PLS: If anyone has
any other upgrades modifications etc gladly I added here, will be useful for all of us:-)
Also if notice any error or misspellings please let me know.
A “Must” and Potential
to eliminate the hum noise. Remove
the unit from AC mains, remove both upper and bottom plates,
A must modifications.
All Orban 222A units from first to last
year of production no matter what SN #, all have two slight mains hum problems, I and
other technicians check lot of 222A units (about 15 pieces) we see that all suffered from
the same hum problems definitely it is a design miss?!! rather than just one faulty 222A
Its very strange that NON of users around the world don’t notice it that,
neither the factory report it with some supplements upgrade revisions as Orban factory
uses to add on his service manuals.
If on all outboard equipment’s before your main processor exist any slight mains hum
then this all adds up. Actually on real world, if one unmodified 222A is ahead of an
8100/xt2 then its hum is magnified by approx. 20+db by the 8100A1 AGC when the gain makeup
reaches its max.
To listen/check/notice the hum problem on yours 222A do the following.Suppose that your
222A is already on air alone or ahead of any processor.
On a dead air tune in with your fm tuner, turn-up the volume of headphones or monitor’s,
first listen carefully on Fm Stereo reception & then on Mono, at Fm Stereo reception
you should notice the mains hum at your on air, at Mono that low mains hum must minimized
or disappeared, the hum you listen on Fm Stereo reception comes from your 222A, to ensure
that simply pull-out the AC power of 222A.
Personally I notice that hum problems immediately as an 222A connected ahead of my
8100/xt2 before some years, after lot of unsuccessfully attempts to locate the source of
the problem, fortunately comes friend Paul, he is very clever, curious &
passionate with electronics and is very skilled with Optimod’s especially with 8100/xt2,
my friend Paul from UK (info “at” maximod.com) finds the cure of hum problems on 222A
and do some interesting upgrades modifications on 8100/xt2, also finds and eliminate the
“6Khz beat tone, whistle” noise which is heard on a dead air at Stereo “only”
reception on all Optimod’s 8200 (greetings
That two hum problems are, one at MONO audio chain which is not so serious, and second at
STEREO (L-R difference) audio chain is most serious because easily can heard on a dead
air. At MONO the hum comes from a ripple at out of negative regulator -15V if you scope
the out of 7915 can be see the ripple, and second at STEREO (L-R difference) hum comes
from inefficient GND of PIN 3 on IC7, if you scope the TP5 which is the L-R VCA out, then
easily may see the mains ripple.
For elimination of hum at
MONO, locate at PWS section the IC51 (7915) solder a short jumper wire from pin 1 of
IC51to E17 (center tap GND of transformer).
For elimination of hum at STEREO, locate the IC7 (5532) near of balance out modules,
solder a short jumper wire from pin 3 to E26 GND is between of L & R input cables
E1,2,3,4. Both above mods will make your 222A more quieter.
some proposes to lower the input noise level and how add some of StereoMaxx’s extra
effects? on your standard 222A.
the noise level of input. Standard
222A use NE5532 as input IC’s, his noise figures become worsen with variation of driver
resistance i.e. mixing console or any other outboard unit between 222A & mixing
console, so noise figures on this old workhorse 5532 depends much from what R see on his
input. For substantially reduced noise
replace IC1,2 & 7
check the noise figure on your standard 222A just set your scope to 5mv per division at
TP6 and easily may see lot of noise, also on TP6 may see the difference on noise level
between NE5532, OPA2134 & OP275 or other IC of your preference. Today with the great
evolution on audio IC there are exist some not so high priced IC’s with much better
sonic and dynamic results, one of the best IC used by many modern upgrades designers are
that of Texas
Instruments/Burr Brown OPA2134,
JFET input, very low noise figures with any variant of drive resistance, excellent
sonically character. Any way for those who wish to add on his 222A
some “impressing” “garbage” which gives that popular “wow factor”, here some
Another better replacement of NE5532 is the OP275 by Analog Devices that is one with
strange scheme Bipolar and JFET, designed especially for Hi End audio use, sonically
sounds better, warmer & smooth on my ears than of cold and dark OPA2134, so you may
give it a try. Now if you like the sonic character of NE5532 and wish to keep it, its
better to replace that old Signetics or Philips IC which is the two favorites vendors of
Orban factory with the same type of 5532 by that of Texas Instruments NE5532(A) the (A)
sign means that version of 5532 is selected and verified for lower noise also TI NE5532
sounds much better of Signetics or Philips.
some of StereoMaxx’s on your standard 222A
Be aware, with the following mod's your MONO will suffer.
As describe above on my results & opinion, 222A & StereoMaxx are the same on
overall way of treatment but with major differences on final “fake” widened result of
stereo image due the use of “digital delay” on L-R products (222Ais superior here due
non use such “baggy” “kitsch-y” tricks) also StereoMaxx expand stereo image on
50Hz-18Khz range & 222A due his pure design only at region of 900Hz-4Khz where is and
the usefully stereo information, for that and other reasons I like Bob’s design:) (if
expand the 20-20khz region of L-R then expand and lots of garbage:(
To open the freq. range of L-R products, thus the stereo image locate the C6 (470pf) on
IC7, that C is connected from pin1 to pin2 of IC7 and limits the high freq. results
the HF contains of L-R products, replace that 470pf with an 47pf. This mod gives on 222A
half of StereoMaxx
To add an delay on L-R products as on StereoMaxx, is not so easy job as the above mod but
maybe want to try this, many users make it with good results and especially without any
by-products as noise etc on StereoMaxx. Cut the PCB trace from TP5 which is the out of IC7
actually is the out of L-R VCA which going on R10 & R12 of IC1a & IC2 which is
L-R, L+R adder/buffers and add between one Phase Rotator circuit similar that of used on
input of any broadcasting processor (look at below given scheme). The Phase Rotator
circuit act as x1 buffer on L-R audio levels so no worry for any trouble, his effect is
good enough on stereo width image because his phase rotation is depended by the freq. that
scheme by its self as all Phase Rotator circuits add some delay “echo”, if you use
more of there or six cascaded such given circuits then the delay on L-R products is
longer. For IC you can use and here OPA2134,
the indicated tolerance for grounded capacitor is for rotation freq. under of about 400hz,
(vocal low region) for higher freq. use smaller tolerance, freely you can experiment to
catch your preferred results.
That’s all folks, I don’t have any other modification.
You play enough, now its time
to restore yours 222A at his original state:)
try to give some appeal of today digital toys on your old analogue units,
leave it as IS in PEACE, if you want to play with digital toys then go to buy one. DON’T
try make your analogue unit a horribly “Frankenstein” unit.