Modulus + GK = fart? - Page 2

christw · #21 01-07-2013, 11:13 AM

It's worth noting that as you turn your volume knob it is not a linear extension of the amp's power. How far you turn that knob to get max power depends on what you're using. With a hot signal I run out of headroom around 4/10 pre and 3/10 master on some of my amps. Is the GK louder than the EBS before distortion's onset?

1958Bassman · #22 01-07-2013, 11:16 AM

Quote:

Originally Posted by murphy

Very funny analogy

Jumping on a mattress? It seems to work pretty well but I don't remember where I heard it- must have been well over 30 years ago. I also heard power supply voltage compared to a clothes line and the easy way to add support (stiffen) to it is by adding clothes poles at the right places (filter capacitance) because when more load is added, it sags. That works if the voltage is low- otherwise, higher tension (voltage) can be used to keep it from being a problem.

Then, there are the analogies to water pressure and flow rate.....

BassmanPaul · #23 01-07-2013, 12:27 PM

Quote:

Originally Posted by Axxis

When I'm just playing the E string while turning the volume up on the amp, the sound is good to 9 o`clock, but as soon as I go past that the volume stays the same all the way to full twist on the knob, but the distortion gets worse. So the volume won't get any louder than to 9 O`clock.

This strikes me as atypical of a speaker system running out of excursion. Once the excursion limit is reached adding more power will gain you nothing but more distortion and heat. you have to remember that usually cabinet power ratings are thermal and a typical driver will run out of excursion at about half that figure.

I cannot imagine how loud you are looking to be if four twelve inch speakers are not enough!

foderaman · #24 01-07-2013, 12:38 PM

It sounds like your pre in the bass is causing the Amp Pre to clip.Try downing the volume down on the bass it self to about 3/4 volume then adjust your pre according and then turn up your volume on amp to the volume you need. Try this and see if its better.If there is a trimpot internally in your Modulus try cutting back on it.It is a little blue trimpot with a little adjustable pot in it.Turn it counterclockwise a little.

Kenner · #25 01-07-2013, 05:27 PM

Quote:

Originally Posted by foderaman

It sounds like your pre in the bass is causing the Amp Pre to clip.Try downing the volume down on the bass it self to about 3/4 volume then adjust your pre according and then turn up your volume on amp to the volume you need. Try this and see if its better.If there is a trimpot internally in your Modulus try cutting back on it.It is a little blue trimpot with a little adjustable pot in it.Turn it counterclockwise a little.

+1 ....didn't even think of that...I did that with both my Alembics...it dialed right in after that. I did it originally to avoid have to use the -10db pressed in...it sounded a bit suppressed with it pushed in.

1958Bassman · #26 01-07-2013, 05:33 PM

Quote:

Originally Posted by BassmanPaul

This strikes me as atypical of a speaker system running out of excursion. Once the excursion limit is reached adding more power will gain you nothing but more distortion and heat. you have to remember that usually cabinet power ratings are thermal and a typical driver will run out of excursion at about half that figure.

I cannot imagine how loud you are looking to be if four twelve inch speakers are not enough!

In a sealed cabinet, maybe it will hit its excursion limit but in a vented cabinet, once the signal goes below the port tuning frequency, there's not a whole lot of damping, if any. I have seen woofers that were extremely well-behaved within it's allowable range and once the noes go lower, it gets downright un-ruly.

SunnBass · #27 01-07-2013, 05:53 PM

Quote:

Originally Posted by B-string

I suppose you could have damaged the FETs in the input with the Flea 4. There is no way to prevent (on the amp head) a overly hot signal from hitting the front end.

I'd be willing to bet this is it 100%.
I recently had a brand new 700RB II do the exact same thing to me.
A question to the OP: Is it an immediate fart, or is it kind of like: noooote...fart?
Is the fart about half a second behind the note?

By the way, the "woofer" knob is actually your main/master volume. The one near the input that actually says volume is your input stage, you'll never really want that past, oh say...noon-ish.

Axxis · #28 01-08-2013, 09:12 AM

Too all you people who is saying its the Modulus, how come I get the exact same sound with my passive Jazz bass?

FretFree · #29 01-08-2013, 09:23 AM

Is it being caused by vibration? Is the GK sitting on top of the cabinet? Maybe try isolating it and/or try another (more similar) head.

NWB · #30 01-08-2013, 12:13 PM

Quote:

Originally Posted by FretFree

Is it being caused by vibration? Is the GK sitting on top of the cabinet? Maybe try isolating it and/or try another (more similar) head.

He did that with an EBS amp and didn't get the fart.

He still got the fart with a passive J.

The problem seems to have been reduced to the head itself.

Axxis · #31 01-08-2013, 12:31 PM

Quote:

Originally Posted by NWB

He did that with an EBS amp and didn't get the fart.

He still got the fart with a passive J.

The problem seems to have been reduced to the head itself.

Yes. Think I have to see a tech and have him look at it. However, it became a tiny bit better when having woofer higher than volume. Still havent tried with the modulus.

NWB · #32 01-08-2013, 01:02 PM

Quote:

Originally Posted by Axxis

Yes. Think I have to see a tech and have him look at it. However, it became a tiny bit better when having woofer higher than volume. Still havent tried with the modulus.

Since the "woofer" acts as the master volume on that amp, I'd certainly try backing the "volume" (gain) way back, around 9 O' clock perhaps, and upping the woofer level.

ivbenaplayin · #33 01-08-2013, 01:32 PM

after reading through this thread, (and being a GK owner that uses several basses with 18v preamps) it does kind of sound like your Modulus is overdriving your amp's input stage... do you own/use any type of compression device?

NWB · #34 01-08-2013, 01:43 PM

Quote:

Originally Posted by ivbenaplayin

after reading through this thread, (and being a GK owner that uses several basses with 18v preamps) it does kind of sound like your Modulus is overdriving your amp's input stage... do you own/use any type of compression device?

Eh, did you happen to read post #28?

ivbenaplayin · #35 01-08-2013, 01:47 PM

Quote:

Originally Posted by NWB

Eh, did you happen to read post #28?

evidently skipped over that one...
if the input stage isn't being overdriven, then it sounds like it's tech time... hopefully for the OP it isn't something expensive

1958Bassman · #36 01-08-2013, 07:01 PM

Quote:

Originally Posted by NWB

He did that with an EBS amp and didn't get the fart.

He still got the fart with a passive J.

The problem seems to have been reduced to the head itself.

But the GK is over twice the power of the EBS, right? The speaker may be rated for a certain amount of power, but making it work in a smaller than ideal cabinet reduces its power handling capability- sometimes by a large margin. I contacted Eminence about the Delta 12LFA because I want a 12" that would work at home and be better than my Altec 417B. The tech rep modeled it in Bass Box Pro (well, the Emnence software was designed by Wayne Harris, who also developed Bass Bpx Pro, the old TermPro and the graphics are the same)- the speaker is rated for 500W RMS but in the 2.15ft³ cabinet I asked about, its mechanical limit is 150W. In a larger cabinet, it would handle the full 500W. Add the 18dB boost at 40Hz, the speakers are bound to puke.