Powersoak / Attenuator, bad for your amp?

[finkfloyd]

Could someone please explain how these work and are they bad for your amp? I just want to be able to crank the amp to get natural distortion on the clean channel at lower volume. Im a bedroom player and this amp is very loud, infact i dont usually go past 9 o clock on the clean volume!!

Im guessing after looking at the Marshall powerbrake these use very large resistors, and get hot, they also seem to be very expensive.

I basically posted this in a pretty dead forum elsewhere:

I bought the new Soundcity 50 Watt Head and use it with a Hiwatt 4x12, it is a seriously loud amp, and uses 4x 12AX7's and 2 6L6GC's. I use this at home and I darent turn up the volume! You could easily get arrested with this thing and go deaf. I find it is very punchy, in a way if you play then strike a little harder you can feel the power! I'm no expert on amps, but it has a great clean channel, but the overdrive channel can be very nasty I find, and sounds almost like a fuzzface maxxed out. More interestingly you can roll down the volume on your guitar, and it will clean up consideringly well, just like a fuzzface, after playing with it for a month, I have grown to like it, but the distortion is pretty nasty you have to be carefull with it.

For example the song Echoes by Pink Floyd, when I play the solo I have the overdrive at 2:30 and the overdrive level at or however loud you want to play! and I can then play the chords fairly clean and then when the solo kicks in I can turn up the volume to get the nasty full on distortion.

I have also been experimenting with the fx send and fx return function , which where i have my delay and chorus, and it does give a nice cleaner delay when used here, I believe the fx send and return place the pedals after the preamp section, just utilising the output section. I would like to know though if the clean channel on this amp still utilises the preamp stage as well as the output stage?

I havent tried that many pedals on this, but the clean channel takes pedals really well. I have used various distortions on it, but I generally use only a compressor, (Boss CS-2) and modulation such as an Ibanez DE-7 Delay/ Echo and Boss CE-2. I would love to know if its possible to drop in EL34's in place of the 6L6GC's how much would it cost roughly for a technician to do this? Would this make it closer to a Mark 4-5 head? and would it make the clean channel break up earlier and also make it a quieter amp?

Is it worth looking into buying a powersoak / attenuater? Are these bad for the amp/tubes? I forgot to add, The channel/reverb foot switch makes a pop when changing channel, this could be fixed most likely by adding pulldown resistors, I'll get round to that soon.

I hope that helps a few people, incase you were thinking about buying one.

[Dai H.]

My understanding is not necessarily but potentially yes. In the way that if you have an amp (this is probably going to be an old one) where it was never designed to be cranked up all the way and played that way and the attenuator allows you to do it (since previously one might imagine that this wasn't done much or often simply because this would have been too loud) and as a consequence the output transformer is damaged from too much current passing through and overheating, maybe compromising the insulation on the wire inside or even melting the wire. The other way (could be both) is that a "reactive" attenuator (designed with inductors which help to simulate a speaker response as a load on the output of the amp) helps to induce oscillation (continous amplification, power output, amp working hard) leading to the same output transformer damage. Because of this possibility a tech checking an amp (using feedback) should check for oscillation not just with an attenuator but with a long speaker cable as well (long speaker cable is like an inductor--has inductance). Also, some attenuators the way they are designed can create mismatched loads depending on the impedance and setting. Mismatching up stresses insulation, could lead to arcing. Mismatching down stresses tubes. Anyway I would suggest to read the literature available at places such as GEO and the Aiken Amps site for genuine expert info.

[Hamfist]

I've been using a THD Hot Plate with an old Marshall 2203 for about 4 years now.  I run the master volume wide open on the amp.  The amp gets used once a week on average, for about 2-3 hours per practice.  That's how it's been (on average) for the last 4 years or so.  Everything works fine.  No problems or issues to report.  So it doesn't seem to be bad for the amp. 

[Ronsonic]

How they work? Just a large resistance network to turn some of the power coming out of the amp into heat while presenting the correct load to the amp. More sophisticated units use reactive loads to more closely emulate a speaker load and to minimize the effect on the sound. I haven't heard anywhere close to all of them, but the ones I have heard tend to sound pretty bad if you are heavily stepping on the output level. They're usually at their best taking some of the roar off rather than living room level playing with your stage gear.

They won't hurt your amp. Running an amp hard for long periods of time will break the more fragile ones, and will wear any amp out quicker. That's part of the deal every time you turn it on, just something to deal with.

Like always with a tube amp, make sure the impedances are set correctly and never take it off standby without a proper load connected.

[petemoore]

  Having troubles with output jacks, I'd prefer that section hardwired [speakers too...everything soldered would be nice.
  Impedance switches, I prefer to do without them either.
  an input buzz is one thing, but an output that sounds fine but is having a continuity problem under load and the catastrophic consequences is what I choose to risk for having separate heads/cabs.
  And the smaller amp...instead of turning the hard earned watts into heat instead of heat dissipation, but some users write that tubes seems to hold up well when things are working right.
  At lower attenuator settings the amp sounded compressed, motorized attenuators are better in this respect?
  The amp would necessarily sound a little different, {NNBoW} not much after adjustments IIUC, unless under heavy attenuation.

[drewl]

Attenuators do a good job, but at low levels do tend to alter the sound too much, but I've been using my Hotplate for about ten years with Marshalls, Voxes and even Sound City's with no problem.
The attenuator itself won't damage an amp, but you will be putting more stress on the amp.
as long as it is set up and biased properly, you should have no problems. You will wear the power tubes out more often, but that's to be expected.

[earthtonesaudio]

The biggest risk is that you'll turn your amp up louder than you normally would, and wear out the output and power sections sooner than you normally would.  In the worst case scenario, you could get hard clipping of the output section, which can sometimes cause tubes or output transformers to fail.  But it'll probably let you know by sounding like crap before you do too much damage.

My suggestion is, don't turn up a valuable or fragile amp more with a power attenuator than you would without it.

[brett]

Hi
I would expect that resistive power soaks will be *safer* for OTs, etc than inductive loads (including speakers).  Maybe the "spin" about danger helps sell, or inflate the price of soaks.

You can easily and cheaply build your own soak, such as this one for 4 ohm systems (I put this in an Epi junior where it works well).  Just ensure your resistors have enough power rating, and double-check the wiring before firing it up.



cheers
   

[d95err]

Just some thoughts about attenuators....

First, if you really want to crank a 50W amp at "bedroom" volume, you're going to need at least 20dB of attenuation, probably more. 50W is a LOT of power! I've built a tube amp with Powerscaling that scale from 15W down to 0.15W (approx 20dB difference). This is still a bit too loud for bedroom volume, so I use an L-Pad attenuator to take it down a further 6dB (total of 1/400th of the power!).

Reducing power this much will definately change the tone, regardless of what method you use. This is mainly because hearing is non-linear. You hear less treble and bass at low volumes (the ear focuses on the mid-range). This can explain why attenuators are often described as being "dull" or "thin" at high attenuation settings. However, if you record an amp with and without attenuation and play it back at the same level, the difference is much smaller than one would think.

Other reasons why the sound changes are because the interaction with the room is different, and that speakers will not work optimally with a very small power input.

[chillhuman]

Could someone please explain how these work and are they bad for your amp? I just want to be able to crank the amp to get natural distortion on the clean channel at lower volume. Im a bedroom player and this amp is very loud, infact i dont usually go past 9 o clock on the clean volume!!

Im guessing after looking at the Marshall powerbrake these use very large resistors, and get hot, they also seem to be very expensive.

I basically posted this in a pretty dead forum elsewhere:

I bought the new Soundcity 50 Watt Head and use it with a Hiwatt 4x12, it is a seriously loud amp, and uses 4x 12AX7's and 2 6L6GC's. I use this at home and I darent turn up the volume! You could easily get arrested with this thing and go deaf. I find it is very punchy, in a way if you play then strike a little harder you can feel the power! I'm no expert on amps, but it has a great clean channel, but the overdrive channel can be very nasty I find, and sounds almost like a fuzzface maxxed out. More interestingly you can roll down the volume on your guitar, and it will clean up consideringly well, just like a fuzzface, after playing with it for a month, I have grown to like it, but the distortion is pretty nasty you have to be carefull with it.

For example the song Echoes by Pink Floyd, when I play the solo I have the overdrive at 2:30 and the overdrive level at or however loud you want to play! and I can then play the chords fairly clean and then when the solo kicks in I can turn up the volume to get the nasty full on distortion.

I have also been experimenting with the fx send and fx return function , which where i have my delay and chorus, and it does give a nice cleaner delay when used here, I believe the fx send and return place the pedals after the preamp section, just utilising the output section. I would like to know though if the clean channel on this amp still utilises the preamp stage as well as the output stage?

I havent tried that many pedals on this, but the clean channel takes pedals really well. I have used various distortions on it, but I generally use only a compressor, (Boss CS-2) and modulation such as an Ibanez DE-7 Delay/ Echo and Boss CE-2. I would love to know if its possible to drop in EL34's in place of the 6L6GC's how much would it cost roughly for a technician to do this? Would this make it closer to a Mark 4-5 head? and would it make the clean channel break up earlier and also make it a quieter amp?

Is it worth looking into buying a powersoak / attenuater? Are these bad for the amp/tubes? I forgot to add, The channel/reverb foot switch makes a pop when changing channel, this could be fixed most likely by adding pulldown resistors, I'll get round to that soon.

I hope that helps a few people, incase you were thinking about buying one.

The way you know if your amp can handle full output for hours at a time is to run at 50% for a long practice, and feel the PT and OT when you're done. If they're too hot to touch, you can't do it. Then turn up to 70% and keep bumping the dial until you get to 100% output, with not overly hot xfmrs. Another option for you is to buy the least efficient speaker that will handle the power. You would be amazed at how going from a 2x12 w/ efficient speakers to a 1x12 w/ a low efficiency speaker will cut your volume

[finkfloyd]

Hi, sorry about the delay in answering, Ive been really busy, I got a job in IT and dont really have time for diy no more, But ive still got GAS always buying stuff like rf chokes and stuff and pedals i dont need haha.. Thanks for the very informative replies, it is much appreciated!

I was looking at something even more interesting, the THD yellow jackets, they are a socket adapter, which dosent require biasing and change the amp to true class A if it isnt already and drop a 50 watt amp to 20 watts or a 100 watt amp to 30.

What are Yellow Jackets®?
Yellow Jackets® Converters are a type of specialized adapters which permit the use of EL84/6BQ5 power tubes in place of 6V6, 6L6, EL34, and 7591 types.

How do they work?
They give you simple Class-A operation from any amp.Yellow Jacket® Converters not only rearrange the pin locations of the tubes, but also provide the necessary current limiting on the screens and cathode as well as blocking the amplifier's grid bias voltage, while configuring the EL84 in a Class-A, Self-adjusiting cathode-bias circuit. In other words, there are no adjustments to make and no modifications necesary, you simply plug the Yellow Jackets® into the amp's output tube sockets, (in cathode-bias amplifiers) screw the ground wires under one of the output tube socket mounting screws, plug the provided EL84's into the Yellow Jackets®, turn on the amp and play.

How will they change my amplifier?
It's like getting a whole new amplifier! In Champ and Deluxe type amplifiers, the Yellow Jackets® output is smooth, strong and more even than with the stock 6V6s. When the Yellow jackets® Converters are installed inlarger amplifiers intended for 6L6s or EL34 output tubes, the high plate and screen voltages are reduced as well as current limited to protect the EL84 and to drop output power. When a pair of Yellow Jackets® are used in a Marshall 50 watt or similar amplifier, the overall power drops to about 20 watts and takes on more of the character of an old Vox AC30. The distortion is smoother and more even and the output is both substantially reduced and more compressed due to the Class-A nature of the Yellow Jackets®. In a 100 watt amp like a Twin Reverb or Marshall 100, either two or four Yellow Jackets® can be used. If only two are used and the other two sockets are left empy, the output is dropped to about 20 watts. With four in place, the amp puts out about 40 watts and takes on a whole new warmth and richness.

In the cases of the YJ7591 converters, the overall ouput power remains the same, but the sound becomes fuller and the extinct 7591 are replaced with common and inexpensive EL84 tubes. In old Ampeg Reverb Rockets and the like, you experience a warmth and sweetness that you could never get with the now unavailable 7591 tubes.

Will they hurt my amp?
No! Yellow Jacket® converters are safe for all amplifiers and transformers. As all Yellow Jacket® Converters internally limit voltage and current they put no extra strain on amplifiers' power and output transformers or internal components. Using the Yellow Jackets® in higher powered amplifiers actually reduces the strain on the transformers and internal components because it reduces the overall wattage of the system. Furthermore, the heater (or filament) current of the EL84 is lower than that of the 6L6, EL34 or 7591, so the Yellow Jacket® will reduce the strain on the filament windings of the power transformer as well.

How do I get one?
First, figure out the type of power tubes your amp uses (call us or the amp's manufacturer if you're not sure). Then call your local music store (many dealers who don't carry the THD amplifier line do carry the Yellow Jacket.) If they are out of stock, call your closest THD dealer, or call us here at the factory. We will be happy to answer any questions you might have on any of our products.

Anyone had experience with these? I would much prefer el34 tubes in my amp rather than the el84's which i would have to use if i got these.

[drewl]

I've never cracked one open to see what exactly is in a yellow jacket, but as stated they do run EL84's cathode biased where you'd normally have EL34's or most any octal output tube.
They probablyi solate the bias voltage and ground the cathode through a resistor/cap combination.
They sound -okay- but  if you've played a good 18-20 watt amp like an AC15 or Marhsall 18w  they are still plenty loud, too loud for home use, but a little easier to manage in a live situation.

[brett]

Hi
My Marshall 18W (2 x EL84) breaks up fairly early, so if you don't want too much crunch, then these might be ok.  But EL84s can potentially make a defining sound when cranked, and thru efficient speakers.

With any soak, if your tonestack has a "mid" control, you can correct for the perceived loss of bass treble at low volume by rolling the mids back.
cheers