Hi,
I just completed two monoblock amplifiers using the Audiosector premium kit and I am doing the preliminary tests before connecting them to a speaker. I just tested the rectifier boards. I have two transfomers 300VA 25VAC with dual secondaries.
One monoblock seems OK, but the other one has a strange behavior (for me at least, a genuine newbie). Indeed using my DMM I measure 22 DCV at both V- PG- and
V+ PG+ which seems correct, but, by mistake, I verified that simultaneously they also measure 47ACV again between V-PG-, V+PG+ (?)
I checked and checked again, always the same result. The other monoblock measures 0 ACV at both V- PG- and V+PG+.
Any idea on my mistakes?
Renato
I just completed two monoblock amplifiers using the Audiosector premium kit and I am doing the preliminary tests before connecting them to a speaker. I just tested the rectifier boards. I have two transfomers 300VA 25VAC with dual secondaries.
One monoblock seems OK, but the other one has a strange behavior (for me at least, a genuine newbie). Indeed using my DMM I measure 22 DCV at both V- PG- and
V+ PG+ which seems correct, but, by mistake, I verified that simultaneously they also measure 47ACV again between V-PG-, V+PG+ (?)
I checked and checked again, always the same result. The other monoblock measures 0 ACV at both V- PG- and V+PG+.
Any idea on my mistakes?
Renato
mattcalf said:Gah, I'm stuck between which option to get.
Premium vs. Classic.
I don't know if I can justify the extra US$36 (~AU$50) for 2 extra Panasonic caps, a better quality PCB and name brand resistors.
Any suggestions/justification for either?
IMHO i think that this extra cost is well justified.
If you get lets say caddocks or other resistors that have 1% tolerance that means the original values the designer has calculate will be present.
THD will be what he predicted etc. So imagine as far as resistor goes to have 20% tolerance.
You thing that your output will be the same?
The same goes with the other components as far as tolerance and magnetic behavior and other factors.
Wouldn't be to tedious to unsolder the components later for better ones?
Anyways thats just an opinion ;-)
The conclusion is to be happy with your sound
Nick
tiglitosa said:
IMHO i think that this extra cost is well justified.
If you get lets say caddocks or other resistors that have 1% tolerance that means the original values the designer has calculate will be present.....
Anyways thats just an opinion ;-)
The conclusion is to be happy with your sound
Nick
That's what I was after, I'm of course still open to others opinions but I think you mightve just justified the extra cost.
Cheers.
Premium kit is just the premium resistors and chips sorted for low offset.
You can get Classic kit and just order 6 additional resistors to save on cost (4 x 22k Caddock and 2 x 620R Rikens). 220R resistors are not really needed, and you can place jumpers in their spots.
Resistors tolerance is not critical, as long as they are matched to each other (in both channels)
You can get Classic kit and just order 6 additional resistors to save on cost (4 x 22k Caddock and 2 x 620R Rikens). 220R resistors are not really needed, and you can place jumpers in their spots.
Resistors tolerance is not critical, as long as they are matched to each other (in both channels)
Hi,
thanks to the help of this great thread finally I got my two monoblock amps with the audiosector premium kit working.
Everything went (almost) smooth, no hum, no bump when I switch off the amps.
I still need to build a passive pre, now I am just checking them connected to an ipod (headphone out connection so I can set volume).
I only get a bump when I switch on the ipod with the amps already on.
Thank to everybody here
Renato
thanks to the help of this great thread finally I got my two monoblock amps with the audiosector premium kit working.
Everything went (almost) smooth, no hum, no bump when I switch off the amps.
I still need to build a passive pre, now I am just checking them connected to an ipod (headphone out connection so I can set volume).
I only get a bump when I switch on the ipod with the amps already on.
Thank to everybody here
Renato
Hi,
unlikely, I need your help if you can. As I told you in the previous post, yesterday evening I completed my two monoblock amps with the Audiosector premium kit and they worked fine. I switched on-off many times the amps without any problem.
Today the fuses of both amps started to blow on both amps at switch on.
I use 2 trasnsformers 300VA with dual secondaries 25VAC (I am in Europe so the main rail is rated 230V). The fuses I used are 2AT (slow blow).
The only thing different with yesterday I can imagine is a slightly different tension (maybe higher) of the main rail so that the fuses that yesterday were just sufficient now blow.
What is your opinion? Can I slightly increase the ampere rate of the fuses?
Thank you for your help
Renato
unlikely, I need your help if you can. As I told you in the previous post, yesterday evening I completed my two monoblock amps with the Audiosector premium kit and they worked fine. I switched on-off many times the amps without any problem.
Today the fuses of both amps started to blow on both amps at switch on.
I use 2 trasnsformers 300VA with dual secondaries 25VAC (I am in Europe so the main rail is rated 230V). The fuses I used are 2AT (slow blow).
The only thing different with yesterday I can imagine is a slightly different tension (maybe higher) of the main rail so that the fuses that yesterday were just sufficient now blow.
What is your opinion? Can I slightly increase the ampere rate of the fuses?
Thank you for your help
Renato
Hey folks just wanted to say I got my kit built and it is working wonderfully. It sounds fantastic. I did had the RF interference problem the first day. But I managed to solve it with the fix suggested here in the first few pages. The only thing I do not have working is the LED. It is the little things.
Andrew thank you for the math. I will try your example.
I posted some pictures over here....
http://www.diyaudio.com/forums/showthread.php?postid=1828327#post1828327
Andrew thank you for the math. I will try your example.
I posted some pictures over here....
http://www.diyaudio.com/forums/showthread.php?postid=1828327#post1828327
Would there be any improvement by using 1500uf / 50 v Black Gates vs. 1000uf / 50 v? These are the standard BG and 1500uf / 50v is hard to find.
Also, I've been doing some reading on TVC (Sonic Euphoria good bass and dynamics, less clear, less linear) vs. resistor (Placette super clean but less bass and worse at the low volumes I listen at), vs. plain Alps motorized pot (a compromise between the other two) . Would 10k be a good value? My CDP's output impedance is 100 ohm.
Thanks
Also, I've been doing some reading on TVC (Sonic Euphoria good bass and dynamics, less clear, less linear) vs. resistor (Placette super clean but less bass and worse at the low volumes I listen at), vs. plain Alps motorized pot (a compromise between the other two) . Would 10k be a good value? My CDP's output impedance is 100 ohm.
Thanks
Hi,
this is just to thank you for the previous suggestions, it seems that the new increased values fuses (3A for now) do not blow anymore.
I still did not build a pre, so for now I can just use an ipod as source (using the head phone out), but I am already impressed by the sound.
The sound is clearly much more transparent than what I get by my valve Yarland integrated amp.
Unlikely I am also in the 5% of users with RF interference problems, so I am going to install in the next days the small caps at the amp input pins as suggested by Peter in post #51.
Thank you again
Renato
this is just to thank you for the previous suggestions, it seems that the new increased values fuses (3A for now) do not blow anymore.
I still did not build a pre, so for now I can just use an ipod as source (using the head phone out), but I am already impressed by the sound.
The sound is clearly much more transparent than what I get by my valve Yarland integrated amp.
Unlikely I am also in the 5% of users with RF interference problems, so I am going to install in the next days the small caps at the amp input pins as suggested by Peter in post #51.
Thank you again
Renato
Hi Peter and company,
I have a pair of 16 ohm bookshelf speakers (WR125ST w/ 16 ohm Alnico piezo) and two identical center tapped transformers (35 - 0 - 35). Both are from Pioneer SX-6 amplifiers. One is functional and currently powering the monitors, but they deserve something better.
I would like to build some LM3875 "premium" monoblocks for them without having to buy transformers but I'm totally out of my league here. On the back of the amplifier it has a VA rating is 280; there is also a 12 volt secondary which I'm guessing accounts for part of the 280 ratings.? But that should still be plenty for a single channel.? Can I safely build monoblocks with these if they will always see a 16 ohm load and I use decent heat sinks?
I looked at the spec sheet for the LM3875, but it didn't give me a definitive answer since all the Typical Performance Characteristics graphs only account for rail voltages up to 40 volts with 4 and 8 ohm loads, and I figure my rail voltages will be about 50V (35 x 1.4).
Thanks,
Roger
I have a pair of 16 ohm bookshelf speakers (WR125ST w/ 16 ohm Alnico piezo) and two identical center tapped transformers (35 - 0 - 35). Both are from Pioneer SX-6 amplifiers. One is functional and currently powering the monitors, but they deserve something better.
I would like to build some LM3875 "premium" monoblocks for them without having to buy transformers but I'm totally out of my league here. On the back of the amplifier it has a VA rating is 280; there is also a 12 volt secondary which I'm guessing accounts for part of the 280 ratings.? But that should still be plenty for a single channel.? Can I safely build monoblocks with these if they will always see a 16 ohm load and I use decent heat sinks?
I looked at the spec sheet for the LM3875, but it didn't give me a definitive answer since all the Typical Performance Characteristics graphs only account for rail voltages up to 40 volts with 4 and 8 ohm loads, and I figure my rail voltages will be about 50V (35 x 1.4).
Thanks,
Roger