Possible Amp Block Bug (Ultra v11): Tube Pre/Active Tone Stack Loses Bottom End.

[DJD100]

Hi all, I wonder if anyone else sees this?

Using the Tube Pre with it's Tonestack set to Active rolls off the low end (all setting @ 5, power amp on, Low Cut and LF Xformer at minimum). I believe the Tube Pre uses the Vintage Tonestack which is also light on the bottom end? I was hoping that using the Tube Pre with an Active Tonestack would be flat response but this doesn't seem to be the case. Is this an Active Tonestack bug, or just a symptom of the underlying Vintage Tonestack, or...???

I realize that many likely don't use the power amp sim with the Tube Pre as it's off by default, but is there any chance of getting a flat response Tube Pre with the power amp sim on Cliff (it makes for a great power amp sim for external preamps etc)?

Thanks...

 

[Jens]

I guess if you want flat response you might just as well use a filter to boost the signal and maybe a slight compression?

The tube pre-amp is probably designed not to be flat response, because then it would just be a compressor?

Jens

 

[Rex]

AFAIK, the Tube Pre is designed to model the Presonus TubePRE mic preamp. It's not guitar gear. The original has no tone controls at all. The block's passive tone controls already cover more sonic ground than the original. If you need more control over bass/mid/treble, add a PEQ or GEQ in front of or behind it.

 

[DJD100]

Hmmm, then in that case it should be flat response at least in the freq range of electric guitar?

By using the Active Tonestack I should be bypassing and tone altering with the levels at 5, but it still rolls off the bottom end unlike a generic recording pre which is what I thought it was trying to be?

I use it for a flat power amp sim with external guitar preamps, so what I need is it to be flat with the tone controls set at 5 in active mode etc.

Yes, some EQ can compensate though it shouldn't be needed if I'm understanding correctly (supposedly a flat recording pre etc)?

IMO it should have no tone stack rather than using the low end challenged Vintage Tonestack. I did try all the other tonestacks though and they're all way more colored in the mids, which is likely why Cliff used the Vintage Tonestack in the first place?

Thanks...

AFAIK, the Tube Pre is designed to model the Presonus TubePRE mic preamp. It's not guitar gear. The original has no tone controls at all. The block's passive tone controls already cover more sonic ground than the original. If you need more control over bass/mid/treble, add a PEQ or GEQ in front of or behind it.

 

[Jens]

Hi all, I wonder if anyone else sees this?

Using the Tube Pre with it's Tonestack set to Active rolls off the low end (all setting @ 5, power amp on, Low Cut and LF Xformer at minimum). I believe the Tube Pre uses the Vintage Tonestack which is also light on the bottom end? I was hoping that using the Tube Pre with an Active Tonestack would be flat response but this doesn't seem to be the case. Is this an Active Tonestack bug, or just a symptom of the underlying Vintage Tonestack, or...???

I realize that many likely don't use the power amp sim with the Tube Pre as it's off by default, but is there any chance of getting a flat response Tube Pre with the power amp sim on Cliff (it makes for a great power amp sim for external preamps etc)?

Thanks...

I am wondering about these things:

1. What you want the amp to do if it is not suposed to color what goes through it?

2. What do you mean that the power amp sim is off be default in the Tube pre-amp? Sag is not at 0 and there are also positive values on warmth and damp.

It is not meant as a critique I just want to understand what you are looking for. I recently played an ada mp-1 through the axe only using a cab block and that sounded great! I did not feel the need to
add a power-amp to it.

Jens

 

[Rex]

You can simulate "no tone controls at all" with the passive tone stack by putting Bass, Mid and Treble controls straight up. That should make it pretty flat. I'm not sure why the active tone stack at "0" would be any different. "Active and "passive" tone stacks have no meaning with this model, because the original has no tone stack at all.

You can use it as a power amp sim (might sound great). The original has no power amp.

 

[DJD100]

In theory there is no "flat" with a passive tone stack due to the interaction of the controls. In theory there is a flat with active EQ with the controls centered or zeroed, though in this case it appears the Active tonestack is an active version of the passive, so it's overall curve applies even when set to active and zeroed out.

The Tube Pre appears to use the Vintage Tonestack as there are tone controls, and according to someone here it nulls out with another instance of itself if flipped out of phase etc (one using default, the other vintage).

In this case Tube Pre doesn't appear to have anything in common with the Prosonus pre you mentioned?

The Tube Pre does sound great as a generic tube power amp sim when you turn on the power amp (it's off by default), and the default tone stack is the flattest of the available options by far, though it does roll of the low end way too much which I personally wish it wouldn't (though you can of course compensate with EQ and Depth, Warmth, High Pass, Thump etc).

Thanks...

You can simulate "no tone controls at all" with the passive tone stack by putting Bass, Mid and Treble controls straight up. That should make it pretty flat. I'm not sure why the active tone stack at "0" would be any different. "Active and "passive" tone stacks have no meaning with this model, because the original has no tone stack at all.

You can use it as a power amp sim (might sound great). The original has no power amp.

 

[DJD100]

I am wondering about these things:

1. What you want the amp to do if it is not supposed to color what goes through it?

Color yes, roll of at 330Hz or higher no.

2. What do you mean that the power amp sim is off be default in the Tube pre-amp? Sag is not at 0 and there are also positive values on warmth and damp.

In my rig, if I select Tube Pre for amp type from within the Amp Block (not a preset), then it defaults with the power amp sim off (Sag 0)?

It is not meant as a critique I just want to understand what you are looking for. I recently played an ada mp-1 through the axe only using a cab block and that sounded great! I did not feel the need to
add a power-amp to it.

I know, and thank you for the response!

The power tube/output transformer/speaker combination imparts a dynamic EQ curve which I find critical personally (as well as distortion and compression). It actually works quite well with my external preamps aside from having the low end roll off way to early, and that can be compensated for with EQ (and the advanced params, Depth, Warmth, rthump, High Pass etc), though ideally IMO the Tube Pre should be relatively full range as is any generic recording pre etc.

Thanks...

Jens[/QUOTE]

 

[Rex]

You're right: there is no "flat" response with a passive tone stack. But if the original has no tone control at all, any tone control you like can be crafted with code. What EQ changes are you hearing when you run with the passive stack and the controls set at noon?

I know you don't think there's a resemblance to the Presonus preamp of the same name, but outside of adding tone controls and the capability of power amp simulation. I don't see much difference. Especially when you consider that the sim defaults to sag=0.

 

[DJD100]

The Tube Pre's passive and active tonestacks actually sound quite similar with all controls at 12:00 (power amp on or off).

The difference vs the Presounus Pre is that the Tube Pre rolls off the low end way to quickly for a recording channel (with the power amp on or off), and the Presonus Pre most assuredly wouldn't do that because if it did it would be useless for many recording needs (though a switchable high-pass would be welcome etc).

I'm thinking the Tube Pre is merely a low gain guitar pre using the Vintage tonestack defaulting to 500Hz, one which defaults with the power amp sim off, and is not a recording pre sim at all though hopefully Cliff or someone will chime in with the facts?

Thanks...

You're right: there is no "flat" response with a passive tone stack. But if the original has no tone control at all, any tone control you like can be crafted with code. What EQ changes are you hearing when you run with the passive stack and the controls set at noon?

I know you don't think there's a resemblance to the Presonus preamp of the same name, but outside of adding tone controls and the capability of power amp simulation. I don't see much difference. Especially when you consider that the sim defaults to sag=0.

 

[Bakerman]

Here's the reason for some confusion about settings: defaulting the entire amp block doesn't set it to the actual defaults for Tube Pre. Only choosing Tube Pre w/ the type knob gives zero damp/sag/warmth, passive tonestack.

DJD100, could you describe more about how you noticed this rolloff, or post a preset? I checked with sine sweeps and guitar through a few different drive/master/sag settings, active & passive tonestack, and none of them caused a significant low end rolloff. From 100 toward 40 Hz with the sine sweeps there was a 1 dB drop at most, very flat from 100 up.

 

[JJunkie]

white noise -> Tube Pre with changing tonestacks

Tube Pre in default, except drive, which I set at 5 (no presence, since I'm not sure if the presence frequency is switched when changing the tonestack, or if it is amp dependent)

(the spikes at appr. 1.1kHz, 3,1kHz & 6.1kHz are generated by the white noise block)

the white lines from left to right are 50Hz, 100Hz, 200Hz, 500Hz, 1kHz, 2kHz, 5kHz, 10kHz

bypass (white noise only)

Tube Pre passive (which ironically is also 'active')

fwiw

 

[DJD100]

Thanks Bakerman and JJunkie, much appreciated! My mistake (actually a impedance mismatch between the Axe's loop and my custom tube pre's I now believe, DOH!).

The Axe's Tube Pre is fine.

Apologies all...

Here's the reason for some confusion about settings: defaulting the entire amp block doesn't set it to the actual defaults for Tube Pre. Only choosing Tube Pre w/ the type knob gives zero damp/sag/warmth, passive tonestack.

DJD100, could you describe more about how you noticed this rolloff, or post a preset? I checked with sine sweeps and guitar through a few different drive/master/sag settings, active & passive tonestack, and none of them caused a significant low end rolloff. From 100 toward 40 Hz with the sine sweeps there was a 1 dB drop at most, very flat from 100 up.