Valve/Tube Guitar Preamp

[Tod Gilding]

I haven’t been very happy with the tone that I have been getting from my handmade Acoustic pickups. I make something similar to the K & K using 3 piezo discs and have been experimenting with different arrangements such as encasing the discs in different materials, I am now getting a good tone but I thought that it could be a lot better, so I picked up this little $30, Tube/Valve Preamp Kit and put it together, the tone using this preamp is fantastic, I can highly recommend them to anyone looking to improve a guitars tone Acoustic or electric, Bass
This preamp has 2 Dip switches that act as high and low pass filters to tailor the sound to a particular instrument however if being used with a bass guitar or HiFi system, a capacitor needs to be changed for a .022uf
It also has a 1M trimpot for gain and is based on two low power consumption Raytheon JAN6418 sub- miniature pentodes, these tubes were designed for the Audio Technica AT 3060 valve condenser microphone that retails for $600US.
These Valves run cool and can only be seen glowing in a very dark area due to the 1.2V filament drawing only 10mA , the whole preamp draws just 11mA from a 9V battery , the circuit checks the battery power at startup and has a LED that flashes once if the battery is above 7V and will remain on continuous if the voltage drops below this .
The tubes, like all tubes they are micro phonic but with 2 rubber grommets placed over the tubes this is reduced considerably and makes this preamp suitable for mounting internally in the guitar or externally as I have done with this particular one so that I can experiment with different instruments.
It took me about 1 ½ hrs to solder the components which are all marked on the PCB , a little like painting by numbers .If I can do it anyone could. A Highly recommended little preamp.

http://secure.oatleyelectronics.com//ad ... 2&x=15&y=5

[Tod Gilding]

I should add that I have had no RFI ( frequency interference )with this unit testing on the bench, but that doesn't mean anything.I plan to enclose this Preamp in a case (pictured ) and will line the case with copper and possibly encase the board in foam to prevent RFI and vibration, will report back when this is done.

[Allen]

So Todd. You do any more testing on this unit? I'm pretty interested in your results, and how you've integrated it into the rest of your set up.

[Tod Gilding]

Yes Allen I have it set up as an external preamp and have tried it out with quite a few different guitars electric and acoustic, I can't speak highly enough of it IMHO I think it is a great bit of kit when put inline with any PASSIVE system either piezo disks or undersaddle compression type tranducers I havnt tried it with the K&K disk type pups but can see no reason why they wouldn't be as compatible as any other piezo disc.

I am planning on mounting this internally in a dread build that will come as soon as I can get my current build completed, the only thing with it is no EQ from the guitar this needs to be done from the PA or AMP but I dont see this as a problem.

Bottom line is that the results have been positive. it took me about 2 hours to solder it up if time is not a problem then a high quality great sounding preamp can be built very cheap.

it also has a high and low pass filter that can be used to talior the output for a particular instrument and a gain pot, but once set for a particular instrument there is no need to access these controls again.

hope I covered what you wanted to know if not let me know

[Kim]

Thanks for the update Tod, think I will give one of these a go myself.

Cheers

Kim

[Tod Gilding]

These pre's do give a nice warm valve tone but don't expect what you would get from a couple of EL 34's

[Kim]

These pre's do give a nice warm valve tone but don't expect what you would get from a couple of EL 34's

Yeah well just as long as it can push our small intimate venue stack into overdrive it'll work out just fine thanks Tod.

Here's left stage...

AAA_SV Stack.jpg (52.63 KiB) Viewed 20558 times

Check..One...Twwoooooo. Check..One...Twwoooooo..Ttttwwooooooo...Check..Check, Pahh...Pahh...Chiishh!..Chiishh!...Wonnnnah!!..Wonnnnah!!.... Toooooowh..

Cheers

Kim

[Tod Gilding]

Kim you may need to add another Battery that stack looks like it would need at least 18v

[J.F. Custom]

Kim you may need to add another Battery that stack looks like it would need at least 18v

He could try this -


youtu.be/

[kiwigeo]

lucky the household cat wasn't hanging around

[ozwood]

What a dickhead,

I work at an Electrical Engineering/ Manufacturing company and we spend most of our time making things to keep people safe , and that Guy is asking for death , just cause they are batteries does not mean they can't kill you.

the human body resistance can be as low as 300 ohms, depending on such things as how sweaty a person is, wet clothing, skin punctures/bleeding, etc.

Humans can feel 0.001 amps as a tingle. (1/1000 amp)

Involuntary muscular contractions begin at about 0.01 amps. (1/100 amp)

Death can occur as low as 0.1 amp (1/10 amp)

If you were to grab a live wire and 0.01 amps were conducted through the muscles in your arm...you may not be able to let go.

If you were to have 0.1 amp conducted across your chest, that is enough current to make your heart either stop or fibrilate...and you die.

At 30 volts, with a body resistance of 300 ohms, you will get a current flow of 0.1 amps.

I = V/R = 30 volts divided by 300 ohms = 0.1 amps.

So, under unfavorable conditions, a voltage as low as THIRTY VOLTS CAN KILL, because this will draw 0.1 amps through the heart if the current path is across the chest.


2000 Volts from batteries would have a potential surge current of at least say 10 - 20 amps , that bloke is lucky he's not dead.

and as a side note, that was more than an arc that was the air turning to plasma , he's also lucky he did not peel the skin off his hand and send himself blind.

I hope no Teeenages see that and give it a go.

and so endith my electrical safety rant!

[Allen]

Is there anything else that is not included in the kit that would need to be purchased Todd? I was looking at having an external one to try out on ukuleles.

[liam_fnq]

What a dickhead,

I work at an Electrical Engineering/ Manufacturing company and we spend most of our time making things to keep people safe , and that Guy is asking for death , just cause they are batteries does not mean they can't kill you.

the human body resistance can be as low as 300 ohms, depending on such things as how sweaty a person is, wet clothing, skin punctures/bleeding, etc.

Humans can feel 0.001 amps as a tingle. (1/1000 amp)

Involuntary muscular contractions begin at about 0.01 amps. (1/100 amp)

Death can occur as low as 0.1 amp (1/10 amp)

If you were to grab a live wire and 0.01 amps were conducted through the muscles in your arm...you may not be able to let go.

If you were to have 0.1 amp conducted across your chest, that is enough current to make your heart either stop or fibrilate...and you die.

At 30 volts, with a body resistance of 300 ohms, you will get a current flow of 0.1 amps.

I = V/R = 30 volts divided by 300 ohms = 0.1 amps.

So, under unfavorable conditions, a voltage as low as THIRTY VOLTS CAN KILL, because this will draw 0.1 amps through the heart if the current path is across the chest.


2000 Volts from batteries would have a potential surge current of at least say 10 - 20 amps , that bloke is lucky he's not dead.

and as a side note, that was more than an arc that was the air turning to plasma , he's also lucky he did not peel the skin off his hand and send himself blind.

I hope no Teeenages see that and give it a go.

and so endith my electrical safety rant!

It doesn't work like that Paul. If you could get 10-20 amps out of circuit, he'd have had a fire to put out. The batteries simply can't supply enough current to make Mr Ohm ring true. The voltage drops (voltage regulation) too. Anyone who's used a megger or rubbed their feet on the carpet and then touched the cat would be familiar with high voltage, low current shocks.

I'm not saying that the blokes not an idiot or that he couldn't have hurt himself, just that your claims don't ring true.

Also anyone who has jump started a car would be familiar with the idea that batteries in series increases the voltage but not the current while in parallel the current increases and the voltage stay the same. (perfect world situation).

[Tod Gilding]

I have mine set up like this in a plastic food box, the only additional things required where the two jack plugs and a toggle switch to turn the power on and off or you could use a stereo jack to complete the power circuit when a lead is plugged in, everything else was included with the kit.

[Taffy Evans]

Thanks for that Todd I'm going to look into this too, thanks for sharing.

[ozwood]

My Bad Liam,

Late night post should ban myself , should have read 10 - 20 miliamps , not measured just guessed , but my point is under the right circumstances still potentially lethal.

Cheers,

[kiwigeo]

Electric fences are high voltage but low amperage.....that said I still treat them with respect when I'm climbing over the bastards. I learnt that the hard way while engaged in field work as a geologist in New Zealand many years ago. I watched my mate push down the top wire of the fence with his geologists hammer and nimbly climb over same. I did the same and received a healthy zap to my cods.....I hadnt noticed that that his hammer had a fibreglass handle while my hammer was of all steel construction.

[ozwood]

Hi Martin,

I stand by my claim, there is enough current and volts in what that Guy is doing to easily kill someone , when was the last time you saw an electric fence arc like that, I know it's only Low current , but at that voltage still deadly. I have not got around to measureing the current potential of a 9 V battery , but the average for a new one is claimed to be 90 ma so all those 9v bats in series , the Guy claimed added upto 2000v , so 2000v at 90 ma is more than ample too kill you.

Thanks for the correction Liam , I do understand the difference between series and Parrallel ,(it was a tired typo) I guestimated that the half to flat 9 volter would be around 10 -20 Ma not 10 - 20 amps , turn out it's a bit more . I was not at all suggesting that Hooking them up in series multiplied the current , I was pointing out that a contemptuous attitude towards electricty is always a bad thing , especially when you promote it on Youtube .

Thanks,

[kiwigeo]

Paul, my post not intended too discount you're message. Was just pointing out that even a zap from a low amperage source can be uncomfortable.

[ozwood]

specially on the Goolies Martin, Ouucch , it's all good mate !