18W Express?

[shipwreck]

What are the main differences (apart from reduced output) between a half- and full-powered TW Express? Will it be significantly cheaper to build an 18W Express (smaller transformers), or not really?


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[M Fowler]

The 18w/15w will be slightly lower priced.

The perceived volume loudness to your ears will be darn close, meaning that little amp puts out close db levels.

It all depends on if this amp is for church, home jam room, garage band or if you play out in a band but mic the cab.
The 18w will get drowned out in some bands.

Will it be significantly cheaper to build

No it will not be much cheaper.

[shipwreck]

Thanks for the reply (and btw, thanks for suggesting rj guitars to me in a thread over at the TDPRI forum).

The amp is for my home jam room.

Are the break-up characteristics similar as well? And is the wattage reduction simply achieved by losing 1 preamp tube and 1 power tube? Is there a layout and a schematic for this version?


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[xtian]

I coined the name "S'express" for small express. Here is my build log:

http://ampgarage.com/forum/viewtopic.php?f=1&t=24904

It came out great! But I have no experience with a real Express, so can't compare.

[M Fowler]

Thanks for the reply (and btw, thanks for suggesting rj guitars to me in a thread over at the TDPRI forum).

The amp is for my home jam room.

Are the break-up characteristics similar as well? And is the wattage reduction simply achieved by losing 1 preamp tube and 1 power tube? Is there a layout and a schematic for this version?


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Your welcome for the rjguitars tip he is a friend of mine.

Same preamp tubes (same circuit) only the output tubes and component values are changed.

Has same breakup as the big brother.

[redshark]

An 18 watts express is really an 18 watts Liverpool ain't in?

The express as it is already has 2 versions depending the power tubes used....22 watts using 6V6's and 35 watts using EL34's.

[pompeiisneaks]

An 18 watts express is really an 18 watts Liverpool ain't in?

The express as it is already has 2 versions depending the power tubes used....22 watts using 6V6's and 35 watts using EL34's.

Not really there are some pretty significant differences between express and liverpool. Express is fixed bias, liverpool is cathode, there are some component differences, differences in tone stack, etc.

They may be subtle differences, but they seem enough to me to make a tonal change.

~Phil

[Phil_S]

The express as it is already has 2 versions depending the power tubes used....22 watts using 6V6's and 35 watts using EL34's.

As I recall, it suggests this on the schematic. I took mine down a notch by using 6AQ5's and reworking the power supply for lower plate voltage. As I recall, it came in at about 330V, which seems to suit the power tubes nicely. I'm using a pair of ANOS Sylvania.

[Littlewyan]

If you do cut the output power then don't forget to adjust the NFB

[RJ Guitars]

Seems like the TAG Team understands very well that the wattage vs. volume equation isn't linear (literally). A half power Liverpool still wreaks havoc on the eardrums and it feels like it's putting out more than it really is.

I know I am stuck like a broken record (remember when that metaphor made sense) when it comes to low power TrainWrecks. The only path I really like is to build them as low power as you can - which is usually still really loud - then attenuate them down to something usable. For cutting back the output level in an Express I like the 6BM8 tube or another of my favorites is the 6Y6GT. The 6Y6GT isn't a lot different sounding than a 6V6GT (IMHO) but they are a much lower B+ tube... so maybe they are like a power scaled 6V6 amp but I think they actually sound better than that - maybe because they were designed to run at a lower B+ voltage.

I know a lot of folks like VVR and others like the various MV schemes but none of them have the tubes working really hard which I think is key for the Express to preserve it's attitude. So with either of those solutions I find as the volume approaches reasonable the magic typically is already going toward zero. Even with an attenuator there is a lower sonic limit that has more to do with how speakers work and how our ears process musical sounds. Cool physics but not so cool otherwise.

So a low power Express is the search for the Holy Grail... it's kinda hard to find but even getting close feels pretty good.

[shipwreck]

My main loudness limitation is my own ears. I guess an attenuator to take the volume down a notch or two, plus a set of ear protectors is where I will begin my grail search.