Attenuators vor valve amps

FenderBender

Fritz Brand wrote: Would you guys say it is at all possible to get decent tone out of this baby without alarming the neighbours? I am trying to make plans to get the bucks, only way I see it happening is by selling / trading my AD50VT, but then I need to know that I can actually use this thing of beauty in my house without having the cops show up.

Fritz, I'm presently looking at building attenuators for valve amps that will allow full tone at low volume. I have been meaning to get around to this for Alan for a few months now. The best attenuators are ones that are matched to the impedance of the amp driving it.

I could either design a unit to handle a specific impedance, or design a universal unit that will handle 2,4,8 and 16 ohms. The second option would make the unit far more expensive, larger and somewhat less reliable due to all the fancy switching and extra components needed. I don't own a valve amp, so maybe some feedback from our members as to what impedance to design around would be a good starting point.

FatBoy

That is great news man, now I must just get the money together! No idea on which impedance to start off with, maybe just build them to order?

themanthatwalks

the bassman is 4ohm

FenderBender

Cool, I also think a 4ohm proto is sensible. Lets see if I can actually get this project rolling quickly ?

AlanRatcliffe

Build them to order. I need a 16 Ohm version rated at 25 - 30W (15W amp).

Gearhead

... and I would be interested in an 8 (15W) ?
oh PS I would very much prefer it to be switchable..?..?

FenderBender

Duly noted, thanks all. Now that the pressure is on I'm stepping up to the plate, as it were ?

AlanRatcliffe

Graeme Parfett wrote: Duly noted, thanks all. Now that the pressure is on I'm stepping up to the plate, as it were ?

You mean, stepping up to the hotplate, don't you? ?

Gearhead

Thread hijack alert! Alan, should we not put the last few posts in a separate topic? I wouldn't pick up on the fact that one can now buy Parfett Hotplates from the thread title about Bassman Heads.

AlanRatcliffe

Gearhead wrote: Thread hijack alert! Alan, should we not put the last few posts in a separate topic? I wouldn't pick up on the fact that one can now buy Parfett Hotplates from the thread title about Bassman Heads.

Thanks GH - you are right! Done!

CDee

Hi,

Would that sort of thing work for my Fender Hotrod Deluxe? It's way too loud for my current setup and I rarely use it past 2 on the volume.

Thanks

AlanRatcliffe

CDee wrote: Would that sort of thing work for my Fender Hotrod Deluxe? It's way too loud for my current setup and I rarely use it past 2 on the volume.

That's how they work best - to bring down the volume of the amp a few notches so you can crank it a bit more for power tube saturation while keeping the same volume.

Many of them are capable of bringing down the volume of a loud amp quite a lot, but the more you attenuate, the more it changes the tone. The best range is 12dB or less.

deanBailey

I would love to check one of your custom build ones, been hearing about attenuators and checking them out online for ages and haven't tried 'em yet.

CDee

Alan Ratcliffe wrote:
CDee wrote: Would that sort of thing work for my Fender Hotrod Deluxe? It's way too loud for my current setup and I rarely use it past 2 on the volume.
That's how they work best - to bring down the volume of the amp a few notches so you can crank it a bit more for power tube saturation while keeping the same volume.

Many of them are capable of bringing down the volume of a loud amp quite a lot, but the more you attenuate, the more it changes the tone. The best range is 12dB or less.

In that case... You can count me in. How much do they cost?

Gearhead

Eh, they have not even been designed yet. I suspect Greame's got some ideas though. It will have something to do with some resistors, one or two inductances and a bit of capacitance I suppose....

FenderBender

Alan Ratcliffe wrote: You mean, stepping up to the hotplate, don't you? ?

Actually only realised what I'd written after I posted ?
THD aren't perhaps assoc'd with Fender by any chance? Don't want to risk being had for circuit plagiarism :roflmao:

@CDee: Not sure on pricing yet. The project will more than likely require having some custom passive electronic components made up. Fortunately I have contacts in SA from my previous involvement in the power industry and should be able to source these without too much sweat or expense. I plan to get quotes on Monday from a few suppliers. Enclosures are reasonably priced and other hardware is available off the shelf. The multipole switches required for switchable impedance units would more than likely be the most expensive components.

@Gearhead: Spot on!

Gearhead

Yebo ? all attenuators revolve around those thingies, hey.

One more thing to clarify now that you mention multipole switches: When I wrote switchable I meant that I would like to be able to switch the whole thing out of circuit with a multipole relay (DPDT or 3PDT) to fit into my amp concept thing. The ones I'm using now for the output valve bank, ss/tube recto and ultralinear/penthode switching can take quite a large amount of current so they'd be fine with a little attenuator...

FenderBender

Ah ok I thought you were referring to switchable impedance. Makes my life easy then ?
Perhaps I should then consider two variants:

1) A basic, enclosed, external, in-line unit with sturdy jacks or screw-clamp terminals for amp input and speaker output.
Options:

on-board true bypass switch.
jack for external stomp switch and an internal relay with Safety Extra Low Voltage PSU allowing true bypass.

2) A cheaper, open frame unit with terminals for input and output.
The unit could be mounted on the amp's chassis using bolts or clipped onto standard top-hat type DIN rail mounted on the chassis, allowing easy removal.
Bypass switching would then be up to the installer.

Gearhead

what kinda dimensions are we talking about?

FenderBender

Gearhead wrote: Eh, they have not even been designed yet. I suspect Greame's got some ideas though. It will have something to do with some resistors, one or two inductances and a bit of capacitance I suppose....