Preamp (pedal) into a power amp

[DoctorZeus]

I'm in the market for an amplifier. I am thinking a more cost effective (more watts for the power) and (more flexibility on the pre.) solution might be this. Power amplifiers are cheap such as those used in audio. QSC etc. I am wondering if buying a preamp pedal such as a Sans amp and running that directly into a power amp would be a good idea or not? Has anyone done this?

 

[WayneP]

I’m not familiar with everything on the market, but typically guitar signals are fairly weak compared to what’s required for driving an amplifier. You’d need a pedal that outputs a line-level signal, something on the order of 1 Vrms. For best results, the pre-amp’s output voltage should approximately match the amplifier’s input sensitivity rating. If the preamp signal is lower than the amp’s required input sensitivity, you probably won’t be able to drive the amp to its full output.

Regards,
Wayne A. Pflughaupt

Pedulla Club #45 Unique Arrangements of Hymns, P&W Standards, and Original Tunes
Administrator, Official Tobias Club #133
Administrator, Fretless Club #943
Big Cabs Club #23
My Basses
My Rig: Stage and FOH Friendly
Pedulla Club #45

 

[Hurricane Jimmie]

So Anyway, I bought a Class D Peavey power amp and played my passive bass at a gig with it with no preamp. For 350 Watts, I was just barely keeping up with our small band.
Then I used it with my Sans Amp Tech-21 and had plenty of volume and punch.

Good Luck to in your search.

 

[agedhorse]

I’m not familiar with everything on the market, but typically guitar signals are fairly weak compared to what’s required for driving an amplifier. You’d need a pedal that outputs a line-level signal, something on the order of 1 Vrms. For best results, the pre-amp’s output voltage should approximately match the amplifier’s input sensitivity rating. If the preamp signal is lower than the amp’s required input sensitivity, you probably won’t be able to drive the amp to its full output.

Regards,
Wayne A. Pflughaupt

Pedulla Club #45 Unique Arrangements of Hymns, P&W Standards, and Original Tunes
Administrator, Official Tobias Club #133
Administrator, Fretless Club #943
Big Cabs Club #23
My Basses
My Rig: Stage and FOH Friendly
Pedulla Club #45

The preamp’s output voltage must be able to deliver AT LEAST the amplifier’s sensitivity in order to drive the amp to its rated power.

Power amp’s rated sensitivity is measured with the input sensitivity controls fully clockwise and in volts RMS or dBu. Most QSC models are around +4dBu to +6dBu which is between 1 and 1.5VRMS.

The reason I keep mentioning RMS is because it’s not uncommon for pedal builders to use peak voltage which is 1.414 times higher than the equivalent RMS voltage.

 

[onda'bass]

I use a source audio as my pre, run into a crest pro lite2.0 (.075 inp senstvt) I love the idea of changing tone and not the amp. Frequency points ultimately are the secret sauce to why amps sound like they do, I feel Like i can reproduce any amps generic tone by knowing the stats of the amps frequency layout, found in most user manuals. Or i am just a nerd about this topic.

 

[micguy]

I have done this in the past, but I built my own preamp, so I knew the combination would work fine. With randomly chosen pedals, it may or may not work well.

 

[6ornone]

Run a darkglass Adam into a power amp so it’s do able and it sounds great

 

[agedhorse]

I use a source audio as my pre, run into a crest pro lite2.0 (.075 inp senstvt) I love the idea of changing tone and not the amp. Frequency points ultimately are the secret sauce to why amps sound like they do, I feel Like i can reproduce any amps generic tone by knowing the stats of the amps frequency layout, found in most user manuals. Or i am just a nerd about this topic.

No way is the Crest ProLite “.075 input sensitivity”. If you are planning on being a nerd, you might want to update your knowledge.

edit: the PL2.0 is 0dBu input sensitivity which is .775V with the input level controls all the way up. There is an typo/error in the spec sheet for the 2 ohm sensitivity spec, it’s .735V not .350V

 

[onda'bass]

@agedhorse you are correct i just can’t type lol.

 

[jonasparker]

I think you want a power amp with 0.7 volts sensitivity, NOT 1.4.
Crown Drivecore series i believe, at least that's what's on my shopping list per a talkbass recommendation.
Crest CA series, say a CA-9 or even a CA-6, which I own is definitely 0.7 volts sensitivity which means the input signal can be lower and still get full volume. They're old and heavy but awesome. Has bridging option. Mine is with a talented teenager at this time.

Crown X1000 is a good option that's cheap and stripped down and has a switch to toggle between 0.7 and 1.4 volts. I can sell it to you. It doesn't have a bridging option.

I have a couple crown xti's, a 4000 and a 4001, and they're so powerful that the 1.4 volts sensitivity doesn't matter, (plenty loud anyway) until you get a low frequency bump that blows all your speakers. Not recommended but I still use them with caution.

 

[Jim C]

Some of the older Ampeg tube pre's could only support a .775 VRMS input sensitivity.
They were still very usuable with power amps with a 1 VRMS or even 1.5, as the power amplifier's were so powerful that they could be driven far below maximum and still deliver plenty of power for a bass guitar application.
Ampeg made 2 dedicated SS power amps; a 1500 and 1600 watt model in bridged mode.
One had .775 and the other 1.0 as I recall.

 

[agedhorse]

I think you want a power amp with 0.7 volts sensitivity, NOT 1.4.
Crown Drivecore series i believe, at least that's what's on my shopping list per a talkbass recommendation.
Crest CA series, say a CA-9 or even a CA-6, which I own is definitely 0.7 volts sensitivity which means the input signal can be lower and still get full volume. They're old and heavy but awesome. Has bridging option. Mine is with a talented teenager at this time.

Crown X1000 is a good option that's cheap and stripped down and has a switch to toggle between 0.7 and 1.4 volts. I can sell it to you. It doesn't have a bridging option.

I have a couple crown xti's, a 4000 and a 4001, and they're so powerful that the 1.4 volts sensitivity doesn't matter, (plenty loud anyway) until you get a low frequency bump that blows all your speakers. Not recommended but I still use them with caution.

It depends entirely on the preamp pedal. Some can easily provide 5 or 6 volts RMS yet some can't provide more than 1/2 volt.

 

[TOOL460002]

I have run a Sansamp BDDI in a parallel looper directly into an old Stewart PA-1000. Worked for a couple smaller bar gigs, but I also play active basses and the looper/hub I was using at the time could go over unity gain. I feel like I had to really crank it up but definitely worked. Was a while ago.

My approach since then has been to have a rack compressor that I think brings things up to the right impedence or volts or fathoms or whatever unit of measurement it is and have that before the power amp (QSC).

 

[Nebadon2000]

I am wondering if buying a preamp pedal such as a Sans amp and running that directly into a power amp would be a good idea or not? Has anyone done this?

Many Players have been doing this since the 70's [just not pedals] with todays pedals need to heed Agedhorse advice
But I am finding more preamp pedal manufactures claiming their pedals can drive most any Amps as a feature.

Sans Amp pedals I've seen have 2 outputs 1 Instrument for putting it between Bass and Bass Head input and XLR Line Level which should work with Power Amp[receive in on Bass Head]

Back in 2007-2013 I had a Taurus Silverline preamp direct into Roland Active Powered Bass Cabinet worked Great

 

[Medicine Man]

I've done the rack power amp thing, but I've moved on to a Quilter Bass Block. Lighter and easier with a ton of headroom. Not too expensive either.

 

[pglaser01]

If you are planning on being a nerd, you might want to update your knowledge.

and just when I thought I had an all time favorite Agedhorse quote…..

 

[T-boneParish]

i love using an Effectrode LA-1A into a Baby Sumo power amp. Sounds lovely!

 

[DoctorZeus]

Frequency points ultimately are the secret sauce to why amps sound like they do, I feel Like i can reproduce any amps generic tone by knowing the stats of the amps frequency layout, found in most user manuals. Or i am just a nerd about this topic.

I would like to hear more about how this is done. Where you harvest the stats and how you dial it in. What equipment do you have? Sorry if I missed that.

 

[77FenderJazz]

+1 for Quilter BB800 with a preamp pedal. Lighter, cheaper than a power amp and gives you easier connections.

 

[agedhorse]

I would like to hear more about how this is done. Where you harvest the stats and how you dial it in. What equipment do you have? Sorry if I missed that.

IMO, this is overstated. There is so much individually within each amp's design that the "secret sauce" comes down to many different elements that can not be harvested from an owner's manual or specifications.