Let's keep this thread alive 
Two new (?) GC topics to talk about:
(1) The supply:
One or two toroids, 160 VA or 225 VA, voltage ? I heard that 18 V should be optimal ? Is that 18 V DC ?
I use 2x160 VA, 25 V with 4x1000 uF per channel.
(2) The speaker cable:
47 labs states that the speaker cable is very important with the gaincard. Yesterday I tried cheapo (PVC) CAT5 cable, and the difference was very big. I used only a single CAT5 cable (4 pairs, colored and uncolored connected as + and -). With a big difference I do not mean necessarily better. It seems that the bass is *much* tighter, but I miss some bass also. The sound was a little harsh (sss) in the beginning, now it's better, probably also because of the burn-in. The stereo placement and detail are better I think. I should compare it again in a few days. Also I plan to try connecting more pairs, maybe braided. With my 93 dB/W speakers probably I do not need many more, 47 labs also uses very thin cable. (comparable to a single cat5 strand?)
Fedde
Two new (?) GC topics to talk about:
(1) The supply:
One or two toroids, 160 VA or 225 VA, voltage ? I heard that 18 V should be optimal ? Is that 18 V DC ?
I use 2x160 VA, 25 V with 4x1000 uF per channel.
(2) The speaker cable:
47 labs states that the speaker cable is very important with the gaincard. Yesterday I tried cheapo (PVC) CAT5 cable, and the difference was very big. I used only a single CAT5 cable (4 pairs, colored and uncolored connected as + and -). With a big difference I do not mean necessarily better. It seems that the bass is *much* tighter, but I miss some bass also. The sound was a little harsh (sss) in the beginning, now it's better, probably also because of the burn-in. The stereo placement and detail are better I think. I should compare it again in a few days. Also I plan to try connecting more pairs, maybe braided. With my 93 dB/W speakers probably I do not need many more, 47 labs also uses very thin cable. (comparable to a single cat5 strand?)
Fedde
fedde said:
If you look at the datasheet, 4 ohm power goes flat at just over 25 V DC. So i figure this is close to optimal. That means a trafo 18-0-18 with cap input.
160 VA was originally speced, but i have 225VAs lying around so will use those. If i'm happy with those, i may also try the 120VA units ApexJr has to see how much difference it makes (these are available cheap and that goes a long way t keeping the cost down)
Try a single twisted pair, with the individual wires spearated. I'd be interested in your result.
dave
opa549 gainclone
alot of people have talked about using the burr-brown chips, but it seems to go no further. well, i have just finished a pair, and i am very impressed with the results. i also have some lm3875's coming, so i can do a comparison at a later date. they are well worth a try if anyone is interested (and they are also available as samles, no minimal cost!), and also have a higher power output. if anybody else has used these, i would be interested to hear.
alot of people have talked about using the burr-brown chips, but it seems to go no further. well, i have just finished a pair, and i am very impressed with the results. i also have some lm3875's coming, so i can do a comparison at a later date. they are well worth a try if anyone is interested (and they are also available as samles, no minimal cost!), and also have a higher power output. if anybody else has used these, i would be interested to hear.
Crap-5.....
"With a big difference I do not mean necessarily better. It seems that the bass is *much* tighter, but I miss some bass also."
I have observed this with CAT-5 also - (falsely) detailed and hard sounding.
Try 10 pair or 20 pair indoor telephone cable instead - different insulation and sheath - sounds nicer to my ear, much nicer.
Also try playing with RC network values, at the amplifier output and across the speaker.
Eric.
"With a big difference I do not mean necessarily better. It seems that the bass is *much* tighter, but I miss some bass also."
I have observed this with CAT-5 also - (falsely) detailed and hard sounding.
Try 10 pair or 20 pair indoor telephone cable instead - different insulation and sheath - sounds nicer to my ear, much nicer.
Also try playing with RC network values, at the amplifier output and across the speaker.
Eric.
"Mr Feedback, you found a nice and enlightened work around..."
Thankyou.
It is sort of a tongue in cheek poke at the artist formally known as 'Prince'.
A few years ago, in response to 'Prince' (Punce more like ) changing his name to 'Person Formerly Known As Prince', an Oz radio network ran an afternoon drivetime phone-in competition to find a more suitable name.
I remember clearly a listener phoning in and saying "Why don't you just call him 'Davo' ", and the name stuck and he won a couple of CDs, and everybody had a good laugh.
Despite working with a lot of musos, I am still unable to take them entirely seriously, and if I can take the **** out, I will.
Eric.
Thankyou.
It is sort of a tongue in cheek poke at the artist formally known as 'Prince'.
A few years ago, in response to 'Prince' (Punce more like
) changing his name to 'Person Formerly Known As Prince', an Oz radio network ran an afternoon drivetime phone-in competition to find a more suitable name.I remember clearly a listener phoning in and saying "Why don't you just call him 'Davo' ", and the name stuck and he won a couple of CDs, and everybody had a good laugh.
Despite working with a lot of musos, I am still unable to take them entirely seriously, and if I can take the **** out, I will.
Eric.
(rasises hand)
um... i have a few questions about the power supply as well
1. i have two spare 300va 30v transformers - 30v seems a bit too much, is it possable to use 30v (probably more after rectification) if not what are the most efficant ways to bring the voltage dosn (bearing in mind this is all going to be in a small(ish) case)
2. i plan on using elna RSH 1000v 63v capacitors - are these good, cus i can get them quite cheaply?
um... i have a few questions about the power supply as well
1. i have two spare 300va 30v transformers - 30v seems a bit too much, is it possable to use 30v (probably more after rectification) if not what are the most efficant ways to bring the voltage dosn (bearing in mind this is all going to be in a small(ish) case)
2. i plan on using elna RSH 1000v 63v capacitors - are these good, cus i can get them quite cheaply?
I had this same question. I finally started wading thru the aleph X thread and realized that if i could use a secondary/channel i could use up a 600VA 25-0-25 i have.
Isn't it possible to take a single winding and make it look like a +/- supply? Something like the diagram below (i don't know whether the resistors in blue are required).
dave
Isn't it possible to take a single winding and make it look like a +/- supply? Something like the diagram below (i don't know whether the resistors in blue are required).
dave
Attachments
Here are a couple of interesting pages on powersupplies. Some schematics look like your idea, Dave.
Marc
http://www.tnt-audio.com/clinica/ssps1_e.html
Marc
http://www.tnt-audio.com/clinica/ssps1_e.html
Dave,
Check this thread http://www.diyaudio.com/forums/showthread.php?s=&threadid=7807
There was another one dealing with that subject, but couldn't find it.
Check this thread http://www.diyaudio.com/forums/showthread.php?s=&threadid=7807
There was another one dealing with that subject, but couldn't find it.
zeno said:
This is the latest article from this author over supplies. Go have a look:
http://www.zero-distortion.com/techno/powersupply/powersi.htm
Carlos
planet10 said:
The resistors are generally necessary to insure that the voltage divides equally between the capacitors. This sort of thing works fine for low current loads like op-amps, but I think you'll have problems if you try to run a power amp off this, unless you use very small resistors which will then burn a lot of power.
You also have to be careful what you connect to this "0V" point. If it goes to the chassis, and the chassis connects to the power system ground through the line cord (or through the shield of a cable that connects to AC power ground in another box), you could have big problems.
MR
A new ground
Peter / Dave:
Maybe this is what you're looking for:
http://www.diyaudio.com/forums/showthread.php?s=&postid=59181&highlight=supply+AND+GROUND#post59181
Peter / Dave:
Maybe this is what you're looking for:
http://www.diyaudio.com/forums/showthread.php?s=&postid=59181&highlight=supply+AND+GROUND#post59181
Fedde,fedde said:Let's keep this thread alive
Two new (?) GC topics to talk about:
(1) The supply:
One or two toroids, 160 VA or 225 VA, voltage ? I heard that 18 V should be optimal ? Is that 18 V DC ?
I use 2x160 VA, 25 V with 4x1000 uF per channel.
(2) The speaker cable:
47 labs states that the speaker cable is very important with the gaincard. Yesterday I tried cheapo (PVC) CAT5 cable, and the difference was very big. I used only a single CAT5 cable (4 pairs, colored and uncolored connected as + and -). With a big difference I do not mean necessarily better. It seems that the bass is *much* tighter, but I miss some bass also. The sound was a little harsh (sss) in the beginning, now it's better, probably also because of the burn-in. The stereo placement and detail are better I think. I should compare it again in a few days. Also I plan to try connecting more pairs, maybe braided. With my 93 dB/W speakers probably I do not need many more, 47 labs also uses very thin cable. (comparable to a single cat5 strand?)
Fedde
I use one transformer Amplimo (type 68015) of 225VA and +/- 25 Volts AC and I see the DC power having problems under heavy load (Going from 30Vdc dipping to about 26Vdc). Therefore I cannot imagine that 18Vac would be enought for the LM3875.
I use 4*1000uF (2 per channel) in the amplifier on the chip and some small 100uF in the power supply.
Initially I liked Cat5 for speaker cable but the sound was a little bit on the bright site.
An externally hosted image should be here but it was not working when we last tested it.
Maarten
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.