Reverse engineering vintage Haz Labs pre

[Maidenfloyd]

The secret imho is to rely only on the onboard preamp and leave the amp‘s EQ flat, maybe cut the bass on the amp if you max out the bass of the onboard preamp. That‘s how I do it when I play over my amps in practice room which are a GK 400 and a Mesa M6.

Thank you

 

[grimmchaos]

I was thinking that as a stompbox, the LHZ would just need the Bass and Treble pots (linear 100k, center detent), a button that acts as a bypass & power (assuming this is not like an effect pedal that you'd be kicking on and off during a song: it'll always be on or off), In and Out jacks, and and LED to let you know it's on.

There'd be no volume control on it at all: you'd rely on whatever volume pot is on the bass just like if the preamp was built into the bass.

I'm also designing a version with a pre and post gain stage that can push the core preamp harder (this might be a neat OD for guitar?) and also allow you to adjust the output volume. For this version, the pre gain stage will use the feedback loop for gain control. That way I can just select a single pot that works for the gain circuit instead of trying to determine which pot value will be best for whatever pickups / electronics are in the bass.

(I know that's a hot mess of a reply!)

Your first version is exactly what I'd be looking for (and what I may try doing myself).

 

[AgingEngineer]

We just hit a milestone last week: the 100th LHZ preamp was built! To celebrate, we will select one of our existing customers to receive S/N# 100 completely free of charge to upgrade another Spector in their arsenal, or choose to have it shipped to anyone of their choosing.

The winner will be notified via the store account used to purchase their preamp, TB forum account, or email if they have been in direct contact.

 

[Fritter]

I've got a cheap short-scale bass that I upgraded to EMG Geezer P-J passive pickups and I'm wondering about adding an LHZ to a) boost the output and b) add some magic Spector sound. All your schematics/drawings show EMG active pickups feeding into the blend control and then into the LHZ. Will the LHZ work with my EMG Geezer pickups and, if not, can the gain of the first stage be altered by changing components?

What I'm not clear on is the output level difference between the EMG active and my passive pickups and what difference that will make to the performance of the LHZ.

 

[AgingEngineer]

Will the LHZ work with my EMG Geezer pickups and, if not, can the gain of the first stage be altered by changing components?

The LHZ preamp works very well with any pickups, passive or active. I know there are several users that have installed it with the EMG Geezer PJ set. I can review my conversations to see which clients those were, and if they are TB users I'll see if they are OK with me passing along their name to you.

EMG is not terribly helpful when it comes to difference in output volume between active and passive pickups. They specify an output voltage for active, but not passive. It's easy to assume the active are a LOT louder, but I don't think that is a valid assumption. (For example: https://www.talkbass.com/threads/hey-i-thought-active-basses-were-louder-than-passive-basses.892343/) For example, if I thump the E string I'll get about a volt on the oscilloscope trace from an active EMG P pickup. For a passive EMG P pickup, I'll also get about a volt. (It might be slightly less, but not significantly so.)

So the output is about the same, which means they are driving the preamp about the same.

The original Hazlabs used the same circuit for both passive and active pickups. The only difference was pots values used for volume and blend, which is totally based on the type of pickup.

I'll attach a drawing I'd recently done for another client (not in the manual yet) showing dual passive with blend and volume.

 

[AgingEngineer]

Oops... forgot to add the ground wire! Since I can't edit my prior post, here's the corrected diagram.

 

[KaraQ]

Sorry if I missed this specific question - is there any functional or sound difference between wiring the pickups & blend control to the board connections ("legacy wiring" in the pdf), vs. wiring the pickups to the blend, then to the board (as in the standard? "spector conversion" drawing that's on the website, but not in the pdf)?

 

[AgingEngineer]

is there any functional or sound difference between wiring the pickups & blend control to the board connections ("legacy wiring" in the pdf), vs. wiring the pickups to the blend, then to the board (as in the standard? "spector conversion" drawing) that's on the website?

Great question! There is no sonic or functional difference at all! The LHZ board simply routes the pickup signals (from PU1 and PU2) to the blend (VR1) and volume (VR3) pots in the exactly same manner that they are normally wired directly.

When I first created the board, my mindset was for it to be a HazLabs with flexible pot mounting options. (Because I had a ReBop and the HazLabs board doesn't quite fit because the pots were in fixed locations on the board.) So instead of mount pot, I just created connection pads for them.

What I learned from clients during the last year is that almost no-one connects the pickups to the board!

Instead, almost everyone connects the pickups to the volume (or volume & blend) pots per the EMG diagrams, then sends the output from the volume pot to the LHZ via two pins on the VR3 connector. Same thing with folks with hard-soldered pots: they leave the pickup wires soldered to the volume pots, then just connect the Signal and Ground from the volume pot to the LHZ via the VR3 connector.

That's why the current revisions now list the Legacy wiring in the back... It's basically for reference: you can wire it up that way, but most people don't.

In practical application it's a LOT easier to keep the pickups wired directly to the pots. (Plus if you love the magic of the EMG ABCX blend control, there is no going back to a standard blend pot!)

BTW: there are several diagrams that are being added to the PDF that should go live this weekend, so that diagram and others will be in the new revision.

Taking what I've learned from clients this year, I am working on a new board design for Q3 of 2024. The new version will reduce the size of the board, and will eliminate the PU1, PU2, VR1, and VR3 connectors to only provide a 2-pin IN connector. This will make it a lot easier to fit into tiny control cavities (looking at the Fender and Steinberger crowd) and easier to integrate as well.

 

[KaraQ]

Great question! There is no sonic or functional difference at all! The LHZ board simply routes the pickup signals (from PU1 and PU2) to the blend (VR1) and volume (VR3) pots in the exactly same manner that they are normally wired directly.

When I first created the board, my mindset was for it to be a HazLabs with flexible pot mounting options. (Because I had a ReBop and the HazLabs board doesn't quite fit because the pots were in fixed locations on the board.) So instead of mount pot, I just created connection pads for them.

What I learned from clients during the last year is that almost no-one connects the pickups to the board!

Instead, almost everyone connects the pickups to the volume (or volume & blend) pots per the EMG diagrams, then sends the output from the volume pot to the LHZ via two pins on the VR3 connector. Same thing with folks with hard-soldered pots: they leave the pickup wires soldered to the volume pots, then just connect the Signal and Ground from the volume pot to the LHZ via the VR3 connector.

That's why the current revisions now list the Legacy wiring in the back... It's basically for reference: you can wire it up that way, but most people don't.

In practical application it's a LOT easier to keep the pickups wired directly to the pots. (Plus if you love the magic of the EMG ABCX blend control, there is no going back to a standard blend pot!)

BTW: there are several diagrams that are being added to the PDF that should go live this weekend, so that diagram and others will be in the new revision.

Taking what I've learned from clients this year, I am working on a new board design for Q3 of 2024. The new version will reduce the size of the board, and will eliminate the PU1, PU2, VR1, and VR3 connectors to only provide a 2-pin IN connector. This will make it a lot easier to fit into tiny control cavities (looking at the Fender and Steinberger crowd) and easier to integrate as well.

Awesome, thanks for the info!

I think I'll probably follow the others with wiring to the blend/vol then to the board - it'll likely be a bit easier, and *should* make wire management a bit easier in the small space of my Ibanez

 

[VeryTallBassist]

Great question! There is no sonic or functional difference at all! The LHZ board simply routes the pickup signals (from PU1 and PU2) to the blend (VR1) and volume (VR3) pots in the exactly same manner that they are normally wired directly.

When I first created the board, my mindset was for it to be a HazLabs with flexible pot mounting options. (Because I had a ReBop and the HazLabs board doesn't quite fit because the pots were in fixed locations on the board.) So instead of mount pot, I just created connection pads for them.

What I learned from clients during the last year is that almost no-one connects the pickups to the board!

Instead, almost everyone connects the pickups to the volume (or volume & blend) pots per the EMG diagrams, then sends the output from the volume pot to the LHZ via two pins on the VR3 connector. Same thing with folks with hard-soldered pots: they leave the pickup wires soldered to the volume pots, then just connect the Signal and Ground from the volume pot to the LHZ via the VR3 connector.

That's why the current revisions now list the Legacy wiring in the back... It's basically for reference: you can wire it up that way, but most people don't.

In practical application it's a LOT easier to keep the pickups wired directly to the pots. (Plus if you love the magic of the EMG ABCX blend control, there is no going back to a standard blend pot!)

BTW: there are several diagrams that are being added to the PDF that should go live this weekend, so that diagram and others will be in the new revision.

Taking what I've learned from clients this year, I am working on a new board design for Q3 of 2024. The new version will reduce the size of the board, and will eliminate the PU1, PU2, VR1, and VR3 connectors to only provide a 2-pin IN connector. This will make it a lot easier to fit into tiny control cavities (looking at the Fender and Steinberger crowd) and easier to integrate as well.

Oh man, so the new version might fit into my Coda 5 Pro that doesn't have rear routing? You, sir, are trouble!!

 

[AgingEngineer]

Oh man, so the new version might fit into my Coda 5 Pro that doesn't have rear routing? You, sir, are trouble!!

Can you send me photos and dimensions of what the control cavity looks like? I'd not had my hands on that model. I've had a surprising number of Fender Jazz players ask if the LHZ will fit, so the goal is to get the dimensions down to fit most of these requests.

 

[VeryTallBassist]

Can you send me photos and dimensions of what the control cavity looks like? I'd not had my hands on that model. I've had a surprising number of Fender Jazz players ask if the LHZ will fit, so the goal is to get the dimensions down to fit most of these requests.

I'll take some pics and measurements tonight. I have a question on this particular bass, which I think is likely not unique to me - the way I have the electronics currently set up I am using a BTC for the stacked bass and treble controls and I have EMG's passive tone control in line with them. It's kind of similar in concept to the Sadowsky preamp with the VTC, only without a preamp bypass. It allows me to set the EQ flat and just use the tone control for a more vintage sound, but if I use them together I can boost the treble and tame the top end just a bit, which is often useful. I would imagine that this would be doable with the LHZ if the tone control was installed in between the volume control and the input of the preamp, would it not? If that's the case, then maybe a stacked tone control knob would be a good option to offer.

 

[AgingEngineer]

I am using a BTC for the stacked bass and treble controls and I have EMG's passive tone control in line with them. It's kind of similar in concept to the Sadowsky preamp with the VTC, only without a preamp bypass. It allows me to set the EQ flat and just use the tone control for a more vintage sound, but if I use them together I can boost the treble and tame the top end just a bit, which is often useful. I would imagine that this would be doable with the LHZ if the tone control was installed in between the volume control and the input of the preamp, would it not? If that's the case, then maybe a stacked tone control knob would be a good option to offer.

If I am reading this, you have the BTC and the passive tone controls in series like this: Pickups --> Blend --> Passive Stacked EQ --> BTC Stacked EQ --> Output. Is that correct?

Yes, this will work with the LHZ. I believe there are one or two clients who have put an EMG VMV Variable Mid control between the volume and the LHZ, which is the same concept.

I've had several folks ask about a stacked Bass & Treble pot this year, so I'm thinking maybe it's time to reach out to the mfg to see what it would cost to have a small lot of these made!

 

[VeryTallBassist]

If I am reading this, you have the BTC and the passive tone controls in series like this: Pickups --> Blend --> Passive Stacked EQ --> BTC Stacked EQ --> Output. Is that correct?

Yes, this will work with the LHZ. I believe there are one or two clients who have put an EMG VMV Variable Mid control between the volume and the LHZ, which is the same concept.

I've had several folks ask about a stacked Bass & Treble pot this year, so I'm thinking maybe it's time to reach out to the mfg to see what it would cost to have a small lot of these made!

Passive HPF but yes, that's it exactly. Cool!

 

[VeryTallBassist]

Can you send me photos and dimensions of what the control cavity looks like? I'd not had my hands on that model. I've had a surprising number of Fender Jazz players ask if the LHZ will fit, so the goal is to get the dimensions down to fit most of these requests.

Control cavity is 5"L x 1.25"W x 1.25"D.

 

[AgingEngineer]

@VeryTallBassist Thank you for posting the dimensions and photos! That is a tight cavity.

Last night I was working on mockups for the new design using 90-degree pin headers so POWER and INPUT connectors are on one side, and the OUTPUT connector is on the opposite side. This gives me a board that is approximately 1.75"L x 1"W with the the tallest cap making the board slightly over 1/2" high from back to top of the tallest cap.

That should be able to lay flat on the bottom of that cavity.

Still a work on progress...

 

[KaraQ]

Awesome, thanks for the info!

I think I'll probably follow the others with wiring to the blend/vol then to the board - it'll likely be a bit easier, and *should* make wire management a bit easier in the small space of my Ibanez

Picked up my new pre-amp from my package drop today, looks great! Looking forward to getting it installed


Looks like I've got a couple of options for placement:

This way has very little clearance with the blend, but would let me put the battery back in its normal place

This second option puts the pre-amp in the battery's spot.
I'll need some spacers I think, to help keep it clear of the pickup wiring (probably the same foam I use under pickups), and the battery will have to essentially lay on top of the pots (in its sleeve), until I can get a battery box installed.

But, I'm thinking it will be the better way....

 

[AgingEngineer]

This second option puts the pre-amp in the battery's spot.

Another (unconventional) option would be to wrap it in a foam sleeve and stand it up between the two rows of pots. If you turn the bass and treble pots slightly so the terminals are facing toward the barrel jack there should be plenty of clearance in the middle. Then the battery can sit in its traditional space.

 

[KaraQ]

Another (unconventional) option would be to wrap it in a foam sleeve and stand it up between the two rows of pots. If you turn the bass and treble pots slightly so the terminals are facing toward the barrel jack there should be plenty of clearance in the middle. Then the battery can sit in its traditional space.

Interesting idea!

I'll see how that might work when I get the chance to work on it. Hopefully Sunday!

Also, using your foam sleeve idea, maybe put it component side down on top of the pots?, where I was thinking of putting the battery.


Part of the fun of doing custom/non-standard mods is figuring out how best to make it work

 

[ColdEye]

Anyone use this on a Warwick? Lol I have a Warwick that needs pickups and a preamp, probably going to try this (vol/vol/stacked B/T as it only has 3 pot holes).