Separate preamp/power amp question. I want more volume...

[Yorkshire Bottom End]

I have a Sadowsky SBP-1 running into a 600w GSS Baby Sumo. 4ohms into two TE 110 cabs.

I don't think I'm getting enough volume from the Sumo even with two cabs, and I wonder if it's the Sadowsky that isn't 'driving' it enough.

I love the small set up, and have built an angled wedge for one speaker and sit the other on an isolation pad. They're both 300w RMS.

Brand new Custom Lynx speaker cables and connecting lead between the Sadowsky and Sumo.

Articulate and clear but I don't feel it's loud enough.

First time I've gone down the separate pre/power route. Could it be the preamp or somthing else...? Thanks

[FugaziBomb]

A quick Google search came up with the Sumo requiring less than 10k ohm input impedance while the Sadowski has an output impedance of 12k, so there might be something to that.  I'd definitely dive deeper on that to confirm those numbers are right, but it's a step in the right direction.

Edited Friday at 14:47 by FugaziBomb

[Yorkshire Bottom End]

1 hour ago, FugaziBomb said:

A quick Google search came up with the Sumo requiring less than 10k ohm input impedance while the Sadowski has an output impedance of 12k, so there might be something to that.  I'd definitely dive deeper on that to confirm those numbers are right, but it's a step in the right direction.

 

Thanks for that. I love the Sadowsky but I might have to look into other preamps. So many good ones around. 

I can keep the SBP-1 for a DI if I'm not using my rig.

[FugaziBomb]

1 minute ago, Yorkshire Bottom End said:

 

Thanks for that. I love the Sadowsky but I might have to look into other preamps. So many good ones around. 

I can keep the SBP-1 for a DI if I'm not using my rig.

You might be able to find a different power amp with selectable input sensitivity.  The Crown rack amps I have both have selectable input sensitivity.  That might be a tall order in terms of free standing power amps, though. 

[Yorkshire Bottom End]

1 hour ago, FugaziBomb said:

You might be able to find a different power amp with selectable input sensitivity.  The Crown rack amps I have both have selectable input sensitivity.  That might be a tall order in terms of free standing power amps, though. 

 

It's the size and weight with the Sumo I was after. Or lack of. I've put my TE Elf head through it and I'm getting better results. Just ordered an MXR M81 and a Behringer BDI thing to compare and contrast. I can always send them back if I'm not happy or, knowing me, I'll just keep them!

[FugaziBomb]

10 minutes ago, Yorkshire Bottom End said:

I'll just keep them!

This attitude is why my music room eventually took over the whole floor.  My basement looks like a music store these days 

[Dan Dare]

You aren't really running a pre/power rig if you're expecting your bass to drive a power amp directly. I've not come across a bass that will do that. Onboard active pre's do not deliver enough poke to do the job, in my experience. 

[Bill Fitzmaurice]

The SBP-1 is a floor pedal, not an active bass, but you're on the right track. Floor pedals by and large are gain configured to drive a full on bass amp, not a power amp.

[Yorkshire Bottom End]

57 minutes ago, Dan Dare said:

You aren't really running a pre/power rig if you're expecting your bass to drive a power amp directly. I've not come across a bass that will do that. Onboard active pre's do not deliver enough poke to do the job, in my experience. 

 

I'm not doing that. It's bass > preamp > power. I'm not running a bass directly into a power amp.

[Yorkshire Bottom End]

7 minutes ago, Bill Fitzmaurice said:

The SBP-1 is a floor pedal, not an active bass, but you're on the right track. Floor pedals by and large are gain configured to drive a full on bass amp, not a power amp.

 

So going on what you've said, even with an MXR M81 (which I've ordered to test) I'm not going to drive the Sumo to its full potential?

What are my options then? I thought a decent preamp pedal straight into the power amp would suffice. Seems not with the SBP-1.

[Jack]

The cheapest way to get a really beefy signal are the Behringer (mic100) or Rolls (mp13) units. 

Edited Friday at 19:49 by Jack

[warwickhunt]

It could be the level going to the power amp (Sumo), it might be the output form the Sumo is inefficient, potentially it could be the speaker inefficiency or simply lack of displacement.  Personally I'd see if you can trial the replacement of one of the 3 components... possibly try a different preamp/DI first.  If the issue isn't the preamp I'd be wondering if the speakers are giving you enough of what you want.

[Yorkshire Bottom End]

I've got the Behringer and MXR on the way so I'll see what they're both like. Behringer was £23 (!) so I'll keep it anyway. MXR is more than five times as much! Who cares if I get either of them to do what I need!

[BassmanPaul]

Using a power amp in your system is a whole new ball o' wax. You have to take into account the input impedance of the power amp and the output impedance of the pre-amp. Typically the output impedance of the pre should be far lower than the impedance of the power amp. This usually directs you to a proper rack mount pre-amp and not a pedal.

 

I use a 2KW capable stereo power amp but I designed and built a tube pre-amp specially to drive it bearing in mind the factors mentioned above. Good luck!

 

[warwickhunt]

I occasionally use my preamp pedal into the effects return or 'pre-in' of a (shared) bass amp thereby utilising it purely as a power amp, I can then take out the anomalies of the bass amp preamps... the speakers are a whole other thing!  LOL  You could try the SB1 like this and see if the impedance differential makes much difference from the Sumo.

 

[Bill Fitzmaurice]

6 hours ago, Yorkshire Bottom End said:

 

So going on what you've said, even with an MXR M81 (which I've ordered to test) I'm not going to drive the Sumo to its full potential?

What are my options then? I thought a decent preamp pedal straight into the power amp would suffice. Seems not with the SBP-1.

Pedals are made to go into bass amps. Rack mount pre-amps are made to go into power amps. I'm sure there are exceptions, but the only way to know if any combination is to make sure that the output voltage of the pedal is at least equal to the required voltage to drive the power amp to full output. Unfortunately neither your SPB-1 nor your GSS provide those specs.

Quote

You could try the SB1 like this and see if the impedance differential makes much difference from the Sumo.

The impedances aren't the problem, it's the output voltage of the pedal and the input voltage sensitivity of the power amp.

Edited Saturday at 02:02 by Bill Fitzmaurice

[crazycloud]

2 hours ago, Bill Fitzmaurice said:

The impedances aren't the problem, it's the output voltage of the pedal and the input voltage sensitivity of the power amp.

Yup.

 

It's a gain structure issue; the 'preamps' simply supply insufficient gain to be able to drive the power amps to full output because as was said earlier, they're designed to drive the instrument input of a conventional bass amp or head.

Likewise, it could be an issue with many people being reluctant to actually turn the gain control up enough. I've seen many who erroneously believe that turning the control past 12 o'clock (some have told me 9 or 10) will cause damage to something.

[Bill Fitzmaurice]

Tell that to Derek Smalls. ☺️

[bremen]

5 hours ago, Bill Fitzmaurice said:

Tell that to Derek Smalls. ☺️

I believe his new rig goes one beyond 11 - actually to infinity

[Downunderwonder]

The Sumo power output is superfluous with a 210 cab set despite what TE would have you believe.

 

The Elf should be pushing them along without any danger of blowing them up. If that's not loud enough I think you should be looking for a pair a 12" speakers before anything else.

[JPJ]

3 hours ago, bremen said:

I believe his new rig goes one beyond 11 - actually to infinity

 

[bremen]

If you like the pre and you like the power amp, simplest thing would be a wee box offering about 12dB (opinions?) gain, flat response and maybe a 40Hz HPF.

 

Such things must exist. I can share a design and if you like, buy the bits and stuff the boards.

 

Usual rate, £ to food banks +cost of parts.

[agedhorse]

It’s not gain or gain structure but limited maximum output level of many (not all) pedal preamps that’s responsible for not being able to drive a power amp to rated output. 
 

if a power amp has an input sensitivity of +4dBu (power amp sensitivity is measured with the input level control all the way up), the preamp must have a maximum output level capability of AT LEAST +4dBu (I recommend 6dB more if possible) in order to achieve rated power.

 

The output impedance of the driving device (preamp) should be roughly 1/10th (or less) the value of the input impedance of the driven device (power amp). If not, there will be additional losses. In the case where the output impedance is 12k and the input impedance is 10k, there will be a ~6dB loss.

 

Unfortunately, these specs are often omitted (or unknown/unmeasured) by manufacturers which makes matching a crapshoot. 
 

As an example of a pedal preamps that’s that can easily drive a power amp to rated output, the Genzler Magellan Pre-Di is one. It also includes all of the important, necessary specs to document the performance:

 

Specifications

DIMENSIONS: 6” (152mm) W x  4.3” (110mm ) D  (w/ jacks)  x  2.5” (63mm) H  (w/ knobs and feet)

WEIGHT: 1.1 lb (0.5kg)

POWER SUPPLY: 9VDC-18VDC (low noise type), either polarity, 80mA

POWER SUPPLY JACK: 2.1mm center pin with 5.5mm barrel (standard Boss pedal dimensions)

INPUT IMPEDANCE: 1 Meg Ohm

INPUT SENSITIVITY (nominal): -10dBu to -20dBu (instrument level)

INPUT SENSITIVITY (maximum):  >0dBu (9V supply), >+5dBu (12V supply), >+10dBu (18V supply)

HIGH PASS Filter Range: 25Hz – 120hz, 18dB/oct variable

EQ Filter Points:

LOW: +/-15dB shelving below 75 Hz

MID: +/-15dB peak-dip, between 150Hz – 2.8kHz

HIGH: +/-15dB shelving above 6kHz

PREAMP OUTPUT IMPEDANCE: 1k ohm (unbalanced), 2k ohm (balanced)

PREAMP OUTPUT LEVEL (nominal): -10dBu to +4dBu (line level)

PREAMP OUTPUT LEVEL (unbalanced maximum): +8dBu (9V supply) +12dBu (12V supply), +16dBu (18V supply)

PREAMP OUTPUT LEVEL (balanced maximum): +14dBu (9V supply) +18dBu (12V supply), +22dBu (18V supply)

DIRECT OUTPUT LEVEL (balanced nominal): -30dBu (mic level)

DIRECT OUTPUT IMPEDANCE: 2k ohm (balanced)

AUX INPUT IMPEDANCE: 10 K Ohm

AUX INPUT LEVEL (nominal): -10dBu, stereo (sums to mono)

AUX INPUT LEVEL (maximum): +10dBu, stereo (sums to mono)

HEADPHONE OUTPUT: Drives headphones and IEM buds from 8 ohms -200 ohms, stereo output, mono signal path.  (Higher impedance headphones, such as 600 ohms, will result in less output and headroom.)

 

 

[BassmanPaul]

Thank you Andy for putting the facts so succinctly.

 

[BassmanPaul]

Why do adverts such as the one above have to use crudity. It certainly put me off from interest in SWR products and I'm sure there must be more of us of the same mind. 🤯