Killer Ant arrived

[bigdaddy]

OK so FedEx was here and the Killer ant arrived, all 1 watt of tremendous power!!!!!

I plugged it into a Lopo line 1-10" cab with an Eminence Copperhead speaker. Jacked it to max and played...too much distortion to the point of over saturation sounding more like a Big Muff. So I backed off the volume and about half way. I found a sweet spot, very fenderish but more like a hotrodded fender which is what I like. So I although skeptical at first, I was very pleased with the tone and sound. I will try different cabinets to see if the sound changes with different speakers.

As far as the volume, it was loud in the room. Not as loud as the 6K6GT champ I made, to my ear about half. The thing was that it did not push air. I think the big problem is sympathetic vibration causing other surfaces to act like speakers. By moving air and with the sound waves hitting surfaces hard it causes sympathetic vibrations. This amp does not put out those deep tones and sounds, more like what you would hear a guitar on a CD not like a live loud amp cranked. I think I am in the right direction and need to add more sound proofing and finish the isolation area in my bedroom.

In fact I am going to build one of these amps soon. I am going to cut down on the preamp gain which was way too much and only use one 12AX7 with a tone stack(it uses a more Marshall like preamp with a fixed tone stack). Since the OT has a 50K primary I think I will use both triodes of a 12AX7 or 12AT7 in parallel and use a Fender reverb transformer which has about a 22k primary and 8 ohm secondary, that should work for, am I correct about that?

[bigdaddy]

I tried it with a small Marshall 1-10 cab with a greenback 10" speaker. Lower output but more Marshall tone. Nice...

This amp really needs a tone stack and I can't put it past a little more than half without it really over saturating. So it's designed a little strange, a Marshall type preamp with a CF fixed tonestack into a 12ax7 triode SE power amp. I'll try to post a schematic of the Killer Ant.

I ordered some transformers to build my own version. What I intent to do is use 2 12ax7s, one with a typical fender preamp then into paralleled triodes form the second 12AX7 for power. I'll be using a fender reverb transformer as an output tranny. So basically my version is a BF Champ with a power section using paralleled triodes.

The killer ant has about 275v on the plate for power and the tranny has a B+ of 300v. I'm using a 250-0-250 tranny with a 5Y3. The bias resistor is 1.5K, would I use a 750R for 2? Also how do I bias this amp. I'm spoiled by using a comubias, how do I bias a triode for power in SE operation?

Is the 12AX7 3 watts max or 2.5 watts, I have read 2 different data sheets.

[plexi50]

I have always wondered what a 1-2 watt amp would sound like.

[loogie]

I have always wondered what a 1-2 watt amp would sound like.

I'm rather fond of the cheap old All American Five amps which I can't believe are much more than a couple of watts.  I have an Alamo Capri that sounds real nice cranked, well sort of nice, and when its dimed you can still have a normal conversation.  I also have a Gregory MkV, yes you heard right, a real Gregory.  One of those will set you back fifty bucks or so.  You know what they say "If you wanna play, you gotta pay".

Bigdaddy, keep your eyes peeled for an AA5.

[bigdaddy]

What got me started on the BF Champ clones was the idea of making a 5-10 watt SE amp sound like their bigger brothers, super reverbs, 50 watt Marshalls and so on. I did it.....a lot of work and expense, trial and mostly error. I did it.....

Now the thing is can I make amps 3 watts or less do it. I already did to some extent by just using a 6K6GT in some of my Champs with lower voltage transformers. It sounds awesome.....but still a little too loud.

I have a few designs, one is the Killer Ant, the other a Firefly and another the AX84 4-4-0.....maybe PRRs 1/3 amp or whatever he calls it.

I saw an amp made by East amps(Jeff Bober from Budda amps) called the studio 2 and it's 2 watts going on 50. It sounded much louder than a 2 watt amp. It uses 3 12AX7s and a pair of 12AU7s for power, I guess it has a real phase inverter and both triodes of the 12AU7 are used for each side.

So you can use the 12AU7 or the 6SN7GT for power. The Fender Harvard looks good too but with a pair of 6SN7s instead of the 6V6.

[bnwitt]

Bigdaddy if you keep this minimalistic bent going wattage wise you're going to have to change your handle to ittybittydaddy.   Sorry, we already have a tinydaddy in here

[tonewood]

I saw an amp made by East amps(Jeff Bober from Budda amps) called the studio 2 and it's 2 watts going on 50. It sounded much louder than a 2 watt amp. It uses 3 12AX7s and a pair of 12AU7s for power, I guess it has a real phase inverter and both triodes of the 12AU7 are used for each side.

So you can use the 12AU7 or the 6SN7GT for power. The Fender Harvard looks good too but with a pair of 6SN7s instead of the 6V6.

The East uses 2 12AT7's not U7's. Sounds great.

I have a Harvard that I would love to be quieter (sometimes). I'd like to hear what you come up with.

scott

[Frankenamp]

<perk>
AA5??
Recapping (one of a few) AA5's and the 'business end' of that is either a 12a(v/t)6 and a 50C5, or a 12SQ7 & 50L6 (earlier)
and a 50DC4 rectifier ... makes me wonder... if something similar can be made for guitar?

[bigdaddy]

So I do have a few options as far as design and power tubes. I think I'll stick with the fender style preamp as it seems to do me good so far. If I want to build higher gain models with SE designs I'll go with a pentode like the EF-86 and 5879 which have worked very well in my other builds along with a the 6SJ7. I'll see what the push pull designs respond to.

I think the Killer Ant suffers from the tone stack before power tube SE syndrome. It kills the feel of the amp for some reason. I think the power tube in an SE amp just wants to see the end result and not variables. In a push pull amp you have the PI. In SE amps there is no PI and the driver section is best fixed for the best tone, IMO. Yes it works having a tone stack before the power tube but every amp I have had or heard loses something. Like the Killer Ant the Epiphone Galaxie 10 amps had similar issues with over saturation and lousy tone. The 12AX7 was driven too hard and the tone stack was before the power tube. Since the tone stack is fixed in the killer ant some of the issues are not as noticeable. But it does have that over saturated sound if turned up past about 1/2.

[JB]

I've been playing around with low power SE and push pull designs for a while now.  This is aimed at a neighbour friendly home playing/recording amp, and a slightly louder version for use at jam nights at a friends house (with drummer).

I tried the firefly, and developed it into various other incarnations of 12AU7 push pull output stages.   I thought LTP driven sounded better than the fireflys' self split method.

Ultimately though for me, playing blues, blues/rock and hence looking for not too over the top mostly output stage distortion, I've found small power pentodes to sound better than a triode based output stage.  I'm currently using EL91's (6AM5?) in both single ended (just over 1 watt) and push pull (about 4 watts) designs.  Millitary numbered Mullard manufactured NOS EL91's are plentiful and cheap.  I've also tried single ended ECL82 (6BM8) which also sounds good.

1 Watt (clean, before clipping) into a typical 10 or 12 inch guitar speaker is still 95dB+ (I use a single EVM12L in an open back cab) so plenty loud at home, and sometimes too loud for neighbours. I've had no complaints but a very nice old lady lives next door and don't want to annoy her.  I've used VVR and PRR's variable screen idea on both these amps to wind the power down a bit with success (and similar sounding).

My current single ended version uses EF86 into Marshall style ECC83 gain/CF stage, then tonestack and output.    I don't find a tonestack immediately prior to the output stage to be a problem.

I'm now experimenting with adding a single ECC83 driven reverb into it.

Lots of fun, and good guitar tones, to be had at lower powers. 

[bigdaddy]

Have you tried the 6SN7 for a power tube? I have seen this being used in a few designs.

[JB]

Have you tried the 6SN7 for a power tube? I have seen this being used in a few designs.

No.  I've got a couple and seen designs using them (the Moonlight?) but not tried them.  The only triodes I've tried are ECC82/12AU7.  I diverted into small power pentodes at that point and am still using them. 

PRR's third watt using a 6AU6 as an output stage is good for a bedroom rock sound but I couldn't get any useable clean sounds out of it - wound down to clean my strings were louder than what was coming out the speaker!  I also found the fender reverb transformer a bit lacking in bass.  Not a problem for its intended use but you may find it a bit light when driving a guitar speaker.

[bigdaddy]

I also ordered a Hammond Push Pull 125 model that was used for SE operation in the past. It has a lot of taps to get the correct impedance. I'm not big on lows with my guitar sound and it's the lows that make everything vibrate in this building. It was built in the 60s and was poorly designed, built and there was a lot of rebuilding because of a fire before we moved in many years ago when I was a teenager.

This is going to be an interesting endeavor. I think the more you try to make it sound like the larger fender and Marshall amps the louder it will get. So the trick is to keep it from going that direction. Adding VVR, power scaling even a little attenuation might just do it......I'll find out for sure.

I say that because listening the the East 2 watt amp tells me 2 watts might be too much, that amp screamed. I like the idea of being able to turn my guitar volume down and having the amp clean up or using a lower output guitar without pedals yet have it drive the preqamp a bit. All my SE amps do that now. Can I get 1 watt amps to do that? I'll start with the 12AU7/12AX7/12AT7 and 6SN7 tubes in both SE and PP and see what I have. Then maybe try the pentodes. Too much stuff all at once is confusing....I still have to figure out how to bias these amps. I relied on a meter and not the math.

[plexi50]

I love the 6SN7 & 6SL7 tubes. There smooth sounding

[JB]

I'm using a 125C in my little push-pull amp and it's very good.  Also I use a 125BSE in the SE amp.  Fewer taps on that one.

I think you'll find 1 Watt is plenty and you may have to knock it back a little depending on speaker efficiency and how sensitive your neighbour is (I read your post on that, you have my sympathies).  I find VVR and PRR's screen voltage reduction to be the best.  Attenuators, beyond maybe 6dB, have too great a tonal impact for me - though I've only tried simple resistive or reactive ones, not the weber mass idea.

My SE amp measures just over a watt and I can roll between plenty loud enough clean to crunch and beyond using the guitar volume.

[bigdaddy]

I did order the weber mini mass. It was interesting, designed for 15 watts max. But instead of a volume control it has 2 tone controls. One is treble-mid the other bass-mid you dial in how much of each. That appeals to me from poor experiences with nonadjustable tone circuits.

I should have that unit in a few weeks and hopefully it will help not having to tear apart so many builds already done and working.

[zendragon63]

There is definately a diminishing return on 'tone satisfaction' as you drop below 1 watt. IMHO the speaker choice makes big, big difference here but ultimately it will be the one that floats yer boat.

bigdaddy, don't overlook the 6AK6. Plentiful and reasonable last I looked. About 1 watt each of pentode sound that sounds pretty good in triode mode as well. Runs ~10K OT SE so a Hammond 125 would accomodate nicely. So many options, so little time... Reagrds

dennis

[bigdaddy]

Yes I have been also looking at the 6AK6 also and that is probably were I'll end up. It's a process and a learning curve until you get there.

I just messed with the ant again and I cannot get it to clean up at all. Like I said the 12AX7 is being over saturated and the the 12AX7 power section is not being driven probably for tube life issues. My design is the fender preamp driving both triodes of a 12A_7 in parallel SE. I should have some transformers Tuesday.