new idea (for me): dual first order building block PCB - diyAudio
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Old 16th February 2011, 01:20 AM   #1
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Default new idea (for me): dual first order building block PCB

I'm continuing on my quest to design some interesting and useful circuit boards for DIY audio. Here's my latest concept - a board that has two independent sections that can be used to build the following:
  • first order low pass filter (inverting)
  • first order high pass filter (inverting)
  • summing amplifier (inverting)
  • non-inverting amplifier
  • inverting DC-servo
  • non-inverting DC-servo
  • simulated inductor
  • grounded capacitance multiplier
  • LCR notch filter (using simulated inductor)
  • baffle step plus notch a la Sigfired Linkwitz
  • Baffle Step a la Rod Elliot (with adjustable baffle step)
It is also possible to configure the op-amp output to have a zobel, to isolate the amplifier's output from interference picked up by the cable it is driving.

All of these circuits are pretty useful for audio, especially for loudspeaker crossovers. The circuit that has two input paths for each of the amplifier inputs (inverting and non-inverting), two parallel negative feedback paths, and two output paths. Allowing for a couple components to be capacitors makes it possible to build the circuit footprint in many different ways to realize the range of circuits listed above. There may be other possibilities as well.

Today I did the PCB design. Everything fits on a 2x4 inch PCB along with a bypassed, DIP-socketed op-amp:

Click the image to open in full size.

-Charlie

Last edited by CharlieLaub; 16th February 2011 at 01:50 AM.
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Old 17th February 2011, 07:43 PM   #2
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Have you abandoned the "Universal Board"? I think it would be a better choice.
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Old 17th February 2011, 08:09 PM   #3
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Quote:
Originally Posted by TomHinton View Post
Have you abandoned the "Universal Board"? I think it would be a better choice.
No, both boards are still in development. They are separate concepts, although some of the capabilities (e.g. the circuits that can be created with each one) do overlap.

The "universal filter board" is more targeted at making HP or LP filters.

The "dual first order building block" board is more targeted at gain stages, DC servo, and baffle step compensation (1st order shelving filter) circuits.

Also, because of the greater complexity, the "universal filter board" has a 4x4 inch footprint, while the "dual 1st order building block" board has a 2x4" footprint. This will influence the production cost, which is proportional to board area.

-Charlie
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Old 17th February 2011, 11:52 PM   #4
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I've been looking for an op amp prototyping pcb for about a year now for my organ project. Yours is not quite it. Neither is anybody elses. See this thread gain block pcb's
Rules for organ prototyping 1. push in connectors don't work, the organ can knock vacuum tubes out of the sockets, that is why I am building something.
2. Wirewrap doesn't work on audio signals. The proof - 4 of the wirewrap connections in this 1968 organ have been soldered by dealer service. Something about low voltage signals and the oxide on the wire after a couple of years perhaps?
3. DIP-8 op amps are wonderful, but I can't solder reliably to the socket without causing bridges. Some pins on the dip need 2 or 3 connections.
4. 1/16" glass epoxy board is a **** to drill, so .1 perf board is really expensive.
5. 1/8" polycarbonate from the lumberyard is strong enough,& easy to drill but dip sockets and radial capacitors have leads shorter than that. 3 wrap dip sockets are available, which are over 1" tall, parasitic? and 3 wrap sockets are expensive.
6. axial components are easy to solder together, it is the dip that is the problem.
So I need 2"x3" or 2"x4" PCB's like SELECTRONIC ::: L'univers électronique ::: but there is not enough room on that PCB for the discrete components outlying. Besides, I've only found it in France, and the shipping and paperwork fee would be more than the $10 I want to pay for each PWB.
Your propsed PWB has not enough terminals next to the DIP for free form circuitry. I might not want first order filtering, I might want a differentiator or an integrator. Or a one-shot or other timer. Or a VCA envelope generator. The schematics are in the book. You've got a lot of dedicated traces to the discretes, that can be done very effectively by soldering solid core wire to them, with extra holes for strain relief on the wire.
Tonepad.com has a nice miniamp PWB, and a decent price, but he has no capacitor decoupling of the power supplies, not even the electrolytics, and above that modern (hifi) op amps like 33078 or 4560 need local disc caps on power supply and around the feedback resistor. Also he has dedicated circuitry.
Velleman's one op amp pwb, having been built by an organforum member, is stupid circuitry. Their disco mixer is worse.
Nightfire electronics kits has got something, but it comes with a sack of obsolete parts like 108's and 741's. Bleah.
I'm not going to etch myself, too nasty. My computer is too stupid (ubuntu) to run canned routing programs. And $25 each plus whatever for custom pcb's is beyond my budget. Mouser's budget boards all have the wrong pattern.
Still looking.
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Last edited by indianajo; 17th February 2011 at 11:59 PM.
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Old 18th February 2011, 12:20 AM   #5
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Quote:
Originally Posted by indianajo View Post
I've been looking for an op amp prototyping pcb for about a year now for my organ project. Yours is not quite it. Neither is anybody elses. See this thread gain block pcb's
Rules for organ prototyping 1. push in connectors don't work, the organ can knock vacuum tubes out of the sockets, that is why I am building something.
2. Wirewrap doesn't work on audio signals. The proof - 4 of the wirewrap connections in this 1968 organ have been soldered by dealer service. Something about low voltage signals and the oxide on the wire after a couple of years perhaps?
3. DIP-8 op amps are wonderful, but I can't solder reliably to the socket without causing bridges. Some pins on the dip need 2 or 3 connections.
4. 1/16" glass epoxy board is a **** to drill, so .1 perf board is really expensive.
5. 1/8" polycarbonate from the lumberyard is strong enough,& easy to drill but dip sockets and radial capacitors have leads shorter than that. 3 wrap dip sockets are available, which are over 1" tall, parasitic? and 3 wrap sockets are expensive.
6. axial components are easy to solder together, it is the dip that is the problem.
So I need 2"x3" or 2"x4" PCB's like SELECTRONIC ::: L'univers électronique ::: but there is not enough room on that PCB for the discrete components outlying. Besides, I've only found it in France, and the shipping and paperwork fee would be more than the $10 I want to pay for each PWB.
Your propsed PWB has not enough terminals next to the DIP for free form circuitry. I might not want first order filtering, I might want a differentiator or an integrator. Or a one-shot or other timer. Or a VCA envelope generator. The schematics are in the book. You've got a lot of dedicated traces to the discretes, that can be done very effectively by soldering solid core wire to them, with extra holes for strain relief on the wire.
Tonepad.com has a nice miniamp PWB, and a decent price, but he has no capacitor decoupling of the power supplies, not even the electrolytics, and above that modern (hifi) op amps like 33078 or 4560 need local disc caps on power supply and around the feedback resistor. Also he has dedicated circuitry.
Velleman's one op amp pwb, having been built by an organforum member, is stupid circuitry. Their disco mixer is worse.
Nightfire electronics kits has got something, but it comes with a sack of obsolete parts like 108's and 741's. Bleah.
I'm not going to etch myself, too nasty. My computer is too stupid (ubuntu) to run canned routing programs. And $25 each plus whatever for custom pcb's is beyond my budget. Mouser's budget boards all have the wrong pattern.
Still looking.
The PCBs that I am developing are not at all meant for the "free form" kind of development of circuits that you are speaking of, but are for a set of circuits that are useful for audio. I call one board the "universal filter board" because with it you can make pretty much every kind of filter that you would use in audio, well at least for loudspeakers, etc. But it is definitely not universally universal!

I have some leads for you, however. If you need some prototyping boards that you can solder up in a general way, I can suggest these reasonably priced boards from MCM Electronics:
Small IC Prototype Board | 21-110 (21110) | Distributed By MCM
Check out the full category at MCM:
Project Accessories - Circuit Boards - MCM Electronics - Category
Futurelec has some larger offerings:
Prototyping Boards
Circuit Specialists have these boards (and others, if you search the category "breadboards and prototyping boards" on their web site):
Circuit Specialists Inc. - UNI-BOARD Prototyping Boards

Hopefully one of these appeals to you for your project.

-Charlie
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Old 18th February 2011, 12:48 AM   #6
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I appreciate your work in typing up the links. Thank you.
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