| JoeBob |
| Thanks for the reply Peter, and I'm sorry for the off-topic post. Btw, just ordered a couple, thanks alot for such a great service to us canadian diyers, duty and tax at the border sure is horrible. |
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| rabstg |
Hey Peter and Brian-
I'm in for a set or two of these boards.
Thanks,
Troy |
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| Firebug24k |
| I'd buy two of the "beta" boards as well - just let me know where to send the money :) |
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| rnoble |
Brian and Peter,
I was wanting to order one of your kits (basic with monoblock), do I have to wait for a group purchase or just order online from the website?
Kind regards
Rod |
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| Peter Daniel |
| Just order from website. |
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| Peter Daniel |
| As promised, I did some revisions to the previous layout (mostly cosmetics, with some traces modified). Here's the final layout of amp's board. There is one SMD resistor for muting setting. I think it would be a good idea to provide an extra pad (not neccessarily through hole) for a bigger size resistor, if somebody doesn't want to bother with SMD parts. |
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| Peter Daniel |
And here's the PS layout. Since that set is high power, parallel configuration, I would imagine that each amps board needs dedicated PS board and it should be offered either as a single set (1 + 1) or stereo set (2 + 2).
The mounting and connection holes are matching and boards can be positioned side by side (vertically) |
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| Peter Daniel |
| I sent the layout to Brian, for further revisions and aproval. Not much is needed to get the ball rolling, so probably within next few day the files should be sent for prototyping. |
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| carlmart |
| quote: | Originally posted by Peter Daniel
And here's the PS layout. Since that set is high power, parallel configuration, I would imagine that each amps board needs dedicated PS board and it should be offered either as a single set (1 + 1) or stereo set (2 + 2).
The mounting and connection holes are matching and boards can be positioned side by side (vertically) |
I understand, even if I don't agree with, using thin width on audio passing tracks to avoid stray capacitances. But on a supply pcb?!
Why not filling larger areas for each interconnection between e.g.: D2-D4, D1-D3 and so on? Rectangular blocks would probably do the job fine.
You can also design a single side pcb for the PS, as only one input intercrosses other lines.
Carlos |
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| Peter Daniel |
I don't see much reason to go with single sided board here. PS board will be done together with the amp's board, and since this one is double sided, the PS board can be too.
As to the width of the traces, 100mil is pretty wide, the size of the board is only 1.2 x 2.9 so connections are really short. I don't think anything wider is neccessary, but I also think it wouldn't hurt either.
I'm tempted though to put shielding on one side (connected to mounting holes only) in case rect board is piggy backed with amp's board. |
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| Peter Daniel |
Here's the trace width increased to 120 mil. It is fine like that.
I also tried 140mil, but didn't feel comfortable with that width, if not only for difficulties with soldering. |
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| fireman |
Having read this thread since the beginning, I must say I am quite interested in it. One question that has not really been addressed is the VA rating of the transformers that will be used to power these amps. In post # 56 mhennessy came to the concluson that 25 to 28 volt secondaries would be required to power them. Unfortunately, I don't recall reading anything about the VA rating.
I know that Steve of Apex Jr has some 28.4 V at 150 VA Avel-Lindberg toroids so I was wondering if these would work in a dual monoblock configuration. I quite sure they would be under powered for the bridge configuration but would they be OK for the single board configuration ? |
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| Peter Daniel |
| Those transformers would probably work fine with the boards, but again, higher wattage may be even better. |
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| rabstg |
Everything in my GC is shielded and the amp is DEAD QUIET as a result. I would hate to but the diodes close to the audio circuitry and have noise induced there when the shielding could help prevent that.
Thanks again, and anxiously waiting,
Troy |
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| BrianGT |
Well, I spent some time looking over the LM4780 files, and will get some boards made soon.
Here is a picture of the board, showing both layers and silkscreen:
and a picture of the bottom layer of the pcb:
The pcb is very similar to the size of the LM3875 board, but the amplifier board is a bit bigger. The overall dimensions of the pcb is 2.9" wide by 5.2" deep, compared to the LM3875 board being 4.8" deep.
Any comments on the layout? The recent modifications that Peter and I made are:
- move input wiring a bit farther from the output, and add ground trace in between
- remove ground plane from rectifier board and restructure a bit
- slight modifications to placement of zobel components.
- increased size of SMD pads for mute resistor to allow a through-hole resistor to easily be soldered in this place.
I am looking to get the boards made soon, after I look over the layout a few more times. I am considering doing a small prototyping run first for testing first.
--
Brian |
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| rabstg |
Hey BrianGT-
You said:
"- remove ground plane from rectifier board and restructure a bit"
Why did you remove the ground plane? Does it cause a problem that I am unaware of?
Thanks,
Troy |
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| BrianGT |
| quote: | Originally posted by rabstg
Hey BrianGT-
You said:
"- remove ground plane from rectifier board and restructure a bit"
Why did you remove the ground plane? Does it cause a problem that I am unaware of?
|
I didn't think that it would be very useful in the way that it was setup, and might possibly pickup more noise then prevent. The recent one that Peter created wasn't tied to anything, and would be tied to ground on the chassis side. I decided that I would rather have the design of the rectifier board to mirror the current LM3875 board, since it seems to work rather well. Notice that I intentionally didn't put wiring for two boards from one power supply board, since the LM4780 will draw more power (should be same as 2xLM3875 boards). The dual-mono configuration will be standard with the kit.
As for a bridging board to go with the kit, I haven't had time to do any prototypes, so I decided to leave it out of the kit. Maybe after a few DRV134 boards have been prototyped, I will add a board for it to the pcb set.
--
Brian |
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| Variac |
| I thought that there was going to be room for diode heatsinks and a logical layout to make it easy to attach a htsnk plate between the rows of diodes so people could use them if desired, or use the rectifier boards for other projects. |
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| Peter Daniel |
I did one layout with diodes facing back to back and one heatsink plate, but then we discussed with Brian the possibility (and danger) of rectifiers touching each other (when not aligned properly) and creating hazardous situation, especially when the boards are to be used by so many people.
There is still enough room to use two heatsink plates, shared by 4 diodes. |
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| rnoble |
I hope this is the right place for advice on GC kit ideas :)
I am considering a 3 channel GC project. I have just ordered the parts and am now planning the layout. However in this planning my ohms law is a little rusty these days, particularly with “VA” ratings which I took to mean Volts*Amps which confuses me on Power which is V*I which is also volts by amps! Anyway I have some questions below and would really appreciate some experienced DIY Amp builder’s input.
I have attached an image with the topology of the setup.
- Can a 300VA tranny successfully run 3 gc amps?
- Is a 300mm long by about 70mm high finned heatsink enough to keep them cool?
- Will the tranny draw more than recommended 3A slow blow fuse?
Using a larger transformer, possibly 400VA is an option but costs will rise (including case requirements). The datasheet for the LM3875 would suggest that 34v post rectified is ok for running 6ohm speakers but was wondering what others experiences were on this.
A picture of the case with its heat sinks (an AKSA kit is being used) is on the link below. Transformer will be the same as seen (if feasible) but naturally the rest will be different, using GC kits from BrianGT. Case example |
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| Peter Daniel |
Here's the board in 3-D:
 |
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| Peter Daniel |
| quote: | Originally posted by rnoble
- Can a 300VA tranny successfully run 3 gc amps?
- Is a 300mm long by about 70mm high finned heatsink enough to keep them cool?
- Will the tranny draw more than recommended 3A slow blow fuse?
|
I don't see a problem with 300VA trafo to support 3 channel of GC.
The heatsink size should be fine too.
If the fuse blows, just replace it with a bigger one. I find the biggest problem with fuses blowing, the inrush current at start up. In my case 3A fuse is not big enough, but again, I'm running it at 120V AC from mains. |
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| BrianGT |
I placed an order for pcbs for the 4780, and will start taking orders sometime soon. The kit details are finalized and the webpage for the kits is being finalized now.
--
Brian |
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| Vuamp2 |
Brian,
Look great!
Would it alows you to have larger trace between pin #14 and pin #20 if you move it to the other side (Red)? |
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| BrianGT |
| quote: | Originally posted by Vuamp2
Brian,
Look great!
Would it alows you to have larger trace between pin #14 and pin #20 if you move it to the other side (Red)? |
not really. I attached a pdf of the final files that were sent to the board manufacturer (Advanced Circuits) last week, and they are 80% done now, in the screening phase where they apply the silkscreen. Seems like they could possibly arrive here next week.
:)
I will start taking orders soon.
--
Brian |
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| theChris |
to the poster of the VA vs Power
VA -- this is RMS voltage multiplied by RMS current. however some elements will store energy for later use. this means not all energy is used each cycle and thus power is less then V*I in (some) AC systems.
if you pay an electric bill, you can see how much energy you use vs how much you store/supply. this is "power factor" and should be close to 1.0. if it falls below something like 0.95 you will be chraged... |
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| Peter Daniel |
| quote: | Originally posted by Vuamp2
Would it alows you to have larger trace between pin #14 and pin #20 if you move it to the other side (Red)? |
That particular trace is for muting purpose only, and what is presently on the board is quite suitable for that. Doing it in a top layer (red) would be a good alternative as well. We might consider it in the next revision. Thanks for the input. |
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| BrianGT |
| quote: | Originally posted by Vuamp2
Brian,
Look great!
Would it alows you to have larger trace between pin #14 and pin #20 if you move it to the other side (Red)? |
Sorry for the quick response. You are right about the trace between pin 14 and pin 18, used for the mute circuit. We will look into this when we look at the next revision.
--
Brian |
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| Vuamp2 |
Brain,
I am sure that both Peter and you are correct. I just want to make sure that we are taling the same thing....
Post #215 posted by Brian show there is a small trace connects between pin 14 and 20. I don't see any trace between pin 14 and 18.... am I just don't read these image correctly? :cannotbe: |
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| BrianGT |
| quote: | Originally posted by Vuamp2
Brain,
I am sure that both Peter and you are correct. I just want to make sure that we are taling the same thing....
Post #215 posted by Brian show there is a small trace connects between pin 14 and 20. I don't see any trace between pin 14 and 18.... am I just don't read these image correctly? :cannotbe: |
It was a typo on my part. You were correct about it being between 14 and 20. I am sorry for the confusion.
--
Brian |
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| jiawu232 |
hello! every one :
I one to design a power amp to a cd player,using chip(LM3886),I wonder if it needs a pre-amp.
think you very much to shou me out!
by the way,
Does anybody have LM3886.PCB?
best
wish to you!
blue |
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| rabstg |
Hi-
digi01 has some LM3886 boards and pwr regs and he is in China also.
I ordered some and am eagerly awaiting there arrivile.
Thanks,
Troy |
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| jiawu232 |
Thank you very much to show me this message,but I don't know hao to contact digi01,would you please show me a hand again?
Happy mid-autumn day!!!! |
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| rabstg |
Hi jiawu232-
digi01 has this thread:
http://www.diyaudio.com/forums/show...&threadid=38506
And you can email him through the forum.
I have ordered a set of his boards and his ZEN headphone amp and am awaiting their arrival.
digi is a GREAT person to deal with.
Best of luck!
Thanks,
Troy |
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| fireman |
| quote: | Originally posted by BrianGT
The new website is up at:
www.chipamp.com
--
Brian |
Holy macaroni Batman, that is a very professionnal looking web side you got :D
Keep up the good work :up: |
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| bg40403 |
Sam Tellig reviewed the Primo by Audio Analogue in the June issue of Stereophile.
an excerpt:
As you turn the Volume knob or press Volume on the remote, an array of small LEDs tells you where you stand with the gain. Roberto Martini has done a superb job with the look of this gear. The potentiometer is a National Semiconductor LM1972 integrated resistor network, with no buffers. According to Marco — next time I shall interview Nadia — each channel uses two “power pack ICs” to deliver a rated 70Wpc into 8 ohms or 110 W p c into 4 ohms. “ Power packs?” “A power pack is an integrated circuit that can manage power,” Marco explained. “It’s a kind of power op-amp. We use the same one that Jeff Rowland uses in his Concentra integrated amp — the National LM3886T. “Power packs have advantages over discrete component circuits,” Marco continued. “They save space, save heat, are totally protected against overloads and short-circuits. Each power pack uses a pair of bipolar output transistors in a quasi-omplementary mode. The two power packs are then connected in a fully balanced bridge configuration. So neither the positive output post nor the negative output post is at ground voltage. ” “And this is important?” “Noise. Or lack there of. This type of circuit uses two identical power amplifiers per channel. One amplifier works with the input signal, while the other works with a mirror signal, the same as the original input signal but with polarity reversed. “ The speaker is connected between the two outputs of the two amplifiers.
The original signal drives the positive input of the loudspeakers while the mirror-image signal drives the negative input. The power supplies of each polarity float, with none of the
capacitor-charging current contamination of ground circuitry. “Power packs save space, as I said.
Using two small power-pack amplifiers per channel, we can obtain 70 Wpc. If we used one power -pack amplifier per channel, we’d get 20W. ” “ Marco, you say each power pack
contains two bipolar output transistors. Do you have NPN complemented with PNP?” Output transistors come in two flavors: neutral-positive-neutral (NPN) and positive-neutral-positive (PNP). Usually, one complements the other to make a matched pair. “Only NPN bipolar transistors are used within each power pack,” Marco replied. “This makes the power stage not quite symmetrical, a little like a tube stage. Maybe this explains why this particular power pack offers such good sound and some other power packs don’t. ” Purists can pooh-pooh integrated circuits. When you introduce the term opamp, many audio purists think of the crappy analog output stages of inexpensive CD players, where each op-amp might cost 5¢ or 10¢. How do you think they make the stuff so cheap? To get a handle on the Primo integrated, I didn’t prime the Primo CD player right away. Instead, I routed a Creek CD50 Mk.2 CD player into a new McIntosh MDA 1000 D/A converter ($8000), removing the latest McIntosh MC275 tubed power amp ($3500). Speakers were the Opera Callases — no time to fool around if I’m to beat the Milanese hi-fi paparazzi. They’ll first read about it here. Ha. All of this was blatantly unfair to the Primo CD player. I used an $8000 D/A converter into a $3500 tubed power amp and compared this combo to an $895 solid -state integrated that was built for size, convenience, and price . . . and good sound. I preferred the Mac MC275. You shouldn’t be surprised. What surprised me was how much I enjoyed the Primo integrated on its own terms. The Mac MC275 sounded tubed. Well, it is tubed. While the Primo integrated isn’t tubed, it sounded tube-like to a remarkable degree. What I love about the Primo integrated is its tonality — my main concern, really. Call it the Claudio factor — orecchie di pipistrello. Resolution was very good — not exceptional, but probably beyond what you might expect for $895. But the tonality was exceptional. Violins. Cellos. Tenor sax. Female voice. Opera — the genre, not just the loud-speaker company. With the Operas, this system was Italy in a box — |
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| bg40403 |
After review of the posted 4780 boards along with the National app note, it appears to me that it can be configured in bridge mode with the following changes:
Jumper R7, R8 & R9
"Cross" R5 with R6, that is change one leg of R5 from GND to input and change one leg of R6 from input to GND.
It remains to determine the proper values for R1-R6.
I submit this for your review and look forward to your comments |
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| 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.:clown:
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 :eek: :eek: :eek: , 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.:clown:
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".:clown:
My god, it's all too bad to be true.:bawling:
I read audio magazines in the bathroom, some people call it the "library".:D
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.:xeye: |
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| bg40403 |
Mongo read in library too. Mongo don't think it change what come out.:scratch2:
I look forward to comments relating to the value of (properly) bridging LM4780 |
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| Peter Daniel |
| I'd prefer to bridge 2 parallel amps, which comes to using 2 LM4780 chips per channel. |
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| cdoggy81 |
| Ok Peter, lets get crackin on that :) |
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| 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 |
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| 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..... |
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| rabstg |
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 |
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| carlosfm |
| quote: | Originally posted by 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..
|
| quote: | Originally posted by alexw88
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.
| quote: | Originally posted by rabstg
Output Current=5000 mA |
This is nominal current, absolute maximum is 12A.:eek: |
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| 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 :confused: , 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. |
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| carlosfm |
| quote: | Originally posted by alexw88
...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.:D |
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| 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.. |
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| rabstg |
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 |
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| 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 |
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| BrianGT |
Here are some better pictures that I took with my good camera:
front:
back:
--
Brian |
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| rabstg |
Brian-
Beautiful. Brings a tear to the eye.
Thanks,
Troy |
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| 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 |
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| 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. |
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| 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.;) |
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| Vuamp2 |
| Thanks Peter. It may help some. We will see :cannotbe: |
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| lgreen |
| 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. |
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| BrianGT |
I received the last shipment of parts for the LM4780 kits. I also managed to get one channel working tonight. It seems to work rather well. I haven't done any extended testing, as I only have one channel finished. I will take some pictures once I can find my digital camera charger.
The kits should start shipping out this weekend. I will be putting together the shipment of parts for Peter tomorrow morning to mail up to him. (already mailed him some board for his testing).
--
Brian |
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| Evan Shultz |
Was any thought given to using a differential input instead of single ended? That would open up the board to balanced inputs along with possibly an cleaner input.
I had lots of trouble getting a LM3886 quiet but it was much, much easier with a differential input. |
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| rabstg |
Hi Evan-
Did you use a differential buffer for the LM3886?
If not, can you post your circuit layout? |
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| Peter Daniel |
So here it is, first two boards assembled ( as I believe Brian assembled only one so far ;)).
I got a bit sidetracked with my recent experiments with TDA1541 DAC, but yesterday I finally managed to put together those boards and today I hope to put it into a chassis and compare with 3875 chip (that's why I used similar components). It seems like leaving rectifier board connected is a good idea and I will feed two double bridges from common secondaries.
I must say that this board came up pretty nice actually and there is not a single thing yet I would like to change here.;)
It seems like double aluminum oxide insulators might work here, as they provide more than enough spacing on mounting holes. In that case a push bar would have to be used.
I will be experimenting with bridged configuration soon. |
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| Peter Daniel |
| Here's another, more artistic picture: |
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| peranders |
They have a very professional good look. I like it. :up: :nod:
Just wondering, what is the obvious advantage to your design compared to using only one LM3886 (I know that LM4780 contains two LM3886 dices)? |
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| m0tion |
Peter:
From your pictures it appears that you've used larger capacitors (physically) on one of your LM4780 amps than the other. Are the larger capacitors (physically) black gate? Are they higher capacitance? Why did you choose to use different capacitors on each of the LM4780 amps? |
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| carlosfm |
| quote: | Originally posted by Peter Daniel
It seems like leaving rectifier board connected is a good idea and I will feed two double bridges from common secondaries. |
I don't think it's a good idea at all, Peter...
PSU diodes near the signal inputs?:xeye: |
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| Peter Daniel |
| quote: | Originally posted by carlosfm
I don't think it's a good idea at all, Peter...
PSU diodes near the signal inputs?:xeye: |
If I didn't try it I wouldn't say so. I'm using this arrangement in my monoblocks and I don't see any problems whatsoever. I was kinda surprised myself, but I usually try things before making any comments;) |
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| Peter Daniel |
| quote: | Originally posted by m0tion
Peter:
From your pictures it appears that you've used larger capacitors (physically) on one of your LM4780 amps than the other. Are the larger capacitors (physically) black gate? Are they higher capacitance? Why did you choose to use different capacitors on each of the LM4780 amps? |
On one board are 1500u Panasonics. I tried them already in a protoype and they work fine. On the other board are 1000u BG STD, to show that they also fit the board. |
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| peranders |
| quote: | Originally posted by carlosfm
I don't think it's a good idea at all, Peter...
PSU diodes near the signal inputs?:xeye: |
I this case I'll agree with Peter :nod: I have also rectifier pretty close and have no problems with that. Picture here if you want to check. |
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| Peter Daniel |
| P-A how do you make such nice quality pictures? |
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| peranders |
1 1300 W halogen with an umbrella
2 A good tripod, very stable
3 White, silver and grey cardboards
4 Minolta F100 4MPx (an "old" camera now, 2 years old)
5 Remote control (in order to avoid vibrations)
6 Manual exposure
7 Manual focusing
8 Manual white balance
9 5 different exposures for each picture
That's it! :nod:
Hints: Don't mix different light sources => bad colours
Calibrate the white balance before each session.
Your latest picures weren't too bad. You only have to get a bigger white cardboard plus an additional to get more controlled relections. |
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| Peter Daniel |
And what for background?
If I have enough time, I also use tripod, remote and no flash, natural light, but never tried those additional diffusors with a lamp. |
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| peranders |
I have never used a background. If you have a cardboard size 0,7 x 1 m (2.5' x 3.5') or so you won't need a background.
... ooh, I forgot... Photoshop of course.
1 Unsharp mask (a must!), Unsharp maks is like waxing your car. It simply gets better, a win-win situation :nod:
2 Make sharper (occationally)
3 Levels, sometimes
4 Contrast, brightness often
5 Colour balance, not often
I have not practiced so much using "curves" but this makes wonders also... but... nothing can be as good as a good taken picuture to begin with. Put most of your efforrts there and try also to handle those cardboards carefully so you don't get scracthes becuase this creates much work in Photoshop to remove. |
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| carlosfm |
| quote: | Originally posted by peranders
1 1300 W halogen with an umbrella
2 A good tripod, very stable
3 White, silver and grey cardboards
4 Minolta F100 4MPx (an "old" camera now, 2 years old)
5 Remote control (in order to avoid vibrations)
6 Manual exposure
7 Manual focusing
8 Manual white balance
9 5 different exposures for each picture |
Aaahhhh... I see you know what you're doing!:cool:
I can't leave my trusty Canon T90 because there has to be invented a digital (or whatever) SLR as good as this, and such a pleasure to use.
Probably the best manual-focus SLR ever made.:angel: |
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| BrianGT |
| quote: | Originally posted by Peter Daniel
[B]I believe Brian assembled only one so far ;)
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At least I listened to my one channel, instead of spending a bunch of time taking pictures of it ;)
--
Brian |
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| cdoggy81 |
Good one Brian :) How does it sound BTW?
What will you be bringing to ATL DIY this year?
Still not 100% if I'm going or not... My girl gets 4 wisdom teeth out that Thursday so depending on how she feels Friday night I may or may not make it :( |
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| BrianGT |
| quote: | Originally posted by cdoggy81
Good one Brian :) How does it sound BTW?
What will you be bringing to ATL DIY this year?
Still not 100% if I'm going or not... My girl gets 4 wisdom teeth out that Thursday so depending on how she feels Friday night I may or may not make it :( |
Chris,
I will finish it and bring it with me.
If you make the trip this year, try not to get arrested for excessive speeding again. ;)
--
Brian |
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| cdoggy81 |
Thanks Brian.... funny you should mention.....
I was making a left hand turn Friday (the 22nd) on to 7th street. Got in the turn lane just before 6th street, drove past it & made my turn on 7th. Got pulled over & given a ticket for $118 for not turning on to 6th street B/C I drove in the center lane. I CAN'T GET A BREAK!!! :mad: :mad: :mad:
:smash: $118 :smash: |
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| Peter Daniel |
| quote: | Originally posted by BrianGT
At least I listened to my one channel, instead of spending a bunch of time taking pictures of it ;)
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I made those pictures to have a proof that I'm actually doing something about those boards;)
I read somwhere that Florida drives are the worst in America. |
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| bg40403 |
Peter said: "I will be experimenting with bridged configuration soon."
Peter, are we likely to find one day that we can combine boards into a BPA 200 arrangement?
Regards, |
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| BrianGT |
| quote: | Originally posted by bg40403
Peter said: "I will be experimenting with bridged configuration soon."
Peter, are we likely to find one day that we can combine boards into a BPA 200 arrangement?
Regards, |
This is part of the master plan :)
--
Brian |
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| BrianGT |
| quote: | Originally posted by Peter Daniel
I made those pictures to have a proof that I'm actually doing something about those boards;)
I read somwhere that Florida drives are the worst in America. |
Florida drivers do suck, as they are mostly old people who shouldn't be allowed to drive.
Georgia drivers are ok. While they tend to drive rather fast, they are usually courteous.
--
Brian |
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| DWong |
Brain and Peter,
Good to see that the kits are ready. When will you send out the kits for international orders?
Dennis |
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| BrianGT |
| quote: | Originally posted by DWong
Brain and Peter,
Good to see that the kits are ready. When will you send out the kits for international orders?
Dennis |
I am shipping out the US orders now, and I shipped all the parts for the international orders up to Peter last week, and they should arrive by the end of this week, meaning that the international orders should start shipping out at the end of this week, or early next week, depending on the shipment.
--
Brian |
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| m0tion |
| Could I use a 70VCT@625VA transformer (35-0-35) to power 6 LM4780 amps, or would I need a larger transformer? How would I calculate the current draw for the 6 LM4780 amps all driving 8ohm loads? |
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| bg40403 |
m0tion,
With 70 VCT you would provide about +/- 50 V to the chips. This, we are told by the app. note would lead to serious heat problems.
Each Lm4780 is about equal to 2 Lm3886. We have seen that an LM3886 needs a minimum of 80 VA, and more is better. So, 6 LM4780 should have at least 960 VA...and more is better. |
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| lgreen |
| I received my boards today. Thank you! they look very nice. Can't get a project out right away but its good to have one in the hopper. |
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| motherone |
| Got my boards today. Thanks Brian & Peter.. They look great! |
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| JimD |
Brian,
Received my LM 4780 pc boards yesterday. They look great!
Is there a schematic I can use to determine which components go where on the pcb?
Thank you
Jim |
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| Peter Daniel |
| I'm sure Brian is coming up with something. In a meantime you can use this schematic from National's site. |
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| Peter Daniel |
| When looking an that pic, two power resistors are from the outputs (0.1R). Two horizontal resistors, closest to the chip, are 20k(or22k) feedback. Between power resistors, from left to right: 20k (input to ground), 2 x 1K (or 680 for more gain), and 2 x 1k (or 220R) series input resistors. |
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| JimD |
Peter
Thank you. That should get me started.
OFF TOPIC
Have you constructed any gaineclones utilizing all Riken Resistors?
If so what is your impression in relation to the sound of the premium component combination with Caddocks and Riken?
Jim |
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| Peter Daniel |
I never built an amp using all Rikens. I don't think it will work well. I tried Rikens at feedback position, but to me, Caddocks works the best there.
Today I replaced Dales (in gain seting position) in my ML preamp with Rikens and they didn't even last an hour there. I switched back to Dales as they sound better there.
Everything is circuit dependant and only you can tell what sounds best for you . ;) |
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| JimD |
Understood.
Thank you.
Jim |
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| cdoggy81 |
| Has anyone tried the HOLCO's? I've heard a few good things on the Asylum forum. Nothing about chip amp applications though :) Peter, any usage??? |
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| Peter Daniel |
Holcos are OK, but not the best. They don't posses the clarity of Rikens and Caddocks and can sound a bit veiled/mellow. However they are usually better than Dales, for instance.
There is no simple answer which is really better, for as my previous post shows, everything is circuit (and system) dependant.
Whenever I build more complicated circuits, with more resistors, Holcos are my first choice because of the relatively low price.
My first GC had Holcos at feedback location, and it sounded fine.... untill I tried Caddocks ;)
Good carbon resistors might work well here, but I still didn't find the right ones. |
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