New (approx) 1 watt amp

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John Kingma
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New (approx) 1 watt amp

Post by John Kingma »

A friend of mine builds tube amps from old TVs, stereos and other bits of electronic junk. He recently put together this little gem and when I heard it I just had to have it. So we made a trade and I'm going to be doing some work on an SG project we wants to get started on.

It's made from an old Electrohome FM Multiplex unit. He designed the circuit that he put into it... which I really don't understand anyway. It uses a 12ax7 preamp tube and a 6sn7 power tube. It has incredible sounding overdrive for such low wattage.

Here's his YouTube video... and I'll post some pictures.

http://www.youtube.com/watch?v=CHVwA6KpzpI

It measures about 9" long x 4" wide x 6" high
1wattamp001.jpg
1wattamp002.jpg
1wattamp003.jpg
The original Electrohome stickers are still attached.
1wattamp004.jpg
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Nick Middleton
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Re: New (approx) 1 watt amp

Post by Nick Middleton »

That's funny you bring that up. Marshall is making a bunch of 1W amps now as well. They have different ones designed to be like the 60's, 70's, 80's, JCM's, etc.

For a while now I've been seeing a 5W bandwagon with the different makers. This is probably the beginning of a new trend. 1W is still pretty loud for practicing at home or low-volume jams & recording.

Maybe people are finally realizing they don't need 100+ Watt stacks to get a good tone!

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Greg Robinson
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Re: New (approx) 1 watt amp

Post by Greg Robinson »

Nice little amp John!
I repair tube amps (and guitars) full time, and hang out a lot on ax84, is your friend also a member there? 12ax7 and 6sn7 is a popular combo with the members there.

Hopefully I'll have some amp builds of my own finished to contribute here soon.
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David King
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Re: New (approx) 1 watt amp

Post by David King »

I wish every budding electric guitarist I'd ever played with had used one of these. I bet my hearing would be better now. Too many twins and jcm 800s out there in inexperienced hands.
I hope these amps become standard equipment.

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Greg Robinson
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Re: New (approx) 1 watt amp

Post by Greg Robinson »

And roadies with back injuries! A 100W amp is only 4 times as loud as a 1W, using the same speakers. And most cheaper instrument speakers have poor efficiency. A nice 30W guitar speaker with 113dB 1W/1m with a 1W amp is plenty gigging loud!
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Jason Rodgers
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Re: New (approx) 1 watt amp

Post by Jason Rodgers »

DIY amps? ax84? A whole new world of geekery to consume my time and prevent me from completing anything!!!
-Ruining perfectly good wood, one day at a time.

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Mark Swanson
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Re: New (approx) 1 watt amp

Post by Mark Swanson »

Cool amp! I love small amps, and I have three Epiphone Valve Jr's that I have modded and they are great. I used one to gig for quite a while but I do prefer my blackface Deluxe Reverb for that now.
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John Kingma
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Re: New (approx) 1 watt amp

Post by John Kingma »

Greg Robinson wrote:Nice little amp John!
Thanks Greg.

Greg Robinson wrote:I repair tube amps (and guitars) full time, and hang out a lot on ax84, is your friend also a member there?
Not sure... he really isn't big on internet stuff other than his own website, which someone else looks after for him. I'll mention ax84 to him next time we chat.
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John Kingma
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Re: New (approx) 1 watt amp

Post by John Kingma »

Mark Swanson wrote:Cool amp! I love small amps,
Me too, but until now I haven't heard one that really flipped my switch.

Right now when I use it I'm plugging in a speaker from a bigger amp that I have... but some day I want to make a small cabinet for it with an 8 or 10 inch speaker in it.
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Jason Rodgers
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Re: New (approx) 1 watt amp

Post by Jason Rodgers »

I've been reading up on the P1 project on ax84 and I think I could do that! Here's a general amp construction question, though: is it necessary that your chassis be made of sheet metal? Could one use plywood with copper tape/sheet on the inside for grounding?
-Ruining perfectly good wood, one day at a time.

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Greg Robinson
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Re: New (approx) 1 watt amp

Post by Greg Robinson »

Hi Jason,
While that can be made to work, the biggest problem is that with the temperature rise of components inside the wooden "chassis", it can quickly become a fire hazard. Wood is a very poor conductor of heat. It can also be subject to fluctuations in moisture content, and with the high voltages used in tube circuits, this can present a further hazard.
it's certainly been done, and is still done by many, but I'd suggest you stick with kits or at the very least metal chassis until you get a good understanding of heat dissipation in components and tubes.
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Rodger Knox
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Re: New (approx) 1 watt amp

Post by Rodger Knox »

Greg Robinson wrote:And roadies with back injuries! A 100W amp is only 4 times as loud as a 1W, using the same speakers. And most cheaper instrument speakers have poor efficiency. A nice 30W guitar speaker with 113dB 1W/1m with a 1W amp is plenty gigging loud!
What speakers have a sensitivity of 113 dB 1W/1m? The best I've found are 103...
+1 on AX84 for tube amps, I've built the P1 extreame.
A man hears what he wants to hear, and disreguards the rest. Paul Simon

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Re: New (approx) 1 watt amp

Post by Nick Middleton »

Yeah, I made a P1 ex and now I've converted it to an SEL. It's my main amp I gig with!

AX84.com is a good starting-point into DIY amp stuff

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Greg Robinson
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Re: New (approx) 1 watt amp

Post by Greg Robinson »

Rodger Knox wrote:What speakers have a sensitivity of 113 dB 1W/1m? The best I've found are 103...
I can't think of any guitar speakers off the top of my head, but some smaller speakers (a lot of headphones are in that vicinity and higher), and old (vintage) PA speakers in particular are way up there in efficiency. When bandwidth wasn't the primary concern, and only (relatively) low-powered amplifiers were available, they really pushed the limits of efficiency in speakers.
If you ever get your hands on an old Rola PA speaker, they make really great LOUD guitar cabs.
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Rodger Knox
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Re: New (approx) 1 watt amp

Post by Rodger Knox »

Are we talking about speaker efficiency, or sensitivity? Efficiency is the acoustic power out/electrical power in, usually experssed as a percentage. Sensitivity is a different thing, and the units you used leads me to believe that is what we're talking about.
Back in the day, I ran a 100 watt Traynor tube amp through two 15" JBL D-130s, they're sensitivity is about 103dB/Watt/Meter. I never turned up past 3, even in outdoor shows. That was when you needed 100 watts because you couldn't turn up past about 30% without getting distortion from overdriving the tubes. :o I could run my 5 Watt 8 track player through them and they'd still make your ears bleed.
A man hears what he wants to hear, and disreguards the rest. Paul Simon

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Greg Robinson
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Re: New (approx) 1 watt amp

Post by Greg Robinson »

Yes, sensitivity is what I mean, you never hear efficiency percentages quoted for speakers (they're a smaller number: 3-5%!), but they're directly related. Should have used the correct terminology though, sorry.
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David Schwab
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Re: New (approx) 1 watt amp

Post by David Schwab »

John Kingma wrote:It has incredible sounding overdrive for such low wattage.
The low wattage is why it has such good overdrive. It has no headroom for a clear tone.

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Re: New (approx) 1 watt amp

Post by Art Davila »

Nick Middleton wrote:That's funny you bring that up. Marshall is making a bunch of 1W amps now as well. They have different ones designed to be like the 60's, 70's, 80's, JCM's, etc.

For a while now I've been seeing a 5W bandwagon with the different makers. This is probably the beginning of a new trend. 1W is still pretty loud for practicing at home or low-volume jams & recording.

Maybe people are finally realizing they don't need 100+ Watt stacks to get a good tone!
Yes and many guitarist are going deaf, and so they want some lower power amps to give just enough volume to be mic'ed and let the bulk of the volume to be in the PA speakers giving the audience the ear piercing volume once in awhile artist saves his hearing on a nightly basis. I have a heard that Eric claption and many other iconic guitarist have made their recording in the studio with fender champs and other very low wattage amps.
I have a lot of experience on how "not" to do things.

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Beate Ritzert
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Re: New (approx) 1 watt amp

Post by Beate Ritzert »

David Schwab wrote: The low wattage is why it has such good overdrive. It has no headroom for a clear tone.
Please let me disagree on this. My two Valve Juniors (btw, heavily modded...) are way too loud as practise amps even for bass (and the sensitivity ob bass capabale chassis is audibly lower than that of guitar speakers with their lower bandwidth). They are even loud enough as bass amps with not too loud drummers.

In my youth i made guitar noise through my 1.5 Watts transistor radio - and that had plenty of headroom for practising "clean".

So amps like the little toaster imo have a lot of sense.
(Use a power soak instead of the speaker and amplify that signal by a class D amp ... You'll get everything You need from the tubes and all the power You might think You need)

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David Schwab
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Re: New (approx) 1 watt amp

Post by David Schwab »

Greg Robinson wrote:And roadies with back injuries! A 100W amp is only 4 times as loud as a 1W, using the same speakers. And most cheaper instrument speakers have poor efficiency. A nice 30W guitar speaker with 113dB 1W/1m with a 1W amp is plenty gigging loud!
Only if all you want is distortion!

I have a nice little Vox VT-80+. It's a hybrid modeling amp, and uses a 12AX7 to simulate a push pull power amp stage. So it feels and sounds like a tube amp. It's 31 pounds, and has a 12" speaker and is 120 watts. Has a power attenuator too. Sounds as good as my friend's all tube AC-15. And that thing is heavy!

That's all the guitar amp I need for gigging. :D

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