Beresford TC-7520 DAC amplifier review

Soundcards and Speakers 106 Page 9 of 10 Published by

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External Usage

External Usage

These days people are acquiring more and more electronic sources that feature digital output in one form or another.  In order to be thorough, we decided to look around the lab and find some external S/Pdif sources.  We tested the TC-7520 with a Eureka external HDD audio/video player and a PlayStation 2 for some external gaming and CD tests.  Both units were connected to the 7520 using optical S/Pdif cable. 

The TC7520 produced excellent sound over headphones for the FLAC on the HDD player and our gaming/CD tests using the PSII.  Although we did notice some higher frequency noise on the PSII when playing normal CDs using it as a music source. We could not reproduce the noise on any other gear.

Electronics Overview - We use this section to shows those new to PC audio and audio electronics as a whole, what they are actually buying when they purchase new audio devices. 

PCM1716E DAC
What? Isnt the whole unit called a DAC?  Well yes, the entire unit is called a DAC for short and to signify the duty.  However, inside there is the actual Digital to Analog Converter chip that performs the conversion. The two terms are interchangeable to many in the audio world.

Beresford DAC

 

The PCM1716E is from Texas instruments Sound Plus line up of audio grade components.  The DAC is a enhanced multi-level ÄÓ (Delta, Sigma) Architecture Digital to Analog converter IC.  This IC offers a signal to noise (SNR) and Dynamic Range of 106dB.  The output Total Harmonic Distortion and Noise (THD+N) of the unit is -96dB.  This DAC also features an 8X digital oversampling filter.  This chip accepts 16, 20, 24 bits at a (fs) of 16 KHz to 96 kHz.  Burr Brown DACs are high quality converters seen in many external DAC and soundcards.

NE5532P Opamps

Beresford DAC

The NE5532P are the stock opamps on this unit. They are a go to opamp for many designers offering reasonable price to performance for many audio circuits.  They can be found in everything from professional grade studio mixers to consumer gear. This opamp has a slew rate of 9V/µS and in the audio world this unit would be considered generic.  This unit can produce some reasonable output given the proper circuit designs.  Many times these opamps are used with sockets in an attempt to keep the final price low as they are meant to be replaced.

Timing CircuitsAn interesting note is the Beresford DAC has two PLL timing circuits.  One timing circuit is employed for the S/Pdif input sections and the second is used for the USB input. This is somewhat unique design among external DAC units.

USB Receiver Chip
Many DAC units have USB input from compatibility with laptops or desktops.  External DAC modules require a separate circuit to accept the USB digital and convert it to a usable format the DAC chip itself can understand and process.

Beresford DAC

Many designers usually go with the older PCM2702 chip but Beresford opted for the improved 2902 chip.  We will say this chip has some improvements over its earlier siblings we come across the same issue the 2702 had when used in this capacity, in that the USB input is limited to 16bit 48Khz playback. This circuit also employs its own re-clocking circuit separate from the other used for S/Pdif.


Modification Options
Opamps - DAC units can offer some exceptional gain to the modders in the community.  The Beresford TC-7520 DAC is no exception and uses separate opamps for the line and headphone outputs.   To get started, we can swap out the stock opamps with some higher grade units.  The designers anticipated this and installed some opamps sockets for both the line outputs and the headphone output.  These dual sockets allow the end user to tune the headphones differently than the line outputs.

Beresford DAC

LM4562 - This opamp has been popping up everywhere in the audio world, in everything from PC soundcards to DACs and amplifiers.  This opamp offers excellent THD+N ratings of 0.00003% (typ).  This unit also has a fast Slew Rate ±20V/μs (typ).

They are still a very new unit and are considered high quality in comparison to units such as a NE5532.  Beresford suggests these units for a quick and easy upgrade for the TC-7520.  Based on some quick RMAA comparisons in the lab, the LM4562NA produces lowers THD% and improved crosstalk measurements over the stock 5532s.

Beresford DAC

THS4032 These units have been popping up for quite awhile for use in current to voltage converters and buffer section in a few modified DACs.  The amp is extremely fast in comparison to the other units tested, offering up a 100V/µS slew rate and 100Mhz Bandwidth. We always keep a few of these around for testing in our ever growing 200+ unit opamp collection.

Final notes on opamps: We always do much more opamp testing then we show in our reviews as at Guru3D we habitually take things a step further in everything we do!  We had an opportunity to test the 7520 using a custom built discrete opamp and some current production units which produced some excellent results.  The inside of the case is large enough to accommodate a discrete opamp.  This may be an option for those of you that like the sound of a discrete opamps design over chip based units.

DAC Chip Modifications

For the more expert home technician in our reader base you can further mod out the actual DAC chip itself with a higher quality unit.  Many people have modified their TC-7520s with the WM8716 and further improved the sound quality.  The WM DAC is a 64X oversampling DAC compared to the stock DAC with is only 8X oversampling.

To note, Beresford offers an upgraded version called the Caimen that includes both the LM4562NA and the higher quality Wolfson DAC.

Disclaimer: we offer the modifications options so our readers can have an accurate idea of the value of the unit in both stock and with some investments of money and time.  Please understand that while some modifications are simple others are very complex and we do not recommend any modifications by unauthorized technicians. You will possibly mod your new DAC into a high end paper weight and definitely void your warranty.

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