Tag: Sowter

Morgan Jones’ visit

I had the pleasure of Morgan Jones visiting me today. We’d discussed for some time a meeting and I was looking for the right time. August looked to be it as I was taking some days off work before the arrival of our next child.

Morgan had planned to ride in his bike into London. What could have gone wrong? Well, after more than two months of hot weather and no rain, we had a classical British rainy day.  He arrived completely drenched in his leather bike gear.

Oh well, it all went uphill after that. We listen to Tom Waits on the new setup after the DHT shootout held yesterday.

Playing “Heart Attack and Vine” from Tom Waits

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Custom transformer for Discrete DAC

Some 3 years ago I built the famous “Starlight” discrete DAC and CD transport, the DIY version from Sonic Illusions.  This is, in my opinion, one of the best DACs I’ve every listened to.

One of the disadvantages of the DAC output is the high (10kΩ) resistance and AC coupling requirement (unless you are prepared to balance DC, etc.) The traditional output configuration is an output capacitor feeding a step-down transformer to provide lower output impedance. The DAC can do only 1Vrms maximum due to the TTL output logic. With a 4:1 output I had to date, I wasn’t able to drive properly my VT25/10Y preamp into the 4P1L PSE amplifier. 

I decided to try a 1:1 output transformer but I had a clear challenge. The big primary inductance (Lp) needed demands a careful design and construction of the transformer to minimise the leakage capacitance and inductance which will impact the HF response. As I’m driving a long cable into the DHT preamp, this presents a demanding load of 47kΩ||400-600pF.  

I contacted DvB transformers to order a custom transformer to fit my needs:

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Headphone Parafeed Amp – Part I

Introduction

headphone-ampDid you ever dream about having a nice valve headphone amp? I did. Several times in fact. I’m not keen on the OTL designs and yet, owning a pair of Grado’s SR80i 32Ω headphones, I’ve been looking at different topologies and designs for headphone stages. 

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