What's all involved in getting a basic 9 volt Overdrive TS circuit to run on 18 volts ?
Thanks for any help or tips !
Besides getting an 18V DC supply, you need to make sure your components are rated for the higher voltage. Resistors are more than likely fine, but you need to check the caps/IC's/transistors.
What about op amps ??
JRC 4558D , how do they stand up to the 18 volts ?
Yup. It's a common mod, as long as all your other stuff is rated for more than that. I'd be most worried that you could have 16V caps in there, so look closely!
I should be good then , cause i use alot of electrolytic s than are rated at 50 volts :icon_biggrin:
These were the components that i was worried about ???
JRC4558D
2N3904
1N4001
Film caps 1uf , .1 uf , .047 uf , .22 uf etc etc
Could i feed my OD board direct from a charge pump output ??
9 Volt dc > 1044SCPA > dc input on OD board ...
Quote from: HOTTUBES on February 19, 2014, 12:26:03 AM
Could i feed my OD board direct from a charge pump output ??
9 Volt dc > 1044SCPA > dc input on OD board ...
yup..
I wouldn't expect all that much difference in the case of a TS-9/808. Keep in mind that the headroom advantages to increasing the supply voltage pertain to where it is the supply voltage itself that is constraining the headroom of some gain stage. So, if you are asking a gain stage to turn a 100mv signal into a +/-5V signal, running off a 9V supply will put an end to that particular goal, and running off 18V will make it a reality.
But in the case of a Tube Screamer, the diodes are in the feedback loop of the op-amp, such that signal amplitude in that stage can never really go above about +/-650mv or so, and ALL clipping will be diode-related, rather than headroom-related, as it is in something like the MXR Distortion+ or the Proco Rat. Or, said another way, the headroom limitations come from the diodes, not the supply voltage.
If using 18V for a couple of pedals helps to simplify things for you, be my guest. But if you are doing it for this particular pedal, in hopes of hearing something magical, I wouldn't hold my breath if I were you.
All of that said, I second all of the things to look out for that others have noted.
Just check the opamp datasheet.If it can take 18 vols it's fine.That opamp can take 18 volts.Also, as it has been mentioned before, resistors are usually good for these kind of voltages.Just make sure that all your other components such as caps are rated at least 25 volts, just in case.
Thanks Guys for all the great info ...
I see alot of Overdrive pedal makers talking about them being able to run on 9 or 18 volts , many players have said that there is a big difference
with them running on the 18 volts etc etc .... so my question now is , what are they doing in the circuit to make better use of the 18 volts ???
Example Phulltone Fulldrive 2 , its a 9/18 volt OD based around a TS circuit ...
Quote from: HOTTUBES on February 19, 2014, 11:10:45 PM
what are they doing in the circuit to make better use of the 18 volts ???
imagining or lying.
...or their pedals are quite different from the Tube Screamer. Mark's already summed it up better than i could. there are circumstances in which higher voltages can be beneficial (or at least different), namely circuits where signal preservation is the goal, but it's a fact that's abused and turned into hype. as far as i can tell, anyway. it's something i read a lot on non-DIY guitar forums, where people seem to think you can just plug a higher voltage into
anything and it'll magically sound better. ofc, maybe it does... http://en.wikipedia.org/wiki/Placebo (http://en.wikipedia.org/wiki/Placebo).
i guess it's the old "bigger=better" myth (i think i'm average, for the record :icon_lol:).
Quote from: HOTTUBES on February 19, 2014, 11:10:45 PM
Thanks Guys for all the great info ...
I see alot of Overdrive pedal makers talking about them being able to run on 9 or 18 volts , many players have said that there is a big difference
with them running on the 18 volts etc etc .... so my question now is , what are they doing in the circuit to make better use of the 18 volts ???
Example Phulltone Fulldrive 2 , its a 9/18 volt OD based around a TS circuit ...
It's not ALL hype, but one would be naive to ignore the particular design of a circuit, and treat anything that calls itself an "overdrive" as essentially the same thing. In some instances, such as all-discrete JFET-based circuits that do not rely on diodes for clipping, varying the supply voltage can result in different qualities of sound. In others, such as the TS circuit described earlier, other components will govern the performance of the overall circuit more strictly, such that variations in supply voltage will have a very tiny voice in that crowd, by comparison.
Of course, when the objective is to be as clean as possible, raising the supply voltage will go a long way towards maximizing headroom. For example, take your everyday plain vanilla MXR Microamp, goose the supply voltage with a charge pump or even just double 9v batteries, and it can become a much better mic booster for feeding a mixer or whatever. If memory serves, the Visual Sound Truetone clean booster, that RG designed,
triples the supply voltage for huge headroom.
Supply voltage does have an impact on the performance of tubes, naturally, with some tube-based pre-amp/overdrive makers using what often gets described as "starved plate" (i.e., lower than recommended plate voltage) to yield saggy overdrive.
At 18v you'll notice more volume because the pedal has more power.
As Mark noted, if you want a bit more headroom change the clipping diodes for leds.
mac
Quote from: Mark Hammer on February 20, 2014, 09:14:46 AM
In some instances, such as all-discrete JFET-based circuits that do not rely on diodes for clipping, varying the supply voltage can result in different qualities of sound.
For instance, the Catalinbread Formula #5 benefits greatly from 18V. At minimum on the gain control it's too dirty for me at 9V. But at 18V it gives me the perfect range from clean to dirty as I adjust the volume knob on my guitar.
Mac,
You are certainly correct that use of LEDs or even a 2+2 set of 1N4148s would undoubtedly raise the volume ceiling, even without a supply-voltage change, but where would the increased power/volume come from, in a stock build? The stock clipping diodes have a fixed forward voltage, the tone stage has very little gain, and the transistor buffer stages are ostensibly run at unity gain. If the transistor stages changed their gain via the supply voltage, I could see it, but nothing that would be amenable to supply variation is jumping out at me. So what am I overlooking? (and I have overlooked MANY things before :icon_redface: )
Mark, I took a look at the output transistor, and its emiter voltage would be higher, ie, more power to deliver to whatever follows the TS.
In other words, I thought available electrons not voltage.
mac
That might make a difference if you were connecting it to something with a very low input impedance. I wouldn't think anything you'd normally connect it to would be drawing any significant current though so it wouldn't make any difference.
EDIT: scratch that increasing the supply voltage is only increasing the DC power, not the AC, I think???
At 9 Volts, with a hot enough signal it is technically possible to make the opamps in a TS clip, you're probably talking a lot hotter than a guitar though unless you've got some stupidly loud active jobby.
So the general consensus is that in a slightly modified TS overdrive circuit , running at 18 volts will not held a very big difference over its standard 9 volts ?? hmmm ??? Interesting ....
Ya never know until you try! There are dirt pedals, such as the Fulltone OCD, that do sound different at higher voltage.
QuoteSo the general consensus is that in a slightly modified TS overdrive circuit , running at 18 volts will not held a very big difference over its standard 9 volts ?? hmmm Huh Interesting ....
I have a Red Fuzz which is a cousin of the TS, and a Dist+. At 18v they have more of everything.
It's not a 100% jump because diodes do limit the voltage, but they are working harder and adding extra harmonics.
mac
Well, diodes do behave a little differently, depending on the current presented to them. Perhaps they behave a little bit differently with a higher supply voltage applied to the op-amp pushing them?
It's one of those things that really cries out for a blind test. Personally, I don't expect anything particularly noticeable, but distortions are an especially nuanced thing where very small differences can appeal to, or discourage, different players. Of course, those "little things" can be a real and reproducable phenomenon, or they can just as easily be a quirk of a particular unit and the listening biases of the player.
QuoteWell, diodes do behave a little differently, depending on the current presented to them. Perhaps they behave a little bit differently with a higher supply voltage applied to the op-amp pushing them?
That's what I think.
Imagine a 1k resistor in series with a led at 9v. It's going to give some light. Now double the voltage keeping the 1k resistor. There is more current, more light and extra voltage drop.
For simplicity take a Dist+. At 18v the opamp and the 1u tant cap are feeding the diodes with extra current because like in the example above, the opamp and the cap can go higher. They make the diodes work harder, which means more harmonics, ie, more signal and more volume. It's not much because that extra diode voltage drop is small, but it is noticeable.
mac
Quote from: garfo on February 19, 2014, 11:20:46 AM
Just check the opamp datasheet.If it can take 18 vols it's fine.That opamp can take 18 volts.
If the max supply voltage for the op-amp is 18V, and you are feeding it 18V, isn't there a danger either that a mild surge in power could fry the IC, or that the IC is not bang-on spec and can only take 17.5V so this also fries it?
Quote from: GGBB on February 21, 2014, 05:38:26 PM
If the max supply voltage for the op-amp is 18V, and you are feeding it 18V, isn't there a danger either that a mild surge in power could fry the IC, or that the IC is not bang-on spec and can only take 17.5V so this also fries it?
A max supply voltage of 18V means +/-18V, so it can handle 36V total. So it's not a problem.
When i do up another run of overdrives , i'm going to " beef up " the caps , and try one at 18 volts .... i have heard so many guys rave about how much " better" they sound running on 18 v v/s 9 v. For some reason i could see players who use there overdrive to push a dirty amp enjoying the new found 18 volt head room etc .
Thanks for everyone's input !!
;D :icon_smile: :icon_wink:
I ran a LTSpice simulation of a Distortion+ at 9v and 18v. Input signal is 0.5v @ 440hz.
First second is the output wave at 9v, then at 18v.
The volume change is "similar" to what I hear in the real life.
LTSpice shows a difference of 15% using 1n5817.
Even increasing the ouput resistor to >1M the difference remains the same.
sound sample (http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=50563&g2_GALLERYSID=61097b6ae70d4311ec5581cb08b3aba7)
mac