Artisan 15 (attenuation)

DCS222

Whilst I know my Blackstar isn’t exactly “the wall of sound”, to fit into my band’s stage sound level, the volume dials on both channels are barely off the start and the tiniest move have have the volume blooming. I’d like to be able to use the amps drive tones better and I’m half thinking about attenuation (but in my world, it’s an expensive road to travel)… so are there any other options I don’t know about… budget friendly as possible???

DCS222

(Note - that’s in 15 watt mode, 5 watt mode doesn’t have the clean head room

Dave_Mc

There's a Harley Benton attenuator for about £60... it's not amazing and sucks a fair bit of treble, but if you're only going down to "slightly quieter band volume" rather than "bedroom volume", it may well be good enough, especially since the amp is only 15W in the first place...

ecc83

If it is "twitchy pots" that are the problem you could try a volume pot in the path between ch 1 and ch 2?

The A15 really does not put out much more than 15W (maybe 20W if you have mains voltage at top tol') so an "L Pad" attenuator rated at 20W should be safe. There are caveats to using such things as I am sure ICBM will explain, meantime I shall see what is about.

How are you with a bit of electronics DIY?

Dave.

DCS222

Thanks both… I appreciate the responses

I’m not adverse to a bit of soldering… I did make a basic fuzz pedal a while back… but I’m not proficient! I wouldn’t like to work (and potentially eff-up the amp itself)

Wouldn’t the volume pot idea stop me using one channel or the other? Mind you, I’m effectively down to one channel now because I can’t drive channel 2 to natural overdrive on its own at that volume pot position.

ICBM

Without an FX loop, an attenuator is the only practical option. As Dave said, a ‘100W’ L-Pad* would be adequate for an amp of this power rating, and is the cheapest - and actually a pretty good-sounding - option. You don’t even really need an enclosure, you could just mount it on a bracket screwed to the inside of the cabinet round the back - they’re air-cooled rather than using a heatsink.

The Harley Benton one isn’t bad either, if you would prefer a bought-in solution.

(*The reason they’re called 100W is historic, but they’re only really suitable for up to about a 20-25W guitar amp.)

ecc83

DCS222 said:

Thanks both… I appreciate the responses

I’m not adverse to a bit of soldering… I did make a basic fuzz pedal a while back… but I’m not proficient! I wouldn’t like to work (and potentially eff-up the amp itself)

Wouldn’t the volume pot idea stop me using one channel or the other? Mind you, I’m effectively down to one channel now because I can’t drive channel 2 to natural overdrive on its own at that volume pot position.

If you own a digital multimeter (Ohms range) you can build a power soak with a 50W, better 100W rated L pad and check the resistance. "Monarco" seem to be the people but others might have their ideas.

50W pot is about 30 quid, you'll need a tin (Ally) and couple of jacks (get insulated types not those 'bent Tin' horrors!)

Even a short for several minutes on the A15 won't knacker it. An open circuit load might if run at full wick but your meter can steer you right there.

If you want to have a go PM me and I can walk you through it.

(With apologies in advance to Impman who may not be enamoured of the idea!)

Dave.

ecc83

I am obliged to my friend ICBM. Yes the 50W L pad would seem marginal so go for the 100W unit. They seem to be about a nifty so you are getting into 'ready made' territory price wise.

Dave.

DCS222

Cheers, the ready made option… is there a website to peruse?

ICBM

Yes, the ‘50W’ L-Pads are really only suitable for amps up to about 10 to 12W, if you’re going to overdrive them - a solid 15W is probably pushing it.

I may as well explain the historic reason! (Dave will know this.) It’s because they were designed as tone controls for old-fashioned “hi-fi” systems - they were used as passive treble attenuators in the speaker cabinets, and rated for the power of the amp being used. But hi-fi signals only contain an average of about half the rated clean power of the amp at most, whereas an overdriven guitar amp can put out up to double it - and anyway the treble frequencies contain less than the full power of the signal. So about a 4 or 5 to 1 difference is a good safety margin, as you don’t want to risk blowing the L-Pad and leaving the amp with no load.

I actually have an old 1950s “hi-fi” cabinet like that, although the treble (and midrange - it’s 3-way, very sophisticated for the time!) attenuation is done with rotary switches and fixed resistors, rather than L-Pads.

DCS222

So where do I get one, or be instructed to make one… I’ll give either route a go

relic245

If you want to make one I have a starting point for you.

When I bought my Artisan 30 about 15 years ago, Dave (ecc83) talked me through building one.

It's scruffy but works. The volume control is wired backwards lol and I never got around to changing it.

The resistors were very much over speced even for a 30 so will be great for what you need.

You may want to just use the components and start again but if you want it you can have it for the price of postage.

DCS222

That is very decent of you, I would gladly accept! Thank you so much. Left me know what you need in the message section and I will sort you out.

ecc83

Relic! I don't remember that! Oh the 'joys' of old age!

Did I send you some files? If so could you let me have them so as to advise our other friend should the need arise?

Dave.

relic245

ecc83 said:

Relic! I don't remember that! Oh the 'joys' of old age!

Did I send you some files? If so could you let me have them so as to advise our other friend should the need arise?

Dave.

Sadly I don't have the drawing you sent me. I have some of our early emails but not the one you attached the diagram to.

Unless you could have used a different email address?

The one I have was started tubeman the a couple of numbers (don't want to paste your email address here)

If it would help I can send you some pictures of that might help to reverse engineer it?

Edit. It was Feb 2011 so don't feel bad that you don't remember

ecc83

I might have the email Relic if you could give me a similar clue to your address?

Dave

relic245

ecc83 said:

I might have the email Relic if you could give me a similar clue to your address?

Dave

I've dm'd you.

relic245

Here is it in all it's scruffy glory  

The screws in the top are because @ecc83 suggested that I used a metal box and screw the big resistors to it as a heatsink. 

The wiring is very scruffy but works - but hey it was 15 years ago and I could do a lot better now  

As I already mentioned the pot is wired backwards and I never got around to fixing it. 

Simple circuit but worked very well on my A30.

It will shortly be winging its way @DCS222 and hopefully he will have some fun with it too. 

ecc83

Relic, I have searched my old emails and found lots to and from us, even found a list of component But NO schematic! Bummer, in that list was a "70 volt" transformer but I can't see that in your photo.

Anyway, that box will easily and safely handle a 15. Fork! Those Gold resistors are 25W each and can stand a 1000% (yep THREE  zeros) overload for 1 second.

I reckon swapping the two blue wires over will sort the pot direction out.

Dave

relic245

I remember you talking about different versions of power soak but deciding to keep it simple as it was my first build.

Maybe you had a rethink before giving me the drawing as I'm certain there was no transformer on there.

If there was then I just got lucky building something without it that worked

ecc83

relic245 said:

I remember you talking about different versions of power soak but deciding to keep it simple as it was my first build.

Maybe you had a rethink before giving me the drawing as I'm certain there was no transformer on there.

If there was then I just got lucky building something without it that worked

Seems feasible! A 100V line transformer is a very simple way to knock a really powerful amp down to get a 'line output' and gives the bonus of earth isolation.

You still need the power resistors to load the amp but there is less faffing about with further attenuation.

I still have a couple of old 100V line traffs kicking about if anyone wants one. Just remembered! I build a really high power load box for soak testing amps at Bs...wonder if it is still there?

Dave.