Ampeg svt issue

[jonday30]

I picked up this svt AV head probably 3 months ago. I didn’t have the matching 810 cabinet but I do have a Traynor 810 cabinet.

So after 3 months the jam space is finished and I’m able to crank this thing. A little disappointed really. Running the EQ flat, both hi/low buttons in, master cranked and the gain at about 3(9 o’clock) most of not all low end notes are distorted.

I thought maybe I had the amp a little too close to the corner of the room. It’s now in the middle of the room and the low notes just distort. I can put my ear to all speakers hit open E or F on the E string and it’s just farty.

What would it be? The Traynor and svt are both 300 watts.

 

[Dave W]

Leave the hi/lo buttons out. You’re scooping the mids and pushing a ton of low end into the cabinet.

If that doesn’t fix it or at least help out I’d be more inclined the think your have a Traynor 810 problem rather than an Ampeg SVT problem, unless you’ve got another amp that’s running through it just fine.

 

[jonday30]

I traded in the Traynor yba300 for this head and didn’t notice the low end/higher volume speaker crackle before. Basically the exact same EQ settings, with high/low buttons pushed in. The yba300 and this svt are almost identical with the EQ setup.

I did turn off the high and low switches and it is better. Still once the volume goes up the noise is still there. Maybe this svt just pounds a little harder.

 

[beans-on-toast]

If this is a vintage Traynor 810, the Marshland speakers were not that great. If it is a TC810 you should be fine with the SVT. In general, a cabinet needs a higher RMS wattage rating than the amplifier. For instance, the SVT is rated at 300W RMS, the SVT-810E is rated 800W RMS. That’s considered a good match.

First, as suggested, you need to try the amp with another cab to rule out the distortion coming from the amp. When the amp is pushed, you could be hearing crossover distortion related to the bias setting of the power tubes. A tech can check this out with a signal generator, dummy load, and a scope.

Otherwise, you could be distorting the speakers when you hear a crackle. This can damage them. It could be that the Ampeg is pushing harder. Turn down the volume or the bass eq and see if it helps.

 

[jonday30]

Yes it’s the TC810 cabinet rated for 1600 watts. It should be ok with the svt. I did turn down the volume and adjust the EQ which definitely helps. Still I’d like to get this sorted out so I can run this beast at higher volumes.

I’m on the hunt for a ampeg 810AV cabinet but looking for used which is a tough one.

 

[beans-on-toast]

I should add, check the bias with the LED’s on the back of the SVT as per the manual. The amp should be warmed up before the bias is set, play through it for a half hour first.

 

[jonday30]

I’ll actually give that a try. I did set the bias as per the manual but I’m going to try it as you said. Get it hot first and then set it. It may be set a little too hot causing the amp to push the speakers hard.

 

[beans-on-toast]

I’ll actually give that a try. I did set the bias as per the manual but I’m going to try it as you said. Get it hot first and then set it. It may be set a little too hot causing the amp to push the speakers hard.

Too hot will cause the crossover distortion that I mentioned.

Warm the amp up, be consistent with your settings: unplug your bass, turn down the volumes, set tones at noon. Set the bias by always turning the pot clockwise. If you overshoot turn it down and go up clockwise to where you want to set it. Do not leave it set with the red LED on.

What the lights do when you are playing is of no concern. What’s important is how they read with the amp warmed up (in playing mode, not just in standby) and at idle (no input).

It goes without saying that the amp needs 6 well matched power tubes.

 

[Funk With Me]

I was going to suggest that maybe a power tube or two might just be old and ready for replacement.

 

[beans-on-toast]

I was going to suggest that maybe a power tube or two might just be old and ready for replacement.

It could be internal tube arcing when the amp is pushed. There are many other possibilities but you have to start with the simplest stuff to resolve first.

 

[Funk With Me]

Not necessarily arcing, just old and worn out if it’s a used amp. I bought one new, and after a few years of pretty hard gigging the amp got weak. Any attempt at compensating with the volume control resulted in distortion. Took it to a tech. Turned out the power tubes were just plain old used up.

 

[jonday30]

I’m going to bias the amp tomorrow. It’s too late tonight to give it a go. It’s definitely possible that it could be a weak tube. It sounds great but only when pushed is when it starts to distort.

 

[jonday30]

Would these be the stock tubes for this svt-av? Svetlana 6550c

 

[andy67]

I had this very issue with my SVT Classic, only difference was, that the classic would distort and then lose volume. Turned out to be one faulty power valve. Once replaced and re-biased, worked perfectly.

 

[JimmyM]

Tough to diagnose things like this over the net, but I would be looking for a faulty power tube, too. If not that, check your preamp tubes.

 

[JeezyMcNuggles]

I picked up this svt AV head probably 3 months ago. I didn’t have the matching 810 cabinet but I do have a Traynor 810 cabinet.

So after 3 months the jam space is finished and I’m able to crank this thing. A little disappointed really. Running the EQ flat, both hi/low buttons in, master cranked and the gain at about 3(9 o’clock) most of not all low end notes are distorted.

I thought maybe I had the amp a little too close to the corner of the room. It’s now in the middle of the room and the low notes just distort. I can put my ear to all speakers hit open E or F on the E string and it’s just farty.

What would it be? The Traynor and svt are both 300 watts.

Yeah, it's distorting. That's what happens when you crank tube amps. Especially with the ultra low on. I'm really surprised that you still have speakers.

Put the amp knobs straight up, switches off, and play. Does it still do that?

 

[jonday30]

Yeah, it's distorting. That's what happens when you crank tube amps. Especially with the ultra low on. I'm really surprised that you still have speakers.

Put the amp knobs straight up, switches off, and play. Does it still do that?

I know how tubes work and this amp is by no means cranked. This is not my first svt or tube amp for that matter.

With switches out and EQ set flat, no it doesn’t do it. However the tone of after is not in that range of settings. So that’s why I want it sorted out. Tonight I’ll bias the amp again and look into power tubes.

 

[Plain Old Barry]

It's been a long time since I had an SVT, but I don't remember the controls being linear, same with many other tube amps of the day. 3 on the input wasn't 1/4 volume on mine, it was probably more than 1/2, and part of the equation is output of the bass and/or pedals. Since your master is dimed, the amp may be nearly maxed out and distorting all by itself.

 

[jonday30]

That’s really weird then. Maxing the master and using the gain as my overall volume, it being at 3(9 o’clock) with EQ flat it’s almost maxed for power. That doesn’t seem right to me. What happens when you play a stadium and need more clean headroom?

 

[Plain Old Barry]

That’s really weird then. Maxing the master and using the gain as my overall volume, it being at 3(9 o’clock) with EQ flat it’s almost maxed for power. That doesn’t seem right to me. What happens when you play a stadium and need more clean headroom?

I'm not saying it's definitely your problem, but the gain and master on so many tube amps of that day were maxed well before 10 on 0-10 knobs. After a certain point, there was very little change. Again, the signal level of your bass or pedals also is part of the overall equation. Even solid state stuff, like Acoustic or Lab Series, had a certain non-linear reaction, but it wasn't as pronounced as the tube stuff I remember using.

As for your question, you'd DI into a PA or add more amps. Multiple SVT's were not unusual to see in the 70's and 80's on arena stages.

If you're looking for a current hi-fi sound at loud volumes, you may have the wrong amp.