Let’s revive Bass preamps (rack mounted!)

[Redbrangus]

Just noticed that in my original post (#3) I forgot to put in a picture showing the rear patch panel I made. Love that thing!

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Here’s a closeup of the top rack, front and back (the Carvin amp died after years of light-duty use so I replaced it with the current Ashly)...

View attachment 7033307

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…and a zoom on the patch panel.

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The line out and amp in jacks in are closed-circuit devices that connect the pre-amp straight to the amp (i.e. the same as if there were jumper cables between them). When a cable is inserted into any jack, the signal is interrupted and the jack then functions as labeled.

Here’s a of an internal view of the previous 6-space incarnation showing the tidy cut-to-length cabling I did.

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Here’s a detail of the back side of the panel (before the additional signal jacks were added) showing power management .

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The left box houses the main power inlet. It is wired to the center outlet that the Furman power strip plugs into. The right box is the convenience outlet. The pig tail allows me to plug it into the center outlet, making the it always hot. Or, I can plug it into the Furman power strip, making it switched.

My only regret is that Speakons were only used on PA speakers at the time the panel was made.

Regards,
Wayne A. Pflughaupt

Ecclesia: Unique Arrangements of Hymns, P&W Standards, and Original Tunes
Administrator, Official Pedulla Club #45
Administrator, Official Heartfield Club #36
Administrator, Official Tobias Club #133
Fretless Club #943
Big Cabs Club #23
My Rig: Stage and FOH Friendly
My Basses

Pretty tidy. As an old PA guy, I always appreciate it when the back side of someone's rack doesn't look like a train wreck. On your rear patch panel, did you use insulating shoulder-washers under the quarter-phone jacks?

 

[WayneP]

Pretty tidy. As an old PA guy, I always appreciate it when the back side of someone's rack doesn't look like a train wreck. On your rear patch panel, did you use insulating shoulder-washers under the quarter-phone jacks?

I actually worked as an installer for a sound company for a number of years, so I spent a lot of time doing custom wiring for racks, including stuffing and wiring panels. That was basically my inspiration.

Didn’t know about the shoulder washers. The first and only time I’ve ever seen one was when I wanted to put a signal input jack on the back panel of the Furman PL Tuner, and ordered one from them. It came with a shoulder washer, I assumed to fully isolate the jack (and audio signal) from the chassis of what was basically an electrical management component.

I did use TRS jacks (closed circuit type) for the signal connections, but not the speaker output jacks.

Should I be concerned, and add some? I haven’t noticed any issues, but maybe I just didn’t know what to look for!

Regards,
Wayne A. Pflughaupt

Ecclesia: Unique Arrangements of Hymns, P&W Standards, and Original Tunes
Administrator, Official Pedulla Club #45
Administrator, Official Heartfield Club #36
Administrator, Official Tobias Club #133
Fretless Club #943
Big Cabs Club #23
My Rig: Stage and FOH Friendly
My Basses

 

[Rocksolid]

Meh. It's cool for what it is, but it's far from the king. There's probably a dozen other ones I'd pick before even thinking of that one.

If you really wanted to go Sansalp, I'd say the PSA is WAY cooler than the 2112

And that's why we have so many flavours to choose from I suppose. I would rate the RPM and VT Rack before both of those as far as the sansamp products go.

 

[FugaziBomb]

And that's why we have so many flavours to choose from I suppose. I would rate the RPM and VT Rack before both of those as far as the sansamp products go.

Yeah, the VT does the Ampeg thing pretty good, but in the realm of Sansamp preamps, the PSA is probably my favorite just for how much it can do.

 

[Redbrangus]

Should I be concerned, and add some? I haven’t noticed any issues, but maybe I just didn’t know what to look for!

If you haven't had any problems, then I wouldn't be concerned about it. (You have to enlarge the holes to use them, BTW.)

Since it's mentioned so often here, I presume you know that you can't use that speaker output arrangement if you move over to a power amp that employs bridged output topology like many of the modern Class D amps. Grounding either of the speaker terminals on those causes release of the magic smoke.

 

[WayneP]

If you haven't had any problems, then I wouldn't be concerned about it. (You have to enlarge the holes to use them, BTW.)

Since it's mentioned so often here, I presume you know that you can't use that speaker output arrangement if you move over to a power amp that employs bridged output topology like many of the modern Class D amps. Grounding either of the speaker terminals on those causes release of the magic smoke.

Yikes. The amp in the rack is an Ashly SRA-2150. Ashly claims the output circuitry is Class D. I have seen the speaker thing mentioned, but didn’t really get what it was about. Wonder what saved my bacon?

Do you have a source for the shoulder washers? I can’t find anything that seems to be specific to this application.

Regards,
Wayne A. Pflughaupt

Ecclesia: Unique Arrangements of Hymns, P&W Standards, and Original Tunes
Administrator, Official Pedulla Club #45
Administrator, Official Heartfield Club #36
Administrator, Official Tobias Club #133
Fretless Club #943
Big Cabs Club #23
My Rig: Stage and FOH Friendly
My Basses

 

[Redbrangus]

I've communicated with @WayneP via DM, but I note this: not all Class D amps utilize BTL or bridged topology, but many do. Those are the ones that would be endangered by grounding the black (but still 'hot') speaker output terminal via this quarter-phone patch panel. Apparently -- and luckily -- his amp did not have this grounding scheme.

For those interested, the part number for those shoulder washers is Switchcraft S1029. Searching Amazon will probably turn up a number of sources. My Google search turned up this place, probably familiar to some folks here: Tube Depot

Edited to correct the descriptive title of the link... Tube Depot, not Tube Doctor.

 

[agedhorse]

I think you got lucky, I don’t think that’s an internally bridged model. It’s externally bridgable however, so the warning applies to that mode.

In general, it’s safest in all regards to use isolated jacks, eliminates all kinds of potential ground loops.

 

[DWBass]

Still use a BBE BMax in my rehearsal rig but bought an integrated EBS amp (8 lbs) for live performance. I’m not ditching my passive enclosure and dropping coin on a powered cab.

Riis

I still have my BBE BMax/rack rig. I have not used it in almost 5 years! May be selling it.

 

[WayneP]

IIn general, it’s safest in all regards to use isolated jacks, eliminates all kinds of potential ground loops.

@Redbrangus has volunteered to send me some of the isolation washers he has in excess stock, so I’m definitely going to get this done. Hopefully my unibit will have the right hole size.

Regards,
Wayne A. Pflughaupt

Ecclesia: Unique Arrangements of Hymns, P&W Standards, and Original Tunes
Administrator, Official Pedulla Club #45
Administrator, Official Heartfield Club #36
Administrator, Official Tobias Club #133
Fretless Club #943
Big Cabs Club #23
My Rig: Stage and FOH Friendly
My Basses

 

[Rocksolid]

Picked up a Crown XLS1002 (at a bargain price) to go with my pre rack.

 

[WayneP]

My Ashly BP-41 is currently out for a makeover to clean up all the scratchy pots and switches. In its place for the time being is my Ashly SC-40 – one of the originals with the nifty oscilloscope logo. Easily 45 years old and still works like a champ!

Regards,
Wayne A. Pflughaupt

Ecclesia: Unique Arrangements of Hymns, P&W Standards, and Original Tunes
Administrator, Official Pedulla Club #45
Administrator, Official Heartfield Club #36
Administrator, Official Tobias Club #133
Fretless Club #943
Big Cabs Club #23
My Rig: Stage and FOH Friendly
My Basses

 

[D.M.N.]

I've only just started down the rack preamp path. Currently have two Ashly SC-40s and am in the process of building an Acoustic 360 preamp in a rack. I primarily use them for recording, haven't experimented with live use yet. Absolutely love the SC-40s for tracking with a cab IR straight in, probably the best recorded tone I've found yet.