khstudio
Well-known member
I'd like to know too :green:
ours sound like the 2*5*2*0?
- Thread starter Mbira
- Start date
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therecordingart
Well-known member
The only things I'm confused about with the 2520BC is....
What is the deal with R4/R5?
How do you match transistors?
I also just want to confirm that R10 + C2 are wired in series correct?
What is the deal with R4/R5?
How do you match transistors?
I also just want to confirm that R10 + C2 are wired in series correct?
therecordingart
Well-known member
The closest value I could find to the 800R resistor was 806R. I know it should be fine considering the true value of a resistor does vary, but I just want to make sure.
therecordingart
Well-known member
Thank you much...
So R4/R5 is two 20k resistors in series or just one 20k resistor?
The revised schem appears to just have one 20k.
So R4/R5 is two 20k resistors in series or just one 20k resistor?
The revised schem appears to just have one 20k.
Phazinhead
Well-known member
Hi everybody
Anybody have a 2520 DOA schematic using transitor array such as THAT 300 series for example ? This would give a bigger PCB that original 2520 but would be maybe easier to build and no transistor matching to do. If you have any info about it :razz:
Anybody have a 2520 DOA schematic using transitor array such as THAT 300 series for example ? This would give a bigger PCB that original 2520 but would be maybe easier to build and no transistor matching to do. If you have any info about it :razz:
Walrus
Well-known member
[quote author="Phazinhead"]Hi everybody
Anybody have a 2520 DOA schematic using transitor array such as THAT 300 series for example ? This would give a bigger PCB that original 2520 but would be maybe easier to build and no transistor matching to do. If you have any info about it :razz:[/quote]
The HFE of the THAT 300 is too low, seems to be 100 typical, whereas the 2520 calls for greater than 400.
Anybody have a 2520 DOA schematic using transitor array such as THAT 300 series for example ? This would give a bigger PCB that original 2520 but would be maybe easier to build and no transistor matching to do. If you have any info about it :razz:[/quote]
The HFE of the THAT 300 is too low, seems to be 100 typical, whereas the 2520 calls for greater than 400.
I saw the THAT array...Thought the same thing...Couldn't we use that for a DOA?! Then I saw the specs and realized there was no way.
Honestly though...A DOA made from predominately a single chunk of silicon....That's almost like a...Opamp IC. What's the advantage? And just why does a DOA sound "better" than a regular chip opamp.
Is it the current drive capability? Joe took a stab at that with the "Hybrid" opamp by put a discreet power section on the tail of a chip OA.
Whatever the case...My 312 type pres with 2520's kill. Not exactly sure how much of that is iron and how much is the opamp. I guess I could try sticking some iron on the output of another pre and see how it does.
Honestly though...A DOA made from predominately a single chunk of silicon....That's almost like a...Opamp IC. What's the advantage? And just why does a DOA sound "better" than a regular chip opamp.
Is it the current drive capability? Joe took a stab at that with the "Hybrid" opamp by put a discreet power section on the tail of a chip OA.
Whatever the case...My 312 type pres with 2520's kill. Not exactly sure how much of that is iron and how much is the opamp. I guess I could try sticking some iron on the output of another pre and see how it does.
therecordingart
Well-known member
[quote author="flintan"]I made a new BOM from the remade schematic Mick found working for his 2520BC, if anyone is interested:
I'm gonna try this, hope it works. I will let you know when i do.[/quote]
Two questions:
-Where do CD1 and CD2 go? I'm not seeing a spot on the PCB or on the updated schematic.
-For D1a and D1b I messed up and only put in one diode. Will I be ok?
I'm gonna try this, hope it works. I will let you know when i do.[/quote]
Two questions:
-Where do CD1 and CD2 go? I'm not seeing a spot on the PCB or on the updated schematic.
-For D1a and D1b I messed up and only put in one diode. Will I be ok?
Tubemooley
Well-known member
I'll try to answer TheJames' question. I am not familiar with the THAT 300 array. Not yet anyways. But the beauty of a transistor array is that it is two (or more) transistors fabricated at the same time on one piece of silicon. So the geometries of the gate/base and junctions are very, very close to being the same. Then some of the foundries do laser-trimming to match them even closer. It would take us DIYer's hours to attain this level of matching on loose transistors. And a transistor array is just two (or more) transistors on one piece of silicon. An IC opamp usually contains 30 or more transistors on that one piece of silicon. Try to go read as many datasheets for IC opamps as you can. Some of the manufacturers include a simplified schematic for each device in the datasheet. That is only a simplified schematic. There are more components in there which they don't want to reveal. A monolithic IC opamp has all these components in order to attain certain spec's which the designers want that device to have. But the IC guys are rarely trying to attain really, really good sound. They're usually trying to optimize input current noise or something like that. The DIY DOA's which we build don't have 30 or more transistors. And they don't have all sorts of resistor-capacitor networks to filter out various things. They are some of the barest opamp circuits available so they pass nearly all the signal sent to them and don't muck with it and filter the shit out of it. The DIY DOA's are just short wires with amplification. And most all of them are running in class A and really suck down the power and consequently they need to dissipate all that power also. An IC opamp could never dissipate all this power in a DIP-8 package (for instance).
Alright. That's my 2 cents for today. DW.
Alright. That's my 2 cents for today. DW.
peter purpose
Well-known member
Nielsk,
There are too many differences between the two types, but try moving C5 to between Q1 collector and the output pin.
Try that and report back.
peter
There are too many differences between the two types, but try moving C5 to between Q1 collector and the output pin.
Try that and report back.
peter
nielsk
Well-known member
I will try that & report back
thanks
thanks
gemini86
Well-known member
bump... how did the thing sound? I'm also trying to figure out where the com or ground pin is attached to the circuit, since the schematic doesn't show where this pin should be going to?
thanks!
thanks!
Just put a 100n capacitor from the ground pin to each rail (+ and -).
That's all there is to it. :wink:
Regards,
Anders
That's all there is to it. :wink:
Regards,
Anders
nielsk
Well-known member
The ground on the original goes to a sheild covering the back.
The C5 to -in is the lowest osscilation I have found, but it never goes away.
The C5 to -in is the lowest osscilation I have found, but it never goes away.
