Pre-Amp + Driver + Power Amp Setup: What Am I Doing Wrong?

[SamTheMusicMan]

Recently, I decided to go down the path of having a pre-amp + power amp setup due have a bit more flexibility with my wattage, sound, setup, etc. It didn't take me long that the pre-amp I was interested in, the Radial Bassbone OD (convenient because I am a frequent doubler) would not drive the power amp. I tried an Ebtech Line Leveler, which didn't work because of what I assume was an impedance issue. Now, I've just tried the Lehle Sunday Driver, with better results, but it still can only drive my Crown XLS-1002 to just barely the second bar, even though the Sunday Driver is cranked.

So what is going wrong in my setup? My bass is going through various effects pedals, coming out of the Bassbone OD's Hi-Z 1/4 in output, into the Sunday Driver, which is set to the higher impedance, then into the Crown, which is set to 0.775 Vrms input sensitivity.

I reached out to the folks at Lehle before purchasing the Sunday Driver, and they said the unit reaches +22dBu. When I crunched the numbers using this converter they supplied me (dB dBu dBFS dBV to volts audio conversion digital - calculator volt to dBu and dBV dB mW SPL dB decibels 0 dBFS - convert dB volt normal decibels relatioship relation explanation analog audio absolute level true rms convertor converter decibel to dbfs converter calculation online attenuation loss gain ratio reference audio engineering sound recording dBFS dBVU 0 dB audio logarithm level converter peak to peak p-p impedance voltage pro consumer audio digital analog recording level - sengpielaudio Sengpiel Berlin), this should mean that the Sunday Driver is able to clip the the Crown several times over. My thinking is that the output on the Bassbone is "Hi-Z instrument level" (which I assume is standard -10dBv) is being boosted by around 20 dBv by the Sunday Driver (22 dBu=19.8 dBv), which leads to around +10dBv converted to 3.2Vrms. Why isn't that 3.2 Vrms able to drive 0.775 Vrms input sensitivity?

 

[4Mal]

Well... the Bassbone is not a preamp. It has 0 gain. Period.

Not sure about the Lehle but an impedance mismatch is certainly possible. I think a better approach would be to put an actual preamp. That could be a simple little box from Rolls or ART at the low end. It could also be a rackable EQ, parametric being my choice that has a bunch of gain on tap. Rane, DBX... I did plenty of gigs with a PBass into a Rane Parametric EQ into a QSC PLX... It could also be a regular rack mount pre from all the usual vendors. There are a bunch in the GFS here from Arkham (mine) to BBe, Demeter, Ashely and Yamaha... Avalon U5 has 30 db of gain as I recall. It will drive a PLX nicely... lots of choices depending on the color or lack thereof you are looking for.

Rule of thumb... if you can't plug your bass straight into the preamp and from there straight to the power amp, skipping everything else and get acceptable volume - the bassbone isn't going to help.

I've been a use of the BB since V1... still am.

 

[WayneP]

Seems like it should work unless there is some kind of impedence thing going on, as 4Mal mentioned. If that’s not the problem, I suspect maybe you’re losing gain from one or more of the EFX pedals. I’d suggest bypassing them all and plugging your bass directly into the Radial / Lehle / Crown and see what you get.

Regards,
Wayne A. Pflughaupt

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

 

[BassNugget]

Hey Sam. Welcome. I have the Crown XLS. 1002 as well. It is a great amp that works well on the Pro side (1.4v). To me, it was disappointing running it at the .775 setting with my Emotiva pre amp for home audio. I believe Crown says you have -6 db output at that setting as well. Did not go loud at all using consumer audio preamps.

My solution was to keep everything Pro at the 1.4 setting. I bought a low-cost, 4-channel mixer to use as a preamp.

I have one pedal, a Caline Wine Cellar. I don't always use it. But my chain is:

Pedal, small 4 channel mixer, Crown XLS, cabinet. The small mixer has plenty of oomph for the Crown. Keeps the Crown at 1.4v.

The Crown does double duty for me. It is my "hifi" amp in my main stereo system, with the mixer as the "preamp". It also is my bass amp if my needs exceed the combos I have.

Of course it is better to have a pro bass preamp, but I mostly just play clean, using the EQ on the bass if needed or DI out from the combo, so the little mixer works.

 

[walterw]

So what is going wrong in my setup? My bass is going through various effects pedals, coming out of the Bassbone OD's Hi-Z 1/4 in output, into the Sunday Driver, which is set to the higher impedance, then into the Crown, which is set to 0.775 Vrms input sensitivity.

doesn't the lehle allow for balanced output? maybe try that, a trs cable from it to the power amp.

barring that, maybe the bassbone OD is just the wrong box to use as a preamp. i know the typical sansamp bass preamp has an actual switch to set its 1/4" out to line instead of instrument, that lets it drive my QSC PLX3002 easily.

if the bassbone OD's tone is essential to you, maybe replace the lehle at the other end with something like the tech 21 Q strip. even if you don't want to use the EQ on the Q-strip (assuming it works like a BDDI) you can just bypass it, turning it into a transparent active DI with a line level out on the 1/4".

 

[Wasnex]

I don't think you necessarily have an impedance issue; you simply need more gain than the Sunday Driver II provides. Lehle specs 18dB of gain. It does spec a max output of 22dBu, but keep in mind the max input is 20dBu. So only 2dB of gain required to go from max input to max output.

AFAIK, instrument level is generally around -30dBu. Your bass's output may be higher or lower. Assuming your bass is right at -30dBu, applying 18dB of gain only gets you to -12dBu.

Per the converter linked in post #1, -12dBu = 0.194569886VRMS. On the most sensitive setting the Crown needs 0.775VRMS to be driven to full power. So the provided signal level is not even close.

IMHO, ideally you want something the can provide at least 0.775VRMS nominal, so you have a bit of headroom. Although the Sunday Driver II is capable of providing a much stronger output than 0.775VRMS, it probably does not have enough gain to amplify your bass's signal to this level.