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.
+4
stewdan
Kentley
Maintarget
Schaale
8 posters
VTA SP 14 issues
Schaale- Posts : 7
Join date : 2016-09-21
Maintarget- Posts : 227
Join date : 2013-02-10
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.
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 : 496
Join date : 2015-03-06
Age : 71
Location : Worcester, MA
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
Thank you for the help. I'll take some pictures later today after my granddaughters birthday party.
stewdan- Posts : 231
Join date : 2010-03-07
Age : 85
Location : Houston Texas
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 : 496
Join date : 2015-03-06
Age : 71
Location : Worcester, MA
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
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 : 231
Join date : 2010-03-07
Age : 85
Location : Houston Texas
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
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- Posts : 7
Join date : 2016-09-21
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
- Posts : 3263
Join date : 2008-11-26
Location : Massachusetts
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
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.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.
pigface- Posts : 85
Join date : 2011-04-10
Location : pittsburgh
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 .
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The two red & green wire pairs on the lower right are going to the circiut board .
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Schaale- Posts : 7
Join date : 2016-09-21
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 : 85
Join date : 2011-04-10
Location : pittsburgh
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
I meant the grounds that go to the pcb from the volume switch
Roy Mottram- Admin
- Posts : 1839
Join date : 2008-11-30
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
Last edited by tubes4hifi on Fri Jan 18, 2019 6:51 pm; edited 1 time in total
Roy Mottram- Admin
- Posts : 1839
Join date : 2008-11-30
another photo . . .
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.
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.
Last edited by tubes4hifi on Fri Jan 18, 2019 6:52 pm; edited 1 time in total
Roy Mottram- Admin
- Posts : 1839
Join date : 2008-11-30
nothing new here, except these photos are from today, instead of the older ones on my webpage.
Tube Nube- Posts : 707
Join date : 2008-12-06
Age : 60
Location : Calgary, AB
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.
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.
Tube Nube- Posts : 707
Join date : 2008-12-06
Age : 60
Location : Calgary, AB
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.
I feel a bit like a kid, again, waiting for Christmas to hurry up and come.
Tube Nube- Posts : 707
Join date : 2008-12-06
Age : 60
Location : Calgary, AB
It's the logical progression of this condition, "upgrade-itis", where you order a component, and before ot's even received, you have to order its successor!
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