Reverse engineering vintage Haz Labs pre

[AgingEngineer]

@takeout, I don't see a problem with that. The LHZ really doesn't care what is in front of the input, so I don't foresee any adverse tone issues. This what what the wiring generally looks like with with a standard 4 pot (vol/blend/bass/treble) installation with bypass. I assume you'd put the passive tone control between the Blend and volume. If so, with the bypass in position 1 the signal chain would be:
Pickups --> Blend --> Passive Tone --> Volume --> LHZ --> Output

With the bypass in position 2 the signal chain would be:
Pickups --> Blend --> Passive Tone --> Volume --> Output

If you really wanted to get creative, you could get a 3PDT switch and wire the passive tone so it was only in-circuit when the LHZ is bypasses.

 

[PhishPhan22]

Ssoo to revive this a little I have the Spector euro LT that had the first darkglass tone cap in it. Not a fan. It’s not getting that high end like cut as is talked about here I played on the new American Spectors a wow loaded with EMGs an haz I play jam style music like goose. Moe. that stuff. I have Bart pickups I’ve been wondering if changing to
The Bart NTMB would be a huge diff an worth it or maybe going for the cheaper version of the haz I’ve already paid enough retail I don’t want to go to deep into it more but I don’t like that preamp

 

[fibz]

Ssoo to revive this a little I have the Spector euro LT that had the first darkglass tone cap in it. Not a fan. It’s not getting that high end like cut as is talked about here I played on the new American Spectors a wow loaded with EMGs an haz I play jam style music like goose. Moe. that stuff. I have Bart pickups I’ve been wondering if changing to
The Bart NTMB would be a huge diff an worth it or maybe going for the cheaper version of the haz I’ve already paid enough retail I don’t want to go to deep into it more but I don’t like that preamp

Sooo, what‘s the question?

 

[PhishPhan22]

Hahab I ended up not finishing that post. lol funny. But it was guna be will how much do onboard preamp swaps help? I spent a goood amount on this bass already so
Idk if I want or should put a new pre in. BUT if it really would make a significant diff on tone and get me there is would the Bart NTMB be worth it? Or another onboard pre I only say the Bart pre cause it seems to have all the features I’d want. An I say the NTMB cause the pups that came on my spec were the Barts

Sooo, what‘s the question?

 

[fibz]

But it was guna be will how much do onboard preamp swaps help?

Help? More like „some add a certain flavor“.

BUT if it really would make a significant diff on tone and get me there is would the Bart NTMB be worth it?

That I can’t tell as I only had experience with a NTBT in a Willis fretless.

all the features I’d want

Like what?

An I say the NTMB cause the pups that came on my spec were the Barts

That is of course your choice. But there’s no rule to get the same brand, Spector also combined different pickup brands and preamps.

 

[Hillie]

Just ordered one for my Euro 5 LX, looking forward to install it! Saw I missed out on the discount code... oh well.

edit: Regarding the EMG balance circuit/pot, is there any issue with using the ABCX vs the ABC? Their spec sheet seems to indicate the ABCX is a bit better with power consumption...

 

[AgingEngineer]

Just ordered one for my Euro 5 LX, looking forward to install it! Saw I missed out on the discount code... oh well.

edit: Regarding the EMG balance circuit/pot, is there any issue with using the ABCX vs the ABC? Their spec sheet seems to indicate the ABCX is a bit better with power consumption...

Thank you! I just saw this drop in and it will ship out tomorrow.

The ABCX is the blend control I recommend for all installations using active pickups. The EMG website differs slightly from the installation docs, and implies that the ABCX is for the X-Series. The reality is that the ABCX is used for ALL active pickups (classic or X-series) whereas the ABC is for installations using passive tone controls OR that have BOTH passive and active pickups.

The main difference is that the ABCX buffers the signal AFTER the pot (which is 25k) and the ABC has buffers BEFORE the pot.

 

[Hillie]

Thank you! I just saw this drop in and it will ship out tomorrow.

The ABCX is the blend control I recommend for all installations using active pickups. The EMG website differs slightly from the installation docs, and implies that the ABCX is for the X-Series. The reality is that the ABCX is used for ALL active pickups (classic or X-series) whereas the ABC is for installations using passive tone controls OR that have BOTH passive and active pickups.

The main difference is that the ABCX buffers the signal AFTER the pot (which is 25k) and the ABC has buffers BEFORE the pot.

Great, thank you! Nothing to be concerned about then. Looking forward to getting the LHZ, just need to order the appropriate EMG components now.

 

[fibz]

Thank you! I just saw this drop in and it will ship out tomorrow.

The ABCX is the blend control I recommend for all installations using active pickups. The EMG website differs slightly from the installation docs, and implies that the ABCX is for the X-Series. The reality is that the ABCX is used for ALL active pickups (classic or X-series) whereas the ABC is for installations using passive tone controls OR that have BOTH passive and active pickups.

The main difference is that the ABCX buffers the signal AFTER the pot (which is 25k) and the ABC has buffers BEFORE the pot.

Interesting regarding the buffers. I also used the ABC for two passive Seymour Duncan soapbars and then went into a preamp, if memory serves right, into a BTS. Worked well. It’s somewhat confusing that EMG is marketing these two accessories in that way.

 

[Hillie]

I guess the 2 vs 1 buffers explains the difference in power consumption. ABC is rated at 600uA, 750hr life on a 9V battery, ABCX is rated at 188uA, 2500hr life on a 9V battery, both taken from the instruction PDFs from EMG's site.

Unaware of the reason, I was leaning to the ABCX based on power consumption. Plus it's their "X" series, supposedly "better".

 

[AgingEngineer]

Interesting regarding the buffers. I also used the ABC for two passive Seymour Duncan soapbars and then went into a preamp, if memory serves right, into a BTS. Worked well. It’s somewhat confusing that EMG is marketing these two accessories in that way.

The thing is that the ABC will work perfectly well on a set of active pickups, so you could argue that it is sort of a one-size-fits-all solution. I think most people expect that there would be a clear difference between the two, when the reality is that that there is a lot of overlap between them.

Personally, I'd argue that they should have a selection matrix. Something like this:

 

[Chris Hass]

This is exactly why I was interested in the Haz in the first place: I like the fact that it adds high frequency harmonics, and that that the LF442CN produces more even harmonics as compared to the pronounced odd harmonics from other opamps in the same circuit.

This journey was strictly to:

1. Determine what made the old Haz preamp unique,
2. Find out what it was doing with the high frequency overtones that attracted me to it,
3. Share the circuit and findings with other Haz fans.

I appreciate that @ThisBass enjoys a pristine clean tone, but that's not what I am hunting for.

For me, "clean" preamps are nothing special. All my basses have them. I can get them anywhere. What I cannot get anywhere is that unique sound of the old 9volt Haz 46745 preamp... unless I spend several hundred dollars for an original Haz, or a couple hundred for a clone.

Or, I can build one for under 6 dollars and a little time.

Attached is the reverse-engineered schematic and BOM for any Haz fans that want to build their own.

Looking to build a pedal around this with some added features. Is this the schematic used for your Hazard Lamps pedal?

 

[AgingEngineer]

Looking to build a pedal around this with some added features. Is this the schematic used for your Hazard Lamps pedal?

Good morning, Chris

That drawing is a bit old, and there were a couple corrections made to it after the LHZ went up for retail sale:
1. C1 is 33uF, not 100uF
2. OpAmp was replaced with an MC33172DRG2 (same opamp that Hazlabs is using now)
3. The RING and SLEEVE connections on CN2 are reversed. This drawing shows the battery negative going to the SLEEVE, where it should be going to the RING.

Other than that, this is correct!

 

[Roadstar]

Just had a LZH installed and could not be happier with it. Tones to my ears are so much better than the bts that came in the this Euro Spector. I have a couple of Rex’s I am going to place these in over the next few months.

 

[AgingEngineer]

Just had a LZH installed and could not be happier with it. Tones to my ears are so much better than the bts that came in the this Euro Spector. I have a couple of Rex’s I am going to place these in over the next few months.

That's great to hear and I'm glad you are digging the LHZ!

As I look back to the beginning of this thread on TB, I never would have figured that two years later this post-Covid hobby project would have turned into a business. I very much appreciate you, and everyone else in the community, who have taken a chance on an unknown vendor and taken the time to share your experience. Thank you!

 

[Roadstar]

That's great to hear and I'm glad you are digging the LHZ!

As I look back to the beginning of this thread on TB, I never would have figured that two years later this post-Covid hobby project would have turned into a business. I very much appreciate you, and everyone else in the community, who have taken a chance on an unknown vendor and taken the time to share your experience. Thank you!

You’re very welcome. I luthier believes it to be the best two band preamp he has heard.

 

[fibz]

Happy new year! By now It should be 2025 everywhere. And in the past few weeks I had the opportunity to beta test the upcoming LHZ preamp version. Read on for more …

It certainly came a long way. Back in May 2023 I was browsing through Talkbass looking for some Spector preamps and HAZ clones. In the past I already obtained several HAZ clones used in Spectors, but this preamp was new and looked very promising and I was eager to add it into my database (SoundCloud).
So I contacted Lonnie and got me one of the first LHZ PCBs to play around and was very impressed with its sound.
Fast forward to December 2024 I could witness how many people are enjoying this preamp, over the time the preamp‘s layout evolved further into the new 4.1. This review gives you some insight what’s new.

LHZ 2025​

As we all know (at least those who have followed this thread), the LHZ is a clone of the famed Spector HAZ preamp. The new version stays on the current form factor, meaning a rectangle shaped PCB. Compared to the previous version, the current LHZ is 25% smaller and to the original version, it is even 35% smaller. These figures refer to the footprint of the PCB.

The following image shows a comparison between the first version (green), the current (blue) and the upcoming version. All components have now been changed to SMD parts. As a result, the LHZ is now approx. 30% flatter than before.



Note the heights on the red / LHZ-4 board (bottom right pic, circled) as well as the new angled output Dupont connector. By moving the connector to the middle of the PCB, it makes installation a lot easier as the connector doesn’t take up unnecessary space anymore.

LBCA-02 ACTIVE BLEND​

The newest addition to the catalogue is LHZ‘s active blend, called LBCA-02. The final version will look a little bit different, but the design will be the same.
It has the same functionality as the EMG one (ABCX), has the original pinout and is also powered by 9V. While the LBCA shares many design traits with the ABC-X, it has some tiny mods under the hood (opamp, different filter caps) compared to the EMG one.

It comes with a split shaft pot, making it possible to reuse the pushon Spector knobs from Euro basses.


Left: LHZ Active Blend, right: EMG ABCx/B118 blend.

Sizewise they are the same as you can see. Length, width and depth are nearly the same. The thread is long enough to be used in a Spector bass. This pot works as smooth like the original ABC-X, no drop of volume or whatsoever (no insertion loss).
Have a listen where I pluck a note and sweep the LBCA:

IN THE SPECTOR​

Here’s a pic of the knob side with LHZ pots installed. The one with the brass thread is the EMG one. The leftmost pot is the LBCA blend pot:


In my test bass, a NS-5CR the size-reduced LHZ fits perfectly when installed against the „side wall“. Nevermind the somewhat messy wires, I tried to keep it tidy but that isn’t my strength :-D

On the left there‘s the LHZ LBCA. This pic is only interesting for owners of older Euros where the battery sits together with the pots. For Euros with a separate battery compartment there won’t be any problems with space.
I prefer to have the balance pot in the front position. Others might prefer it where my volume pot is installed. When using EMG (or LHZ) ABC I found it easier to install it in that particular location.

Sounds!​

Here’s a sample played with the above pictured bass. Full details: NS-5CR (Czech SSD), EMG CS (neck), EMG DC (bridge), LBCA blend pot, LHZ-4 preamp, treble set to 100%, bass set to 75%. Strings are D’Addario Pro Steels, fingerstyle. The song, you may recognize it.



Still that growly HAZ sound! Compared to the ABC-X the LBCA works a bit better with the LHZ. This is due to the mods Lonnie did in the blend pots PCB.

TL;DR​

• Smaller, flatter board makes it easier to install in most, even cramped cavities
• Same great HAZ tone!
• Great quality pots
• LBCA active blend pot is great new product and works as expected and even better!

 

[fibz]

PS: additional pics. First one shows a comparison between the LHZ, the Darkglass Tone Capsule and a Tonepump.
Second a closeup pic of the LHZ.

 

[Arthur U. Poon]

Thank you! I just saw this drop in and it will ship out tomorrow.

The ABCX is the blend control I recommend for all installations using active pickups. The EMG website differs slightly from the installation docs, and implies that the ABCX is for the X-Series. The reality is that the ABCX is used for ALL active pickups (classic or X-series) whereas the ABC is for installations using passive tone controls OR that have BOTH passive and active pickups.

The main difference is that the ABCX buffers the signal AFTER the pot (which is 25k) and the ABC has buffers BEFORE the pot.

Hi, Lonnie! I just received an HL-1 pedal for Christmas, and I’m going to be using it mostly with my Spector NS4CRFM, which has Original Recipe active EMG PJs with an EMG BTS, and with my Spector Euro 6LT, which has active EMG X-Series PJs with an EMG BTS.

I see that you recommend the EMG ABC or ABCX. Even though both basses have BTS’ and active EMGs, do I still need an ABC or ABCX?

 

[Hillie]

Hi, Lonnie! I just received an HL-1 pedal for Christmas, and I’m going to be using it mostly with my Spector NS4CRFM, which has Original Recipe active EMG PJs with an EMG BTS, and with my Spector Euro 6LT, which has active EMG X-Series PJs with an EMG BTS.

I see that you recommend the EMG ABC or ABCX. Even though both basses have BTS’ and active EMGs, do I still need an ABC or ABCX?

ABC and ABCX are EMG's on board blend circuits, so unless you're looking to modify your bass, rather than just use the pedal, AND want to go to vol/blend instead of two volumes, you don't need it. The blend circuit is needed if you want to have vol/blend on the bass.