Magic and Microphony (Pt 2) – 6SN7GT tubes

Back in 2015 – Magic and Microphony (Pt 1) – I suggested that the tendency to ‘microphony’ in some vacuum tubes / valves, can actually enhance the sense of ‘ambience’ or ‘live-ness’ of the reproduced sound.

The last thing I wish for, is a ‘dry’ or ‘threadbare’ sound that is lacking in ‘resonance’ or harmonic ‘decay’.

However, having moved on from a 2-stage tube preamp, back to a single-tube, ‘WOT’ (With Output Transformer) Tube Line-stage, I’ve found that sensitivity to ‘microphony’ can be a serious problem.

Vacuum tube Headphone Amp-DAC

The Sennheiser HD 650 is a great headphone with a little bit of sonic ‘magic’ appeal. The attractively priced MassDrop HD 6XX version is a special bargain.

A popular and nice match for the Sennheiser HD 650 / HD 6XX is a vacuum tube headphone amplifier.

The project here was built by Jeremy Young. It was inspired by the Bottlehead OTL headphone amp, but circuit ‘operating points’ were determined to suit a locally made power transformer.

Consider Connectors

“God is in the detail” – Ludwig Mies van der Rohe (et al)

Sometimes it’s necessary to re-examine the little things, the forgotten details.  Try to dig out the last 10% improvement.

Consider amplifier and loudspeaker connectors.

We know that music signals are alternating current, AC not DC – swinging positive/negative.  We know also that “current in a conductor resides at the surface at high frequency” (Prof. Malcolm Hawksford, HFNRR Aug 1985):

WOT tube Line-stage redux – Pt 1

A Line-stage With Output Transformer (WOT) was built back in 1998, a single 5687 tube per channel with output transformer (OPT).

However I failed to get rid of noise (EM pick-up and attenuator switching noise).  I lacked the expertise to optimise Grounding and to shield and/or orientate the output transformers (OPTs) properly.

Now, I have been fortunate to acquire a pair of Tango NP-126 Line Output transformers. So, I must re-visit the WOT Line-stage.

AUDIO NOTE Kit One amplifier – upgrades

This ‘integrated’ single-ended 300B kit amp was introduced by Audio Note UK in the mid 1990s.  This example was built by me in 1997.

The standard Kit One looks plain and unattractive, so I dressed it up with some Kondo-copper aesthetic!

Not inexpensive (around GBP799 in 1997), this was however a quite good sounding 300B SE amp.

McINTOSH MR71 vintage tuner upgrade

The McIntosh MR71 vacuum tube FM stereo tuner was in production from 1963 to 1969 and retailed for US$399.  (Today a good MR71 can still command a price 5 times that!)

The MR71 was the last tube tuner made by McIntosh and, together with the earlier MR67 model, is regarded as the best tube tuner that McIntosh made.

SUN AUDIO SV-2A3 amplifier

This Japanese single-ended, vacuum tube amplifier can be purchased in ‘kit’ form or fully assembled.

Power output is 3.5 watts/channel.   Supplied with Russian Sovtek tubes – 2A3 (2), 6SN7 (2), 5U4G (1).   Amplifier weight is 16 kgs.

Input Sensitivity is high (150mV), so with the in-built volume controls, this amplifier will accept Line level sources easily.

‘Adagio’ TDA1541A non-oversampling DAC

When I first listened to DACs, I concluded quite quickly that ‘multi-bit’ DACs sounded more like music to me, than ‘bitstream’ DACs – more dynamic & ‘alive’.

The TDA1541 was originally developed by Philips (in 1985) as a high performance stereo DAC.  The ‘A’ version was manufactured between 1989-1995.  It was (is still?) regarded as one of the best sounding DACs ever made.  This chip was used in almost 100 different CD players

2A3PP amplifier – Upgrades

Update 21 Jun 2020:

This 2A3 Push-pull amplifier, built in 2009, has proven itself to be an excellent performer.  Compared with Single-Ended amps,  I am happy about the additional watts and improved bass control.

The design of an amplifier is more important than parts quality – don’t waste $$ on expensive parts in a poor design.

However, I think it is worthwhile to spend some more time and $$ on this amp.

Magic and Microphony (Pt 1)

Real music has dynamics.  Macro-dynamics – with unrestricted headroom in crescendoes.  Micro-dynamics – with subtle low-level information.

Music should be reproduced also with a ‘time’ dimension.  Not just tempo, but each sound accompanied by an harmonic ‘envelope’, where overtones are produced and decay naturally – providing a sense of ambience, dimension and space.