Ampeg SVT Classic and 610HLF Problem

[amozafari]

Hi there,

I just purchased a used SVT classic and a used 610HLF cab. I'm new to both of these and am not too familiar with how to troubleshoot so any help is much appreciated! The amp is in great shape with new tubes that are about a month old

As soon as I plugged everything in, i noticed a buzzing/hissing noise coming from the top tweeter, after playing around with some settings for a while I turned the High Frequency Horn Control to Infinity and it went away. What exactly is that knob for? Will it cause any problems down the road keep it at that setting? What can I do to have that issue go away all together?

After that problem was fixed I began to hear a humming/buzzing sound coming from the cab. I've tried new instrument cables, and played with the settings. It almost sounds like a synthesizer note being played if that makes sense? I'm a little lost as to how to troubleshoot this one any ideas?

Will using a speakon cable instead of a speaker cable make any difference?

Thanks for taking the time to look, any help is very much appreciated, thanks!

[SB Dog]

Seriously w/o B.S. What type of "speaker" cable are you using? How long have you owned the cable? What gauge wire is it made of?

The reason I ask is that at one point, I had this exact same issue with a V4BAV-SVT. I just assumed my zip cord speaker cable that I had on my Fender BXR 200 and 410 cab was good enough.

It took months of stress and anxiety, a re-tube, and finally, a professional troubleshoot, to find out it was in fact just my speaker cord. Oh, and plus the cost of the new speaker cable. (not cheap, but under $50)

[BigOldHarry]

I call shennanagans on the speaker wire thing. Any decent speaker wire that is NOT SHORTING will work just fine. Sure, I wouldn't 20 gauge home speaker wire for this rig, but decent wire is decent wire - there's no magic here, so long as it is not shorting or intermittant. You're saying that the cab runs fine but you get some odd hiss out of the tweeter? I'm thinking you have another issue...

[SB Dog]

Would it be fair to say try the simple thing first? One may call "shennanagans" out of disbelief or ignorance, but I tell you my friend, your symptoms that you have indicated were exactly what I experienced. That cable, (12 or 14 gauge)was in fact good on my other rig, but did not work on my Ampeg Head.

[billfitzmaurice]

Originally Posted by SB Dog

That zip cable, (12 or 14 gauge)was in fact good for my other rig, but did not work on my Ampeg Head.

There's no reason for that to occur. Copper is copper.
As for the tweeter, it only reproduces whatever the amp sends to it. The amp may need work.

[Jim Campbell]

Originally Posted by BigOldHarry

I call shennanagans on the speaker wire thing. Any decent speaker wire that is NOT SHORTING will work just fine. Sure, I wouldn't 20 gauge home speaker wire for this rig, but decent wire is decent wire - there's no magic here, so long as it is not shorting or intermittant. You're saying that the cab runs fine but you get some odd hiss out of the tweeter? I'm thinking you have another issue...

yeah....maybe the connectors need a looksee tho'....beyond that eliminate the variables and check.....different instrument,instrument cable,head

[SB Dog]

Billfitzmaurice:

One could not agree with you more. That was my exact reasoning on why I used that cable in the first place.

However, electrolysis changes everything. I tested for continuity at the cable ends, I did not see any loose or damaged jacks. I did see signs of corrosion as the zip cable was clear jacketed.

Possibly I had an unnoticed loose connection or intermittant connection at one of the jacks that caused this to occur. I still own the cable, but I have not used it since. I do know for fact I owned that cable for several years prior to using it.
I think I will check it out again.

[billfitzmaurice]

Originally Posted by SB Dog

Possibly I had an unnoticed loose connection or intermittant connection at one of the jacks that caused this to occur. I still own the cable, but I have not used it since. I do know for fact I owned that cable for several years prior to using it.

Corrosion is a possibility, as is a mechanical problem in a plug, even a hair sized section of wire creating an intermittent short. If a cable causes a problem it's defective one way or another, but not because it's zip cord, and an under-gauge cable won't cause noise.

[SB Dog]

Originally Posted by billfitzmaurice

If a cable causes a problem it's defective one way or another, but not because it's zip cord, and an under-gauge cable won't cause noise.

Possibly this is where the communication gap started. I was not indicating that any "zip cable" you use, is necessarily the blame. I was merely inquiring about the description, age, and condition of the particular cable being used, for comparison because that is where my issue with my amp was.

As far as my cable, in addition to the corrosion, possibly the shielding may have split and I was getting interferrance from tube freqs, or whatnot, causing the noise.

I appologize for any miscommunication

[billfitzmaurice]

Originally Posted by SB Dog

As far as my cable, in addition to the corrosion, possibly the shielding may have split

Speaker cables aren't shielded. That does bring up a good point, though, that the OP should make sure his speaker cable is a speaker cable, not an instrument cable. I doubt that there's any way it could cause noise anyway, but still..

Will using a speakon cable instead of a speaker cable make any difference?

With the relatively low power of the SVT no, but using Speakons rather than 1/4" removes the possibility of inadvertently using an instrument cable, so it's a good idea.

[rickdog]

Originally Posted by amozafari

I just purchased a used SVT classic ... new tubes that are about a month old ... As soon as I plugged everything in, i noticed a buzzing/hissing noise coming from the top tweeter ... After that problem was fixed I began to hear a humming/buzzing sound coming from the cab. I've tried new instrument cables, and played with the settings....

The tubes are new, but how old is the amp? If it's old, humming/buzzing could be due to bad power supply capacitors. They tend to go bad with age.

Another possible source of hum is improperly biased output tubes. If the two sides (the "push" and "pull" sets of tubes) are both biased properly (and thus balanced), they tend to cancel out hum in the power supply. When the tubes were replaced, was the amp properly biased? Does it still hum if you turn down all of the volume controls all the way? That would tend to indicate the hum is from the power amp (or preamp stages after the last volume control).

If you turn the High Frequency Horn Control back up (so you hear the hissing) do treble and midrange controls affect how much hiss there is? Tubes (and other components) generate some noise; if it's coming from an early stage in the preamp it gets amplified a lot. These days, tubes just ain't what they used to be, and even a brand new tube could be noisy. Try swapping the preamp tubes around (exchange pairs of tubes of the same type) and see if that affects the noise.

There are lots of SVT and general tube amp experts around here (JimmyM and BassmanPaul will probably have some good advice here by-and-by). Once you learn a little about these amps (beginning with how to avoid electrocuting yourself!), there's really a lot you can do yourself to troubleshoot and service them.

[rickdog]

Originally Posted by billfitzmaurice

... relatively low power of the SVT ...

I got a chuckle out of this... I suppose that's true in this age of $300 1 KW class D power amps... but doggone, 300 tube watts! I have a hard time thinking of an SVT as "low power".

[JimmyM]

Originally Posted by rickdog

I got a chuckle out of this... I suppose that's true in this age of $300 1 KW class D power amps... but doggone, 300 tube watts! I have a hard time thinking of an SVT as "low power".

these kids today...all spoiled by their 2000w power amps.

[SB Dog]

Originally Posted by billfitzmaurice

Speaker cables aren't shielded.

Again my appologies for the incorrect nomenclature. It is certainly not just bare wire. When I refer to "shielded" I refer to the protective coating which surrounds the wire. I guess I should have referred to it as jacketed?

Bill, are you indicating additional noise and corrosion can not be contributing factors of an unprotected wire? Also, in my first post, I was nicely making sure that it was in fact, a speaker cable not an instrument cable.

[billfitzmaurice]

Originally Posted by SB Dog

Bill, are you indicating additional noise and corrosion can not be contributing factors of an unprotected wire? .

Corrosion can be a factor, mainly as it can result in a short circuit between the conductors.