18V Booster - Charge Pump Question

[jammybstard]

I'm looking to build some sort of JFet Booster to drive my amps first valve.
I'd like a pure valve tone so I want clean boost with lots of head room, I'm thinking 18v Booster from a 9V supply Via a Charge pump!

As it seems to be tried and tested around here I was going to use an ICL7660SCPA voltage converter to make as common 9v supply into +/-9v and then tap across the + and - supplies to get 18v.
Fine stand alone! But thinking about it; If I'm now using the -9v as a pseudo Gnd and then I daisy-chain the supply onto another pedal (a regular 9v pedal) and then connect the two together with an interconnect, I would end up effectively shorting Gnd to -9v back through the interconnect! So that ideas out for starts

So what's the most common IC to use to double voltage without creating a negative voltageand doesn't put HF noise on the supply?

[merlinb]

There is a more sneaky way to get roughly double the headroom from a 9V circuit. And it doesn't waste power either:
http://www.diystompboxes.com/smfforum/index.php?topic=91629.0

[Processaurus]

LM1054 is what I use for voltage doubling, there is on board regulation as well, so you could boost the pedal supply to 18v and regulate it down to 15v, if you wanted it to be compatible with noisy power supplies.  That and unregulated doubling are in National's app notes in the datasheet, very simple.

[jammybstard]

Cheers Proc'

Far too clever Merlin!

[jammybstard]

LM1054 is what I use for voltage doubling

Is that number right Proc? I cant find an LM1054

[frequencycentral]

LT1054: http://oh3tr.ele.tut.fi/~ftp/pa/cly10amp1/lt1054.pdf

[merlinb]

Far too clever Merlin!

One opamp, three transistors (or two if you used true bypass)... not exactly the space shuttle in terms of complexity!

[Processaurus]

LT1054: http://oh3tr.ele.tut.fi/~ftp/pa/cly10amp1/lt1054.pdf

Mos def:  LT1054.  Texas Instruments, not National.  Thanks.

[jammybstard]

LT1054: http://oh3tr.ele.tut.fi/~ftp/pa/cly10amp1/lt1054.pdf

Mos def:  LT1054.  Texas Instruments, not National.  Thanks.

Cheers, These seem either hard-to-find or overpriced in the UK! What do you pay for them where you are?

[Dimitree]

LM1054 is what I use for voltage doubling, there is on board regulation as well, so you could boost the pedal supply to 18v and regulate it down to 15v, if you wanted it to be compatible with noisy power supplies.  That and unregulated doubling are in National's app notes in the datasheet, very simple.

I use LT1054 too, but I don't understand how to regulate it, for example, to 15V. Any help? thanks

[jammybstard]

Tried this tonight:


seems to work great; So started work on the Booster

[Processaurus]

LM1054 is what I use for voltage doubling, there is on board regulation as well, so you could boost the pedal supply to 18v and regulate it down to 15v, if you wanted it to be compatible with noisy power supplies.  That and unregulated doubling are in National's app notes in the datasheet, very simple.

I use LT1054 too, but I don't understand how to regulate it, for example, to 15V. Any help? thanks

Page 15, figure 20 in the datasheet I linked to has the circuit and equation to determine R2, you'd just put in 15v for V_out in their equation (the second one with V_ref replaced with 1.21v and R1 being 20K)

[Dimitree]

thanks,
and how can I regulate to -15, for example? the figure shows a VOUT and not a -VOUT like figure 19 (the VOUT is in modulus so I guess it will give -VOUT btw?)

[Galego]

thanks,
and how can I regulate to -15, for example? the figure shows a VOUT and not a -VOUT like figure 19 (the VOUT is in modulus so I guess it will give -VOUT btw?)

To have +18/-18V, you need two cascaded ICL7660S, the schematic can be found in the datasheet. You can also look at the datasheet for the MAX1044. Make sure you get the 7660S and always connect pins 1 and 8 together, it boosts the frequency.

[frequencycentral]

^^^

You don't need two ICL7660S, you can do it with just one.

http://www.geofex.com/circuits/+9_to_-9.htm
http://www.geofex.com/circuits/+9_to_33.htm

...getting higher voltage (and lower -ve voltage) is just a matter of adding more caps and diodes.

...or you can use a NE555: http://analogguru.an.ohost.de/001/schematics/Analogguru_SymmVoltMultiplier.gif

[polaris26]

Another idea to play with - if you have a low voltage/low impedance source (say 1k output impedance) feeding into a much higher impedance (say 100k or higher) input, you can get a fairly decent voltage boost by using a small audio transformer.  A 2:1 voltage (turns) ratio would yield a 4:1 impedance ratio, so if you have, say, a 1k output impedance, you would still have only a 4k output impedance which would be more than adequately low to feed into most guitar amp inputs.  A 3:1 turns ratio would yield a 9k output impedance and triple the output voltage, etc.  The frequency response may be limited in some noticable way, but it might also sound good, so you could salvage a small transformer and give it a try.  You might even get away with a small AC power transformer?



Dave

[Dimitree]

thanks,
and how can I regulate to -15, for example? the figure shows a VOUT and not a -VOUT like figure 19 (the VOUT is in modulus so I guess it will give -VOUT btw?)

To have +18/-18V, you need two cascaded ICL7660S, the schematic can be found in the datasheet. You can also look at the datasheet for the MAX1044. Make sure you get the 7660S and always connect pins 1 and 8 together, it boosts the frequency.

thanks but my question was about regulating the output voltage. I usually use charge pumps to get +18/-18 with no problems, but this time I need a regulated -15V, but figure 19 shows a positive regulation if I'm not wrong.

[Processaurus]

thanks,
and how can I regulate to -15, for example? the figure shows a VOUT and not a -VOUT like figure 19 (the VOUT is in modulus so I guess it will give -VOUT btw?)

To have +18/-18V, you need two cascaded ICL7660S, the schematic can be found in the datasheet. You can also look at the datasheet for the MAX1044. Make sure you get the 7660S and always connect pins 1 and 8 together, it boosts the frequency.

thanks but my question was about regulating the output voltage. I usually use charge pumps to get +18/-18 with no problems, but this time I need a regulated -15V, but figure 19 shows a positive regulation if I'm not wrong.

On page 17 there is a:
Figure 23. 100-mA Regulating Negative Doubler

[merlinb]

Considering the input headroom of your valve amp will be only about 4Vp-p max, one might ask why you need +-18V...

[PRR]

> a pure valve tone so I want clean boost with lots of head room

Back in the days of valves, Leo raised B+ voltages from 200V to 350V or 400V for more headroom.

IMHO, 9V 18V +/-18V(??) on tubes is just fooling yourself. Even the cheepest battery tube radios got 22V, any serious battery tube radio had 45V 67V or 90V supply. And these were not amazing-clean machines, but batteries were EXPENSIVE.

As Merlin says, your OUTput is presumably going into a guitar amp, with input overload of just a few volts. On that grounds, you could try lower voltage, even 10V, so the clipped output is in a right ballpark. However your tube has gain, surely 1:10 or 1:30, so now your tube's input overloads VERY easy, and hisses.