The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    New Tubes save the world!

    Share

    Dogstar

    Posts : 81
    Join date : 2014-06-24

    New Tubes save the world!

    Post by Dogstar on Fri Nov 14, 2014 6:01 am

    Well...because of the hiss I was hearing and the thought it was coming from my VTA-ST-120 I replaced the tubes with Tung Sol KT120's and 12AU7's and a Weber WZ68 only to find the hiss coming from my Cary SLP03. I thought read that the Cary preamp came with Mullards from the factory but when I opened her up I found Electro Harmonix tubes so when I replaced them with Tung Sol 12AU7's I didn't feel so bad. Thought I'd be downgrading but as it turns out I plugged them in ...connected everything back up and my system sounds great.

    Even with no breakin to speak of the system does sound good. I biased the tubes to .500 VDC as suggested..with no loss in sound quality.

    I found a SL1200MkII that came with an Isoplatmat along with a KAB cabinet and a Shure M97xe. I was pleasantly surprised to find how nice it sounded. I also plugged in my Denon DL-110 and was really impressed with how well the system sounded. Even with a Cambridge Audio 651P phono preamp.

    Listening to new releases of mono Beatles LPs is simply amazing.

    Bob Latino
    Admin

    Posts : 2378
    Join date : 2008-11-27
    Location : Massachusetts

    Re: New Tubes save the world!

    Post by Bob Latino on Fri Nov 14, 2014 4:16 pm

    Dogstar wrote:Well...because of the hiss I was hearing and the thought it was coming from my VTA-ST-120 I replaced the tubes with Tung Sol KT120's and 12AU7's and a Weber WZ68 only to find the hiss coming from my Cary SLP03. I thought read that the Cary preamp came with Mullards from the factory but when I opened her up I found Electro Harmonix tubes so when I replaced them with Tung Sol 12AU7's I didn't feel so bad. Thought I'd be downgrading but as it turns out I plugged them in ...connected everything back up and my system sounds great.

    If your system has hum/noise/hiss/crackle or whatever noise, you should make an effort to isolate the noise to your amp, preamp or upstream components. The easiest way to test if the AMP is the source of the problem is to remove the interconnects between the amp and preamp AT THE PREAMP. Now turn the amp on. Next, short between the center pin and the outer shield on both of the interconnects that were plugged into your preamp with the metal side of a screwdriver. What you hear is the residual noise level of the amp. If you still hear the hum/noise/hiss/crackle then the AMP IS AT FAULT. If you don't hear "your noise" then the cause of the noise is upstream of your amp. The problem has to be in your preamp, CD player, turntable, or upstream interconnects.

    A common cause of noise in the VTA ST-70 and ST-120 amps are the driver tubes especially the center driver tube. In the M-125's the front driver tube is the most common cause of noise.

    Bob

    Dogstar

    Posts : 81
    Join date : 2014-06-24

    Re: New Tubes save the world!

    Post by Dogstar on Fri Nov 14, 2014 7:40 pm

    That is pretty much what I did according to MontanaWay's advise a few weeks ago. I replaced the tubes in the amp and still the hiss. Just to be sure before just spending money on more tubes for my preamp I connected a source directly to the amp since I have an attenuator on the amp . No hiss with that setup. Replaced the Cary preamp tubes and now the whole system is hum free.

    deepee99

    Posts : 1260
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: New Tubes save the world!

    Post by deepee99 on Sun Nov 16, 2014 6:26 pm

    Output tubes can give you grief, too. When MontanaWay and I were putting his new Big Boppers into my system -- rebuilt from my original M-125s -- we put in a stash of original TS 6550s at my request and got irregular thumps out the LH channel. First thought was it had to be in the preamp(s) or drivers cuz output tubes don't do that sort of thing. Last step in the process of elimination was the output tubes. We swapped the antique 6550s for a run-in set of TS-120s, and QED: dead quiet ever since. Having a toob sound system is like living in a never-ending detective novel, and when you arrive at the happy ending you do your damndest to screw it up again. lol!

    sKiZo

    Posts : 1285
    Join date : 2013-04-02
    Location : Michigan USA

    Re: New Tubes save the world!

    Post by sKiZo on Sun Nov 16, 2014 7:24 pm

    Tell the world!!



    Killer tshirt, btw ...

    https://tubedepot.com/products/revolt-against-the-solid-state-t-shirt

    ** Don't forget to stock up on BBQ sauce and rub while you're there. pig


    Last edited by sKiZo on Sun Nov 16, 2014 7:30 pm; edited 1 time in total

    deepee99

    Posts : 1260
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: New Tubes save the world!

    Post by deepee99 on Sun Nov 16, 2014 7:26 pm

    I want that T-shirt, though can't wear it until May or so.

    sKiZo

    Posts : 1285
    Join date : 2013-04-02
    Location : Michigan USA

    Re: New Tubes save the world!

    Post by sKiZo on Sun Nov 16, 2014 7:31 pm

    ?

    This should be good ...



    Long as we're on the subject of tube-head appropriate clothing, I found this one a bit back ...



    http://www.zazzle.com/robotron_vacuum_tubes_tees-235400571993333855

    Dogstar

    Posts : 81
    Join date : 2014-06-24

    Re: New Tubes save the world!

    Post by Dogstar on Mon Nov 17, 2014 1:44 am

    OK....now I'm perplexed.

    I performed the test Bob Latino posted before before I bought new tubes for my preamp. With a source plugged directly into my amp I have no hiss. That was pretty much what made me think it was the preamp tubes. The first time I started up my system after installing new tubes in the preamp after already installing new tubes and a Weber rectifier in the amp it started up fine. No hiss at all. The next time I stated it up I have hiss coming from the speakers no matter what source I have chosen to play through the preamp.

    After a few minutes the hiss disappears and all seems normal.

    I didn't open the amp to check for cold solder connections but that sounds like the next step. What do you think? Besides a cool T-Shirt?

    Dogstar

    Posts : 81
    Join date : 2014-06-24

    Re: New Tubes save the world!

    Post by Dogstar on Tue Nov 18, 2014 3:07 am

    Please help!

    sKiZo

    Posts : 1285
    Join date : 2013-04-02
    Location : Michigan USA

    Re: New Tubes save the world!

    Post by sKiZo on Tue Nov 18, 2014 3:41 am

    Seems to be heat related as you say it clears up once the system's been on for a while. Heat expands metals, which would tend to make cold connections tighten up.

    First things first though. Give all your tubes and sockets a good cleaning and re-tension the socket tangs. A slight twist of a small jeweler's screwdriver set between the metal and socket body works nice - it doesn't take much. Those will loosen up over time, and even more so when you're playing with them trying to fix a problem. I find that all tube pins aren't the same size either, so not a bad idea to test the sockets for tightness every time you swap.

    You'll also want to be careful and precise when setting and removing tubes. No rocking allowed. Pull straight up, and push straight in, with firm, even pressure. You can tell when a socket's "right" ...

    I'd also try swapping the interconnects first if you haven't already. Those go bad surprisingly often. Like the sockets, they should be a nice tight fit. RCA jacks can also loosen up over time and can be adjusted from the back using more or less the same process.

    Dogstar

    Posts : 81
    Join date : 2014-06-24

    Re: New Tubes save the world!

    Post by Dogstar on Tue Nov 18, 2014 3:56 am

    I'll follow through with these steps too. Thank you.

    deepee99

    Posts : 1260
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: New Tubes save the world!

    Post by deepee99 on Wed Nov 19, 2014 5:58 pm

    Dogstar wrote:I'll follow through with these steps too. Thank you.

    If you're pulling output tubes, octals of any sort or tube rectifiers, keep a very firm grip on the base of the tube. Otherwise your hand slips up and you end up with a handful of glass, which lets all the magic vacuum out of the tube, and all the metal parts are still in the socket. Did that to a brand new KT-88 a coupla years ago. Been there, done that, got the very expensive T-shirt.
    Skiz has an important point; if you take a micrometer to the pins of a modern Russian octal you'll likely find them a tad fatter than NOS American tubes. Which means the new tubes will create a larger hole in the socket, which might not make proper contact when replaced with an NOS tube unless the holes are re-tensioned. Another expensive T-shirt earned.
    Cheerio,
    d

    Dogstar

    Posts : 81
    Join date : 2014-06-24

    Re: New Tubes save the world!

    Post by Dogstar on Sat Nov 29, 2014 12:03 pm

    I tried the test Bob suggested. In the course of touching the screwdriver blade to the center pin and outer ring of the RCA interconnected I heard a loud clunk and a loud buzz and once both were in contact with the blade I did hear the hiss. I tried adjusting the tube contacts to tighten them and I cleaned them with DeOxit as well. I did this to both the KT-120 sockets as well as the rectifier and 12AU7 sockets. I'm not really sure I did a really good job as I was afraid of breaking the sockets so I didn't apply a lot of force. After that procedure I plugged my CD player directly into the output plugs in front since I have an attenuator. I powered it up and there was no hiss. So my next step was the preamp. I adjusted the contacts as well as cleaned the sockets again not applying a lot of force since I didn't want to break the sockets. Switching to other sound sources does not change the hiss.

    Unfortunately now...there is a low volume hiss even after playing for a long time whereas prior to this the hiss went away after everything seemed to warm up.

    I guess I'll perform this again taking more care to make sure all the connectors are tight and clean.

    My one question is is why did the amp have no hiss with the CD player directly plugged in...unless because I only had the attenuator at may 4 clicks up in volume.

    Dogstar

    Posts : 81
    Join date : 2014-06-24

    Re: New Tubes save the world!

    Post by Dogstar on Sat Nov 29, 2014 12:07 pm

    One last thing...the hiss is louder in the tight channel....and when I turned up the gain on the preamp the hiss did not increase in volume. Is this something that could help diagnose the problem?

    Dogstar

    Posts : 81
    Join date : 2014-06-24

    Re: New Tubes save the world!

    Post by Dogstar on Sat Nov 29, 2014 6:10 pm

    Decided to setup a Magnum Dynlab ST-2 to a Marantz ST-6000 tuner I have for this system. After getting everything all hooked up I decided to test out the amp one more time. So I disconnected the amp from the preamp. And so I wouldn't get the loud clunk and buzz I turned the attenuator down before making contact the RCA center pin and outer ring. Turned the attenuator all the way up and there was no hiss in either channel. I used some brand new Audioquest interconnects between the amp and preamp to make sure it wasn't the cable. The other cables coming from the source to the preamp are from Parts Express. Not expensive but not cheap ones. I'm pretty sure they aren't damaged.

    I'm going to try tightening the preamp contacts again but if anyone has any ideas or suggestions I'd appreciate some input....thanks Dogstar.

    corndog71

    Posts : 444
    Join date : 2013-03-20
    Location : It can get windy here

    Re: New Tubes save the world!

    Post by corndog71 on Sat Nov 29, 2014 7:49 pm

    In my limited experience preamps are often the noisy culprit and can be difficult to make truly silent. Sometimes it's a matter of simply having too much gain.

    I prefer to use Belton tube sockets as they provide a superior grip on the tube pins vs most of the nos sockets out there. Ceramic sockets in particular have given me lots of trouble.

    Dogstar

    Posts : 81
    Join date : 2014-06-24

    Re: New Tubes save the world!

    Post by Dogstar on Sat Nov 29, 2014 9:07 pm

    This is a Cary SLP03 preamp...less than a year old. I bought from a company in Milwaukee, Wi.

    The story is that the company had one listed on Audiogon for $1300. This one a demo model. I drove up to check it only to see it was badly visually damaged. The aluminum faceplate and display screen had deep scratches. The store owner offered to sell me a new one for $1600. I agreed. A week later I picked it up. The double box was factory sealed and when I first set everything up it performed perfectly. I've had to rearrange my systems setup quite a few times. Always careful in handling yet be connected and disconnected so many times probably contributed to this problem. The only time I swapped tubes was when I installed the new Tung Sols a month ago and then a few times after that while cleaning and tightening contacts. No other changes.

    Any suggestions please?

    Maintarget

    Posts : 208
    Join date : 2013-02-10

    Re: New Tubes save the world!

    Post by Maintarget on Sun Nov 30, 2014 11:28 pm

    Bob Latino wrote:
    If your system has hum/noise/hiss/crackle or whatever noise, you should make an effort to isolate the noise to your amp, preamp or upstream components. The easiest way to test if the AMP is the source of the problem is to remove the interconnects between the amp and preamp AT THE PREAMP. Now turn the amp on. Next, short between the center pin and the outer shield on both of the interconnects that were plugged into your preamp with the metal side of a screwdriver. What you hear is the residual noise level of the amp. If you still hear the hum/noise/hiss/crackle then the AMP IS AT FAULT. If you don't hear "your noise" then the cause of the noise is upstream of your amp. The problem has to be in your preamp, CD player, turntable, or upstream interconnects.

    A common cause of noise in the VTA ST-70 and ST-120 amps are the driver tubes especially the center driver tube. In the M-125's the front driver tube is the most common cause of noise.

    Bob
    Bob,

    I have an VTA ST-120 amp with the attenuator option what position would you recommend the attenuator be at for this test procedure?
    Thanks

    Bob Latino
    Admin

    Posts : 2378
    Join date : 2008-11-27
    Location : Massachusetts

    Re: New Tubes save the world!

    Post by Bob Latino on Mon Dec 01, 2014 12:14 am

    You can turn the attenuator all the way up to the right. When turned all the way up, the attenuator is basically out of the input circuit except for one extra solder joint.

    Bob

    Sponsored content

    Re: New Tubes save the world!

    Post by Sponsored content Today at 10:23 am


      Current date/time is Thu Sep 29, 2016 10:23 am