I work primarily in two fields: valve amplification and digital. Having studied much circuit topology of the world’s finest valve amplifiers, I reached the conclusion that there are not that many differences in topology but the crucial differences are in the design and sophistication of the power supplies. Over the last year I have pioneered upgrading the power supplies of common amplifiers with particular emphasis on the driver and input stages. I also specialize in upgrading key power supply and signal path components to improve performance over the original designs. I am at the stage now where I can honestly claim to be able to improve virtually any amplifier out there.
The closest mainstream commercial operation I know that appears to do similar work is Border Patrol, whose amplifiers have a world class reputation and cost many thousands of pounds. I believe I can offer similar levels of performance at a much lower cost.
With digital the story is similar. There are some quite different designs around for example non oversampling and oversampling Dac solutions, but the key to good digital sound out of any design is a well sorted high capacity power supply and a decent output stage. Whilst I believe valve output stages often offer excellent sonic results, other solutions are possible depending on the Dac chip, with ‘direct’ output, Class A solid state output stages, and upgraded op amps among the options.
When I receive your amplifier or other equipment I write a report giving my recommendations and a fixed cost for the work. Recommendations are graded in priority, so you will have a clear plan of how much you need to spend to get the biggest bang per buck. Should any other work emerge during dismantling or testing I will of course quote for this before completion.
Needless to say any regular servicing will be included within my recommendations. Some of the equipment I work on was built by me originally. But whether originally made by me or not, the vast majority of my business is repeat.
My system comprises my own custom built 300b Stereo Push pull zero negative feedback amplifier which uses battery bias and has separate choke filters for the input and driver stages. It also has several Black Gate power supply and cathode bypass capacitors and Mundorf film /foil coupling capacitors.
This is fed by a modified Blue Velvet preamp, which I’ve modded to split and decouple the power supply rail. This has a shunt attenuator, which is remote controlled.
My source is J River MC20 running on a Mac Mini and converted by a self built DDDac NOS Dac. Speakers are self-built Wilmslow Audio Prestige cabinets but using Vifa tweeters, Monacor 12ins bass units and the famous ATC mid range unit used in many high end speakers.
I now have augmented my system with two Mastersound 845 Final Monoblocks.
All of the mods and upgrades I do are thoroughly tested in my own equipment before being rolled out for clients.
I am driven by a passion for achieving the best possible standards of musical reproduction and my goal is to make any equipment perform as best it can within your budget, and in many cases to try and make it perform better than my own equipment before retrofitting the same mods to my own system.
Whilst I don’t have a vinyl front end anymore, I have previously owned Rega and Linn turntables, culminating in a Linn Sondek, Ittok and Audio Technica moving coil cartridge. Space in a small London house precluded keeping vinyl and CDs but I love the vinyl sound and to some extent try to create a non aggressive natural digital sound to match a good vinyl rig. You are very welcome to listen to my system and of course compare it to your own equipment before and after modification.
So How Much Does This Cost?
Upgrading some key power supply and signal path components can cost around £100, while a major overhaul and reconfiguration of power supplies might be a few hundred. It’s best to e mail with your thoughts first off, then I can give you a good idea before sending /bringing equipment for a firm quote. Even heavy valve amplifiers can be sent around the UK for around £15 by courier these days-and that was with a separate box for the valves too!
Terms of business are 50% payment up front, at which point I will order any necessary parts, with the final 50% payable on completion.
Some Recent or Completed Projects
1. Valve Amplifiers
Built KT88 and EL34 stereo valve amps
Built 300b Monoblocs
Built 300b stereo valve amp with interstage transformer
Built Cathode follower, Aikido and other valve pre amps
Upgrade of top of range Ming Da pre including shunt pot and key signal path components
Upgrade of 300b stereo amp with battery bias, coupling capacitors, and key signal resistors
Upgrade of 300b monoblocs with battery bias and key signal components
Installation of own design psu upgrades to Cathode Follower pre + upgrade of key signal components
Upgrade of 300b amp with new choke psu, battery bias and signal resistors
Upgrading power supply of Amphion 6C33 Monoblocs, plus upgraded key signal components
Upgrade and servicing of Amplifon 6C33 push pull amplifier
Upgrade of Cathode follower Pre amp with split psu rail, shunt pot mod etc
Rebuild of 2E22 Chinese SE amp with upgraded power supplies, Western components, Hammond output transformers etc
- Valve /Solid State Hybrids
Upgrade of ARC SP9 pre including addition of choke regulated power supply
- Digital /Dacs
Conversion of 5 CD players using TDA 1541 chips to NOS output, with different designs of output stage from capacitor direct, transformers and valve output stages
Conversion of I Pod to high quality digital source
Built custom Dac with valve output and masterclock synched to custom transport
Building of 5 DDDacs
Upgrading of power supplies on around 10 CD players
Installation of remote control facility on 6 amplifiers and preamps.
Construction of 3 T amps
- Audio Myths
In our hobby and /or profession there are more myths and pseudoscience than in most other areas you can name. A few examples of these are:
- If you can’t measure it you can’t hear it
There is a certain sense to this, but of course it depends what and how you measure the particular dimension. Much of the sound quality improvement reaped from better power supplies is because you are removing the dynamic modulation by the output stage of the input and driver stage power supply. If you simply measure a constant sine wave distortion figure at the output the distortion figure will be low, as there is a constant signal and the power supply modulation will be minimal. In real, dynamic conditions distortion of one sort or another will be much higher and whilst you can’t measure this directly, you can clearly pick up the power supply modulation on an oscilloscope.
- Cables don’t make any difference
This is clearly nonsense for the measurement brigade or those who only use their ears. Cables have different resistance, capacitance and inductance which are all measurable and different constructions and lengths may have an effect on the signal. At an extreme end, some solid state amps will oscillate when used with high inductance lengthy cables. Eg Naim state very strongly you should only use their cables for this reason. As a generalization most valve amps are very tolerant of speaker cables.There is a further issue with stranded cable. Over the course of a few years this can gradually oxidise where air can permeate the conductors and cause a diode effect which can be audible. The answer is to use single insulated conductors or to swap over cheap multi strand cables every few years. For a cheap high performance single insulated conductor design look no further than Category 5 (Cat 5) computer networking cable.So, I certainly don’t recommend spending a fortune on top end cables but do give some thought to cable lengths and types for your system.
- There is no point using ‘boutique’ expensive components, they all sound the same
The most important consideration is the overall circuit topology and power supply design. That said, ‘boutique’ components used judiciously can improve overall sound quality. Good examples of this are: upgrading grid input /stopper resistors, using film /foil caps instead of metallised film in the signal path, non inductive resistors instead of inductive ones, or diodes with better performance.
- You have to spend a fortune on NOS valves to get the best sound
There is some truth in this as you can certainly get great sound from NOS tubes. However, there is often some great sounding modern alternatives available. These may be current production or they may be recent Russian military tubes for example. They often go for a fraction of the NOS tube’s price as well.
David 110814 AD Audio Consultants firstname.lastname@example.org