Onboard preamp for P-Bass

BeardyGit

I've been in touch with a small home-based company located in the US to ask them to build an onboard preamp for my Fender P bass. The response was very good - Apparently it's something that's been on the owners mind for quite some time. He's come back to me to ask what other features would be of interest as he's going to use my one-off as a prototype for a future commercially available product.

This guy has been a great source of information for many bassists when they've had problems over many years so I'd like to help him out if I could. I've been careful not to disclose what the company is, what products they sell etc. as I don't want this to come across as an advertisement in any way.

What we have here is an opportunity to contribute directly as 'Joe Bloggs' musicians towards the design specification of a product that many of us could buy if we want in the next 3-6 months. If you play a passive bass guitar and think you would have use for an onboard preamp, what extra features would you like to have available and why?

I've specified that it should be a simple installation, have a bypass switch (so I can run fully passive if I want) and be as transparent/colourless as possible so I can simply have a boosted signal from my Precision. What would you add if you could? Bass/Treble boosted EQ for example? Low battery LED? External PSU connector for home/studio use? What's important to you if you think about this type of product?

Thanks,

Gil

jcoote

thats sweet man great idea...maybe some sort of modeling like the line 6 variax...low battery is cool...maybe internal effects???

BeardyGit

Just to clarify something here that I forgot to mention - I KNOW it's possible to build a preamp circuit myself. I don't want to for one simple reason - This guy is very good at what he does so I'll leave it to the pro!

Also, he's given me a guideline price of €50 for the basic circuit on a small PCB that will measure approx 20mm (w) x 50mm (l) x 8mm (h). He's basing it on a circuit he's already producing for an electric upright bass guitar. I'll also need to mount a PP3 battery box on the back of the guitar - These cost around €5 or I might just route out a seperate cavity with a coverplate and mount everything in there. I'll let you know as this project progresses but it should be an interesting one to follow. Apparently this circuit is wide frequency and should also work well for guitars.

Anyway, I'm outta here - Gil

Doctor J

You're sticking with the passive pickups though? Perhaps something like my Ibanez 6 string, passive pickups running into an active 3 band EQ (bass cut/boost and treble cut/boost on a stacked pot and variable mid cut/boost on a stacked pot). Then again, the beauty of Precision basses is their simplicity, you've got all the EQ you'll ever need on your amp. These things come with a low battery indicator anyway, when the battery is on the way out, it starts to sound like ****

BeardyGit

Yep - I'm sticking with the passive pickups. For my needs I don't want anything that'll alter the classic P tone, just a hotter signal. You're quite right about the indicator too but there have been times when my Prefix EQ on my acoustic has pretty much just **a* itself with very little warning. This bloke reckons the basic circuit could have up to 1000 hours from a single PP3. Start adding extras and that'll drop away - Possibly quite sharply but we'll have to wait and see.

Doctor J

Would you not consider hotter pickups or even if you don't want to change the pickups, get the current pickups rewound? TBH, a hot signal means very little to me, if you've got a decent amp then you don't need super high output pickups. Once the tone is good, I couldn't give a rats ass how hot the signal is.

BeardyGit

I wouldn't change the pickups - It's for a 57 reissue P bass so I want to keep it as stock as possible. I'm playing it through an Ampeg B25 which doesn't have a master volume control, only a single gain control. By using a preamp I'll be able to run a hotter signal to the head, keeping noise levels low and have a greater range of overall volume control then on the head. It's only a 60 watt head but driving a couple of 15" cabs it can be ridiculously loud at times. It'll also allow me run a longer cable for gigging without the Ampeg boosting noise coming off the lead.

Doctor J

Meh, just get an overwound set of vintage Fralins in there and be done with it. An active pre-amp with an LED is a lot less stock 57 than a good pickup.

Eoin Madsen

Whatever it is, design it to work off external power. Put an extra transformer, rectifier, and filtering (the guts of a 9v adaptor basically) into your amp (with a toggle switch) and send it down the ring in a TRS cable.

Any other original ideas I have go beyond the scope of a mere onboard preamp. Go with the active EQ I guess. I'm not sure I'd bother. You could stick a compressor circuit in as well, and stick on an extra pot for threshold or ratio control. Tbh, I think the less things between the pickup and the actual preamp, the better.

BeardyGit

Thanks for the comments so far - All constructive I'd say. I don't think I'll be looking to integrate a compression component into the design as this would either be very bulky or a compromised circuit - For this type of functionality I think an outboard unit will always win hands down - I think you'd agree Eoin?

I considered hot pickups but really want to keep the option of running with the stock P bass pickups and passive circuitry - Replace the pickups and I change the tonal quality of the bass. I'm already using one of this guys amplification products and the acoustic transparency is really quite impressive. If he can deliver the same 'audiophile' neutrality with the pre-amp it would be much better for my intents. With the intended mounting I'm using I won't actually have to make any modifications to the external appearance of the bass at all. It could be removed in the future with only some resoldering to tell tales!

I guess the idea here is that whatever basic pre-amp circuit he puts together would ideally be designed so that optional components could be mounted onboard the bass with the provision of suitable connectors into the pre-amp signal chain already integrated with the basic product. That was you could select a modular onboard system to fairly closely match your own ideal requirements from this type of unit.