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Reverse engineering vintage Haz Labs pre

#21
AgingEngineer said:
Just a quick update. Tonight I ran a few tests to see if I could measure the harmonic overtones coming out of this build. Input is a sine wave at 1kHz and 2kHz, and the output run through an FFT to see the frequencies produced. Then I swapped out the LF442CN that I am using (what was in the old Haz preamps) for a LF412 and TL072 just to see what kind of different the other chips would make in the same circuit.

This is not a comprehensive set of tests, but it does seem to show the LF442CN generates more even harmonics whereas the other two generate more pronounced odd harmonics.

Next up... some A/B audio tests!
View attachment 4666478 View attachment 4666479
Click to expand...
Good post.

I think, you are on somewhat.

About two or three years ago I tried the LF442 in my NS-2O Bass. It was quite disapointing to notice how the NS-2O did lost its "organic" and "airy" sound with LF442 (instead of the stock TL072).
Even in the bandcontext the difference was clearly noticeable.
The NS-2O cuts noticeable better through the mix with the TL072.

I think what you try to describe as kinda "exciter-like added overtones", these "overtones" are all gone on my NS-2O with LF442.
With TL072 there is a pretty nice overtone spectrum present that is noticable missing with the LF442

edit,
in LT-spice modelling there was no audible difference detectable for the Hazlab schematic between LF442 and TL072.
 
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#24
AgingEngineer said:
This is not a comprehensive set of tests, but it does seem to show the LF442CN generates more even harmonics whereas the other two generate more pronounced odd harmonics.
Click to expand...
In first instance it means that LF412 and TL072 can supress THD that arrives from nonlinear and also asymmetrical gain characteristic of components more effectively than LF442.
Asymmetrical gain curves applies in first instance to even order harmonics "distortion" .

In second instance it means that LF412 and TL072 can all kinds of THD (even and odd order harmonics) supress way more effectively than the LF442 cause the levels of all measured harmonics are way smaller.

The LF442 is an old style low power OP amp that draws little current consumption.
This op-amp was rarely (if ever) used for HiFi application.

TL072 was more common in HiFi, but sucks some current. Although TL072 sucks some current the op-amp was often seen on on board EQ electronics placed in musical instruments made in Japan.
Such as it is in my USA NS-2O Bass where the Hazlab board was made under license in Japan.

LF412 sucks even some more current than TL072. The LF412 specs seem to be very good, but too much of current consumption to be used as on board electronic op-amp.
 
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#25
byacey said:
Probably because the spice models gain bandwidth product are identical for both opamps, even though obviously, they aren't the same.
Click to expand...
Somewhat unlikely.
At the one hand side gain bandwidth product is often way to overthinked in regards of LF requirements (20kHz).
Beyond 10kHz there is only little harmonic levels content present anyway, and that's true even for generic audio program material.
But if we do the math, we do the math for full voltage swing at 20kHz !!!

At the oher hand side, if reduced gain bandwidth product was the real reason for noticeable "worse" sound with LF442 versus TL072 than the LF442 gain bandwidth product must be real crap, and accordingly unusable for nothing.

Some HiFi follks swap the TL072 for something "special HiFi" such as Burr Brown that sucks nearly 10 times the current what TL072 does.
 
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#26
I'm very thankfull to @AgingEngineer for his post #8

The different THD spectrum of LF442 vers TL072 is a pretty good key to me to comprehent better WHY TL072 provides a more "organic" sound with my NS-2O Bass versus LF442
The TL072 leaves the pickup sound rather "untached" while the LF442 may cause some "unwanted" colering.
With the LF442 I don't see a strong 2nd harmonic over 3rd harmonic that could me bring to something such as a "warmth" respectively tuby like and musical colering.
While with TL072 the level of the Harmonics stays rather small, and may remain in a rather inaudible range of level
 
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#27
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.
 

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#28
AgingEngineer said:
This journey was strictly to:
  1. Determine what made the old Haz preamp unique,
  2. ...
Click to expand...
Same intention on my side.

Once I was asked in a German forum to run a LT-Spice modelling for the HazLab, and I did it.
The modelling I once did was based on this schematic.
upload_2022-4-24_1-37-1.png


and which seems to be the same schematic as the one you uploaded in #27 (btw, thanks for uploading).


There are same deviations noticable to your previous schematic you have uploaded, and that you have reverse engineered by pictures.
Most of deviations are of no concern and don't hurt anything, except for C that determines the center for the active bass filter.
Althogh the center might be shifted at some content, the deviation is nothing to talk home about, if it was noticable anyway.

One resister in the treble filter is missing in this schematic but, it doesn't hurt the treble filter response in a noticable way.



Besides the stock Japan made HazLab which is in my NS-2O I have got a mighty mite clone (I think it is a mighty mite) that I purchased some time ago for a couple of bugs.
It has the TL062 low power on it.
I have got a EU Spector that has the EMG BTS 2 Band control in it.
Although I have got the "clone" in spare I have got no intention to set this preamp into my EU spector. The BTS fits very well to the sound of the EU spector and there was absolutely no benefit soundwise if I woulld do an Haz-clone"upgrade".
Furthermore, the treble of the Hazlab is little bit more "agressive" to the mids versus BTS (due to some lower number for the center) and thus likey would in total not well fit to the EU spector which basic sound is anyway quite "snappy"


The classifieds are full with upgraded EU spectors and advertised by words such as in the form like:
"The HazLab upgrade in the EU spector brings this bass as close as possible to a USA made spector..."

Personally I think most part of all these sellers should better write the following words, if they really would want to tell the hole story:
"I did spend a lot of bugs to get the original HazLab to upgrade my EU spector, just to upgrade the bass soundwise as close as possible to a USA spector.
But I had to experience the hard and expensive way that it don't works this way. It hasn't changed a lot to the (EU spector) soundwise with the USA HazLab in it!


AgingEngineer said:
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.
Click to expand...
If your bass guitar provides a clean basic sound, you'll get a clean sound back, no matter what kind of preamp was used as board electronic.
Different filter settings may tweak the basic sound of the bass guitar a tiny little bit, however its basic sound charateristic will still remain as is, no matter what the preamp is.
Some folks sometimes think there could be something "magic" with a 2 band EQ. At any time there were way different filters than a 2 band EQ neccessary to "twaek" the basic sound of an instrument.

A couple of years ago I played a USA NS2 in a music store that had an Aguilar 2 band EQ in it. And interestingly this USA NS2 did push the typical USA Spector growl the same way as if it had been a Hazlab inside, but it wasn't!

The USA Spector grwol is already there with the EQ in flat position, and its even more of growl present to the sound with bass/treble digged in from any(!) 2 band EQ control.
To the typical USA Spector growl it doesn't matter which EQ was used.
I have got an USA spector and an EU spector, my EU spector is a transission model, solid maple wings, dot fret markers, SS logo.
Both basses are nearly the same but, the fret wood is different, that's where the difference in sound mainly comes from!

AgingEngineer said:
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.
Click to expand...
yeah, do it, its nothing but a couple of bugs you have to spend, and some time of course!
 
#30
DownUnder_Funk said:
Very interesting thread! Keen for updates and sound clips
Click to expand...

I received the PCB's from fabrication a couple weeks ago and have soldered in a few units for testing. The first one is going into my old Schecter Omen Extreme 5 bass which has EMG 40DC pickups and the EMG BTS system. I opted to keep using the EMG blend and volume pots and wire them into the PCB. The other modification I made was to wire the Bass and Treble pots to only sweep from flat to boost as I only tend to use boost when I want to make a tonal change.

Here are a few pictures of the fully populated PCB, and some diagrams for how it was wired in.

I have to admit that this old Schecter sounds amazing now! I used to love how it looked but hated the sound, and now it's got that "bite" I'd been trying to find. Next up, some before and after sound samples.

I am also thinking an interesting experiment might be to temporarily the Spector (Rebop 5 with EMG pups) so the pickups drive BOTH my PCB and the EMG preamp for comparison.
Boost Only Modification.png EMG Blend and Master.png LHZ-01 in Schecter.png LHZ-01 PCB.JPG
 
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#31
Sorry for the delay in following up on this thread, it's been a busy year! Here's a YouTube clip of how it sounds in my 2009 Spector Rebop DLX 5:

For techies, I've posted a deep dive into my journey of creating this preamp here: [Invalid or Expired Link Removed]

I am still very early in the "beta test" phase getting feedback from players who are able to objectively compare this preamp to an original HazLabs unit. The journey continues...
 
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#35
Sounds great on my phone. I'll have to listen to it through headsets later tonight. One of the things I've found in swapping EMGs for Haz clones of various types is the upper midrange is always more pronounced in the Haz. The distortion you get from the preamp itself happens here, while the low end remains clean and punchy. Also, the center frequency for the treble control is much lower on the Haz than the BTS/BQC, even with the dip switches set up/up. Great project!, dude!
 
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#36
fibz said:
I second that. After a short trip over the Atlantic, I was able to install one of the preamps in my „SoundCloud“ Euro 4LX and tested it today in a session. I think this preamp is awesome.
I’ve added a sample to my preamp database:
Euro 4LX LHZ-01 EMG P4Jr Boost
Click to expand...
From all what I can hear, I think your Euro 4LX sounds still like a more standard Euro 4LX, no matter what preamp was actually installed.
Personally I think, from all what I can hear at soundcloud sample, your Euro 4LX sounds still more close to my NS4CRFM that still has the BTS installed.
However my NS2-O does sound noticeable different!
 
#38
ThisBass said:
I can only speak for the BTS, with proper setting of the treble response DIP-Switches you may come very close to the Haz treble shape and also its "lowish" center.
Click to expand...
I just swapped out a BTS in my NSJH5 for a two board SNC I happened to find here in the classifieds. Having been able to judge them back to back I can confidently say they're close, but the SNC Haz clone has a lot more upper midrange and a lot less sizzle. To be fair, I always liked the Up/Up setting on the BTS, which is the lowest frequency for the treble. The other thing is the BTS is a very clean preamp. The SNC Haz clone has almost a built- in overdrive that only affects the higher frequencies, so your low end remains punchy and clear. I think a BQC with the sweepable mids might come closer.
 
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#39
AgingEngineer said:
Sorry for the delay in following up on this thread, it's been a busy year! Here's a YouTube clip of how it sounds in my 2009 Spector Rebop DLX 5:

For techies, I've posted a deep dive into my journey of creating this preamp here: [Invalid or Expired Link Removed]

I am still very early in the "beta test" phase getting feedback from players who are able to objectively compare this preamp to an original HazLabs unit. The journey continues...
Click to expand...

In first instance I do clearly notice more of bass boost with LHZ-01 vers the BTS.

The BTS bass boost is equal to roughly +10dB while the HAZ is about +14..15 dB.

The treble content in total sounds very close, no "overload" artifacts to be audible for the treble content, neither on LHZ-01 nor with the BTS.
 
#40
VeryTallBassist said:
I just swapped out a BTS in my NSJH5 for a two board SNC I happened to find here in the classifieds. Having been able to judge them back to back I can confidently say they're close, but the SNC Haz clone has a lot more upper midrange and a lot less sizzle. To be fair, I always liked the Up/Up setting on the BTS, which is the lowest frequency for the treble. The other thing is the BTS is a very clean preamp. The SNC Haz clone has almost a built- in overdrive that only affects the higher frequencies, so your low end remains punchy and clear. I think a BQC with the sweepable mids might come closer.
Click to expand...
No, if there was some treble "overdrive" baken in, you'd notice it very clearly as nasty distortion.
That's the way how it is, no myth involved.

There is another thread here on TB regarding this "overload" myth and that clearly demonstrates that there is no treble overload present to the HAZ schematic nothing at all.

If any then at least the (old school) LF442 OP-Amp may have some coloring influence to the total sound. Once the LF442 was swapped for a TL072 (for example), then the magical HAZ sound is widely gone.
 
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