Longdog Audio http://www.longdogaudio.com Bespoke Audio Design & Build Mon, 08 Oct 2018 15:59:13 +0000 en-GB hourly 1 Valve Regulated 300B http://www.longdogaudio.com/valve-regulated-300b/ http://www.longdogaudio.com/valve-regulated-300b/#respond Mon, 01 Dec 2014 18:50:41 +0000 http://www.longdogaudio.com/?p=304 Power supply 1: 6080 and ecc83 as shunt regulator powering output stage

Power supply 2: Low noise solid state regulator power driver stage

Driver stage using two stages of 5687

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Power supply 1: 6080 and ecc83 as shunt regulator powering output stage

 

Power supply 2: Low noise solid state regulator power driver stage

 

Driver stage using two stages of 5687

 

Interstage coupled to 300b output stage

 

Amorphous core output transformers

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300b/GM70 Monoblocks http://www.longdogaudio.com/300bgm70-monoblocks/ http://www.longdogaudio.com/300bgm70-monoblocks/#respond Mon, 01 Dec 2014 18:49:31 +0000 http://www.longdogaudio.com/?p=302 Circuit is a C3g Pentode voltage amplifier with VR tube screen regulator, then 300b driver to 1:1 amorphous interstage to GM70 grid. Output TX 7k amorphous.

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Circuit is a C3g Pentode voltage amplifier with VR tube screen regulator, then 300b driver to 1:1 amorphous interstage to GM70 grid. Output TX 7k amorphous. Driver and 300b supply, series regulator using 6080, ecl82 and 0d3 (Steve bench inspired). TJ-Meshplate 300b, running 330v @ 55ma. Copper plate GM70 running 1020v @ 110ma.

 

All transformers by Automatic Electric Europe

 

GM70 and 300b DC heated using TentLabs units.

 

Rough specs, -3dB points (5w into 8ohm) 18Hz, 52kHz. 3% distortion reached at 42w into 8 ohm.

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211 A2 Amp http://www.longdogaudio.com/211-a2-amp/ http://www.longdogaudio.com/211-a2-amp/#respond Mon, 01 Dec 2014 18:47:41 +0000 http://www.longdogaudio.com/?p=300 Circuit is 6sn7 voltage gain, the el84 cathode follower direct to 211 grid, in a similar fashion to Ongaku. The A2 driver is capable of sending the grid at least 40v positive, so peak power is just above 30w.

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Circuit is 6sn7 voltage gain, the el84 cathode follower direct to 211 grid, in a similar fashion to Ongaku. The A2 driver is capable of sending the grid at least 40v positive, so peak power is just above 30w.

 

All transformers by Sowter Transformers

 

211 DC heated using TentLabs units.

 

At 1w the frequency response is 10hz to 37kHz at -3dB, 20hz to 24kHz at -1dB

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Moving Coil Direct Input Valve Phono Stage http://www.longdogaudio.com/moving-coil-direct-input-valve-phono-stage/ http://www.longdogaudio.com/moving-coil-direct-input-valve-phono-stage/#respond Mon, 01 Dec 2014 18:45:18 +0000 http://www.longdogaudio.com/?p=298 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. SPECIFICATIONS Overall gain 62dB at 1kHz Overload at 42v RMS output (40mv input) Frequency response within 0.25dB of RIAA (with […]

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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.

SPECIFICATIONS

  • 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.

 

EXPECTED COST

 

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 info@longdogaudio.com

 

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

 

REVIEW

 

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. It’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 Faith’s ‘Do what you like’ 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 should… with gusto. Respect to Ginger!

 

Pulps ‘The Wicker Man’ from the album ‘We love life’ has some great under watery sounds as well as the lovely Jarvis tones and it really does take you there – not that you would want to go there in the first place. I’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 🙂

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Fully Balanced Valve Preamplifier Bp1 http://www.longdogaudio.com/fully-balanced-valve-preamplifier-bp1/ http://www.longdogaudio.com/fully-balanced-valve-preamplifier-bp1/#respond Mon, 01 Dec 2014 18:40:30 +0000 http://www.longdogaudio.com/?p=296 Transformer coupled (Sowter), front and back, balanced gain stage, valve rectified, choke regulated power supply.   This design was started when I was asked for the “Best preamp you can make” So this is it. There are some test results available, but the real magic is only heard. It is something special even though I […]

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tn-preamp-2

Transformer coupled (Sowter), front and back, balanced gain stage, valve rectified, choke regulated power supply.

 

This design was started when I was asked for the “Best preamp you can make” So this is it. There are some test results available, but the real magic is only heard. It is something special even though I say so myself.

 

I fully intend to build another (if only for myself) and will probably use a torrid for the power supply which will allow the power unit to be in a matching 4U non ferrous enclosure.

 

As to the name, well, thats what its owner wanted, he may explain one day.

 

To replicate it will cost their new owner £2500, but I have not heard any other preamp that can do what this does.

 

Test results

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D3a Driven 2a3 http://www.longdogaudio.com/d3a-driven-2a3/ http://www.longdogaudio.com/d3a-driven-2a3/#respond Mon, 01 Dec 2014 18:38:24 +0000 http://www.longdogaudio.com/?p=294 The d3a is a great little high gm pentode to strap as a triode for use driving smaller DHT’s.   Its not got enough grunt for a 300b. But it sounds wonderfull driving 2a3 or 45 (and if I could afford them the British output DHT’s).   Valve rectifier and choke power supply. James output […]

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The d3a is a great little high gm pentode to strap as a triode for use driving smaller DHT’s.

 

Its not got enough grunt for a 300b. But it sounds wonderfull driving 2a3 or 45 (and if I could afford them the British output DHT’s).

 

  • Valve rectifier and choke power supply.
  • James output transformers.
  • CCS loaded d3a for linear operation.
  • Audio Note copper PIO coupling caps.

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Moving Coil Valve Phono Stage With Valve Regulated Supply http://www.longdogaudio.com/moving-coil-valve-phono-stage-valve-regulated-supply/ http://www.longdogaudio.com/moving-coil-valve-phono-stage-valve-regulated-supply/#respond Mon, 01 Dec 2014 18:37:28 +0000 http://www.longdogaudio.com/?p=292 Specifications   Overall gain 43dB at 1kHz Frequency response within 0.1dB of RIAA from 20Hz to 20kHz. All filter components hand matched to within 0.1% tolerance. Active loaded output driver provides low impedance, low distortion output to preamp or integrated amp Single stage high accuracy EQ provides stable imaging and wide soundstage. No feedback used […]

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83-phono-1tn

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Specifications

 

  • Overall gain 43dB at 1kHz
  • Frequency response within 0.1dB of RIAA from 20Hz to 20kHz.
  • All filter components hand matched to within 0.1% tolerance.
  • Active loaded output driver provides low impedance, low distortion output to preamp or integrated amp
  • Single stage high accuracy EQ provides stable imaging and wide soundstage.
  • No feedback used in signal path.
  • Valve complement 2 off ECC83/12AX7, 2 off 6072a.
  • Valve regulated power supply using 6EM7 Compactron dual triode for ultra low hum and noise.
  • Good quality components used througout. Takman carbon and metal resistors, ICW Clarity Cap SA capacitors.
  • Can be supplied with moving coil step up transformer installed eg Lundahl LL9226 or Sowter 9580.
  • Non-ferrous casework

 

The pictures show the first protype of the stage undergoing final check and testing before going to its new owner. The pictured model has relay switched dual inputs.

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Longdog Audio At Whittlebury http://www.longdogaudio.com/longdog-audio-whittlebury/ http://www.longdogaudio.com/longdog-audio-whittlebury/#respond Mon, 01 Dec 2014 18:34:18 +0000 http://www.longdogaudio.com/?p=290 The post Longdog Audio At Whittlebury appeared first on Longdog Audio.

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