L-Pad convert from 8 to 16ohms?

[mrjones200x]

Hi there im gonna invest in a L-Pad for my Epi valve junior but you can only buy them in 8ohms resistance.

 

 

 

 

What i would like to do is it to build an L-pad into a box with 3 outputs for 4, 8 and 16 ohms incase i decide to use my valve junior on different cabs.

 

I have the stock speaker 16ohms and also my Vox which is 8ohms at the moment and i like using both as they sound slightly different.

 

Anyone got a link to a wiring diagram as im sure it can be build easily instead of paying 60 pounds for an already built one off of ebay?

 

Im hoping its as easy as buying an 8ohm L-pad and then a few resisters and a few jack plugs, oh and a smart box of course.

 

If anyone knows where to get different rated L-pad in uk that would be great too.

 

I'll prob wanna build it for use on up to a 20 watt valve amp as i'll prob upgrade in the future. Prob be wise to buy a 50 watt one yeah??

 

Many thanks guys

 

FOUND ONE IN 16 OHMS SO CAN MAKE JUST FOR EPI.

 

wOULD LIKE TO MAKE A MULTI OUTPUT ONE REALLY THO

[layboomo]

I suggest you read and understand this http://www.webervst.com/lpad.htm It should answer alot of your questions. The type of resistors used are what are called dummy load resistors and they look like cement blocks...they are not the cheap little film resistors that you may be thinking of.

[mrjones200x]

Hi, thanks for that.

 

I have read and understand to a certain level.

 

Only thing i am unsure about is the DB desired attenuation.? Its only for a 5 watt epi valve for now. Do i need to know how much Decibels it makes now and how much i wanna cut it by?

 

Bear in mind i know nothing about music measurement terms and only know a little about electronics

 

Thanks so far.

 

If it gets to complicated for me i'll prob just get an L-pad rated at 15 watts and put between amp out and speaker in.

 

This is a design ive seen. simple but effective (Please tell me if im wrong)

 

http://www.guitarpug.com/2008/07/diy-wattage-attenuator-box/

[strangedogs]

Found this one:

 

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=260-254

 

 

this company sells different ones (Stereo and mono) 8 & 16 ohms and differnt wattages too - they may ship to the UK - not sure - i'm buying the one in the link - should handle the VJ no problem... (hoping anyways as I'm dumb as a rock when it comes to electronics)

[layboomo]

"Only thing i am unsure about is the DB desired attenuation.? Its only for a 5 watt epi valve for now. Do i need to know how much Decibels it makes now and how much i wanna cut it by?"

 

It's pretty simple really try plugging in the numbers as follows.....16 Ohm amp/speaker 10DB cut which is half as loud as the valve jr wide open and translates to.5watts of power......the chart will give you the resistor values. In short, yeah you can safely use a 10 or 20 watt L-pad no problem at all with a valve jr.

[strangedogs]

"Only thing i am unsure about is the DB desired attenuation.? Its only for a 5 watt epi valve for now. Do i need to know how much Decibels it makes now and how much i wanna cut it by?"

 

It's pretty simple really try plugging in the numbers as follows.....16 Ohm amp/speaker 10DB cut which is half as loud as the valve jr wide open and translates to.5watts of power......the chart will give you the resistor values. In short' date=' yeah you can safely use a 10 or 20 watt L-pad no problem at all with a valve jr.

[/quote']

 

won't hurt to use a 50 watt L-Pad will it? Might wanna use it also for my 15-watt Vintage Tuber if I mount it in an enclosure... and also they only start @ 50-watts for the 16-ohm

[layboomo]

 

won't hurt to use a 50 watt L-Pad will it? Might wanna use it also for my 15-watt Vintage Tuber if I mount it in an enclosure... and also they only start @ 50-watts for the 16-ohm

 

Not at all .......I'd be carefull going to much above a 15 watter though as the peak output can be quite a bit higher than the rated output on some amps.

[mrjones200x]

[quote name=layboomo

It's pretty simple really try plugging in the numbers as follows.....16 Ohm amp/speaker 10DB cut which is half as loud as the valve jr wide open and translates to.5watts of power......the chart will give you the resistor values. In short' date=' yeah you can safely use a 10 or 20 watt L-pad no problem at all with a valve jr.

[/quote]

 

 

Only one more question,

 

Will it shorten the life of the tubes and could it cause damage to anything in the amp? Or will it be the same as running full blast all the time.

 

Thanks

[layboomo]

[quote=layboomo

It's pretty simple really try plugging in the numbers as follows.....16 Ohm amp/speaker 10DB cut which is half as loud as the valve jr wide open and translates to.5watts of power......the chart will give you the resistor values. In short' date= yeah you can safely use a 10 or 20 watt L-pad no problem at all with a valve jr.

[/quote]

 

 

Only one more question,

 

Will it shorten the life of the tubes and could it cause damage to anything in the amp? Or will it be the same as running full blast all the time.

 

Thanks

 

This is actually a really good question and it depends who you ask as to the answer you'll get...but I don't think the amp cares if it's driving a speaker or a dummy load. In general though the more heat...the more stress on components...that's pretty much a given....but hey man these things were designed to be played ...Right?

[GrumpyOldMan]

In the UK CPC have 8 ohm ones in stereo and mono. www.cpc.co.uk item number LS00543 mono or LS00544 stereo. I wanted a 4ohm one and was told I could bridge an 8ohm stereo one but never tried it as I bought an 8 ohm speaker so bought an 8ohm mono one. Wasn't a gradual change though, tended to be a bit off or on with a very small amount in between so I don't use it to be honest.

Hope that helps,

Ian.