NEW Trainwreck?

[mojo]

FYI - Just read a thread on the Gear Pages under the Amps section that reports Komet is coming out with a Ken Fisher designed Express style amp called the KF-50. Thought there might be some interest here in that.

[Omar]

Here's the thread:

http://thegearpage.net/board/showthread ... adid=85495

Omar

[Mark]

A lot of fellows with a lot of money over there!

I personally believe that some of the stuff they talked about may happen (the cab idea) but to what extent?
I don't think the cab would make as much difference as other factors within the amp, perhaps Hogy will do some recordings with this new amp to demostrate this effect?

(Sorry to play the devils advocate, but someone has to, this isn't religion.)

A sobering thought I sometimes reflect on is that none of my favourite guitars tones were made using a Trainwreck amp. In fact, I didn't know the amp had any merit till I built a rough clone.

BTW Omar, I thought your clone had the smoothness that I've heard in real Express recordings. I was a little surprised that it didn't have the outragous gain that I have experienced.

[Bear]

Wow. That's markup. I hope Ken is getting a good cut off of that. I'll have to toil in the garage instead, though.

Bear

[Guest]

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[Omar]

BTW Omar, I thought your clone had the smoothness that I've heard in real Express recordings. I was a little surprised that it didn't have the outragous gain that I have experienced.

I'm not sure where they had the gain on the amp, but it can get into some pretty high gain sounds past 12 o'clock.

I got some feedback from the guys at the ampfest that the amp was way too bright. They said that even with the Treble on 0, it was too bright. When I got the amp back I tried it and I have to agree. I'm thinking about scraping the whole thing and trying a build like Jackie Treehorn's since I don't think I can afford the Komet KF-50.

Omar

[Mark]

I was wondering if anyone tried Hogy's cabinet test?

This is Hogy's quote from the Gear page:

"Pureoldsound, if you don't think your head boxes resonate, just touch them with the headstock of your guitar while playing and see what that does".

I did try this with two different guitars on two different amps, at various gain settings.

To be quite honest I heard no difference at all.

I was careful not to be fooled into hearing "something" which was string vibration generated by the headstock tapping either the chassis or the cab.

Has anyone had differing results?

I don't agree that you can compare tapping components with a screwdriver and the effect of the head cab on the tone of the amp.

I have found that the volume level of my guitar is always far greater then the volume of the tapped component.

For the output transformer or speakers to generate even the volume level of the tapped component, I doubt I'd have any ear drums left.

While some effect may be possible, I do feel it would be quite insignificant. Should you have a test that can prove this effect is more significant, then I would love to be enlightened.

Regarding the reason the new FK-50 can only accept EL-34's, perhaps the output transformer impedance is the typical 50 watt Marshall value?

I suppose the question is also what is a Trainwreck?

Is it a production amp, or is it the fact you saw Ken Fischr with you guitar and favourite speakers and he custom built an amp for your needs?

I believe anyone could make a KF-50 if they are all the same, but I was of the understanding that they are all different (with the exception of the Rocket amp, [I'm told].)

Okay, I hope this doesn't sound like a rant, it's more like an enthusist meets a poor man's myth-busters.

[Bear]

Well, all the interaction stuff is supposed to be relevant, but if I'm going to build the tweed Fender circuits, I'm going to be a heathen and build them as heads. Longer amp life, longer tube life, and less fuss about microphonics seem like good things. Besides that, more ease of selecting the speaker rig du jour. Yes, the speaker back wave affecting the circuit can be part of the sound, but I don't think it's a necessary component. I don't think the wood cab is a necessary part of the Trainwreck sound, either, or Hogy wouldn't sell them in tolex.

Bear

[mojo]

Where's Rocket when an emergency arises? Guess I'll have to take a deep breath and do what I can for the good of the online community. Here goes -
Okay Mark, no offense but this is the wreck page its FISCHER not FISCHR!
Did I do okay guys?

[ODwan]

All of the rambling left aside it sounds quite interesting to me. I really would like to know what approaches KF used on this seemingly Express-based circuit to achieve the sound described. My guess is:
Higher Platevoltage for more headroom
Altering the RC-component between the 2nd and 3rd stage for more bass responce
Any guesses anyone???
Again: I want to learn from KF/Komet, not clone...

[Bear]

I was thinking higher plate voltages if it's described as an EL-34-only amp. That also goes to headroom.

The bigger sound/huge bottom description is interesting. I think Ken's TW amps were designed in an era of pretty bright and crunchy hard rock/metal sounds. I wonder if he refigured the interstage LP filtering to dump less bass, but there can be a perceived mushyness if to much bass is left in cascaded gain stages. Another possibility could be going to a more robust OT that'll give more bandwidth and deliver more bass without getting close to saturating the iron.

Very interesting.

Bear

[ODwan]

I was thinking higher plate voltages if it's described as an EL-34-only amp. That also goes to headroom.

The bigger sound/huge bottom description is interesting. I think Ken's TW amps were designed in an era of pretty bright and crunchy hard rock/metal sounds. I wonder if he refigured the interstage LP filtering to dump less bass, but there can be a perceived mushyness if to much bass is left in cascaded gain stages. Another possibility could be going to a more robust OT that'll give more bandwidth and deliver more bass without getting close to saturating the iron.

Very interesting.

Bear

I totally agree on the sound dictated by "era needs". Today the sound everybody likes seems to be a lot more on the bassy side. The trick is to keep that huge bass tight and focused. This is mainly done in master-volume amps by skimming it in the preamp and pumping it up again in the poweramp. NonMV amps are another thing altogether.
The iron: this is the sense in overrating OTs as bandwidth goes down as the transformer nears it's powerrating. Using an iron rated at 100-150W or even 200W in an 50W amp would sure do a lot...
Keep the thoughts flowing!!!
Timo

[Guest]

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[Moose]

I'm not sure where they had the gain on the amp, but it can get into some pretty high gain sounds past 12 o'clock.

I got some feedback from the guys at the ampfest that the amp was way too bright. They said that even with the Treble on 0, it was too bright. When I got the amp back I tried it and I have to agree. I'm thinking about scraping the whole thing

Don't scrap! There's a lot more to it than you think.

First, this circuit is meant to be a LEAD amp, which means cutting through the mix. Remember, upper mids cut, but too much bass or scoop mushes into the mix. As a result, a lead amp should usually be a little more topendy.

Second, this amp is meant for people who do something OTHER than leave their tone control on 10 all the time. Did any of the guitarists at the ampfest roll back any, or did they just leave the thing on 10?

Also, if you want to dial out top end, try rolling back the MID control and listening carefully. The high control -- at least on mine -- seems to add or subtract harmonic content more than fundamentals. Rolling back the mid is necessary to get a less topendy tone.

Third, if you really don't like the brightness, start tweaking to taste. Try some different values on the slope resistor -- maybe a 47K or a 33K or something will tame your treble control. You can also alter the values of the preamp cathode bypass caps. As they stand, their rolloff is under 10hz, so you can't do much, but I've been suprised that LOWERING that value some has made the bass tighter and more apparent. Too much bass headed into a distortion stage causes strange problems, so you might try changing a 22u to a 10u, or even raising it by clipping in a second 22u. Listen after each and do what your ear likes.

And, if you're still worried about bass and punch, EL34s are the sizzliest of the tubes you can use. Try some 6L6 or KT66 and mess a little with the coupling caps on the PI -- both a larger cap on the PI grid if you're not getting mushy or fizzy tones or slighty larger coupling caps on the grids of the power tubes. El34s break up relatively early and don't have as much bottom end, so the distortion character will change a bit. Personally, I like KT66 best of the lot.

Also, consider speakers. I LOVE mine with a closed back 4x12, but find an open 2x12 with a pair of greenbacks is too topendy. The G12H solves that problem by having more apparent bottom end than greenbacks. The cabinet DEFINITELY must be matched to the circuit you're using.

This circuit is remarkably versatile as long as you don't get it in your head that you can build A1A and it'll be a perfect "Clone" of the perfect amp. There's no "perfect" when it comes to trainwrecks, and there's no "perfect" when it comes to amps. Everyone likes something slightly different.

One more note for people who are worried that this is too bright an amp. Try a liverpool instead of an express. I find that power amp to be somewhere between the Marshall mid heavy and Vox chimey in tone. I discovered my favorite EL84 phase inverter values by experimenting with an 18watter and when I was done I had almost identical values to the liverpool. Not too fizzy, not too bright, not muddy, and still extremely dynamic and touch sensetive. Personally, I like what I was able to do with my express, but that liverpool style poweramp I came up with now resides in an amp that tours with a former marshall user (and crate and peavey endorsee -- who pays me instead of taking the freebies) and it walks all over his rhythm guy's DSL.

[Mark]

Okay Mojo, you spotted my typo.

I was a little surprised that there were no remarks about the Hogy's head cab test?

I suppose if you were going for a more Marshall like sound from an Express amp the 2.7K cathode resistor and a 0.68uF cathode bypass cap on the cathode of the first stage is a good place to start. The second to third stage coupling cap would also have to be increased, but then again Ken Fischer did all these kind of things with the Komet.

Hey Rocket, when will we hear a few more details about your amp?