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Reverse engineering vintage Haz Labs pre

#361
AgingEngineer said:
So true! Theory is great on paper, but it rarely inspires. Some of the best stuff came from people who were just single-mindedly doing their own thing to please themselves!
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Absolutely true.
In the '80's and '90's of the past century there where only a few folks/engineers that tried to design SS tube simulation schematics.
Those folks where frequently blamed by "experts" that it never will work with satisfying outcome to the listener.
Yet it works. The outcome of those SS tube simulation may not hit perfectly "tube" yet may sound similar pleasing from a listener perspective.
Personally I think there is way to much confusion all around whenever THD numbers are discussed. Its kinda skunkwork to (frequently) mention that a couple of harmonics (two or three of them) down below -40dB do hardly contribute to the (total) perceived sound texture.
Most of the time crest numbers of music program material in question was pretty obsolete in discussions, just the same way as harmonic density vers. frequency bandwidth are rarely discussed. Most of the time we see stupid sine sweep evaluations instead of an "real word" evaluation.
 
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#362
AgingEngineer said:
You know what's funny? People had been asking me about a pedal version for a long time, and my default reply was that I didn't want to get into the pedal business.

Not because I didn't want to make one, I just didn't think there was much of a market for it with all the really excellent pedals out there. Then I took the Fender to rehearsal one night and ended up spending a lot of time futzing with my settings to get it to sit in the mix like the Spector did. That's when the "aha" light went off: that's why so many folks were asking for it!
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Funny, Sheldon started with a pedal now you came around it was KILLER at rehearsal man .
 
#366
MPU said:
Does replacing TL072 with MC33172 need any modifications? If I understand correct they have same pinout. Am I right?
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If you can still find the MC33172 in DIP format, the pinout is identical so the MC33172 will drop in with no modification.

However, trying to find the DIP version from AUTHORIZED distributors is difficult. Factories have been moving to SOIC (surface mount) and no longer producing the DIP package. If you search for MC33172 you'll find a lot of vendors, but they'll be small sites and Amazon/eBay sellers selling small quantities at an obscene markup.

I would be VERY cautious about buying opamps from any vendor except factory authorized distributors at this point. There is a huge market for out-of-production chips, and a ton of factories overseas churning out lookalikes that are just cheap common opamps despite what is printed on them. You have no way of knowing if you are getting the real thing unless it comes from an authorized source.

If you can't find an MC33172 in DIP format, you can purchase the SOIC version from any authorized distributor, then solder it to a SOIC to DIP adapter like this one: https://www.amazon.com/dp/B07VHJRMHZ. To mount it to the board, I'd used breakable single-row header pins like these: https://www.amazon.com/dp/B06ZZN8L9S

That's an ugly solution, and not something I'd do on a production board, but it does give you an option to swap out the TL072 on existing boards.
 
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#367
bigbottomend said:
Click to expand...


Awesome! This makes me realize that I should do a proper video on the HAZard LAMPS to explain what it was designed for, walk through a comparison of bypass vs flat EQ, show the EQ sweep, and how it impact dynamics.

The problem is that I enjoy making videos and sharing what I've learned, but can't stand to watch myself. Every "um" and "ah" and goofy expression as I am apparently looking to the sky for words I just can't find, and I find my finger hanging over the delete key for the whole project.

If I had mad money, I'd hire an actor to play me in my own videos.
 
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#368
New home!
20240426_145408.jpg
 
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#369
AgingEngineer said:
Awesome! This makes me realize that I should do a proper video on the HAZard LAMPS to explain what it was designed for, walk through a comparison of bypass vs flat EQ, show the EQ sweep, and how it impact dynamics.

The problem is that I enjoy making videos and sharing what I've learned, but can't stand to watch myself. Every "um" and "ah" and goofy expression as I am apparently looking to the sky for words I just can't find, and I find my finger hanging over the delete key for the whole project.

If I had mad money, I'd hire an actor to play me in my own videos.
Click to expand...

would love to see that video! Just aim the camera at the pedal and cut to the chase, it would be awesome!
 
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#370
bigbottomend said:
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That's very interesting kind of a sample cause the "unprocessed" sound (LHZ pedal in bypass mode) sounds as if there was PU resonance texture missing.

Ok, tried to do my my very best and did the following.
I downloaded the file from SC with JDownloader. The mp3 is of lowish 128kbit/s that I converted into WAV 44.1kHz.
I did split the file into two parts, the raw program material as part #1 and LHZ processed program material part #2

The raw program material part #1 was run into LT-Spice HAZ emulation with Treble and Bass at full boost.

In the next step I added a Pickup resonance emulation to the raw program material part #1 before the signal was again feed to the HAZ emulation in LT Spice.

raw program material part #1
- P-PU

program material part #2 processed by LHZ pedal
- P-PU_LHZ-pedal

HAZ LT-Spice emulation of part #1
- P-PU_LT-Spice

Pickup resonance emulation that was feed into HAZ LT-Spice emulation of part #1
- P-PU_LT-Spice_PU-Res

Conclusion
The LT-Spice emulation of the raw program material part #1 sounds a little bit boring vers. "real world" recording LHZ-pedal sound part #2.
Once there was some PU-resonance added to the raw program material before the signal was fed into the HAZ LT-Spice emulation the situation does change dramatically.
The emulated sound does come very close to the "real world" sound that was recorded with the LHZ-pedal.
The LHZ-pedal sound may sound a little bit more aggressiv at the top range of bandwidth vers. emulated sound. This remaining deviation might be aligned (at least at some content) with fine tuning by some variation of emulated pickup resonance and/or its peaking at resonance.
Yet I leave it as is. I did the emulation "on the fly" and to be honest, the emulated sound "as is" may sound (ironically) a little bit more pleasing to the ears than the recorded real world sound.

Download the PDF file "P-PU" and rename file extension "PDF" into "ZIP" to get access to the WAV files.


edit:
posts like this may read just as rant. Rather than rant those posts like this are rather meant to contribute to comprehension.
Me myself was very surprised that "adding" some missing pickup resonance may (strongly) help to achieve an intended sound goal. Interestingly it has nothing to do with shelf filters of the HAZ schematic in question nor anything to do with harmonics when digging in hard. Eventually it's nothing but a total different animal that contributes to the perceived "sonic" sound in question as is.
 

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#373
AgingEngineer said:
Very cool!!! What do you use to manage switching the pedals in a rack setup like that?
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Super simple. The flange, chorus and dist go into the sansamp which then goes to 2 destinations. 1) to the new haz pedal and then into a lehle splitter and into 2 amps, svt ii and svt 4pro. The sansamp is for drive if I want it. The pedals I will turn on or off as needed, no switching. 2 sansamp parallel out (unaffected by sansamp) goes to the gk preamp pedal and that is my FOH sound.

This is something I've developed over time and catastrophic failures. The foh sound is independent of the stage sound so changing my amp sound won't affect foh. It's a constant. Next, if my amp goes down, the other one is also on (2 810 cabs) so I won't loose sound. I keep a touch of bass in my Monitor for this reason. If I happen to use 1 cabinet, the 4pro is a back up. I then only have to move the speaker cable and I'm good.
 
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#374
wolfkeller said:
...and into 2 amps, svt ii and svt 4pro.

The foh sound is independent of the stage sound so changing my amp sound won't affect foh.
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Whenever I played my SVT on stage I did insist on speaker level DI signal that was picked up at power amp out of the SVT.
The main reason for carrying it out this way, yeah it's a very sonic and unique sound that involves lots of interaction of tube power amp with the loudspeakers, quite hard to achieve similar FOH sound with any other kind of technique.

There is nor black nor white but thousand shades of grey. Some players may not want to have svt sound at FOH while other players (such as me) may insist on it.
 
#375
ThisBass said:
Whenever I played my SVT on stage I did insist on speaker level DI signal that was picked up at power amp out of the SVT.
The main reason for carrying it out this way, yeah it's a very sonic and unique sound that involves lots of interaction of tube power amp with the loudspeakers, quite hard to achieve similar FOH sound with any other kind of technique.

There is nor black nor white but thousand shades of grey. Some players may not want to have svt sound at FOH while other players (such as me) may insist on it.
Click to expand...
I'd like to but in my experience, venue provided soundmen are not the best to work with
 
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#378
Hi Everyone!

Well, I did finally carve out a bit of time to try and get the LHZ-02 installed. My starting point bass was an LTD AP-4, which already comes with EMG's. While this isn't my first rodeo, this will be my first install of any preamp that I just can't get to work. I'm sure I'm doing something wrong, but I've run through the installation instructions back and forth and I can't figure out what I'm doing wrong. It's not an overly complicated install, so I must be brain farting somewhere.

1. I ended up buying the EMG stacked volume pot recommended earlier in this thread.
2. Signal flow is both pickups into the stacked volume pot, and then the output of the volume pot into the input of the LHZ-02.
3. I didn't have quick connect cables for everything, so there are a couple of instances where I had to get creative and solder directly to the pins of the board. I used heat shrink to isolate everything and it seemed to check out. If necessary I can source quick connect cables for those and start over.

When I plug the bass in, I have absolutely zero sound. No buzz, no hum, nothing. No response to tapping on the pickups with a screwdriver, etc. Again, I'm not sure what to fiddle with because the install isn't overly complicated, so I'm not sure if I'm shorting everything out somewhere or maybe I don't have battery power flowing through the circuit properly? Anyway, I can take better pictures if necessary, but I'd love some advice if anyone has some to spare. Thank you!

IMG_4381.jpg IMG_4380.jpg IMG_4379.jpg IMG_4378.jpg
 
#380
bigsnack said:
While this isn't my first rodeo, this will be my first install of any preamp that I just can't get to work. I'm sure I'm doing something wrong, but I've run through the installation instructions back and forth and I can't figure out what I'm doing wrong. It's not an overly complicated install, so I must be brain farting somewhere.
Click to expand...

Good morning @bigsnack! I'm happy to help with this, and you can email me directly via the support email in the installation manual. (Don't want to post it publicly in the forum because it gets scraped by bots and I end up getting flooded with spam.)

A COUPLE QUESTIONS
  1. Can you send me a couple photos showing the output jack connections, and a couple other shots that show how the pickups are connected to the stacked volume pot?
  2. I admit that I do not recognize that particular stacked volume pot you are using... Can you link to the product page so I can see how EMG recommends it to be wired?
SOME QUICK TESTS

Try this to see if we if the preamp and output jack wiring are OK:
  • Unplug the pot from the VR3 connector on the LHZ,
  • With battery connected and bass plugged in, tap the MIDDLE pin of the VR3 connector with your fingertip or a small screwdriver.
    • If you hear noise or clicks, the preamp is working AND the output jack is connected correctly.
    • If there is no noise, then we'll need to look at the output jack wiring.
Usually zero sound issues are the pot wiring before the LHZ (some of the EMG controls have the BLACK and WHITE connections reversed, which is very easy to overlook) or an output jack wiring issue.

In the event that the LHZ has failed (I do test them all before they ship, but accidents can happen!) I'm happy to send you out a replacement unit as well.

If you email me a few more detailed pics and a link to the stacked pot you are using, I'm sure we can get you sorted!
 
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