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Old 31st March 2007, 08:24 PM   #1641
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Quote:
Originally posted by JonE2435
I had 2 questions about the LM4780. If i just run it in stereo mode with 8ohm what transformer should i get? I was thinking a 32 vct. Also, how should i implement volume control?
I would recommend at least 200VA transformer, 300VA even better. The rectifier board is designed to work with dual secondaries, centertapped transformer will work too, but some modifications are required. 32VCT is OK, but I prefer 2 x 22V AC.

Potentiometer can be mounted at amp's input, a diagram below shows the connections:
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Old 1st April 2007, 05:11 AM   #1642
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Really? 300VA for 2 8ohm speakers on one chip not parallel? I thought 300VA was need to power 2 of the chips?
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Old 2nd April 2007, 11:49 PM   #1643
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Recently my dac was damaged when I tried to connect it to my high definition tuner. It turned out that the wiring in my apartment was very off: ground and neutral were hot, hot was neutral, and the cable line acted as an earth ground, shorting everything using a grounded ac connection, killing my dac and my computer monitor.
When looking over the board one of the traces near the digital input was vaporized, plating the wood support with gold. I was hoping to be able to replace the damaged parts, but since the board is shot, I'll have to rebuild it, this time as the usb version. Do you know when a kit with the usb board will be available, and how much will it probably run?

Thanks
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Old 3rd April 2007, 12:18 AM   #1644
ttan98 is offline ttan98  Australia
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Peter,

You must have read the amp shoot out at StereoMojo website. I suppose you have submited your chipamp for review allowing them to compare your amp with other amps in a shoot out situation.

I hope you may or can clarify a few points raise there,
the comments which include the following direct quotes from the reviews:

Weakness:
Bass could be boomy at times; slight upper midrange boost; 2D image and soundstage; limited bass; cupboard sounding mid-bass that was also a bit forward; occasionally compressed sound;

This is only part of the comments raise there. There are of couse strengths as well. Those interested should go to stereomojo website.

My objective is not to hightlight the negatives of your product but to ask you why this might be. I find one possible explanation would be equipment partnership. The comment which is of particular interests is bass boomy and sound forward, my experience being that these qualities can be tweaked to be less prominent in light of equipment compatibility. You may like to advise us what needs to be done if we experienced the same situation.

I am a believer in chipamp and currently building a 6 channel amp myself. Your comments because of your experience would be invaluable.

Many thanks.
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Old 3rd April 2007, 04:56 AM   #1645
DeanP is offline DeanP  Canada
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Question LM4780 questions - case help

Hi,
I'm going to put two trannies in one case and was wondering what would be the best distance to put these apart? What would be the minimum distance?
Also, where in Canada could I buy a piece of copper plate 3"x15"x0.250" - online if possible?
Would it hurt, to put in the case with the amps, an electronic crossover?
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Old 3rd April 2007, 01:50 PM   #1646
rnzr is offline rnzr  Estonia
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hi, wanted to ask that can i put Schottky diode between mains ground and chassis groundpoint to protect the amp and the amp case? i live in the terraced house and i guess the house main ground is the same in all apartments, so if my nieghbour connects the ground to mains accidently and i turn the volume then i get electric shock or sth

any thoughts? or am i too sceptic

ronald
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Old 3rd April 2007, 02:17 PM   #1647
mikelm is offline mikelm  England
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ground is tied to ground - if your neighbor connects live mains to ground then he blows a fuse !

If your ground is not tied to ground - then it's very big problem
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Old 3rd April 2007, 02:54 PM   #1648
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Default Re: LM4780 questions - case help

Quote:
Originally posted by JonE2435
Really? 300VA for 2 8ohm speakers on one chip not parallel? I thought 300VA was need to power 2 of the chips?
It is one chip in stereo mode, so it's like 2 x LM3886. 300VA toroid is quite suitable here. Of course, you can use 80VA as well, but the results may not be as good.


Quote:
Originally posted by sdedalus
Recently my dac was damaged when I tried to connect it to my high definition tuner. It turned out that the wiring in my apartment was very off: ground and neutral were hot, hot was neutral, and the cable line acted as an earth ground, shorting everything using a grounded ac connection, killing my dac and my computer monitor.
When looking over the board one of the traces near the digital input was vaporized, plating the wood support with gold. I was hoping to be able to replace the damaged parts, but since the board is shot, I'll have to rebuild it, this time as the usb version. Do you know when a kit with the usb board will be available, and how much will it probably run?
If you used my DAC board, the circuit is not connected to Earth mains and switched power wires would not damage the DAC. However, it looks like the signal from your source might have done it.

The USB version will be available in few weeks. The price will be lower than current SPDIF version, as less critical components will be used.


Quote:
Originally posted by DeanP
Hi,
I'm going to put two trannies in one case and was wondering what would be the best distance to put these apart? What would be the minimum distance?
Also, where in Canada could I buy a piece of copper plate 3"x15"x0.250" - online if possible?
Would it hurt, to put in the case with the amps, an electronic crossover?
I don't think the distance is critical here, I've seen designs where toroids were stacked or put side by side without any separating distance. For metals, check Metal Supermarkets, they have multiple locations. Placing crossover with the amps is not a problem, it may be actually an advantage (no interconnects).


Quote:
Originally posted by rnzr
hi, wanted to ask that can i put Schottky diode between mains ground and chassis groundpoint to protect the amp and the amp case? i live in the terraced house and i guess the house main ground is the same in all apartments, so if my nieghbour connects the ground to mains accidently and i turn the volume then i get electric shock or sth
You must have been reading previous post
If you are concerned about those issues, don't connect amp circuit to the chassis, and connect only the chassis to Earth ground. Using diodes here shouldn't be a problem.

Another alternative could be connecting the amp's output ground to the chassis only, without any connection to mains ground.
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Old 3rd April 2007, 03:24 PM   #1649
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Default Re: To:Peter D.

Quote:
Originally posted by ttan98
You must have read the amp shoot out at StereoMojo website. I suppose you have submited your chipamp for review allowing them to compare your amp with other amps in a shoot out situation.

I hope you may or can clarify a few points raise there,
the comments which include the following direct quotes from the reviews:

Weakness:
Bass could be boomy at times; slight upper midrange boost; 2D image and soundstage; limited bass; cupboard sounding mid-bass that was also a bit forward; occasionally compressed sound;

This is only part of the comments raise there. There are of couse strengths as well. Those interested should go to stereomojo website.

My objective is not to hightlight the negatives of your product but to ask you why this might be. I find one possible explanation would be equipment partnership. The comment which is of particular interests is bass boomy and sound forward, my experience being that these qualities can be tweaked to be less prominent in light of equipment compatibility. You may like to advise us what needs to be done if we experienced the same situation.

I am a believer in chipamp and currently building a 6 channel amp myself. Your comments because of your experience would be invaluable.
Actually, I was was not aware of that shootout and only learned about it last weekend when one of the panelists contacted me through e-mail with some questions about 'the "real cost" of building a kit himselfself.'

I'm also not sure which version of Patek they used, it may well be one of the earlier amps with different caps (the current version uses red BG N on amp boards). The amp in a test must have been a personal property of one of the readers.

It looks like it's been a tough and fair test, but also somewhat limited in assesment.

Regarding the weaknesses: "Bass could be boomy at times; slight upper midrange boost; 2D image and soundstage; limited bass; cupboard sounding mid-bass that was also a bit forward; occasionally compressed sound" you may notice that those comments, in one way or another, have been also used with regards to basically any other amp in a test, so maybe the problem here was the room itself or the whole system as such.

Those GainClones are certainly not universal amps and a lot of care and tweaking is required to achieve best results. Placing the amp into a randomly chosen setup will bring only average results, and that has been documented in the recent shootout. However, with more care, the results can be still spectacular, the best example of bass performance is the choice of GC in a system described here: http://www.6moons.com/audioreviews/w...tric/300b.html where my monoblocks (small boxes beside equipment stand in a picture) are used to power 30-foot long straight bass horns.
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Old 4th April 2007, 02:56 AM   #1650
DeanP is offline DeanP  Canada
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Thanks for the help!
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