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AudioSector-chip amp kits, dacs, chassis

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Hi Peter,

I have now gotten my LM3875 premium kit up and running. Things are humming away nicely on a set of nice little heatsinks and the proper transformer should be in the mail to me today (22v 400Va as opposed to the 18v 750Va intended for an Aleph X). Now I am considering adding a pot to make an integrated with the possibility of adding extra sources as well. I read back in the archives that you have tried several different pots and a stepped attenuator as well. What would you suggest for pot values (10K, 50K) and brand (Noble, PEC)?

Thanks

DaveM
 
I would suggest 25K - 50K Noble pot.

There is also another project coming out: a remote controlled volume attenuator with 130 steps and highest quality available. This will be better than all the pots and better than most of that type units available presently on the market.

You can read more about here: http://www.diyaudio.com/forums/showthread.php?postid=839425#post839425

The boards went already into production, I'm still waiting for my assosiate to develop programming. ;)

Here's the schematic (there's always only 7 resistors in a signal path: series and shunt positons):

An externally hosted image should be here but it was not working when we last tested it.
 
Thanks for the heads up. I was aware of that and I am eyeing that to use in my X-BOSOZ that should have parts comming my way soon from the endless group buy. I believe that a decent pot will do just fine as this amp will probably end up in a room where the spousal acceptance factor must be high, and the end placement of the speakers will probably be less than optimal. :bawling:
But we will see. I'm going to make sure to be able to short around the pot if needed, so that when the pre is done, I can use it as a straight amp. Now I just need some time in the shop to get the chassis completed.

Thanks

DaveM
 
Oh yeah, the caps come from one czech high-end speaker company Xavian. I replaced them for normal 1500mF electrolyts yeasterday and it's defenetely the MKPs causing the problem with RF!

The size might be the issue, they act as an antenna....quite expensive, but useless idea anway:apathic:

I will possibly look for those BlackGates N Peter uses in his patek. They are hard to get here in Czech rep though...
 
hayena said:
Oh yeah, the caps come from one czech high-end speaker company Xavian. I replaced them for normal 1500mF electrolyts yeasterday and it's defenetely the MKPs causing the problem with RF!

The size might be the issue, they act as an antenna....quite expensive, but useless idea anway:apathic:


You may try to shield your big MKP caps with copper foil (connect shield to ground) and use additional small bypasses directly on amp's board, like 1 - 10uF caps perhaps. Otherwise, with MKP connected with wires, there is no capacitance directly at amp's supply pins and that may be causing problem as well.
 
copper foil works wonders;) :nod:
 

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Peter, just wanted to update on what happened to my LM4780. It was my own stupidity. After endless searching, what was wrong, it turned out to be a dry joint on the signal input on PCB side. :xeye:

Now it's playing nicely on both channels and no hum. Thanks for all the help. Now onwards to the LM3875. :D
 
Peter Daniel said:


There is also another project coming out: a remote controlled volume attenuator with 130 steps and highest quality available. This will be better than all the pots and better than most of that type units available presently on the market.

You can read more about here: http://www.diyaudio.com/forums/showthread.php?postid=839425#post839425

The boards went already into production, I'm still waiting for my assosiate to develop programming. ;)

Here's the schematic (there's always only 7 resistors in a signal path: series and shunt positons):

Looking forward to see this.
I hope the "better than most of that type units available presently on the market" also mean the best price on the market. ;)

Sam
 
Copper bar-stock on sale at OnlineMetals.com

Hi Peter,

Just ordered the Primo LM3875 kit. Having fun sourcing chassis and PS parts. (Really.)

javascript:smilie(':smash:')Wanted to pass along that Online Metals is practically giving away 1"x1.25" solid copper bar stock in 1 foot bars for $21.74.:smash:[/url]

The bargain price kinda dissolves if you have them cut-it. (It's worth it having them cut the aluminum panels though...)

For those who aren't aware of them, Online Metals is a great source for small quantities and custom cuts for that high-end Peter Daniel look...

Here's the copper bar:

https://www.onlinemetals.com/merchant.cfm?pid=4325&step=4 -Rob
 
Re: Copper bar-stock on sale at OnlineMetals.com

Rob Thomas said:
javascript:smilie(':smash:')Wanted to pass along that Online Metals is practically giving away 1"x1.25" solid copper bar stock in 1 foot bars for $21.74.:smash:[/url]

The bargain price kinda dissolves if you have them cut-it. (It's worth it having them cut the aluminum panels though...)

The current price for that size extrusion is CAD$29.50/foot at my local Metal Supermarket outlet. Adding shipment costs it may not be such a big giveaway. ;)
 
Got my DAC this morning. Thank you for the increadibly speedy delivery. You will have to tell me your secret! I posted a package to Oxford, 60 miles from where I live, on Wednesday by Special Delivery (next day before 13:00) and it still hasn't arrived!

Now the important bit: It sounds fantastic. It doesn't attempt to ram a performance down your throat and highlight any imperfection in a recording, unlike the Krell setup [280 CD and 300iL amp] I used to own. It is very musical.

Can you supply me with the details for creating a Patak-style case for it?
 
Yeah, the Canada Post is especially good with International shipments, a person in Australia got his DAC already as well. OTOH, the same shipment to US may even take up to 3 weeks. Now, what's their secret? ;)

I also have the feeling that this DAC is quite special, I'm using one myself, and I'm not tempted to put on the Levinson ML360S in a system at all.

Here some pics for chassis construction.

Start with a U channel made out of wood, with metal plate front and back. You may spray the inside with conductive nickel paint, although it's not necessary.
 

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