The Hundred-Buck Amp Challenge

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Joined 2004
Thanks for the positive comments Jazbo8 and djgibson51 - I always like compliments if they're coming from reliable sources (employees and women are NOT reliable sources). :) For English speakers 'Mira qué mono' means 'look how cute!' (he even nailed the accent).

Just wanted to say I'm working on it (schematic and clips) but it may take some time. This time I might do some editing (just for fun), I have new software but I must first learn how to use it.
 
Not really sure if it should be posted in the $100 amp thread, I have not looked up the equivalent parts, but I think it would be a little over. Uses a 4W line transformer which I think will be good for the 6AK6's. Design sort of follows a Marshall 18 Watt direction. Using some nifty DPDT switches that operate normal in the end positions but the center position splits the terminals selected. Use it to select one channel, both, or the other. Also to give the shared cathodes 820 ohms, 820 bypassed with 22uF, or splits then with 2.7k and 0.68uF for the other. Next a cascade option to run the one channel into the other. Normal Tweed type volume and treble, have a switch to short across the mixing resistors to see if I can get some 5E3 interaction. Probably about 200v on the 6AK6's, will double the voltage for the preamp. Negative feedback switch and using a DPDT I may add some presence. Just a working copy, will need some tweaking.

6AK6amp-1.jpg
 
Well, apart from me being at the bottom of the barrel sharing places with Costis and Johnnyeye *cough cough* I think Wavebourn left the game too early, I'd swap him with.......(can't remember his name), the one who builds guitars and posted a few recordings. Australian I think. Probably my 'peculiar' sense of humor put him off so I'm feeling a bit guilty. Never seen again.

I removed that videos from public access on youtube after somebody left a rude comment. It reminded me a saying, "Never show half done work to well done fools". ;)
 
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I removed that videos from public access on youtube after somebody left a rude comment. It reminded me a saying, "Never show half done work to well done fools". ;)

No moderators on YouTube huh? :D If you go public you must accept the good things and the bad things. Internet is just like life: plenty of fools around. Anyhow you got 100 dollars worth of parts waiting for you. You just have to send an email. I haven't BTW, hope BST isn't offended, I love surprise boxes but having to ask for a gift is kind of .....lame.


This weekend I will make the recordings of my new amp. It sounds very crude, it barks - I love it! Oh God how I hate drawing schematics. This amp has too many parts. :)
 
Rip Van Winkle asks the time and date once again

Anyhow you got 100 dollars worth of parts waiting for you. You just have to send an email.
Hello Everyone, long time no see. I got a heads up from the person I have been assisting via email to build my design (which I have not yet put on the market in my ebay store for reasons I won't go into now) to the effect that there had been some sort of offer made here to those who had submitted useful designs.

Before I ask for a summary of that information, let me first say that this long-distance construction project has been a success, finally, and that the individual who built the amp is evidently very pleased with the results that only became fully realized this past weekend after many days of troubleshooting the last of the snags one typically encounters with novel designs (mine) and untested layouts (his). The worst of which, as it (but of course!) turned out, was a bad tube that had to be replaced after exhausting all the other permutations of possibilities that could be tested by unsoldering things and moving them around.

So I am very happy about that jointly successful working reverb amp, at any rate.

As for my long absence from DIY Audio, I have been trying since January to purchase a home, which, in addition to scraping every available penny out from under furniture cushions, stuffing boxes full of unsorted miscellany, and carting truckloads of them off to a storage unit at regular intervals, has kept me sufficiently busy enough to substantially limit my options for doing other things at the same time. And despite this constant flurry of activity, I am not much closer to success in that endeavor than I was two months ago.

This is why I have not been a regular visitor here. I have been very busy away from the office.

And it never rains, but it pours. In addition to having my personal space literally turned topsy-turvey for the past several months (such that I can no longer find my larger drill bits and other necessities),

it also came to pass last month that my mother, who was very elderly but in reasonably good health, suddenly passed away. This brought its own sudden set of additional burdens and time-consuming interruptions to the usual daily circumstances around here.

The situation as it stands now is such that while I continue to search for success in the housing market, I feel somewhat constrained by a relentless and ever-present sense of needing to keep my nerves taut (which my broker tends to encourage at regular intervals) and my breath held for unnaturally long periods of time (which the lenders seem to feel is good for me), conditions that are overcome only by my own need to keep consuming oxygen and participating in daily routine at least every once in a while.

It is only thus to be expected that almost every time in the last three months that DIY Audio has come into my mind, it has been immediately preceding a collapse into deep and exhausted slumber.

It is thus only to be expected that for as long as I continue to anticipate having my Internet connection disconnected at any moment to be carried across town and established elsewhere, perhaps in remote regions that have not yet entered the 21st century, I will also continue to be a fleeting and nebulous presence here, but I do want to assure everyone that this is not at all intended to be a permanent condition.

Now, there was a question that I came here to ask, but I cannot just now remember it very well. Or perhaps I already asked it.

Till next time,

--Tubekit
 
No moderators on YouTube huh? :D If you go public you must accept the good things and the bad things. Internet is just like life: plenty of fools around.

It is true, but I got a lesson: to go public with complete product only, properly advertised. :D

Anyhow you got 100 dollars worth of parts waiting for you. You just have to send an email. I haven't BTW, hope BST isn't offended, I love surprise boxes but having to ask for a gift is kind of .....lame.

Thank you, I pass. I have no moral rights to participate in such contest, I am a professional design engineer, taugt in Soviet Union to design and manufacture military equipment.


This weekend I will make the recordings of my new amp. It sounds very crude, it barks - I love it! Oh God how I hate drawing schematics. This amp has too many parts. :)

Good luck! :)
 
Wavebourn, I'd like to replace the guts of a SS Fender practice amp with your 'micro-champ' but currently have no high-mu small-signal tubes. Can I get away with ECC81 in the same circuit while looking for the 'proper' tube (I believe 6n21 has mu of 70 and ECC81 is 60 so not that far away)? I can only find 6n16 on epay - do you have a source for 6n21? Also, did you ever post the latest schematic with the 'patent-pending two-pot trick'?

Ops... Sorry I missed this post.

The schematic is attached. 6Н21Б is similar to 6Н17Б, that is similar to 6Н2П that is similar to 6Н9С that is similar to 6SL7.
6Н21Б has the lowest microphonics among them.

The transformer is 240V CT, so couple of little 120-240/6.3V transformers can be used back to back.

R16 knob is called "Scream".
 

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Boy I am stubborn. Even though I spent hours on trying to get a PI that can switch between Cathodyne and Long Tailed Pair with a four pole switch and came to the conclusion it can not be done (without needing another triode) I spent a few hours tonight beating my head against my monitor because 'damn it, it should be able to be done'. Well I came up with a version that works.

OK not earth shattering but this means that if anyone wants to have the ability to switch between them in an amp they do not have to get an exotic switch, a simple toggle four pole two position switch that you can get for a couple of bucks will do. I had to compromise and use 100k resistors for the cathodyne splitter stage so that I could use the 100k as plate resistors for the LTP. I wanted to do a 5E3 - 18 Watt Lite cross in the same amp, I have switches that would do it with the original component values but I wanted others to be able to do it also. May go back and see if I could get a Paraphase circuit going with a four pole three position rotary switch but for tonight this is good enough.

SwitchedLTP-CathodynePI4P2P.jpg
 
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Joined 2004
OK, here's my stuff. Power supply schematic is not ready yet. The audio file is just a guitar, an amp, a micro and a computer. No editing apart from crude copy and paste. I start clean, then crunchy and then volume goes to 12.

http://www.fileden.com/files/2012/4/4/3287729/717 taking off.wav

More details about the amp with my next post, probably power supply schematic too. This is a lot of work. Both are the same schematic, just choose your fav color (lol).
 

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Spent some time and worked out how to add a floating paraphase PI to the 4 pole switch PI I posted. So a simple four pole three position switch will work (hopefully). I lifted a preamp from the guys at Watkins since I just got the tube in the mail and I want to try out the 25L6 tubes I have. The power supply still has to be worked out, just put some parts in place for the heck of it.

26L6SwitchedPI-3.jpg
 
Disabled Account
Joined 2004
Good luck!

Thanks Wavebourn, I didn't electrocute myself yet. So far luck is on my side.


I see your first cathode resistor says it's 1500k - obviously you meant this to be 1.5k or 1500.

Yes, 1.5K. Big blunder.


If I may ask, to what specifically does the above quote refer?

Read post 1403. Hey you're on the list!
 
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Joined 2011
Spent some time and worked out how to add a floating paraphase PI to the 4 pole switch PI I posted. So a simple four pole three position switch will work (hopefully). I lifted a preamp from the guys at Watkins since I just got the tube in the mail and I want to try out the 25L6 tubes I have. The power supply still has to be worked out, just put some parts in place for the heck of it.

Ah, great men think alike, here is Merlin's version (via AX84):

An externally hosted image should be here but it was not working when we last tested it.


Jaz
 
Disabled Account
Joined 2004
great men


Where to? :D

Power supply is here! I knew you guys couldn't wait so.......

Three more facts:

1. Power supply caps come from a dead PS, a dead CFL and the poly one is made here in Madrid. Proud of being crap, she is.

2. I did use my cheapest speaker for recording. Remember set up is under 100 dolla (guitar not included). It's a Celestion 12, can't remember its name...RockJunior or something. Ported cabinet.

3. Output transformer comes from a single ended radio. It has several primaries (0, 800, 1.6K, 3.2K) Center tap is 1.6K, serious mismatch in resistance, still, I don't pay the hum penalty.


That's all folks.
 

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Ah, great men think alike, here is Merlin's version (via AX84):

An externally hosted image should be here but it was not working when we last tested it.


Jaz
That's what first got me started on it. When I first started drawing things up I could not find the link to the picture and just took a few Fender schematics and started from scratch. Ended up being pretty close to Merlin's schematic. What I tried to change was not having the triodes paralleled up in Cathodyne. In this circuit you need an added triode to get the gain back where it should be. I thought you should be able to do it with the two triodes. I posted at AX84 to see if any were still interested in the switched PI thing and had no replies so I went at it on my own.

I am starting on the last circuit I posted, did a half *** board layout on my favorite (strip board), the software I used does not allow to rotate the direction of the strips, not a big deal. This is just the power amp section, I will have to adjust for part size, just gives me a rough guide. Changed some part values, will change some more when it gets up and running. Schematic should not have the grid resistors on the power tubes going to ground, added the fixed bias switch at the last minute and should have deleted the ground. The top strip is the power, the bottom is mainly ground. The black lines are jumpers and a length of holes next to the HV and ground is cut.

SwitchedPI4PThreePI.jpg
 
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