You can use bypass capacitors under the board
This will make your life easier, not needing to replace boards.
This is an old practice, was abandoned because purists are seeing ghoasts everywhere..if not seeing them they believe they exist.
Here is a brazilian circuit.
regards,
Carlos
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Hello Lumba...how's your mood today?
This will make your life easier, not needing to replace boards.
This is an old practice, was abandoned because purists are seeing ghoasts everywhere..if not seeing them they believe they exist.
Here is a brazilian circuit.
regards,
Carlos
........................................
Hello Lumba...how's your mood today?
An externally hosted image should be here but it was not working when we last tested it.
Trimpots are for adjustment purpose...not really needed to keep them into the circuit
The get filled with rust...bad contact may happens and they stand there without any function.
We need them only when adjusting..they are always something we can substitute by a fixed resistance (same value or almost the same) or a series of resistances to match the adjusting value or even parallel resistances if needed.
After adjust...remove your trimpot and measure the resistance..them substitute by a fixed resistance.
That trimpot can be used once again..hundred of times, not needing to be there doing less than it can do into the board.
regards,
Carlos
The get filled with rust...bad contact may happens and they stand there without any function.
We need them only when adjusting..they are always something we can substitute by a fixed resistance (same value or almost the same) or a series of resistances to match the adjusting value or even parallel resistances if needed.
After adjust...remove your trimpot and measure the resistance..them substitute by a fixed resistance.
That trimpot can be used once again..hundred of times, not needing to be there doing less than it can do into the board.
regards,
Carlos
An externally hosted image should be here but it was not working when we last tested it.
There's no problems to use capacitors under the board
If some Radio Frequency, very high frequency radio transmitters can use them..... so... we can use them to less critical aplications alike audio frequencies.
Good for 400 Megahertz may be good to 20 Kilohertz.
regards,
Carlos
If some Radio Frequency, very high frequency radio transmitters can use them..... so... we can use them to less critical aplications alike audio frequencies.
Good for 400 Megahertz may be good to 20 Kilohertz.
regards,
Carlos
An externally hosted image should be here but it was not working when we last tested it.
When you have doubts about some capacitor voltage limits.
to be absolutelly sure only testing it with the voltage you will gonna use it.
This can be a destructive test (i am a destroyer...i use to destroy things... this way i have learned some)
Place your capacitor into the 36 volts and let it there to see if it will explode or overheat.
not happening that.... make a fast check if AC is crossing it.
Doing that install into your circuit and be happy man!
regards,
Carlos
to be absolutelly sure only testing it with the voltage you will gonna use it.
This can be a destructive test (i am a destroyer...i use to destroy things... this way i have learned some)
Place your capacitor into the 36 volts and let it there to see if it will explode or overheat.
not happening that.... make a fast check if AC is crossing it.
Doing that install into your circuit and be happy man!
regards,
Carlos
An externally hosted image should be here but it was not working when we last tested it.
the latest schematics show R16 shorted with links.
What is R16's purpose?
Why is the VAS a medium power device?
What is R16's purpose?
Why is the VAS a medium power device?
You're welcome lumba..even into the criticising mood
no problems about that... criticising but always with me dear Lumba... there's a lot of room to criticise into this circuit... a hell old thing..sounding interestingly nice...and incredible!... measuring good too?
regards,
Carlos
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Andrew T
No special reason to use BD139 as VAS there...another transistor can be used..current is small there.
I have just used the ones i have (the good ones i have received from Sean.... Anonimous in our forum)
I have to suggest some...and to test my circuit with some transistor... i do not think this is the best into the position.
Even input and drivers can be replace...well... everything is replaceable in this life..including ourselves.
If you have a suggestion about a better choice will be very welcome.
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You have very good eyes Andrew...thank you.... was a mistake.
regards,
Carlos
regards,
Carlos
no problems about that... criticising but always with me dear Lumba... there's a lot of room to criticise into this circuit... a hell old thing..sounding interestingly nice...and incredible!... measuring good too?
regards,
Carlos
........................................................................................
Andrew T
No special reason to use BD139 as VAS there...another transistor can be used..current is small there.
I have just used the ones i have (the good ones i have received from Sean.... Anonimous in our forum)
I have to suggest some...and to test my circuit with some transistor... i do not think this is the best into the position.
Even input and drivers can be replace...well... everything is replaceable in this life..including ourselves.
If you have a suggestion about a better choice will be very welcome.
........................................................................................................
You have very good eyes Andrew...thank you.... was a mistake.
regards,
Carlos
regards,
Carlos
Attachments
you've cut the wrong link.
the horizontal link between C24 & Q2 makes the schematic the same as original.
I would use a fast, low capacitance, high hFE, signal device for the VAS, even if this means increasing the value of the Miller comp cap.
the horizontal link between C24 & Q2 makes the schematic the same as original.
I would use a fast, low capacitance, high hFE, signal device for the VAS, even if this means increasing the value of the Miller comp cap.
Andrew is the QC department. Thanks Andrew.
I'll fix the whole schematic and re-post it a bit later.
..Todd
I'll fix the whole schematic and re-post it a bit later.
..Todd
Build the Trust amplifier..the one that has a real working
Quality control department.
heheheh.
regards,
Quality control department.
heheheh.
regards,
An externally hosted image should be here but it was not working when we last tested it.
AndrewT said:
BD139
ft ~50MHz
Cbe ~10pF
hFe ~100
+ easly available & cheap!
IMHO it's a perfect choice here.
Charlie!
Are you sure these 7.5pF and 680pF caps are needed? What's the reason using them?
Nice circuit anyway! Thanks for publishing!
Reminds me to the old HiFi/PA amps in the 70's. They used the same conventional circuit, but with old OP devices (quasi 2N3055).
Capacitors prevents High Frequency oscilations.
those frequencies goes from 3 to 30 megahertz..and i found this amplifier addicted to those oscilations... i had while tweaking..reason why they are there....not only those capacitors helps, also zobel filter and the VAS miller capacitor.
I think they could be even bigger.... i tested till i have blocked those oscilations...not sure..maybe the Miller increase have stopped the oscilations and those folks are doing nothing....if doing nothing, at least not bothering me..if bothers you... do not use them dear friend.
If you want you can remove them... having oscilations, them insert them back again.
I love BD139...but you know..each one has own preferences.
This is a matter of taste...i like blonds.
regards,
Carlos
.........................................................................................................
The amplifier resulted good into measurements with those folks there..in place.
those frequencies goes from 3 to 30 megahertz..and i found this amplifier addicted to those oscilations... i had while tweaking..reason why they are there....not only those capacitors helps, also zobel filter and the VAS miller capacitor.
I think they could be even bigger.... i tested till i have blocked those oscilations...not sure..maybe the Miller increase have stopped the oscilations and those folks are doing nothing....if doing nothing, at least not bothering me..if bothers you... do not use them dear friend.
If you want you can remove them... having oscilations, them insert them back again.
I love BD139...but you know..each one has own preferences.
This is a matter of taste...i like blonds.
regards,
Carlos
.........................................................................................................
The amplifier resulted good into measurements with those folks there..in place.
Hi Carlos,
Too many amps already. And building Roender's very sophisticated amp now. If I build anymore SS amps, it will probably be this one. Very simple, non-approved for audiophile use, no fancy parts. And I won't even bother close matching transistors (just best match from whatever is in the bin). Back to basics.
Sheldon
Too many amps already. And building Roender's very sophisticated amp now. If I build anymore SS amps, it will probably be this one. Very simple, non-approved for audiophile use, no fancy parts. And I won't even bother close matching transistors (just best match from whatever is in the bin). Back to basics.
Sheldon
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