Kingley
1768 posts
Feb 10, 2012
8:50 AM
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I'm in the process of attempting some mods on my VHT Special 6. I plan to add a line out as well. Most of it I understand,except for a couple of things. I'm pretty thick when it comes to amp mods, having never done more than swap valves and speakers.
The instructions are as follows: 2.2k ohm resistor from the internal speaker jack tip (the 8 ohm speaker tap is active in my amp) to the line out jack tip.
470 ohm resistor from line out jack tip to circuit board ground.
.0047 mfd cap from line out jack tip to circuit board ground.
Line out jack sleeve to circuit board ground and chassis.
Can someone please enlighten me as to what "circuit board ground" is. I also don't understand what "jack sleeve to circuit board ground and chassis" means.
Any help anyone can offer would be greatly appreciated.
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7LimitJI
600 posts
Feb 10, 2012
9:11 AM
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Circuit board ground is the chassis, which in turn is connected to the earth lead going to the plug.
The line out jack is earthed to the chassis via the thread and nut that holds it to the chassis.
Basically any connection to the chassis is earth.
When building an amp there can be several "earth" points, basically one for the pre amp and one for the power section.
In your case use the "earth" lug on the line out jack.
Use a good quality metal line out jack.
You don't have to fit the cap. What it does is bleed away some of the highs.You can also dial in the sound you like by using different value of cap.
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The Pentatonics Reverbnation
Youtube
"Why don't you leave some holes when you play, and maybe some music will fall out".
"It's music,not just complicated noise".
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Kingley
1769 posts
Feb 10, 2012
9:22 AM
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7LimitJI - Thanks for the help. I suspected it might be the chassis, but wanted to make sure before doing anything daft!
I'll try it without the cap and see how I go on. I plan to use one of the extension speaker jack sockets.
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Kingley
1770 posts
Feb 10, 2012
12:40 PM
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I think I've done it right. I haven't tested it through a PA yet though. I ran it into the 8 ohm extension speaker output and also omitted the capacitor as 7LimitJI suggested. Here's a picture of the mod. Sorry it's a little blurry. Hopefully someone can confirm if I've done it right or not.
Last Edited by on Feb 10, 2012 12:42 PM
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tookatooka
2708 posts
Feb 10, 2012
1:58 PM
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Any chance of a clearer pic Kingley? I was trying to check your resistor values. 2.2k red red red bands 470 Ohm Yellow violet brown bands. Is that what you have?
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Kingley
1771 posts
Feb 10, 2012
2:13 PM
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tookatooka - Yes I think so. That's what I ordered anyway. I'll try and take a better picture.
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Kingley
1773 posts
Feb 11, 2012
5:53 AM
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Thanks Arnenym - I've posted over on the Lone Wolf blues forum
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