Enjoy the benefits of a premium membership!
Upgrade Account
-
TalkBass has been independent since 1998. Add your voice.
Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
Join free Log in
Want zero display ads or expanded classifieds tools? Compare plans.
Just saw a USA Haz go on sale for$450 in a Spector group on Facebook and it sold within 40 minutes. Makes me so happy to have options like the LHZ available that really don't give anything up in terms of tone. Thank you @AgingEngineer for bringing this to market!
This is great!
I’m building a Spector inspired bass and this would be right up my alley.
Are these the same preamps listed on eBay?
I’m building a Spector inspired bass and this would be right up my alley.
Are these the same preamps listed on eBay?
As an eBay Associate, TalkBass may earn a commission from qualifying purchases.
awesome. That’s what I saw the other day. I like that I’m not held to the standard Spector control layout like on the Haz and most SNC.
looks great and the sound clips are on point!
As an eBay Associate, TalkBass may earn a commission from qualifying purchases.
- Apr 14, 2022
- 371
- 2,082
- Disclosures
- Owner of LRWMedia, manufacturer of LHZ vintage bass preamps.
Thank you @VeryTallBassist
When I started this adventure, it was just to build a Haz for myself as it was impossible to get a new Haz for a Spector ReBop/Euro. I didn't know much about the Haz back then, except that I loved the sound. Since then I'd talked to a lot of players and learned more about other models that originally shipped with a Haz that I was not aware of.
For instance, this week I'd gotten a message from the owner of an old Ken Smith BT3 asking if the LHZ is the same as the old 2-band Haz that was used in some BT3's. He sent me a couple photos. I could see the component count was the exactly the same, the op-amp was the same, and the PCB connections (that I could see from the limited photos) were the same. Most of the components had the same values, so I am confident that the Ken Smith Haz is the same circuit, albeit with minor differences to the EQ curve to optimize it for that bass.
It makes me wonder if it's worth trying to get a catalog of images of some of those other Haz preamps to reverse engineer? Use the same PCB, but populate it with components that were used in the BT3, and it would be functionally the same.
@thisSNsucks: Yes, this is the same one! It's also on Reverb as well. The LHZ started here in this forum and got off the group with all the excellent information, insight, and feedback from folks here.
Looks like HAZ also made pre amps for Fodera, Smith, and Steinberger.
Here is a brief bit of info with Steinberger:
HAZ Labs
Here is a brief bit of info with Steinberger:
HAZ Labs
- Apr 14, 2022
- 371
- 2,082
- Disclosures
- Owner of LRWMedia, manufacturer of LHZ vintage bass preamps.
I've had bunch of folks reach out asking if I am doing clones for Steinberger, Ken Smith, and Fodera basses. I've only found a couple pictures, not enough to do a full trace on, but it seems like they are following the same general circuit but are tuned slightly differently.
If someone can provide a full set of high resolution photos (both front and back, with multiple shots from different angles) I can reverse engineer those like I did with the Spector Haz.
- Apr 14, 2022
- 371
- 2,082
- Disclosures
- Owner of LRWMedia, manufacturer of LHZ vintage bass preamps.
It had been a while since I'd posted, but finally had time to put together a video doing a schematic comparison between the LHZ and an original Haz and a KHaz. Multiple thanks to @Jim C for loaning me his Haz and KHaz for analysis!
I think you're onto something with the KHaz having a mislabeled capacitor somewhere. Granted, my sample size is only 2 so I should also be careful in saying your experience carries over to all KHaz boards, but the two I have owned had a different treble response. I never did actual testing like you, but to my ear they were not breaking up the same way on the high end. One of them got sold, the other one I kept and refurbished with the correct resistors, pots, and capacitors and it sounds identical to the Haz, the Czech Haz, and the LHZ.
One thing that was a little strange - on the Czech board, the volume pots that were installed when I got it were 500k. As a result, they were more of an on/off switch than a volume control. I replaced them with 25k pots and it's back to normal. But since this is the only one of these boards I have ever seen, I'm not sure if it came that way from the factory or not. They look identical in construction to the 100k pots for tone controls, but they're clearly not the right value for active EMGs. My suspicion is a previous owner may have made some changes long ago but found the same manufacturer for the volume pots as came stock. It also had EMG 3 pin solderless pickup wires soldered directly onto the board. I don't think EMG had yet stopped making hardwired pickups in 1996, but I may be wrong.
- Apr 14, 2022
- 371
- 2,082
- Disclosures
- Owner of LRWMedia, manufacturer of LHZ vintage bass preamps.
I forgot to mention it in the video, but the KHaz I was testing also used a different op-amp. It has the 072D where the Haz and LHZ use the 442CN op-amp, so the op-amp response when pushed results in different artifacts.
I was measuring resistance values in the circuit. Aside from the anomalous 6.8k marked as 100k and different voltage divider values, all the other resistors matched. I cannot test cap values on the board as connections in the circuit will result in incorrect or invalid readings, so all I had to go on were the values marked.
Given that the circuit itself was a match, I have to assume one or more caps were either mislabeled or had failed to give the different EQ response. Even the low end response was different.
I agree: this is definitely not intended to be a judgement on all KHaz preamps! I know a lot of folks are using them and love them, but this particular unit had some issues. I am confident that if the caps were replaced with correct specs and the op-amp swapped out for a 442Cn, this would provide the same response as a Haz.
I was measuring resistance values in the circuit. Aside from the anomalous 6.8k marked as 100k and different voltage divider values, all the other resistors matched. I cannot test cap values on the board as connections in the circuit will result in incorrect or invalid readings, so all I had to go on were the values marked.
Given that the circuit itself was a match, I have to assume one or more caps were either mislabeled or had failed to give the different EQ response. Even the low end response was different.
I agree: this is definitely not intended to be a judgement on all KHaz preamps! I know a lot of folks are using them and love them, but this particular unit had some issues. I am confident that if the caps were replaced with correct specs and the op-amp swapped out for a 442Cn, this would provide the same response as a Haz.
That's absolutely right. I forgot to mention I swapped out the op amp to an LF442 when I rebuilt mine.
Well, thanks @AgingEngineer for that wonderful music featured in your vid above. That’ll stuck in my head 
Seriously, very interesting to watch. in an older post over at the Spector Owners forum, Sheldon also mentioned some technical details (https://www.talkbass.com/threads/spector®-owners-club.1066466/page-3959#post-24563864 depending on the browser you may have to scroll down)
@VeryTallBassist : had to do the same, changing the volume pots from 500k to 25k to make it work with active EMGs otherwise it would just work like an on/off switch. But I had other Spector buddies who changed their pickups (all KHAZ) no swap of volume necessary.
Seriously, very interesting to watch. in an older post over at the Spector Owners forum, Sheldon also mentioned some technical details (https://www.talkbass.com/threads/spector®-owners-club.1066466/page-3959#post-24563864 depending on the browser you may have to scroll down)
@VeryTallBassist : had to do the same, changing the volume pots from 500k to 25k to make it work with active EMGs otherwise it would just work like an on/off switch. But I had other Spector buddies who changed their pickups (all KHAZ) no swap of volume necessary.
Just pulled the trigger on my second LHZ preamp. I absolutely LOVE the one in my Rebop 5. This is going into an NS5CR I just got.
@AgingEngineer - here's a question for you. My Rebop seems to be draining batteries quickly and at random. It has the LHZ02. I'll be playing it one night and it's fine, I go to play the next day and it's completely dead. I already changed the output jack. Any ideas where I may be causing a short along the route the ring from the input jack would take to the negative? Or is there anything I should look for on the board?
@AgingEngineer - here's a question for you. My Rebop seems to be draining batteries quickly and at random. It has the LHZ02. I'll be playing it one night and it's fine, I go to play the next day and it's completely dead. I already changed the output jack. Any ideas where I may be causing a short along the route the ring from the input jack would take to the negative? Or is there anything I should look for on the board?
Are any part of the wires that are bare and/or solder tags on the pots touching each other ? I've noticed some very quick battery drain recently and on inspection I suspect this is what might been happening. I'm tightening up the pots again in a slightly different direction.
- Apr 14, 2022
- 371
- 2,082
- Disclosures
- Owner of LRWMedia, manufacturer of LHZ vintage bass preamps.
I just saw that order this morning as I am getting my coffee and starting the day. Thank you, it will be shipping out tomorrow morning!
Actually, I do have a suggestion regarding the power drain. There have been 3 folks to date that have reported a similar situation, and the common denominator is that the ground switch via the output jack is bypassed by being shunted by the control cavity shield. Basically, the battery ground is being picked up by a grounded pot and completing the circuit, so the pickups are always under power regardless of the jack being plugged in.
The resolution is to swap the RING and SLEEVE wires on the output jack.
The earlier version of the installation manual had the battery negative going to the SLEEVE, with switched power coming back to the preamp via the RING. This meant the control cavity was always connected to battery ground. By reversing the connections, the cavity is only connected to battery ground when the jack is plugged on.
The installation manual was updated to clarify the output jack wiring, and has been updated on the website.
