Objective: to build an inexpensive stereo line stage based on a Russian tube. Participants may use any design, but the design must incorporate one or more tubes from Russia that the signal passes through. The power supply may be driven by 117 VAC, a wall transformer (AC or DC) or battery.
The Place: David's place in Reston, VA.
The Date: Saturday April 2, 2011. Contestents should arrive with their linestages between 10am and 11 am for testing to ensure they work.
Photos of the entries can be seen below. David's 6N3P entry was the winner.
Building your own line stage is very dangerous, particularly with the high voltages involved. We will not be held responsible for any injuries caused by you building your line stage. This competition is not for novice builders. We highly recommend that novices build one or more Bottlehead kits before considering a scratch build like this.
1. We will not accept entries that are shipped to the competition. You need to carry the line stage in through the door at the competition. If you live in another part of the country, you might consider holding a similar competition in your own region. Our committee decided we did not want to be responsible for items that were shipped to us.
2. Cost of components shall be $100 or less including the tubes, sockets, rca jacks, batteries and fuse/power receptacles. All of the tubes used in the design should have Russian markings on them.
3. Screws, bolts, nuts, wire, washers, lock washers, shrink wrap, cable ties, glue, adhesives and solder etc. are the only items not to be included in the $100. If in doubt, include the item in your $100. Do not include postage / shipping costs from the vendors in the $100.
4. You may use any other Russian tubes you like for rectifier, regulation, etc. Using other Russian components such as capacitors is encouraged. You may also use sand in the driver circuit. Try to be innovative and use some techniques you haven't tried before. Have fun.
5. For safety reasons, the 117VAC line stages will include an IEC connector, an on-off switch, a fuse, at least one power transformer and a bleeder resistor. The wall transformer and battery powered line stages should have an on-off switch, fuse and bleeder resistor.
6. All batteries will be enclosed and not be able to be touched from the top or sides.
7. A schematic and a list of all materials with part numbers and pricing needs to accompany the amplifier. Pricing shall be based on the quantity of parts shown on the schematic or, if greater, the minimum buy quantity. Other than the tube(s), components, both passive and active, may be sourced from any vendor such as: Allied, Digikey, Mouser, Antique Electronic Supply, Radio Shack, Edcore, Antek and Parts Express. Components may also be purchased from Ebay vendors, but no component should be made from unobtanium.
8. You may use parts you already own, provided each exact part is currently available in a catalog or commonly found on Ebay. Discontinued items should not be used. The intent is that somebody else could come along and build your design using the schematic and the list of all materials for the same price. As an example, I happen to have a 22uf 450 volt Nichicon capacitor laying around. I can use it provided that I can still buy that particular exact same cap at Mouser and I can show the part number 647-UCA2W220MHD6 and the current cost ($1.35).
9. Pricing of parts will probably rise in the course of a year. The pricing of the parts for the winning entry will be checked against the online catalogs. If the cost for the winning entry exceeds $100, it will be disqualified. One approach is to design for $90 which would allow $10 headroom for price increases.
10. Just for the fun of it, the case should come from Target. Be imaginative. Spend what you like on the Target stuff for the casework, but no Target stuff is to be used for electrical purposes.
11. All line stages shall be evaluated using the same source, amplifier and speakers. The input impedence of the amplifier to be used will be announced later. Presume at least 47k. The cables will not exceed 1 meter in length.
12. You should include RCA jacks for both input and output. You should also include a volume control.
13. All line stages shall be evaluated using a compilation of music on one CD. The selection will be eclectic and include classical, blues and other genres. Typically, the music will be from CDs that have been enjoyed at our regular meets. David will be picking the music.
14. We will provide a simple prize, possibly some little plate you can attach to your line stage that you can treasure for the rest of your days.
15. We will probably judge the entries based on how we did it for the 6V6 competition.
Set up:
- As much as possible, the same setup and positioning for all equipment(CD player/DAC/line stage/amplifier/speakers/cables/power cable) including positioning of the line stage on whatever support we use.
- A single CD with the music selections preceded by a test tone at roughly 440 hz to set the volume.
- All line stages to be invisible to the audience, even while not playing.
- All line stages will be numbered. The order of playing the line stages will be drawn from a hat.
- One designated person and a helper to be responsible for hooking up each line stage. These persons will not take part in the scoring.
The judges:
- Depending on the number of entries, we may need to limit the number of judges at the discretion of the organizers.
- If the number of judges is limited, priority will be given to those who regularly attend our Bottleneck meetings.
- Each judge will be presumed to have either cloth or tin ears.
The judging process:
- Each judge to be given a score card (and pencil) and will sit in an assigned chair throughout the contest.
- No discussion while music is playing or for 30 seconds thereafter when the score must be written down.
- There will be a preliminary round where all line stages are auditioned. The top three line stages will go on to a final round with a different music selection.
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