SVP Pro Preamp

Rig talk.

Re: SVP Pro Preamp

Postby Mr. Mom » Thu Sep 18, 2014 5:23 am

Passinwind wrote:I had one in here for repairs and a few mods last spring. Came out nice and the owner uses it as his daily driver.


Just curious as to what mods you did?

The seller I purchased this from changed put some Groovetubes in mine in place of the stock tubes. Not being a tube guy, I have no idea if that's good or bad! Sounded good to me! [smilie=smilie_kopf.gif]

I am really digging this thing in my basement practice space. Even like the graphic EQ to tame the bottom end. It's definitely an Ampeg product!!
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Re: SVP Pro Preamp

Postby Passinwind » Thu Sep 18, 2014 10:37 am

Just curious as to what mods you did?


Some cleanup from some other "tech" 's work on the main ribbon cable, and I also reverted the front end design to whichever SVT II variant it was originally based on. The owner had to use the input pad at all times, now he can comfortably use the regular input setting too. I also boosted DI gain and tweaked the clipping indicator circuit so that when it flashes it might mean something. This was one of the series that had noise issues with the steel lid being so close to the transformer, so we had a custom aluminium one fabricated. Rolled lots of different tubes too -- in a couple of slots that can make quite a difference. It came out great, I'd hit it.

This particular one was basically a basket case, and I took it on as a winter project for a friend, and tried to learn a lot about a completely different design philosophy than what I typically roll with. These things are not all that easy or fun to work on, so if it ain't broke... [smilie=cool-smiley-027.gif]
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Re: SVP Pro Preamp

Postby Mr. Mom » Thu Sep 18, 2014 11:29 am

Passinwind wrote:...so if it ain't broke... [smilie=cool-smiley-027.gif]


That's my motto!

Mine does not seem to buzz. I read that tube swapping can cure that buzz, too. We'll see this weekend how it performs.
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Re: SVP Pro Preamp

Postby Passinwind » Sat Sep 20, 2014 9:25 am

Tube buzz and mechanical buzz were/are two different potential issues with that design. My friend's SVP suffered from both. I went through my old parts stash and found one or two winners, but most of the rest are new stock Tung-Sol and JJ. I really like the current Tung-Sol 12AX7s, especially in Fenders.
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Location: Columbia River Gorge, WA.

Re: SVP Pro Preamp

Postby Mr. Mom » Mon Sep 22, 2014 10:27 am

Passinwind wrote:Tube buzz and mechanical buzz were/are two different potential issues with that design. My friend's SVP suffered from both. I went through my old parts stash and found one or two winners, but most of the rest are new stock Tung-Sol and JJ. I really like the current Tung-Sol 12AX7s, especially in Fenders.


Good bits of info to know. Thanks, PW!

Verdict is in: Love it!! Nice tone with everything set flat and the Drive at about 3:00 pm. Plenty of the tubey warmth with nice compression and just a smidgeon of dirt. And yes. I said "smidgeon".
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