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Old 29th August 2012, 02:14 PM   #1621
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Quote:
Originally Posted by Peter Daniel View Post
There's no common ground on rectifier boards (separate grounds for each rail which connect on amp board), so in your case just the wires from CHG for stargrounding.
Great, just to be safe . Still really loving the amp but my new speakers need some more juice. Thanks for answering.
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Old 2nd September 2012, 12:42 PM   #1622
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I've completed one of your builds, Peter - it sounds beautiful. Thank you!

Unfortunately, I'm getting loud pops when I turn on/off a (very cheap) desk lamp. Obviously I should just get rid of/move the lamp, but I'd like to do something about mains filtering.

I remember Marantz offered a power amplifier with a (large, expensive) battery partner. Instead of batteries, what about using a bank of supercaps? Can we completely separate the amp from the mains like that?

I'm also getting phone signal noise - I'm going to put together some shielded interconnects - so if there's something else people would suggest? I've seen some questions on here recently but I must have missed a solution if there was one...
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Old 5th September 2012, 01:42 PM   #1623
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Try that: Commercial Gainclone kit- building instructions

Bank of supercaps instead of batteries won't work here.
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Old 6th September 2012, 05:39 PM   #1624
jimchan is offline jimchan  Norway
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Default Low sensitivity speaker

Hi Peter, have the amp up and running, impressed by the clear sound but not singing as it should.

Dc offset is good, less than 10mv and no hum from the speakers even though not using exact star ground as recommended.

The bass is crisp, but the midrange and treble is distinctly lacking. Have tried with iPad and the Dac, and similar impression. existing HarmonKardon amp gives a full sound but not the clarity.

I note now my speaker sensitivity is 86db, 8 Ohm. Could this explain?

Br, Jim.
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Old 7th September 2012, 08:14 AM   #1625
AndrewT is offline AndrewT  Scotland
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Is the treble driver working?
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Old 7th September 2012, 08:56 AM   #1626
jimchan is offline jimchan  Norway
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good question, but yes. Ribbon tweeter is giving a slightly harsh response. bass OK, but underpowered. Mid range lacking.

230VA transformer, single rectifier to two amp boards.

I will also double check the correct component placing/sizing, but I have checked all this before.

Should I try with large capacitors (snubber) ?
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Old 7th September 2012, 05:02 PM   #1627
jimchan is offline jimchan  Norway
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Jepp....10.000 uF caps and snubber has given the amp what it needs to drive the speakers.

Sounds nice, and certainly different to the HK...
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Old 8th September 2012, 02:00 AM   #1628
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Default Bridged LM4780 Questions

I am building the LM4780 in bridged configuration with one transformer and rectifier board and two bridged amps and had a few questions. If my questions have already been covered, I apologize but I've looked and cannot find specific answers.

1. For star grounding, the OG on the amp boards are tied together with the middle of this connection grounded to the metal case enclosure. The PG+ and PG- on rectifier board are connected to this chassis ground as well. Is there anything connected to PG+ and PG- terminals on the amp boards?

2. Is the speaker output connected through both "OUT"s on the amp board? If so what is the polarity of each "OUT"?

3. Is the input connected to the amp board on both "IN"s? If so, what is the polarity of each?

Thanks in advance for any help.
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Old 8th September 2012, 04:39 PM   #1629
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Bridged configuration has been explained here (same as stereo setup): AudioSector-chip amp kits, dacs, chassis
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Old 8th September 2012, 06:21 PM   #1630
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Peter, thanks for the quick response. I've looked at Post#246 and the LM4780 Amplifier Schematic but I'm still not 100% sure how to connect the inputs and outputs for bridged configuration.

Is this right:
My input signal + wire goes to both "IN"s on amp board and my input signal - wire goes to both "SG"s on amp board?
Both "OUT"s from amp board go to speaker + terminal and "OG" on amp board goes to speaker - terminal?

Thank you for your time.
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