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Joined 2002
Hello,
yes, if you want you can put a potentiometer instead of the pot+res series, set the bias (and the balance), measure the potentiometer resistance value and then swap the pot with a fixed resistor. More compact circuit and more long-term reliability!
As for a preamplifier, I do prefer the "classic" BLS! IMHO it's great!
Best,
Marcello
Hello, It's me again 🙂
I hope this is the last or pre_last version. I'm only thinking on those resistors before pots, I;m not sure It was realy good idea to cut them out 🙂
I'm not sure I can make this PCB with Laserprint method, it's too complex, but I'll try.
P.s. Tortello, do You remember in what range does pot R16 (100k) change BIAS? I's asking because You had 20k+100k resistance and I have only 100k now, so is it sufficient value to set 100-250ma BIAS.
I hope this is the last or pre_last version. I'm only thinking on those resistors before pots, I;m not sure It was realy good idea to cut them out 🙂
I'm not sure I can make this PCB with Laserprint method, it's too complex, but I'll try.
P.s. Tortello, do You remember in what range does pot R16 (100k) change BIAS? I's asking because You had 20k+100k resistance and I have only 100k now, so is it sufficient value to set 100-250ma BIAS.
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OMG, I just killed 4 hours of my life - closed project and didn't save that (last save was 3.5 hours before) 
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sorry to hear that StreamYour layout looks great and you should have no problems etching with the Gootee method, I've done messier transfers
OMG, I just killed 4 hours of my life - closed project and didn't save that (last save was 3.5 hours before)
Hey Stream, redo it now while it fresh in your head. It never takes vey long the second time round. Most of the time in PCB design is working out what to do.
BTW: Wasn't auto backup on? Control panel > Options > Backup
regards
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Greg Erskine
Whooh! My mistake was that I didn't start new project, I just Start new Board without Project, so Eagle for some reason doesn't save progress. But I found some files with *.b## extension, and after I rename this to *.brd it opened!
So here it is:
Brd:
http://rapidshare.com/files/313125268/ver7_finished.brd
Pdf:
http://rapidshare.com/files/313125486/ver7_finished.pdf
Whooh! My mistake was that I didn't start new project, I just Start new Board without Project, so Eagle for some reason doesn't save progress. But I found some files with *.b## extension, and after I rename this to *.brd it opened!
So here it is:
Brd:
http://rapidshare.com/files/313125268/ver7_finished.brd
Pdf:
http://rapidshare.com/files/313125486/ver7_finished.pdf
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Here is last version.
Changelog:
R8 removed
R17 1k => 2k
R4 came back. Because there are only 100k and 200k pots, and wee need about 120k.
A bit of cosmetic 🙂
Eagle brd File
PDF
Changelog:
R8 removed
R17 1k => 2k
R4 came back. Because there are only 100k and 200k pots, and wee need about 120k.
A bit of cosmetic 🙂
An externally hosted image should be here but it was not working when we last tested it.
Eagle brd File
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Hello. Today I was a bit confused about one little thing - where should I connect gnd from output jack?
I just thought, that using 3-pin 6.3 Jack lowering advanteges of dual-mono architecture... Anyone can confirm this?
I just thought, that using 3-pin 6.3 Jack lowering advanteges of dual-mono architecture... Anyone can confirm this?
HI Stream,
Excellent work!!
Just a quick question: in your latest layout I see a TO-92 device, named Q7 and labelled as "1815". Is that the BC550 transistor (Q3) shown at the schematic in post #11?
Regards,
Evangelos
Excellent work!!
Just a quick question: in your latest layout I see a TO-92 device, named Q7 and labelled as "1815". Is that the BC550 transistor (Q3) shown at the schematic in post #11?
Regards,
Evangelos
Hi kenev,
Thanks for kind word.
It is 2SC1815. You can use ZTX450 instead or BC550, but BC550 has another pinout (as I remember).
My build is going slowly. 9 Jan I ordered last parts, and today "laserprinted" amp's pcbs (but not etched yet).
Thanks for kind word.
It is 2SC1815. You can use ZTX450 instead or BC550, but BC550 has another pinout (as I remember).
My build is going slowly. 9 Jan I ordered last parts, and today "laserprinted" amp's pcbs (but not etched yet).
An externally hosted image should be here but it was not working when we last tested it.
Hi Stream,
Thank you for your reply.
I have downloaded the freeware version of Eagle and have been trying to find out how I can print the board (just the "copper" part), but couldn't come to a result. Is there any quick instructions you could help me with?
Regards,
Evangelos
Thank you for your reply.
I have downloaded the freeware version of Eagle and have been trying to find out how I can print the board (just the "copper" part), but couldn't come to a result. Is there any quick instructions you could help me with?
Regards,
Evangelos
kenev,
Goto:
View -> Display\Hide layers...
Check only:
Bottom, Pads, Vias, Holes.
Then just print this 🙂
BTW don't use my PS design - it's unfinished!
P.S. Can Anyone help me with ground wiring? Check this please:
Goto:
View -> Display\Hide layers...
Check only:
Bottom, Pads, Vias, Holes.
Then just print this 🙂
BTW don't use my PS design - it's unfinished!
P.S. Can Anyone help me with ground wiring? Check this please:
An externally hosted image should be here but it was not working when we last tested it.
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I know it is an old post, but I have a nice stock of lovoltech power jfets, can someone point me to this design?
Hum?
Hi there,
I am not trying to hijack the thread. I am posting here as this thread seems to be still active.
I have finished my Marcello's head amp today.
The only thing worries is the hum. With the original 4700uF-5.6Ohm-2200uF it is not really acceptable for any hifi listening (I am using Senn 595 - 50Ohm version).
I still have some longish cables running around, but I am pretty sure the hum comes from the PSU. I doubled the capacitors. The hum is almost acceptable, but it is not ideal. I am pretty sure I can get rid of teh hum if I increase the caps even more. Still I think I might have done something wrong as I cannot believe Marcello would be happy with the amount of hum in the original circuit.
Can anybody comment on this?
Greg
Hi there,
I am not trying to hijack the thread. I am posting here as this thread seems to be still active.
I have finished my Marcello's head amp today.
The only thing worries is the hum. With the original 4700uF-5.6Ohm-2200uF it is not really acceptable for any hifi listening (I am using Senn 595 - 50Ohm version).
I still have some longish cables running around, but I am pretty sure the hum comes from the PSU. I doubled the capacitors. The hum is almost acceptable, but it is not ideal. I am pretty sure I can get rid of teh hum if I increase the caps even more. Still I think I might have done something wrong as I cannot believe Marcello would be happy with the amount of hum in the original circuit.
Can anybody comment on this?
Greg
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