LM3875 build with X-10D based valve stage - where to put the attenuation? - diyAudio
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Old 7th March 2012, 07:26 AM   #1
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Default LM3875 build with X-10D based valve stage - where to put the attenuation?

Hi team - I've built my second chip amp, this time with an integrated valve buffer on the input. If I was to wire in a pot (Alps blue velvet either 10K or 50K) would I be best to wire it in between inputs & valve buffer - or between valve buffer and amp. The chip amp is driven by a Teddy Pardo powerreg supplying 28V/5A fully regulated. I'm happy to listen to any suggestions as to the logic in this, as well as a view on which pot will suit better. The valve buffer is a clone of the Musical Fidelity X-10D with a pair of 6922's (Phillips Jan) - I do have a bunch of other valves including Mullards and Genalex.
By the way - this sounds way better than the cost to build would suggest - very happy. Happy to answer questions on any part of the circuit that anyone is interested in.

AJ

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Last edited by ajst2duk; 7th March 2012 at 07:37 AM. Reason: Added photo
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Old 7th March 2012, 11:43 AM   #2
AndrewT is offline AndrewT  Scotland
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Where do you sit when listening to the stereo?
Where would you like the volume control to be?

Why are you considering putting a volume control on the power amplifier?
The right place for your power amplifier is right beside the speaker terminals.
In my opinion that's the most inconvenient place to locate a volume control.

In closing, where do you locate your remote control/s?
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Old 7th March 2012, 05:57 PM   #3
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The amp will sit between the speakers - no remote. All I'm looking to do us to put a volume pot in so I can use this as a single source integrated - the question is - is this a good idea - and where would the pot be best to sit in the circuit - straight off the source inputs or between the tube buffer and amp PCB.
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Old 9th March 2012, 04:10 AM   #4
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OK well I guess I will try a 10K pot between source and the buffer, that seems to be a logical place to start. - AJ
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Old 5th April 2012, 11:38 AM   #5
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Ended up putting it between buffer and amp as I thought the source would benefit from seeing the buffer direct. It is awesome - no unwanted impact on the sound
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Old 5th April 2012, 11:44 AM   #6
AndrewT is offline AndrewT  Scotland
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Generally one inserts a buffer where the Source equipment cannot properly drive the cable running to the next stage.
This requires the buffer to be located at the output of the Source.

You should be trying to identify which Sources cannot drive the following cables. Then, if needed, insert the buffer at the transmit end of that cable/s
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Old 6th April 2012, 03:40 AM   #7
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You are a bottomless font of great knowledge Andrew - thanks.
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