How do I
get into the group buy? Too late? http://www.diyaudio.com/forums/images/icons/icon9.gif
Unhappy
Have been reading this thread for
a week or more and have looked
in 'Group Buys' under 'Market Place'.
Will there be another GB offered?
get into the group buy? Too late? http://www.diyaudio.com/forums/images/icons/icon9.gif
Unhappy
Have been reading this thread for
a week or more and have looked
in 'Group Buys' under 'Market Place'.
Will there be another GB offered?
Well, I just modded my RevA to a full RevC (previously had just added cap and resistors to LM318 for stability). I thought I'd share a couple pictures for anyone who needs to do it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Rev. A to Rev. C Mods
Brian,
Do you have a marked up schematic showing what additions you made to Rev. A? Not sure if this has been asked before.
I'm getting closer to getting my Rev. A finished. Still awaiting some torriods from Plitorn.
Anyone use more than 10KuF for the bulk capacitors? I found some 15K ones I'm thinking of using.
Tom
Brian,
Do you have a marked up schematic showing what additions you made to Rev. A? Not sure if this has been asked before.
I'm getting closer to getting my Rev. A finished. Still awaiting some torriods from Plitorn.
Anyone use more than 10KuF for the bulk capacitors? I found some 15K ones I'm thinking of using.
Tom
Re: Rev. A to Rev. C Mods
Hmm, really the schematic is from REV C. He simply did some P2P on the board to implement REV C.
I have been meaning to document the conversion at some point. It is not really too hard, you just need both schematics in front of you.
REVA
REVB
REVC
I have used 12Kuf nichicons with good results.
Cheers!
Russ
tommytube said:
Hmm, really the schematic is from REV C. He simply did some P2P on the board to implement REV C.
I have been meaning to document the conversion at some point. It is not really too hard, you just need both schematics in front of you.
REVA
REVB
REVC
I have used 12Kuf nichicons with good results.
Cheers!
Russ
Thanks for the pics
I am trying to figure out if I want to wait for the mono boards or build a stereo version of the C. Piergiorgio sent a mask that shows the placement for this. The pics are a little clearer.
I need to look at this closely. The addition of a connection to pin 8 of the LM318 had me worried. Also changing the 100 pf cap to a 22pf and connecting to the other input.
How do the two compare sonically? I have a couple tweaks for my A yet to do. The cap in the feedback loop and the 12K resistor. I think there is still a little more in mine.
Has anyone preferred the A to the C version of My Reference?
George
BrianDonegan said:
I am trying to figure out if I want to wait for the mono boards or build a stereo version of the C. Piergiorgio sent a mask that shows the placement for this. The pics are a little clearer.
I need to look at this closely. The addition of a connection to pin 8 of the LM318 had me worried. Also changing the 100 pf cap to a 22pf and connecting to the other input.
How do the two compare sonically? I have a couple tweaks for my A yet to do. The cap in the feedback loop and the 12K resistor. I think there is still a little more in mine.
Has anyone preferred the A to the C version of My Reference?
George
Re: Thanks for the pics
Hi George, I really like them both. REV A is stellar, the one big thing REV C has is better phase linearity, but it is a compromise. The REV C circuit has limited bandwidth, and a different technique for managing the feedback which is not quite as stable as REV A. But stability has never been an issue for anyone I have talked to with either circuit.
Both circuits are compromises.
One good thing about the monoblocs I have produced in that you can utilize them for REV A,B and C, and there are some other subtle improvements.
The ability to drive each channel with its own trafo, or with a shared trafo is a big win for the monobloc approach. Also you can use two heatsinks instead of one. The bypassing on the monoblocs is a little more robust (though it was never anything but good).
So here is what I would do if I were you.
Build the REV As. Try them I think you will love them.
Then.. build the REV C monoblocs which should fit in the same case with the same HS, and try them. I think you will find they are both different, but quite enjoyable in there own rights.
Cheers!
Russ
Panelhead said:
Hi George, I really like them both. REV A is stellar, the one big thing REV C has is better phase linearity, but it is a compromise. The REV C circuit has limited bandwidth, and a different technique for managing the feedback which is not quite as stable as REV A. But stability has never been an issue for anyone I have talked to with either circuit.
Both circuits are compromises.
One good thing about the monoblocs I have produced in that you can utilize them for REV A,B and C, and there are some other subtle improvements.
The ability to drive each channel with its own trafo, or with a shared trafo is a big win for the monobloc approach. Also you can use two heatsinks instead of one. The bypassing on the monoblocs is a little more robust (though it was never anything but good).
So here is what I would do if I were you.
Build the REV As. Try them I think you will love them.
Then.. build the REV C monoblocs which should fit in the same case with the same HS, and try them. I think you will find they are both different, but quite enjoyable in there own rights.
Cheers!
Russ
hi all,
RevA= optimizes amp ( read my technical relationship and this thread ).
RevC= the most linear amplifier that me has built never.
The changes not are able appraise from the add. components, but from the technical analysis that there is after.
The revC THD is low of 0,002% in all the audio band and to all the powers on 8 ohms, and I have to change the generator to measure it with precision. The variation of THD among 4 and 8 ohms and the THD change vs. amplitude it's nearly nonexistent, the DF is flat (300) in all the audio band...
The stability is similar (RevA-RevC) and adeguate (no "pure caps" load but all "real load" capability)
Brian,
in your Photo not the 22pF cap is seen among R7 and pin6 LM318.
the 150pF on R7(R30) it may on component side, and without R42(R41) 270 ohm (more stability).
Ciao
Mauro
RevA= optimizes amp ( read my technical relationship and this thread ).
RevC= the most linear amplifier that me has built never.
The changes not are able appraise from the add. components, but from the technical analysis that there is after.
The revC THD is low of 0,002% in all the audio band and to all the powers on 8 ohms, and I have to change the generator to measure it with precision. The variation of THD among 4 and 8 ohms and the THD change vs. amplitude it's nearly nonexistent, the DF is flat (300) in all the audio band...
The stability is similar (RevA-RevC) and adeguate (no "pure caps" load but all "real load" capability)
Brian,
in your Photo not the 22pF cap is seen among R7 and pin6 LM318.
the 150pF on R7(R30) it may on component side, and without R42(R41) 270 ohm (more stability).
Ciao
Mauro
Through the magic of x-ray technology, a little more clarity :
Hi Mauro-
The 22pF cap has replaced the original 100pF (C10, C25) on the top of the board (standard mounting).
You are suggesting I remove R41, R42 (270R) for added stability? That can be done. It would certainly make the mod cleaner. My RevC monoblocks have R41 in place without any apparent issues, but I can try removing it there as well.
Thanks!
An externally hosted image should be here but it was not working when we last tested it.
Hi Mauro-
The 22pF cap has replaced the original 100pF (C10, C25) on the top of the board (standard mounting).
You are suggesting I remove R41, R42 (270R) for added stability? That can be done. It would certainly make the mod cleaner. My RevC monoblocks have R41 in place without any apparent issues, but I can try removing it there as well.
Thanks!
22 pf cap
The 22 pf connects now to the other input of the LM318. It was from output to the inverting input, in the C it goes to the noninverting input The A is pin 6 to pin 2. The C is pin 6 to pin 3.
Either way it looks real clean the way you modded this one. I have another stereo board to use as a C platform. Think I will go ahead and build it to compare to my A.
Thnks for taking the time to show your handiwork. The path lengths are much shorter than what I had envisioned. Mine would have looked hillbilly rigged without seeing PLovati's and your layouts.
George
The 22 pf connects now to the other input of the LM318. It was from output to the inverting input, in the C it goes to the noninverting input The A is pin 6 to pin 2. The C is pin 6 to pin 3.
Either way it looks real clean the way you modded this one. I have another stereo board to use as a C platform. Think I will go ahead and build it to compare to my A.
Thnks for taking the time to show your handiwork. The path lengths are much shorter than what I had envisioned. Mine would have looked hillbilly rigged without seeing PLovati's and your layouts.
George
So, like this?
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
. ok, I'll move it. 
It is between 2 and 6. When I did my mod with the board upside down, I counted from the wrong pin, so ended up at pins 3 and 7. My bad.
Fixed, and removed 270R.
Sorry for the bad pic. Time to clean the flux off the board.
Fixed, and removed 270R.
An externally hosted image should be here but it was not working when we last tested it.
Sorry for the bad pic. Time to clean the flux off the board.
