Thanks Chris
I think I had the amp vol set below max because I was confused about its clipping behaviour. I now know that it can be left wide open and using preamp for volume control. My mistake.
Yes I could take out the pot but wanted it to be an integrated amp for most of its intended use. Was using preamp with low output source and inefficient speakers.
When the pot is replaced, I would recommend the circuit preceding the pot is connected to the "top" contact via a capacitance of a least 4.7uF (non polarised elect., or film) and after by capacitance of same value (or smaller if power amp input impedance is greater than 20K).
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Hi
....and your source is not able to "control" the volume?
foobar-(tidal, spotify....) - DAC(CD player) - Amp
chris
....and your source is not able to "control" the volume?
foobar-(tidal, spotify....) - DAC(CD player) - Amp
chris
Would you be kind enough to upload a sketch. It has been a while since I worked on this and I am feeling a bit doughy 😩
Sure it could control the volume but at max volume the speaker output is too low so I used a 5x gain preamp.
Hi Dunk02
Relax....😀😉😀.....dont feel pushed....its a hobby😀
i mean that your source should have a RCA connector and this you can connect to the RCA at your amp. then connect the hot wire of the first channel to the amp + and the othe cable to GND.
this you should repeat at the other channel. zoom in in my pic at the previous post)
chris
Relax....😀😉😀.....dont feel pushed....its a hobby😀
i mean that your source should have a RCA connector and this you can connect to the RCA at your amp. then connect the hot wire of the first channel to the amp + and the othe cable to GND.
this you should repeat at the other channel. zoom in in my pic at the previous post)
chris
Dunk, can you upload schematics you used?
Maybe some of the suggestions I make are already there, I need to check!
Maybe some of the suggestions I make are already there, I need to check!
really?
your source has such a small output level??
i used with this LM1875 a 4ohm 81db efficiency speaker and it works. not ultra loud but enough to stop after 3 minutes.
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Thanks Chris. I am chillin’ ��
I see how you have eliminated the pot. You could have included a pot and a bypass switch and have a dual purpose amp for use with or without a preamp? That was my original thought as I am still tinkering with speakers and sources and not wanting to commit to one configuration or another.
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This was a complete DIY hack using LM1875 boards. The inputs come from 3.5mm jack or RCA sockets directly to the pot and then to the two amplifier boards. Nothing tricky in the low voltage signal path.
My experience is probably the same as yours just did not want to be operating the amp near max power without any headroom before onset of clipping with loud transients.
Hi Dunk02
This is not what i mean. its enough without distortion.
at post #89 you wrote:
My intention is to mostly have it connected to an Apple Airport Express via a FiiO DAC (just for fun). My DIY Helium Micro Monitors may be the speakers I will keep connected On my work bench
The amp boards performance has been discussed in several places on the web and I probably won’t do much more testing, however here are some observations:
> @ 3/4 volume on iPhone through AEx and amp volume at 1/2 gives me nice listening volume in a large room with the larger bookshelf speakers
So what i mean is that your FiiO DAC should have 1,5V output (about 1Vrms) when you handy is at 3/4 max and that is for this amp enough. i did some measurements with 600mVrms- 650mvRms if i remember right and then i got clipping (max of the amp). so for me the pot is not needed. the volume control can be done by your apple.
chris
This is not what i mean. its enough without distortion.
at post #89 you wrote:
My intention is to mostly have it connected to an Apple Airport Express via a FiiO DAC (just for fun). My DIY Helium Micro Monitors may be the speakers I will keep connected On my work bench
The amp boards performance has been discussed in several places on the web and I probably won’t do much more testing, however here are some observations:
> @ 3/4 volume on iPhone through AEx and amp volume at 1/2 gives me nice listening volume in a large room with the larger bookshelf speakers
So what i mean is that your FiiO DAC should have 1,5V output (about 1Vrms) when you handy is at 3/4 max and that is for this amp enough. i did some measurements with 600mVrms- 650mvRms if i remember right and then i got clipping (max of the amp). so for me the pot is not needed. the volume control can be done by your apple.
chris
I will probably continue with the repaired amp without a preamp. I now have higher voltage DAP source. Not sure how the Chromecast Audio with Cheap Fiio DAC will go though.
I will strip down the old pot and see if there is any damage on the tracks.
I will strip down the old pot and see if there is any damage on the tracks.
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Thanks Chris
I could experiment with that before installing the new pot.
I also have turntable phono stage, DAP, Chromecast/Fiio DAC; all connected through a source switch-box
yep...try this please..
at post #84 you got the advice how to handle the pot and the cabling.
at your pictures i can see the drilled cable to the white connector at the amp board- its a XM-H connector i guess.
at post #84 you got the advice how to handle the pot and the cabling.
at your pictures i can see the drilled cable to the white connector at the amp board- its a XM-H connector i guess.
Not sure what type of connector, came with the LM1875 kit.
Have stop for tonight. Will check back in tomorrow. Thanks fellas��
Have stop for tonight. Will check back in tomorrow. Thanks fellas��
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Would there be any issues with adding signal input RCAs that go directly to the amplifier boards while still having the volume pot connected? Like a “preamp in”.
Also, should the signal wires going to the two channels have the same matching lengths to reduce the likelihood of channel imbalance due to differences in impedence?
Also, should the signal wires going to the two channels have the same matching lengths to reduce the likelihood of channel imbalance due to differences in impedence?
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