Dusty Circuit
Well-known member
Yes, I think I will. They seem to get a lot of good reviews. Are there any specs/measurements out there?
gar2520 build thread
- Thread starter gar381
- Start date
Help Support GroupDIY Audio Forum:
finish mine today,
great documentation it was clear and slick.
first one took me 2 hours to build, while watching at the same time the Triple Jump Final (World Championships in Athletics Berlin).
The second one took me 30 minutes.
Can't wait to try them as soon as I finish my acess 312.
Thanks to Gary and Jeff
great documentation it was clear and slick.
first one took me 2 hours to build, while watching at the same time the Triple Jump Final (World Championships in Athletics Berlin).
The second one took me 30 minutes.
Can't wait to try them as soon as I finish my acess 312.
Thanks to Gary and Jeff
Attachments
gar381
Well-known member
Looking Good Whoops !! 
GARY
GARY
Rob Flinn
Well-known member
How close should I match Q1 & Q2 ??
jsteiger said:
Jeff just to be sure about something,
I bought tge gar2520 Kits from your website,
the Q1 abd Q2 transistor that were inside the millmax pins bag where already matched by you?
Yes, those are the matched ones. Gary actually matches those before he sends the kits to me.Whoops said:
Best, Jeff
Rob Flinn
Well-known member
jsteiger said:
Sure, but that doesn't tell me how close to match them ? Within 5% or 10% etc ???
jsteiger said:
Thanks Jeff
Rob Flinn said:
You should match them as close as possible. if you buy around 20 transistors and measure them I'm sure you'll be able to achieve a >5% match.
10% seems to be too much tolerance in this case.
gar381
Well-known member
WHOOPS
The 2 transistors in the little bag with the millmax pins are already matched.
It's one several advantages of buying the complete kit over just the PCB.
When I match transistors I work with 100 of them at a time. I try to get them
within 2 or 3 HFE most are within 1. Example: if a transistor's HFE is 525 its match
will be between 523 and 527.
Matching is not super Critical at least in my experiments...
Plus or Minus 10 HFE should work fine.
Hope this helps WHOOPS.
GARY
The 2 transistors in the little bag with the millmax pins are already matched.
It's one several advantages of buying the complete kit over just the PCB.
When I match transistors I work with 100 of them at a time. I try to get them
within 2 or 3 HFE most are within 1. Example: if a transistor's HFE is 525 its match
will be between 523 and 527.
Matching is not super Critical at least in my experiments...
Plus or Minus 10 HFE should work fine.
Hope this helps WHOOPS.
GARY
mikefatom
Well-known member
You can achieve a 1% match if you're patient and have a lot of BC550C around.
Anything below 5% is fine though.
Anything below 5% is fine though.
gar381 said:WHOOPS
The 2 transistors in the little bag with the millmax pins are already matched.
It's one several advantages of buying the complete kit over just the PCB.
When I match transistors I work with 100 of them at a time. I try to get them
within 2 or 3 HFE most are within 1. Example: if a transistor's HFE is 525 its match
will be between 523 and 527.
Matching is not super Critical at least in my experiments...
Plus or Minus 10 HFE should work fine.
Hope this helps WHOOPS.
GARY
Thanks for explaining Gary.
Rob Flinn
Well-known member
Thanks for the responses guys, that answers the question.
ninetysixk
Member
Hi guys,
I am in the process of building some asccess 312 preamps and have purchased some 2520 opamp kits from the classic API store. I have a pretty limited understanding of electronics but I am a neat solerer. I have 2 questions and they are as follows.
1. Can someone instruct me or point me to information around how to test the opamp with a multimeter to make sure it is operational?
2. My main concern about this build is that i cant seem to seperate the tiny caps (2 of them) that lie right next to the millmax pins on o ne side. To the naked eye it looks awefully close. I am pretty sure that these 2 caps have all ended up touching or looking like it may be bridged somehow with the millmax pins. Everything else is nicely soldered but I found it almost impossible to seperate the above mentioned.
I tried to follow the trace to see if they are connected anyway. Thes space is so small I can't tell. I havn't build the preamps in full so I cant just put them in and test and I'm not sure that would be such a good idea :-0
Can some kind soul please let me know if these will or will not work. I dont have a macro camera so I cant take any close up pictures. Sorry
Nick
I am in the process of building some asccess 312 preamps and have purchased some 2520 opamp kits from the classic API store. I have a pretty limited understanding of electronics but I am a neat solerer. I have 2 questions and they are as follows.
1. Can someone instruct me or point me to information around how to test the opamp with a multimeter to make sure it is operational?
2. My main concern about this build is that i cant seem to seperate the tiny caps (2 of them) that lie right next to the millmax pins on o ne side. To the naked eye it looks awefully close. I am pretty sure that these 2 caps have all ended up touching or looking like it may be bridged somehow with the millmax pins. Everything else is nicely soldered but I found it almost impossible to seperate the above mentioned.
I tried to follow the trace to see if they are connected anyway. Thes space is so small I can't tell. I havn't build the preamps in full so I cant just put them in and test and I'm not sure that would be such a good idea :-0
Can some kind soul please let me know if these will or will not work. I dont have a macro camera so I cant take any close up pictures. Sorry
Nick
imo
Well-known member
Nick,
If they are what i am thinking of, they are .1 caps going from the power rails to ground, so you should be getting continuity between one side of the cap and ground, and then the other side and the power rails.
Gary, it would be cool to get a schematic. I had a couple of similar moments where i wasn't sure it i had a solder bridge, and it is nice to check it against the work as you go.
By the way, finished with one, sounds great in my 312 style pre!
Ian
If they are what i am thinking of, they are .1 caps going from the power rails to ground, so you should be getting continuity between one side of the cap and ground, and then the other side and the power rails.
Gary, it would be cool to get a schematic. I had a couple of similar moments where i wasn't sure it i had a solder bridge, and it is nice to check it against the work as you go.
By the way, finished with one, sounds great in my 312 style pre!
Ian
gar381
Well-known member
Nick
If you are referring to CD1 and CD2 .. Imo is right. Electrically CD1 connects between The V+ and Gnd Millmax pins. CD2 connects between the Gnd and V- Millmax pins so any solder bridge between the cap leads and their respective Millmax pins is OK.
The board pictures on page 13 of the assembly manual are very helpful.
Suggestions:
Use a very small tip iron.
Use Kester 63/37 solder.
USE A MAGNIFYING LAMP TO CHECK YOUR WORK !!
A good way to check these guys is with a signal generator, a scope and a Variac.
GARY
If you are referring to CD1 and CD2 .. Imo is right. Electrically CD1 connects between The V+ and Gnd Millmax pins. CD2 connects between the Gnd and V- Millmax pins so any solder bridge between the cap leads and their respective Millmax pins is OK.
The board pictures on page 13 of the assembly manual are very helpful.
Suggestions:
Use a very small tip iron.
Use Kester 63/37 solder.
USE A MAGNIFYING LAMP TO CHECK YOUR WORK !!
A good way to check these guys is with a signal generator, a scope and a Variac.
GARY
TornadoTed
Well-known member
I just finished building 8 and they all work first time, took me about 6-7 hours in total. I haven't given them a good workout in the preamps yet as I've been busy with other things but I'm looking forward to hearing them at a session I have coming up.
I don't think I will ever tackle anything smaller as it stretched my slightly dodgy eye sight to the limit!
I don't think I will ever tackle anything smaller as it stretched my slightly dodgy eye sight to the limit!
gar381 said:
Hi Gary there's any other way of check this opamps, or do some measurements or tests if you don't have a scope and a Variac?
I have a Signal probe connected to an Amp and have am DMM,
what could I do?
I have 3 Gar opamps, 2 work perfectly in the preamp, the third one makes the mic pre go silent.
can't figure out whats the problem.
thanks
gar381
Well-known member
Hi Whoops
Is the one that doesn't work on of the ones from post...?
http://www.groupdiy.com/index.php?topic=33501.msg451537#msg451537
I see that the bottom of the input and output millmax pins arn't soldered. Solder both
top and bottom of the millmax pins. Hard to tell in your pictures but it looks
like maybe the output transistors could use a bit more solder on the pins.
Also Look for any solder bridges top and bottom (A-B it to a working one)
The Use a magnified lamp will be most usefull here.
Look for any part leads touching each other on the top side.
Hope this helps. Best of luck
GARY
Is the one that doesn't work on of the ones from post...?
http://www.groupdiy.com/index.php?topic=33501.msg451537#msg451537
I see that the bottom of the input and output millmax pins arn't soldered. Solder both
top and bottom of the millmax pins. Hard to tell in your pictures but it looks
like maybe the output transistors could use a bit more solder on the pins.
Also Look for any solder bridges top and bottom (A-B it to a working one)
The Use a magnified lamp will be most usefull here.
Look for any part leads touching each other on the top side.
Hope this helps. Best of luck
GARY
Hi Gary thanks a lot for your tips,
I will proceed as you suggested.
Unfortunately the Opamp that is not working is not any of those in the pictures in the other thread, those 2 are working perfectly.
BD140 and the 5r6 (R11) resistor burned in this opamp, I replaced them but there's no sound coming out of it.
Today I replaced the Diodes (D1a-b) also, as they were really close to BD140 and could be damaged also,
I will check tomorrow.
Does r11 needs to be 0,5w?
I only had a 0,25watts, should it be enough for the tests?
thanks
I will proceed as you suggested.
Unfortunately the Opamp that is not working is not any of those in the pictures in the other thread, those 2 are working perfectly.
BD140 and the 5r6 (R11) resistor burned in this opamp, I replaced them but there's no sound coming out of it.
Today I replaced the Diodes (D1a-b) also, as they were really close to BD140 and could be damaged also,
I will check tomorrow.
Does r11 needs to be 0,5w?
I only had a 0,25watts, should it be enough for the tests?
thanks
