Pentode/triode phonostage finished

Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

Here is a link to the final version of the phonostage I posted a couple of weeks ago. It uses a single 6gh8a for each channel. The front end uses the pentode section and the triode section is used for output. Equalization is through a lumped passive network between the stages.
I used a seperate ground system for signals and for DC current. I used the chassis as a ground plane for signals. The power supply and DC current returns are grounded to the chassis with a star ground so no direct current flows through the chassis. When I first posted I was still tracking some hum. Moving the star ground point away from the power supply eliminated the hum completely. A slight hiss becomes audible as the volume control approaches maximum. Under normal listening conditions the sound system is silent.
This sounds a lot better than my first phonostage. It used two SRPP connected 12ax7s per channel. I had used a passive RIAA network with it too, but it was much too low an impedance for the ax7. The 12ax7 also seemed to have some trouble driving the volume control and passive crossover. The 6gh8a seems to have no trouble with the network or the output. Highs go higher, and are clearer and smoother than before. Bass is deeper and fuller.
Obviously I'm still feeling the glow of just finishing a new project, so I'm probably not being objective enough. For the moment, though, I am very pleased with how this thing sounds.
Paul

Phonostage (Open in New Window)

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Topic - Pentode/triode phonostage finished - Paul Scearce 12:06:28 01/31/03 (11)

A similar finished - PÃ¤r 23:20:55 02/03/03 (2)

Re: A similar finished - Paul Scearce 11:57:49 02/04/03 (1)

Re: A similar finished - PÃ¤r 23:48:46 02/04/03 (0)

bravo! nt - chiggy 14:34:58 02/02/03 (0)

Re: Pentode/triode phonostage finished - Allen Wright 15:24:58 02/01/03 (1)

Re: Pentode/triode phonostage finished - Paul Scearce 05:40:17 02/02/03 (0)

Re: Pentode/triode phonostage finished - J Epstein 14:50:42 02/01/03 (2)

Yes - very nice <nt> - Jim Dowdy 08:56:06 02/02/03 (0)

Re: Pentode/triode phonostage finished - Paul Scearce 04:54:23 02/02/03 (0)

Re: Pentode/triode phonostage finished - sj701 18:22:18 01/31/03 (1)

Re: Pentode/triode phonostage - Paul Scearce 07:17:00 02/01/03 (0)

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