Good morning Russ;
Just a few questions: With the pcb and kit; are the power supply caps included and the diode rectifiers? Also what would you recommend for a transformer? I have an old working center tapped trans. pulled from a 70's Kenwood amp.
I have a lm3875 and lm4780 amp.In a few words;what do you feel are the major sonic improvements with the new amp.The lm4780 is my favourite now.
Thanks;
doggy
Just a few questions: With the pcb and kit; are the power supply caps included and the diode rectifiers? Also what would you recommend for a transformer? I have an old working center tapped trans. pulled from a 70's Kenwood amp.
I have a lm3875 and lm4780 amp.In a few words;what do you feel are the major sonic improvements with the new amp.The lm4780 is my favourite now.
Thanks;
doggy
Hi Doggy,
The LM3886 can drive more current than the LM3875, but they actually sound very similar. The 4780 is nothing more than two LM3886 dice in one package. So if you like the LM4780 you are really saying you also like the LM3886.
For our kits all of the PS parts which go on the PCB are included (caps, bridge, etc...) but you will need your own trafo.
48VCT is ideal (250-300VA is big enough for stereo), or 24V dual secondaries. It is OK to go a little lower voltage say 21-22V secondaries, but you will have less headroom.
The major benefit to REV_C is that it has some of the flatest frequency/phase shift behaviours you will ever see. That translates to good imaging, and faithful accoustics with faithful reproduction without the detriment of nasty phase shifts which are common in many amps.
Cheers!
Russ
The LM3886 can drive more current than the LM3875, but they actually sound very similar. The 4780 is nothing more than two LM3886 dice in one package. So if you like the LM4780 you are really saying you also like the LM3886.
For our kits all of the PS parts which go on the PCB are included (caps, bridge, etc...) but you will need your own trafo.
48VCT is ideal (250-300VA is big enough for stereo), or 24V dual secondaries. It is OK to go a little lower voltage say 21-22V secondaries, but you will have less headroom.
The major benefit to REV_C is that it has some of the flatest frequency/phase shift behaviours you will ever see. That translates to good imaging, and faithful accoustics with faithful reproduction without the detriment of nasty phase shifts which are common in many amps.
Cheers!
Russ
Russ/Mauro-
The GC amps usually benefit from a buffer driving them.
I am currently planning on going passive 50K noble pot and relay input switching but I have a pair of Pavels "audio refiner" brds if the buffer is necessary.
Should I plan to implement Pavels boards or will the 50K pot be sufficient?
The GC amps usually benefit from a buffer driving them.
I am currently planning on going passive 50K noble pot and relay input switching but I have a pair of Pavels "audio refiner" brds if the buffer is necessary.
Should I plan to implement Pavels boards or will the 50K pot be sufficient?
rabstg said:
Hi troy, a buffer will not hurt, but it is not necessary (the only exception would be if you had a source with very very high output impedance), because on this power amp the input impedance is high (100K). So your source does not have to pump much current.
50K pot is just fine, but I actually use a 10K pot when I am not using a preamp.
I have a few inverting GCs which absolutely require a buffer for good operation, in that case Pavels boards are a very solid choice, but this amp (MyRef) is not like that.
Cheers!
Russ
Member
Joined 2003
Member
Joined 2003
I know I'm a lot slow on the ball here but I finally have mauro's 2 channel amp up and running. So far I've only tested one channel and DC offset is 10mV, and there is no hum or anything. I screwed up a little when mounting the chips to the heatsink though. I didn't think ahead when I was lining up the holes and drilled one of the holes too close to an exising hole (previously used heatsink). So there is a part on the lower right of one of the LM3886 chips that is not in contact with the heatsink because it sits over a hole. Hopefully there will be no problems...
I only have it hooked to a cheap car speaker on my table right now to test with so I can't comment on sound quality. On the input is Russ White's Freebird preamp and an alps blue velvet 10K pot. I just thought I'd post to say that so far everything is going smoothly. I am very exited.
I only have it hooked to a cheap car speaker on my table right now to test with so I can't comment on sound quality. On the input is Russ White's Freebird preamp and an alps blue velvet 10K pot. I just thought I'd post to say that so far everything is going smoothly. I am very exited.
DcibeL said:
Hey thats great news!
As far as the heatink goes, it will probably be just fine, but here is something I did a few months ago when I had a similar issue. I took a propane torch and heated the heatsink at the hole and then used some thick silver solder I had lying around to fill the hole. Then you lapp the surface of the HS with a belt sander, or by hand. That worked fine for me.
Cheers!
Russ
Member
Joined 2003