Results (photos and schematics at end of blog)
- The competition was held at Steve's place on April 11, 2010
- The first round results were very close. Unfortunately, both Jim and Ray's amps only worked in one channel. The final round resulted in a clear win for John's amp. All of the amps were excellent and we can highly recommend using the triode 6V6 as an output tube.
- Pictures and schematics (if available) can be seen below at the bottom of this post.
- Ray's amp won the Ikea prize.
February 25 Update
- Amps to arrive in the 10am - 11 am period, preferably closer to 10am
- Each amp to be turned on and tested prior to 11 am to ensure that each amp works and the offical tester knows how to do it
- Each amp to be given a name eg 'The Devastator'
- The order of audition will be random
- Everybody to be seated in their allocated chair by 11am
- Ray to supply scorecards and explain the rules
- First audition will be a short test run with the PP amp to get people used to the music and the judging procedure - that amp will be repeated later in the competition
- Each audition in first round to have about 20 minutes of music (6 tracks)
- Scoring to be be completed at end of each audition
- Short break between auditions (hopefully we can do one amp every 30 minutes)
- Slightly longer break at the end of the third amp for lunch
- At end of first round, the top three entries to continue (or two if we are running short of time)
- Fewer tracks in the second round
- Ray to present prizes for Best of Competition and The Ikea Award
- Event to finish at 4pm ( Ray flies to UK from Dulles at 18:40)
- No food or drink in listening area
- Send me an email if you need directions to Steve's place
January 3 Update:
- The competition will be held on Sunday, April 11. The starting time has not been set in stone, but plan on 10 am.
- If you are planning to submit an entry, please send me an email by February 1 which will be the cutoff date for entries. We have no idea how many entries we will have to allow auditioning time for, so we need to use this cutoff date for planning purposes. There is no entry fee.
- I have an email account at gmail. Please use rperry13 and I will acknowledge your email with directions to Steve's place in Stirling, VA.
- If you plan to attend but are not going to submit an entry, it would be helpful to send me an email prior to the competition so that we have an idea of how many people are turning up. There is no cutoff date for non competing attendees.
- Please review the rules below, particularly rule 1 about carrying your amp in the door.
- According to rule 7, there is no need to submit your schematic and parts list until the day of the contest, but for planning purposes, when you send me the email, could you let me know if the amp is single ended or push-pull.
Again, I thank all those who have made suggestions.
Objective: to build an inexpensive stereo amplifier based on a common output tube, the 6V6. Participants may use any design, single ended, push-pull, whatever, including two or four 6V6’s. The use of driver tube(s) is optional and at the discretion of the builder but the output tubes must be 6V6's.
The Place: Stirling, VA (near Dulles airport)
The Date: Sunday, April 11 2010. Kickoff probably at 10am.
Building your own amplifier is very dangerous, particularly with the high voltages involved. We will not be held responsible for any injuries caused by you building your amplifier. 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. After considerable thought, our committee decided we will not accept entries that are shipped to the competition. You need to carry the amp 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 $200 or less including the tubes, sockets, chassis, rca jacks, binding posts and fuse/power receptacles. Each 6V6 will be priced at $8.95 which is the cheapest in the AES catalog. We will use a more expensive set of matched 6V6's at the competition that will be used to audition all entries. For the other tubes, you may use your own special NOS tubes, but use the lowest pricing from the AES catalog. The model number of all tubes should appear in the AES catalog.
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 $200. If in doubt, include the item in your $200. Do not include postage / shipping costs from the vendors in the $200.
4. The design shall be based on the 6V6 used as an output tube. You may use any other tubes you like for input, rectifier, regulation, etc. Sakuma 6V6 - 6V6 style amps will be acceptable. You may also use sand in the driver circuit. Try to be innovative and use some techniques you haven't tried before.
5. The amp can be any class you like - single ended, push pull, class A, class AB, class B, class C, triode, ultralinear, etc.
6. For safety reasons, the amplifier will include an IEC connector, an on-off switch, a fuse, at least one power transformer and a bleeder resistor. No wiring carrying more than 1 volt (AC or DC) should be able to be touched from the top or sides. Plate dissipation for each 6V6 should not exceed 14 watts.
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. Components, both passive and active, must be current catalog items sourced from any vendor with a commonally available catalog that can be accessed using the internet. Examples are: Allied, Digikey, Mouser, Antique Electronic Supply, Radio Shack, Edcore, Antek and Parts Express. Components purchased from Ebay vendors, are prohibited. 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. 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,
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 $200, it will be disqualified. One approach is to design for $190 which would allow $10 headroom for price increases. Do not use 'sale' prices.
10. Just for the fun of it, the case should come from Ikea. Be imaginative. When we were first thinking about this competition, we thought the IKEA cost should be included in the $200 but on second thoughts, it would be more fun to see what our imaginations can come up with. So spend what you like on the IKEA stuff for the casework, but no IKEA stuff is to be used for electrical purposes.
11. All amps shall be evaluated using the same tubes, preamp, cd player, speakers. We currently expect to listen to the amps at Steve’s place in Stirling, VA using his 95db efficient Econowave speakers with JBL 14A woofers and the Selenium D220 wave guide loaded drivers which are 8 ohms. At our last meet, we felt that the JBL was not quite efficient enough so we may change the woofer.
12. The speaker cables will use banana jacks to allow easy changing of amplifiers. You should include full function binding posts. RCA jacks will be used for input.
13. All amps 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.
14. We will provide a simple prize, possibly some little plate you can attach to your amp that you can treasure for the rest of your days.
15. We are still considering how to judge the entries. The following may change prior to April 11.
- As much as possible, the same setup and positioning for all equipment(CD player/DAC/Foreplay/ speakers/cables/power cable) including positioning of the amp 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 with some kind of sound meter in a fixed position.
- All amplifiers to be invisible to the audience, even while not playing.
- All amps will be numbered. The order of playing the amps will be drawn from a hat.
- One designated person to be responsible for hooking up each amp. This person will not take part in the scoring.
- 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.
- The scoring system is not yet finalized but a sample can be seen here
- There will be a preliminary round where all amplifiers are auditioned. The top three amps will go on to a final round with a different music selection.
- Each of the three members of the organizing committee will select two short tracks (or excerpts)for each of the preliminary and final rounds. If there are a lot of entries and we are short on time, we may restrict the number of tracks to be played. The list will be published prior to the competition. Between us, we will cover different styles of music.
|John's winning entry used a cake pan.|
In the schematic, The power transformer is an Edcor XPWR013, L1 & L2 are the primary & secondary of the Edcor GXSE10-8-5k
|David's entry used a wooden tray and pencil holders|
|Fritz's entry used a child's push trolley. The amp is on the lower level and used a Dynaco chassis with the cover not shown in the photo. Fritz also mounted his linestage on the upper level, which is really clever.|
|Jim's entry used a tray. The amp was working the night before but there was a problem with a capacitor that affected the small input tube.|
|Joel's entry used a cake pan|
|Ray's entry used a candle holder.|
The second photo shows the lightbulbs glowing in the dark. The amp worked fine during the warm up test and then failed for the first time since the amp was built. The cause of failure was a screw to hold one of the 2SK3564's to the heatsink had loosened with all the jolting on the trip down. I now use a dab of nail polish to keep the nuts tightened.