Please. I need clarity concerning my Ampeg SVT CL

I guess the first question is why are you trying to mess with the bias? If it's brand new it has been set for the tubes currently in it prior to shipping.

 

Yeah, hook it up, let it warm up for 15-30 mins, enough so the fan moves room temp air. Start playing on it, the bias LEDs should be green and go red with the volume. If it acts weird then take it too a tech.

Why fix what isn't broken.

 

First, make sure the head is going into a load (cab). You'll blow your amp up if you turn it on and it's not connected to a cabinet.

Second, turn the power on with the amp remaining in standby. Leave it on for at least 30 seconds before flipping off standby. However, when you're setting the bias you want to let it stay in standby for a good 20 minutes or so first before taking it out of standby.

Third, turn off standby and start playing. Look to see what the bias is doing. The green lights should remain green, and the red lights may or may not be flickering (it's cool if they are). If this is what's going on then you're A-okay.

If the lights are red all the time then you need to set the bias. Fortunately, it's really easy. Take a flat head screw driver and turn the dials until the lights turn green.

 

I gotta make this obvious. If it's brand new then it should be set correctly from the factory. It is good for you to understand the procedure for some time several years down the road when you need to set the bias, but right now it shouldn't be your first concern.



Your first concern should be the location of your earplugs, and the proximity of any small animals that may perish from the effects of what you just purchased.

 

"If it ain't broke, don't fix it." If I wrote about all the ways I've learned this, it would be too long to read As FenderAmpeg pointed out, it's brand new. Unless it was badly abused in shipment and something was damaged, it should be biased just fine.

If you want to check the bias, I'll respectfully disagree about warming it up in standby. The heaters (that make the cathodes glow that nice warm orange color) are about 11W of heat per tube (6.3V at 1.6A). The plate dissipation at idle (not standby) is about 15W per tube (650V at 24 mA); but that's zero in standby (no plate voltage), which means the tubes won't be heating up to their normal operating temperature.

And the manual clearly says to check the bias with no input signal present. Yes, the red lights should flicker when you play, but for setting the bias what counts is green with no red when you're not playing.

Finally, yes, never take it off standby unless the speaker is connected!

 

If the head is brand new then they should have already biased it as I am told you only need to bias it when replacing tubes.

Other than that, go to the Ampeg website and go to the SVT-CL, when on the description page scroll down and look on your right hand side for the download for the PDF instruction manual for your head. In the manual it is on page 7/8 and it tells you in detail how to bias it. It tells you everything to look for while you do and even lists everything that can happen when not properly biased and the solution.

 

Let's take this from the top. The manual is a bit confusing.

-Connect the speaker cabinet to the amp.
-Plug in the amp.
-Do not plug in your instrument cable, turn the gain and master fully to the left (minimum), set the tone controls at noon. Setting the pots is not necessary but it sets the amp up in a consistent way for setting the bias. It is just a good practice.
-Put the amp in standby.
-Turn on the power.
-Wait at least 30 seconds for the heaters inside each tube to turn on and heat the tube.
-Turn the standby off. The amp is now in playing mode.
-Let the amp warm up for at least 30 minutes. The idea is to have it in playing mode and to allow all the components to reach a steady state temperature.
-Set the bias as per the manual. Follow the instructions. Once the bias is set, check it again after another 30 minutes. Adjust the bias again if necessary.

From the manual:

Setting Tube Bias
Allow the unit to warm up at proper AC line voltage for at least 20 minutes. With no input signal present, adjust each control so that only the associated green LED is lit. The controls may be slightly interactive. If neither LED is lit, the amp is over biased.This will result in some distortion in the power amp and a generally thin sound. If the green and red LED are lit, the amp is under biased and too much current is flowing to the power tubes. This will give a big, full sound but will also reduce the life of the power tubes. Once set, the controls should not have to be changed except as needed for tube replacement, or to compensate for tube aging. Note that the AC line voltage may vary from place to place and the LEDs will read slightly different. There is no need to fiddle with this every other day. Note that it is nor- mal for the red LEDs to light when there is a signal present. Bias 1 Control adjusts the three left (as seen from the rear) power tubes. Bias 2 Control adjusts the three right power tubes. By observing the LEDs as the Bias Controls are slowly rotated clockwise, a number of tube problems can be diagnosed by the user:

Condition: Green comes on, then red
Problem: No problem
Solution: The longer the green LED is on before the red LED comes on – the better matched the tubes are.

Condition: Red comes on, then green
Problem: Tubes not properly matched
Solution: Set slighty before green comes on, obtain matched tubes when possible.

Condition: Red comes on, no green
Problem: One or more tubes are non-functioning
Solution: Check to make sure tubes are all seated properly; if so, find and replace bad tube(s).

Condition: None on
Problem: Possibly no high voltage or bad Bias Control or bad tube(s)
Solution: Have unit checked by a service technician.

Condition: Both on all the time
Problem: Possible bad Bias Control or bad tubes
Solution: Have unit checked by a service technician.

If the tubes are bad enough to cause damage to the unit, the Fault Indicator (#11, Front Panel) will signal and the unit will shut down.



The bias needs to be checked and set if necessary when you change your power tubes. It will not change if you replace your pre-amp tubes.

As the power tubes age, the required bias can change. So check your bias every four to six months if you use the amp a lot, otherwise every year as part of a general maintenance procedure.

The bias can also change if the wall voltage changes. If you set the bias with a wall voltage of 125 VAC, then go to a different location where the power is 118 VAC, the required bias will change. I'm not saying you need to re-bias the amp whenever you move it. But a different line voltage will affect the optimal bias setting. If you notice that you amp sounds more distorted or sterile from one location to the next, it could be the bias. Just be aware of it. If you don't think that the amp is performing optimally, check the bias.

-Thermal shock shortens tube life. If your amp was out in the cold, let it warm up to room temperature before powering it up. Likewise, allow your amp to cool down before taking it out into the cold.

 

Hey man, take it easy! It's an amp like any other, except it's just way more awesome than any other

SVT's are tanks, and though you shouldn't mistreat them, people wouldn't take them on the road with them as much as they do if they couldn't stand up to it. Plug it in, turn it on, wait 30 seconds and start playing. After a half hour or so, check the bias if you must. Chances are it'll be just fine. And for God's sake, don't turn into one of these retubing nuts! Only change tubes when they break on you, and only replace the broken one.

 

I love solid state.

 

Munji, you're a lot older than I am, and I know of no good way to say this so I'll just be blunt...Do you really want to die knowing that you could have had an SVT and never got one? Don't you want to spend your declining years with the very best tone known to man?

 

Having nothing productive to add to this thread , I will contribute this much.

Daaaaaaaaammmmn Jimmy.

 

Sure. I still have the DB750 in my arsenal, so I'm good.

 

BTW, the DB750 has a Telefunken ECC83 in V1 and a Siemens 12AU7 in V4 with JJs everywhere else.

 

Ya know, there's guys that endorse a product, and then there's guys that stand on the corner and push it... Jimmy, you wouldn't sell any Ampeg to grade school kids would you?

 

HAHAHA! I just like doing that to Munji because it's fun To be honest, I'm not much younger, either.

 

Rehab is going to cost for this guy....

 

Oh, that kid is done for! You sat him on an SVT and it's all over...you've consigned him to a life of moving a 250 lb rig.



Cute as all getout!

 

^^^ I love it - another bass hero in the making.