Theremin components

Hi,
I'm building the EM theremin from this article: =http://www.cs.nmsu.edu/~rth/EMTheremin.pdf]

At the moment i can't find these parts:
1: LM781L12 12V positive regulator
2: LM79L12 12V negative regulator
3: LM1360ON dual operational transcondance amplifier (National Semiconductor)
4:33 ìF/50V, 5%, NPO (zero temperature coefficient) ceramic capacitor
and 5: 10 mH, 3-section, RIF choke (J. W. Miller #6306)

I'm still really new to electrical engineering and would also like help on the actual building of the theremin, or at least how to read the schematics.

Any help would greatly be appreciated!!

EDIT: I also need the Cui-Stack DPA120020-P1-SZ but don't want to spend $50!!! Is there any other plug that will work?

EDIT2: Okay last piece I need is the connector set with at lest ten conductors for connections between the main circuit board and front panel, but I don't know what those are or what to do with th

[i]At the moment i can't find these parts:
1: LM781L12 12V positive regulator
2: LM79L12 12V negative regulator
3: LM1360ON dual operational transcondance amplifier (National Semiconductor)
4:33 ìF/50V, 5%, NPO (zero temperature coefficient) ceramic capacitor
and 5: 10 mH, 3-section, RIF choke (J. W. Miller #6306)

I'm still really new to electrical engineering and would also like help on the actual building of the theremin, or at least how to read the schematics.

Any help would greatly be appreciated!!

EDIT: I also need the Cui-Stack DPA120020-P1-SZ but don't want to spend $50!!! Is there any other plug that will work?

EDIT2: Okay last piece I need is the connector set with at lest ten conductors for connections between the main circuit board and front panel, but I don't know what those are or what to do with them [/i]

1,2 Any low power +12 and -12V regulators (I assume the circuit consumption current is less 50 ma). The pin arrangement may be different from LM78/79, see datasheets. Also you can use dual regulators, for example OM3905SC.

4. The 33 uF/50V capacitor is declared in the part list, but in schematic C9 is 33 pF. I think (according the operating principle) the real C9 must be 33 pF.

Singe they die from time to time, I've always some spare 78L12 and 79L12. I order them without problems on eBay for a few cents. The overall power consumption of the EM is about 75mA, so at least 100mA rated voltage regulators are required in order to support the initial current peak when switching it on before the oscillators start working and the tank circuits go into high-Z mode.

The LM 13600 is not longer produced and may be replaced by a LM 13700 which you'll also find on eBay for a few bucks.

The 33pF ceramic capacitor must not forcibly be a NPO type. You may use a normal ceramic capacitor. The NPO has a somewhat better temperature stability, but the difference is not so important in this type of reactance circuit. The junction capacitance of the transistor in parallel varies much more.

The 10mH Miller coils may be replaced by the actual Hammond 1535G type which is sold by tubesandmore.com on catalog page 37 for 5.20$.

IMHO it makes absolutely no sense to use 'L' (100mA) regulators - particularly if you are making a 'breadboard' Theremin (like the EM version of the EW) or are designing your own PCB.

Standard 1A 78 / 79 regulators are virtually the same price, can be dropped into the circuit to replace the 100mA parts, can dissipate happily if the input voltage is on the high side, and, in all, are a much better / safer option if size is not a major issue.

There are also lots of modern 3 terminal regulators with a better specification than the 78 / 79 family.. lower drop-out, better regulation etc - and most of these are pinned the same as the 78 / 79 family.. mostly +Ve.. IMO the better solution is often to use an adjustable +Ve or -Ve 3 terminal regulator - two resistors set the required voltage, so you can buy a batch and 'program' them to any required voltage - or you can do 'exotic' things with them like using them with a bandgap shunt regulator to give extremely precise regulated voltages with high current and virtually no change in output voltage over a wide temperature range or loading.

Power supplies! IMO these are often the weakest link in designs - Designers love doing the exciting stuff, and use a bench supply for testing .. Then, almost as an afterthought, realize they need a supply they can ship in the product - LOL - so a few quick calculations (ignoring worst-case scenarios) and its "stick a 78Lxx in.." Advice .. If one cannot stand the boredom of designing a good PSU, at least go for overkill on the regulators and decoupling! - A big regulator will have less temperature change than a small one, and this, alone, will improve regulation.

;-)

Fred.

http://cds.linear.com/docs/Datasheet/1086ffs.pdf

I agree with Fred ... LM740T-12, 7812, LM320T-12, 7912 are easy to get from Digikey, Mouser, Fry's and most other local-to-your-area electronics stores. National Semiconductor has a nice Power Supply Handbook that has great information on how to design simple linear power supplies.

[i]"National Semiconductor has a nice Power Supply Handbook that has great information on how to design simple linear power supplies.." - Don [/i]

Hi Don, Not sure about the "has" - I think it may be a "had"! .. My NS "Voltage Regulator Handbook" is dated May 1975 - it has been well used! ;-) Then I have the NS "Linear Circuits - Voltage regulators and supervisors" book dated 1989.

These books (particularly the "Voltage Regulator Handbook") give all the most important 'practical theory' but I cannot find them on-line.. There are lots of other linear power supply design guides though - just search for linear regulator and/or linear power supply design and one gets pages of hits.

Somehow, the "old days" were a lot easier though - we had a few good books to guide us, and when a new, better part came on the scene, we all learned about it quickly..

These days we are drowned by incomprehensible volumes of data, and new parts come and go weekly -

too much of a good thing...

Fred.

So I take it that parts can be substituted as long as they have the same values?
I.E a mulitlayer ceramic capaictor with 50V for a normal ceramic capacitor with 50V?

And thank you ILYA, I could find plenty of the capacitors for 33pf, but I don't know how much the circuit consumption is...

[i]"So I take it that parts can be substituted as long as they have the same values?
I.E a mulitlayer ceramic capaictor with 50V for a normal ceramic capacitor with 50V?" - Wildfire [/i]

Yes, and no.

With capacitors, the vital parameters are capacitance and voltage.. but (like everything else in electronics) there are other factors which can make a huge difference..

A real capacitor is, in itself, a quite complex circuit - it has series resistance and inductance, it has its dielectric whose charactaristics are temperature dependent, and it has other 'imperfections'.

If you do not understand the above (cannot go through a component data sheet and determine the suitability of the component) then you are best sticking to the specified component. IMO you would be best sticking to a NOP or COG (COG is basically another way of saying NOP) capacitor.. Sure, there may be (are) other factors which may dwarf the thermal effect of the capacitor - but if Bob Moog specified NOP, I am inclined to think he reasoned that it was worth having!

You will find it hard (impossible?) to get 33p 50V COG - but you can get 33pF 200V COG (http://uk.farnell.com/multicomp/mcrr25330cogj0200/capacitor-33pf-200v/dp/1216408) easily, and these are fine.

As for power consumption - the circuit specifies 78L and 79L regulators, so you can assume current will be less than 100mA.. So replace these 'L' parts with standard 78/79 (1A) parts, and you will be safe.

Fred.

ah, well the main reason i asked is because the ceramic capacitors needed don't specify weather or not they should by multilayer, because those are the only ones i can find

multilayer ceramic NPO/COG should be fine. Most ceramic C's these days are multilayer, and unless otherwise specified, one can assume 'ceramic' is 'multilayer' - particularly if larger values (>50pF) are required.

To get single layer with large capacitance, one needs a big plate area and extremely thin, high K dielectric.. even 33pF might be difficult to make as a small, low cost single-layer NPO component.. high K dielectrics tend to have bigger thermal coefficients.. NPO dielectrics are usually a mix of dielectrics having +Ve and -Ve coefficients which act against each other to give near zero coefficient.. one can achieve nearly the same result by using 2 capacitors and selecting their coefficients so that these cancel each other out - but this is a lot of bother, and only really worth doing for larger capacitances where one cannot buy NPO.

Fred.