Another SVT 4 Pro Topic

[dr9]

This amp should probably have it's own subforum. I've been reading here and elsewhere for hours this morning and last night, and still have a couple of questions that, hopefully, some of you gurus can help me out with.

I sold an SVT-4 Pro on CL to a gentleman an hour and a half away. I never really used it much, I'm not a bass player and I inherited it from a deceased family member years ago.

He's emailing me now with problems. He says the sound is low and slightly distorted. He's running in stereo with two 4-10s. He says there is no difference in sound between A channel and B channel. I chalk up the low volume to him not bridging mono with correct speakon and cab wiring.

I can't figure out the distorting problem though. In my limited use with this amp, it was used direct for recording with zero issues, actually sounded awesome, and is worth $600 just for that capability in my opinion. However, whenever I played it through the HLF410, I never really cranked the volume and thus never noticed an issue, so there could have been an issue that I simply wan't aware of.

So, the buyer is thinking/hoping it's just the preamp tubes that need to be changed, I also hope that's the issue, but something tells me, based on reading here and elsewhere for the last 24 hours, it might be a bigger problem and I'm going to have to end up buying this back from the guy and driving 1.5 hours one-way to get it.

I've asked him to run it 1/4 direct to a recording device or stereo to see if the sound is still distorty, and report back. I assume if the sound is still crappy, it is indeed just a tube problem and not something more serious. Am I correct in this assumption?

I appreciate any info you can give me. Again, I created an account here because this forum seems to have the most informed responses to the issue from google searches.

[audiomitch]

Tell him to insert a cable between the effects send and return jacks. If the distortion goes away it's a dirty switch.

I'm not sure about a SVT-4 Pro, but in the SVT-3 Pro the mosfets sometimes need to be biased. A lot of people eliminated their distortion problems by adjusting the bias to spec.

Good luck, and this is the right place to get answers.

[tbird36go]

The dude is running it wrong! Tell him to go here... http://www.ampeg.com/products/pro/svt4pro/index.html & click on "download the manual". To run 2-410 cabs stereo he needs an effects processor & 2 input cables. The SVT-4 PRO’s two internal power amplifiers will each power a set of full range cabinets in stereo:
Set the Stereo/Mono Bridge switch OUT (Stereo position) and connect the system as follows:
1: Connect a shielded cable from the Effects Send of the SVT-4 PRO to the Input of a Stereo Effects Processor.
2: Connect a shielded cable from the Left Output of the Processor to the SVT-4 PRO’s Effects Return Left / B jack.
3: Connect a shielded cable from the Right Output of the Processor to the SVT-4 PRO’s Effects Return Right / Ajack.
4: Connect a speaker cable from the SVT-4 PRO’s Power Amp ASpeaker Output jack to the input jack(s) of the Stage Left speakers.
5: Connect a speaker cable from the SVT-4 PRO’s Power Amp B Speaker Output jack to the input jack(s) of the Stage Right speakers.
For Speakon® connectors pin 1+ = “+”, pin 1– = “–”. The manuals page 12 & 13 have all the hook up diagrams.