 Glasshouse Passive Pre-amplifier No.1
front view
Glasshouse Passive Pre-amplifier No.1
rear view
Please read before this ordering
Do you need tools?
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Introduction
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A passive preamplifier by definition is basically a control box where numerous source signals come together to one location, through a selector switch you choose which signal you want to hear then onto a volume control, be it a potentiometer or stepped attenuator, then onto your amplifier. Simple, no power supply, no signal circuitry.
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The design formula
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When designing a passive pre-amplifier you have several criteria to consider as the following discusses:
1. Keep signal wire lengths as short as possible, passives are not good at driving long runs of interconnect so the distance from the inputs - selector - volume control device - output socket is vital. As a result we have kept the chassis as small as possible without limiting the possibilities of what the chassis can enclosed, the Glasshouse Passive Pre can accommodate DACTs 6 deck stepped attenuator if you so desire. Also, direct straight line point to point wiring. There is no point making your wiring nice to look at if you are adding 10cm onto signal travel distances.
dimensions (with feet and knobs fitted)- 86mm(h) x 160mm(d) x 135mm(w)
2. Chassis material and product weight. The Glasshouse chassis is made of 2mm aluminium a reasonable cost material, non-ferrous with shielding properties so limited interaction with nearby separates. The finished product weighs in at 1kg so it will not move all over the place when you turn the volume or selector knob, especially as such devices do have a high turn torque.
3. Component selection. After all this is at the essence of a passive, keeping at a budget of £200.00 (exc.vat) for the kit. All phono socket are Audio Notes very own silver plated insulated chassis type, a highly regarded connector. All signal wiring is HGCs 0.5mm diameter 99.99% pure silver sheathed wire. For the selector we have gone for the famous Elma 2 pole 6 way, a precision engineered device, one of Hificollective`s best seller. Lastly we have chosen the Dale Vishay L pad 23 stepped attenuator to put the icing on the cake of this superb performing passive. The Dale Vishay is available at 10K, 50K, 100K and 250K, we would recommend the 10K type for solid state users and 50K for the valve heads.
4. Clearly marked front panel. Often with stepped passive the screen print on the front panel will label which is the volume and the selector, the latter is usually marked with its inputs be it a description of the source or with a number. What is very useful but often missed is numbers marked around the volume. The Glasshouse Passive have the 23 steps numbered so you can easily obtain your normal listening level.
5. Inputs and outputs. Our passive has 6 pairs of inputs, 1 pair of record outputs and 2 pairs of output RCA sockets. Plenty of inputs for multi-source systems and you can feed a subwoofer and satellite systems.
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The kit
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As far as complexity of build goes the a passive is one of the easiest things a diyer can build. However saying this it is not for a true beginner, in order to give justice to this high calibre piece of hi-fi you need to be able to make a good solder join.
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.
All that remains is wiring up the inputs and record out to the selector, the selector to the attenuator to the output sockets. With around 60 solder joins to be made it will take around 3 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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Build requirements
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To build the Glasshouse 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 - £200.00, built & tested - £250.00, built, tested & 100hrs burn in - £265.00
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