THD Hot Plate

[emperor_black]

well, then all you have is a speaker with a 16 ohms total impedance if you're using two 8's or a 32 ohms speaker if you're using two 16's. that is not the same as micing a cab with the air displacing...

this is the isolation cab I was talking about. but i would think its will not be easy to change the mic to speaker distance...

http://www.musiciansfriend.com/product/Randall-Isolation-12-Speaker-Cab?sku=480371&src=3SOSWXXA

in most cases, tube amps perform well when you have impedance matching. Are you sure you're not overloading your amp's transformer?

[Cygnus X1]

well, then all you have is a speaker with a 16 ohms total impedance if you're using two 8's or a 32 ohms speaker if you're using two 16's. that is not the same as micing a cab with the air displacing...

this is the isolation cab I was talking about. but i would think its will not be easy to change the mic to speaker distance...

http://www.musiciansfriend.com/product/Randall-Isolation-12-Speaker-Cab?sku=480371&src=3SOSWXXA

in most cases, tube amps perform well when you have impedance matching. Are you sure you're not overloading your amp's transformer?

Huh?
I'm running 16 ohm speakers, parallel wired for 8 ohms.
Where did I say I was running 8 ohm speakers? Oh, well.
Yes, I ALWAYS make sure my speakers are matched to
the output. I'm anal enough to check it with the meter, to make sure.
As I say, I'm really just giving it a line out oprion
not a true "isloation box", so I can run the amp maxed and not
have to deal with the decibal problem.
And, connecting the amp's extension speaker (another 8 ohm load),
essentially cuts the overall volume almost in half, making "7-8" listenable.
We're overthinking this little setup, I think.

[straycat]

A very interesting read thanks guys.
My Carvin 100 watt head dosen't much like my power brake(Marshall)it gets flubby past 8 on the amp vol.
Now the 100 watt Jackson JG-3 head I had was stellar with the brake.I may try the Weber just for the fun of it.

[MSGfan]

The problem with this trick is 12au7 sends less signal than 12ax7,
so you are not driving power valves any harder.Basicly its the same as if you turn down the volume knob.Power attenuator lets you drive power valves hard(to distort)at lower volume

If you read the first post on this subject you'll notice the person asked is it possiable to acheve a decent sound quality at room levels without upsetting the neighbours with a THD Hot Plate. I was only sudjesting another method to lower output volume and still get a decent sound by changing the 12AX7 in the output driver to a 12AU7 which works great without using the THD. I don't use the Hot Plate on my Mesa Duel Recto's but I do change the output driver tube to a 12AU7 to tame the over all output volume.
I didn't sudjest that this simple trick would drive the output tubes any more!! But it will reduce the output volume to quite a degree in some amps with touchy master volumes.
You should give it a try before you knock it!

[jgcable]

I just recently discovered that attenuators exist and what they do. Now I'm wondering if anyone has experience with a THD hot plate through a loud amp like an Uberschall or 5150? Is it possible to play them with decent sound quality at room levels (without upsetting neighbours or roommates too much)?

IMHO.. no. Thats over attenuation. The sound will be slightly muddy even with a high end attenuator like the THD.

[hippietim]

Does an attenuator change your tone? Sure. It has to! You are changing the amount of air you are moving. You are not hitting your speakers as hard so your cone breakup characteristics can change quite a bit. If you use heavy attenuation then make sure your speakers are a match for the lower level.

In my experience with a lot of amps, -8db or -12db with the Hotplate is just fine - any more than that gets a bit washed out. If you regularly require more attenuation than that then you are using the wrong amplifier.

I've used the Dr. Z - very nice but I prefer the Hotplate a bit - you can't go wrong with the Dr. Z.

I gigged for many years with the Scholz Power Soak. It sucks your highs so you need some room on your treble/presense controls to compensate.

The Weber is a very cost effective solution and sounds excellent.

[butrus]

If you read the first post on this subject you'll notice the person asked is it possiable to acheve a decent sound quality at room levels without upsetting the neighbours with a THD Hot Plate. I was only sudjesting another method to lower output volume and still get a decent sound by changing the 12AX7 in the output driver to a 12AU7 which works great without using the THD. I don't use the Hot Plate on my Mesa Duel Recto's but I do change the output driver tube to a 12AU7 to tame the over all output volume.
I didn't sudjest that this simple trick would drive the output tubes any more!! But it will reduce the output volume to quite a degree in some amps with touchy master volumes.
You should give it a try before you knock it!

So I got you wrong,
actualy have some 12au7 at home ,and will stick them in 2210.
Lets see...

[Cygnus X1]

So I got you wrong,
actualy have some 12au7 at home ,and will stick them in 2210.
Lets see...

It's worth a shot, but you will lose some "gain".
It's equivalant to turning the volume down in front of the power tubes.
Master volumes work, because the gain stage gets saturated,
and the power tubes amplify that saturation. So, the solution to
preserve gain is to soak the pre's,(a kind of fizzy distortion), and reduce
overall volume in the power stage.
That's why I like 6V6's. They aren't so loud, you can "stuff" them pretty
well, and get a singing distorted quality that emulates a loaded up KT88.
EL84's do the same, that's why old Voxes get that "singing" quality. Champs, Blackface Fenders, etc. have a similar quality, with the 6V6's.

Modern amps use multiple gain stages to control this preamp fizziniess,
to get the distortion and run it through tone stacks. Marshall pioneered it,
and everything else follows.

So, bottom line is, if you can't drive the power tubes sufficiently, can't move the air with the speakers, then the only options left are to play with the preamp tones. This is where the emulators fall, and where they are doing quite well.

[butrus]

I tried that trick out.
Tried it with JCM800 2210 head.It has JJs ecc83s in pre amp and EH 6CA7EH in power amp.I tried changing jj(one closest to power tubes) with EH12au7 and another one but dont know the brand.
My settings are
presence 5
master 1
bass 5
middle 5
treble 4
pre vol.10
gain 9

Have to say I personaly dont like the result.
As Cygnus X1 suggested i lost some gain(although it was werry little),
Have to say i like gain hi,and use Blackstar HT boost in front to make my rythm sound more agresive.Also,sound was not so thight anymore.
Its hard to explain sound in my language and even harder in english.
I think lowering pre volume gives similar result,so why bother.
I only have pre gain on 9 becouse of lower noise and i compensate that(and more) with boost(gain wise)
So this trick might work in some situations,but is not the right answer for me.
Have to try Hotplate everyone is raving about,but my local stores dont have one...
The search is on.....

[MSGfan]

I tried that trick out.
Tried it with JCM800 2210 head.It has JJs ecc83s in pre amp and EH 6CA7EH in power amp.I tried changing jj(one closest to power tubes) with EH12au7 and another one but dont know the brand.
My settings are
presence 5
master 1
bass 5
middle 5
treble 4
pre vol.10
gain 9

Have to say I personaly dont like the result.
As Cygnus X1 suggested i lost some gain(although it was werry little),
Have to say i like gain hi,and use Blackstar HT boost in front to make my rythm sound more agresive.Also,sound was not so thight anymore.
Its hard to explain sound in my language and even harder in english.
I think lowering pre volume gives similar result,so why bother.
I only have pre gain on 9 becouse of lower noise and i compensate that(and more) with boost(gain wise)
So this trick might work in some situations,but is not the right answer for me.
Have to try Hotplate everyone is raving about,but my local stores dont have one...
The search is on.....

I don't know what the tube lay out is on a Marshall 800 2210 but oviously if you lost some gain you didn't put it in the right spot! You probally put it in V1 (tone stack) or a gain slot. In a Marshall 800 2203 and 2204 the 12AU7 would go in V3 the farest pre amp tube from where the input jacks would be.
The intent of this is not to increase gain, tho it can somewhat because it forces you to turn up the output volume (Master) if need be, thus driving the output tubes harder.
It is ment to lower the over all output volume of the amp.
I use it with a Hot Plate and the sound is thicker and darker at lower volumes. Works Great for me!

[slo100]

I have the 16 ohm version HotPlate and in my experience and to my ears, it does the most with non-master volume amplifiers. I do not really hear a difference that would be discernable in a live setting using it with master volume amps with high gain preamp circuits.

However, the HotPlate creates an amplifier that has a decent amount of gain out of my non-MV amp that I otherwise could not use for songs needing some high gain tones without punching up the signal into the front end with an overdrive or distortion pedal.

I am reading that a lot of people find value in using them with high gain amps so I suppose there is a use for some in that area.

Bret