Project files: Little helpers – Alps PCBs III

What is it?
These are “little helper” boards for the Alps RK168xx series of motorised potentiometers. These pots are not quite as good quality as the standard Alps “Blue Velvet” RK27-series, but they are cheaper and smaller. They are also used in many commercial products, so they should work fine for many diy projects. The motor also means that the pots have a nice mechanical feel to them šŸ™‚
There are two board versions, a 2-channel (for stereo with the RK16812) and a 4-channel (for balanced amps with the RK16814). Alps also makes a six-channel version of the pot and adjusting the footprint to fit these should be relatively easy, but I have no need for these now so I couldn’t be bothered šŸ™‚

How big are the boards?
Both boards measure 1.85″ x 2.0″ (app. 47Ā x 51 mm) and theĀ rear mounting holes are in the same place on both boards.

What is the status of the boards?
BothĀ are version 1.0 since they are exactly as my prototypes.

Does it use any special/expensive/hard-to-find parts?
Mostly there’s only one real part on the board and that is the pot itself, so not really šŸ˜€

Anything else I need to know?

  • These are “preamp” style boards have a ground plane and a ground pad that can be used if you grounding scheme requires the shaft of the pot to be grounded. Use a piece of wire connected from the ground pad to either one of the screws on the back of the pot or soldered to a ring terminal wedged between the pot and the chassis. You can also use the grounding pad on the bottom instead.
  • The boards can also be used to make separate, passive preamps. In this case, a 10k potentiometer should be used.
  • The screw clamps are standard 5mm pin spacing types, but of course it is possible to solder bare wires to the boards as well.
  • The basic Eagle footprint for the RK168 was one I found in a diyaudio-thread, so I can’t take credit for that. All I have done is modify it to match the Quad-version as well.

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

As usual,Ā please remember to consult the manufacturer’s datasheet as well.

Project files: Little helpers – Ground Loop Breaker

One more little helper for you guys šŸ™‚ Once again, not exactly a major effort with this one, but I hope it is still useful.

What is it?
Itā€™s a Ground Loop Breaker as described in this article by Rod Elliot on grounding/earthing of audio equipment.

How big isĀ the board?
The boardĀ measures 2.0″ x 2.0″ (app. 51 x 51Ā mm.)Ā This is my new semi-official standard for modular circuits like this and will allow stacking of boards šŸ™‚

What is the status of the boards?
The board is version 1.1 as I had to replace the original bridge rectifier with a different footprint.

Does it use any special/expensive/hard-to-find parts?
No.

Anything else I need to know?

  • Read the articleĀ and follow the recommendations on connections.
  • The rectifier bridge should be in a so-called GBPC-W package with wire leads. The rating should be 25A or higher and both the bridge and the capacitor should be rated for at least the mains voltage where you live (so 250VAC/400VDC in 230V countries)
  • The connections on the ā€œgroundā€ side (input) are either via the screw clamp or a couple of FAST-ON tabs. Connections on the ā€œearthā€ (output) side are either via FAST-ON tabs to a dedicated ground screw or a plated-through hole that can be used to make the chassis connection. The board mounting holes are isolated. UseĀ cables that are as short and thick as possible for all connections.

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

Be careful with working with any mains wiring and be sure to ask questions if you are not sure about anything, either in an online forum or to a local electrician (preferred).

Project files: Little helpers – Capacitor boards

Another post inĀ my ā€œlittle helpersā€ project series consists of a couple of capacitor boards for mounting input/output capacitors that will not otherwise fit on an amplifier board.

What is it?
Universal boards for (input) capacitor mouting, either for testing purposes or for designs where there is no space to mount a decent-sized capacitor on the main PCB. I made the small board to supplement my P3A clone where adding a large input capacitor would have increased the overall board size quite a bit, so using an off board input cap gives more flexibility. The background for theĀ ridiculously large ā€œMegaMKPā€-version you can read in my previous post.

How big are the boards?
This big šŸ™‚

  • The “normal”Ā boardĀ measures 2.0″ x 2.0″ (app. 51 x 51Ā mm.)
  • The “MegaMKP” boardĀ measures 3.95″ x 0.625″ (app. 100Ā x 16Ā mm.)

What is the status of the boards?
BothĀ boards are in v1.0, meaning they have been tested and are working.

Does it use any special/expensive/hard-to-find parts?
Well, thereā€™s really nothing on these boards except the capacitors šŸ˜€

Anything else I need to know?

  • The small board has capacitor mounting for small caps on the top and for larger caps. Max dimensions are approximately:
    • Bottom side mounting: 25 x 38mm axial capacitor (with holes for 33mm long caps as well).
    • Top side mounting: 27mm lead spacing x 15mm thick box cap or app. 20 x 28 mm. axial capacitor.
  • If using the bottom side mounting points, either mount the board upside down on standoffs or don’t use the footprint for the terminal block but solder wires to the board instead.
  • The large board has holes for a various combinations of 2/3/4 large caps. There are screw holes that can be used to mount the boards to the chassis via standoffs so you can use caps as big as you like.

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

Project files: Little helpers – Alps PCBs II

What is it?
Not exactly the most complex designs ever made šŸ˜‰ A couple of PCBs for mounting Alps (or pin-compatible) potentiometers. Unlike the previous boards these ones have screw clamps for input and output, making them better suited to testing useĀ and peopleĀ with fat fingers (like yours truly) šŸ˜€Ā There are two versions, a 2-channel (for stereo) and a 4-channel (for balanced) amps.

How big are the boards?
The SE board measures 1.15″ x 1.975″ (app. 29 x 50 mm) and the balanced board measures 1.975″ x 1.975″ (app. 50 x 50 mm.)

What is the status of the boards?
I’ve called these version 1.5 since they are based on the previous boards of the same type, just modified with screw clamps for the input/output connections.

Does it use any special/expensive/hard-to-find parts?
Mostly there’s only one real part on the board and that is the pot itself which can be a bit expensive, so yes, I guess so šŸ˜€

Anything else I need to know?

  • These are “preamp” style boards have a ground plane and a ground pad that can be used if you grounding scheme requires the shaft of the pot to be grounded. Use a piece of wire connected from the ground pad to either one of the screws on the back of the pot or soldered to a ring terminal wedged between the pot and the chassis.
  • The stereo board has a four-hole footprint to fit various pots that use that configuration, but the last set of pads isn’t connected to anything so will not work directly with a loudness tap.
  • The boards can also be used to make separate, passive preamps. In this case, a 10k potentiometer should be used.
  • The screw clamps are standard 5mm pin spacing types, but of course it is possible to solder bare wires to the boards as well.

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

As usual,Ā please remember to consult the manufacturer’s datasheet as well if you use a different pot than the recommended type.

Project files: Little helpers – Powerhelpers

What is it?
A few auxiliary boards to match theĀ mainscontrollerĀ boards or for use one their own.Ā More specifically, there are a couple of relay boards for use with the relay-less version of the Mainscontroller. The large relay board is intended for a “T90”-type relay which is typically rated 20/30A. The smaller board is using a Omron G5LE relay which is rated 6/10A.

There is also a simple softstart-board that can be used when powering transformers over app. 250-300VA. This is based on a very old (and frequently copied) circuit from Elektor that seems to work well, at least for medium-sized PSUs.

How big are the boards?
The Softstart board and the large relay board are both 2″ x 2″ (app. 51×51 mm.). The smaller relay board measures 1.5″ x 2″ (app. 38 x 51 mm.) As the pictures show, mounting holes and connectors line up so the boards can be stacked and cables routed neatly between them.

What is the status of the boards?
The softstart board is now in v1.5 as it is an improved version of one I did earlier. The large relay board is v1.1 as I have prototyped it and corrected the relay footprint which wasn’t perfect (my own design, obviously…). The small relay PCB is in v1.0. I haven’t actually received and tested the prototype boards yet, but as it is the exact same circuit as the large board and the footprint for the relay is an eagle standard one I am OK with releasing this design as well.

Does it use any special/expensive/hard-to-find parts?
Not really, but:

  • The T90 relays can commonly be found on ebay. There are name-brand equivalents as well from Omron, Finder and other manufacturers of relays.
  • The Omron G5LE can be puchased cheaply from Mouser or Reichelt. Alternatively there are equivalents available on ebay, usually marked with SRD-xxx designations.
  • The relay on the softstart is an Omron G2R-24V type which is also available from Mouser or Reichelt.
  • Note that the large 330nF capacitor on the soft start board must be an X2-rated type.

Anything else I need to know?

  • When in use, these boards mayĀ feature exposed mains parts (the softstart certainly will). One especially “problematic” thing is that the legs of the axial resistors are partly exposed so make sure that the board is protected from accidental touches. If you are stacking boards, I suggest putting the relay PCB on top as it has fewer exposed parts, but even so a cover** of some sort could be a good idea.
  • Whether used with the Mainscontroller board or on it’s own, be sure that you are aware of the current consumption of the mechanical relays. The T90 relay typically consumes app. 1W (1200 mW worst case) and the G5LE relay consumes app. 400mW, which for instance means they cannot be controlled directly by a micro controller.
  • I have never tested the softstart board on transformers larger than 500VA. I imagine it should be good up to around 800-1000VA, but anything more and I would be cautious and probably look for something with bigger relays and resistors. The same applies if you are using exceptionally large capacitor banks.
  • **The cover is based on an idea I had a while ago but didnā€™t test until now: I wanted to have an easy way to make covers to shield sensitive and hot/live parts from touches. I could use Front panel express to have 2mm acrylic sheets made but that is comparatively expensive, so I came up with another way: The Gerber files give me the board outline for each design and so by rendering the Gerbers e.g. with Circuitpeople I can get a true-size outline. Once that is scaled I can then import into a graphics program to add warning symbols, text or anything else. To get the cover I simply laminate the printout using a home laminating machine with the thickets foil type and then use a hole punch to cut out the mounting holes which are clearly marked. It’s obviously not a safety-approved material in any way, but it fits perfectly and it will protect against accidental touches which is bound to be better than nothing.

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

Project files: Little helpers – Fuseboards

The thirdĀ part of my ā€œlittle helpersā€ project series consists of a few connector/fuse boards for power supplies or for testing/lab use.Ā Not exactly the world’s most interesting PCBs, but stillĀ  – they can be quite useful so I decided to publish them anyway šŸ™‚

What is it?
These are simple fuse-boards with LEDs to be used on the secondary side of a transformer or DC PSUs (such as switchers). There are two versions:

One version can be used to combine two AC or DC voltages to provide a center-tapped voltage. The circuit works on both AC and DC so can be used for example for wiring up two secondary windings on a transformer to provide a +/- voltage or for combining two DC power supplies to do the same.

The second type of board is more or less identical, except that the ground plane is split so they are “passthrough” for the input voltages. This is useful for instance if you want to put fuses between the transformer secondary and a PSU board that already has an onboard rectifier and does not need (or want) a center-tapped voltage.

The boards also include fuses for both rails as well as LEDs to indicate that power is applied. If connected in the ā€œstandardā€ way then the LEDs are connected to the input through the fuse, so if the fuse breaks the corresponding LED will turn off.

How big are the boards?
There are two sizes of both designs:

  • The “small” one measures 2.0″x1.95″ (app. 51x50mm)
  • The “normal” one measures 2.5″x1.95″ (app. 64x50mm)

The two versions are compatible, meaning the board size and hole spacing are the same for the two versions.

What is the status of the boards?
All boards are in v1.0, meaning they have been tested and are working. (Well, to be honest I haven’t received the prototype versions of the “passthrough” boards yet, but as they are made from the schematics to the other ones I expect no issues) šŸ™‚

Does it use any special/expensive/hard-to-find parts?
Not really. The fuses are standard 5x20mm types with holders (22.5mm lead spacing). The LEDs, resistors and diodes are all “standard” types and the terminal blocks are 5.0/5.08mm types.

Anything else I need to know?

  • On the large boards it should be possible to use PCB-mounted FAST-ON tabs instead of the terminal blocks (not tested though).
  • Note: These boards are not intended for mains voltage use!

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

Project files: Little helpers – Connectors

The second part of my ā€œlittle helpersā€ project series consists of a few connector boards amplifiers or for testing/lab use.

What is it?
Three boards for various connectors and purposes:

  • AnĀ XLR/TRS-board which is a small breakout-board for a Neutrik NC6FI-H XLR/TRS combo connector that means you can then use bare wires or a three-pin connector to wire up the socket.
  • AnĀ XLR I/O board which is intended for XLR in and loop out with “standard” PCB-mounted Neutrik D-series XLR connectors.
  • AnĀ RCA I/O board which is designed for some board mounted RCA connectors. I don’t actually know who makes these but they are pretty much the only decent-quality style PCB mounted RCAs that I know of. There are a couple of of internet sources for them (ebay, audiophonics, Rapid electronics, ) and I think they are identical (if nothing else then in size/dimensions) to the ones sold by Vampire at a more “audiophile” price šŸ˜‰ If anyone knows the “true” source of these then I’d like to know?

How big are the boards?
Smallā€¦ I don’t want to list them all here šŸ™‚

What is the status of the boards?
The boards are in v1.0 which means they have been tested and are working.

Does it use any special/expensive/hard-to-find parts?
Mostly there’s only one real part on the board and that is the connector itself which can be a bit expensive, so yes, I guess so šŸ˜€

Anything else I need to know?

  • Note that although the XLR/TRS sockets do fit into a standard Neutrik D-series hole, for reasons I don’t quite understand the board will not sit completely straight if mounted that way. For most uses that will not be a problem, but if you want to use these in a 1U enclosure you need to be a bit careful or mount the board upside down. To avoid this, make your panel holes exactly as it is shown on the drawing.
  • On the XLR-boards there is an onboard jumper to connect pin 1 to ground, so depending on usage (SE or BAL) and grounding scheme of your build, this is an easy way to manage ground loops. There is also a jumper to connect the chassis to ground which should not ever be necessary if everything you connect is made properly. If it isn’t, then that jumper is here to save the day šŸ˜€
  • The “XLR loop” boards are included in a “right” and a “left” version which are mirrored. If you only need one version and don’t really care which one, I’d recommend the one marked “left” as it has the nicest routing (unbroken ground plane).

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

As usual,Ā please remember to consult the manufacturer’s datasheets as well and ensure that you verify the connector part numbers before hitting the “buy” button on anything :).

Project files: Little helpers – Alps PCBs

These “little helpers” are small supporting boards I have developed for my various audio projects. I have a few different ones and I don’t think they are really “big” and sophisticated enough to warrant a post for each one so I’ve decided to lump them together in a few groups instead.

What is it?
The first collection is PCBs for mounting Alps (and a few other types, including the Noble I have used in some of the pictures šŸ™‚ ). Included are boards for different types of potentiometers namely stereo without motor and quad with and without motor (i.e. Alps types RK27112 and RK27114/RK27114MC).

For the unmotorised version there are two variants: ā€œPreampā€ groups input and output terminals together and ā€œBreakoutā€ groups the individual decks of the pot together. The ā€œpreampā€ version is used when you want the signal to flow through the pot (such as in a pre-amp), whereas the ā€œbreakoutā€ version is used when you want to insert the pot into an existing circuit, i.e. for wiring an off board pot to an amplifier PCB that has onboard space for it. This distinction is mainly to help simplify wiring ā€“ unless the circuit has a really strange design with respect to grounding, you can of course use the boards interchangeably.

How big are the boards?
Smallā€¦ I don’t want to list them all here. The biggest board is the quad motorised which measures 3.5″ x 1.75″ (app. 89 x 45 mm).

What is the status of the boards?
The boards have been tested in v1.0 and for a couple I made some cosmetic changes, including changes to the footprint of the motorised quad pot, to upgrade them to v1.1.

Does it use any special/expensive/hard-to-find parts?
Mostly there’s only one real part on the board and that is the pot itself which can be a bit expensive, so yes, I guess so šŸ˜€

Anything else I need to know?

  • The stereo boards have a four-hole footprint to fit various pots that use that configuration, but the last set of pads isn’t connected to anything so will not work directly with a loudness tap.
  • The various quad boards have all holes in the same places so the motorised and unmotoriseed boards can use the same chassis footprint (even if of course the unmotorised board is smaller)
  • The “preamp” style boards have a ground plane and a ground pad that can be used if you grounding scheme requires the shaft of the pot to be grounded. Use a piece of wire connected from the ground pad to either one of the screws on the back of the pot or soldered to a ring terminal wedged between the pot and the chassis.
  • On the motorised quad pot the shaft is connected electrically to the solder pins for the motor housing, so if you want to ground one of these you only need to connect a small jumper on the underside of the board from one of the housing pins to the ground pad – no messy wiring needed.
  • The eagle footprints for the quad pots are not “official” but ones I made myself by chopping up the stereo footprint. They work fine, but they probably aren’t the last word in accuracy and the holes for the housing pins could have been done more elegantlyā€¦

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

As usual,Ā please remember to consult the manufacturer’s datasheet as well.

 

EDIT July 28th 2014: Added pictures (which I stupidly forgot when I posted this…)