Oakley PCB Issue 2 User manual

Oakley Sound Systems
Power Supply Unit (PSU)
PCB Issue 2
User Manual
V2.3.
Tony Allgood B.Eng PGCE
Oakley Sound Systems
CARLISLE
United Kingdom
1

Int oduction
This is the Use Manual fo issue 2 of the PSU ci cuit boa d f om Oakley Sound. The Oakley
PSU is a powe supply unit designed to be used in conjunction with the Oakley Dizzy powe
dist ibution system.
When built onto the 3U maste panel the maximum peak cu ent output is 520mA pe ail
using the ecommended Yamaha PA-20 powe supply. When built onto the la ge 4U 19” ack
panel and using the Yamaha PA-30 powe supply the maximum cu ent d aw is 780mA pe
ail.
It is possible to upg ade the powe supply's maximum cu ent capability using a diffe ent
powe sou ce and suitable smoothing capacito s and app op iate heatsinking.
As well as giving details as to what the PSU boa d does, this document contains inst uctions
on how to wi e up you boa d to you sou ce of powe , any exte nal switches and the optional
powe indicato s. We will also look at the Oakley powe buss and how it diffe s f om the
MOTM one yet etains complete compatibility with it. I will also give you some info mation
about suitable sou ces fo you low voltage AC powe supply.
The Oakley PSU allows fo va ious options in the installation. You can use the unit eithe in
full wave ectification mode fo connection to tapped linelumps o twin t ansfo me
seconda ies, o in half wave ectification fo single phase AC output wallwa ts and linelumps.
If all this sounds ve y confusing at the moment, do not wo y, in this manual I will t y to make
it clea e so that you make the ight decision about what powe sou ce you will need.
If you a e building the PSU as a complete DIY p oject please also download the latest
Builde 's Guide. This can be found on the main PSU webpage along with ou ve y useful
gene ic pa ts and const uction guides.
2

Safety Wa ning
This supply has been designed to wo k with isolated low voltage AC inputs only. Connection
to any othe supply is done at you own isk. Low voltage is classified as being less than 25V
with espect to the g ound potential. Voltages above this level can, and often a e, lethal to
living c eatu es.
Oakley Sound Systems will not advise on building o modifying this boa d to allow fo di ect
connection to the mains, o othe high voltage sou ces, fu the to what is p ovided in this
document. Please do not ask us fo additional info mation pe taining to di ect mains
connections o using inte nally mounted t ansfo me s as we will not give it.
For safety and legal reasons we cannot recommend powering this board from any other
supply than low voltage AC output mains adapters.
Oakley Sound Systems a e not liable fo any damages caused by the misuse of this p oduct. It
is you esponsibility to use this p oduct safely. If you have any doubt about installing a safe
powe supply, then please do not attempt to do so.
3

The Oakley PSU module
The powe supply boa d will allow the conve sion of a suitable low voltage alte nating cu ent
(AC) to be ectified, smoothed and egulated fo ope ation with the Oakley Modula . The
module is designed to be fitted to a suitably la ge metal panel which functions as a heatsink fo
the se ies pass devices connected to the PSU ci cuit boa d. This metal panel should have
adequate ai flow a ound it. An example of such a panel is ou 3U wide maste panel which
also contains a handy multiple and powe switch. You can also use a 4U high 19” ack blank
panel. These a e pa ticula ly suitable if you a e mounting you modula synth in a 19” ack.
The g eate su face a ea on the 19” blank panel allows you to mount not only the powe
supply module but also up to two Dizzy PCBs. And the g eate su face a ea also allows the
powe supply's powe devices to dissipate mo e heat safely and that means a g eate cu ent
output should you need it.
A standard 4U high 19” panel with an Oakley PSU and single Dizzy. This would e suita le for powering
up to 12 Oakley modules. Note the grounding point just elow the main power inlet.
The voltage output of the powe supply module is a split ail 15V supply. This means it
gene ates both +15V and -15V. That is, two powe ails, one of a positive voltage, the othe a
negative one. These voltages a e measu ed with espect to a common g ound which is
no mally connected, via you house's wi ing, to the ea th that you stand on. The voltage
ac oss both ails is 30V, with the common g ound sitting exactly in the middle of this at 0V.
The output cu ent capability is the maximum cu ent you can d aw out of the powe supply.
The cu ent taken f om the supply is, fo the most pa t, dete mined by the amount and type of
modules you a e connecting to the powe supply. Howeve , the actual patch also has an effect
on the cu ent d aw – the mo e outputs that a e connected to inputs inc eases the cu ent
d aw slightly. Also, some LEDs when lit may inc ease the cu ent d aw.
The Oakley PSU featu es cu ent limiting. This sets the maximum cu ent the powe supply
will actually p ovide. If you t y to d aw mo e than the limit the output voltage will fall to
maintain the cu ent at the limit value. The cu ent limit is set by two esisto s, R2 and R3, on
the PSU boa d. It is essential that you make the cu ent limit esisto s suit you application.
The next section, and also in the pa ts list of the Builde 's Guide, will give details on what
values to use.
I ecommend that you use a Yamaha PA-20 o PA-30 powe supply. These a e neat tidy
exte nal powe supplies that keep the dange ous mains voltage away f om you modula . The
PA-20 will allow a maximum cu ent of 520mA (0.52A) to be d awn f om each ail. While the
4

PA-30 will allow up to 780mA (0.78A). Remembe though you can't use a PA-30 with the 3U
maste panel and expect to d aw 0.78A out of it without the panel getting too hot. If you a e
using the 3U maste panel then you should d aw no mo e than 0.52A pe ail.
If you a e using a 500mA (o 0.5A) AC wallwa t* then the most cu ent you can take f om
this powe supply module is 125mA f om each ail. That is, take no mo e than 125mA f om
eithe the +15V supply o the -15V supply. Most Oakley modules take a ound 20 to 30mA
each f om both the +15V and the -15V ails. That means you should est ict you self to
d iving a maximum of five o six synthesise modules in you system if using 500mA wallwa t.
Howeve , you must emembe that some modules may take mo e that 30mA. So check with
the module's Use Manual o webpage to see how much cu ent each one takes.
Va ious companies make linelumps** with a g eate capacity than 500mA. If you can get a
1A output one than this will be able to d ive up to 250mA pe ail.
Some linelumps, like the Yamaha PA-20 and PA-30, use a split AC output o a cent e tapped
AC output. This means it has th ee wi es coming f om it and will use a diffe ent plug f om the
usual ound ba el one you see on the single phase AC wallwa ts. Single phase mains adapte s
have only two wi es coming f om them so they can use a simple connecting plug.
The Oakley PSU is ecommended to be used with full wave ectification. This allows it to
utilise split AC outputs ve y effectively. The Yamaha PA-20 supply is ated to give an output
voltage of 35Vac (with a cent e tap) at a load of 0.94A. Once ectified and smoothed this
means that a maximum cu ent of 0.52A can be d awn f om the PA-20.
Two sets of sc ew te minal blocks a e p ovided fo connecting the low voltage AC powe
sou ce to the boa d and the optional powe switch. If you a e using a single phase wallwa t to
powe the PSU module than you need only to use two te minals pe te minal block.
The boa d has fou mounting holes fo stable placement onto you modula case. Ca e should
be taken so that the boa d's va ious boa d mounted components do not come into contact with
any pa t of you modula 's enclosu e. One of the holes, the bottom ight hand one, is
connected to the g ound pins of the two output te minals via a ' esisto ', R13. In most
situations R13 is a wi e link thus ensu ing that the panel the PSU module is fitted to is
connected to 0V o g ound of the powe supply.
The powe supply has two integ al fuse holde s in case of a p oblem with the powe supply
ci cuit y itself. Two fuses a e needed if you a e using full wave ectification, but only one, F2,
is equi ed fo o dina y half wave ectification. The fuse type should be a slow blow o anti-
su ge type. The size is 20mm. It should be ated at between one and two times the maximum
cu ent of you wallwa t. Thus a 500mA AC output mains adapte should have a fuse that is
ated between 500mA and 1A, ideally 750mA. A 1A linelump should have a fuse that is
between 1A and 2A, ideally 1.5A.
Th ee on-boa d LEDs, one fo +15V, one fo -15V and one fo the AC input, p ovide a quick
visual efe ence that all is well. All th ee LEDs could be fitted exte nally to the boa d and be
mounted on a f ont panel. Howeve , the ecommended way is to mount only the AC indicato
on the f ont of the synthesise along with the AC powe standby switch.
5

As we have seen the standa d ci cuit p ovides two outputs, one at +15V and one at -15V.
Both output voltages can be finely adjusted with just one t imme . The -15V will
automatically t ack the output voltage on the +15V.
The output voltages a e available f om two sc ew te minal blocks. It is expected that each
te minal block will be connected to one Dizzy boa d. Howeve , you can with ca e connect
mo e than one Dizzy boa d to each output block. We do not ecommend that multiple Dizzy
boa ds be connected in daisy chain fashion. That is, each Dizzy boa d should go back to the
PSU sepa ately.
* A wallwa t is the ve nacula te m fo a low voltage mains adapte that plugs di ectly into the
wall. These take the fo m of a black plastic block that is shaped like an ove sized mains plug.
It is called a wa t simply because its appea ance is somewhat uglie than a no mal slimline
plug.
** A linelump does the same job as a wallwa t but it gene ally can handle g eate cu ents.
Because of its inc eased size it cannot be made so that it will safely fit into a plug socket
di ectly. Thus the adapte sits in a black plastic box and connects to the wall via a cable and
t aditional mains plug. It is the efo e a black plastic lump connected to a line. The Yamaha
PA-20 and PA-30 a e such linelumps.
6

The Powe Supply to the Powe Supply
The inlet, switch and LED wiring on a 19” panel assem ly. The top connector is the power supply inlet
coming from a PA-20. The middle unch of wires is for the two pole DPST rocker switch. At the ottom is
a red 5mm LED in a low profile clip connected to the oard via my usual Molex KK method.
The standa d method of powe ing the unit is f om a low voltage tapped AC sou ce. The safest
available option is to use a eady made 'wallwa t' o ‘line lump’ supply.
You can use any 15V o 18V AC output wallwa t of linelump you can sou ce. The cu ent
capability of the mains adapte , sometimes inco ectly called the 'ampage' will dete mine the
maximum cu ent d aw of you PSU.
Fo use with this boa d I ecommend the Yamaha PA-20 and PA-30 supplies.
Yamaha PA-20
This is a linelump supply and featu es a fixed 17.5-0-17.5 volt AC output at 0.94A maximum.
This means it gives us two AC outputs with a cent e tap o mid point efe ence voltage. So
unlike the single phase AC adapte output with two leads, this one has th ee. This means you
need to use the Oakley PSU in full wave ectification mode.
The PA-20 is made fo Yamaha p oducts and they a e available f om Yamaha spa es
depa tments as well as many music shops, eg. Thomann. These a e CE app oved and connect
to the mains via you local mains connecto . They will be diffe ent types depending on the
count y you need them fo . It comes with a handy th ee way plug at the low voltage end that
you can use with an app op iate socket. If you wish you can ditch thei connecto and use
7

you own. Maplin in the UK sell a suitable th ee way connecto to fit the Yamaha one
pe fectly. Thei pa t numbe is FM51F.
In the UK the line lump’s pa t numbe is V9812300 and the total cost is a ound £30 including
VAT and postage. We do have pe mission f om Yamaha-Kemble in the UK to use this
pa ticula pa t fo the Oakley system, but in othe count ies this may be not so clea cut. The
liability issue once again ea s its ugly head and they may not want to sell powe items fo
thi d pa ty use. If you a e buying these di ect f om Yamaha and, fo some eason, a e asked
why, the best thing is to say it is fo you own MG12/4 mixe .
Once ectified, smoothed and egulated the Yamaha PA-20 can delive up to 0.52A
continuously into both 15V ails. The cu ent limit esisto s on the Oakley PSU, R2 and R3,
should both be 1R esisto s.
You should fit both fuses and both should be anti-su ge types and ated between 1A and 1.6A.
The European version of the PA-20. Other country's units are similar ut will have the local mains
connector fitted.
Yamaha PA-30
This is essentially a bigge ve sion of the PA-20 as detailed above which supplies 18V-0-18V
at 1.4A maximum. Once ectified, smoothed and egulated it can supply up to 0.78A
continuously. Make R2 and R3 both 0R82 to set the cu ent limit to a ound 0.78A. Again,
you should fit both fuses and both should be anti-su ge types and ated between 1.5A and 2A.
8

The following supplies may also be used but have not yet been tested:
Maplin N57AT
This is a 500mA single phase AC output wallwa t. It is a va iable output type. This means it
has a little selecto switch on the unde side of the unit that allows you to change the output
voltage. You should select 15V fo ope ation with the PSU boa d. I do not ecommend you
take mo e than 125mA pe ail. R2 and R3 on the PSU boa d should the efo e be 2R7
esisto s.
Because this is a single phase unit the Oakley PSU is wi ed in half-wave ectification mode.
You notice that only two wi es come out of the wallwa t and that you can select f om a
va iety of output socket types. Simply chose the one you would like to use on you system
and buy the app op iate socket fo it to go into. I tend to ecommend the 2.5mm DC powe
plug one since this is the most common type of powe socket.
You should fit fuse F2 only and it should be an anti-su ge type and ated between 500mA and
1A.
Maplin N58AT
This is a 1A single phase unit. It has the potential to delive up to 250mA pe ail when the
Oakley PSU is used in half wave ectification mode. Make R2 and R3 both 1R5 esisto s.
If you have successfully used the Oakley PSU with any othe types of powe pack please do
let me know eithe di ectly o via the Oakley Sound fo um at www.muffwiggle .com
9

Linelumps and Wallwa ts: Wi ing Diag ams
Input wi ing will depend on the type of wallwa t o linelump you will be using.
Standard AC output wallwart
Single phase, two wi e, wallwa ts o linelumps need to use half wave ectification so the
Oakley PSU can gene ate both positive and negative supplies simultaneously. They only need
the te minal's AC1 and 0V2 wi ed to the powe socket. AC2 and 0V1 a e left unused.
Wallwart with single phase AC output, eg. Maplin N57AT
The f ont panel switch is a single pole single th ow (SPST) switch which simply connects S1R
and S1S togethe when switched on. You can eplace the switch with a simple wi e link, but I
do ecommend that a switch be fitted so the socket doesn't have to take the full su ge cu ent
when you inse t it with the wallwa t powe ed up.
I also ecommend fitting the AC indicato LED too. This is so you know the wallwa t o
linelump is on. The AC indicato is designed to indicate the status of incoming powe and is
not dete mined by the position of the standby switch.
The standby switch should not be used to tu n the unit off pe manently. This should be done
by eithe switching the adapte off at the mains socket, o by pulling the adapte 's plug out of
the mains socket.
An optional ea th o g ounding connection can be made. See late fo mo e details.
10

Recommended Option: Centre tapped wallwarts and linelumps
Cent e tapped linelumps like the Yamaha PA-20 will have th ee wi es coming f om thei
connecto . It will have two AC outputs and one 0V. Take one of the AC outputs to te minal
AC1 and the othe AC output to te minal AC2. It should not matte which AC output goes to
AC1 o AC2. The 0V should go to the 0V2 te minal. The 0V1 te minal is left unused.
Figure 2. Linelump wiring with centre tapped output, eg. Yamaha PA-20
The f ont panel switch is a double pole single th ow (DPST) switch which connects S2R and
S2S togethe , and S1R and S1S togethe , when switched on. You can eplace the switch with
two wi e links, but I do ecommend that a switch be fitted so the socket doesn't have to take
the full su ge cu ent when you inse t it if the linelump is powe ed up.
I also ecommend fitting the AC indicato LED too. This is so you know the linelump is on.
The AC indicato is designed to indicate the status of incoming powe and is not dete mined
by the position of the standby switch.
The standby switch should not be used to tu n the unit off pe manently. This should be done
by eithe switching the adapte off at the mains socket, o by pulling the adapte 's plug out of
the mains socket.
An optional ea th o g ounding connection can be made. See next section fo mo e details.
11

Linelumps and Wallwa ts: Fitting a G ounding Point
Using double insulated wallwa ts and linelumps mean that you do not have to have a mains
safety ea th fitted to you modula . Howeve , if you modula is to talk to the est of the
studio you need to make su e that the modula 's g ound is tied to ea th somewhe e in you
system. The most usual way of doing this is via the connecting cable's shield o sc een
connection. You mixing desk o monito ing equipment will be ea thed and simply connecting
a cable to any module within you modula will tie the modula 's g ound to the othe
equipment's ea th. This seems p etty st aightfo wa d and it is so long as you have a small
system and only have one o two inte connecting cables in use.
Howeve , a la ge mo e complex system will have pe haps mo e than one modula , mo e than
one mixing desk and pe haps a heap of othe outboa d equipment. This is when it makes sense
to look at g ounding you modula cases togethe .
A 4mm anana socket eing used as a common grounding point for a rack power supply. Here the
anana socket is connected directly with a nice thick piece of wire to the spare 0V1 screw terminal.
Let us conside a mo e simple scena io fo the moment. Say we have built ou selves two
modula cases and we would like to connect the modules in them togethe to fo m an
awesome monste patch. Each case has its own PSU and each one is powe ed by a Yamaha
PA-20. It is useful in this situation to ensu e that both PSUs a e g ounded togethe . In othe
wo ds the two 0V lines f om each powe supply a e fi mly connected togethe . Although this
will be done the moment that one patch lead goes f om one case to the othe it is beneficial to
do this with a dedicated bonding wi e.
We can do this in a va iety of ways but one useful method involves having a 4mm banana
socket mounted nea each powe supply. The banana socket is connected to 0V on the PSU
boa d. The cu ently empty 0V1 sc ew te minal on the PSU boa d p ovides a ve y handy point
to connect the socket.
12

If both powe supplies have a banana socket then it is a simple matte of patching the two
powe supplies togethe with a banana patch lead. The nice thing about bananas is that they
a e stackable so it's easy even if you have mo e than two PSUs to connect up.
I ecommend that you use thick multist and cable to make you g ounding leads and that you
use good quality 4mm banana sockets and plugs.
13

Using an Inte nal Mains t ansfo me
Be af aid, be ve y af aid...
Some of you old hands will laugh about the level of hyste ia that su ounds di ect mains
connection to DIY p ojects. Howeve , this fea is mo e to do with ou litigious society than
the eal dange to the builde . Even so, I have had mo e than my fai sha e of high voltage
shocks ove the yea s and it is not something I would want any builde to have to expe ience.
It has been pu ely luck that has saved me in seve al of those cases.
So I will say again – do not attempt to build a mains t ansfo me into you modula case, o
any othe p oject, without ealising that to do so ca ies a isk of death to eithe you, o to the
pe son who may inadve tently put thei finge s into you half built const uction. Fu the mo e,
it is up to you as the builde of such an item to make su e, that once built, the item is safe to
use and meets all cu ent safety legislation.
This is not a complete set of instructions on how to fit a transformer into a piece of
electronic equipment. This information is offered only as a guide and should not be
considered as your only source of information. No further information, other than that
included here, will be provided by myself or Paul Darlow regarding the construction of
mains powered items.
The mains t ansfo me 's seconda ies should be ated:
18-0, 18-0 (or 18-0-18)
80VA
This will give you a powe supply that should be theo etically capable of just ove 1A each ail
assuming you heatsink and smoothing capacito s a e up to the job. In this case you should
make both R2 and R3 0R56 2W esisto s.
Take note that the 5U high 3U wide f ont Maste Panel design is insufficient to ca y away the
heat safely when continuously supplying ove 520mA pe ail. A diffe ent method of mounting
the powe devices must be found unless you limit the maximum cu ent to less than 520mA.
The 4U 19” panel detailed ea lie may well be adequate fo a 1A supply but emembe that the
seconda y voltage will affect just how much heat needs to be dissipated. It is up to you to
ve ify that you chosen panel is up to the job of keeping those powe devices cool. Remembe
that ai flow to the panel is essential so make su e any tests you do a e ep esentative of the
situation you heatsink will eventually be fitted to.
The t ansfo me seconda y voltage is suggested to be 18V. Slightly highe t ansfo me
seconda y voltages can also be tole ated although you need to conside th ee things:
1. You may need a physically la ge t ansfo me fo the same output powe .
14

2. The powe supply's components, including the smoothing capacito s, should be ated at a
high enough wo king voltage to handle the inc eased voltage ac oss them.
3. The heatsink will need to dissipate even mo e ene gy because of the g eate voltage d op
ac oss the egulato s.
In the wi ing diag am shown on page 17 I have included a suggested wi ing method fo
connecting up a mains t ansfo me . Not all mains t ansfo me s a e the same, some have
additional windings, othe s have tapped windings. I have simply used a single p ima y, double
seconda y type fo example only. Note that whateve type of t ansfo me you use do not
connect any of the seconda y wi es to 0V1. 0V1 is p ovided fo optional ea thing pu poses
only and should not ca y any cu ent f om the t ansfo me .
Fo the mains fuse you should use a 500mA anti-su ge type. All wi ing at mains potential
should be adequately insulated and p otected f om st aying finge s.
The e is no need to fit an AC standby switch since you will be fitting a p ope mains powe on
switch in se ies with the t ansfo me p ima y coil. So you should link S1A to S1R, and S2S to
S2S, on the PCB.
Earthing
Remembe it is up to you, the builde of the equipment, to make su e that you item is safe
and is built to the equi ed safety standa d in you count y. These notes a e only a guidance
and it is up to the eade to establish the exact obligations equi ed in thei own count y.
It is essential that eve ything you build, that has both live mains inside and a metal case o
panels, has a safety ea th fitted. UK legislation says that any metal panelling should be
adequately insulated, ie. double insulated, o connected to ea th. Since making a double
insulated case is not p actical you should ensu e that any exposed metal pa ts be p ope ly
ea thed.
Fi stly you need to ensu e that the heatsink is ea thed. Given its size and equi ed ai flow this
will ce tainly be an exposed piece of metal and thus should be ea thed well. It should be
bonded to ea th via a thick piece of wi e back to the ea th tang of the IEC powe inlet o a
common ea th bonding point.
The PSU boa d should be secu ely mounted (using all fou mounting holes) onto the ea thed
heatsink using app op iate sc ews and toothed washe s. R13 on the powe supply boa d
should be a wi e link. This should ensu e that the powe supply g ound (0V) is tied to ea th.
R2 on each Dizzy is p ovided to join the Dizzy's ea th pad to pin 3 of the powe heade s. Pin 3
ca ies the panel g ound in an Oakley system although in a mixed MOTM system it will also
be the module g ound, o 0V. To bond the panel g ound to ea th via a Dizzy boa d you should
make R2 a wi e link and connect each Dizzy's ea th pad back to the IEC socket o common
ea th bonding point. Again use a thick piece of insulated wi e to make the connection.
15

Howeve , this alone may not be sufficient fo a solid safety ea th bond. All panels should be
ea thed di ectly, eithe with thei own di ect connection to the ea th tag on the powe inlet, o
via the modula 's ea thed metal mounting ails and suitable toothed washe and sc ew. If you
have a wooden case with wooden mounting ails and you a e toying with the idea of using a
mains t ansfo me in you DIY powe supply p oject then you may want to ethink you plans.
You will also need to p ovide ea thing to any exposed t ansfo me co e. This does not apply
no mally to to oidal types but EI types should have thei metal f ame ea thed.
It is possible that by ea thing the f ont panel you may int oduce ea th loops when you connect
you mixe to the sockets of one of the modules. The outcome of this is audible humming at
50/60Hz and its ha monics. It is p oduced by ea th cu ents t avelling down the sc een of the
connecting cable(s). This can be avoided by ca eful studio wi ing and/o by using balanced
audio lines to pipe signals to and f om the modula and mixing desk. Most mixing desks will
have balanced outputs and inputs.
16

Mains wiring diagram. For experienced uilders only!
17

The Oakley Powe Bus
In an ideal wo ld I wanted the Oakley powe bus to be based on a five way 0.156” MTA o
Molex connecto . This would contain +15V, -15V and th ee g ounds. One g ound would be
the safety g ound; this would be connected to the f ont panels and then di ectly onto the
main’s supply ea th. The second would be a clean g ound fo all the analogue modules to take
thei supply efe ence, the ze o volt line, ie. 0V. The thi d would be a di ty g ound. This
would be the g ound efe ence fo things like the noisy digital ci cuit y and LED switching.
Howeve , this system would be incompatible with the MOTM modula which has a fou way
connecto fo its analogue modules. So the question now emained, how could I make my
system wo k with MOTM, yet still etain some of the featu es I needed.
The chosen Oakley powe bus comp ises of +15V and -15V lines with two g ounds. These
g ounds a e not connected togethe as in the MOTM. They a e joined only at the powe
supply in a wholly Oakley Modula .
In an Oakley modula one of the g ounds, pin 2, goes st aight to the powe supply’s sta
point. This is the analogue efe ence point and is co ectly called 0V o module g ound. This
is the same as the MOTM g ound. The second g ound is on pin 3. This is also connected to
the powe supply’s g ound. But this g ound is connected only to the metal lugs of the sockets
on each module and nothing else on the module. It is this connection that sets the potential of
the patch lead’s sc eening and the metal case of the modula . This way it is impossible fo
g ound cu ents to t avel down the inse ted patch co ds, since the panel is isolated f om the
system g ound except at one point.
Howeve , this only wo ks if ALL you modules follow this ule. If you inse t just one MOTM
module into this system, the ‘benefits’ a e lost. MOTM modules can be modified to allow full
Oakley compatibility although this should be done as you a e building the module. Modifying
a completed MOTM module is possible, but the eve se side of the PCB must be accessed so
that you can cut the equi ed t acks.
But I said ea lie that the MOTM and Oakley powe systems we e compatible. And indeed
they a e. Any Oakley module will wo k in a MOTM system. And vice ve sa. But you will not
get the inhe ent advantages of a two g ound system if you mix and match systems.
Having said all that I have yet to hea any p oblems elated to g ound cu ents in any MOTM
o MOTM/Oakley systems.
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Final Comments
I hope you that the Oakley PSU lives up to you expectations and p ovides you with a eliable
sou ce of powe fo you modula system.
If you have any questions about the module, an excellent sou ce of suppo t is the Oakley
Sound Fo um at Muffwiggle .com. Paul Da low and I a e on this g oup, as well as many othe
use s and builde s of Oakley modules.
If you have a comment about this use manual, o have a found a mistake in it, then please do
let me know.
Last but not least, can I say a big thank you to all of you who have helped and inspi ed me
ove the yea s. Thanks especially to all those nice people at Muff's and the Synth-DIY and
Analogue Heaven mailing lists.
Tony Allgood at Oakley Sound
Cumb ia, UK
© Octobe 2010 – updated Octobe 2012
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