TubeJuice Attenuator

[duhvoodooman***]

While poking around on eBay a few days ago, I did a buyer's search on "attenuator" to see if there were any good prospects for a used Weber Mini-Mass. I've been considering an attenuator for some time, since I play in a small room in my home, and cranking the volume up past halfway on even my little 5W Valve Jr is painful to the ears and obtrusive to the rest of my family.

One of the items returned by the search was an attenuator called the "TubeJuice". The description sounded pretty interesting--a nice, simple one-knob box rated for 30W and selling for a Buy-It-Now price of $65 plus $6 shipping within the US. Since high-end attenuators like the THD HotPlate go for well over $200, that seemed like a relative pittance to pay....IF it worked well. I checked the guy's eBay feedback, which was excellent, with several positive comments by previous TubeJuice buyers. There were also two very positive reviews posted on Harmony Central. For $65, it sure seemed worth the risk, so I went ahead and bought one.

The seller, Mark Wood, builds these units himself and sells primarily through eBay, though he does have a website. He's obviously trying to get a small business going, and appears to take a strong interest in each sale. His communication was prompt--within minutes of buying the unit, I received an e-mail asking whether I wanted an 8 or 16 ohm version--and shipment was immediate. I had the unit in three business days. So far, so good!

I bought the 30W version, since my biggest amp, a Peavey Delta Blues, is rated at 30W. But he also sells a beefier unit, rated for 100W. The TubeJuice is a simple affair, to be sure--a small plastic box with standard 1/4 inch "In" and "Out" jacks and one knob (see photo below), which increases or decreases a resistive load housed inside the box. You have to provide the connections between your amp, the TubeJuice, and your speakers. If you use a head/cabinet set-up, you're halfway there already, and just need another section of speaker wire with 1/4" jack plugs. But at 30W or less, most of us will be using this unit with a combo amp, which may require adapter pieces with 1/4" plugs on one end and male or female spade-lug connectors at the other. I had previously bought a set of these, which came from Weber, in anticipation of an attenuator purchase, and they work great for my Delta Blues. Once the TubeJuice is connected, it's just a matter of dialing your amp up to the volume setting of choice, and adjusting the attenuation knob to a comfortable sonic level.

My biggest questions about the unit were (1) will it "suck tone", as some of these attenuation devices are known to do, and (2) will it generate a lot of heat? After running the unit with both my Valve Jr. and Delta Blues, those fears have been allayed. Yes, there is definitely a loss of top-end at high attenuation, but it's really not very pronounced, and I found that I could adequately compensate with the amp's tone stack and the guitar's tone pots. Overall, I thought the two amps sounded amazingly good with the TubeJuice, even at very high attenuation. And heat seems to be a non-issue--after playing through it hard for a matter of 20 - 30 minutes, the box remained cool to the touch. If the components inside are getting hot, they must be pretty well insulated from the outside of the casing.

As far as fulfilling its main function--allowing me to dial up the volume on my two amps to achieve power tube saturation and the nice, smooth overdriven tone that goes along with it, while avoiding permanent damage to my ears or my marriage--the TubeJuice is a rousing success. I got to hear tones from my Delta Blues that I have never come close to achieving before. Had that sucker up as high as 10 (out of 12) on the clean channel volume dial, when I'd never been able to go past 3 before, for fear of rupturing an eardrum! The Valve Jr. gave similarly positive results; though I had cranked it up to tube saturation before, the TubeJuice allowed me to get there at a much more comfortable volume level.

To give a flavor of what I'm talking about here, I recorded an audio clip (link below) using the TubeJuice with my Delta Blues and Epiphone Dot. This is recorded on the DB's clean channel using the Dot's bridge pickup (a Duncan SH-4 JB model humbucker). Same pentatonic riff, played 4 times; no pedals or other effects, other than a bit of reverb. The DB volume settings are, in the order played, 1.5, 3, 5 and 8, with the attenuator off for the first and then progressively dialed up to keep overall volume level in the same basic range. By the end, the TubeJuice is cranked to well over 90% of its attenuation range. I intentionally didn't touch any tone controls throughout, so that the impact of the degree of attenuation on tone can be heard. I threw in a little of one of my favorite Neil Young tunes at the end, for grins!

Also attached is a screenshot I took of the GUI in the Audacity recording/editing software I use to record my clips. This shows those same 4 repetitions of the riff in the audio clip. You can very clearly see the effect of the increasing amount of applied attenuation and the resulting compression & sustain effects on the output signal. As radically different as they "look", it's hard to believe that the four segments sound as similar as they do! Pretty cool stuff, I thought!

Only time will tell, as far as the reliability of the TubeJuice goes, or how it interacts with my amps over a broader range of use conditions. I'll update this thread if any new developments arise. In the meantime, the TubeJuice 30W definitely gets the DVM Good Guitar-Playing Seal of Approval!

Links/attachments:

TubeJuice Audio Clip

[kerc]

Interesting! I'm looking for an attenuator for my Amptramp...How does it compare to the Weber MASS? Is it more transparent? I see it can work easily with my amp--it's only about 10W (but you know how loud 10W can get!)...

[duhvoodooman***]

Interesting! I'm looking for an attenuator for my Amptramp...How does it compare to the Weber MASS? Is it more transparent? I see it can work easily with my amp--it's only about 10W (but you know how loud 10W can get!)...

Kerc, the only way I can answer that is to direct you to listen to the clip and judge for yourself. I haven't played through a MASS, so can't do a direct comparison. The TubeJuice certainly isn't completely transparent, but its tonal benefits certainly outweigh any negatives, at least for my purposes.

[kerc]

Isn't this the same as an L-Pad?

[Plank_Spanker]

Wow!

Not to be a "nay sayer", but you said it was cool to the touch after 30 minutes? Just the small heat sink area on that box makes me wonder.

I wonder how it would fare on a four hour, three set gig. I use a 40 watt amp on gigs that I keep tamed with a THD. It's quite warm to the touch at the end of the night.

[Spudman***]

Open it up. Let's see what's inside. Ppppppppllllleeeeaaasssseee?

[duhvoodooman***]

Isn't this the same as an L-Pad?

The maker told me that it worked on a purely resistive basis, so I would think that it's an l-pad or very similar design.

Not to be a "nay sayer", but you said it was cool to the touch after 30 minutes? Just the small heat sink area on that box makes me wonder.

I wonder how it would fare on a four hour, three set gig. I use a 40 watt amp on gigs that I keep tamed with a THD. It's quite warm to the touch at the end of the night.

Yeah, I hear you. As a home player of modest needs, this unit seems to meet my requirements perfectly. I rarely get to play for more than an hour at a time, but I'll try to keep tabs on heat generation as I use it more.

I don't know if it would be up to the rigors of gigging. But then again, at only 30W, I doubt that it would be big enough for the larger amps typically used for that purpose.

Open it up. Let's see what's inside. Ppppppppllllleeeeaaasssseee?

I'll do that tonight, Spuds, and post a pic or two....

[Plank_Spanker]

Looking forward to the pics.

[duhvoodooman***]

Yup, it's an L-pad:



Now I can see why the outside doesn't get hot. The back of the L-pad "floats" inside the casing. The big plastic knob insulates the shaft. Any heat is passively dissipated through the 6 air vent holes in the top & bottom of the casing. Maybe if it runs long enough, the casing would eventually get warm.....

[Plank_Spanker]

That definitely explains the size of the box. Play that puppy for a while and tell us some more.

[duhvoodooman***]

Just finished playing through the TubeJuice for the better part of an hour with my Delta Blues cranked to 9 (of 12 max), and the outside of the unit remains ~ room temp. So I immediately opened it up and felt the back of the L-pad itself--warm, but not hot. It was still cool enough that I could place it against my cheek without discomfort. So while this definitely generates heat (it pretty much would have to; that energy has to go somewhere other than the speaker), it's either (1) not much, or (2) it sheds the heat pretty efficiently. However, with only a passive cooling system, I have a hard time understanding how (2) could be achieved....

In any case, the little sucker still sounds mighty good to me! Gettin' that nice "creamy" overdrive with it! My DB has never sounded better!

[Plank_Spanker]

In any case, the little sucker still sounds mighty good to me! Gettin' that nice "creamy" overdrive with it! My DB has never sounded better!

That's all that counts!

[duhvoodooman***]

Came across THIS while googling for L-pad info. Take note of the sentence right above the first pic that starts "Consider repackaging this...." Looks like somebody did exactly that!

[kerc]

I asked you about it being and L-Pad 'cos I was considering building my own...This is the unit I'll use (I'm gonna order it tomorrow):

Click here to see the L-Pad...

And will buy a case in Radio Shack to put it in. I'm considering finsgin a way to stick a heat sink to it--I gotta have the parts first to figure out how to do it and make it work.

Thanks for the info and the clips!

[duhvoodooman***]

I posted an expanded version of this as a review on my website:

TubeJuice Review @ DVM.com

[Spudman***]

Excellent review Voodoo. The Audacity photo along with the sound clip is a ton of information just in themselves. Nice write up.

[y2kgtp]

Just registered here due to this old thread I found.....

Had a question on this....is it ok to use a 16ohm L-Pad for a 8ohm output\speaker?

[kerc]

I built mine a couple weeks ago. Works perfect! I will add a switchable cap circuit to it to bleed low frequencies, 'cos it can get muddy at very low volumes.

Total cost for parts: $26.

[unclefoo]

This is an old thread but ..... Is anyone still using an L-Pad attenuator? Any problems with blown Output transformers?