> 1465 DAC Interface Transformer SOWTER AUDIO TRANSFORMERS


1+1:5+5 Current / Voltage transformer - BUY

1465 Response

Frequency response 100 Ohm source 20K Ohms load

Sowter DAC transformer

APPLICATION Our most popular transformer for use with most current out Digital-to-Analogue Converters. Works well with any current out DAC. Provides current to voltage conversion with gain to achieve at least a line level signal (0 dBu 0.775V) depending on the I/V resistor used. Presents a low impedance to the DAC output for best frequency response and quantisation noise reduction. . Provides significant sound quality improvement when compared to other interface methods. Ensures full isolation of digital noise in ground and supply rails. 

We recommend that the I/V resistor is placed across the secondary of the transformer (See below). The transformer has sufficient inductance for good quality operation with higher values to increase the output level..  Lower values may improve the sound but will reduce the output level. Can be configured to drive 9335 attenuator without loss of bandwidth. Can be used driven from multiple parallel DAC's to increase output level. Twin primary windings are provided for use with twin DAC's fed with complimentary data. This approach has been used in order to cancel out quantisation noise.

The I/V resistor across the secondary of the transformer instead of the primary has yeilded the best result according to some customers.  The value of the resistor should be increased by the ratio squared.  The table below suggests values for rexperiment.

FEATURES Exceptionally large and high performance transformer.  Twin primary windings are provided for use with two DAC modules fed with complimentary digital signals which provides improved cancellation of quantisation noise. For normal use connect the two primary windings in parallal. Twin secondary windings with geometric balance for driving differential (push-pull) amplifier. These may be used in parallel to improve the bandwidth and reduce the output impedance.  Mumetal core for minimal harmonic distortion.  Mumetal can for magnetic shielding. 


Referring to the diagram below: To connect the primary windings in parallel (usual configuration) connect Grey to Orange and Brown to Blue.

To connect the secondary windings in parallel connect Violet to Pink and Yellow to White. To connect in series connect Yellow to Pink. If you are driving a balanced input it is normally better NOT to ground the mid point (Yellow-Pink). For feeding an unbalanced load one side can be connected to analogue ground. For feeding 2 grids Yellow-Pink can be grounded to reference the grid bias.

If possible the grounds of the digital part of the circuit should not be joined. The secondary may be loaded balanced or unbalanced (one side grounded).


Current out = +/- 2 mA = 4 mA p-p = 4 / 2.82 mA= 1.43 mA
Configuration: Primary coils in parallel. Seconday coils in series. Ratio = 1:10
Secondary current = 0.143 mA
Secondary load resistor for line level (0.775V) = 0.775 / 0.000143 = 5420 Ohms. Allow 25% for copper loss. Use 6.8K Ohms

Configuration: Primary coils in parallel. Seconday coils in parallel. Ratio = 1:5
For line level out use 3.3K Ohms secondary load. For increased output level increase load in proportion.

Suitable DACS:

AD1860N AD1862 AD1865DSD1792 PCM1702 PCM1704 PCM1738 PCM1792 PCM1794 PCM1795 PCM1796 PCM1798 PCM2702 PCM56 PCM63 TDA1540 TDA1541A TDA1543 TDA1545A TDA1547
45 mm Dia. x 52.5 high
3.0 H Typical 
6.7  Ohms  Typical
SECONDARY DC RESISTANCE (2 coils in series)
1.29K Ohms Typical
Parallel secondary windings
+/- 1.5 dB 5 Hz to 100 kHz
Series secondary windings
+/- 1.5 dB 5 Hz to 50 kHz
1465 connections
Sowter 1465 Balanced DAC PCM 1704 Sowter 1465
Sowter DAC transformer