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Boulder Model 508 phono preamplifier

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.


I have had a fair amount of experience with Boulder gear and I have always enjoyed its neutral presentation. Boulder gear does not colour the sound but strives to present what it is given with great presence and dynamics. Resolution is very clear. I opted to begin with the 1970 Polydor live album of Joe Cocker’s Mad Dogs and Englishmen. ‘Feelin’ Alright’ has always offered great energy and power right off the vinyl and the 508 acquitted itself as expected. The sound was visceral and very organic. The horn section was brassy and powerful. This is a large band and choir and the soundstage reflected the expansive scale of the production. Joe Cocker is one performer I never had the chance to see live and the 508 delivered an electric performance off of this very well engineered album that is likely as close I will ever get to being there under the circumstances.

One ‘audiophile’ album I have always enjoyed is Shelby Lynn’s Just a Little Lovin’[UMG] It is a wonderful thing when a recording can capture the space of the room, and the title track is an excellent example of this. The 508 brings the space to life with terrifically accurate decay on the drumstick on the snare drum rim. The sound of this snap moves around the room and is gone just as the next snap occurs. The upright bass brings another example of the terrific organic feel as hand meets string and wood. Shelby’s lost and forlorn vocals carry great emotion as regret and loss flow through her to the listener. Once again that sense of dimensionality is so pervasive. You can ‘see’ the room, which is a real testament to the purity of the signal being sent by the 508. 

Gerry Rafferty’s City to City [United Artists Group] is a soundtrack of your life record that I have enjoyed for forty-two years. It is not so much a collection of ten songs as a two-sided bounty of memories. Playing ‘Baker Street’ and ‘Right Down the Line’ back to back brought back the summer of 1977 in clear definition. This was perhaps the finest rendition of these songs I have heard on this original vinyl release through any stereo system. The signature saxophone on ‘Baker street’ had soul and swing alongside the rasp of the reed as the song queued up visions of lonely early morning streets after a summer rain. Images of lives in twilight come to the fore in this poignant song. When a piece of gear can put you inside the music, that is the goal and the fulfilment of listening. The 508 with its simplified yet refined and sophisticated design delivers the goods with aplomb.

I have a first-class phono stage – the well regarded Simaudio Moon 610LP – and it is, in a word, superb. It also offers a ton of loading settings and short signal paths that I can use for a myriad of cartridge reviews. Consequently, I am very pleased with what I have. However, the 508 gave me pause. If I were simply enjoying my system without new gear rotating in and out, I would be more than tempted to make a switch. The 508 is that special. It is, in the world of Boulder products,  an actually affordable device. A four-figure bargain designed by one of the world’s leading aspirational brands. No corners were cut, and yet signal paths were shortened, and circuits were refined. The result is a unit I will unequivocally recommend. Take time and give it a listen. You may very well keep it.


Inputs: 1 pair, via 3-pin XLR

Outputs: 1 pair, via 3-pin XLR

Input Impedance, Maximum MC: 100 ohms, MM: 47k ohms

Output Impedance: 100 ohms, balanced

1 kHz Gain, RIAA MC: 70 dB, MM: 44 dB

Frequency Response: RIAA ±0.5 dB, 20 Hz to 20 kHz

Distortion: THD 0.01%

Noise (EIN): MC 116 nanovolts flat, 20 Hz to 20 kHz

Maximum Output Level: 16 Vrms

Power Requirements: 100, 120, 200, 240 VAC, 50–60Hz

Power Consumption: 15W Maximum

Dimensions: 29.2 cm W ×24.1 cm D ×5.8 cm H

Weight: 5.2 kg)

Price: £6,150

Manufactured by: Boulder Amplifiers Inc.


Distributed in the UK by: Padood


Tel: +44(0)1223 653199


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