Hot Plate question

[tt0511]

I just got a 16 ohm hot plate for my peavey classic 30.  The hot plate inputs and outputs are 1/4" jacks, and my amp speaker wires are just wires with slide on clips that attach to the speakers, just like a car audio speaker.  The guy at the store said I would have do the following to get the Hot Plate to work:

1.  Remove the wires from the power amp to the speaker and install a 1/4" jack on those wires.  Then connect that to the input of the Hot Plate.
2.  Take unshielded speaker wire and install a 1/4" jack on on one end.  Connect that end to the output of the Hot Plate.  Connect the other end of this wire to the speaker by soldering or installing more clips that slide on, ...like what's on there now.

I didn't have a problem with that but I just thought of something:  What happens when I plug my extension cab in?  I then have a 16 ohm Hot Plate breaking only one speaker, ..and my understanding is that when the extension cab is plugged in, ...a 16 ohm speaker, the amp operates at 8 ohms.  So then there is a 16 ohm Hot Plate operating on a 8 ohm system.  This doesn't sound good.  How do I do this?

 

[tt0511]

Okay, I just found a manual on THD's website.  They say that I would need an 8ohm Hot Plate to connect both my 16ohm speakers (the one in the combo amp and the one in the extension cab) so I'm not going to be able to do that.  Will it work to simply disconnect the Classic 30's internal speaker and run the hot plate between the extension cab jack and the extension cab?  In other words, if I disconnect the amp's internal speaker and only use the external cab, will it operate at the required 16 ohm load?

If so that would keep me from having to hack into the Classic 30's speaker wiring.

 

[Superlizard]

Quoting myself from a while back:

http://www.unofficialwarmoth.com/index.php?topic=7610.0

To quote Ed DeGenaro on a question I asked him years ago on the Plexi Palace BBS:

posted June 20, 2002 08:44 AM

Here's the deal...a matched impedance IMO always sounds better.
The Hotplate you'd want for both 8 ohm cabs is a 4 ohm model. BUT, you can use the 8 ohm model with them, just make sure to set the amps impednce to 4 ohm when using both cabs.

The 8 ohm Hotplate won't be as efficient as the 4 ohm in this application. Since we do compensate for the Fletcher-Munson curve the boost switches frequency peaks will be a bit off. But it's still better than any other option unless we're talking matched load.

That said, I've been using a 16 ohm Hotplate since years on all my 8 and 16 ohm loads myself.

Ed DeGenaro
Product Development & Support
THD Electronics, Ltd.

 

[tt0511]

Okay, so although the hot plate doesn't match "perfectly" to an 8 ohm load, I can use it either way for 16 or 8?  Not sure if I want to run just my combo amp or run it with the extension cab.  I can easily plug the extension cab in afterwords though if I want more presence.

That being the case, is this how you'd wire it?

Solder some speaker wire to the speaker tabs and put male 1/4" jacks on the ends of those wires to allow connection.  Install male 1/4" jacks on the wires between the amp and the speaker.  That would allow the hot plate to be removed and the speaker to be reconnected in the stock configuration by connecting the two male connections via a double female coupler.

( the wires going from amp to speaker currently do not have 1/4" jacks on the ends but speaker tab fittings like this:  http://images.auctionworks.com/hi/68/68411/nc144.1.jpg )

 

[tfarny]

What Super Lizard is saying is, you'll be just fine if you go amp -> 16 ohm hot plate -> 8 ohm cab. The EQing may be a little bit off, which is why you have all those knobs on the front of your amp, on your pedal board, and your guitar.

 

[mayfly]

What Super Lizard is saying is, you'll be just fine if you go amp -> 16 ohm hot plate -> 8 ohm cab. The EQing may be a little bit off, which is why you have all those knobs on the front of your amp, on your pedal board, and your guitar.

Hold it there, partner.  You don't know what impedance will be present at the output of the amp with this rig.  That means that you don't know what impedance will be reflected to the plates of your output tubes.  Running the rig like this loud (which is of course the entire point) may damage your tubes and/or your output transformer.

It's better to stick with like impedance with attenuators because of the power levels you'll be running at.  What's the output impedance of your amp?  That's the first question. Can you switch it from 8 or 16 ohms? 

If you can switch your amp to 16 ohms, set it to 16 ohms, hook it up to your 16 ohm hotplate, and then find a 16 ohm speaker load to run it into.  If your speakers (internal and external) are both 8 ohms - run them in series and you're good.

 

[tt0511]

The amp is rated at 8 and 16 ohms, but there is no switch.  From reading the manual and the forums on Peavey's website I have discovered that the amp runs at 16 ohms.  The amp comes with a 16 ohm internal speaker.  The output jack says "16 ohm minimum load".  Here's a pic of the back of the amp.  There is a 16 ohm Vintage 30 in the amp, and the extension cab has a 16 ohm vintage 30 in it.  When the external cab is connected, the amp runs at 8 ohms automatically from what I've read on the Peavey forums.  There is no switch on the amp to change the rating.

 

[mayfly]

I think I know what's going on.  The output jack of the amp for the extension cab is probably switched to switch to an 8 ohm winding for both speakers when something is plugged into it.  I'll verify if I can find the schematic for this amp.

 

[mayfly]

I think I know what's going on.  The output jack of the amp for the extension cab is probably switched to switch to an 8 ohm winding for both speakers when something is plugged into it.  I'll verify if I can find the schematic for this amp.

Just checked the schematic.  Yep - when you plug a speaker into the extension cab, it disconnects the 16 ohm winding and connects up the 8 ohm winding instead.

Here's the schematic BTW: 

So for your use, you need to connect the attenuator between the amp and your built in speaker, and not use the extension cab.  Your mod will work, provided you are careful to get good mechanical and solder connections on your splices.  Don't forget to insulate your connections.

 

[tt0511]

I have some soldering experience.  I can handle that part.  I got the cable prepped and ready for tinning and soldering Monday tonight.  Hopefully I'll get to test drive it then.

 

[Superlizard]

What Super Lizard is saying is, you'll be just fine if you go amp -> 16 ohm hot plate -> 8 ohm cab. The EQing may be a little bit off, which is why you have all those knobs on the front of your amp, on your pedal board, and your guitar.

Hold it there, partner.  You don't know what impedance will be present at the output of the amp with this rig.  That means that you don't know what impedance will be reflected to the plates of your output tubes.  Running the rig like this loud (which is of course the entire point) may damage your tubes and/or your output transformer.

It's better to stick with like impedance with attenuators because of the power levels you'll be running at.   What's the output impedance of your amp?  That's the first question. Can you switch it from 8 or 16 ohms?  

If you can switch your amp to 16 ohms, set it to 16 ohms, hook it up to your 16 ohm hotplate, and then find a 16 ohm speaker load to run it into.  If your speakers (internal and external) are both 8 ohms - run them in series and you're good.

You have a point under typical amp+speaker situations, but apparently you missed what Ed DeGenaro said regarding
HotPlate "impedance ratings" (see my above post with his quote).

 

[Superlizard]

What Super Lizard is saying is, you'll be just fine if you go amp -> 16 ohm hot plate -> 8 ohm cab. The EQing may be a little bit off, which is why you have all those knobs on the front of your amp, on your pedal board, and your guitar.

That's correct.

Normally one wouldn't mismatch (especially with a smaller speaker load e.g. amp - 16ohm / spkr - 8ohm), but the HotPlate is an exception.

All one has to make sure is the *amp* & *cab* are matched, or at the very least, the speaker is higher (e.g. amp - 8ohm / spkr - 16ohm)...
the ohms rating on the HotPlate is only a (actual usage) consideration *tone-wise* (for example, the "Bright" & "Deep" switches on it).

 

[Superlizard]

The amp is rated at 8 and 16 ohms, but there is no switch.  From reading the manual and the forums on Peavey's website I have discovered that the amp runs at 16 ohms.  The amp comes with a 16 ohm internal speaker.  The output jack says "16 ohm minimum load".  Here's a pic of the back of the amp.  There is a 16 ohm Vintage 30 in the amp, and the extension cab has a 16 ohm vintage 30 in it.  When the external cab is connected, the amp runs at 8 ohms automatically from what I've read on the Peavey forums.  There is no switch on the amp to change the rating.

16ohm amp + 16ohm speaker + 16ohm HotPlate = perfect.

You're good to go.   :icon_thumright:

 

[tt0511]

:headbang:    :hello2:  arty07:  :blob7:

Yeah, ...I just got the hot plate installed tonight and tested it out for about an hour.  BOY AM I HAPPY!!!!  This wrocks!!!  There is so much tone I've been missing it's just unbelievable.  The top end sparkle and dynamics I'm hearing are something I actually haven't heard come out of my amp before.  At the -16db rating, I was able to crank the amp up to 8 very comfortably.  The -16db rating is a little kill-tone but it's still WAY better than not having a hot plate at all.  I will likely use it on -8db or -12 db most often because I like the tone better there and can pull the volume back a little and not really sacrifice much.  Whoo Hoo!

My advice for those curious about the hot plate is GET ONE.  But, I'd get one used because they do cost an arm and a leg.  It's worth the used price for sure.  You'll forget about the money in a couple of weeks and get to enjoy killer tone for the rest of your life.  Thanks Superlizard for recommending that attenuator scenario.  I was in the dark and had no idea this kind of thing existed.  I'm almost speechless, ...but obviously, ...not quite, ha ha.

 

[Superlizard]

:headbang:    :hello2:   arty07:   :blob7:

Yeah, ...I just got the hot plate installed tonight and tested it out for about an hour.  BOY AM I HAPPY!!!!  This wrocks!!!  There is so much tone I've been missing it's just unbelievable.  The top end sparkle and dynamics I'm hearing are something I actually haven't heard come out of my amp before.  At the -16db rating, I was able to crank the amp up to 8 very comfortably.  The -16db rating is a little kill-tone but it's still WAY better than not having a hot plate at all.  I will likely use it on -8db or -12 db most often because I like the tone better there and can pull the volume back a little and not really sacrifice much.  Whoo Hoo!

My advice for those curious about the hot plate is GET ONE.  But, I'd get one used because they do cost an arm and a leg.  It's worth the used price for sure.  You'll forget about the money in a couple of weeks and get to enjoy killer tone for the rest of your life.  Thanks Superlizard for recommending that attenuator scenario.  I was in the dark and had no idea this kind of thing existed.  I'm almost speechless, ...but obviously, ...not quite, ha ha.

PARTAY!  :toothy10:

 

[tt0511]

I just want to thank all you guys who chimed in to help me out with the amp, gear, hotplate, etc. questions, and giving your input and advice.  It is much appreciated!  That makes this forum the best forum I've been on.  You guys are great!

 

[Superlizard]

Ain't nuffin' like the tone of powert00bs workin'... that's where all the magic comes from.

Preamp distortion buzz = p00000p

 

[tt0511]

Now that I've got my toobs working, I'll be able to make a better comparison between my amp and the software modeling.  What I found REALLY awesome last night was cranking the amp's clean channel until it breaks up and then experiencing the different dynamics between picking soft or hard.  That's there at very low volumes, but it doesn't change the tone like that, more like just the volume.  It just kills.  That nice round, popping, full, warm clean sound by playing softly or rolling off some guitar volume, ...gets that kind of Angus clean tone thing going on.  Whoo Hoo.  I'm more excited about my amp now, that's fer sure.

 

[tfarny]

Welcome to the world of real amplifiers, son....

 

[mayfly]

Glad that you are now getting the tone you are looking for.  Congratulations!  :icon_thumright: