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Old 13th June 2011, 01:38 PM   #11
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Now to decide, simplest, or most bang for the buck.
How about something you (or another guitar player) would want for themselves.

I am planning to dig out as many old breadboard as i can find wire stuff together until I get a sound that I would keep. It's got to be something new and unique. I don't need another "Champ".
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Old 13th June 2011, 01:45 PM   #12
Trout is offline Trout  United States
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Originally Posted by tubelab.com View Post
How about something you (or another guitar player) would want for themselves.

I am planning to dig out as many old breadboard as i can find wire stuff together until I get a sound that I would keep. It's got to be something new and unique. I don't need another "Champ".

I agree, though champs are nice home use platforms, and many sound great, they have been beat to death in variations.
Maybe reverb should be mandatory LOL

Mod Tank from CE 4AB3C1B, 8 ohm input, 2,250 ohm output, long delay.

That should get rid of the dryness anyway
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Old 13th June 2011, 01:48 PM   #13
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I'm not a designer, but I do need a teeny amp, so I'm up as a test builder. What would be really fun would be to set an agreed OP traffo, so the different circuits could be tested without duplicating the expensive part of the build.
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Old 13th June 2011, 02:29 PM   #14
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Sounds fun! Do you have any guidelines for the "prize"? Should this be a winning design for under $100 that is useful and buildable by others? If so, you might want to specify that the parts should be available to most people for a price that keeps it at or under the $100 (USD, right?).

In most loudspeaker DIY design contests, for example, the drivers and crossover parts need to be in stock somewhere for at least a while (even if they are surplus), not one-off custom units, out of stock clearance leftovers, or unobtainium. If someone builds with junkbox parts on hand, the equivalent purchase price is still figured into the cost for the purpose of the design and the contest. The cabinet (in this case, the chassis as well) is not figured into the cost since there can be so much variation. Switches and pots would be priced for a common part.
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Old 13th June 2011, 02:39 PM   #15
ratbagp is offline ratbagp  United States
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Last year our little group ran a similar competition for a 6V6 amp (stereo) housed in a container that came from Ikea.

6V6 Competition

Photos and some schematics can be seen at 6V6 Entries

The constraints are what make the competition interesting. It's not that easy to stay under the $$ limit. Another resistor here and another cap there and soon you are hitting the $$ limit. We really like the idea of using non traditional containers. I wandered around Ikea a few times before I found my container. You can read about my entry here.
6V6 Lumiere

This year we are doing a similar competition for an under $100 line stage based on Russian tubes. The container has to come from Target.
Bottleneck Linestage Competition and Audio Meet - June 18

You can read about my entries here.
Russian Line Stage

The auditioning part of the competition will be this Saturday, so if you are in the DC area you are welcome to attend.

ray
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Old 13th June 2011, 02:44 PM   #16
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What would be really fun would be to set an agreed OP traffo, so the different circuits could be tested without duplicating the expensive part of the build.
I think finding a creative source for OPT's that really aren't OPT's will be one of the deciding factors in the success of the design. It is also a big factor in the "tone" of a guitar amp. Much of Fender's tone comes from using tiny cheap OPT's, while Marshall used rather big transformers. Choosing the OPT up front restricts the tonal possibilities.

I for one will be exploring push pull amps while I am assuming most builders are going SE.

Quote:
Should this be a winning design for under $100 that is useful and buildable by others? If so, you might want to specify that the parts should be available to most people for a price that keeps it at or under the $100 (USD, right?).
All parts should be something that anyone could order, and the total price should add up to less than $100 USD, right?

Quote:
If someone builds with junkbox parts on hand, the equivalent purchase price is still figured into the cost for the purpose of the design and the contest.
I would even go as far as that an equivalent part must be orderable from somewhere in the world and that price should count. I am sure that I could build a 100 watt flame throwing guitar amp head without buying a single part, with mostly free or cheap stuff. That wouldn't be fair to the guy that isn't a compulsive junk collector like me.

Quote:
Wow. Competing against Tubelab and Wavebourn, two heavyweights. I'm chickening out!
The one thing about guitar amps is that the "winning sound" is far more subjective than any HiFi, tube VS SS, full range VS 3 way speaker debate that has been seen on this or any other forum. If the judges are chosen from guitar players, and non guitar players, (a jury of our peers / members) everyone will have a good chance of winning. Besides, I will bet that Trout has made more guitar amps than Wavebourn and Tubelab combined. He knows how to play guitar too.
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Old 13th June 2011, 02:53 PM   #17
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I assume shipping costs of parts will not have to be taken into account.
But if i create an OPT with steel I cut out of soda-cans, do I have to count the price of the soda cans?
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Old 13th June 2011, 03:45 PM   #18
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I think you will need to set some required low frequency response (maybe 40 Hz for guitar?), or the amp/OT will just be a tweeter amp. Real easy to do a 400 Hz and up amp. (use air core even) Similarly the HF end needs some minimum, or the amp will be 1000 Hz limited. And the Watt limit should be taken as a minimum, since its easy to get a couple of $1 sweep tubes to do 50 Watts in P-P. And cheap 480 V industrial/control transformers off Ebay are usually a few hundred Watts at least.
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Last edited by smoking-amp; 13th June 2011 at 03:47 PM.
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Old 13th June 2011, 04:01 PM   #19
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Many guitar amps use the venerable 12AX7. The 12AU7 and the 12AT7 are also common. The only common output tubes that will fit this price and power ranges are the 6AQ5, the 6BQ5 / EL84, the 6CW5, and maybe a Chinese EL34 or 6L6GC. Since these tubes can be found for an extremely wide price spread we could agree on a fixed number for these tubes up front.

The reason that I propose this is the 12AX7 is the defacto standard in guitar amp gain stages. It is available world wide. There are dozens of cheap stand-ins from the TV and FM radio tuner tube selection, but their use immediately limits the target audience because a lot of these are not common outside the US. The ones that are common will skyrocket in price as soon as the winning design gets published.

The output tube choice gets a bit more sticky since the common guitar amp tubes are just too expensive and not really suited to low power / low voltage operation.

If cheap oddball tubes are used, there should be multiple choices, or thousands in stock somewhere to insure a stable supply. Look at what happened when Pete Millett published his red board amp. The 6GV5 was on the dollar menu at 2 different suppliers. Now they are $5 if you can find any.

Quote:
But if i create an OPT with steel I cut out of soda-cans, do I have to count the price of the soda cans?
In this part of the world most cans are made of aluminum.
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Old 13th June 2011, 04:09 PM   #20
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The whole amp could be done with just one odd tube type, like 6LU8, 6LR8, 8AL9, 6AL11, 6AD10, 6BY11, 6T9, 6T10.
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Last edited by smoking-amp; 13th June 2011 at 04:20 PM.
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