#1
I have a Peavey Max bass 450, i'm grabbing the same head later with 700 watts instead of 450 and it has all the same features - but I have a question or two about the built in DDT Speaker protection function on these amps.

On my 450, I have a old peavey cab with 12 inch Sheffields. The cab is rated something around 400 watts at 2 ohms. When my DDT speaker protection is enabled, I can push this amps gain at about 12:00 and its master at about 3:00 when that DDT speaker protection light turns from yellow to red - however it only turns red as im playing deep notes. This seems fairly normal to me, and was to be expected. Im running a 450 watt head into a 400 watt cab, of course I can't push it to the max. I'm gonna wire this cab to 8ohms instead of 2, but thats for later

My real problem is this however, i grabbed a GK cab that is rated 200 watts at 8ohms. my 450 watt amp runs about 170 watts into this cab at 8ohms - but I have the same exact problem. If this cab can handle 200 watts, why does my DDT speaker protection display show that im damaging the speakers when I'm only running at about 12:00 volume?

I did read the manual that came with my head, but it didnt really help much. It just said what the DDT protection is, and that it should always be enabled. My problem is that the cabs sound GOOD when pushed just a little past where they are suppose to - I don't really want to damage the speakers but I need that extra boost of volume when my band practices. Could anyone enlighten my as to why it works this way, or maybe i'm not using it right?
Treble>Epiphone Prophecy EX - MXR micro Amp - MXR Blue Box - MXR Fullbore - MXR Noise Clamp - Vox AD30VT
Bass>Ibanez BTB505 - MXR Blowtorch - MXR D.I. - Peavey MaxBass 700 - Peavey TVX410
#2
DDT is not for speaker protection. It;s for preventing preamp and poweramp clipping.

Its a compressor/limiter that kicks in once you hit the full output for the amp. At what point you hit it depends on your gain settings and how hot your input signal is.

If the DDT light is on, but your getting sound, it basically means that the compressor is preventing clipping.

If there is a risk of damaging the amp, the limiter kicks in and shuts off the poweramp stage.

My Peavey KB4 has DDT and it does the exact same thing that you are describing. Its normal.

In laymans terms, red light is ok. If things get hairy, amp switches off.

SS amps are not like tube amps. Once they hit the max rated output, they start clipping. The point at which the red light goes on is the point where the amp is pushing its full power. The fact that it happens when you paly depper notes on the lower strings proves it- those strings are much thicker, hence your input signal is hotter, hence the poweramp is driven harder, and you bump against the power ceiling. Same thing happens when my bands bassist decides to do slap and pop while connected to my amp. Only, it shuts off instead of just red light glowing
Last edited by GS LEAD 5 at Feb 28, 2012,
#3
Thanks for your reply, pretty insightful. So what your saying is, if the speakers are being damaged by my playing and my EQ, then the amp will just cut the input if DDT is enabled? Otherwise, good to go?
Treble>Epiphone Prophecy EX - MXR micro Amp - MXR Blue Box - MXR Fullbore - MXR Noise Clamp - Vox AD30VT
Bass>Ibanez BTB505 - MXR Blowtorch - MXR D.I. - Peavey MaxBass 700 - Peavey TVX410
#4
Leave the speakers out of it. This has nothing to do with the speakers. (At least not in the way you are thinking. But, forget them for now, you're confusing the issue)

The amp has no way of knowing what speakers you have connected - it's just reporting how much power the amp is trying to push, and how much power it has left to give. When you use a less efficient speaker setup, it makes sense that you reach that power threshold earlier, since you have to push the amp harder to get the same volume.
#5
Quote by Vypor
Thanks for your reply, pretty insightful. So what your saying is, if the speakers are being damaged by my playing and my EQ, then the amp will just cut the input if DDT is enabled? Otherwise, good to go?


Re read my post. DDT is NOT speaker related tech. It simply compresses the signal when your amp's pre/poweramp clips, and cuts the signal completely if the compressor cant cope. It has nothing to do with the speaker. Stick to the 400W speaker you had earlier- if the red light was on then the amp was pushing all 450W. If you didnt hear the speaker break up (a buzzy, fuzzy kind of sound) then the speaker is probably rated very conservatively.
#6
I understand now, thanks for the help. I hope you surely can understand my confusion however, the label under the light does read "DDT speaker protection" - and I did get different results with the GK 2x10 then I did with the Peavey 4x12.

Also, if the red light only comes on when I'm pushing the full 450 watts my head can output - then why does the red light come on when I'm only pushing 170 watts into 8 ohms?

Really, not even that because the amp isn't even anywhere close to maxed out.
Treble>Epiphone Prophecy EX - MXR micro Amp - MXR Blue Box - MXR Fullbore - MXR Noise Clamp - Vox AD30VT
Bass>Ibanez BTB505 - MXR Blowtorch - MXR D.I. - Peavey MaxBass 700 - Peavey TVX410
Last edited by Vypor at Feb 28, 2012,
#7
It protects your speakers in the same way the headlights on your car protect the groceries in your back seat.

That is to say, indirectly. DDT just keeps the amp from trying to put out more power than it is rated for. It isn't actually actively protecting the speakers. There is no way for the DDT to "know" what wattage speakers you're using. It just assumes you're using ones rated for exactly the amp's rated output. The lights are coming on because of the impedance of the cab, not the wattage rating. If you had a 10,000 watt cab that was 8 ohms, the light would come on at the exact same time.

That's what you're missing. 170 watts is maxed out for your amp at 8 ohms. More impedance = less power. The amp is working just as hard to produce 170 at 8 ohms as it is to produce 400 at 2 ohms - actually, probably even harder due to lower efficiency.

The volume knob position is largely irrelevant, and misleading. Most amps hit their rated wattage way before the knob is at 10. Many tube amps will hit their advertised output somewhere around 4.