[Listening test] Bottlehead Moreplay - vacuum tube preamplifier

Bottlehead Moreplay

Tubed preamplifier DIY kit

Product: Bottlehead Moreplay - vacuum tube preamplifier
Manufacturer: Bottlehead - USA
Recommended Retail Price: $495 USD as of December, 2022
Reviewer: Greg Johnson - TNT USA
Reviewed: February, 2023

Background

The Moreplay is the successor to Bottlehead's Foreplay series, which went through three iterations. The Moreplay is unique in having only one gain stage, a triode-wired 6V6, with zero feedback. The volume control is also after the gainstage rather than before it, to mitigate the typical noise-gain correlation. General specifications are pedestrian and probably conservative, but are consistent for a zero feedback triode gainstage using a power tube: a sensible 9dB of gain, less than 1% distortion at 1V, output impedance < 3.2 kOhms at all levels, and a 65-80dB SNR at 1Vrms, the latter of which seems very conservative since my Moreplay is by far the quietest preamp I've ever owned. The low noise is a design goal since Bottlehead amplification is designed for use with SET (Single Ended Triode) amps and high efficiency speakers. A pair of NOS (New Old Stock) Russian 6V6GT tubes come with the kit. The stock parts are decent industrial quality but merely "OK" (more on that later). While I've built many kits and done a lot of modding over the years, I bought the Moreplay fully built in 100% stock form from a fellow audiophile.

Sound Quality In Stock Form

The assessment of sound quality is based on a comparison to my Conrad Johnson PF-1L. The Moreplay in stock form, including tubes, I found mostly comparable to the PF-1L. There did seem to be a sense of hardness or nervousness to the Moreplay that the PF-1L did not exhibit, however. The Moreplay is more forward and energetic sounding.

Upgrades

If anyone is contemplating building a kit component, I highly recommend it. Building and upgrading allows you to "peer behind the veil" regarding the impact of passive components (although be warned, modding gear does detract from resale value). The Moreplay proved to be the most sensitive component I've modified, presumably because a preamplifier circuit has the the critical task of amplifying a low level voltage and the Moreplay circuit is so simple and "pure". In sequence I upgrading the following:

Output Tubes: not surprisingly considering the minimalism of its circuit, the Moreplay is very sensitive to output tubes. What's nice about the Moreplay is that NOS 6V6 tubes are still (relatively) inexpensive compared to just about all other common NOS tubes. Better still, 6K6G and 6K6GT tubes can be used, and these are fairly plentiful, very inexpensive and sound just as good as the 6V6 in my opinion. I've settled on 1940s-1950s vintage RCA 6K6GT.
Output (DC blocking) capacitor: upgrading these proved to be relatively modest in impact but worthwhile, which correlates with previous experience upgrading these on both a solid state preamplifier (Acurus LS-11) and a couple of MHDT NOS DACs. I tried several caps here (Mundorf Supreme, Jupiter HT, Jantzen Superior, Obbligato Ultra Premium and Claritycap CMR). I found the Claritycap CMR to sound the best here. I'm probably still going to try Solen SE series tin foil caps as well. To be safe, note that these caps must be rated at 400V minimum rather than the 250V specified in the manual since turn on surge approaches 400V according to Bottlehead.
Resistors in circuit path: upgrading these I believe provided the most significant improvement. Stock resistors were industrial grade carbon films, which are also magnetic. I replaced these with (non magnetic) Takman REX carbon films (either the same wattage or one step up), with the critical grid stopper upgraded first to a REX then to Shinkoh Tantalum I had from a previous project. If the quality of the carbon film in industrial resistors and audio grade resistors is equivalent (likely the case), then the improvement is purely from eliminating magnetic components from the signal path. I had a similar experience once with a 300B SET I owned at the time in replacing Audio Note magnetic tantalum resistors with Takman REX, which, theoretically, should have been a "downgrade".
Plate Load Resistor: replacing this industrial grade wire wound component with a Mills wire wound proved beneficial, again under the assumption of eliminating a magnetic component from the signal path
Cathode bypass capacitor and resistor: these are in parallel and upgrading this capacitor (which is an electrolytic) proved significant. I found the Nichicon Fine Gold to sound best and preferable to an Elna Silmic II, Audio Note Kaisei, and two other Nichicon audio-grade electrolytics. The improvement made by replacing this resistor with a Takman REX was subtle.

After my upgrades, comparing the Moreplay to the PF-1L finds them much more distinctly different. The PF-1L is still smooth and pleasant. The Moreplay after upgrades has overcome virtually all of its stock hardness or nervousness and is about as smooth and pleasant as the PF-1L. It's also more energetic, open, transparent, resolving, and "colorful" than the PF-1L. The Moreplay reveals the PF-1L as laidback, pleasantly veiled and slightly grey tonally. A good way to summarize the differences is this: the PF-1L enables me to be a spectator to the music whereas the Moreplay forces engagement and attention. Because I sometimes just want to relax with music, the Moreplay isn't altogether superior to the PF-1L from the standpoint of pure musicality.

Conclusion

Because I had become burned out on the DIY aspect of the hobby, I hadn't built or modified any components in a couple of years. By virtue of how easy it is to upgrade (for example, the top plate, by which everything is attached, lifts right off), and the sensitivity it exhibits to component changes, the Moreplay has rekindled my interest in DIY. This is my first Bottlehead component. One may find the form factor (which makes shelf installation challenging) and point-to-point wiring a concern. These admittedly kept me away from Bottlehead for a long time and now I regret it. The Moreplay looks great in person and I find point to point very easy to work with. One can also use 90 degree connectors or 90 degree adaptors for RCA cables and the AC cables to overcome form factor concerns (although I found 90-degree adaptors to add a bit of hardness to the sound).

High Points

Organic yet resolving - ridiculously good sound quality for the money, esp. with tube rolling and select passive component mods
Unique form factor
Ease of modification

Potential Issues

Unique form factor
High output impedance means matching with the minority of amplifiers problematic
Pedestrian / adequate stock parts

Review System

Seas A26 loudspeakers (custom braced baltic birch cabinets & Skylan speaker stands)
VTV Hypex NCore NC252MP amplifier
Conrad Johnson PF10L preamplifier
Lumin U1 Mini server
Michael Yee Audio DA-1 DAC
Uptone Audio Ether-Regen
Quadraspire Q4 Evo equipment rack

DISCLAIMER. TNT-Audio is a 100% independent magazine that neither accepts advertising from companies nor requires readers to register or pay for subscriptions. If you wish, you can support our independent reviews via a PayPal donation. After publication of reviews, the authors do not retain samples other than on long-term loan for further evaluation or comparison with later-received gear. Hence, all contents are written free of any “editorial” or “advertising” influence, and all reviews in this publication, positive or negative, reflect the independent opinions of their respective authors. TNT-Audio will publish all manufacturer responses, subject to the reviewer's right to reply in turn.