Custom Tube DAC

I have made this DAC for one of my colleagues who wanted something more analog sounding than his punchy Burmester CD player, DAC that would sound close to his Garrard 301 turntable with Koetsu cartridge.

It was quite easy job, one full day of assembly plus two days of burn in and tuning to find the sweet spot. I’ve set myself a challenge – build a DAC that will be as good as my personal unit, or better..

Custom ordered chassis, made from Dibond instead of full metal. Dibond is a synthetic material with 0.3mm aluminum layer on the top.

In my opinion it was the best possible material that could be used for this purpose – weight is few times less than aluminum or copper, very easy to drill the holes and it provides full shielding due to the aluminum layer. 3mm is thick enough to hold stable even when loaded with 8kg transformer (I tried!).

Digital board PSU: 0-16V 30VAC sealed transformer, followed by Greatz rectifier made from 4x Vishay NOS diodes, CRC filter with absolutely amazing Epcos Sikorel capacitors and 10W mills 4,7r resistor.

On the digital board PSU input pins I have placed NOS Motorla 7805 goldpin regulator.

I own many high end regulators like: NewclassD, Teddy Pardo Reg etc..   and to be honest I always slightly prefer good, old 7805 from the old stock supplies. It sounds full, with more body and timbre comparing to slightly analytical regulators from current production.

Tube analog stage: CCDA (constant current draw amplifier) with Philips PCC88 tubes. These tubes are the same like ECC88 with one difference – they have 7v heater requirements instead of 6.3, and they are slightly cheaper too!

I always prefer to set up a slightly starving filament with every small signal / preamp tube I use and run it on low currents (30% of their maximum ratings). It simply sounds best to me like this, and when I say „best” I mean: musical, colorful, dynamic, full bodied presentation – like the ones from reference tape master recorders.

These D-getter Philips are on the same performance like Amperex Bugle Boy 6DJ8 with D getter from the late 50’s. Philips is slightly more musical with smooth presentation, however Amperex has better bass and overall darker presentation. I like them both.

Resistors used: Audio Note tantalum 2W, Kiwame 5W, Riken RMG – this combination was chosen after the final tuning. Capacitors – Vintage Sprague Vitamin Q. In my own system I have almost fully replaced all Duelunds with these old beauties.

High Voltage PSU: Highly oversized gem – British Partridge transformer. Internal screened, double C-core transformer with natural epoxy resin. There is no company in the world right now, that manufactures such a quality transformers. Best of the best, nothing come even close, especially when it comes to sound with this unit!

Marconi 6023 black plates rectifier followed by CLCLC circuit. 10uf Siemens MKV oil condenser – 10H Triad choke – 220uf Nichicon Negative Black – 8H Choke – 10uf Oil Siemens MKV. Only one electrolytic in the chain to gain the smoothing capacitance.

IEC socket – TDK Japan with internal EMI/RFI filter. Sound-wise – these are superior to any Furutech socket I have ever tried – and I have tried all besides latest NCF socket.

5N 10awg power cables using Illuminati Power Reference conductor. Western Electric, Oyaide and Ortofon PCOCC signal conductor, Transparent Reference coaxial cable.

I have also applied some screening for one choke and transformer using pure copper plate (check last photo). While there was no hum without them, addition of the screening improved three-dimensional sound presentation and overall cleaned the background.


Time to listen…

DAC sounded very, very good from the very beginning. I have listened to it only for one hour after all work was done and leaved it for two days so it could initially burn in.

After two days I made a serious listening session with one of my favorite first press US albums: Judas Priest – Screaming for Vengeance, Toto – Isolation, Stevie Ray Vaughan – Couldn’t Stand The Weather. To make long story short – I believe that testing equipment on audiophile records it’s a waste of time, most of them sound at least good on almost every system, it is not a challenge to make Diana Krall sound pretty. Try do the same with pop, rock or hard rock from the 80’s. If your system can play Judas Priest with 100dB sound pressure with no sibilance and jaw-dropping performance – than you own a good system.

Enough said.

DAC played like a dream, comparing to my personal DAC based on AD1865 it had better dynamics, and what surprised me the most – overall much more smooth presentation. I highly enjoyed the sound from the first note, nothing to complain about. Have a look on the video and judge by yourself.