Valve phono stage using a JFET/ECC88 cascode to provide the gain and low noise of a solid state stage without the sonic cost of silicon and all the overload and sound advantages of valve stages.
- Overall gain 62dB at 1kHz
- Overload at 42v RMS output (40mv input)
- Frequency response within 0.25dB of RIAA (with 3.18us corner) from 20Hz to 20kHz
- Active loaded output driver provides low impedance output to preamp or integrated amp
- Choke power supply and shunt regulator per channel provides ultra low noise and stable power rails
- Direct input MC stage sutable for low output cartridges avoids the smearing and loss of detail associated with step up transformers (even the best ones)
- Single stage RIAA network employing zero loop feedback
- Selected components matched to within 0.1%
- Simple loading adjustment through RCA plugs loaded with resistor provides varying cartridge load.
- Good quality components used througout. Takman carbon and metal resistors, ICW Clarity Cap SA capacitors, JJ ECC88 and Philips 5687 triodes
BEST OF BOTH WORLDS
Traditionally there have been two ways of hearing your moving coil catridge, either the low noise capabilities of solid state (often commodity op amp) designs, or the increased transparency and tone of valve phono stages but then needing a step up transformer to provide adquate signal to noise ratio of low output cartridges. After experimenting with various phono stage designs, I came to the realisation that neither of the two tranditional methods actually let you hear what your cartridge was capable of. Using a hybrid design with a single ultra low noise JFET in a cascode arrangement with all valve stage following, you could get the best of both worlds, and have the low noise and accuracy of solid state designs, but the phase correctness, tone and overload margin of an zero feedback, single stage eq valve stage.
With a fully machined and lettered non ferrous case silver or black anodised fronts. I will be building the first of these in the next couple of weeks so that will potentially be available to use as a demo machine. if anyone wants to discuss this project I can be found via email to firstname.lastname@example.org
FIRST IMPLEMENTATION OUTSIDE THE WORKSHOP
The following pictures are of the first build of this design that has progressed beyond my workshop and listening room, and its now playing music through its owners system. The next step is to reproduce the electronics but this time in non ferrous casework with machined and lettered front and rear panels. Though I think the plain front looks rather nice as it is.
Images courtesy of its new owner Joe Lewis
The owner of the first one (Joe Lewis) has kindly written up his feelings after the first few weeks of ownership:
Right from the very off once the very cool blue light has stopped flashing after warm-up it’s very neutral, open and dynamic, the bottom is lush with no over extension or smear and after 5 minutes or so it starts to tighten and open up even more.
I’m running this through a Radford STA 25 Renaissance (EL34) with the SC-25 Valve pre. The turntable is a Thorens TD124 MKII with an Ortofon Rondo Red MC. Speakers are Dali Helicon 800 MKII’s.
It certainly got punch especially on the likes of Led Zeppelin III, Roxy Music – For your Pleasure – Stone Roses, David Bowie – Ziggy Stardust.
Coming back from the Turkey farm after not having a phono stage for a short while I must say that this stage certainly is different to my last stages.
Its more realistic, natural and not shouty like some are. Itâ€™s also not soft or woolly, it has presence, weight and really does reach down deep for those details. No distortion from what I can hear and is very quiet indeed.
It handles mono recordings with such ease. Sgt. Peppers Y/B original Mono pressing has such a lush sound and Small Faces Autumn Stone sounds rhythmic and loud bringing out all of that lovely studio amp buzz.
Blind Faithâ€™s â€˜Do what you likeâ€™ has one of the best drum solos ever to which sounds utterly superb and Stevies Hammond lead-in reprise is so funky. It sweeps in like it shouldâ€¦ with gusto. Respect to Ginger!
Pulps â€˜The Wicker Manâ€™ from the album â€˜We love lifeâ€™ has some great under watery sounds as well as the lovely Jarvis tones and it really does take you there â€“ not that you would want to go there in the first place. Iâ€™m from Sheffield myself and believe you me; the mentioned concrete channel really does exist!
I love it!… I’m finding myself switching it on a lot more often in the last few weeks of owning it. Previous to this stage I had the NVA Phono 2 and a PS Audio GCPH-100 and it really knocks the socks off these.
I’m finding the sound becoming more and more natural with each day. It gives the clean lines of CD but with realism, pace and none of that forwardness and un-relentless consistent fatigue.
Thanks Joe 🙂