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Yosemite Preamplifier
$20,000.00
Our first tube preamplifier build began as many ampsandsound products do, inspired by icons. In this case, legendary line-phono units like the C22 and Marantz Model 7 guided the basic approach to the circuit. Many of these units provide controls largely abandoned by the modern audiophile - tone controls for example. These add not only additional parts, but require additional feedback to compensate for their effects, a design compromise that runs counter to our ethos.
In the style of rebuilds of tape heads as linestages, we removed these tone controls and separate out the power supplies for phono and line - there are completely separate power transformers and supplies for these two stages, something almost never seen in a unit of this type. Next we applied our attention to detail in build quality, a 200% overspecified toroidal transformer, premium 33-step attenuator volume control, high quality coupling caps, custom nickel-core step up transformers for the moving-coil input, a new custom input transformer for XLR conversion, tube rectification and application of our 10-gauge steel plate chassis, turret-board construction and fanatical attention to wiring.
All of those details are what you would expect from ampsandsound, but we also broke new ground in the design of the chassis, taking cues from 1940’s and 50’s industrial audio equipment and crafting a modular design with several distinct advantages. This new mechanical platform allows for a greater ease of repair for a complex product with multiple power supplies, and also allows for isolation between the various power supplies, volume controls and sensitive line and phono stages. It also makes room for a heavy duty, functional tube cage. The goal of permanent install industrial electronics has always been functionality and bulletproof stability. An easy demonstration of this is the Yosemite input jacks which are all panel mount, increasing reliability and ease of service. It is our aim that in 40 years a simple and easily accomplished servicing will provide an additional 40 years of service.
All of these improvements add up to one of the finest pieces we’ve ever built, and an impressive performer. The Yosemite achieves an astonishing noise figure of 23uV at -100dB, a figure which is almost unheard of for tube gear, and competes even with some solid state equipment. This is even more special when you consider that there are zero PCBs or silicone in the linestage.
Aside from excellent measurements, ampsandsound’s goal is for Yosemite to satisfy those absolute purists who must have a completely mechanical and analog device. We are never attempting to hit a sculpted sonic profile in this process and refrain from adding anything nonessential or extra, so that we may focus on the purest, simplest and best sounding path. Yosemite represents a much less colored linestage than you may expect from an old-school traditionally built pre, opting instead for wide bandwidth, depth, refinement and richness over syrupy or dark presentations. With this linestage it is our hope that you can have your cake and eat it too.
Some of the interesting points include:
The Line and the Phono are modeled/inspired by the Marantz 7.
The line and the phono each are completely separate, having their own power transformer, choke and power supplies.
The pre is completely wired via turret boards in a manner we call mission critical.
The pre was designed to be modular, All power transformers are under their own isolated cover are to reduce EMI/RFI bleed out.
The front head unit houses the volume control and input selector.
The rear tail section houses panel mount versions of the I/O.
The front and rear have internal access panels to inspect and service the volume control or I/O without tearing down the whole pre.
The nature of this pre was to give all the sonic dividends of the Marantz 7 but in a more robust/serviceable package. Though heavy, its meant to be lab grade… as such, failures should be very uncommon and fixing them straight forward.
The phono sec is a modest gain of 40 but is intended to make use of the SUTs.
- Specs:
- 120V or 230v configurable.
- 2 Single Ended (RCA) line level inputs
- 1 XLR Balanced line level input
- Input impedance of Single Ended inputs is 50K
- Input impedance of XLR input is 600ohms
- MM input impedance is 47Kohms
- MC input impedance is 50ohm
- Output impedance is 2Kohm
- Line level gain is 10 - 12AU7s for gain and driver
- Phone section gain (all tube) before MC SUTS is 40 - 12AX7s for gain and 12AU7 driver
- Included SUTS are 1:9, 1:18
- THD+N = 0.0110%
- THD =0.0021%
- Noise 13.04uVrms
- Tube compliment for Phono:
- 12AX7 left and 12AX7 right are used for gain.
- The centered 12AT7 is the Driver
- Tube compliment for Line:
- 12AU7 left and 12AU7 right are used for gain.
- The centered 12AU7 is the Driver
Balanced to Single ended conversion done with custom Cinemag input transformers.