Killer ant mod

[bigdaddy]

I was playing the Killer Ant and was like wow this amp sucks. So I thought maybe I should sell it on ebay to recoup some money. Well good idea but who's going to bring it to the post office or fedex?.......I can't.

So I'm stuck with it. I tried some different tubes and a 5751 in V1 and a 12AY7 in V2 sounded best. Still not a very good sound and I tried a lot of speaker cabs, the LOPO line with the Emi Copperhead was best. So I opened it up and just cut some resistors off the cathode follower fixed tone stack and that helped too. OK time to rest and save it for another day. Last night I was feelin' not too bad and sitting here at my PC, I looked at the schematic. I was like boy this is exactly what I would not do for an SE amp like this, maybe they know more than I do, of course they do that's why the amp sucks so bad.

I totally removed the cathode follower and hooked up a .022 cap, 220K to ground and a 3.3K grid stopper. I tried it and what a difference, the blanket came off and a lot of the honky mids disappeared. I changed to a 12AY7 in V1 and a 12AT7 in the V2 power stage. It sounds pretty good now, like 100X better. Almost usable now. So when I get a little window of time I might add the tone stack in between the two halves of V1 and use a 12AX7. I bet it would then sound great!!!!! It sounds better than the Bitmo modded ones on Youtube now for sure and those didn't sound too bad. I can hear the over saturation in the preamp, that's why the 12AY7 worked best. The amp was designed to keep the power tube alive for a long time and to get all the distortion from the preamp, bad design, terrible.

If I had the ability I would make kits for this amp. In the future I might try paralleling the triodes of V2 but I just don't think I have it in me. I can only do a little at a time. If I can get it to sound descent I'll be happy until I get the Studio 2 watter from Jeff Bober. Maybe I should just leave it and be happy it's at least playable. I fear if I start ripping it apart and I get sick again it will never be usable. But I think there's a pretty good sounding amp hiding in there....

[BnATX]

thanks of the info. I built a "killer ant" style amp before the killer ant was released. i thought mine sounded pretty good. I plan to go back to it and build another one day. I have this thing about really wanting to use a 12ax7 for an output tube. Whenever i might have a question regarding that i always get the standard, "there are better tubes to use" and " that won't work very well" 
But i 'm  a noob and i don't know any better. 

I think i read that you live in an apartment so not sure if this helps you any, as USPS has limitations on what they do. But i can get USPS to pick up a package for free at my front door. I live in a house though so as i said, not sure if they will do that at an apartment complex.
We only have one vehicle and the wife pretty much has it all the time so that is how i ship priority packages when i do ebay and what not.

take care

Billy

[PRR]

> this thing about really wanting to use a 12ax7 for an output tube. Whenever i might have a question regarding that i always get the standard,...

There are better tubes to use.

That won't work very well.

Why?

Power is voltage times current. To get POWER you want lots of both.

Impedance is voltage divided by current. Speakers are low voltage and huge current. Far more current than any tube. So we use transformers. But even a transformer can't be made for very high impedance and good audio bandwidth (bass to treble).

The 12AX7 is a very low-current tube. It can't make power, and it is a poor match to a transformer.

Ideally the load impedance is greter than the tube plate impedance. If you violate this, both gain and power output are low. We can find a 15K OT. 12AX7 plate resistance is more like 60K. Bad match.

{Historical note: You can have gain or current, not both. The General Purpose triodes like 6J5 and 12AU7 were made with just as much gain, Mu=20, as could be used with a transformer. The high-gain tubes (6F5, 6SL7, 12AX7) give-up the good match with transformers to get higher gain in resistance-loaded stages.}

But you don't know any better.

Get a 300V DC supply, well-filtered, and the highest impedance SE transformer you can find. The Fender Reverb 022921 is suitable and sells for $18.00 here. Use a 470 ohm cathode bias resistor. The "power" output will be about 60mW or 0.06 Watts (at 8% THD; 100mW at 10% THD). 1/100 the power and 1/10th the loudness of a healthy 6V6 Champ. Less power than a 1963 pocket transistor radio.

Yet we annoyed our parents with those bitty radios, and they would be a lot more impressive with a "real" speaker instead of the cheap 3-inch in Camel-pack "cabinet".

Use the other half of the 12AX7 as a conventional preamp stage, sensitivity is adequate. You could put a volume control between, though at this power level that may be silly.

Total power drain is 5mA at 300V DC.

[bigdaddy]

I know people will disagree with me but every SE amp I have tried and built having the TS before the power tube makes for a poor sounding amp(one reason those Galaxie 10 Epiphones sound so bad). When it's coming from the plate the sound is so much better especially without the TS. I mean I tried SO many different configurations and tubes. Not as many as I wanted because I found the best sound is a constant for me in certain design parameters. Like Driving the power tube from the plate of a triode or pentode without a TS.

Just a .022 cap a resistor to ground and a grid resistor. The resistor values depend on the power tube. But I even tried a whole bunch of cap values and no matter what,... my ear always went back to the .022. It just seemed like that allowed the most musical and balanced tone for guitar no matter what speaker cab I tried.

Now as for guitars, I'm talking about I have almost 20 guitars I built with ALL kinds of pickups and wood so when I test something it's using many different pickup types and outputs. I have Lollar, Klein(new guy), Fralin, Duncan, Duncan custom shop stuff I designed and I tried a bunch more I discarded like Rio Grande, Kent Armstrong and so on.

I also think there is an inherent lack of tone in a 12AX7 as a power tube. Because it's not meant to be one. The best small dual triode so far is the 12AT7. I always thought the 12AT7 sounds horrible, to me it's kind of a mechanical tube that does mechanical type duty like phase inverters and reverb tubes. When I tried it in preamps they just sounded flat. The 12AY7 seems to work OK as either. I haven't gotten to the 12AU7, I wanted to check that out as well as some more octal types like using the 6SN7GT as a power tube. I read that is a great one. I could have done this for another few years to get all my ideas working and moving into the mini watt territory was a real challenge, but oh well.