The Symphonies Plus Vacuum Tube Pre-amp is made and sold by YS audio as a level 2 product for around £500 + duty and taxes in the UK and less from eBay USA. YSA have a scale of 1 to 4 for their products and they sell a number of pre-amps and power amps at various levels of internal parts quality and upgrades. This unit can be upgraded to level 4 by a few easy mods and tweaks. It really needs some changes to get the very best out of it and in some set-up's without a few critical mods it can sound mis-matched. It uses 3 x Ecc83 (12AX7) tubes with some global feedback in the circuit. Sound of the unit before any upgrades or mods is fast, dynamic with bite and edge without being overly sharp, not at all fat, slow, coloured and mushy like some other tube amps can be. Construction quality as standard is excellent with a full non magnetic metal chassis, thick brushed aluminium face plate, anodised aluminium knobs, C core mains transformer, regulated power supply, tube rectifier, circuit screening and tube dampers etc. Dale resistors are also used throughout the circuit.

This model includes the following upgrades :-

If you search the diyaudio.com forum you will come across a passive attenuator design by a guy called George Stantscheff. What makes his design unique is that the audio does not pass through any contact points in the form of a "wiper" as with a pot or a stepped attenuator. The main component in the Light-speed Attenuator are Silonex NSL-32SR2 Opto-couplers.

Sound is very surprising for a passive and not what I expected when I borrowed a DIY one off Dave H down the road from me. Most passives sound detailed but thin, weak, small and lacking dynamics. This passive is quite the opposite having a very wide sound stage, really deep bass and a natural textured sound. This is by far the best passive pre-amp I have ever heard even compared to TVC / AVC units. In a system with sensitive speakers it works amazingly well. However with difficult loads such as a power amp needing an active pre-amp with voltage gain like my Nelson Pass F5 or the F3, or using speakers under 90+ db then it is not as great. It still has the same wide sound, deep bass, detail and naturalness, but it sounds 2D with no projection. It just lacks that edge and bite of an active stage.

I was asked by Val to upgrade his Havana DAC with better capacitors and non magnetic resistors in key locations. This is the result. Output coupling is now by Clarity caps with Glass based Russian silver mica and BlackGate caps used elsewhere. This DAC uses a classic Bur Brown PCM56P chip with a simple form of conversion using matched resistors in a ladder configuration. This results in less signal manipulation during the conversion process. Those clarity caps are huge and only just fit in the case and I had to fit them rotated 90 degrees compared to the originals. These would not be my choice for practical reasons of fitting as the unit is very compact. Other upgrades include Silver WBT RCA sockets and flat sliver wire on the output plus a gel tube damper socket, although a Teflon socket could be used here instead. Build quality as standard is good with Nichicon Muse Gold electrolytic capacitors along with regular film foil caps used else-where.

Mods