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Reverse engineering vintage Haz Labs pre

#381
bigsnack said:
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!

View attachment 5454337 View attachment 5454338 View attachment 5454339 View attachment 5454340
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What about the jack‘s wiring? Can we have some close up pics as well?
 
#384
fibz said:
Good to hear! Have fun with it! Also it’s the most common error.
Click to expand...

You are right, it is the #1 support call I receive. I'd been trying to do a troubleshooting video for battery drain for the last few months, and finally had time to record one. (OK, I also dislike recording myself, so there's another reason.)

I'll post it here in case it helps anyone.
Battery Drain Diagnostics with Active Preamps:
 
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#385
A couple more projects on the bench this weekend... I've acquired a set of Ken Smith and Steinberger Haz preamps that will go through the reverse engineering process, and will also be used to capture baseline test data from for later comparison.

I also made a random discovery. Folks that have followed this thread for a long time know that I'd moved from using Bourns pots (which I am a huge fan of!) to having custom pots manufactured for the LHZ preamps. As I was putting away some older parts I found an unopened box of Bourns pots I'd ordered from the authorized distributor. The box had the original manufacturing source information on it. It turns out that Bourns pots are made by the same factory I am using for the LHZ pots. Who knew?
Preamps.png
 
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#386
Forgive me for asking but I got a b quad 5 neck on. A peavey grind 5 U.S.A. body with 4 controls

I’ve changed the stock preamp to a BQC but I’m interested in the haz lab 2 band

is there a huge different from the Ken smith and Spector vs steinberger ?

does it operate at 18V? To use with Emg j?
 
#387
Good evening @PeaveyPlayer!

I know there is a difference in how the circuits are tuned, but I've not played through them or profiled the EQ response yet. The LHZ (preamp that I manufacture) is based on a pre-Kramer Spector Haz Labs preamp and works at both 9volts and 18volts.

At a high level, these preamps appear to have a common core design so I assume they run at 9volts or 18volts as well. Once I get the comparison completed, I'll share the results here.
 
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#389
I just finished soldering couple of HAZ clones. I’m going to use one with EMG35P and 35TW. Spector scematic has blend and 500k master volume in front of HAZ. What difference does it make if I use EMG supplied two volumes in front of HAZ? Two 25k volumes does not have the same total resistance as 25k blend and 500k master volume. What difference does that make? There is different impedance going in the HAZ right? Or is there?
 
#390
MPU said:
I just finished soldering couple of HAZ clones. I’m going to use one with EMG35P and 35TW. Spector scematic has blend and 500k master volume in front of HAZ. What difference does it make if I use EMG supplied two volumes in front of HAZ? Two 25k volumes does not have the same total resistance as 25k blend and 500k master volume. What difference does that make? There is different impedance going in the HAZ right? Or is there?
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It doesn't make any difference! The LHZ is a component-level clone of a pre-Kramer HAZ, and it doesn't care what the pots are in front of it. The pots are important to match the pickups, so generally 25k for actives and 250k or 500k for passives. As far as the circuit is concerned, there's no difference as the input cap is isolating the pots from the opamp.
 
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#391
That’s great. Then it’s just two volumes and HAZ clone as tone control. They are going into a Spector clone I’m building. Three piece maple neck with rosewood fretboard, walnut wings with crotch walnut top, Badass 1 bridge and lightweight Gotoh tuners.
 
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#392
AgingEngineer said:
As far as the circuit is concerned, there's no difference as the input cap is isolating the pots from the opamp.
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That's true for DC yet its a bit more complex for AC.
In first instance there is 1 Meg Ohm resistor active in regards of AC input impedance behind the DC blocking input cap. At the other hand side there is two 500k resistors in serial mode to provide virtual ground for the opamp. In total the input impedance at the opamp input equals about ~350k rather than 1 Meg which in consequence means a total AC input impedance actually more at lowish side of input impedance for any passive pickup.

edit:
lots of 9V battery powered stomp boxes that shall provide HiZ do frequently suck on just the same reduced input impedance issue as well as it is true for the HAZ schematic.
This reduced HiZ impedance issue is very often true to many 9V battery powered schematic designs that where made in the 70's and 80's and 90's of the last century.
 
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#393
MPU said:
That’s great. Then it’s just two volumes and HAZ clone as tone control. They are going into a Spector clone I’m building. Three piece maple neck with rosewood fretboard, walnut wings with crotch walnut top, Badass 1 bridge and lightweight Gotoh tuners.
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Very cool! Have you posted pictures of the build anywhere? I think I first found the TB site stumbling on a link of someone building a Spector clone and they'd posted some of the engineering drawing for the body curves... Always wanted to build my own, but I'm terrible with woodwork.
 
#397
fibz said:
It would be certainly interesting how this thing works/is designed.
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Korg is definitely trying to keep it in the family between Aguilar and Darkglass for the majority of their preamps now. I've heard the samples and it is definitely not as bright as we're used to. It doesn't quite nail the Haz, but I think that's by design so the Haz remains exclusive to the USA's.
 
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#398
I’ve had my Spector NS Pulse II for about a week. I love this bass. I’m not much fir basses with preamps and I was somewhat unimpressed with the TonePump Jr.
much to hit and aggressive for my taste.
When I texted Lonnie about his LHZ preamp, and read some of the reviews, I was somewhat skeptical about it. I had never played or heard an older Spector so I didn’t know what to expect.
Well I ordered one and installed it today. The difference is unbelievable. It’s no where as aggressive as the TonePump Jr. It’s a bit smoother, and the bass and treble adjustments are much more linear. I love the center-detent on those controls.
If I play it normally it’s smooth and clear, but when I dig in there’s just enough breakup in the notes to remind me of the 70s & 80s and how a lot of basses sounded back then
My other basses are going to have a very difficult time working their way back on-stage.

Thanks so much, Lonnie. You hit a HomeRun with this!
 
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#399
Pep said:
My other basses are going to have a very difficult time working their way back on-stage.

Thanks so much, Lonnie. You hit a HomeRun with this!
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Man.... This just made my night! The LHZ started as a personal project right here in this thread on TB, and I am still as excited today as I was on day 1 whenever I connect with someone on their tone journey. I still don't advertise (would rather spend time building and talking with clients than doing SEO and keyword juggling) so word-of-mouth means everything.

Thank you!
 
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#400
AgingEngineer said:
Man.... This just made my night! The LHZ started as a personal project right here in this thread on TB, and I am still as excited today as I was on day 1 whenever I connect with someone on their tone journey. I still don't advertise (would rather spend time building and talking with clients than doing SEO and keyword juggling) so word-of-mouth means everything.

Thank you!
Click to expand...
Thank you for sharing your quest and for allow me, and others, to enjoy the fruits of your journey!
 

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