Hi,

Can some tell me about the valve amp power attenuators… I am thinking of the Marshall Power break and the THD HotPlate.

http://www.marshallamps.com/images/products/powerbrake/powerbrake.html

http://www.thdelectronics.com/products/hotplate.htm

I want to be able to get Power tube distortion out of my amp at a more sane volume level. At the moment I have a 100W Marshall 6101 combo. I have used it in the past at high volumes (where the power tube distortion kicks in) and it is smokin’. However I want to be able to start doing a few recordings at home (in the apartment) during the day and thought that one of these signal attenuators could do the job nicely… Please no POD recommendations I want to mic up a valve amp!

I have read the Harmony central reviews and the Powerbreak gets a bit of a slating for being weak sounding and the THD gets great reviews up to -12dB attenuation. Now my question is:

If I have a 100W amp and I half the perceived loudness that means I have to have it down to 10W. Right? So that’s -6dB is half power? Now 10W is still going to be VERY loud in an apartment. So I would need -12dB to get it down to 1W. Now that’s a lot to ask of a power attenuator without messing with the tone.


PLease anyone with experience of this chip in...

Cheers

Steve

Hi,

By some strange coincidence I also have a Marshall 6101 - mines an LM version - and am on the lookout for an attenuator.

100w down to 10w is 1/10 power, which is 10dB attenuation.
Down to 1 watt is -20dB .

Have you used the Marshall in half power (50 watt) mode? Then -12dB gives just over 3w, which should be manageable and recordable without upsetting the neighbours.

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Nik
Godin, Axon, Tonelab, Repeater & the skin of my teeth!

Hi,

Yeah ?I have played around with the 6101 in the pentode triode and full half power modes...

These give the 100w 50w (pentode or triode) and 25W possibilities.

However they don't sound as good (to my ears) as the full on 100W.

I am confused about the attenuation and the perceived loudness of the amp.

I know 10W to 100W is ten times the power. However to the ear it is only twice as loud. The ear is logarithmic right?

So if I cut a single by 6dB (if its sound power) then thats halfing the sound power?

So -6dB would bring 100W down to 10W
So -12dB would bring 100W to 1W

Right? Please correct me if I am wrong BUT please explain it....

What I like to do is tame my 100W down to about 1W MAX. If I can get it down to 0.5W even better....


On a different note it would seem that THD make EXACTLY what I am looking for but wihtout the effects loop

http://www.thdelectronics.com/products/univalve.htm

Now if only this had a valve driven effects loop I would buy one....

Cheers

Steve

As we're talking dB SPL (sound pressure level) here, a halving of the power actually gives a 3dB reduction, not 6dB (as far as I know the -6dB rule only applies when dB is used in relation to voltage (V), not in relation to power (W)).

I'm guessing that your Marshall combo probably puts out in excess of 100dB SPL at the point of power tube distortion. That means that the best-case scenario with the THD will be around 90dB SPL - that's stillas loud as a ambulance siren. If you first reduce the output of the amp (you could take it as far as 25W, right?) you should be able to get it down to 94dB from the amp, and then subtract an additional 12dB with the hot plate would give you 82dB SPL. This will be (a bit of guesswork here) roughly equal to someone speaking very loudly (threshold of yelling).

On second thought: Power-amp distortion probably doesn't set in before you're closer to 110dB SPL. Adjust the figures accordingly.

You could check this site out for more on dB's:
http://www.jimprice.com/prosound/db.htm

Stig

Edited by The Stig (15/12/04 01:53 PM)

Quote The Stig:

---

As we're talking dB SPL (sound pressure level) here, a halving of the power actually gives a 3dB reduction, not 6dB (as far as I know the -6dB rule only applies when dB is used in relation to voltage (V), not in relation to power (W)).
Stig

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Yeh. That's right.
100 watts down to 10 watts is a power reduction to one tenth. That's a dB reduction of 10. From 10w to 1w is another tenth - another 10dB. So 100w down to 1w is total 20dB reduction.

Halving the power from 100w to 50w is a reduction of 3dB.

100w amp with 12dB attenuation is 6.25watts.

I find my 6101LM sounds the same at 50watts as at 100watts, and barely any less loud. Switching to Triode from Pentode does soften the sound, takeing the edge off. OK for practice, but not to my likeing for stage or critical recording.

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Nik
Godin, Axon, Tonelab, Repeater & the skin of my teeth!

Get a POD - much better for recording

Quote SunShineState:

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Get a POD - much better for recording

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No way will any digital modelling shite every produce the pure, brew-tal distortion of the Marshall 6101 30th Anniversary - probably the greatest Marshall ever, and so probably the greatest amp in the world ever. My guitar drips tone through an all valve Marshall and modelling is for wimpy country rock kinda Telecaster players!

Oh, and I use a Boss GT-6 direct to desk for recording, and usually it's the GT-6 direct to PA for live work as well.

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Nik
Godin, Axon, Tonelab, Repeater & the skin of my teeth!

Point that I'm really making is "horses for courses" - valve amps sound great cranked up hammering through speakers in a live situation - and part of this sound is the sheer volume of it - if you use an attenuator or similar I believe you will not be so happy with the sound, and so for recording I believe you may get a sound closer to what you want with "digital shite". Personally I have two Marshalls - including a 50w all tube from 1976 (not quite 30 years old yet) - but I find it rather boxy sounding recorded! Cheers

Or if you have a flair for making things you could look here.

http://www.scopeboy.com/ssim.html

And here.

http://www.scopeboy.com/tesla/index.html

Hi,


I have done a A-B test on a POD and a real amp. I am sorry yeah its 'good' but real valves IMHO takes you to an extra level of electric guitar- amp synergy. It is just inspiring to play the guitar! With my Lexicon MPXG2 and also a POD pro xt I tried it just feels gimmicky.

What I am after is the ability to 'tame the beast' enough to be able to record some killer guitar. I am unable to get the killer inspiring sound I am after with my lexicon or a pod or guitar rig (demo version) and belive me I tried... That is why I have come full circle and am convinced I need to be approaching the task properly:

Valve preamp and power amp sound cannot be bettered at the moment. It is just a question of me being able to enjoy that in practice and at a gig at a realistic volume and to be able to record it easier. Having a much lower volume would enable easier recording: You can trust yours ears more, if it sounds good at the lower volume then thats the sound you generally get recorded.

For example I considered the ZVEX nano-head which is a 0.5W valve amp. it is a GREAT little amp and suprisingly loud if you crank it. It is great to record with but it is a bit of a 1 trick pony. And the sound is very good but not what I am after. However it made me think that because it is so great to record with (because of the low power) that I could get some great recordings (and have an amp I love to practice and gig with) if I could lower the power on my 6101.

OK.. So with my Marshall I can put it to half power. This will give me 50W. So with a THD hotplate I would have -16db (maximum attenuation), -12db, -8db, -4db (minimum attenuation) or 0db (no atten.)

I have read reviews of the THD hot plate that all seem to say at -16dB the sound is not the best but at -12dB it is very good.

So 50W with 12dB of attenuation is 3.125W. (I can run the 6101 at half power using only 2 output tubes and I can just swop them around with the other two. This way I will cook em at the same rate.)

Now to be perfectly honest I reckon a 3.125W valve amp would still be pretty loud pushing say a 4x12 cabinet (1 option) or a single 1x12 (option 2). But exactly how loud I don't know. Would it be possible to talk over it? To shout over it? Would it be ok in an apartment ish situation?


The final option would be to run the 6101 in 25W mode (which is the pentode triode mode trick at half power). Now this does not as shingles agress sound quite as good... But that would give me 1.5625W.... So what would this be like?

Now the next question is NOISE. My 6101 does start to hiss in an great aggressive kond of way when I crank it. I can't remember the last time I serious cranked it up though but it did hiss a little too much. I have read that the hotplate does filter out the hum a little. (My strat has Kinman noiseless pickups in it and I am plannign to shield the cavity and redo the wiring with shield wire this christmas. So I hope this would not be too much of a problem.)

Ok so the other alternative is a lower wattage amp to start with.... The THD univalve looks intersting. However what I really want does not seem to be available...

Surely I can not be the only person on the planet who would buy a fully featured all valve low wattage amp. All the great low wattage amps tend to be single channel with no effects loop...


On a slightly off topic note - Shingles have you ever played the non LM version of the anniversary? I am told the only difference is the 3rd channel. I have the non LM original version and while the 3rd channel is very good it is not so different to the 2nd channel fully cranked. At the risk of being flamed it is a bit too american sounding for my likeing (and for a Marshall for that matter!).

I bought my 6101 in 1996 2nd hand and have absolutely loved it... Its a great amp... and with midi channel switching as well. I don't think that Marshall has made much progress since then.. The TSL seems to my ears very similiar and without all the features that make the 6101 so useable.




Thanks for the help!

Cheers

Steve

I've been pondering the same question recently, my Fender Twin needs to be in the next building when its cooking! So I've just bought a 30W Laney which can have 2 tubes pulled to give 15W. I think I will be able to get away with playing this full on, for a short while at least, or when the neighbour is at work. Enough to record a track with some hot tube action.
Torres do a 0.5W all tube amp I think, specifically for recording. Not cheap but good. Can't remember if it as more than one channel. Do you really switch channels while recording? I usually layer different sounds as it is difficult to get the levels set up before you do the mix.
That's the way I'm approaching it. Also, if you aren't happy with your 3rd channel, perhaps it needs a tube swap. Again Torres can sort this for you, or if you know what you are after, order from Watford valves.
Right, I need sleep now. Not well. Hope it hasn't fuddled my brain.

Firstly, 3.125 watts into a 4 x 12. Well, the drivers in a 4 x 12 are going to be rated somewhere between 97 and 103 dB per watt at 1m. So in theory, 1m from the cab, you will get between 101 and 108dB sound pressure level (SPL). No, you cannot talk over that. That is pretty loud.

1.5 watts will give somewhere between 98 and 105dB. Still too loud to hold a conversation over, but I would say that's manageable.

I did have a 6watt valve guitar amp with a 10 inch speaker. So twice the power we are talking about, but a less efficient speaker. Cranked up, it was too loud to talk over, was as loud as I ever have my 50watt per channel stereo, but not lud enough to annoy the neighbours in the next (detached, double glazed) house.

The Thirtieth Anniversary Series:
The 6100 and 610 1 were introduced in 1992. Power valves were EL34 - traditional Marshall.
Late in '93, EL34 supply dried up and Marshall had to change over to either 6L6 or (closely related) 5881 types for ALL their amps. They have taken a lot of stick for this, but the decision was forced on them by the valve manufacturers at the time.
In 1994, due to perceived demand, Marshall increased the gain on the red channel of the 610* amps and added the LM (Lead Mod) suffix.
I played one back in '95 in a shop, but don't know what variety it was. I bought my 6101LM one year ago, based on the memory of the '95 encounter, and it lives up to that.

I agree that the 'Annys' haven't been bettered by Marshall. I also use the MIDI switching. But the TSL is, to my mind, a different beast. The TSL has three channels, all of which are Marshally: Marshall clean; vintage Marshall - like a plexi or Master Volume or JCM800, and Marshall High Gain, like a JCM900SLX. The Anny has all those sounds just on the crunch channel. The green and red chann els are not meant to sound like Marshalls. Green = Fender clean. Red is somewhere between a Soldano and a Peavey 5150.

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Nik
Godin, Axon, Tonelab, Repeater & the skin of my teeth!

As for hum and hiss in the 6101. Hum may be due to filter caps drying up. You need a good tech to soirt this out.

Hiss is likely to be failing or low-quality valves. Try swapping some valves around and see if it makes a difference.

And yes, there must be many people who would pay for a fully featured, multi-channel, high gain, low power amp. I had GAS for a Boogie Mark IV since they were introduced in the late 80s. I always thought they should make a version with just the 15watt class A power amp. But hey, the Anny cured my GAS. Just a cool and versatile as the Boogie, but with that British accent the Mark IV lacks.

Yes, I want to try it with an attenuator and no, I have not yet tried recording it from the compensated line output.

Like I said, for recording and most live use I use a Boss GT-6 direct to the PA or recorder.

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Nik
Godin, Axon, Tonelab, Repeater & the skin of my teeth!

Folks, for what it's worth, I use a JCM800 and a Mesa Rectoverb with a THD Hotplate. Experience shows that these amps are not at their best turned to 10 - there is a sweet spot around 5 - 8 on the master. Set the volume controls where they work best and then use the attenuator to set actual volume.

Bear in mind that not all valve amps will actually overdrive the power stage - some manufacturers (Marshall included) have produced valve amps where you just can not do this - saves a lot of money on warranty claims apparently. You can test with a master volume amp by turning the MV to 10. the pre amp volume to 1 and the listen - some amps are still clean. If you do this with a good amp that will overdrive the power stage (like the JCM800) then you can get very close to the plexi sound.

At very low volumes (like night time practise) the sound does lose definition, the deep and top end boosts on the THD do a pretty good job of recovery but it is NOT quite the same.

For recording I bought a Behringer DI box with amp sim (GI-100 Ultra I think) for £30. Run this from the line out of the THD, set the THD to LOAD (ie no sound from the cab) and you get an amazingly good, real overdriven valve sound at line level.

I know some folks who prefer the Powerbreak and others who prefer the Hotplate - try and see. Note that although the THD comes in different models for different impedance reatings, you are OK so long as you match the Hot Plate to the amp. So I have a 8 ohm Hot Plate - I can use my JCM head set to 8 ohms into the 8 ohm HP - then plug into a 16 ohm cab. The amp still sees 8 ohms, the only thing is that the deep and top boosts don't work quite so well (this is how the Univalve gets by with one attenuator, but you can plug it into virtually anything). THIs info is direct from the excellent Ed De Ginaro at THD (apologies if sp is incorrect - this is from memory).

Oh, and the Univalve has a big brother called the Bi Valve - 30 Watts, has an FX loop, run it on low power, with 1 output valve - put al EL84 and you have about 5 W flat out - and then it has an attenuator built in. And I have one to sell!



Andi

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Andi, www.thedustbowl.net Mixing, Mastering, Audio Editing at The Dustbowl Audio

Or you could consider a silent speaker - you know the inverted ones where the speaker is actually in the box? Just a thought...

Stig

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If it sounds GOOD to YOU, it's bitchen; and if it sounds BAD to YOU, it's
shitty. -FZ

But you can use an attenuator for recording, home practice and on stage - every amp should have one.

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Andi, www.thedustbowl.net Mixing, Mastering, Audio Editing at The Dustbowl Audio

Quote Andi:

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But you can use an attenuator for recording, home practice and on stage - every amp should have one.

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Amen.
I actualy have my eye out for a Marshall Se100. It's a rack mounted powerbrake with all kinds of extra adjustments and tweaks on it.

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Nik
Godin, Axon, Tonelab, Repeater & the skin of my teeth!

Hey, let us know what you think when you try one.

A.

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Andi, www.thedustbowl.net Mixing, Mastering, Audio Editing at The Dustbowl Audio

Hi,

Ok well I have had a bit of a thought about this… Namely why you can’t seem to get an effects loop on these low wattage valve amps… (OK I know the bivalve has one!)

Effects loops place the effects in the signal chain after the preamp and before the power amp. High power (100W) amps are not often used at such a volume as to have power tube distortion. So the effects will stay clean. If however you have a low wattage power amp (or attenuate a high power) then you are going to get power tube distortion. This will cause the effects to be distorted. Now some effects are ok with having distortion added after but some do not react well to this… I like my time based effects after any distortion/overdrive/fuzz.

So it seems to me that the best way to do this would be for the purposes of recording to recording everything dry (which is good practice anyway), but this still means I can’t really practice or compose with a smoking valve sound and time based effects. I will need to add another amp to the equation.

What I will need is a very low wattage amp (or an attenuator) which I can get a preamp and power amp distortion sound from and then feed this into another amp which is set for a clean sound. I can then add effects inbetween. The THD powerplate or the Univalve head seems to allow me to do this.

Ok so the setup I would be looking at is:

THD univalve (18W all valve head with built in attenuator) line level output 

Time based effects. 

Into my Marshall 6101, line level input jack to take an external pre-amp thus
using just the power stage of the amplifier.


The benefit of this setup is I can treat the Univalve as the mother of all stomp boxes or pair the setup down into a simple Univalve  6101 speaker (bypassing the 6101 amp altogether)



The problem would be then that I need to go and play with a univalve head to test if I like it, and I’ve heard that because of the combinations of valves you can use with it it takes a lot of test driving.

Another solution would be to try the Univalve line level out into a POD XT type thing to get the speaker simulation part of the sound?

All of a sudden this has started to get rather too expensive…. Maybe I will just pick up a THD hotplate and try it out on my 6101 for a while and see what happens. If I want the mimimum distrurbances to neighbours then I'll use just the 1x12" speaker which is 8 Ohm so a 8 Ohm hoptplate it is...

Andi.... Can you PM me about the bivalve? If I only use 1 power tube then thats basically the univalve with the extra features, right? To be honest a bivalve is to much £££ for me but if the price is right....

Cheers

Steve

Cheers

Steve

How about:

Guitar > frequency based FX > smokin valve amp on 10 > dummy load (Palmer speaker simulator, Hotplate, Power Brake) and maybe a single cabinet for the dry sound > line out to time based FX > stereo, high power solid state power amps > several 4 x 12 cabs.

That's what Eddie Van Halen has been doing on stage since the mid 70's.

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Nik
Godin, Axon, Tonelab, Repeater & the skin of my teeth!

What we really need is an effect box that goes in the FX loop of a high power amp and simulates the sound of a valve power amp being overdriven.

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Nik
Godin, Axon, Tonelab, Repeater & the skin of my teeth!

I'm thinking of this solution to as a possbility (but mainly for recording purposes) but...

What I would like to know is:

1. What level of tone loss occurs by bringing down the volume level down say 50% or 75%
2. How much difference is there tone-wise recording at low level into a mic as there is at a higher level (i.e., no attenuation)

I currently have a 6W Cornford Harlequin. But this is still way too loud when cranked up to its sweet spot especially for lead work and is causing problems with resonance in the room at high levels as well as just being too damn loud! i'm thinking if i can get the volume down by 50% or so it may be acceptable but i don't know what affect this will have when it comes to recording the amp.

I don't want to compromise tone and need to record the excellent solid tone that the amplifier outputs. Perhaps i could offset the lower volume / effect by using a 2x12 or even 4x12 cab and a mic on each speaker or something... or possibly switching to using condensor mics instead... too many bloody options... i want my tooooone!!!

Any comments greatly appreciated!

Hi D@ve

I used a Harlequin for a while - that 6W was very nearly loud enough to use on-stage and it sounded very nice. For home use it was almost as unuseable as my Marshall 1/2 stack - way too loud.

My valve amps change sound as I turn them up or down, above about 5 or 6 on the volume control they don't get louder, they just get thicker and more "elastic". With an attenuator they also change as you turn them up or down. Everything interacts on a valve amp - every twist changes the sound.

To my ears attenuators sound good - if I'm running any of my amps at any given SPL, I'd rather run the master where I want it for the sound quality then attenuate for loudness.

Is the sound identical to that without the attenuator - don't know because the amps are so loud up close that my ears compress the sound anyway. Does it work for recording - oh yes! Does it work on stage - oh yes! Does it work at 2 in the morning with the kids asleep upstairs - pretty damned well - it's not exact but then who are we kidding, I'm not REALLY Joe Perry either.

I asked all the "are you sure" questions, then I plugged a LP into a plexi through an attenuator and just stopped asking.

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Andi, www.thedustbowl.net Mixing, Mastering, Audio Editing at The Dustbowl Audio

Many amps and guitar tones rely on power amp squash and so benefit from being run wide open into an attenuator. But there are also many amps and guitar tones that rely on preamp distortion alone. Seems to me the 6101 can be used either way.

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Nik
Godin, Axon, Tonelab, Repeater & the skin of my teeth!

While speaker attunuators for valve amps can be a good idea remember that if the sound you like is of the amp at almost full volume into something like a 4x12 cab a good deal of that sound will be due to the speakers breaking up as well as pre- and power amp distortion, which of course you won't get if you're attenuating the output to the speakers. It all depends about how important the various aspects of the sound are to you and you can't really know until you've explored the effect of changing each part of the amplification chain. In the same way smaller amp/speaker combinations don't have the same sound as a 100W Marshall (or whatever) head into 2 4x12 cabs, and the speaker in the isolated box won't sound the same as a cab in a big room. You just have to experiment until you find the right compromise for you.

Having used both the Marshall PowerBreak and the rack mounting SE100 version, I'd go for the cheaper Powerbreak as it offers more individual stages of attenuation while the SE50 only has 3. If you need the speaker simulation and DI capabilities of the SE100 have a look at a speaker simulation DI unit like the Red Box

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RockinRollin' VampireMan

Quote SugarBox:

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Having used both the Marshall PowerBreak and the rack mounting SE100 version, I'd go for the cheaper Powerbreak as it offers more individual stages of attenuation while the SE50 only has 3. If you need the speaker simulation and DI capabilities of the SE100 have a look at a speaker simulation DI unit like the Red Box

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Thanks for the tip.

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Nik
Godin, Axon, Tonelab, Repeater & the skin of my teeth!