Boulder Model 508 phono preamplifier

Boulder Amplifiers Model 508
Boulder Model 508 phono preamplifier

Boulder Amplifiers, Inc. of Boulder Colorado, USA has established, over its nearly thirty-five years, a history of truly mountaintop performance. Designs can be on the market for over a decade as their individual excellence may take years to surpass. I was able to personally witness the exceptional build quality of Boulder’s designs when I toured their factory in October of 2018. The new facility they had built and moved into in 2016 was state of the art and housed all of the build processes for their lineup. During the tour I saw the mighty 161kg Model 3050 Monoblock amplifier being built while held by an engine block lift! Huge and technically imposing it was all of the six-figure price tag. So, what did my post tour goodie bag have in it from my trip to Boulder? In fact, it was their newest piece the 5.2kg Model 508 Phono preamplifier. The first in the new ‘affordable’ 500 line. Yes, it is the smallest and least expensive (£6,150) piece in the Boulder Amplifiers, Inc. arsenal. However, being the youngest and smallest does not make it any less a Boulder Amplifier product.

Building impressive and technically proficient gear is de rigueur for these Colorado audio scions. The build quality of the new 508 was no exception following in the footsteps of its larger brethren. Milled from a solid billet of 6061-T6 aluminium on their in-house CNC machines it comes to life with as much detail and precision as any other Boulder model. I spoke with the staff member responsible for the sanding of the casework after CNC work was completed. He was very proud to be a part of the team working on such high-quality gear. This was consistent throughout my tour. There was much pride of workmanship in the Boulder team. 

The design concept for the 508 was to reduce as much complexity as possible. They were striving to reduce the circuit to as direct a signal path as they could manage. Seeing the Boulder team assemble the densely packed surface mount board I was impressed with how little space each section took up and how precisely the board was arranged. It was also interesting to see the separate section inside the case for the power supply to remove any spurious power from influencing the audio signal regardless of the power input. The 508 can operate efficiently with 100V to 240V.

Once I returned home, installing the 508 in my system was very simple. The front of the case offers an on/off toggle switch and a mute button. On the rear you have a standard IEC power plug (in the USA) next to a fuse and a pair of balanced outputs and inputs with the MC/MM toggle and the ground screw next to the balanced inputs. A single white LED on the front indicates the unit is on. For most of us with a typical unbalanced turntable output Boulder supplies a pair of unbalanced RCA to balanced XLR cables to complete the connection. The 508 converts the unbalanced signal to balanced and operates in balanced the rest of the way. I experienced no issues with this and was thankful for the included adapters to hook up my VPI Prime Signature table to the 508 and then run balanced cables to my PS Audio BHK preamp.

Many top-flight phono stages have a wide range of settings to allow for the use of many cartridge types. The 508 goes for the middle offering the standard 47k Ohms for Moving Magnet and 100 Ohms for Moving coil to pair up with an active two-stage RIAA filter. The only setting selection is that small toggle switch on the rear to select between them. While this may eliminate some very low voltage moving coil cartridges initially, there are plenty of high-quality Step-Up transformers that could assist should your Ortofon Windfeld Ti Moving Coil’s 0.2mV need a bit of a boost. (Bob’s Devices comes to mind). My Ortofon Cadenza Bronze Moving Coil at 0.4mV performed flawlessly with the 508.

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