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    Tube Newbie

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    LeGrace

    Posts : 95
    Join date : 2016-08-07

    Re: Tube Newbie

    Post by LeGrace on Wed Aug 24, 2016 8:31 pm

    Want to see a grown man cry? Come over to my place. Just discovered triode mode. The sound flows out like liquid honey. Shocked

    LeGrace

    Posts : 95
    Join date : 2016-08-07

    Re: Tube Newbie

    Post by LeGrace on Thu Aug 25, 2016 6:05 pm

    Ordered two Weber copper tops today. Power tubes are still a mystery. How long do they last again? (ref Sovtek 6550's)

    Bob Latino
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    Re: Tube Newbie

    Post by Bob Latino on Thu Aug 25, 2016 6:43 pm

    LeGrace wrote:Ordered two Weber copper tops today. Power tubes are still a mystery. How long do they last again? (ref Sovtek 6550's)

    Hi Legrace,

    You should get 3000 to 4000 hours out of your Sovtek 6550WE output tubes ..This is about 3 or 4 years based on about 3 hours a day playing time. Driver tubes can last 5000 hours or so ..

    Bob

    LeGrace

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    Re: Tube Newbie

    Post by LeGrace on Fri Aug 26, 2016 11:30 am

    Thanks Bob! Is it OK to just wait around until they fail? Or is it better for the hardware to replace on a schedule with some measure of safety factor?

    Peter W.

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    Re: Tube Newbie

    Post by Peter W. on Fri Aug 26, 2016 11:47 am

    LeGrace wrote:Thanks Bob! Is it OK to just wait around until they fail? Or is it better for the hardware to replace on a schedule with some measure of safety factor?


    My experience is that tubes start to sound funky long before they actually fail. And in most cases, "failure" is benign inasmuch as the tubes simply stop working. There are a few issues, however, to keep in mind:

    a) Some tubes, with specific reference to small-signal tubes (12XX7 types for example) will fail so slowly as to have the user not realizing that the tube, not some other component, is the problem. Example: I have a Dynaco FM3 that was giving me fits fading in and out - that I attributed to alignment. Turned out to be the 12AX7 on the MPX board.

    b) Output tubes that do not fail suddenly tend to go buzzy or hum. And sometimes drive the user into questioning the power-supply. Similarly, rectifier tubes.

    So, it is usually a good thing for someone seriously into tubes to keep at least a simple emissions-type tube tester for screening purposes. NOT a necessity, but useful. The other rather simple expedient is to keep a spare set of tubes - and when there is some question, simple substitution can clear things up.

    I have some ordinary 1930s/1940s radio tubes with many thousands of hours on them that still work (and test) fine on my GM-type tester. However, modern audio tubes are driven at far higher levels than most vintage radio tubes such that the will wear out relatively much faster.

    Unlike transistors, our amps have "consumables"...

    LeGrace

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    Join date : 2016-08-07

    Re: Tube Newbie

    Post by LeGrace on Thu Sep 01, 2016 5:01 pm

    deepee99 wrote:
    LeGrace wrote:Working on the second M-125, much easier second time around. What's not easier is reverting to my old setup in the mean time, after that brief taste of tube sweetness! I see posts now about K120 tubes and copper rectifiers, I can see I'm just getting started!!

    LeGrace, don't rule out the Gold Lion KT-88s for output tubes. They're a bit spendier than the Tung-Sol KT-120s (both are Russian re-issues) but in my completely subjective opinion they just sound a little sweeter. Jim McShane at http://mcshanedesign.net/  is my go-to guy for Russian tubes and he stocks both. Jim was recommended to me by Bob L. a few years back and is a pleasure to deal with.

    Another word to the wise, from one who's been there, don't go overboard squandering a lot of money rolling output tubes. It's tough on the sockets and the law of diminishing returns applies. There's always "something better" out there than what you've got, but you'll go bug-nutty and broke trying to find it. Been there, done that, got the T-shirt. Plus, I've found that the front driver tube has far more influence on sound quality than the output tubes. I would seek Bob L.'s advice on that for starters, then get 10,000 opinions on the forum.

    Again, congratulations on your first successful M-125 build. They really are a joy.

    OK per yr advice I contacted Jim. I said what about EH KT90's, his recommendation was same as yours, I should go for the Genalex KT88's. So I ordered two quads. If they improve on my current 6550's, then I'm in for a real treat!

    deepee99

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    Re: Tube Newbie

    Post by deepee99 on Sat Sep 17, 2016 12:38 pm

    LeGrace wrote:
    deepee99 wrote:
    LeGrace wrote:Working on the second M-125, much easier second time around. What's not easier is reverting to my old setup in the mean time, after that brief taste of tube sweetness! I see posts now about K120 tubes and copper rectifiers, I can see I'm just getting started!!

    LeGrace, don't rule out the Gold Lion KT-88s for output tubes. They're a bit spendier than the Tung-Sol KT-120s (both are Russian re-issues) but in my completely subjective opinion they just sound a little sweeter. Jim McShane at http://mcshanedesign.net/  is my go-to guy for Russian tubes and he stocks both. Jim was recommended to me by Bob L. a few years back and is a pleasure to deal with.

    Another word to the wise, from one who's been there, don't go overboard squandering a lot of money rolling output tubes. It's tough on the sockets and the law of diminishing returns applies. There's always "something better" out there than what you've got, but you'll go bug-nutty and broke trying to find it. Been there, done that, got the T-shirt. Plus, I've found that the front driver tube has far more influence on sound quality than the output tubes. I would seek Bob L.'s advice on that for starters, then get 10,000 opinions on the forum.

    Again, congratulations on your first successful M-125 build. They really are a joy.

    OK per yr advice I contacted Jim. I said what about EH KT90's, his recommendation was same as yours, I should go for the Genalex KT88's. So I ordered two quads. If they improve on my current 6550's, then I'm in for a real treat!
    I don't think you'll be disappointed, LeGrace. They're pretty tough, too. I dropped one about 6 feet onto a hardwood floor, and even after bouncing off the wood hutch on its way down it still works just fine. I think McShane burns them in for a day or two just to ensure no immediate defects, but give them about 50 hours to let them find their sweet spot, keeping an eye on bias. What you'll find is that from a cold start, you can set the bias to spec, but after an hour or two re-check and re-set same, as it tends to rise as the amp heats up. Again, methinks running them between .50 and .55 V per tube (1.1 on the pots) is more than plenty.
    Enjoy!
    dave


    LeGrace

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    Join date : 2016-08-07

    Re: Tube Newbie

    Post by LeGrace on Sat Sep 17, 2016 4:27 pm

    The KT88's sound amazing. 8 fuses later, I'm finally a happy camper! Since I changed over to the NOS Sovtek 5AR4 rectifiers no more blown fuses (rectifiers matter!). Now have a pair of copper tops as well, but holding on to them as backups.

    The Genalax KT88's vs the 6550's are like Scotch versus Irish whiskey. You will enjoy either, but one is just a tad smoother. Especially at the high end, very musical tube.

    Component wise changed my system around again. Had the M125's on my top shelf along with my Rega TT, for heat reasons. But my wife kept saying it looks busy. So I moved them down to the bottom shelf. To address heat buildup I placed low rpm Noctua 120 mm fans behind the amps. Curious what minimal airflow you need to effectively address heat issues...






    Last edited by LeGrace on Sat Sep 17, 2016 5:07 pm; edited 1 time in total

    Dave_in_Va

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    Re: Tube Newbie

    Post by Dave_in_Va on Sat Sep 17, 2016 5:04 pm

    It really doesn't take much air to keep the tube heat down. I have a clone of a '63 Vox AC30 guitar amp. The originals got super hot and so does my repro. So hot that I could barely touch the on/off or stand by switches. That heat had to come from the 4 EL84's through the chassis to get the front panel switches.

    I added a standard 12 volt computer type fan and tapped off the 6.3 v pilot light connections. The fan runs at half speed but the amp is plenty cool. You can barely feel the air move but that's all that was needed.

    LeGrace

    Posts : 95
    Join date : 2016-08-07

    Re: Tube Newbie

    Post by LeGrace on Sat Sep 17, 2016 5:24 pm

    I have the fans connected to a fan controller. Have each fan turned down to ~500 rpm, virtually inaudible. Air flow is really low, but I'm finding that's all it takes.


    LeGrace

    Posts : 95
    Join date : 2016-08-07

    Re: Tube Newbie

    Post by LeGrace on Mon Sep 19, 2016 1:25 pm

    Spoke too soon. Just watched my second 5AR4 tube rectifier go nuclear. Sad  We're talking MTBF running around 2.5 - 3 weeks! Always right after switching the amps on. So I'm going to give the Weber Copper Tops a go versus the 5AR4 tubes. Is there such a thing as a tough/reliable rectifier tube for these amps?  I can't be replacing these things every 2-3 weeks!

    Peter W.

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    Re: Tube Newbie

    Post by Peter W. on Mon Sep 19, 2016 1:33 pm

    LeGrace wrote:Spoke too soon. Just watched my second 5AR4 tube rectifier go nuclear. Sad  We're talking MTBF running around 2.5 - 3 weeks! Always right after switching the amps on. So I'm going to give the Weber Copper Tops a go versus the 5AR4 tubes. Is there such a thing as a tough/reliable rectifier tube for these amps?  I can't be replacing these things every 2-3 weeks!

    Country-of-Origin for that 5AR4?

    I find that with this particular tube in most Dynaco/Dynaco-Clone related applications, NOS US/Euro origin tubes are worth the freight. And in NO CASE WHATSOEVER, should any 5AR4 from China be introduced into valuable and/or valued equipment.

    Kentley

    Posts : 335
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    Age : 64
    Location : Worcester, MA

    Re: Tube Newbie

    Post by Kentley on Mon Sep 19, 2016 1:40 pm

    The Genalex new-issue seem to be the best of the Russian stuff. But to get a durable rectifier, it might be necessary to mine the caverns for old Mullard GZ-34, or better, GZ-37, or best, GZ-33. They ain't cheap. And there's the Mystery Factor of buying "NOS" and "NIB" and "slightly used" tubes. A good place to start is the venerable Andy Bowman, vintage tube master. Here's a link to get you started. BTW phone only - he don't do email. Great guy. http://vintagetubeservices.com/
    You are not alone. Many of us have gone through many, many glass rectifiers in our time. And Webers have been known to melt down, too. Good luck.

    LeGrace

    Posts : 95
    Join date : 2016-08-07

    Re: Tube Newbie

    Post by LeGrace on Mon Sep 19, 2016 2:09 pm

    Peter W. wrote:
    LeGrace wrote:Spoke too soon. Just watched my second 5AR4 tube rectifier go nuclear. Sad  We're talking MTBF running around 2.5 - 3 weeks! Always right after switching the amps on. So I'm going to give the Weber Copper Tops a go versus the 5AR4 tubes. Is there such a thing as a tough/reliable rectifier tube for these amps?  I can't be replacing these things every 2-3 weeks!

    Country-of-Origin for that 5AR4?

    I find that with this particular tube in most Dynaco/Dynaco-Clone related applications, NOS US/Euro origin tubes are worth the freight. And in NO CASE WHATSOEVER, should any 5AR4 from China be introduced into valuable and/or valued equipment.

    The first ones were Chinese, second ones Russian. The Russian tube lasted about twice as long, but 3 weeks is certainly nothing to crow about!

    I looked into those GZ tubes, yikers! I'm praying the copper tops will be the answer!

    deepee99

    Posts : 1336
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    Location : Wallace, Idaho

    Re: Tube Newbie

    Post by deepee99 on Mon Sep 19, 2016 2:13 pm

    I think you'll be happy with the Weber WZ68s, Just remember, even though they're solid state, they are consumables, just like tubes.

    Bob Latino
    Admin

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    Re: Tube Newbie

    Post by Bob Latino on Mon Sep 19, 2016 2:13 pm

    Legrace ... Check your line voltage ? Anything 122 VAC or above will cause the tube filaments to run at voltages noticeably higher than normal. These higher voltages will cause shorter than normal tube life.

    Bob

    LeGrace

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    Join date : 2016-08-07

    Re: Tube Newbie

    Post by LeGrace on Mon Sep 19, 2016 2:49 pm

    Bob Latino wrote:Legrace ... Check your line voltage ? Anything 122 VAC or above will cause the tube filaments to run at voltages noticeably higher than normal. These higher voltages will cause shorter than normal tube life.

    Bob

    Line voltage reads 199.99/120.0 V. Should I call my local utility?

    corndog71

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    Re: Tube Newbie

    Post by corndog71 on Mon Sep 19, 2016 3:20 pm

    Yep. Been there. This is why I switched to UF4007 diodes. Haven't had a single problem with them in 2 1/2 years.

    wgallupe

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    Re: Tube Newbie

    Post by wgallupe on Mon Sep 19, 2016 3:35 pm

    If there was a place to mount it, what would it take to add a second 5AR4? Is it as simple as running some parallel wires?

    With my ST-120 I have thought about relocating the quad cap to somewhere inside the chassis. Then, use a dremmel or something to open up the quad cap mounting hole to accommodate a larger tube socket. Run some parallel wires, plug in a second 5AR4. Same could be done on the M-125...

    Are there any downsides to this idea?


    Last edited by wgallupe on Mon Sep 19, 2016 3:55 pm; edited 1 time in total

    LeGrace

    Posts : 95
    Join date : 2016-08-07

    Re: Tube Newbie

    Post by LeGrace on Mon Sep 19, 2016 3:50 pm

    corndog71 wrote:Yep.  Been there.  This is why I switched to UF4007 diodes.  Haven't had a single problem with them in 2 1/2 years.

    Sounds like you know of what I speak. Kindly explain confused

    sKiZo

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    Re: Tube Newbie

    Post by sKiZo on Mon Sep 19, 2016 5:20 pm

    Ah, yes ... can't say as I miss my "nuclear rectifier" days since scoring a couple nice old stock GZ37s ...



    Done the "yellow sheet" mod on the rectifier socket? Couple simple diodes can make a big difference in saving your tubes.

    You could also add a thermistor to the hot side of the AC line. That acts to slow down the inrush current that can kill a tube. Another benefit ... They never go completely open and will usually drop the VAC one or two points, which is usually a good thing with the higher average levels we see nowadays. Just make sure you leave max clearance from your other components as they can get HOT.

    Mine was high enough I added a bucker to the mix to drop the line voltage. Amp seems much happier and more relaxed with that in line.

    sKiZo

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    Re: Tube Newbie

    Post by sKiZo on Mon Sep 19, 2016 5:30 pm

    Another trick if you want to improve cooling ... keep an eye out for laptop coolers that will meet the SO's approval. My HTPC ran very hot a couple builds back, and one of those was just the ticket for moving a lot of air with minimal noise.



    Seems to me a couple of those mounted to the bottom of the next shelf up would be work for ya. Most of them are made to use the USB connection on a laptop for power, but you can also get standalone power warts to plug into the wall.

    LeGrace

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    Join date : 2016-08-07

    Re: Tube Newbie

    Post by LeGrace on Mon Sep 19, 2016 6:49 pm

    Hilarious pic Skizo, except for the reality it reflects. Here is my take so far from the feedback:

    1) I can do a diode mod, except I wonder if its so great why has it not been incorporated into the standard design already? What's the catch? Or the thermistor mod? Even if I knew what this was the watch out for the HOT comment is alarming!?

    2) I can buy GZ37 or GZ33 tubes, the only examples of which I can find are NOS GZ37's at a cost of ~$150 USD each! By the time I get them into Canada with duty etc close to $500 for the pair. Sadly I cant afford this after what I've already invested. Was a stretch to start with.

    3) The Webers are working fine. Except for how long, plus the amps seem to have lost some of their mojo vs the tube rectifiers.

    Arghh!!!

    Kentley

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    Re: Tube Newbie

    Post by Kentley on Mon Sep 19, 2016 7:05 pm

    Just a reminder - always readjust bias levels when you switch out a rectifier. Every time. And it's best to lower them BEFORE you install the rectification, and bring 'em up to level after about a half hour warm up.
    If it ain't one thing.......

    deepee99

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    Re: Tube Newbie

    Post by deepee99 on Mon Sep 19, 2016 7:30 pm

    Yeah, what Kentley said. You might be losing some oomph thataway. Bias check is as important when changing rectifiers as it is with changing output tubes.
    Bias will max out at about 2 hours' running time. There's your setting.
    Do re-check it for a few days, then once a month is sufficient. Nothing to obsess about, just insurance.
    Good to keep a notebook handy and mark down any significant changes month-to-month. That will alert you to a tube or rectifier going lame. If all four tubes are doing weird things, then it's either the bias circuit, or a rectifier going south.
    The Webers are pretty tough dudes.

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