Asteroid/TrainWreck Gain Level

deuce42 · Post by **deuce42** » Fri Mar 06, 2015 12:55 am

Hi guys

Maybe a silly and naive question but how much gain (in practical terms not tech or electrical terms) is normal on these circuits?

On my build I'm finding that after my volume gets above 3 I'm kind of overdriving and getting rough. Having never owned or played a TW or Asteroid equivalent, I had assumed that these amps would be a little cleaner - or at least have a bit of nice chimey headroom before getting into overdrive territory.

I'm trying to understand if I've made an error in my build or whether a higher gain rocking amplifier is just the flavour of a circuit like this. Maybe I was just assuming a bit more Fender-esque than Marshall-esque at lower settings

Cheers

AcornHouse · Post by **AcornHouse** » Fri Mar 06, 2015 2:58 am

What is guitar volume on? They're very control sensitive. Use your guitar volume to float between cleans and crunch.

deuce42 · Post by **deuce42** » Fri Mar 06, 2015 5:19 am

Well that's another issue - I'm even finding my guitar volume starts overdriving at about 2.5! Its only slight grit there and by 5 I'm in plexi rhythm style territory.

I'm just unsure whether it's the build or just the nature of the beast.

bcmatt · Post by **bcmatt** » Fri Mar 06, 2015 5:27 pm

What kinds of pickups and guitar pots are you using? Are they pretty high output pickups?
Even with low output vintage style single-coil pickups, my liverpool and express will not stay clean above 1 on the gain knob if my guitar volume is all the way up.

On the other hand, I can run the amp at noon, and get quite a spanky clean at 5 on the guitar with P90s, 57 Classic HBs, and Strat pickups.
But then again, the taper of your guitar pots really matter to achieve this effect. Without Gibson Historic Pots on the humbuckers and P-90s, it's hard to find that clean on the guitar knob before you lose the signal completely.

geetarpicker · Post by **geetarpicker** » Sat Mar 07, 2015 3:41 am

What he said. I couldn't have said it better!
GK

geetarpicker · Post by **geetarpicker** » Sat Mar 07, 2015 3:45 am

Here is another observation of my original Express amps, regarding the [b]pots in the amps[/b] themselves. I had posted this on another forum but will copy it here. Point of my post was to mention that the amp gain itself can seem higher (in regard to typical knob position, if there is such a thing) due to the taper of the amp pots.

__________________________________________________________

"I'll mention one something I've noticed with my original Ken built Express amps.

The pots Ken used were fairly cheap basic parts, however he was quite good at selecting pot models that had very smooth tapers even in a fairly high gain circuit. For example my '85 Express is barely playing when it's up to about 2, is still clean on about 4, then 5 to 6 gets moderately gainy, but there is still a big change in gain going from 6 to full up. Heck even 3/4 to full up is a noticeable change. This is with a stock Express circuit that is no different than what most clones use today, and with all typical gain 12AX7s in V1, V2 & V3. I did some investigating on the volume pots on my '89 and '85 Express and noticed yes they are obviously "analog taper" but tend to be quite exaggerated in the smooth slope, especially the volume pot in my '85 Express. For example that volume pot measured out quite a bit passed 1 meg overall, but when 1/2 way up the measured value was only at 80k being not even 10% of the full on value. I've measured other "analog" taper pots made these days and just about all of them ramp up more quickly. It seems "analog" tapers pots are not all created equal, not even close.

Ok, all that to say if you build a clone and the volume control seems like a light switch you might try swapping out the volume pot for something else. You might even try some old NOS parts as slower rising tapers seemed to be more common with older production pots a couple decades back at least. Note how 50s Gibson guitars have quite slow smooth taper pots, it seems like it was more the norm back then. Anyway having a very slow rise of the amp pots makes the controls much easier to dial in, even with the stock Express circuit. Oh, also having a slow rising taper on the treble control will also make a big difference. I know this sounds like something you could just compensate for by not turning up the knobs so far, however with slower rising taper pots it spreads out the sweet spots making variations in sound much easier to find.

GK"

deuce42 · Post by **deuce42** » Sat Mar 07, 2015 11:05 am

Well this is pretty enlightening guys. The volume pot matters are particularly intriguing and I might start experiment on the guitar pots.
Good to know at least that my build is not impaired in some way:)

martin manning · Post by **martin manning** » Sat Mar 07, 2015 12:36 pm

Not to be a terminology troll, but audio taper pots are called "log" as a short form of logarithmic. I suppose they are an analog for human hearing sensitivity, though.

Thanks once again for sharing your first-hand knowledge of the real deal, Glen!

RJ Guitars · Post by **RJ Guitars** » Sat Apr 18, 2015 1:57 am

My first play through a DIY Express had me thinking I put it together wrong - it just had no clean headroom. It took me a few builds and a lot of playing hours before I came to recognize and embrace the formula for clean sounds. Previous to these experiences I typically kept my guitar volume on 10 and used a pedal for overdrive.

After playing through a few different Express builds and a few more Liverpool's I eventually began to acquire the fine art of finessing the combination of guitar and amp between clean and dirty. It wasn't just the hardware either... I now appreciate what folks are talking about when they say "touch sensitive". One of the funnest places to play an Express is on the edge of the clean/Dirty transition and push it hard to break it up or back off to "hear it ring"... sounds like a good name for an album?

Now I tend to like to use the guitar volume control between 3 and 7, seldom using the max setting unless I'm really trying to make a statement. YMMV

jazzbass · Post by **jazzbass** » Mon Apr 20, 2015 7:27 pm

RJ Guitars wrote:My first play through a DIY Express had me thinking I put it together wrong - it just had no clean headroom. It took me a few builds and a lot of playing hours before I came to recognize and embrace the formula for clean sounds. Previous to these experiences I typically kept my guitar volume on 10 and used a pedal for overdrive.

After playing through a few different Express builds and a few more Liverpool's I eventually began to acquire the fine art of finessing the combination of guitar and amp between clean and dirty. It wasn't just the hardware either... I now appreciate what folks are talking about when they say "touch sensitive". One of the funnest places to play an Express is on the edge of the clean/Dirty transition and push it hard to break it up or back off to "hear it ring"... sounds like a good name for an album?

Now I tend to like to use the guitar volume control between 3 and 7, seldom using the max setting unless I'm really trying to make a statement. YMMV

Hi RJ, ok for the "touch sensitive" but after 11 the Express than i build with a Ceriatone Kit is quite unusable. I'm agree that with the use of a riverse logaritmic pot is easier to set the level before crunch but.....Who sales this Kindle of post?
Thank you

RJ Guitars · Post by **RJ Guitars** » Mon Apr 20, 2015 9:25 pm

I'm going to be the first to admit that I don't know a lot about Ceriatone builds. I have one of their Output trannies here and have listened to it a little bit but that's about all i have experienced with them.

Glen's report on the extra volume from the Ceriatone seems like it could line up with your report. I did find with the Mercury Stancor A-3801 clone OT's that they had a little more headroom than the other choices so output trannies definitely matter.

It would be interesting to make up a full voltage comparison between the Ceriatone and what we believe are the original Wreck values. Then maybe look at the various component differences - values and brands of resistors and caps, etc.

jazzbass · Post by **jazzbass** » Mon Apr 20, 2015 10:32 pm

RJ Guitars wrote:I'm going to be the first to admit that I don't know a lot about Ceriatone builds. I have one of their Output trannies here and have listened to it a little bit but that's about all i have experienced with them.

Glen's report on the extra volume from the Ceriatone seems like it could line up with your report. I did find with the Mercury Stancor A-3801 clone OT's that they had a little more headroom than the other choices so output trannies definitely matter.

It would be interesting to make up a full voltage comparison between the Ceritone and what we believe are the original Wreck values. Then maybe look at the various component differences - values and brands of resistors and caps, etc.

Great RJ, at the end of this week I refit the Express after the cut of of all the canges I have made to try to tame without significant success. Originaly, before my changes, with the volume pot between 9 and 11 amplifier sound very good but went from a good clean too low to be usable live to a good distorted sound, after that is unusable.
As soon as I finisced the refit I will post the voltages chart.
The schematic used by Ceriatone is substantially equal to the KF Kelly except for: insertion of resistors 2k2 ohm on V1b grid and 820 ohm on V1a grid and R11 LTPI changed from 10 k ohm to 22 kohm.
Greetings
Franco

jazzbass · Post by **jazzbass** » Mon Apr 27, 2015 10:16 pm

"The pots Ken used were fairly cheap basic parts, however he was quite good at selecting pot models that had very smooth tapers even in a fairly high gain circuit. For example my '85 Express is barely playing when it's up to about 2, is still clean on about 4, then 5 to 6 gets moderately gainy, but there is still a big change in gain going from 6 to full up. Heck even 3/4 to full up is a noticeable change. This is with a stock Express circuit that is no different than what most clones use today, and with all typical gain 12AX7s in V1, V2 & V3. I did some investigating on the volume pots on my '89 and '85 Express and noticed yes they are obviously "analog taper" but tend to be quite exaggerated in the smooth slope, especially the volume pot in my '85 Express. For example that volume pot measured out quite a bit passed 1 meg overall, but when 1/2 way up the measured value was only at 80k being not even 10% of the full on value. I've measured other "analog" taper pots made these days and just about all of them ramp up more quickly. It seems "analog" tapers pots are not all created equal, not even close."

GK"[/quote]

Hellow to everybody,

tomorrow i'll finish to refit my Express and then I measure the voltages but...I have an Idea reading of what write Mr Geetarpicker about old pots in original TW Express. Logarithmic pots are not all equals, there are logarithmic and reverse logaritmic or "C". Maybe this is the solution and this is what Ken Fischer had used ?? who knows....I'll buy some 1M "C" pots and give a try. Rolling Eyes

geetarpicker · Post by **geetarpicker** » Tue Apr 28, 2015 1:07 am

The "1 meg" volume pot in my '85 Express measures pretty high at about 1.3meg wide open, but only measures about 80k on 1/2. This nets quite a range of control down in the end of the dial where most folks like to play these amps. I'm not sure if there are many "audio" or "log" taper pots made these days that are only 10% value at only half way, let alone below that. Anyway, Ken found some pots that really worked well with his circuits, but it seems that in general higher value (500k, 1 meg, etc.) pots are quite hard to find these days with similar taper. I think a pot that spreads out that first 10% of value over a wide range will make for a more user friendly amp that won't seem nearly as touchy gain wise. Perhaps others can measure some readily available current production pots to compare? Remember, I'm not talking an over all ohm value nor 10% ohm tolerance. I'm talking about charting out the taper of the pot, or at least ball parking it with a 1/2 way and full up measurement .

jazzbass · Post by **jazzbass** » Tue Apr 28, 2015 9:23 pm

Hi Geetarpicker, look at this please:

http://www.ebay.fr/itm/1M-Reverse-Log-T ... 19fcaf0a09

Maybe this is the solution !?

Greetings

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