The John East preamp club

[John East]

John, I had a question about the merits of running my Unipre at 18 volts. Headroom, battery life? You insight would be appreciated.

(Apologies for the delay, I'll work harder to give timely answers)

All East units work with 9V or 18V with no change, apart from adding an extra battery and wiring, or a dual battery box.

Doubling the voltage doubles the head room or maximum signal level that can pass through a circuit. (Double = 6dBs more)

9V allows more than enough signal level for any rig with an instrument input and many power amps alone.

But if you dial in a lot of bass and/or lower mid with the volume set at max, the overall output level could be much greater, and you may experience clipping with 9V. In this case, just backing off the volume will get you back to a clean signal, but still with plenty of output.

If you prefer to work with the volume at max as a reference point, 18V will help to avoid clipping with more extreme EQ settings. We say, if extreme works, go for it, what's the point in having a flexible powerful EQ if you can't use it? Backing of the volume may be necessary with 9V, but unlikely with 18V.

 

[Drop1]

Mr. John,
How do we put the uni's internal adjustment wheels back to the stock settings ?

Is it set up with the wheels centered when shipped?

I tried using an analyzer to find the corresponding frequencies, but my analyzer doesn't have peak hold and trying to play while adjusting the wheels is a bit tedious due the bass waves being so complex.

I normally just set it by ear, but I'm trying to find the default so I can mark the wheels with a sharpie so I have an easy point of reference.

 

[Zeom]

Nice article that I want to share with you. East UK Uni-Pre Onboard Preamp

 

[Drop1]

Does anyone know what each jumper for the pre curve do? There are 2 and you need to set both to go from flat to the pre curve (4db boost at 40hz and 10khz)

I assume it's 1 per pickup, but I could be wrong. In fact, I'd like to be wrong. I'm hoping it's one jumper for the 40hz boost and one for the 10k boost. That would be handy.

The manual doesn't specify. It only shows moving both jumpers to achieve flat or pre curve. It doesn't say anything about mixing jumper postions or what the jumpers actually affect though mixing jumper positions does do different things to the sound. That much I can hear.

 

[MaxSpinrun]

Mine are mixed 40 HZ is set for boosting have my jumpers separated.. low on boost highs on flat. Seems to work.

 

[Drop1]

Mine are mixed 40 HZ is set for boosting have my jumpers separated.. low on boost highs on flat. Seems to work.

How do you know which one is which? Just move them and listen? If the high and low boost are in separate jumpers I love Mr John even more lol. I just wish the manual was a but more in depth.

 

[MaxSpinrun]

Low is the front high is the rear. So I moved just the front to the right. Hope that helps.

 

[Drop1]

Low is the front high is the rear. So I moved just the front to the right. Hope that helps.

That sound right to what my ears hear. Where did you get his info? I'd have assumed the jumper were just one per pickup. Did I over look something in a manual ?

 

[Drop1]

I got it figured out. It's crazy how much thr pre curve and internal ew adjustments can change a basses sound.

Just a few days ago my bass was ALL mid roar and growl. It's till got plenty of growl , hut it's more round and pleasant
I previously had the highs jumper on. This made any boosting of high frequencies too bright. I set that jumper to flat and tuned the treble knobs cutoff frequency and now i can add presence with treble boost without the highs getting overly harsh.
This is a job I was using my mids for becuaery previous set up was so bright already up top.

Now my mid knob is free to do whatever I want with. I don't even need it at home after tuning the bass a treble knobs. I rarely have any reason to touch it. If I want mid cut, I just boost the highs and bass a touch. It creates the perfect scoop becuae ive tuned it to do so. I kinda wish the mids had a width pot. That would be cool.

Turns out most of my complaints about my basses sound were just the high side of the bass was set too high so a bunch of mids (all the way beyond 500hz) was getting boosted any time you increased the bass on the pre which I always run it at about 1 o'clock.
Everything sounds almost perfect now and I still have my amp set dead flat. Crazy how much control the uni pres have.

I also turned the pup pots all the way down to match the passive output. I miss a bit of output, but the tone sounds better so I just make up for the loss with the amp.

 

[Drop1]

I had what i think is a slick idea for our adjustable pre amps. If you like easy options, check it out.

https://www.talkbass.com/threads/switches-in-place-on-jumpers.1651179/

 

[Asher Skerrett]

I see the P Retro is available again after years of being unavailable. Looks like in limited quantities as well.

 

[davedamage]

They dropped at the end of April. I ordered mine as soon as the in stock email showed up.

And it is glorious.

 

[Asher Skerrett]

That's interesting. I only received the email this morning.

 

[Drop1]

I have some single coil pickups with 3 wires.

The grey (3rd wire) is supposed to go to the pres common.

Anyone know where to connect those wires on a uni pre?

 

[Alex Masters]

Earth? Depends on the pickup, but most fender pickups ar black and white (hot/cold) and the grey wire should go to an earthing point, assuming that's what the colours are, or look them up on the manufacturer's website.

 

[Drop1]

Earth? Depends on the pickup, but most fender pickups ar black and white (hot/cold) and the grey wire should go to an earthing point, assuming that's what the colours are, or look them up on the manufacturer's website.

Ground is black, white is hot, grey either goes to common on passive basses or common on active.

My tech wired the grey straight to hot wires. It works somehow, but if it could be less noisy putting the grey wires in the proper place, if like to do that.

Nords wiring diagram says white = pos, black = ground and I'm not sure ehat the grey does but I dont think it's supposed to be wired to the hot side..

It somehow works , but It's not "correct ".

Would the jack ground be common? I don't know a lot about preamp wiring.

 

[ctmullins]

Earth.

Most active preamps use normal earth connections.

Audere is the only exception I know of, and they have great instructions.

 

[Drop1]

Earth.

Most active preamps use normal earth connections.

Audere is the only exception I know of, and they have great instructions.

What really confusing me is the bass works with the grey and pos connected, but I have a feeling it's not as good for noise. I tried contacting nord about this several times to try to understand what the grey wire is, but I haven't gotten a response.

On the flip side, It may not matter. We can flip pos and neg on both pickups with no problem I'm aware of, I'm wondering if it even mattes .

Nords do mention the Audere, but also mentioned buffered. I know the east falls into the active, buffered part, but I don't know if it falls into Audere territory wiring wise.

Would the bridge ground be a good location or be considered common or the ground leading to the battery ?

I

 

[Alex Masters]

You can use the output jack ground as a star earth, or buy a solder lug and screw it into the copper shielding or shielding paint in the cavity and then connect it to the output jack ground. If you can, its best to have all grounds from cavity shielding, bridge and pickup grounds connecting to a single point (star grounding).

 

[ctmullins]

Okay, after taking a peek at Nordstrand's documentation, here's the deal:

Black and white are the coil start/end wires. This is what generates the signal.

Gray is a shielding wire.

So the gray should ALWAYS go to ground. Period. For noise rejection.

For the black and white signal wires, follow the preamp maker's instructions.