Paolo,
do you have two or four bridges?
If only two, maybe your transformers are connected wrongly (out of phase).
If you have four bridges and no other connections to the transformer you must check and double check ALL your connections and the PCB. Believe me, there is always room for faults and mistakes. Did you check out all voltages, offset etc.?
Hum and noise always means wrong or missing connections. If you sound is low and muddy, maybe the connections to your soundcard is loose. If you read the provided manual carefully nothing shoud go wrong at the end of the day.
do you have two or four bridges?
If only two, maybe your transformers are connected wrongly (out of phase).
If you have four bridges and no other connections to the transformer you must check and double check ALL your connections and the PCB. Believe me, there is always room for faults and mistakes. Did you check out all voltages, offset etc.?
Hum and noise always means wrong or missing connections. If you sound is low and muddy, maybe the connections to your soundcard is loose. If you read the provided manual carefully nothing shoud go wrong at the end of the day.
Preferrably one for each chip.
You can go with 2 x 25V transformer if you need more power, check page 13 of the datasheet for more info: http://cache.national.com/ds/LM/LM4780.pdf
You can go with 2 x 25V transformer if you need more power, check page 13 of the datasheet for more info: http://cache.national.com/ds/LM/LM4780.pdf
Hi Peter,
I'm still getting some problems with my LM3875 premium kit
. I'm using 2 toroids (300VA, 2x22v) and 2 rectifiers and the sound is way to low. Mesuring between V+ and PG+ and V- and PG- I get 30v. I've checked every wire, every solder joint and I can't figure out what's happening 
. My speakers are 90dB and I used to have a Sonic Impact T-amp and it drove them very well.
Can you post some pics or more info for newbies like me to check and see how you do it?
Thanks.
PS. the sound is quite good, warm and detailed, but very low. I'm using it in power configuration connected to a Ibook and a Marantz A/V reciever.
I'm still getting some problems with my LM3875 premium kit
. I'm using 2 toroids (300VA, 2x22v) and 2 rectifiers and the sound is way to low. Mesuring between V+ and PG+ and V- and PG- I get 30v. I've checked every wire, every solder joint and I can't figure out what's happening . My speakers are 90dB and I used to have a Sonic Impact T-amp and it drove them very well. Can you post some pics or more info for newbies like me to check and see how you do it?
Thanks.
PS. the sound is quite good, warm and detailed, but very low. I'm using it in power configuration connected to a Ibook and a Marantz A/V reciever.
Hi again,
Still with the same problem
. I've introduced a 50k pot in the game and I have to turn it to maximum to get sound at a reasonable volume, but then I can hear some very audible interference on the speakers. The output offset is around 25mv with source connected. I need some help please .
Paulo
Still with the same problem
. I've introduced a 50k pot in the game and I have to turn it to maximum to get sound at a reasonable volume, but then I can hear some very audible interference on the speakers. The output offset is around 25mv with source connected. I need some help please . Paulo
Paulo, can you measure the resistor values and post what is in each position on the pcb? It could be that the gain is too low. I doubt that you switched the 22k and 220R caddocks, because then things would really be messed up, but maybe the 22k caddocks or 680R rikens are the incorrect values.
EDIT: you could also look at the caddocks, the resistance is printed on the package, and look at the rikens for the band pattern, this website will show you how to read it to get the resistance:
http://www.reprise.com/host/circuits/resistor_colorcodes.asp
EDIT: you could also look at the caddocks, the resistance is printed on the package, and look at the rikens for the band pattern, this website will show you how to read it to get the resistance:
http://www.reprise.com/host/circuits/resistor_colorcodes.asp
The pictures of assembled boards can be found here: http://www.diyaudio.com/forums/showthread.php?postid=584425#post584425 I was using different caps than supplied in a kit though.
The amp has quite a high gain, so you shouldn't have problems with volume. What source are you using?
The amp has quite a high gain, so you shouldn't have problems with volume. What source are you using?
Peter,
Thought I'd share a pic of my non-typical use of your rectifier boards. Now you can say you do tube amp boards.
Thought I'd share a pic of my non-typical use of your rectifier boards. Now you can say you do tube amp boards.
An externally hosted image should be here but it was not working when we last tested it.
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