Group order of non-inverted LM4780 pc boards? Anyone interested?

[carlosfm]

The Primo amp has a small PSU, measured power is much less than what they say.
I saw this on another (more serious) magazine, don't ask me what, I don't remember.

The Primo CD is really a joke.
It uses a Samsung CD-ROM (some years ago, the worse CD-ROMs in the market, my hardware experience), they use the internal CD-ROM Dac , they just take the line out from the CD-ROM and buffer it.
Read: buffer, not amplify.
This anecdote has 750mv output and treble starts to roll off at 8khz, being very low in output much before 20khz.
Digital out is taken directly from the CD-Rom to an RCA output.
The CD player is very noisy in operation (figure out, with a fast CD-Rom...).

Now the best part: critics say the sound is "smooth".
My god, it's all too bad to be true.
I read audio magazines in the bathroom, some people call it the "library".
Audio Analogue is not an example of italian design, I've heard several gear from them and it's nothing special, even expensive things.
They can rave what they want, they can't fool me.
Sorry.

 

[Ed LaFontaine]

Mongo read in library too. Mongo don't think it change what come out.

I look forward to comments relating to the value of (properly) bridging LM4780

 

[Peter Daniel]

I'd prefer to bridge 2 parallel amps, which comes to using 2 LM4780 chips per channel.

 

[cdoggy81]

Ok Peter, lets get crackin on that

 

[yuri777]

Carlos F.
I have a question for you

Let's say i want to adapt your regulated PSU circuit to drive a pair of NI LM4780 PCBs from this thread (running in parallel)

Since the LM338s can deliver a maximum of 32V, if i want a more powerful amplifier, i will have to use a different type of regulator..

Do you think this one will work?

http://www.national.com/pf/LM/LM317HV.html

By reading the spec sheet, it seems like the values for the resistors on your circuit will have to change.. but nothing else..

thx

 

[alexw88]

I think for the LM338 32V is the output to input voltage difference, not the absolute output voltage.

Also LM317HV is capable for 0.5A only.....

 

[troystg]

Hi Alexw88-

Part Number=LM338T
Package Type=TO 220
Pins=3

InputMax Voltage=40 V <---- 40 volts absolute for "intended" installation. Unless it is not referenced directly to ground, then possibly higher voltage opperation is possible.

InputMin Voltage=4.2 V
Output Current=5000 mA
Output Min=1.2 V
Output Max=32 V


Thanks,

Troy

 

[carlosfm]

Carlos F.
I have a question for you
Let's say i want to adapt your regulated PSU circuit to drive a pair of NI LM4780 PCBs from this thread (running in parallel)
Since the LM338s can deliver a maximum of 32V, if i want a more powerful amplifier, i will have to use a different type of regulator..

I think for the LM338 32V is the output to input voltage difference, not the absolute output voltage.

Yuri, you have the answer here.
Anyway, 30~32V is the way to go, don't go higher.

Output Current=5000 mA

This is nominal current, absolute maximum is 12A.

 

[alexw88]

Troy,

On the LM338 datasheet it said :

"Since the regulator is “floating” and sees only the input-to-output
differential voltage, supplies of several hundred volts can be
regulated as long as the maximum input to output differential
is not exceeded, i.e., do not short-circuit output to ground."

If I understand this statement correctly , the LM338 only care about the Vin to Vout difference. In the spec, all the graphs only listed the Vout-Vin as parameter, never mentioned the Max Vin or Max Vout in the spec.

 

[carlosfm]

...the LM338 only care about the Vin to Vout difference. In the spec, all the graphs only listed the Vout-Vin as parameter, never mentioned the Max Vin or Max Vout in the spec.

Yes, maby the sky is the limit.

 

[yuri777]

So, if i want to run four LM4708s for biamping my Maggies 2.7QRs, i could use two 330VA 25-25 toroids and two boards with the regulator circuit..
that should be more than enough to drive four channels, right?

i know Alex has a single 500VA 25-25 trafo for his two channel 3875 gainclone, but seems like overkill..

 

[troystg]

Hey Alex88-


Notice the key word "Unless". The older I get the more I find out nothing is absolute.

I have seen a circuit that was operating at 150 VDC and had a voltage divider circuit going to ground reference.

It worked well but was not a "graceful" solution.



Thanks,

Troy

 

[BrianGT]

Here is a picture of the new boards that came in today. This is a comparison of the LM3785 board and the LM4780 board. I can mail out the boards soon, but I am still waiting for a couple of components to arrive from the kit.

--
Brian

 

[BrianGT]

Here are some better pictures that I took with my good camera:

front:

An externally hosted image should be here but it was not working when we last tested it.

back:

An externally hosted image should be here but it was not working when we last tested it.

--
Brian

 

[troystg]

Brian-

Beautiful. Brings a tear to the eye.


Thanks,

Troy

 

[Vuamp2]

Brian,

Look at the "back" image that you posted earlier... Look like you have a broken trace to the most left pin on the bottom row of the LM4780

 

[Vuamp2]

Brian,

Look at the "back" image that you posted earlier... Look like you have a broken trace to the most left pin on the bottom row of the LM4780.

 

[Peter Daniel]

That's not a broken trace. It's a ground trace used to further separate output from the input. Don't ask me if it's gonna work, but I thought it's worth trying.

 

[Vuamp2]

Thanks Peter. It may help some. We will see

 

[lgreen]

Dimenions?

Ok, looks great, I've even got my preorder in. Hey, what are the dimensions of these boards? I need to know because I'm going to lay them out next to each other.