Volume Loss Help

[non]

i have a ampeg ba108 practice amp that has a issue that might be impedance related.
the amp has a aux input. if i put a pedal in the fx loop and turn the pedal on the volume from the aux input drops really low.
if i turn the pedal off the aux input level get loud again. i have tried different pedals in fx loop with the same result. i have tried different things in the aux input ie. laptop. mp3 player, drum machine and the volume still drops with the pedal in the fx loop is on.
any ideas what is going on?

thanks

 

[abarson]

Sounds abnormal. What does Ampeg say about the situation?

 

[Wasnex]

i have a ampeg ba108 practice amp that has a issue that might be impedance related.
the amp has a aux input. if i put a pedal in the fx loop and turn the pedal on the volume from the aux input drops really low.
if i turn the pedal off the aux input level get loud again. i have tried different pedals in fx loop with the same result. i have tried different things in the aux input ie. laptop. mp3 player, drum machine and the volume still drops with the pedal in the fx loop is on.
any ideas what is going on?

thanks

The schematic for the amp can be found here. [Invalid or Expired Link Removed]

Note the Aux In is connected at the Effects Return. When you plug a pedal into the return, the output impedance of the pedal is loading down the Aux In signal.

FY, The Effects Loop on this amp is line level so it's not really suited for an effects pedal anyway. Pedal typically operate at instrument level.

 

[non]

The schematic for the amp can be found here. [Invalid or Expired Link Removed]

Note the Aux In is connected at the Effects Return. When you plug a pedal into the return, the output impedance of the pedal is loading down the Aux In signal.

FY, The Effects Loop on this amp is line level so it's not really suited for an effects pedal anyway. Pedal typically operate at instrument level.

thanks for the schematic. i see that now.
why would the effects loop not be instrument level?

 

[BassmanPaul]

thanks for the schematic. i see that now.
why would the effects loop not be instrument level?

Because a lot of folk use rack mounted effect units of various kinds that are all line level. Put your effects where they should be - in front of the amp.

 

[Wasnex]

thanks for the schematic. i see that now.
why would the effects loop not be instrument level?

From what I have seen, the majority of effects loops are line level.

The problem you are having would seem to be a bit of a design flaw IMHO, but I believe the amp is work as it should.

 

[Bass_Pounder]

why would the effects loop not be instrument level?

Because it is between the preamp, and the power amp. Therefore, already boosted to line level for the power amp's use.

 

[agedhorse]

The majority of effects loops are line level because:

1. The effects loop is a place to insert a line level device (there are some line level pedals but most are instrument level)

2. The effects send on many designs also becomes a line level preamp output that can drive an external power amp.

3. The effects return can be used as a power amp input that takes its signal from a line level preamp output. Almost always, when plugging into the return, it breaks the link between the effects send and effects return jacks.

 

[non]

thanks for the replies everyone.
so would it hurt anything if the instrument level pedal in the fx loop is on and to just crank the volume all the way on the aux in devices so they can be heard?

 

[agedhorse]

You would probably overdrive the pedal as it's expecting instrument level whichi s much lower than the loop level.

 

[non]

Because a lot of folk use rack mounted effect units of various kinds that are all line level. Put your effects where they should be - in front of the amp.

what i was trying to do is i am getting real boomy bass and the amp eq cannot get rid of the offending frequency so i set the amp eq flat and use a multi band eq pedal in the fx loop to solve the problem, which it did. but then i am getting the volume loss as i described.

 

[non]

You would probably overdrive the pedal as it's expecting instrument level whichi s much lower than the loop level.

that would explain the loud hiss when the pedal is engaged.

 

[Wasnex]

that would explain the loud hiss when the pedal is engaged.

Yes, typically you either over drive the instrument level pedal or have a poor signal to noise ratio.

 

[agedhorse]

Time to study up on gain structure...

 

[non]

Time to study up on gain structure...

as a pedalboard aficionado i am aware of gain structure. i have never had a need to use a fx loop so i was not aware the loop was line level.
thanks all for the lesson. i learned something today.

 

[BassmanPaul]

what i was trying to do is i am getting real boomy bass and the amp eq cannot get rid of the offending frequency so i set the amp eq flat and use a multi band eq pedal in the fx loop to solve the problem, which it did. but then i am getting the volume loss as i described.

Sometimes things work and sometimes they don’t. Time to try a new tack.

Perhaps a rack mount EQ in the Loop will do what you need.

Edit: I have a suitable one on a shelf in my garage if you’re anywhere near me.

 

[non]

Sometimes things work and sometimes they don’t. Time to try a new tack.

Perhaps a rack mount EQ in the Loop will do what you need.

Edit: I have a suitable one on a shelf in my garage if you’re anywhere near me.

this is just for my little "bedroom" practice amp and space is limited but i appreciate the offer.