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    VTA SP 14 issues

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    Schaale

    Posts : 7
    Join date : 2016-09-21

    VTA SP 14 issues

    Post by Schaale on Sat Sep 24, 2016 12:37 pm

    Hi everyone new to the site.  I'm looking for some guidance.  I just finished up with my build of the sp14 and I'm having 2 issues.  The first is with the volume.  I have to turn the gain and volume all the was up to be able to hear it and it's just enough to hear it.  I checked the voltages and they are all what,they are suppose to be.  My other issue is if I hardly touch or a slight tap on the case, transformer, or turn the selector dial you can hear it though the speakers.   I can adjust the gain for each,channel and it seems like it's working.  Any help would be appreciated. I forgot to add that I was turning the selector knob with a cd playing and the volume went up real loud as I turned the dial between aux1 and aux2. It only happened once.

    Maintarget

    Posts : 209
    Join date : 2013-02-10

    Re: VTA SP 14 issues

    Post by Maintarget on Sat Sep 24, 2016 1:33 pm

    I built an SP-14 over a year ago the only area I was confused with was the volume & balance wiring, a common mistake is grounding from the circuit board to the volume or balance control.
    The twisted ground wire should only terminate on the circuit board and not on the volume control switch end.
    I would post pictures of your wiring the really helpful members of this forum will spot any issues.
    Once you have this figured out you are going to be in bliss
    Good luck.


    Last edited by Maintarget on Sat Sep 24, 2016 1:34 pm; edited 1 time in total (Reason for editing : additional message)

    Kentley

    Posts : 335
    Join date : 2015-03-06
    Age : 64
    Location : Worcester, MA

    Re: VTA SP 14 issues

    Post by Kentley on Sat Sep 24, 2016 1:36 pm

    Your volume issue might be solved simply with a thorough check of all wiring. Sounds to me as if there is an error in the input wiring. Your noise problem is called "microphonic tubes". 6SN7s are prone to this issue. It doesn't necessarily interfere with SQ, but it is annoying. What are you using for 6SN7s? - especially crucial are the two to the left of the board. These are the actual amplifying element.

    Schaale

    Posts : 7
    Join date : 2016-09-21

    Re: VTA SP 14 issues

    Post by Schaale on Sat Sep 24, 2016 2:59 pm

    Thank you for the help. I'll take some pictures later today after my granddaughters birthday party.

    stewdan

    Posts : 161
    Join date : 2010-03-07
    Age : 78
    Location : Houston Texas

    Re: VTA SP 14 issues

    Post by stewdan on Sat Sep 24, 2016 3:02 pm

    Hi Schaale and welcome aboard. For what it is worth, your tapping of the case or transformer with the sound coming thru the speakers sounds to me like some sort of grounding issue. I had a VTA 120 Amplifier where the ground was not firm somewhere on the unit and my tapping would come thru the speakers and also drop the volume. In my case, all the grounds were resoldered and reworked which cleared up my problem. It took awhile to find!!

    Kentley

    Posts : 335
    Join date : 2015-03-06
    Age : 64
    Location : Worcester, MA

    Re: VTA SP 14 issues

    Post by Kentley on Sat Sep 24, 2016 3:32 pm

    Stewdan may very well be correct about the noise issue. Microphonics is best described as a "pinging" or even a bell-like resonance. If you indeed have a grounding issue, it would be more of a sharp click or rasping sound.

    Schaale

    Posts : 7
    Join date : 2016-09-21

    Re: VTA SP 14 issues

    Post by Schaale on Sat Sep 24, 2016 4:18 pm

    It sounds more like when you tap on a microphone. I was thinking a ground issue or the volume connected wrong. Why would a.ground issue cause low volume?

    stewdan

    Posts : 161
    Join date : 2010-03-07
    Age : 78
    Location : Houston Texas

    Tapping Sound

    Post by stewdan on Sat Sep 24, 2016 5:40 pm

    Hi --- In my case, the amplifier would play fine for 10-15minutes and then when something heated up (I guess), it broke the ground contact and my volume would drop by more than half what it was.  

    If I then tapped the chassis or the tubes or the transformers, the tapping noise would come thru the speakers and sound crisp like when you tap a microphone.  The only mechanical part on the amp was the on/off switch so, I never bothered tapping that.

    After checking all the wiring and re-soldering all the ground contacts, my problem went away.

    From the time I started working the problem until no tapping noise came thru the speakers was something like 5 to 6 hours.

    Hope this helps and does not confuse.
    Stew

    Schaale

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    Join date : 2016-09-21

    Re: VTA SP 14 issues

    Post by Schaale on Sat Sep 24, 2016 6:43 pm

    I can't seem to figure out how to load a picture or I might not have enough post to be able to.  The wires going from the volume control to the in on the pcb.  I have a green and white and a red and white going to the in puts. The whites are both landed on the ground other the volume and on the circuit board.

    Bob Latino
    Admin

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    Location : Massachusetts

    Re: VTA SP 14 issues

    Post by Bob Latino on Sat Sep 24, 2016 7:24 pm

    Schaale wrote:I can't seem to figure out how to load a picture or I might not have enough post to be able to.  The wires going from the volume control to the in on the pcb.  I have a green and white and a red and white going to the in puts. The whites are both landed on the ground other the volume and on the circuit board.

    You have to be a member for at least one week to post a photo. Also - The forum will not host a photo. You have to host the photo on another web site. Read the sticky on how to post a photo on this forum.

    Bob

    Schaale

    Posts : 7
    Join date : 2016-09-21

    Re: VTA SP 14 issues

    Post by Schaale on Sat Sep 24, 2016 8:19 pm

    Maintarget wrote:I built an SP-14 over a year ago the only area I was confused with was the volume & balance wiring, a common mistake is grounding from the circuit board to the volume or balance control.
    The twisted ground wire should only terminate on the circuit board and not on the volume control switch end.
    I would post pictures of your wiring the really helpful members of this forum will spot any issues.
    Once you have this figured out you are going to be in bliss
    Good luck.
    I removed the white wires from the volume control and left them termed on the pcb.  Now with the power switch turned off I can hear faint music from the speakers.  When I turn it on I get music but it's a constant volume.  If you turn the volume or gains it stays the same volume but it induces a human as you turn up the volume.  I looked at the print again.  The print says it's a view of the back of the front panel. Ut it's laid out as if you where looking through the front panel.  I think I might have the ground and the wire on the other side shaped.  If you look at the switch from the back with the term points on the bottom  I have the ground on the right.

    pigface

    Posts : 72
    Join date : 2011-04-10
    Location : pittsburgh

    Re: VTA SP 14 issues

    Post by pigface on Sun Sep 25, 2016 11:49 am

    Here is a picture of my SP-14  wiring   .The attenuators are different but the connections should be the same . If you carefully trace the wires out you can tell were they connect to . It maybe of help ?

    The two red & green wire pairs on the lower right are going to the circiut board .

    [img][/img]

    [img][/img]

    Schaale

    Posts : 7
    Join date : 2016-09-21

    Re: VTA SP 14 issues

    Post by Schaale on Sun Sep 25, 2016 2:37 pm

    That's how I had them hooked up.  I had the white wires grounded on each end. I want to check to see if I have the white wires at the correct spot.  The ones that came with the kit don't have the terms marked for what,they are

    pigface

    Posts : 72
    Join date : 2011-04-10
    Location : pittsburgh

    Re: VTA SP 14 issues

    Post by pigface on Sun Sep 25, 2016 3:51 pm

    If im not mistaken the white wires from the attenuators that go to the source - tape switch do not get grounded on the source - tape switch end they are left unconnected .

    Schaale

    Posts : 7
    Join date : 2016-09-21

    Re: VTA SP 14 issues

    Post by Schaale on Sun Sep 25, 2016 3:57 pm

    I meant the grounds that go to the pcb from the volume switch

    tubes4hifi
    Admin

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    Join date : 2008-11-30

    Re: VTA SP 14 issues

    Post by tubes4hifi on Fri Oct 14, 2016 11:09 am

    here's the diagram straight out of the SP14 docs . . .


    also, here are two photos . . . .



    the volume controls in the photos are inverted from the diagram, slightly easier to wire that way.
    You need to connect the green, red, and black wires from the master volume to the inputs on the PCB.

    if that doesn't help, ask directly . . . . info@tubes4hifi.com

    tubes4hifi
    Admin

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    Re: VTA SP 14 issues

    Post by tubes4hifi on Fri Oct 14, 2016 12:30 pm

    here's two more photos, taken this morning, using the wiring diagram!
    Come on, it's 3 wires on a volume control!
    I just need to connect the center terminals of the master volume control to the inputs on the PCB, along with the ground, of course.


    tubes4hifi
    Admin

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    Join date : 2008-11-30

    Re: VTA SP 14 issues

    Post by tubes4hifi on Fri Oct 14, 2016 3:17 pm

    nothing new here, except these photos are from today, instead of the older ones on my webpage.



    Tube Nube

    Posts : 643
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: VTA SP 14 issues

    Post by Tube Nube on Sat Oct 15, 2016 7:22 pm

    Pretty sure the amplified knock knock knocking you hear when you tap the pre amp is microphonics.

    As others have said, octal tubes are vulnerable to this. My SP14 does this, and it was built by the designer and master himself. Not an issue as far as I can hear whist the music plays.

    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: VTA SP 14 issues

    Post by deepee99 on Fri Oct 21, 2016 3:33 am

    Tube Nube wrote:Pretty sure the amplified knock knock knocking you hear when you tap the pre amp is microphonics.

    As others have said, octal tubes are vulnerable to this. My SP14 does this, and it was built by the  designer and master himself. Not an issue as far as I can hear whist the music plays.

    Every model of tube is capable of microphonics. 6SN7s, 6CG7s, 12BH7s, you name it. I've got a microphonic 6SN7 in a driver volt-amp hole right now. Unless you bash it with a pencil eraser, it works just fine. Most do. If'n it gets to the point where a tube is causing a KLUNK! sound when you're spinning the selector switch, then yank the sucker.
    It's not a bright idea to thump a hot tube with anything heavier than a chop-stick, though. Sometimes even a gentle touch will reveal the culprit. But if it's not screwing with the sound, leave well enough alone.

    Tube Nube

    Posts : 643
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: VTA SP 14 issues

    Post by Tube Nube on Fri Oct 21, 2016 12:47 pm

    I continue to marvel at how excellent this pre amp is, microphonics notwithstanding. And I look forward to the November long weekend when "a friend of ours" from Nelson will be visiting and with him, bring my new CV181 tubes and a hand full of caps for the power supply section.

    I feel a bit like a kid, again, waiting for Christmas to hurry up and come.

    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: VTA SP 14 issues

    Post by deepee99 on Fri Oct 21, 2016 1:31 pm

    Tube Nube wrote:I continue to marvel at how excellent this pre amp is, microphonics notwithstanding. And I look forward to the November long weekend when "a friend of ours" from  Nelson will be visiting and with him, bring my new CV181 tubes and a hand full of caps for the power supply section.

    I feel a bit like a kid, again, waiting for Christmas to hurry up and come.
    Then Nube, sounds like you're on the verge of a DS-1. Better'n sex, at least in my dotage. Whilst your "Nelson friend" is visiting kick him in the arse about my KT-88 amp. Want it, need it, etc. You will love the Chinese tubes. I've run mine several hundred hours now and they just get sweeter and sweeter.
    You gonna fix his eyesight while he's there? I smell a trade coming on . . . although a Maule ride in the cloud-soaked Selkirks would be a close second.

    Tube Nube

    Posts : 643
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    Age : 53
    Location : Calgary, AB

    Re: VTA SP 14 issues

    Post by Tube Nube on Fri Oct 21, 2016 1:43 pm

    Yo Dave,

    If you have ordered that amp, I am convince you're gonna love it. I'll mention hearing of your eagerness.

    What's a DS-1?

    A Maule ride, you say? Hmmm. If I can ever get it together to replace the passport my dog ate (!), perhaps I can twist your arm into a drive in the country with me. You're so darn close, as the Maule flies, it's simply appalling that I haven't been down there to meet you in person long ago already!

    -Brenton

    tubes4hifi
    Admin

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    Re: VTA SP 14 issues

    Post by tubes4hifi on Fri Oct 21, 2016 7:18 pm

    Dave, the DS1 is old school now, the latest is DS2 (that's a SUPER SP14 for those not in the know . . . )
    Don't expect your amp for another 2-3 weeks from what I hear . . .

    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: VTA SP 14 issues

    Post by deepee99 on Fri Oct 21, 2016 7:24 pm

    tubes4hifi wrote:Dave, the DS1 is old school now, the latest is DS2 (that's a SUPER SP14 for those not in the know . . . )
    Don't expect your amp for another 2-3 weeks from what I hear . . .
    Grumble, grumble . . .
    A DS-2, eh? He's been holdin' out on me!

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