# Using a tube amp head as a preamp with no speakers attached?



## JPhoenix19 (Nov 18, 2010)

Ok, so instead of bumping a year-old thread similar to this topic I decided to start a new one. I've been using my Google-fu, but found nothing in regard to the specific question at hand. See, I was searching the forum for information about the HT-5 and I came across this video:





Awesome tone! This video is actually part of what swayed me toward getting an HT-5. Anyway, in the comments the person seems to say that he just uses his HT-5 as a preamp, connecting its effects send straight to his VHT 2/50/2. I know I've seen many times that running a tube amp without speakers (without a load on the output transformer) is very very bad, but if your signal is going out of the effects send then no signal is being put on the output transformer, so no damage should be incurred, right? So theoretically, using the HT-5 as a preamp with no speakers attached could theoretically be a viable option? Or is it imperative that a load be put on the HT-5, and I should get something like this and make a load-box thingy. I'm asking because I want to be able to run this through a power amp if I need more power sometime in the future.


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## Pif (Nov 18, 2010)

99% of tube amps that I've used are essentially a preamp and a poweramp in the same chassis. The beauty of a master effects loop is that it falls right between the two; so the send is technically a preamp OUT and the return is a poweramp IN. Before I could afford my stereo poweramp for my rack, I was running my Randall RM4 into the effects loop return of a Genz-Benz Diablo, using the Diablo only for the power section and skipping the preamp alltogether. You would be doing the same thing in reverse: running the signal out of the HT-5 and into a dedicated poweramp. There's no worry of running the HT-5's power tubes without a load on them since the signal leaves the head before passing through the power stage. I'm sure there are rare cases of heads that integrate the preamp and poweramp no matter what signal is present at the effects loop, but not in any modern head I've played. Hope this helps!


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## Ostia Man (Nov 18, 2010)

with some amps the preamp is still active wile the power section is in standby. like marshall amps. I have done this with out any speaker conected to the marshall because is in standby. not pocible with a rectifier. not sure about the ht-5


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## jaco815 (Nov 18, 2010)

Do not have an amp turned on without speakers connected. It's too damned easy to flick that standby switch on accident and then you're out an amp. If you want to use it as a preamp, just use the effects send out with the standby switch on. On my buddy's Blackstar, the effects send without a return does not bypass the poweramp; the effects send is parallel so he has to flick the standby switch on to shut off the amp. He is able to monitor his guitar playing through his amp while recording the effects send out to impulses at the same time, nut to play through the impulses only, the standby has to be engaged.


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## aiur55 (Nov 18, 2010)

Not all amps can do that. Like the fireball 60 can't do that, someone knowledgeable once told me. Ofcourse, I have never tried it and ended up selling the amp before I got the chance.


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## Wookieslayer (Nov 18, 2010)

Nice dude! I was thinking of posting something similar except I was wondering what would happen if someone ran a V2 or T2 into a sick Mesa or Fryette power amp!


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## JPhoenix19 (Nov 19, 2010)

Thanks for the input, gang.  I'll try running the signal from the effects send with the amp on standby, and we'll see if that works. Since I'm considering running my HT-5 4-cable method with a MFX, I could theoretically use the HT-5 to power a smaller cab in the front of the stage for monitoring- or just make a load box to be safe.


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## Toshiro (Nov 19, 2010)

I would use a load box, like a weber attenuator.


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## petereanima (Nov 19, 2010)

The only problem with the "Amp-on-standby with no load"-version (besides the possibility of swtiching the standby on per accident), is, that this is really not healthy for your tubes, because "modern" Standby switches do heat the tubes, and having you amp on standby for too long heats the tube but cuts off plate current - that can cause cathode poisoning. 

The HT-5 uses what? A 12BH7 or something? Not really an investment, but for the folks using expensive powertubes (and lots of them), i wouldnt want to make an unnecessary risk. Better attach a load/cab, and just turn master-volume to zero.


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## Pif (Nov 19, 2010)

petereanima said:


> The only problem with the "Amp-on-standby with no load"-version (besides the possibility of swtiching the standby on per accident), is, that this is really not healthy for your tubes, because "modern" Standby switches do heat the tubes, and having you amp on standby for too long heats the tube but cuts off plate current - that can cause cathode poisoning.
> 
> The HT-5 uses what? A 12BH7 or something? Not really an investment, but for the folks using expensive powertubes (and lots of them), i wouldnt want to make an unnecessary risk. Better attach a load/cab, and just turn master-volume to zero.


 

Very good point, bro!


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## JPhoenix19 (Nov 19, 2010)

I was considering making a load box just to be on the safe side. I've read that a 16- or 8-ohm 20 watt resistor wired to a 1/4" jack might work for the HT-5. I guess it's time to research how to make a load box!


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