Audio Amplifiers - Daniel Royce

AUDIO AMPS Designs

Enki 25

State of the art, modern class A amplifier, employing HexFet output transistors from ON Semiconductors (formerly Fairchild).
As a true A class amp, it runs very hot. Each channel is dissipating 90W of power, while delivering up to 25W of output power, at 6 Ohm load (speakers). Whole unit draws over 200W of power, even when idle. Employs two, 92mm, temperature controlled Noctua fans, that run quietly, below 19 dB to cool the amp.
Aluminum chassis with big heatsinks weights over 3 pounds. PSU, as with all our amps, is housed separately, and consists of two, 230W each, high quality SMPS units sourced from Hewlett Packard.

Nabu 80

The most sophisticated amp so far. Current dumping concept has been patented by legendary Quad HiFi. Once patent has expired, we did not hesitate to built thoroughly modern amp taking advantage of this concept. It basically works like having A class amp for lower wattage, say up to 2 Watts, and B class amp for higher levels. This delivers lowest distortion and optimal thermal performance.

It's cool running, self-adjusting amp, which thanks to two JFET op-amps handling the input and voltage gain stage, delivers lowest distortion we've ever seen in any real-life amp: 0.0004% in wide frequency bandwith, at max power; and highest slew rate: 40V/µs. This unit is powered by BJT transistors in undestructible TO-3 package.

Buzur 80

Circlophone topology, with its bias current controlled dynamically in real time by a servo, has been pioneered by an engineer from Belgium, 10 years ago. As a concept - it's extremely versatile, and can be made to work with any kind of output tranasistors: BJTs, HexFets and LatFets. It's a hot class B amp, and by hot, we mean HOT. Dissipating approx 20W when idle, delivers stellar performance. All our amps, except 'Nabu' which employs op-amps, are made solely with dicrete components - for more traditional listeners. This one is the most complex discrete amp, mostly due to bias servo implementation. As usual - PSU is housed seprately, and it can be implemented as linear PSU (with 400W toroidal transformer), or with SMPS - which is of course much smaller and lighter. This design has never been sold as a commercial product - due to its complexity and cost - it was only built, so far, by a handful of DIY audiophiles.

Dumuz 80 Quasi

Rock solid, old school amp, rooted in the early 80s, when HiFi moniker really meant HiFi. Back in that time, due to lack of high power PNP transistors, only NPN devices had been used. Never the less, it performs great, and is relatively simple to tune. Unbreakable, solid design that will never fail. These days it's virtually impossible to find modern amps/receivers still built as Quasi amps - but here we are! Thoruoghly modernized and built with NMOS HexFet transistors from OnSemi, and with THD still well below 0.1% at full power, will stand up to any other amp.

Kasad 160

The only amp in our catalogue, that implements two pairs of output transistors - for extra power. And these transistors - legendary, pioneered by Hitachi and designed exclusively for audio Lateral Fets. The most expensive transistors out there; bar none. Rarely used in commercial amps these days due to price, and availabilty. There is only one company - Exicon in UK - still making them. Relatively simple, but robust and high quality design. Built for power. Implementing output stage with two pairs of transistors has pros and cons. Obviusly it gives more power, and also - in theory - it improves certain specs. The only problem is that both pairs have to be identical (matching). In real life it's a challenge to correctly match them. From our experience it only make sense with LatFets. That's why all our amps (except this one) employ single pair. As Bill Gates famously said: 80W of continuous power should be enough for everyone, but in case more is needed, 160W should really suffice :)

Dumuz 80 Quasi - Woody

Electronically - the same as Dumuz 80 Quasi - but enclosed in a replica of vintage wooden (American Oak) box that looks like 'Klipsh Capitol 4' amp from the 50s.

Due to its small size, it comes with SMPS PSU only, and - unlike our other amps - it's one integrated unit (amp + PSU in one enclosure).

AUDIO AMPS Features and Customization

Chassis

Each amp's circuits are mounted atop of heavy aluminum chassis - usually 3/4 or 1/2 inch thick, and 8x8 or 9x9 inches is size.
This chassis, with heatsinks on top of it (either passive or fan-cooled) weights 3-4 pounds, and provides stable and easy to cool platform.
PSU units are slightly bigger and heavier.
Units with fan cooling usually have small fan temperature controller circuit mounted at the back of the chassis. As you can see, all 'guts' of the amps and exposed.

Output transistors

If amplifier is built with TO-3 transistors (metal cans) - they are usually mounted on top of the chassis, between PCBs and heatsinks. TO-3 option is only available for BJT transistors.
If plastic encased transistors are being used (e.g. all FET transistors) - they are mounted under the chassis, so the dimensions of the chassis can be slightly smaller in this case.
All advertised power rating applies to continous sinus AC output power (actually tested). For music material, actual power will greatly exceed the specs.
Whenever required - all transistors are closely matched for their Vbe and Hfe parameters.

PSU

All but one of our designs, consist of two units: proper power amp, and the PSU (power supply).
Keeping power supply separately doesn't make it cheaper, BUT it separates noisy (in electrical sense) PSU from sensitive input stages of the amp. It allows better way to control noise and hum. Finally, it allows us to expose the 'guts' of the amp itself for those of us who enjoy it in esthetic sense, while keeping PSU shielded.
Now, PSUs can be built in traditional way - using top quality toroidal transformers (heavy!) with big bank of electrolytic capacitors (big!),
or using smaller/lighter SMPS PSU - kind of like in your PC, or laptop.
The fact is, that 60% of our builds, as per customer request, are done in traditional way - with transformers.

Other stuff

The PSU unit usually also houses VU meters, slow start module, and speaker protection circuit - to quickly disconnect your expensive speakers, and prevent them from damage, when the amp fails.
Protection circuit is designed with NMOS relays (instead of magnetic/mechanical ones), that can switch speakers off in matter of microseconds, and can handle heavy current of the amp. Magnetic/mechanical relays are notoriously unreliable, especially when they age. This feature (NMOS relays) is very seldom seen on commercial amps.

Each amp, after it's built, is thoroughly tested and tuned (if needed) to meet the specs. Each amp will come with oscilloscope screenshots presenting its performance at full power and frequency range.

Each amp is built on order, by hand - electrically and mechanically.
Each single component - even resistors and capacitors - is checked and tested before being used.

Pricing and ordering

These amps are not cheap - pricing starts at $2000.00 (Enki 25 class A amp).
Final cost depends on options, which can include: PSU (as described above), choice of chassis: wood or aluminum, active cooling with fans, or passive cooling with heatsinks.
Just let us know what is your idea of a power amplifier!
We only build limited number of amplifiers per year - as of Jan 2021, the waiting time to start working on your order would be slightly over 1 month, and it will take approximately another month to complete the build, unless we have some amps available in stock, which happens rarely.
Please inquire: Daniel@DanielRoyce.com

Each amp comes with lifetime warranty, and if it fails it will be fixed or replaced.
We ship worldwide.

We design and make high-end audio power amplifiers.