garxxxx(OA10) support thread

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gar381

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Jan 27, 2005
Messages
1,123
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Retired in (Amherst) Cleveland, Ohio
NOTE FOR FOLKS SOURCING THEIR OWN PARTS>>>>

There are a few part # errors in the BOM in the current manual.

R2 & R5 is 2.7K  the correct part # is
MOUSER 271-2.7k-RC ( NOT 271-2.7-RC)

R9 is still 3.3R  1/2 watt                                                               
MOUSER 293-3.3-RC
(NOT 291-3.3-RC)

CD1 & CD2  Part number should be
594-K104K15X7RF5TL2 (NOT 594-K104K15RX7RF5TL2)

There will be an updated fixed manual soon in the doc section at the CAPI store.
Look for REVISED added to the link.


Just another note here..
Mouser seems to be having trouble with stock
on R8  (293-10-RC) at the moment.  You can use
660-CF1/2C100J as a sub if necessary. 

---------------------------------------------------------------

The NEW garxxxx(OA10) DOA will work from +/- 15V  thru +/-24V so it is a
Happy camper on any VPR or 51X standard.  More info to come soon!!


INFORMATION COMMON TO BUILDING ANY gar DOA.

PLEASE ALWAYS REFURE TO THE APPROPRIATE ASSEMBLY MANUAL WHEN ASSEMBLING gar DOAs. 
Either print it out or have the pdf open on your desktop. This will help both the novice and ProTech alike
from accidentally making assembly errors.

Note that the OUTPUT transistors are NOT the same.  One is a NPN and the other
is a PNP.  Make sure that they are in the correct positions and facing the correct directionAs shown in
the assembly manual.

Note the BLUE Murata caps are all different values.  Make sure you got the correct
cap in the correct positions as shown in the assembly manual.

Note that the DIODES are polarized.  Make sure that the black band on the diode is in
The hole with the circle.  Note the diode pads on the PCB are square shaped. 
They are the ONLY square pads on the PCB.

All  BC560C transistors are on tape.  (Except for the Matched Pairs on the
gar918BC and garxxxx(OA10) kits.  These are in a little bag with the milmax pins.)
The pads on the PCB are in a straight line on ALL The BC560Cs and only these,
so that they
will not be confused with the BC550C pads.  Make sure they are facing the correct way as shown
on the silkscreen.

All  BC550Cs transistors are in little bags.  One of the bags is for the
MATCHED input pair (gar2520, gar1731 garAM10kits) and this bag will also include the Millmax pins. 
Do not remove the transistors from this bag until installing them so they do not get mixed up with
the other BC550C transistors in the kit.  All BC550C pads on the pcb are in a triangle formation
so as not to be confused with the straight line BC560C pads. Make sure they are facing
the correct way as shown on the silkscreen.

Measure all RESISTOR values at instillation and install according to the manual. 
Be careful when measuring values above 100k so you will not be including your skin
resistance in the measurement.

Before testing your fresh assembled DOA,  double check for unwanted solder bridges where shown
In the manual and make sure that no component leads on the component side of the PCB are
touching each other.

As these are all the most common assembly errors.  Following this basic informational
Guide should result in a successful build and your new DOA should work first time out of the box.

If you followed the Assembly Tips Page and Assembled your DOA by this
Manual all should be well and it should work the first time “out of the box”
But even the most experienced of us have an occasional screw up.

----------------------

Note on part substitutions in kits.  Occasionally the parts listed in the BOM
Of each kit maybe temporarily unavailable from my parts supplier.  A substitution
Part will be included in the kit.  These parts will be of the same value, tolerance
And quality of the part listed in the BOM. 

For you folks sourcing your own partsFor your builds,  All the ¼ watt resistors use
any major brand 1% metal film. The ½ watt resistors can be any major brand carbon film
or metal film 5% or better.
The Murata caps can be 50v or 100v 5%.  Any major brand npo/cog 5% with the lead
Spacing of .1” or 2.5mm can be used if necessary. 
Output transistors can be ON semi, Fairchild or ST micro transistors. 
Note that the ST micro transistors have a slightly different  Package but will drop right
in the PCB just fine.



HOLD ;)
 

jsteiger

Well-known member
White Market Member
Joined
Apr 11, 2008
Messages
3,329
Location
Nashville TN
Happy to announce I've got the new garOA10's listed at the store!

You can find them here:
https://capi-gear.com/catalog/index.php?cPath=71_72
 

TwentyTrees

Well-known member
Joined
Sep 17, 2015
Messages
345
Location
London, UK
Hi Gary & Jeff,

Quick question - what's the input impedance of the garOA10? I'm scoping a mic preamp project based around this op amp, and was wondering if I could get away with a 1:10 in there. I'm assuming it'll push 50dB into a 2503 without breaking sweat.  ;D

Thanks!
Andy
 

TwentyTrees

Well-known member
Joined
Sep 17, 2015
Messages
345
Location
London, UK
And, from the datasheet on Kubarth's website, I think I've answered my own questions (assuming the garOA10 is the same as the Neumann in these respects):
  • Differential input impedance = 40k...
  • So on a mic impedance of 200R, around a 4.5:1 step up on the input transformer seems about as much as I can ask for...
  • And given output impedance and current, 50dB into a 150:600 OPT should be very doable.

There's a few ill-informed assumptions going on here (eg that input Z is more a function of topology than the exact transistors used), so I'd be grateful for a steer if I'm wildly off base with any of this. Otherwise: test and learn!  ;)
 

PRR

Well-known member
Joined
Jan 30, 2010
Messages
11,144
Location
Maine USA
It's an op-amp. Under NFB the working input impedance is likely to be infinity.

The question is: what is the OSI? Optimum Source Impedance for low hiss. Or don't you care about hiss?
 

TwentyTrees

Well-known member
Joined
Sep 17, 2015
Messages
345
Location
London, UK
Excellent, thank you for pointing me in the right direction PRR. Have done a good deal of reading today.

I'm calculating the OSI for the OA10 as 877k, based on input voltage noise  of 0.5uV/√Hz and input current noise of 0.57pA/√Hz (as √(2IBq) with an input bias current of -1uA from datasheet, which I treated as 1uA to be able to resolve the sqrt).

Now off to calculate the noise figure of various candidate input transformers, using the excellent info here:
https://groupdiy.com/index.php?topic=17885.msg208417#msg208417

Much appreciated.
 

TwentyTrees

Well-known member
Joined
Sep 17, 2015
Messages
345
Location
London, UK
Thanks Gary, it does - grateful for your help.

gar381 said:
Twenty Trees..

The garOA10 works very well in a API312 pre driving the 75:75:75:75  2503 OPT
so a 150:600 OPT will work fine.

Hope this helps.

GARY
 

cassio2263

Member
Joined
Feb 4, 2017
Messages
8
gar381 said:
NOTE FOR FOLKS SOURCING THEIR OWN PARTS>>>>

There are a few part # errors in the BOM in the current manual.

R2 & R5 is 2.7K  the correct part # is
MOUSER 271-2.7k-RC ( NOT 271-2.7-RC)

R9 is still 3.3R  1/2 watt                                                               
MOUSER 293-3.3-RC
(NOT 291-3.3-RC)

CD1 & CD2  Part number should be
594-K104K15X7RF5TL2 (NOT 594-K104K15RX7RF5TL2)

There will be an updated fixed manual soon in the doc section at the CAPI store.
Look for REVISED added to the link.


Just another note here..
Mouser seems to be having trouble with stock
on R8  (293-10-RC) at the moment.  You can use
660-CF1/2C100J as a sub if necessary. 

---------------------------------------------------------------

The NEW garxxxx(OA10) DOA will work from +/- 15V  thru +/-24V so it is a
Happy camper on any VPR or 51X standard.  More info to come soon!!


INFORMATION COMMON TO BUILDING ANY gar DOA.

PLEASE ALWAYS REFURE TO THE APPROPRIATE ASSEMBLY MANUAL WHEN ASSEMBLING gar DOAs. 
Either print it out or have the pdf open on your desktop. This will help both the novice and ProTech alike
from accidentally making assembly errors.

Note that the OUTPUT transistors are NOT the same.  One is a NPN and the other
is a PNP.  Make sure that they are in the correct positions and facing the correct directionAs shown in
the assembly manual.

Note the BLUE Murata caps are all different values.  Make sure you got the correct
cap in the correct positions as shown in the assembly manual.

Note that the DIODES are polarized.  Make sure that the black band on the diode is in
The hole with the circle.  Note the diode pads on the PCB are square shaped. 
They are the ONLY square pads on the PCB.

All  BC560C transistors are on tape.  (Except for the Matched Pairs on the
gar918BC and garxxxx(OA10) kits.  These are in a little bag with the milmax pins.)
The pads on the PCB are in a straight line on ALL The BC560Cs and only these,
so that they
will not be confused with the BC550C pads.  Make sure they are facing the correct way as shown
on the silkscreen.

All  BC550Cs transistors are in little bags.  One of the bags is for the
MATCHED input pair (gar2520, gar1731 garAM10kits) and this bag will also include the Millmax pins. 
Do not remove the transistors from this bag until installing them so they do not get mixed up with
the other BC550C transistors in the kit.  All BC550C pads on the pcb are in a triangle formation
so as not to be confused with the straight line BC560C pads. Make sure they are facing
the correct way as shown on the silkscreen.

Measure all RESISTOR values at instillation and install according to the manual. 
Be careful when measuring values above 100k so you will not be including your skin
resistance in the measurement.

Before testing your fresh assembled DOA,  double check for unwanted solder bridges where shown
In the manual and make sure that no component leads on the component side of the PCB are
touching each other.

As these are all the most common assembly errors.  Following this basic informational
Guide should result in a successful build and your new DOA should work first time out of the box.

If you followed the Assembly Tips Page and Assembled your DOA by this
Manual all should be well and it should work the first time “out of the box”
But even the most experienced of us have an occasional screw up.

----------------------

Note on part substitutions in kits.  Occasionally the parts listed in the BOM
Of each kit maybe temporarily unavailable from my parts supplier.  A substitution
Part will be included in the kit.  These parts will be of the same value, tolerance
And quality of the part listed in the BOM. 

For you folks sourcing your own partsFor your builds,  All the ¼ watt resistors use
any major brand 1% metal film. The ½ watt resistors can be any major brand carbon film
or metal film 5% or better.
The Murata caps can be 50v or 100v 5%.  Any major brand npo/cog 5% with the lead
Spacing of .1” or 2.5mm can be used if necessary. 
Output transistors can be ON semi, Fairchild or ST micro transistors. 
Note that the ST micro transistors have a slightly different  Package but will drop right
in the PCB just fine.



Hi.
Is it possible to replace the BD137 / 138 (BD139 / 140) transistors with 2n4036 / 2n2102, on garAM10BC?
Greetings from Brazil.
 

abbey road d enfer

Well-known member
Moderator
Joined
Jan 22, 2008
Messages
12,363
Location
Marcelland
cassio2263 said:
Is it possible to replace the BD137 / 138 (BD139 / 140) transistors with 2n4036 / 2n2102, on garAM10BC?
Maybe; it depends on the actual idle current. In the absence of a schematic, it's hard to tall.
Please note you made a copious mistake in one of your previous posts:
"I'm calculating the OSI for the OA10 as 877k, based on input voltage noise  of 0.5uV/√Hz and input current noise of 0.57pA/√Hz"
The actual result is 877 ohms, a factor of 1000 less! This indicates a suitable xfmr would be a 1:2.
 

gar381

Well-known member
Joined
Jan 27, 2005
Messages
1,123
Location
Retired in (Amherst) Cleveland, Ohio
Is it possible to replace the BD137 / 138 (BD139 / 140) transistors with 2n4036 / 2n2102, on garAM10BC?

The simple answer is Yes.  BUT.... Tight fit & beware of pinout.  Don't let those 2n part cases (TO5/TO35) touch anything as the can is the collector.

BTW... those were the original AM10 outputs.

G.

 

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