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dave_bass5

Question about using GK MB800 power stage only.

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Last night i had a rehearsal with the above amp and my new F112 cab. I was running my Helix Stomp in to the return of the amp. Tone wise it was a bit lacking but volume wise it was very quiet. I had the master very high and was still struggling to keep up with the drummer.

I ended up plugging in to the front input and had the full volume back. Lowered the master from 1 'o clock to around 9, and the same setting no the input. Please ignore the settings here, im just explaining how the volume jumped and not questioning where the knobs were set.

My question is, is this a GK thing or should i expect this with any amp? What am i missing here?

It seemed to me the power stage needs a lot of power to drive it. EQ was all at 12 (im not saying neutral). I know GK suggest turning the master right up and adjusting the volume with the input stage, but it just seemed strange that i was hardly getting any power out of it. Helix was set to instrument out and the volume level was pretty much what ive been getting when not using it

 

Edited by dave_bass5

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1 hour ago, dave_bass5 said:

... Helix was set to instrument out and the volume level was pretty much what ive been getting when not using it

 

Try setting to output to "line" level? (assuming that you can on one of those)

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Thanks but my question isnt really about the Helix, its about why the drop in power and is it normal. if i was using normal floor effects the result would be the same.

Im wondering if i needed to have Gain 2 level up (its always kept low). Im not good at reading diagrams but the one in the GK manual looks to me like the signal comes in before level 2.

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I think @nilebodgers is on the right track.  If the GK send/return loop is at line level,  your Helix (or anything you plug into the return socket) should also be at line level.

Using instrument level into the return socket won't give good result (e.g. plugging your bass directly in to return socket).

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14 minutes ago, jrixn1 said:

I think @nilebodgers is on the right track.  If the GK send/return loop is at line level,  your Helix (or anything you plug into the return socket) should also be at line level.

Using instrument level into the return socket won't give good result (e.g. plugging your bass directly in to return socket).

Thanks, and this is my question. Is the GK head different to other heads? Are send/return chains normally like this? According to the manual the Return impedance is 50k. Obviously i can check specs if i buy another head, but was wondering if this is the norm.

 

Edited by dave_bass5

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15 minutes ago, dave_bass5 said:

Thanks, and this is my question. Is the GK head different to other heads? Are send/return chains normally like this? According to the manual the Return impedance is 50k. Obviously i can check specs if i buy another head, but was wondering if this is the norm.

I would think most send/return loop are at line level.

If the return socket is also the power amp input, I don't think it could be anything else?

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2 minutes ago, jrixn1 said:

I would think most send/return loop are at line level.

If the return socket is also the power amp input, I don't think it could be anything else?

Yeah but to my untrained eyes it looks like there is a level knob between the Return jack and the master in the diagram above, and i know this is always set very low as its my gain channel .

Ill have a play tonight and see if that makes a difference. Its just something id like to understand more.

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Ah, ok.  That's a question more about this GK's two-channel gain feature than the effects loop - and I don't know the answer :lol:  I'd think though if you're using channel A (and so therefore the level B knob is not in use) you should be able to get a usable output level from the combination Helix and GK.

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2 minutes ago, jrixn1 said:

Ah, ok.  That's a question more about this GK's two-channel gain feature than the effects loop - and I don't know the answer :lol:  I'd think though if you're using channel A (and so therefore the level B knob is not in use) you should be able to get a usable output level from the combination Helix and GK.

It wasn't until this morning when i looked at the diagram that i saw the level 2 control in the signal path. Im sure its not that but ill investigate tonight or over the weekend.

I can get more than enough signal out of the amp using the front input,  but i was sort of hoping to get a less coloured tone by just using the power stage. I see so many posts about people just using the power stage that i was surprised it didnt work last night for me. Must admit it did cross my mind to change the output of the Helix but it was just as quick to change inputs, and i also gained the EQ section. Id prefer to use it like this anyway. Might be getting a Quilter BB800 soon anyway.

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Level B doesn't do anything unless the 2nd channel (Gain B) is active. If you were using the FX return as an input only then you'd leave the amp in the 1st channel mode so Level B is out of circuit and only the overall Master affects the output.

The helix would still need to be in line level output mode to drive the MB800 hard enough going in via the FX return.

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24 minutes ago, nilebodgers said:

Level B doesn't do anything unless the 2nd channel (Gain B) is active. If you were using the FX return as an input only then you'd leave the amp in the 1st channel mode so Level B is out of circuit and only the overall Master affects the output.

The helix would still need to be in line level output mode to drive the MB800 hard enough going in via the FX return.

Thanks for the clarification. One thing im still not clear on.

In the manual it states 'This input allows the signal from outboard effects devices to be inserted before the boost section.'

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