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Old 4th November 2007, 02:09 PM   #1951
bfslm is offline bfslm  Brunei
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Many thanks Andrew for your sugestion, I actually very newbie in this DIY section so need to learn alot from your guy who have lots of experience.

with your suggestion, I may op to go with 2 x 225 VAC transformer(mono block), 9% regulation typical, 30 VDC secondary . Is it good?. Peter recommended of using 22VDC supply voltage????

A bit concern me, You recommended of 56VDC- 70VDC supply voltage but Peter recommended that transformer for LM3875 must have supply voltage of <42VDC,



Again thank you
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Old 4th November 2007, 02:31 PM   #1952
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Quote:
Originally posted by bfslm
For LM3875, should we use 2 transformer 160 VA mono block or 1 of 300 VA or 2 300 VA transformers, what option extract best performance from LM3875. For 6 ohm speaker, what Dc voltage workbest: 18, 20, 22, or 25 V DC. Becasuse i can customer make for trans. We use 220V AC in our country.
While transformer ratings given above will work fine from technical POV, over the years I noticed that for some reason bigger transformer is better sonically. So presently I'm using 300VA units only (either for mono or stereo) with 2 x 22V AC secondaries. This produces approx 34V DC rail voltage.

"56VDC- 70VDC" suggested previously was voltage between rails.

300VA transformers are also recommended for dual mono configuration (although 220VA will work fine too).

As to the LM3875 chip configuration, I don't recommend paralleling. Bridging would be good, but with 6ohm load it is not really suitable (although it will work). Besides, you would need a balanced source/preamp. So a single chip per channels is the way to go.
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Old 4th November 2007, 11:15 PM   #1953
bfslm is offline bfslm  Brunei
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Many thanks Peter,

Clear now for transformer selection. I'll go with 300/2x22VDC.

Few question.
- What's size of PBC board, both amp and rectifiers boards, with heigh, for premium kit and upgraded with BG BGN100/50 and BG STD 1000/50 as Peter recommended.
- Can I order BG BGN100/50 and BG STD 1000/50 from you as well and what's price of upgraded premium kit (LM3875). How can I order it via audiosector (with BG upgrade).

Still can not contact Peter via email for DAC order cause new register.

Rgds,
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Old 5th November 2007, 02:21 PM   #1954
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Both amp and rectifiers PCB size is 30x74mm. The caps height as follows:

Panasonic FC1500/50 36mm
BG N 100/50 31mm
BG STD 1500/50 41mm

You can get those caps from me. My direct email address can be found here: http://www.audiosector.com/contact.asp
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Old 8th November 2007, 07:48 AM   #1955
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Peter, I have a LM4780 gainclone from you in parallel configuration. How would I go about to lowering the gain on the LM4780 to match the gain of the Aleph 3. I am planning to use them for bi-amping with the Aleph3 powering the tweets and the LM4780 to power the mids of my Epos ES11 speakers.

Thanks.
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Old 15th November 2007, 07:24 AM   #1956
ssmith is offline ssmith  France
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Hello Peter,
I have a DAC with a passive output (a DDDac), and am thinking of running it through a low Zin passive pre. Not ideal, so think a buffer on the dac output may be the solution -- and your posts and schematic for the ML-based buffer caught my eye... and was wondering if PCB's are available?
rgds ssmith
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Old 15th November 2007, 08:01 AM   #1957
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Safetyman,

Peter's circuit is based on the datasheet one, albeit with carefully chosen components to maximise performance, so you can use that info to calculate the two resistors you need to change, (sorry, I can't remember offhand their designations). Just one point to be aware of, don't go below a gain of ten or the amp will become unstable.
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Old 16th November 2007, 03:04 AM   #1958
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Quote:
Originally posted by safetyman
Peter, I have a LM4780 gainclone from you in parallel configuration. How would I go about to lowering the gain on the LM4780 to match the gain of the Aleph 3. I am planning to use them for bi-amping with the Aleph3 powering the tweets and the LM4780 to power the mids of my Epos ES11 speakers.
You can increase the value of R3/R5 to 1k5 or so. If that won't help you may also increase the input series resistors (R6/R7) to whatever value will work for you.


Quote:
Originally posted by ssmith
I have a DAC with a passive output (a DDDac), and am thinking of running it through a low Zin passive pre. Not ideal, so think a buffer on the dac output may be the solution -- and your posts and schematic for the ML-based buffer caught my eye... and was wondering if PCB's are available?
Yes the PCBs are available, contact me for pricing info.

http://www.diyaudio.com/forums/showt...978#post805978
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Old 16th November 2007, 12:43 PM   #1959
ssmith is offline ssmith  France
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Quote:
Originally posted by Peter Daniel

Yes the PCBs are available, contact me for pricing info.

http://www.diyaudio.com/forums/showt...978#post805978
Thanks, that was the schematic I was referring to. PM sent.
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Old 16th November 2007, 10:27 PM   #1960
mikelm is offline mikelm  England
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Hi ssmith

your picture looks like brainwave coherence across alpha, beta, delta & theta. . . ,

or am I mistaken ?

mike
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