Thanks Steve!
Well, for now I'm still learning how to do good piano finish work as part of my hobby (I've managed it on small things, but these shelves are 6 feet tall!), so the painting is "half the fun". However in the future I hope to have more money than time (the reverse of my life now!
) so that's a terrific idea.
I'll check around here and see if the local body shops would touch a project like this at those sorts of prices; thanks again!!
All the best,
Morse
Well, for now I'm still learning how to do good piano finish work as part of my hobby (I've managed it on small things, but these shelves are 6 feet tall!), so the painting is "half the fun". However in the future I hope to have more money than time (the reverse of my life now!
) so that's a terrific idea.I'll check around here and see if the local body shops would touch a project like this at those sorts of prices; thanks again!!
All the best,
Morse
The thing I remember reading about X-rated caps is that they're designed to fail open rather than closed, as Morse said, and that's not guaranteed with other types of film caps. I put mine after the fuse and power switch. But this topic has probably been discussed enough already.
So this resistor would go in parallel across the primaries, in series with the capacitor? Could you please explain the benefits of that? Most power line filter circuits I've seen have resistors in series with each leg of the primary winding.
is that they're designed to fail open rather than closed, as Morse said, and that's not guaranteed with other types of film caps. I put mine after the fuse and power switch. But this topic has probably been discussed enough already.So this resistor would go in parallel across the primaries, in series with the capacitor? Could you please explain the benefits of that? Most power line filter circuits I've seen have resistors in series with each leg of the primary winding.
More questions.
Plate dissipation on Sovtek 2A3s - I've read several posts where people say that they've heard that these tubes can be run at higher than the classic 15W rating. I've read some posts saying they can do 40W, I've read posts by J. C. Morrison refuting this.
The Angela schematic runs them at ~ 18W for the cascaded 6SL7 version, and below 15W for the SRPP 6SL7 version. My plate voltage is around 345V and cathode voltage is around 55V with an 880 ohm resistor, so that's 290V*62.5mA or a little over 18W.
Does anyone have first-hand long-term experience with using these tubes at higher than 15W plate dissipation? Are there any detrimental effects to doing this? How does it affect the sound to be at a higher plate dissipation (besides higher output, of course)? Also, I've read some people say they like to run tubes at lower voltages and higher currents. I don't see how I can do that without changing my cathode bias resistor, but I'm still interested in peoples' opinions on that.
Thanks,
Saurav
Plate dissipation on Sovtek 2A3s - I've read several posts where people say that they've heard that these tubes can be run at higher than the classic 15W rating. I've read some posts saying they can do 40W, I've read posts by J. C. Morrison refuting this.
The Angela schematic runs them at ~ 18W for the cascaded 6SL7 version, and below 15W for the SRPP 6SL7 version. My plate voltage is around 345V and cathode voltage is around 55V with an 880 ohm resistor, so that's 290V*62.5mA or a little over 18W.
Does anyone have first-hand long-term experience with using these tubes at higher than 15W plate dissipation? Are there any detrimental effects to doing this? How does it affect the sound to be at a higher plate dissipation (besides higher output, of course)? Also, I've read some people say they like to run tubes at lower voltages and higher currents. I don't see how I can do that without changing my cathode bias resistor, but I'm still interested in peoples' opinions on that.
Thanks,
Saurav
NO PROBLEMA.
Hi,
In series is more like it.Look at it as a filter network.
The benefit is that it will "snub", attenuate any disturbance on the mains depending on what C and R you combine which will define the frequency it is effective.
40W out of a 2A3 is whishful thinking indeed, 18W dissipation is closer to home.
The more you squeeze out of them the more often you'll need to replace the valves...just like any other incandescent device you'll burn it up faster.
Yes, same thing really...the more current you allow to flow the better they sound ( usually), in order to allow for that you'll need to lower the cathode resistor.
Understanding loadlines and tubes in general is a plus, none of that is all that hard.
Keep in mind that there really are no limits to this though,so take your time...
Cheers,
Hi,
In series is more like it.Look at it as a filter network.
The benefit is that it will "snub", attenuate any disturbance on the mains depending on what C and R you combine which will define the frequency it is effective.
40W out of a 2A3 is whishful thinking indeed, 18W dissipation is closer to home.
The more you squeeze out of them the more often you'll need to replace the valves...just like any other incandescent device you'll burn it up faster.
Yes, same thing really...the more current you allow to flow the better they sound ( usually), in order to allow for that you'll need to lower the cathode resistor.
Understanding loadlines and tubes in general is a plus, none of that is all that hard.
Keep in mind that there really are no limits to this though,so take your time...
Cheers,
Hi Saurav;
I've got close to a year's running time on a set of SovTek 2A3's at the same plate dissipation as yours (345VDC B+, 55V bias) and (*knock on wood* as I type this!! ) so far no prob. Only dead valve in the amp was an early mortality 6SL7 (about the 800hr mark). Since I run this amp for maybe 4 hours per day on average (and have more than one 18+ hour listening session on it), you can get an idea of the number of hours on those 2A3's.
When I've run 'em about 35V hotter than this (maybe 200 hours like that), the sound seemed a little brittle somehow - but the amp seemed to have a little more 'oomph' too. FWIW, I went back to 345VDC and haven't considered bumping it back up to 380VDC.
Hope this helps!
All the best,
Morse
I've got close to a year's running time on a set of SovTek 2A3's at the same plate dissipation as yours (345VDC B+, 55V bias) and (*knock on wood* as I type this!!
) so far no prob. Only dead valve in the amp was an early mortality 6SL7 (about the 800hr mark). Since I run this amp for maybe 4 hours per day on average (and have more than one 18+ hour listening session on it), you can get an idea of the number of hours on those 2A3's. When I've run 'em about 35V hotter than this (maybe 200 hours like that), the sound seemed a little brittle somehow - but the amp seemed to have a little more 'oomph' too. FWIW, I went back to 345VDC and haven't considered bumping it back up to 380VDC.
Hope this helps!
All the best,
Morse
I would like to think that I have a bit of a handle on that, but you never know how much you don't know, do you
I do plan on taking my time learning things with this amp, as well as enjoying music of course. I just used the component values in the schematic, and didn't bother with plotting a load line for this amp. I'll eventually go back and do that.So 18W is probably not something to panic about. That's good to know.
So the idea is to try to pick a point on the plate dissipation curve that's high current and low voltage, while still being linear. That makes sense. Once I start feeling like changing things again, I'll figure out the current operating conditions of my amp, and see if I can pick a better one.
Morse, just saw your post. Thanks, that's good information to know.
I got a blob of solder down one of the octal tube socket legs yesterday, then got it on the carpet while trying to get it out. Grr... my landlady's going to be pretty unhappy by the time we leave this apartment. I dropped a soldering iron on the carpet once...
I got a blob of solder down one of the octal tube socket legs yesterday, then got it on the carpet while trying to get it out. Grr... my landlady's going to be pretty unhappy by the time we leave this apartment. I dropped a soldering iron on the carpet once...
Hi Saurav;
>>>...I dropped a soldering iron on the carpet once...<<<
Been there, done that - good to know I'm not the only one!!
Seriously though, if the solder blobbies aren't too big, sometimes you can CAREFULLY trim the little buggers out with a nail trimmer - without trimming out too much of the carpet (in other words, without leaving visible evidence that they were ever there!!). That was learned the hard way too, *sigh*
All the best,
Morse
>>>...I dropped a soldering iron on the carpet once...<<<
Been there, done that - good to know I'm not the only one!!
Seriously though, if the solder blobbies aren't too big, sometimes you can CAREFULLY trim the little buggers out with a nail trimmer - without trimming out too much of the carpet (in other words, without leaving visible evidence that they were ever there!!). That was learned the hard way too, *sigh*
All the best,
Morse
I'll try that the next time (I'm sure there'll be a next time). Our landlady is a bossy older woman who treats me and my wife as kids, and she mentioned several times that the carpet was brand new. I was pretty upset the first time I made a hole in it. My wife still gets upset, but it doesn't bother me much any more She's probably right though, I am kissing my security deposit goodbye. But I figured that until we can afford to live in a place with a garage, this kind of stuff is just something I'll have to accept. I'm not careful enough to never get solder on the carpet, and the only alternative is to take stuff outside on the porch every time I need to solder, which isn't very practical.
The feeling is mutual
She's probably right though, I am kissing my security deposit goodbye. But I figured that until we can afford to live in a place with a garage, this kind of stuff is just something I'll have to accept. I'm not careful enough to never get solder on the carpet, and the only alternative is to take stuff outside on the porch every time I need to solder, which isn't very practical.The feeling is mutual
When I was little...
I wasn't supposed to be doing things like soldering in my room, so when my mother came in (to check up on what I was doing?) I hurriedly moved to block her view. In doing so, I knocked my crude stand over, and the iron hit the carpet. Fortunately, she went out again quite quickly, but by then it had burnt through to the backing. I scraped the charred bits away, but there was still a very visible hole, so I had to strategically rearrange my room to obscure the evidence.
Of course, if she hadn't forbidden soldering, I wouldn't have knocked the iron over, and the carpet wouldn't have been burnt. So it was all her fault, really.
The nail scissors ploy works...
I wasn't supposed to be doing things like soldering in my room, so when my mother came in (to check up on what I was doing?) I hurriedly moved to block her view. In doing so, I knocked my crude stand over, and the iron hit the carpet. Fortunately, she went out again quite quickly, but by then it had burnt through to the backing. I scraped the charred bits away, but there was still a very visible hole, so I had to strategically rearrange my room to obscure the evidence.
Of course, if she hadn't forbidden soldering, I wouldn't have knocked the iron over, and the carpet wouldn't have been burnt. So it was all her fault, really.
The nail scissors ploy works...
Hi EC8010;
>>>...and the iron hit the carpet...<<<
And here I'd thought for years that dropping a soldering iron onto the carpet was something unique to my own experiences! Now that there are 3 of us in this group, there must be others.....
Perhaps it's actually something of a right of passage with DIY'ers** - albeit a nasty one that leads to all manner of rows with parents, significant others, and landlords..... Also makes a heck of a mess on the side of the iron, what with all that melted carpet burned onto it! At least with me it was a cheapie "Radio Shack" iron that was a pretty poor bit of kit from day one.
Now if it'd been my Weller that would have been different! I really would have been irritated then!
All the best,
Morse
**Another right of passage with at least some DIY'ers would be the experience of finding out just how thoroughly the smell of model airplane dope can permeate a house in record time, when doping the tissue onto the wings of his first flyable masterpiece - and with the windows wide open for ventilation, at that!
>>>...and the iron hit the carpet...<<<
And here I'd thought for years that dropping a soldering iron onto the carpet was something unique to my own experiences!
Now that there are 3 of us in this group, there must be others.....Perhaps it's actually something of a right of passage with DIY'ers** - albeit a nasty one that leads to all manner of rows with parents, significant others, and landlords..... Also makes a heck of a mess on the side of the iron, what with all that melted carpet burned onto it! At least with me it was a cheapie "Radio Shack" iron that was a pretty poor bit of kit from day one.
Now if it'd been my Weller that would have been different! I really would have been irritated then!
All the best,
Morse
**Another right of passage with at least some DIY'ers would be the experience of finding out just how thoroughly the smell of model airplane dope can permeate a house in record time, when doping the tissue onto the wings of his first flyable masterpiece - and with the windows wide open for ventilation, at that!
Radio Shack iron? Melted carpet? Wow, I thought I was the only one who'd done that. I discovered that the fibres in my carpet are a synthetic material that melt instead of burning when heated. And that was my first soldering iron too, a 15W RS unit with no holder, one of those little metal 'W' shaped stand thingies that don't work too well on carpets, as I found out.
Morse, a screen grab of my PSU is posted on page 6 of this thread. I have a 5AR4 with 3uF - 10H - 100uF which feeds both 2A3's, then 27K - 100uF to each of the 6SL7s. This gives me around 345V at the plates of the 2A3s, and 320 or so at the 6SL7s.
Morse, a screen grab of my PSU is posted on page 6 of this thread. I have a 5AR4 with 3uF - 10H - 100uF which feeds both 2A3's, then 27K - 100uF to each of the 6SL7s. This gives me around 345V at the plates of the 2A3s, and 320 or so at the 6SL7s.
Hi Saurav;
Darned if I can remember how many watts that old RS iron of mine was rated at, but I remember that #$*&%^#@!! "w" shaped metal stand all too well. Frankly I soon found that a big ashtray made a better holder (less likely for the iron to slip out). Worst thing about those RS irons was that they had tips that wouldn't last past one or two soldering sessions at the most. Funny thing is that since I went with a good iron, I've been through exactly one tip - and I put years of use on that one....
Your PSU is really similar to mine. I used 20uF->10H->100uF->27kr->40uF with the B+ taps at 100uF and the B'+ taps (to the 6SL7's) at the 40uF. Our voltages are pretty much identical as you would expect.
Only real diff is that I bypassed all my caps with series pairs of .22uF 400V film and foil caps (Daytons). It didn't make as big an improvement as did the RF filter cap, but it definitely did smooth things out in the midrange.
By the way, here's a crazy idea. I see that you're still up in the air with where you want your B+ and that's causing you some grief in terms of setting a consistent heater/cathode potential on the 6SL7's. Why not put a potentiometer in series with the voltage divider, between the 2 resistors? Then draw the offset voltage from the wiper of the pot. You'd need to do a little math to give yourself enough adjustability in the pot and make sure it can handle the 1 or 2mA of current. Just an idea, but I thought it might work for you.
All the best,
Morse
Darned if I can remember how many watts that old RS iron of mine was rated at, but I remember that #$*&%^#@!! "w" shaped metal stand all too well. Frankly I soon found that a big ashtray made a better holder (less likely for the iron to slip out). Worst thing about those RS irons was that they had tips that wouldn't last past one or two soldering sessions at the most. Funny thing is that since I went with a good iron, I've been through exactly one tip - and I put years of use on that one....
Your PSU is really similar to mine. I used 20uF->10H->100uF->27kr->40uF with the B+ taps at 100uF and the B'+ taps (to the 6SL7's) at the 40uF. Our voltages are pretty much identical as you would expect.
Only real diff is that I bypassed all my caps with series pairs of .22uF 400V film and foil caps (Daytons). It didn't make as big an improvement as did the RF filter cap, but it definitely did smooth things out in the midrange.
By the way, here's a crazy idea. I see that you're still up in the air with where you want your B+ and that's causing you some grief in terms of setting a consistent heater/cathode potential on the 6SL7's. Why not put a potentiometer in series with the voltage divider, between the 2 resistors? Then draw the offset voltage from the wiper of the pot. You'd need to do a little math to give yourself enough adjustability in the pot and make sure it can handle the 1 or 2mA of current. Just an idea, but I thought it might work for you.
All the best,
Morse
Saurav: Yay! Another Tubehead! Glad your amp is singing nicely
I've also done the RS iron on the carpet it more than once (4-5 of us now?)...I've even dropped it on my forearm once! (OWWWW!!,I still have the scar..you can see the outline of the iron,and tip,even the round burn of the phillips head screw,complete with the + in it!)
And yes,those dumb RadioShack tips vanish into thin air.. Mine is currently only about 7-8mm long!!! Time to buy a new iron..
New tips - $4.99
New iron - $5.99,I just buy a new iron everytime..
Ohh,and I hate those dumb "M"stands also.. I get one with every new iron,so I've got a few..I've found that a pair of regular pliers works well for a "stand",Just seperate the handles a bit so the iron will sit between them,and be somewhat stable. (Be sure to use pliers without insulated handles,that stuff STINKS when it burns.)
The pliers can then double as a hand warmer on those cold days! Seriously,be careful,I've picked up HOT pliers more than once.
I've also done the RS iron on the carpet it more than once (4-5 of us now?)...I've even dropped it on my forearm once! (OWWWW!!,I still have the scar..you can see the outline of the iron,and tip,even the round burn of the phillips head screw,complete with the + in it!)
And yes,those dumb RadioShack tips vanish into thin air.. Mine is currently only about 7-8mm long!!! Time to buy a new iron..
New tips - $4.99
New iron - $5.99,I just buy a new iron everytime..
Ohh,and I hate those dumb "M"stands also.. I get one with every new iron,so I've got a few..I've found that a pair of regular pliers works well for a "stand",Just seperate the handles a bit so the iron will sit between them,and be somewhat stable. (Be sure to use pliers without insulated handles,that stuff STINKS when it burns.)
The pliers can then double as a hand warmer on those cold days! Seriously,be careful,I've picked up HOT pliers more than once.
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