbies. In which case, they're all likely to have similar questions. That's why we ask you to search first - because it's highly likely that your question has been asked (and answered) before. Of course, if you have a genuinely new question, or a very specific problem (like this thread), then there's no alternative but to start a new thread. You'll get the idea.
Oh, and welcome to the forum!
EC8010 said:
EC8010... from your statistics...the assumption ...It seems not many are interested in working/botching with valves/tubes on the bench.....I wonder how many potential wanna-be tubies go "shy because of high voltage working" ?
I'm coming up to 46 years working with tubes and high voltage (what I consider 200V upwards) and we are becoming are rare breed.
Perhaps an online (honest) poll would indicate a trend...
richj
High voltages ought to make people be cautious about getting into tube diy. But it's interesting that so many of us doing tubed hifi are in that 45-60 year old demographic. The younger fellows interested in tubes tend to come at it from the musical instrument side, or so it seems to me from reading the forum.
Some of them young whipper snappers do eventually seem to make the connection though, and I have a few friends well under 40 who are getting into tubes for hifi.. This is an expensive hobby, and when I was in my early 30's and getting into tube hifi it seemed that most of the people I was meeting were much older, perhaps they could afford the hobby at that point in their lives - children grown? (I never had any.) ..
kevinkr said:
Some of us had tubes passed down i.e I was weaned with the h.v hobby quite early on by 10 years age i.e around 1959. Poking about with h.v wasn't taken half so seriously as it is now, and I suspect alot of would-be tubers' these days have been deterred into "brainwashed safety culture" avoiding the h.v bug. There still a massive number of tubes still out there at reasonable prices. But as I mentioned before,these days the hobby aspect throughout the population everywhere is seriously lacking and so has the thinking quality of the human being. Then, evening courses at the local tech was recommended.
richy.
OK, I think I need to find a way to get this thread back on topic
As far as the driver tube, I don't have anything suitable. So I hope to buy them off of one of you guys (so that I could get the extra bits I need in one place too).
So, do any of you guys have a set of suitable tubes around? I can probably scrounge anything I need other than any particular specific devices (like a non inductive resistor, matched sets of stuff, inductors, sockets etc), so I would like to find someone that has a large stockpile of extra bits they are wiling to share...
That in mind... What do you suggest?
Also, I was looking around to figure out how to do the math to calculate the correct values for the components, but I need to know the indepedense e of the output... In a normal amp I would just use the o/p transformer, but how do you know what the correct value is for a ss css parafeed?
Thanks!
As far as the driver tube, I don't have anything suitable. So I hope to buy them off of one of you guys (so that I could get the extra bits I need in one place too).
So, do any of you guys have a set of suitable tubes around? I can probably scrounge anything I need other than any particular specific devices (like a non inductive resistor, matched sets of stuff, inductors, sockets etc), so I would like to find someone that has a large stockpile of extra bits they are wiling to share...
That in mind... What do you suggest?
Also, I was looking around to figure out how to do the math to calculate the correct values for the components, but I need to know the indepedense e of the output... In a normal amp I would just use the o/p transformer, but how do you know what the correct value is for a ss css parafeed?
Thanks!
The output impedance of a parafeed output stage is dominated by the tubes output impedance. Because the effective impedance of the CCS stage is so high it doesn't really come into it. Stick with the calculated output transformers.
Have you an old timer TV repair man in your local town. They usually have a stash of old tubes which can usually be press ganged into service.
Don't worry about the use of fancy components at this stage. The differences will not be huge - use what you have to hand to breadboard a test circuit up. If you like what you here then think about toroidal outputs before anything else.
If you were local I would try to help with components. Really all you need at this stage is a single dual triode driver tube. These can be had off ebay for dollars.
Shoog
Have you an old timer TV repair man in your local town. They usually have a stash of old tubes which can usually be press ganged into service.
Don't worry about the use of fancy components at this stage. The differences will not be huge - use what you have to hand to breadboard a test circuit up. If you like what you here then think about toroidal outputs before anything else.
If you were local I would try to help with components. Really all you need at this stage is a single dual triode driver tube. These can be had off ebay for dollars.
Shoog
Sy: I came at it from the Hi-Fi side of things,I can play an instrument about as well as I can draw,which=nil. 
I'm only 25,and got interested in HiFi and tubes years ago,when I was about 18,or so.
Here's a layout pic of my latest project: RA-100A
(got the chassis drilling mostly done tonight.)
Based on:
http://www.dogstar.dantimax.dk/tubestuf/ampindex.htm
Okay,Back to designing tube amps! </threadjack>
The 6080 usually needs a fair amount of voltage swing to drive it,IIRC.
Despite that,there have been all sorts of amps and preamps built around them. Pretty hefty tubes,and they look kinda cool too! But generally not a whole lot of power,but perhaps enough.
I've got a PP 6V6 amp,which does about 8Wpc,not alot of power,but it gets my power-hungry speakers rockin' in my small room.
The 30-35Wpc from my Dynaco ST-70 is "overkill" at times.
With reasonably efficient speakers,you won't need a whole lot of power.
Single Ended might be a possibility,or look into Push-Pull if you want more power.
Just be careful with the high voltage
I'm only 25,and got interested in HiFi and tubes years ago,when I was about 18,or so.
Here's a layout pic of my latest project: RA-100A
(got the chassis drilling mostly done tonight.)
Based on:
http://www.dogstar.dantimax.dk/tubestuf/ampindex.htm
Okay,Back to designing tube amps! </threadjack>
The 6080 usually needs a fair amount of voltage swing to drive it,IIRC.
Despite that,there have been all sorts of amps and preamps built around them. Pretty hefty tubes,and they look kinda cool too! But generally not a whole lot of power,but perhaps enough.
I've got a PP 6V6 amp,which does about 8Wpc,not alot of power,but it gets my power-hungry speakers rockin' in my small room.
The 30-35Wpc from my Dynaco ST-70 is "overkill" at times.
With reasonably efficient speakers,you won't need a whole lot of power.
Single Ended might be a possibility,or look into Push-Pull if you want more power.
Just be careful with the high voltage
At this stage you really need to go away and learn how a triode works. This will allow you to take any datasheet and calculate a good set of components around them. This will stand you in good stead for when things go wrong (as they will) and you can work out how to put them right.
All the hard design work has been done, and all you need to do is work out how to put the components together - this is basic engineering.
Shoog
All the hard design work has been done, and all you need to do is work out how to put the components together - this is basic engineering.
Shoog
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