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Luxman DML-02

F

FrankyLttrs

Active Member
Thanks to member vinnysj, we have completed a PCB design for a replacement DML-01 using more modern components that should be available long enough to do a couple of runs. I ordered a test batch of boards and, while I am waiting, I turned my attention to designing a DML-02 PCB. The initial results are shown below. The 3D model shows too many pins. It is a 12 pin device where the pins are on 0.200 inch/2.54 mm centers so I used some 0.100 inch/2.54 mm headers for the visual design. I was able to get some dimensions for the length using some images of a replacement DML-02 and I took some measurements from an image to determine a width. It was really tight and my results didn't seem to match the images of the replacement DML. I don't have any DML-02 modules or equipment that uses them so I can't make a direct measurement. If someone has access to a DML-02 or a board that uses one, I would greatly appreciate a set of measurements. The most important measurement would be the pin-to-pin distance between the rows of pins, but any and all measurements would be appreciated. I've never done this before so I don't know if these things will work. I am going to test the DML-01 on my own equipment and I will be scouring the Internet for a dead piece of equipment that uses the DML-02 modules. If anyone has a lead on such a piece of equipment for a reasonable price, please let me know.
DML-02.jpg
dml2version2a.jpg
 
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Thanks for kicking off this project.
From online pictures, the replacement DML-02 uses standard header pins with only the odd pins installed. So, the distance between pins should be about 5.08mm. The width looks like 6 pins distance (152.24 = 2.54*6) similar to DML-01
Here is the iteration of DML-02 but using SMT components. Using FJV1845 for NPN and FJV992 for PNP. After much thinking, using through hole transistors like your design might be better since it does not require a special jig for transistor gain matching.

1699419795199.png
 
vinnysj said:
Thanks for kicking off this project.
From online pictures, the replacement DML-02 uses standard header pins with only the odd pins installed. So, the distance between pins should be about 5.08mm. The width looks like 6 pins distance (152.24 = 2.54*6) similar to DML-01
Here is the iteration of DML-02 but using SMT components. Using FJV1845 for NPN and FJV992 for PNP. After much thinking, using through hole transistors like your design might be better since it does not require a special jig for transistor gain matching.

View attachment 3030432
Click to expand...
Very clean. Are there dual packages with prematched transistors? Do they have to be that well matched?
 
vinnysj said:
Thanks for kicking off this project.
From online pictures, the replacement DML-02 uses standard header pins with only the odd pins installed. So, the distance between pins should be about 5.08mm. The width looks like 6 pins distance (152.24 = 2.54*6) similar to DML-01
Here is the iteration of DML-02 but using SMT components. Using FJV1845 for NPN and FJV992 for PNP. After much thinking, using through hole transistors like your design might be better since it does not require a special jig for transistor gain matching.
Click to expand...
I was hoping the width was wider, but that is what I got out of the image measurements as well. I have to believe that all the dimensions are some multiple of 0.100 inch so I'll go with a multiple of 6.
 
ivandezande said:
Very clean. Are there dual packages with prematched transistors? Do they have to be that well matched?
Click to expand...
The better the match, the better the noise and stability of the amplifier, but it isn't that critical for non-audiophiles. The dual packages are matched by default because the semiconducting elements would have been manufactured at the same moment under the same conditions using the same materials, which was the whole point of ICs, including dual packages, for differential amplifiers in the first place. You could go with non-dual packaged transistors and hand-match them, but I doubt you would get any closer than two semiconductors manufactured at the same moment.

I have a morbid fear of unobtanium, so that is why I am doing this, it's a coping mechanism.
 
If using non-dual packaged transistors and you need matched, it is recommended to source taped vs. bulk devices. The taped units were probably made much closer together than a couple transistors that happen to be next to each other in a bag.
 
FrankyLttrs said:
The better the match, the better the noise and stability of the amplifier, but it isn't that critical for non-audiophiles. The dual packages are matched by default because the semiconducting elements would have been manufactured at the same moment under the same conditions using the same materials, which was the whole point of ICs, including dual packages, for differential amplifiers in the first place. You could go with non-dual packaged transistors and hand-match them, but I doubt you would get any closer than two semiconductors manufactured at the same moment.

I have a morbid fear of unobtanium, so that is why I am doing this, it's a coping mechanism.
Click to expand...
For sure! I just really like SMD parts on new boards which I know isn't repairable technically, but is cleaner and can be assembled from factory.
Super glad you guys are doing this. Hope to see them on eBay soon.
 
Resized to the smaller footprint, had to switch over to SMD resistors (I didn't know what wattage would be OK so I just picked a size that fit) but stayed with the through-hole transistors. If I have to sort through a bunch of transistors, I would rather it be simple to do.
DML-02.jpg
 
Ok, one last iteration. Found some dual-packaged SMD BJTs (thank you markthefixer!) that should work and be matched as well as can be. I think the resistor values will have to be tweaked, I can't believe that changing every single transistor in the whole circuit will not incur a cost when it comes to the resistor values:
DML-02 SMD.jpg
As I have nothing to test it in, I am leaving this here and will focus on getting the DML-01 working. As I don't know if the circuit will work, I am loathe to release the Gerbers.
 
Which kind is on the bad channel? Would be pretty lucky for it to be a bad DML as the cause, considering your intentions. Would probably a good idea to recap it too, also check for Hitachi transistors with silver oxide on the legs, as these are known to go bad.
 
The C12 was produced right as Luxman was at its lowest and was sold to Alpine. Documentation from that era is difficult to find. The one schematic I have doesn’t include a diagram showing component placement, or even a right and left channel. I haven't looked at the silkscreening yet to determine what's what and I may have to trace the signal to determine which module it is.

The PO used Deoxit liberally to try and cure it. It has a 60 Hz hum on the right channel and the SNR is improved by flipping the muting switch so the PO Deoxited the heck out of that switch. It has been my experience when there is a hum on only one channel, there is a differential pair somewhere that is out.

It only has eight electrolytic capacitors so a recap will be easy.
 
FrankyLttrs said:
The C12 was produced right as Luxman was at its lowest and was sold to Alpine.
Click to expand...
This preamp was designed in Luxman's best early era, the time when their 50th Anniversary (1975) Series, the Tim de Paravicini designed M6000 power amp and the matching tuner T-110 and preamp C-1000 (don't know how much work Tim did on these) along with his tube MB3045 power amps. Additionally, their new top of the line gear the Laboratory Reference Series was starting to hit the shelves. The -12 series with the L-10 and L-11 were in their Laboratory Standard Series, their next best products and these came out about 1976. This is well before the Alpine acquisition in 1984. Maybe the proliferation of so much higher end gear caused problems but they seemed to sell a good bit of it. Worthy gear to restore. Be nice to have sources for these DML units.
 
My bad on the dates. I liked my delusion though, now I'm disappointed in Luxman because they had no excuse for the poor documentation.

I love my M-12s, they are the best sounding amps I have and their appearance is growing on me. If you are going black, might as well finish the job by being as austere as possible.
I'll be ordering boards and parts for an all SMD replacement for the DML-02. Hopefully that will ensure that these amps can be repaired far into the future.
 
FrankyLttrs said:
I'm disappointed in Luxman because they had no excuse for the poor documentation.
Click to expand...
I expect poor documentation with Luxman. I think they tried to make too much stuff over those years. With not enough technical writers they service info suffered and some of the descriptions in them are nothing more than a typewriter written page or two.

I'm using my M-12 on the DQ-10s with a powered sub and it seems to drive them just fine.
 
I just read up on the DQ-10 system, pretty cool analog tech! I love seeing what people did pre-digital. My job is all digital all the time and I love messing with analog stuff.

It's all about the bass isn't it? I'm not comfortable with powered subs. I am taking a different tack and will be trying biamping with a woofer amp and 2 way mid/tweeter amp arrangement. I have two working M-12s and a board from ESP to build an active crossover that will not introduce phase shift during the crossover processing. I have experience with building air suspension speakers and I want to build some speakers just for this purpose. Once I have the C-12 repaired so that I can use it as a preamp for the M-12s, I will start on the crossover and speakers.

My long term goal is to build a heterogenous biamping system with a dedicated woofer amp of around 100wpc so I can take any of my integrated amps, receivers, or power amp/pre amp combos to neighbor annoying sound levels. Can't wait to see my Harman Kardon 330A rock the house!
 
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