+/-6V power - check my circuit!

P

phi1

Well-known member
I’m planning to mod a rockman bass headphone amp to accept typical 9v power (the guy lost the original special +/-6V power adapter, and he lost the battery cover so batteries aren’t an easy solution).

I drew up a circuit for converting the 9VDC to +6V/0V/-6V DC for the rockman. Anyone see any issues with this?

The L7806 I got from Tayda is a big one (up to 1.5A).

Edit::: don’t use this first drawn circuit, follow the thread for a working circuit.
 

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A friend and I have been building true Rockman X100 clones that will run off a standard negative center 9V @ 500mA wall-wart. We learned very fast that standard chargepumps cannot supply enough current.

What we did find was a nifty little buck converter module on LINK: eBay and LINK: Amazon. We bought from both sources and they are reliable.
The MP1584EN in these modules is unique in that two of them can be fed the same 9V DC supply, and tho wired together (to get the ±6v dual rail supply with enough current on both sides) unconventionally, the diagram below shows how to with the BC modules to gather to set a solid, quiet, lo-ripple ±6V dual-rail DC supply pair at over 500mA each. Once they are wired together, connect a 9V battery at eh + In and the ground inputs. Then put a DC voltage meter on the output of each one, one at a time and tweak the tiny trimpot to set the output for +6V and -6V respectively. Use a tiny plastic tipped flat-head screw driver - those trimmers are all metal and quite small. It may take a few tries to nail ±6.00 when adjusting the trimmers. It's OK if they are within 0.05V of the ±6.00V

These BC modules are quite versatile in that they will provide the same voltage whether loaded or not. The current available varies on the input supply and output yield as set by the trimmers. At +9V DC in and ±6V DC out (+6V on one module & -6V on the other), the available current exceeds 1A. More than enough to drive a Rockman.

I often use this to modify Rockman HP gear.

BuckConverters_Dual-Rail-Wiring_MP1584_Notes.jpg

We went so far as to have some mounting daughterboard PCBs fabricated to accommodate the two BC modules for our Rockman X100 builds for quicker assembly.

BC_Module_PCB.png

And just for the heck of it, some shots of our RMS X100 builds . . .
(In the the 3rd shot, you can see the mounted BC module PCB.)

X100_V2_AN-07P_Done_Powered.jpg V2_Gutshot_Done_01.jpg Enclosure_Final Prep.jpg
 
Cybercow said:
A friend and I have been building true Rockman X100 clones that will run off a standard negative center 9V @ 500mA wall-wart. We learned very fast that standard chargepumps cannot supply enough current.

What we did find was a nifty little buck converter module on LINK: eBay and LINK: Amazon. We bought from both sources and they are reliable.
The MP1584EN in these modules is unique in that two of them can be fed the same 9V DC supply, and tho wired together (to get the ±6v dual rail supply with enough current on both sides) unconventionally, the diagram below shows how to with the BC modules to gather to set a solid, quiet, lo-ripple ±6V dual-rail DC supply pair at over 500mA each. Once they are wired together, connect a 9V battery at eh + In and the ground inputs. Then put a DC voltage meter on the output of each one, one at a time and tweak the tiny trimpot to set the output for +6V and -6V respectively. Use a tiny plastic tipped flat-head screw driver - those trimmers are all metal and quite small. It may take a few tries to nail ±6.00 when adjusting the trimmers. It's OK if they are within 0.05V of the ±6.00V

These BC modules are quite versatile in that they will provide the same voltage whether loaded or not. The current available varies on the input supply and output yield as set by the trimmers. At +9V DC in and ±6V DC out (+6V on one module & -6V on the other), the available current exceeds 1A. More than enough to drive a Rockman.

I often use this to modify Rockman HP gear.

View attachment 44857

We went so far as to have some mounting daughterboard PCBs fabricated to accommodate the two BC modules for our Rockman X100 builds for quicker assembly.

View attachment 44860

And just for the heck of it, some shots of our RMS X100 builds . . .
(In the the 3rd shot, you can see the mounted BC module PCB.)

View attachment 44861 View attachment 44862 View attachment 44863
Click to expand...
Lovely clean design for the enclosure and build.
 
As an additional note on those BC modules, they do NOT need filter caps at the output. We found that adding any caps larger than about 10µF on the output can prevent the BC modules from booting. The internal protection on those BC modules sees a larger value electrolytic cap as a voltage well too deep to fill in the BC module boot time and the short circuit protection kicks in and shuts the BC modules down. The high frequency of operation and low ripple output are sufficient without added filter caps on the output.
 
Just got a couple of those modules to try! I've been looking for a good solution to give me ±15V for a while
 
Got the boards from Amazon, and it worked perfectly according to the diagram @Cybercow shared (thanks!). I used a little jb weld to fix the boards in the housing and tied the wires into the connections in the battery spring board.

I also sprayed a little contact cleaner in the switches, which seems to help them behave more reliably before shipping back to its owner.
 

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phi1 said:
Got the boards from Amazon, and it worked perfectly according to the diagram @Cybercow shared (thanks!). I used a little jb weld to fix the boards in the housing and tied the wires into the connections in the battery spring board.

I also sprayed a little contact cleaner in the switches, which seems to help them behave more reliably before shipping back to its owner.
Click to expand...
Glad you got it running.

Does it run with the two 220µF caps still in place near the wire ribbon strip? I had to take mine out. When those BC modules see a large capacitance well at boot-up they go into reset/protection mode.
 
I didn’t remove anything from the rockman boards, I fired it up a few times with a simple one-spot wall watt without issue, and now it’s in the mail… so I hope it continues to work, but thanks for the heads up, I’ll let them know to reach out to me if they have any issues.
 
Good to know you've no issues with the caps. In our testing and trials, we found that anything over ~ 47µF immediately after the BC Modules would trigger the self-protection mode. But, inconsistently, they would fire up even with the 220µF caps in place. We chose to remove them for consistency's sake. Those BC modules deliver a rather clean supply on their own and don't need them.
 
I just ordered (and received) my modules -- holy cow are they ever small - like the size of a Chiclet.
Here's a question - what kind of wire are you using to make these connections? I've never worked with such small pieces before. Anything I need to know materials wise or technique wise? All I can say is that I'm glad they came in a 6 pack!

I replaced the caps and (IIRC) a bad amp chip on my x100 years ago - but this is the first time I've worked on something this small since.
 
phi1 said:
Do they look similar to my pictures? I just used 22awg solid, same as I use for everything.
Click to expand...
Exact same - I bought them from the Amazon link in the video that was made (yours?).

Here’s a photo of the board (just showing one) with some 22awg plusivo wires cut to size…


1736963137772.jpeg

I was just practicing cutting wire here as a rough-in exercise.

Can I also ask how you secured it in the Rockman? The same glue used to glue the boards together?

Many thanks
 
That wire working with these boards looks fine to me!! I don’t remember the details super well. I read through my post and I said I used JB weld to stick them both in one of the Housing halves. Sounds familiar, I’m sure other glues would work too
 
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