Suggestions needed for a small tube amp

H

HamishR

Well-known member
A fella who I recently built a version of a Matchless Lightning for has asked if I can build something similar but smaller. I have explained to him that the Lightning is the smaller version, but apparently it's still too loud for some situations. He prefers not to use the master volume and I don't blame him. The amp has a MV bypass switch and it invariably sounds better with MV switched off.

So I'm thinking it might have to be a single-ended amp. Trouble is that the Lightning is quite a bright amp and most single ended amps I have tried are a bit dark in comparison. Also, the first amp he bought from me was a 5F11 tweed Vibrolux which was my first idea when he asked for a quieter amp but he's already had one and likes a Vox kinda sound. He has pedals etc etc - he wants a quieter version of a Lightning.

Any suggestions?
 
I don't know anything about building amps, but what about putting a post phase inverter master on the Lightning? Does that amp circuit lend itself to that? I've been super impressed with how John Suhr has incorporated PPI masters into many of his amps. I think most of the newer Dr Z's have them as well. I had a Suhr PT15 for a while and It was very effective in eliminating the need for an attenuator. (I still ran it through a ToneKing though.....)
 
I think the charm of the Lightning is what it is....it's not a quiet amp by any means, and it needs to be played at a decent volume to get "that" sound out of it. Which is why I've always kind of avoided Vox based amps. (Matchless, Bad Cat, etc) They're all too loud for my uses. I'm not sure what your buddy's use case is, but in a studio setting, I'd probably invest in a good reactive load box and run it direct. Ooooorrrr....build a "blast box" iso box for it and mic it up. :p
 
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The idea is to sound like the Lightning but be quieter. FWIW I have built a Vox AC15-ish amp with some of the Mojo parts, and have some more on the way to build another. The first one I used a choke (not in the Mojo kit) and a GZ34 rectifier (also not in the Mojo kit) because that made it more authentic. It sounded really good and I posted pics of it not so long ago. The fella who wants the new one is the same fella I rebuilt a Fender Princeton Reverb RI for. But this time we built it with bigger iron and it runs 6L6 tubes - It sounds amazing! Fixed the noisy reverb too. But it is very loud.

I'm not sure that a quieter Vox-sounding amp exists. Part of the problem is that tube amps sound best loud - it's as simple as that. I guess it's possible that a single-ended amp may capture some of that Vox-vibe but I can't think of one. I might have to make a small tweed with a Vox tonestack.... I once built a top-boost channel into a blonde Bassman's Normal channel. That sounded fantastic. Maybe that's the key.

Thanks for the suggestions!
 
Is he trying to get bedroom or house volume out of it? He might be better with a modelling amp. I've never seen anything which will do a matchless impersonation at low volume
 
He's gigging with it. He originally had a 5F11 tweed Vibrolux with a 12" Celestion I had built - a full 10W of mighty 6V6 power... And he was being told it was too loud, even when he used a pedal for overdrive. So then he bought a Vox 15W something (it sounded awful) and he was happy with that, so he asked me to build a small Vox-flavoured amp with a master volume. So I built the Lightning because it's very much Vox based and has a master volume. I got the chassis and board from Ceriatone.

So he wants something handmade and something tube. I have an idea...
 
What about the AC4? The old version with the ef86 and a single el84, and maybe without the tremolo circuit.

Have you thought about putting a less efficient speaker in the lightning? It's surprising what volume difference speaker efficiency makes
 
I've built a tweed Princeton with a 12" speaker before so I guess it wouldn't be so difficult to build one with an EL84. The Princeton is just a Champ with a tone control. An EL84 should run from a Champ/Princeton PT ok shouldn't it? Should be pretty straightforward.

As an aside - I wonder what a tweed Vibrolux with EL84s would sound like? I love the 5F11 circuit - but I leave out the NFB. My friend has no need for tremolo but it might be a nice build for me.
 
How have you attenuated at V1 grid? I'm starting to warm to the idea of an EL84 Princeton. I have a feeling that as long as I can make the amp relatively bright my friend will be happy. And I hear you re grid stoppers. Mr Psionic is quite vocal on the idea too.
 
That all makes sense. I use the 680nF cathode bypass cap on a lot of these small amps because too much low frequency at the front end is a big problem. I did that in the Lightning, the Vox and usually in a 5E3. In fact the only time I have increased the size of caps lately was in the Marshall 1974 build. I try to reduce the coupling caps in size through the amp (if necessary) in a kind of proportional way. In other words if I need to reduce the amount of low frequencies in the amp I don't try to achieve it all at one point. I think it's important to reduce most of the caps in the signal path by similar amounts, although I rarely mess with the tone stack. It's largely as you have done.

I never got into the Valve Junior thing! Thanks for the info.
 
jubal81 said:
I added a voltage control to my PP EL84 amp and love the results.
Click to expand...
When I made the Bass channel in a blonde Bassman clone into a Top Boost channel I was amazed at the difference changing the dropping resistor in the dog house made. When I first had a sound test of the amp I had the standard value dropping resistor feeding the B+ to that channel. The new Top Boost channel sounded quiet but very, very distorted, in a creamy, beautiful way! Checking the voltages I found that the B+ was way too low for a Top Boost style preamp, so gradually reduced the value of the dropping resistor until I reached Vox/Matchless voltages there. It still broke into dirt but at a much higher volume - it was around noon on the volume pot. It wasn't as creamy but still a beautiful sound, and now I had some clean headroom too.

The reason I decided to turn that Bass channel into a Top Boost channel is because in that amp (unlike most Fenders) the Bass channel used two 12**7 tubes and had Volume, Bass and Treble knobs on the front. So turning it into a Top Boost channel was easy. It sounded so good I rarely used the normal channel, which was the reason I built the amp!
 
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