2P29L Preamp

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Paul Barker
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#16 Re: 2P29L Preamp

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Tick
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Ray P
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#17 Re: 2P29L Preamp

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Inspired by Mr. 'Speedy' Cresswell I've put a bit of effort into assembling my 2P29L DHT preamp today.

Most of the PCBs are built and installed. B+ supply connected and tested. A pair of Andrews DHT filament supplies installed and tested. Next is to hook up and test the Bartola 'Gyrator' boards - hungry now though so time to stop.

I removed the aluminium can from one of the 2P29Ls, they're like 'stubby' valves.

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Ray P
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#18 2P29L Preamp - Xmas Project #5

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I can't take the first four of my Christmas projects any further as I'm now waiting on parts so today I picked up this par-baked project as I will be needing a preamp for my SIT follower project quite soon. I spent a few productive hours getting all the power supplies hooked up and all is now in good order. Tomorrow I will connect and test the Muses volume control modules.
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Ray P
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#19 Re: 2P29L Preamp

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More progress on the preamp today, hooking up the Muses volume control boards and installing the output boards

The muses control section is mounted on the front panel but the actual volume control boards are on the rear panel, conncted by a ribbon cable. I had planned to install that and test the volume control functions today but after a previous bad experience I checked the ribbon cable and found a couple of discontinuities so I've ordered some cable and will make up my own connectors.

The preamp has a single input but three outputs - one Muses volume control module routes it's output to a pair of unity gain buffer outputs and a second routes it's output to the 20dB gain preamp stage, with each output from that having two connections, one direct coupled and one capacitor coupled - in essence its both and active and a passive preamp. The rationale behind this relates to my OB project - the buffered output will go to the bass amplifier, which has about 25dB of gain, and the actively outputs will go to the Follower 'power buffer' that I'll use with the full-range speakers. The passive and active preamp options are powered/switched separately so in other use cases I can use passive or active as appropriate.

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I need to arrange some alternative connectors to the plastic terminal block that I've used temporarily - the proper ceramic terminal blocks I normally use turned out to be too tall to fit under the lid!
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