Tube preamp+power amp+attenuator as an inline effect

[Taylor]

If anybody here is familiar with the Hughes and Kettner half-rack preamps (Cream Machine, Blues Master, Metal Master, BATT), they used an interesting scheme with a high voltage tube preamp and a power tube to get 1-5 watts, then an attenuator built-in. They could be used as full tube power amps, or as preamps with the sound of a tube power amp. They had outputs to plug into headphones, speakers, or into SS power amps or effects.

Has anyone built anything like this? It would be a challenge, but I think it would get you that elusive power tube distortion into headphones, or into a solid state power amp so gain in the preamp tubes and power tubes could be controlled independently of volume. Also, I like to use spring reverb, but I don't like having my reverb distorted; I'd rather have my distortion reverberated.

Any thoughts on the smartest way to approach this? Is there a reason I'd want to get up to a couple of watts, then attenuate down from there, as opposed to only getting up to a hundred milliwatts or so?

[frequencycentral]

Interesting idea, I've never come across that HK.

Is there a reason I'd want to get up to a couple of watts, then attenuate down from there, as opposed to only getting up to a hundred milliwatts or so?

As I understand it there are three 'parts' to 'that' tube amp sound, triode preamp and pentode power amp crunch are different, each having their own harmonic signature, transformer saturation get you the rest of the way there. So if you're dealing with just milliwatts you'd be missing out on a good part of it.

[Salvatore]

I have the Cream Machine and Metal Master.
The Cream Machine suffers from a serious lack of bass, I guess cause of the small output transformer.
The Metal master just is a 2 tube preamp with transistor power amp, and cause of the better bass sound, I like it better.

Both, I think, are not so well suited for diy, far to complex for what it delivers.
A much simpler design can be found on the ax84 site, the firefly, a 1/2 watt marshal simulator in pushpull mode, which will do most what the Cream Machine does, with all the tweaks and gadgets tried.

[Tubebass]

Also have a look at the Garnet Herzog.

[Ripthorn]

I would think that it would require a good bit of space to put all that together, and then my opinion is "well, why not just have a little amp that you can hook up to a speaker".  Then you can run an attenuator to a more powerful power amp if you want.

[sean k]

I'm also of the opinion that the output transformer and the speaker on the end do so much of the shaping. Nothing like sag as the power supply tries to grab current that ain't available and the OT saturates then the speaker does it's harmonic thing through alnico magnets and paper cones... into a room that really works. So much is about whats after the power tubes that your attenuater would be a true work of art to assimulate all those mechanical variables.

Don't let that stop you though... how else do we progress other than doing something that it seems somewhat pointless to do. That is what opens up all new areas for exploration and triggers new insights.

[petemoore]

   ...Champ with an 8R tacked on the end...
   The one guy I read about found out what he found out.
  Noisy, and can be particularly useful when he used the amp-amp [what the HZog drives] totally cranked, he mentioned 50w Marshall, 100% volume.
  He also mentioned physically controlling or otherwise gating out the noise-spaces [ie when the signal dropped below 'x', which I ascertained correctly or incorrectly as fairly often, noise quickly and forcefully creeped in]...which seems logical, and is what I noticed when...
  I stuck a 10R on the OT of my 6SN7 PP Amp. Although there seems to be potential for Zog-Tone, only a glimpse is what I expected and got. It performed pretty much as I expected. Noisey, somewhat rough distortion...from an experiment which is '~slipshod'...not exactly the best test elements...easy to do and 'proved enough for me to consider continuing to aquire non-linear signal transfers using other, simpler methods.
  I could persue the Zog-Tone further, it just seems like the long way to get around the barn to me at this point, so I probably won't. Perhaps something with an input sensitized / noise gate near-ish the OT might work better.
  12 or 9v effects have proved themselves quite useful already...just crank the amp into reactive load [speaker] and put an NPNBoost, Jfet or whatever you like, in front, to put a kick on the input wave swings, you may not be riding the exact shape of a Zog-Wave but...Surf's Up!
 

[Ben N]

Doug Hammond has been there, done that, got the t-shirt, published the results. Do a search, here and on the internets, for Firezog.

[ninjaaron]

I did something similar with my Univalve, except no attenuator. The Univalve has a dummy load when there is no speaker plugged in, so you can just go direct from the line out (which taps the signal from the power amp, not just the pre), and then I ran that into a multi for delay and reverb, and then into another amp.

It sounded great. Probably the best tone I've gotten.