power amp and preamp pedal

[mario_buoninfante]

Hi all,

Recently I have been thinking about preamps and amps, having the bass going through a preamp pedal and then another preamp (combo or head), and how that affects the sound.
So, I was thinking about just using a "power amp" and a preamp pedal (+ any other pedal of course). Something I saw some people do years ago (I remember a guitar player from back in my teenhood). This to keep consistency (as much as possible) between my preamp pedal DI out and the sound coming out of the speaker.

I also saw some brands making these:

https://www.grbass.com/portfolio/pure-amp/

Does anyone have any experience with this kind of setup? pros and cons?

Cheers,
Mario

Edited February 6, 2023 by mario_buoninfante

[Jakester]

I tried this a while back using my pedalboard and preamp into a GSS Baby Sumo, but I could never get satisfactory results. 

 

I think you need to ensure that the signal is at the correct level for the power amp to 'see'. My issue was despite using a preamp and an active bass, the signal level was too low. I'll have a look and see if I can find the thread because there were a couple of choices mentioned on that which might be useful. In the end I just went back to pedals + amp. 

 

Another option if you haven't spent the £££ already might be pedals and preamp into powered speaker, rather than power amp + cab. You can then run a cab sim etc which would give you the option of changing your cab sound as well.  

[mario_buoninfante]

amazing thanks for the feedback.
I'm not interested in speaker simulators atm, but I see that's an option

[mario_buoninfante]

Quote

My issue was despite using a preamp and an active bass, the signal level was too low.

also, I assume this is when the gain section on some power amp like the GR I linked above, come into play.
I know that'll probably be another preamp, but at least seems to have been designed to be transparent

Edited October 27, 2022 by mario_buoninfante

[Lozz196]

In my last band I used a Tech21 Para Driver into my Ashdown amps but with the eq on those in the off position. Not exactly the same as a power amp but doing pretty much the same. Worked well.

[mario_buoninfante]

sure, bypassing the EQ is already something!

[mario_buoninfante]

just found this too.
not sure I want to buy an Ampeg to bypass its pre though
 

 

Edited October 27, 2022 by mario_buoninfante

[mario_buoninfante]

that's interesting too

 

 

[Waddycall]

I think EBS claim that the microbass 3 has enough output (0dbv) to go straight into a power amp. It’s something I’m considering as I have a decent QSC power amp and the microbass 3 has all the tone shaping I need.

https://ebssweden.com/content2/effects/ebs-microbass-3-professional-outboard-preamp/

[agedhorse]

In general, pro audio power amps are +4 to +8dBu rated sensitivity with the level controls fully up. Generally you will want 6dB of drive headroom to avoid overdriving the preamp while approaching the clip or limit point of the power amp.

 

Some power amps also have exhibit lower sensitivity when driving unbalanced inputs, and many preamps have 6dB lower maximum output level when driving from unbalanced (or unbalancing via adapters) outputs. 
 

 

These are all things that need to be tested/verified to determine compatibility. It’s not always easy with the limited specs that are often provided.

[jezzaboy]

I used this set up and if you stick a ART Tube Pre Amp at the end of your signal chain, it will provide a hot enough signal to drive the power amp.

 

The MXR DI I have doesnt give a hot enough signal to do this on it`s own. And someone has one for sale on here at the moment. You can use it for vocal, bass, guitar etc.

[mario_buoninfante]

1 hour ago, Waddycall said:

I think EBS claim that the microbass 3 has enough output (0dbv) to go straight into a power amp. It’s something I’m considering as I have a decent QSC power amp and the microbass 3 has all the tone shaping I need.

https://ebssweden.com/content2/effects/ebs-microbass-3-professional-outboard-preamp/

it seems like this can drive a power amp too

https://www.premierguitar.com/tech-21-geddy-lee-yyz-signature-sansamp

[mario_buoninfante]

from its manual

Edited October 27, 2022 by mario_buoninfante

[Jack]

My first attempt at frfr, long before that term was coined, was my pedalboard (topped with an MXR preamp) into a rack and then a Dr Bass cab. I didn't have quite enough juice to push the QSC without a little help and so I used a Presonus channel strip. 1600W, 2x12" subs, a 6" mid and 1" tweeter. Sounded immense. Please excuse the photo quality, this was the good old days. 

 

 

 

[mario_buoninfante]

I start thinking that the GR Bass Pure Amp might just be the ideal solution for this, since they also have a gain stage in case the preamp doesn't provide enough signal.

Edited October 27, 2022 by mario_buoninfante

[3below]

Used this type of setup recently for about 4 years in gigs, would still do if my band was in some functional state.   Tech 21 Sansamp RBI rack mount or Tech21 Sansamp Leeds pedal > QSC (until it died) then  Crown or Peavey power amp  > Barefaced Dubster or Sherman Audio custom 15 / 6 / horn cab.  Really like it, works well, the Leeds pedal in particular gives me the essence of the Hiwatts (100 & 200W) that I owned in my youth without the weight or price these days.   Some (Crown to name one) power amps have selectable input sensitivity.  The DSP high pass filter to prevent speaker damage with the Crown is really useful if you are in a loud band.

[Tech21NYC]

Power amps like Crown, QSC etc are designed for pro audio applications. If they were designed for musical instrument use you would be able to easily plug in a low output high impedance instrument into them. This is not the case. This doesn't mean that it's impossible to use other devices with them but you need to be aware of the input sensitivity of the power amp. Instrument level devices like our DI's can achieve anywhere from instrument level (-10dB) to consumer line level (0db) . This depends on the way they are set. Microphone, instrument, consumer and pro audio levels represent an "operational range" which the equipment is designed to work with. They are not a constant like a voltage or impedance measurement. 

 

If using one of our DI's with a pro audio power amp you want something that has an input sensitivity of .775 volts (0db) or lower. Some power amps have adjustable input sensitivity. It also depends on how much power the amp has in relation to the speaker system though you tried to use components that are properly matched.

 

The other thing that many people get wrong is that you don't want to drive a power amp at its peak power. You need headroom to prevent the peaks from clipping the power amp. What we see with many players is that they get bogged down in the numbers and try to use a small speaker system with high wattage heads and think they can play any gig. If you need a lot of volume you need a lot of speakers. This is why we made our B410-DP cabs at 16 ohms for dUg Pinnick. He uses 4 cabs to get the thunderous volume he is known for with his 1000 watt signature dUg Ultra amp. 

[Skybone]

I'm running my POD Go into the Effects Return on my Ashdown combo, effectively bypassing the amp's preamp. Works for me.

[Dan Dare]

I used to have a Lehle pre' (which I regret moving on) and tried to run it direct into a power amp. I found I had the same issue as Jakester above. Couldn't drive the power amp adequately. Shame, as the Lehle was excellent. In the end, I gave up and bought an AG700 and traded the Lehle against it.

Edited October 28, 2022 by Dan Dare

[agedhorse]

22 hours ago, mario_buoninfante said:

I start thinking that the GR Bass Pure Amp might just be the ideal solution for this, since they also have a gain stage in case the preamp doesn't provide enough signal.

Maybe, but there's no input sensitivity spec anywhere in their documentation so there's no concrete way to know for sure without trying it (or asking the manufacturer what the input sensitivity is for rated output).

[mario_buoninfante]

4 hours ago, Tech21NYC said:

Power amps like Crown, QSC etc are designed for pro audio applications. If they were designed for musical instrument use you would be able to easily plug in a low output high impedance instrument into them. This is not the case. This doesn't mean that it's impossible to use other devices with them but you need to be aware of the input sensitivity of the power amp. Instrument level devices like our DI's can achieve anywhere from instrument level (-10dB) to consumer line level (0db) . This depends on the way they are set. Microphone, instrument, consumer and pro audio levels represent an "operational range" which the equipment is designed to work with. They are not a constant like a voltage or impedance measurement. 

 

If using one of our DI's with a pro audio power amp you want something that has an input sensitivity of .775 volts (0db) or lower. Some power amps have adjustable input sensitivity. It also depends on how much power the amp has in relation to the speaker system though you tried to use components that are properly matched.

 

The other thing that many people get wrong is that you don't want to drive a power amp at its peak power. You need headroom to prevent the peaks from clipping the power amp. What we see with many players is that they get bogged down in the numbers and try to use a small speaker system with high wattage heads and think they can play any gig. If you need a lot of volume you need a lot of speakers. This is why we made our B410-DP cabs at 16 ohms for dUg Pinnick. He uses 4 cabs to get the thunderous volume he is known for with his 1000 watt signature dUg Ultra amp. 

 

thanks for this, it's really useful!

[mario_buoninfante]

2 hours ago, Skybone said:

I'm running my POD Go into the Effects Return on my Ashdown combo, effectively bypassing the amp's preamp. Works for me.

I need to try this with my setup too.
I'll report the results

[mario_buoninfante]

14 hours ago, agedhorse said:

Maybe, but there's no input sensitivity spec anywhere in their documentation so there's no concrete way to know for sure without trying it (or asking the manufacturer what the input sensitivity is for rated output).

that's fair. I did see some official videos (in Italian though) on YT where the presenter was saying one could even go straight into that with their bass.
I think it's the gain stage they have in place that allows that.

[NancyJohnson]

For many years I ran a 4U rack, a dual channel Matrix Poweramp (2U) that could be bridged for more output, Korg tuner (1U) and a variety of Tech21 units RBI (5/5), GED2112 (initially great, developed a fault, distributor hopeless 5/5 to 1/5), VTBass (sold on, didn't like it).

 

The great thing about the different pre-stages is you're just amplifying the manufacturer's unit uncoloured and it's pretty simple to swap these around for different applications.  I also ran a board with a dual channel set up BDDI/GT2 which I ran into the Matrix and into two cabs...this kind of emulated the dUg tone.

 

If @tech21nyc had rolled out the dUg pre in a 1U unit, I'd probably still be running the rack to this day.

[Downunderwonder]

I found out the hard way that 'line' on a Sansamp BDDI was something less than what I was used to.

 

I was doing a show gig and done with rehearsals I had left amp and backup amp with the one cab safety locked up in the theater all set to go.

 

Got last minute pub gig. Went home and grabbed up some gear. BDDI, 1000w Crown power amp, 210 cab. Plenty for small bar even if the drummer was a cousin of the drummer in The Electric Mayhem.

 

Not actually, what with the just discovered gap between the BDDI output and Crown 1.4V rated input. It just managed to keep up by using all available output from the BDDI and cranking the amp.