 Glasshouse TVC Passive Pre-amplifier No.1
front view
Glasshouse TVC Passive Pre-amplifier No.1
front internal view
Please read before this ordering
Do you need tools?
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Introduction
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The Glasshouse Passive pre-amplifier No.1 has been a great success, which goes to show how passives always have an important role to play in hi-fi. The neutrality and clarity of the little box has won the hearts of many. Featuring the low cost Dale Vishay stepped attenuator. shortly after the launch we offred the option to use Audio Note`s amazing series fed stepped attenuator instead, adding a touch more detail and depth to the sound. So what next? Following the numerous bulletin boards on the net, it would appear that a host of you guys have tried Music First`s passive magnetic pre-amplifier, which recently won the 2006 Hi-FI News award for the best pre-amplifier, to great effect. This unit features a transformer volume control, TVC, instead of the signal being attenuated through resistors, the signal is basically piped around the windings of a transformer, the transformer is tapped and switch controlled at the front. Simple. So we thought we would have a go.
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Glasshouse TVC passive
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Without changing any of the most important criteria applied to the original passive - to outline:
- Keep signal wire lengths as short as possible - keep the chassis as small as possible (front to back distance is 160mm.
We had to source a transformer that would fit the original box and boy did we find one. With a few subtle changes to the original design to put the Glasshouse badge on, we now have be-spoke transformers that not only fits in the box, but are at an excellent price. (RRP - £150.00 a pair, exc. vat & p&p). Early reports suggest that the Glasshouse TVC passive is very close to the sound of the Music First magnetic pre-amplifier and may we add at a fraction of the cost.
The First prototype featured the new transformers, supplied with solder tags, wired with our very own HGC 99.99% silver 0.5mm diameter wire. Each transformer has 24 solder tags, once built the kit uses 10m of wire. The HGC wire, sheathed in telfon, has a diameter of 1.385mm. If you have ever worked with teflon in a restricted area you will know that it is not exactly bend friendly, preferring to take a relaxed curved pathway. If you have a quick look at this PICTURE you will see that the version on the right looks a little squeezed in. To be honest, it was quite a hard build. When formulating a kit you must always think of the constructor, we had to find a more "bendy" wire. So I called Mirko from Mundorf, who is always singing the merrits of their 99%silver/1%gold wire, a mix that they say, is sonically superior to pure silver. Also, it is sleeved in PTFE with a combined diameter of 0.75mm and a lot easier to manipulate, so we ordered a 50m reel. Needless to say prototype No. 2 was a far easier build and sonically very similar, so problem solved.
You will see from the PICTURE that the 2 pole 23 way selector on prototype No.1 is different, this featured the Audio Note selector switch, as used in their stepped attenuator, this retails at £51.00. Cost is always an issue, it is a balancing act sometimes, not wanting to compromise the sound quality by using a cheaper component. We received a consignment of 2 pole 23 way selector switches from the makers of the Dale Vishay, retail price £12.00, just after building the 1st prototype. As a new version had to be built as a result of the wire problem, we built it using the dale selector. On listening the difference was minimal and as the chassis drill hole was the same, the kit now uses the Dale selector and you will be £39.00 better off! However if you wish to build your kit with the Audio Note switch we can accommodate.
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The kit
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The build is slightly more complex than the standard passive on account of the wiring up the transformers, but far from being complicated. You will see from the numerous pictures on the GALLERY PAGE the transformer is wired to the selector externally as there isn`t enought room inside to do so. once built it is fitted in place. The kit is supplied with the fitting holes for the transformers pre-drilled.
Mechanically the kit goes together very easily as long as you have the right tools for the job and follow the recommend sequence in the instructions. With around 140 solder joins to be made it will take around 5 hours to complete, test and then play.
The Instructions provided are very clear, giving step by step details backed by pictures and diagrams. The instruction book will soon be available as a pdf file download on the site.
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The conversion kit
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For those who have the original kit, that features the Dale Vishay and want to upgrade to the TVC version, we are offering a Conversion kit. All wiring from the phono sockets to the selector switch has to be removed as the transformer need the space to be clear for fitting. The stepped attenuator needs to be removed. Then the re-build begins.
Parts list:
1 x Glasshouse TVC transformer
10m x Mundorf 99% silver/1% gold
1 x Dale 2 pole 23 way
1 x instructions
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Build requirements
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To build the Glasshouse TVC Passive Pre-amplifier you will need to:
- know how to solder a good join
- be aware of safety practices when it comes to electronics
- have an understanding of switching electronics
- be able to read a circuit diagram
- own a multimeter.
- be able to understand the instructiosn provided fully.
- have patience, rushing creates mistakes
If you do have problems, we can help via the telephone or e-mail or you can return her to base for repair.
At the end of the experience you will have a kit that not only looks amazing but it will sound awesome for many years to come.
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Price list: (excluding vat and carriage):
kit - £350.00, built & tested - £450.00, built, tested & 100hrs burn in - £465.00 conversion kit - £200.00
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