Salas hotrodded blue DCB1 build - Page 25 - diyAudio
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Old 7th September 2010, 07:10 PM   #241
Marra is offline Marra  United Kingdom
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Thanks Jean-Paul. I guess I was lucky with the leds buying 30 from Farnell with most of them giving 1.8v give or take 0.04-5v with a few above 1.9 and acouple below 1.7. I'm really looking forward to listening to this; then I'll have to decide on a case. Maybe Hifi 2000.
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Old 7th September 2010, 07:10 PM   #242
Salas is offline Salas  Greece
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Its because the blue has a differently connected positive leds local CCS. Orthodox connection. Goes OK tonally when hot rod as the blue is intended. The black boards have an inherent twist to present a certain tone when run ecologically as originally designed. That will make them slightly asymmetric on purpose. (+/-) 9.5 to 10.5V is my preferred sweet spot, so the mentioned build seems perfectly OK.
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Old 7th September 2010, 07:44 PM   #243
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Of course ! I have the old Mez version and not the hot rodded blue version, sorry. While I am building a new Mez this evening I was searching the forum for posts regarding the voltages when I ended up in this thread. The third Mez has larger differences than the others which I wanted to check.

I was not aware that there are differences in the schematic of the blue version though...
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Old 7th September 2010, 07:55 PM   #244
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Should a pot go before or after the DCB1? Opinions please...

I note that on the Mez it is before. It could be either way though, couldn't it? I'm sure the result will be different, but both should work...which is best?
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Old 7th September 2010, 08:00 PM   #245
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Before is the best way. Why would you make the output impedance higher by adding a potentiometer there ? And the circuit will be more noisy as it is always "open" at the input...
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Old 7th September 2010, 08:05 PM   #246
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OK, before then. Thanks.

On the subject of pre-amp earthing. What do you think to my suggestion to isolate signal earths through the pre-amp process, so that they only reach earth in the power amp? Is this a good procedure? It reduces the likelihood of earth loops, no? Is there any reason not to do this?
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Old 7th September 2010, 08:11 PM   #247
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Please only use the term "earth" only for PE/Safety Earth which is meant for safety in case of live AC wiring touching the chassis/case. There is no "signal earth". I know that the terms are very misleading as we speak about "ground loops" in english... I recently read a very good explanation regarding safety earth/PE and signal GND on this forum but I don't recall in what thread it was.

You mean signal ground or GND, don't you ? Or safety earth/PE ?
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Last edited by jean-paul; 7th September 2010 at 08:15 PM.
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Old 7th September 2010, 08:12 PM   #248
Salas is offline Salas  Greece
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Quote:
Originally Posted by jean-paul View Post
Of course ! I have the old Mez version and not the hot rodded blue version, sorry. While I am building a new Mez this evening I was searching the forum for posts regarding the voltages when I ended up in this thread. The third Mez has larger differences than the others which I wanted to check.

I was not aware that there are differences in the schematic of the blue version though...
I have posted that will be a difference there when there was talk about releasing it, it shows on its CCT too if you look 1st page here. Also for reg only I have put a note on the reg only thread not to manipulate that fet as for the black. Then again the threads were galloping, easy to skip info. Check your positive side jfet leds ccs (the one connected to the 10R) maybe its stronger than average, or some leds on that side are a bit happy.
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Old 7th September 2010, 09:12 PM   #249
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Quote:
Originally Posted by LucasAdamson View Post
On the subject of pre-amp earthing. What do you think to my suggestion to isolate signal earths through the pre-amp process, so that they only reach earth in the power amp? Is this a good procedure? It reduces the likelihood of earth loops, no? Is there any reason not to do this?
Sorry, yes I mean signal return. It does terminate at the earth, and so yes you're right it's important to be as clear as possible. I mean the return that runs with the signal lead through the RCAs and interconnects.

My question is whether it is really necessary to connect them to transformer earth/chassis earth within the preamp, as is performed on the DCB1 blue with jumper number 2?

Is there a good reason to connect the signal returns to earth, or is it better to leave them isolated from the chassis and electrical system until the power amp? My thinking is that a loop is created when signal returns are connected to earth on both pre and power amps.

Many thanks
Lucas
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Last edited by LucasAdamson; 7th September 2010 at 09:14 PM.
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Old 7th September 2010, 10:13 PM   #250
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