The Dark Art of Audio Mastering

Picture of Alchemy Mastering Room 1

Founded in 1997, the World Famous Alchemy Mastering is one of the UK's leading audio mastering facilities. 

Located in an elegant West London mews, Alchemy’s mastering facility houses 3 studios designed by the Alchemists themselves. Each is equipped with a wide range of high end analogue and digital hardware and software processors, both vintage and cutting edge.

For more than 20 years Alchemy have been mastering hit mainstream and underground records across all genres, from Techno to Classical, Rock to Jazz.

Technical and creative Vinyl and Digital audio mastering

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The Alchemists

Barry “Bazza” Grint

Picture of Barry Grint, Mastering Engineer at Alchemy

Barry Grint. A mastering engineer since 1984, Barry founded Alchemy in 1998 having previously worked at Abbey Road, Porky’s Mastering, Tape One and the legendary Trident Studios. Barry has worked with many award winning artists including George Ezra's Double Platinum Staying At Tamara's, The Platinum single Shotgun, Tom Odell - Wrong Crowd and twice BRIT nominated Tom Walker - What A Time To Be Alive. Classic projects include: Madonna, Prince, Oasis, Bon Jovi, David Bowie, The Rolling Stones, The Beatles and Paul McCartney.


For all enquiries relating to Barry please contact or










Phil Kinrade

Picture of Phil Kinrade, Mastering Engineer at Alchemy

Phil Kinrade started working in 1978 in the studios of Dick James Music, before going on to set up Sound Basement offering mastering and duplication. In 1990 they merged with Chop Em Out where he worked until 2000 when he joined Alchemy as a director. Phil has worked with countless artists, including Elton John, Blondie, The Specials, Fun Lovin’ Criminals, & Donna Summer. In recent years Phil has specialised in catalogue and compilations, restoration and duplication.


For all enquiries relating to Phil please contact or






The Studios

Mastering One

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          Barry Grint's mastering studio for

          Digital, Analogue, and Vinyl.

          Including Half Speed cutting.

Mastering Two

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          Mastering studio for

          Digital, CD and Vinyl.

Mastering Three

Picture of Alchemy Mastering Three

          Phil Kinrade's mastering studio for

          restoration, Digital and CD.



At Alchemy we offer a boutique mastering service for digital and vinyl formats, as well as duplication and watermarking.

Our acoustically tuned rooms, all with full range monitor systems and natural daylight, give us the precision to refine the sound of your recordings to get you the sound you want to hear.

Alchemy is one of the world's leading experts in half speed and pure analogue vinyl mastering.

We offer a complete restoration service to recover audio and remaster from almost all defunct formats, plus an onsite tape baking facility to stabilise tapes that are shedding.

Alchemy is an approved Mastered For iTunes file author.



Should I choose an Attended or Unattended session?

Choose the kind of session that suits you best. We enjoy our clients sitting in on sessions, and frequently this can lead to better results due to the direct communication and ease of decision making that being in the same room together provides.

We do not charge a surcharge for attended sessions, although you may find that you have to wait slightly longer to get an attended booking.

If you aren’t able to, or do not wish to sit in on the session then we are very happy to take guidance and instructions from our clients as to how they would like their finished masters to sound.

Notes, reference tracks, thoughts and aspirations can all help us to fulfil our clients’ wishes more quickly and more accurately.

Communication between our engineers and our clients is the key to this success.

What File Format should I supply?

Digital source files should be supplied as WAVs or AIFFs. MP3s or AACs should not be used as source material, unless there is no other option.

Files should be rendered at the sample rate they were recorded at (no up or downsampling, regardless of the desired sample rate of the finished master). Preferred bit depth is 24 bit or 32 bit (fixed or float). Please note files rendered at 32 bit float can be subject to overs when re inserted into a different workstation due to the conversion from floating point to fixed point maths and back again.

Non interleaved (split left and right channels) are preferred to interleaved, although not all workstations offer this output as an option. If supplying non interleaved files please check that the files do re-combine into stereo correctly.

Please render with 1 or 2 bars of silence at the start and end of the recording, ensuring all reverb tails are allowed to fully ring out.

If providing stems please render all files from the same point in time, 1 or 2 bars before the start of the recording. Please ensure that all of the stems recombine to form the mix correctly when summed back together at unity gain. If you are using any buss processing please ensure that this does not change when you are printing stems.

We also accept Exabyte, DAT, Minidisc and 1630 Umatic tapes as digital source material, plus all analogue formats. 

What format will my master be delivered to me in?

As standard Alchemy will supply individual tracks as 44.1kHz / 24 bit interleaved stereo Broadcast WAV files, unless otherwise requested. Please note that if you wish to have higher resolution masters to request this prior to the start of your session, otherwise it may be that an additional pass is required and an additional charge levied. 

If ISRCs are supplied prior to the session these can be encoded into the BWAV metadata.

CD Masters will be supplied as DDP files as standard, either on a physical DVD disc or as an upload link. Where a physical copy has been supplied an audio CD ref for approval will be included with it. When uploaded the DDP will be supplied with software to play and test the CD master. It is the client's responsibility to check all aspects of the CD Master prior to manufacture, as any faults will be their own responsibility. If you encounter any problems, mistakes or have any questions about your CD master please contact your engineer immediately prior to proceeding with manufacturing.

Please note that we will default to encoding CD Text on a CD Master unless otherwise requested, if the required information has been provided on the booking form or in the form of complete label copy. All information will be cut and pasted so please ensure that all spellings and punctuation for CD Text are correct as supplied .

Vinyl masters will be supplied as lacquers, cut on one of our two modified Neumann VMS-80 vinyl mastering lathes.

Should I Dither when rendering my mixdown?

If you are supplying a 24 bit file for mastering then Alchemy recommends that 24 bit dither is applied when rendering your mix, as you move from the internal resolution of your DAW (which is most likely to be 32 bit floating point) to 24 bit. Although dither will be applied after mastering, and therefore is being applied twice to the recording, at 24 bit depth the dither will only measure at somewhere in the region of  -100 dBFS, and is therefore so quiet as to be inaudible in any practical sense. As a consequence there is no real discernable reason to not apply 24 bit dither.

If you are supplying a 32 bit floating point file for mastering then there is no need to apply dither.

How much Headroom should my mix have?

With a theoretical dynamic range of 122dB (at 24 bit resolution) there is no need to render your mixes with peaks at 0dbfs.

Mixes should peak at -3 to -6dbfs, to guard against intersample peak distortion.

Please note that if you are supplying a mix that has been limited there is no benefit in rendering out the limited version at -3 dbfs as no extra headroom has been created in dynamic terms.

Should I use any mix buss Processing?

In most instances Alchemy requests that mixes are supplied with no mix buss processing. However, we do understand that sometimes it can be an integral part of the sound of the record. So if mix buss processing has been applied, ideally please supply a version with and without and we can choose whichever version gets the best results.

If mix buss eq or compression has been applied notes as to what and why are very useful.

Please note that if limiting has been applied it can reduce the amount of options that the mastering engineer has to manipulate the sound of the recording.

If limited reference files have been created and used in the mix approval process then please also supply these also to the mastering engineer for reference purposes.

Would Mastering from stems be a benefit to my project?

Mastering from stems can cost more than mastering from a stereo mix down due to the additional time it takes to build the session and explore the additional possibilities it opens up. The benefit is that it can offer us more flexibility over the final balance of the mix that we are mastering.

So if for example we find the mastering process is reducing the amount of punch in a kick drum then we might choose to turn up the kick drum stem by a dB prior to the mastering processing chain.

If we find that the vocal has become too loud in the mastering process then we might turn the vocal stem down.

Mastering from stems can also be useful if there are elements in the mix that are unbalanced, so if for example the overall instrumentation in a mix is dull sounding, but the vocal is bright then we may adopt some different and specific processing on the vocal stem only.

Stems should ideally number 10 or less. An example of a stem set might be -


Synths and Guitars

FX, Noises and Atmospheres


Kick Drums

All other drums, cymbals and percussion

When creating the stem set please ensure that they are printed with all their corresponding effects, level rides and processes. When the stem set is combined it should create the exact sound of the complete mix, and so you should always A/B the stem set with the complete stereo mix down to ensure this.

If you have any dynamic mix buss processing it's important that this is side chained from the full mix when you are creating the stems, otherwise any mix buss dynamics processors that you are using will be getting the wrong trigger information and will therefore be applying the wrong dynamic changes. Render out a full stereo mix down and use this to trigger the side chains of your mix buss dynamic processors when you are rendering out the individual stems.

It's important to note that mastering from stems is not a substitute for doing a mix, the stems need to be created from a finished mix down - for reasons of cost and efficiency the mastering room may not be the best place to mix your record!

If you need mixing services we recommend you employ a dedicated mix engineer. If you would like us to suggest some names for you then we would be happy to do so.

How can I send you my mixes?

We are happy to download from any link provided by the client, or from their ftp server. Please ensure all transfers remain live until the day of the session, and are free from viruses and other malware. We may not be able to download anything in advance of the session, and if the link is expired then we cannot guarantee to be able to work on your record in the time that has been allotted. 

Clients may also send audio to Alchemy using our uplink service via these links:

Digital masters will be returned to the client via download link unless otherwise requested.

Can you check my mixes in advance of the session?

This may or may not be possible, depending on the availability of your chosen engineer. Please discuss with them directly.

It is worth noting that whilst some feedback prior to the session can be given, often its not possible for the mastering engineer to know the potential of any given mix until they have actually completed the mastering session and fully explored all possibilities. Generally much better feedback can be given after the session has been completed.

What If I want to tweak something once I have heard the master?

The price you pay Alchemy to master a track includes one free revision, so if having heard your master you feel that you would like to make a tweak then we would be happy to do so.

Please note that additional amendments after this first set of revisions may be subject to a recall charge.

If you wish to supply a new mix with some slight alterations for us to master again, then this may also be subject to a recall fee.

How many minutes can you cut on a side of vinyl before you lose quality?

As such the sound quality remains the same however loud we cut, although obviously the louder we cut the better the signal to noise ratio. This is one of the reasons for the misconception that sound quality diminishes the quieter the record is, as the level of the noise floor interacts more with the program material.

To cut longer sides there may also have to be some compromises in the sound of the recording, as stereo width and bass content can all take up more space on the disc. Therefore a longer side may have to have some low frequency or stereo width reduction in order to fit on the disc at the required loudness level.

As a rough guide we recommend the following approximate maximum running times for a loud and uncompromised cut (although please note that it is very program dependent and so every side is different) -

7" 45 rpm (SINGLE) - a running time of approximately 3'30" or less is optimal

7" 33 rpm (E.P.) - a running time of approximately 5'00" or less is optimal

10" 45 rpm (SINGLE) - a running time of approximately 6'00" or less is optimal

10" 33 rpm (E.P.) - a running time of approximately 9'00" or less is optimal

12" 45 rpm (SINGLE) - a running time of approximately 8'00" or less is optimal

12" 33 rpm (E.P.) - a running time of approximately 12'00" or less is optimal

12" 33 rpm (ALBUM) - a running time of approximately 24'00" or less is optimal


For each minute of running time over and above these approximate maximums you can expect to lose approximately 1 dB of loudness.

Please note that when we are cutting half speed we can get considerably more running time on a side, for more information please see our guide to Half Speed Vinyl Mastering. If your project has longer times than this then please CONTACT US to discuss and we can help to advise you on what we think are the best options for you.

Finally it is worth noting that high frequency can also influence how loud we can cut the record. The Neumann SX-74 cutter head, such as those we have at Alchemy, is so efficient that it can cut high frequency waveforms that are in excess of what some turntables and cartridges can reproduce, and in these instances the high frequency will sound distorted on playback. In these cases we would look to reduce the high frequency in the recording using equalisation and dynamic reduction processes. Even with these tools it is sometimes the case that the most elegant solution is to reduce the overall loudness of the cut in order to maintain a clean, smooth and open top end on the disc.

Can you cut Locked Grooves at Alchemy?

Yes we can. The success of the locked groove depends partly on the nature of the program material, with rhythmic patterns tending to loop more seamlessly than ambient patterns. This is because the rhythmic nature of the recording tends to better hide the sound the loop makes when it rejoins itself.

The length of a single revolution of the disc is unchanged regardless of where on the surface we cut the loop, so a revolution at 33.33 rpm is always 1800 ms long whether we cut it at the outside edge of the disc or towards the centre.

This means that a locked groove to be cut at 33.33 rpm should be exactly 1800 ms long. This equates to a 1 bar pattern at a bpm of 133.33 in a 4/4 time signature. Obviously the tempo would change for different time signatures.

The length of a revolution at 45 rpm is 1333 ms long, so a locked groove to be cut at 45 rpm should be 1333 ms in duration.

Please note that because we are unable to play master lacquers prior to them being sent to the factory (because playing the lacquer will damage the groove) we are unable to check a locked groove prior to manufacture. We will always perform test cuts in order to make sure the locked groove is a good as we can make it, but it is impossible to say exactly how good it is until you have received your Test Pressings. 

There is a small additional charge for each locked groove to be cut, please check with your engineer prior to your session about this.

Can you cut backwards (I.e. from the inside of the disc to the outside)?

This technique can only be done on a Scully lathe, where the lathe's lead screw can be removed and reinserted backwards.

At Alchemy we operate 2 highly modified Neumann VMS-80s and so are unable to offer this technique currently.

Can I take an Alchemy mastered WAV and get it cut to vinyl at the pressing plant?

Yes you can, but as the digital Mastered WAV will not have been fully optimised for vinyl, the resulting factory cut is unlikely to sound as good as a lacquer cut by us at Alchemy. In order to achieve the very highest sound quality, Masters must be optimised for both the destination format and for that specific release, whilst taking into account the equipment being used to create the master.

When we cut lacquers we will apply vinyl - specific mastering processing to optimise for that format. This is done in conjunction with a series of test cuts and playback on a number of different turntables, in order to establish the changes necessary to make the best sounding vinyl cut.

Frequently when cutting vinyl master lacquers we will make adjustments to the digital master recordings, and some of the processing that has been used to optimise the release for digital formats may be reduced or removed. Additionally processing may be introduced.

The amount that this and other elements need to be adjusted will vary depending on a number of factors including;

  • The cutting system that they are being cut on (the D/A converter, clocking, wiring, power supply, cutting amps, modifications, make and model of lathe and cutter head)

  • The speed of the cut

  • How loud the record is being cut

  • Where on the disc the track occurs (the frequency response and distortion characteristic varies from the outside to the inside of a record)

  • the make of blank lacquer

  • the make and model of cutting stylus used

For these reasons it isn’t possible to know what adjustments would need to be made without doing the test cuts that relate to that specific vinyl release, on the machine and in the studio in which the master is being cut.

Therefore it isn’t possible to provide a “vinyl master WAV“ that has been truly and fully optimised for vinyl. In addition to this, the cutting engineer at the factory may well repeat some or all of the adjustments, doubling up the processing and further reducing the sound quality of the vinyl cut.

We will of course where asked provide digital source material to be cut to vinyl elsewhere, prepared as best we can whilst taking into account all of the above.

It is also worth considering how the factory is going to cut the master: a vinyl master will always be either a lacquer or copper disc. The majority of in-factory cuts are done on a DMM cutting lathe cutting directly onto copper discs. This eliminates a metalwork stage and so is cheaper and easier for the factory. However it is generally felt that sonically copper cuts can lack the overall loudness, mid range warmth, stereo and bass content of a lacquer cut.

For this reason the vast majority of independent cutting rooms such as Alchemy will solely or predominantly have lacquer cutting systems and not DMM systems.

Finally it should also be noted that as the mastering engineers who have spent a great deal of time mastering the material, we are better placed to cut the vinyl masters for a project because of this in-depth knowledge of the recorded material. So an Alchemy vinyl cut is likely to exhibit far fewer problems such as sibilant distortion or high frequency distortion, as well as almost certainly sounding better overall due to the superiority of our heavily modified vinyl cutting systems.

How do I check a test pressing?

TPs should be checked for audio content, tracking performance, sound quality and noise. If you have any questions or doubts please contact your engineer to discuss. Please note we will need a copy of any TP that you wish us to assess; a digital transcription is not sufficient as we will need to evaluate not just by playing the record but also visually using test microscopes. At Alchemy we have 6 different playback systems, ranging from Hi Fi to DJ type decks, to give us a broad cross-section of feedback when checking records.

Audio content - are the correct tracks in the correct order, with the correct fades and spacing between them?

Trackability - does the record play without skipping on a number of different playback systems?

Sound Quality - does the record sound good, and does it sound how you expected it to sound?

Noise - how quiet are the blank sections of the record such as the spirals, run in and run out grooves? How loud and frequent are the clicks and pops throughout the record, and how loud is the general noise floor relative to the program material?

I can't fill out all of the information on the booking form, what should I do?

Please fill in what you can and return to us. If you don't know the answer to any of the questions then it may be that they aren't relevant to your particular session. If there is any information that is missing that we require we will ask you for it.

Please note the second page requests CD text and ISRC information. We can encode ISRCs into Broadcast WAV files as per the EBU specification co-authored by Alchemy's Barry Grint. CD Text information can only be encoded into CD Masters, and so only needs to completed if you are requesting a CD master from us.

Where do I get an ISRC from?

Alchemy do not create or supply ISRCs, but if you have them we are able to encode them into the metadata of Broadcast WAV files, or CD Masters.

More information on ISRCs can be found in these links below - 


ISRC Wikipedia Page

The EBU technical specification for ISRC in BWAV




What is M F i T (Mastered for iTunes)?

Mastered For iTunes (MFiT) is Apple's premium AAC product that can be sold alongside their standard AAC product.

MFiT masters can differ from standard digital masters - Apple have provided tools that allow us to assess how the sound will change after the encode / decode process, and so the sound of the master can be altered to accommodate this change.

We can also check to see if the resulting AAC will clip after the encode / decode process, and reduce the peak level accordingly. This means that MFiT releases can distort less when listened to by the consumer.

Apple will accept higher resolution masters for MFiT (up to 192kHz / 24 bit), although all incoming masters are sample rate converted to 44.1kHz.

Mastered For iTunes



When I put my CD in the computer the Artist and Track titles don't appear, why?

That information comes from the Gracenote CDDB database, so will only show up if Gracenote has the information and the computer is connected to the internet.

It is not stored on the CD itself.





Mix tips and general good practice

Reference your mix on multiple playback systems

No audio replay system is perfect, and the idiosyncrasies of the mixdown environment may well find their way into the sonics of the mix.

For example mixes created in a monitoring environment that is very bright may be lacking in high frequency.

If the client’s monitoring environment isn’t optimal then it may be worth referencing the mixdown in a number of different listening environments.

Reference other recordings

It is useful to collect recordings by other artists that you feel are good sonic examples to use as reference points.

When A/B-ing a mix with other commercially released recordings you may need to level match the 2 recordings by turning down the commercially released recording.

There are now a number of good software plug ins that provide a degree of automatic level matching between different audio files, which can help you A/B an unmastered mixdown with a commercially released recording. iTunes has a feature called SoundCheck which when activated will also provide some automatic level matching and can be useful in this regard also.

If you have a previous mix of your own which sounds particularly good, and which was particularly successful once mastered, then this would also provide a good reference point for future mixdowns.

Listen at multiple speaker volumes

Listening quietly can often reveal more about the relative loudness balances of different instruments within a mix.

Listening loud can be enjoyable, and a good way to check the power and impact of a recording. However, exposure to loud audio over time can cause fatigue and alter your understanding of high frequencies. Prolonged loud listening can cause temporary or permanent hearing damage.

Get the mix to sound as close as possible to how you want it to sound

This may seem like stating the obvious, but try and make sure the mix sounds how you would like, don't assume that there are elements within it that will be fixed in mastering.

When mastering a record we obviously try and get it to sound as good as we can to our ears, whilst taking into account how the client’s own aspirations.

The mix that we are supplied with will provide us with a benchmark as to how you like things to sound, for example if a mix has a very loud vocal in it we would normally make the assumption that the you wanted the vocal to be very loud in the finished master. So it is helpful if the mix sounds as good as you think it can.

If this is not the case then notes as to what your are unhappy about the mix are useful.

The fewer problems there are to fix in the mix the better the final master will sound; whilst we are adept at minimising weaknesses in a mix it is generally the case that it is more difficult to totally eliminate flaws at the mastering stage than at the mix stage.

If the client is unsure about particular elements within a mix then stem mastering should be considered and discussed in advance with an alchemy engineer.

Phase & mono

Mixes should be checked for mono compatibility; when listening in mono does the mix still stand up, or does it lose top, or have other frequencies that cancel out? Are the key elements still clearly audible, and how has their relationship to each other changed?

Many online streams, radio stations and club sound systems are mono, or predominantly mono, as well as many laptop and mobile phone speakers. So it may be that a mix that suffers when mono’d needs more work.

If the recording is destined for vinyl as a release format there are other phase considerations that may need to be checked, please see the following point -

Vinyl specific issues

Recording to vinyl is different to recording to any other medium, and as such there are some sonic elements which work well when recorded to vinyl, and some which work less well.

In general it is sensible to avoid any stereo width in the low frequencies, and also to avoid any elements that are totally out of phase. Extreme High Frequency, Stereo Width, Vocal Sibilance or Low Frequency can limit the overall loudness of the cut, due to the possibilities of distortion on playback, jumps or mistracking on playback, or excessive depth modulation within the groove itself.

Distortion in a recording will almost certainly increase if transferred to vinyl.


Contact Us

A: 10 Barb Mews, London, W6 7PA
T: +44 (020) 7348 0010


Hammersmith – Circle Line, District Line, Hammersmith & City Line, Piccadilly Line Shepherd’s Bush - Central Line


Shepherds Bush or Kensington Olympia.

By Car

On street metered parking is available directly outside the studio.

Practising the dark arts since 1998