Audio-GD - R7HE 2020 Magna R2R DAC

Audio-GD is world renowned within a small group of audio connoisseurs. Its regenerative power supply and FPGA corrected R2R DAC, capable of both native PCM and native DSD makes it stand out. And then there is its giant cabinet and its weight of over 17 kilos. Initially I got lost in the R2R models offered by Audio-GD. But once explained to me I now see it’s rather simple.

There are two classed of electronics, the R8 series being the standard 00:43 - version with SMD components on a single PCB. And the R7 series that has a more sophisticated DSP board, almost only WIMA capacitors and DALE resistors, a heavier chassis, a 10 MHz external clock input and class A power supplies in stead of standard voltage regulators. Both series are also available in the HE version that in stead of three mains transformers for digital, left channel and right channel, has a regenerative power supply to almost eliminate any negative influence coming from the grid. The review sample is the R7HE, so the ‘deluxe’ version with regenerative power supply. The 2020 extension indicates it’s the current version.

The distributor Magna Audio then upgraded it somewhat more 01:34 - by replacing some components in the digital circuits plus silver cabling at a modest extra charge. Hence the addition Magna. The Audio-GD is a digital to analog converter that must have its analog outputs connected to the amplifier. Both single ended RCA and balanced XLR outputs are available, as are special ACSS outputs on MiniXLR. These are compatible with Krell CAST and thus relevant to Krell users. If you use your computer or laptop as music source, you connect it over USB, SPDIF or TOSlink to the DAC, USB often gives the best result with computers.

You 02:17 - can also connect a cd-player over SPDIF, TOSlink or, in some cases, I²S. The latter uses an HDMI cable but is not compatible with video equipment. Only if your digital source has an HDMI socket labeled I²S according to the de facto PS-Audio standard, it is suited for this DAC. If you use a streamer or network bridge as digital source, it is to be connected to one of the inputs. SPDIF and USB are the most popular, AES/EBU is used too, I²S is less used but is a very good interface.

The streamer or network bridge is then connected 02:56 - over the network to your router for internet sources and over the router to your computer for locally stored music. Usually streamers are controlled over tablets or smartphones. Network bridges need a suitable program to run on the computer. The Audio-GD is huge and heavy. It’s an aluminium cabinet that measures 430 by 488 by 125 mm and weighs 17.4 kg. Especially the depth is something to take into account. When we look at the front we see the power button and three smaller buttons. Settings lets you select the setting you want to change, Select Left lets you go back in a menu and Select Right lets you step forward. When not in the settings mode, you use the select left and right for input choice. The display appears to shows quasi-random characters. But together with the manual they let you set for instance oversampling, PLL chasing, display dimming and so on.

It is an archaic system but it works and most people will not change settings 04:08 - after initial choices are set. A remote control is optional. In the middle we find the IEC mains entry with above it the digital inputs. That starts with a mini USB for updating the firmware. Next to it the AES/EBU input on XLR, the SPDIF input on RCA, a 10 mHz clock input on BNC, an optical digital input on TOSlink, the I²S input on HDMI and the USB B connector according to the USB Audio Class 2 standard. On request other input configurations are possible.

If you want two SPDIF inputs on RCA and no AES/EBU, 04:54 - that can be arranged. Want BNC’s in stead of RCA’s, no problem either. There are three kinds of analog outputs: single ended on RCA, balanced on XLR and Krell CAST compatible ACSS on miniDIN. As you can see no space is left unused. It might be a very big DAC but the space was needed. On the left you see an R-Core transformer that size wise would not be misplaced in an amplifier. The R-Core type of transformer is getting more popular by the day for audio applications.

They can be wound more evenly than toroidal transformers. This transformer feeds a balanced class A power supply that - in stead of 50 Hz - generates a clean 400 Hz AC current. This higher frequency is chosen since it is more efficient and the end result has to be converted to direct current anyway. This AC current is then sent to three separate R-Core transformers that feed individual class A power supplies, one for the digital circuitry and one for each analog channel. The circuit board in the middle contains all digital interfacing and processing.

In the middle we see the Altera Cyclone IV FPGA which is a microprocessor 06:20 - that is programmed by Audio-GD, I presume to do the upsampling, digital filtering and the like. Two Xilink FPGA’s closer to the inputs are probably used for interfacing. Furthermore two costly Accusilicon precision crystal oscillators, one for 44.1 kHz and one for 48 kHz based sampling frequencies. To both sides of the digital board we see the analog circuitry. I removed the metal shielding of the bottom one so you can see the SMD resistor banks that form the digital to analog converters. There are two banks for each channel to generate true balanced outputs. A Xilink FPGA per bank switches resistors in parallel rather than in series as is usual with ladder converters. This way of working makes it possible to work around resistor tolerances and achieve a higher resolution. Below the DAC board the analog audio is situated.

As mentioned no SMD components here, only 07:22 - through-hole components of best quality. Basic use is quite simple: press the power button, wait for the unit to start up and then select the required input. Although not needed you can then play with all kinds of settings, for instance the phase locked loop ‘catch range’. If you use a very high quality source, the catch range can be limited to reduce jitter. Oversampling can be set to off or to 2x, 4x or 8x. You can even upload other software to get a TDA1541 like behaviour. The TDA1541 was a very popular DAC chip by Philips that combined a ladder converter and oversampling. The maximum sample rate varies per the input. I²S does PCM up to 384 kHz, 32 bits and DSD up to DSD512. USB does PCM 384, 32 bit and DSD256 while SPDIF, AES/EBU and TOSlink do PCM up to 192 kHz, 24 bit and DSD64. I have been playing around with the settings to conclude that the non oversampling mode was best to my taste.

In this setting it has the same character as the Holo Audio May DAC 08:49 - I reviewed two videos ago. Which means it sounds very natural and relaxed yet dynamic and powerful. It’s very clean on voices and has a fantastic way of reproducing strings - especially double bass - and piano. The stereo image is not big or small, it is just natural. This is a very fine sounding DAC that never fatigues and plays anything with ease, from 60’s jazz-folk-rock by The Pentangle to Rossini chamber music, from Wagner to Imagine Dragons and from Muddy Waters to Duke Ellington.

I auditioned the Audio-GD in my setup 1, now 09:29 - using the Uptone EtherREGEN to feed the Auralic Aries G2. DAC’s of this level should be fed a quality signal like this, of course. Judging on the sound quality the Audio-GD R7HE Magna is well priced. With the Magna options installed the price is just under € 3.800, clearly cheaper than the aforementioned Holo Audio May. That might sound yet a bit better, although I can’t say to what degree precisely since I couldn’t do a direct comparison. The Holo Audio has a more mature user interface while the Audio-GD is a bit rough on the edges. For some operations you need to mute the amp to avoid plops which is no problem unless you have the family operate it as well. If you can live with that, you really buy a very good sounding DAC with lots of tweaking options for a attractive price. That brings us to the end of this video. There will be a new video, as always at Fridays at 5 PM central European time.

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