Tube boost + overdrive running off a 9 volt battery

[Mustachio]

Siroky, Could maybe be a bad tube or something in your circuit is bridged or maybe a stuck pot value. take pics and look at the debug thread.

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0


Also all of these valvecaster variants work better at 12v's for the heaters and higher for the rest of the circuit.

If your running off a 9volt battery it will eat the battery fast and once its drained to a certain point it just wont have enough amps for the heaters which is something around 400ma.

Also For toplak whats the amps rating on your power supply ? If you don't supply enough current with these tubes they hum, just gonna guess that 2 tubes and the rest of the circuit and any voltage regulators are gonna be hungry for amps and I would suggest something over 1 amp maybe 2 amps would work best .

If you read back a few pages in this thread there's a lot of info about hum and different causes when using switching mode power supplies and voltage regulators. There's also grounding issues to look at and is it inside an enclosure for shielding.

Good luck guys and welcome to the forum

Also reading this entire thread is good for you, think of it as a right of passage ! Can really learn a lot from such a wonderfully large thread with lots of great info threads like these don't come along every day.

[toplak666]

Thanks for your help mustachio. My trafo is rated at arround 1,1A. I've measured the amp draw with the trafo and the batteries and with both I got a consistant 0.33A so I doubt amperage is a problem... If I had a higher rated power supply handy I would try it but I don't think I have one at the moment... I'll try to find the part about the hum you mentioned. I already skimmed through all the pages... Guess I must have missed that part. :S
In the mean time, any more advice? It seems filtering is the main issue. Any advanced filtering circuits I don't know of?

[Jdansti]

Welcome!

Good info from Jim.

In your earlier thread, you said two things that caught my attention:

1) works great on 3- 9V batteries
2) power supply = transformer to regulators with filtering on both sides of the regulators.

You've probably got enough filtering on the power supply, but you didn't mention a rectifier. Do you have one between the transformer and regulators to convert AC to DC, or is the transformer output ready rectified?

[toplak666]

Welcome!

Good info from Jim.

In your earlier thread, you said two things that caught my attention:

1) works great on 3- 9V batteries
2) power supply = transformer to regulators with filtering on both sides of the regulators.

You've probably got enough filtering on the power supply, but you didn't mention a rectifier. Do you have one between the transformer and regulators to convert AC to DC, or is the transformer output ready rectified?

Indeed I do have a rectifier. I'll have some pictures and maybe a schematic up by the end of the day.

Thanks for the help!

[Bill Mountain]

It's been a while since I checked in here.

Did we break any new ground recently?

I'm thinking of doing some starved plate CLEAN preamp designs.

Is anyone using their Valvecaster for cleans?

[Isak]

hello,

i found this http://www.diystompboxes.com/smfforum/index.php?topic=77190.0
didnt build it yet.

hope this helps in some way.

cheers.

[toplak666]

It's done! 2 months of R&D and a week of soldering and it's done!



Isn't it pretty?  

___________________________________________________________________________________________________________________________________________________________

Ok, let's start at the beginning!
Transformer and rectifier:



1.) .68µ/250V capacitor infront of the transformator to smooth out the AC just a bit.
2.) 24V/1.1A transformator bought from a local electronics store. Don't let the writing on it fool you... It is 24V/1.1A.
3.) Just your average everyday full wave bridge rectifier.
4.) Huge-ass inductor of unknown value that i found in an old ATX power supply. Actually helps quite a bit with smoothing out the rectified DC...
5.) Wires going to main board.

___________________________________________________________________________________________________________________________________________________________

Main board:



1.) DC input connector.
2.) sh*t-ton of filtering. 10n, 100n, 10µ, 470µ and 4 1000µ capacitors. This may look like overkill but I assure you, each one of these makes a contribution to lessening the hum. Adding more filtering doesn't help, however removing them results in more hum.
3.) 2 10000µ capacitors that make by far the biggest difference in smoothing out the current. (As if the other capacitors weren't overkill enough... xD)
4.) 12V regulator, 18V regulator and an awesome heat sink from the ATX power supply mentioned earlier.
5.) 2 1000µ capacitors for filtering after the 12V regulator.
6.) 2 1000µ capacitors for filtering after the 18V regulator.
7.) Stage 1 valvecaster circuit with connectors for off-board components.
8.) Stage 2 valvecaster circuit with connectors for off-board components.
9.) LM317 regulator set to 9V (because i didn't have a fixed 9V regulator handy) for Tillman preamp and indicator LEDs
10.) 2 1000µ capacitors for filtering after the 9V regulator.
11.) Tillman preamp circuit.

___________________________________________________________________________________________________________________________________________________________

Off-board components:



1.) Volume and gain POTs for first stage.
2.) Volume and gain POTs for second stage.
3.) Indicator LEDs, foot switches and connectors.

___________________________________________________________________________________________________________________________________________________________

Crème de la crème:



2 GrooveTube 12AX7s bought at a local music store for 18€ each.

___________________________________________________________________________________________________________________________________________________________

The end result is a heavenly sounding Doublecaster with next to no hum. If there's one thing I learned from this build is that more capacitors = less hum. Nothing new right? Indeed. However I never imagined I'll be using 10 1000µ and 2 10000µ capacitors to eliminate the hum... And yet that's what it took! Now i have next to no hum even when cranking both the gain pots to 9! (The sound I get with both on 10 isn't that good but maybe I'll fix that one day...)
Next step: Building an epic enclosure with the help of a friend!

If anyone needs help with 12AX7 valvecasters or with removing hum feel free to ask. I feel pretty confident that i'll be able to help at least a bit.

Couldn't have done it without the help of everyone on this forum! So thanks again!

P.S. Wow, this is one huge post! xD

[Isak]

Beautiful work, well done!

[Govmnt_Lacky]

HOLY HEATSINKS BATMAN!!!

Great looking build! 

[Jdansti]

Everything looks beautiful!

I could be wrong (it happens, ask my wife ), but I suspect that the transformer might really be rated at 18V secondary with 230V input, and you saw 24V because it was measured without a load. If the transformer output is less than 19.5V under load, your 18V regulator may not have the proper input voltage to operate correctly. I'm interested to know the following::

1) Transformer input voltage,
2) Transformer output voltage, measured with no load, e.g., disconnected from all other circuitry (this may not be possible if it's hard wired),
3) Transformer output voltage, measured with load (the output of your regulators need to have a load for this measurement), and
4) The output voltage of each regulator, measured under load.

It all may turn out fine, but I'm a skeptic by profession.


Edited for grammar. 

[toplak666]

Everything looks beautiful!

I could be wrong (it happens, ask my wife ), but I suspect that the transformer might really be rated as having an 18V secondary at 230V input, and you're saw 24V because it was measured without a load. If the transformer output is less than 19.5V under load, your 18V regulator may not have the proper input voltage to operate correctly. I'm interested to know what the following:

1) Transformer input voltage,
2) Transformer output voltage, measured with no load, e.g., disconnected from all other circuitry (this may not be possible if it's hard wired),
3) Transformer output voltage, measured with load (the output of your regulators need to have a load for this measurement), and
4) The output voltage of each regulator, measured under load.

It all may turn out fine, but I'm a skeptic by profession.

On it!

[toplak666]

Whoa... Am i ever glad you were sceptical. O_O

Input voltage is 220V.
The transformer actually only gives me 19V without any load...
And falls to only 15.5V with full load!
...In my defense, when I wrote "It is 24V/1.1A." I was measuring with all the filtering already connected but no load so that's what bumped my measurements up...
Now, I knew that the trafo alone gives me 19V and the capacitors bump that up to 24V, however I just assumed that the voltage wouldn't drop by that significant of an amount under load. (facepalm...)
That's also the reason why I simply wrote the trafo is rated at 24V...

Looks like I'll be getting a new higher rated trafo in the near future! 

Thanks for pointing this out to me man!

[Jdansti]

No problem!

BTW, I don't know if you have a surplus shop near you, but I found some old, but new in box, 24V doorbell transformers for $1 each at my local surplus shop. Old laptop supplies can usually be filtered and regulated too.

[backinnam]

This is my first post, so be gentle with your terminology. I've built a valvecaster and combined it with a Lovepedal COT 50 boost, but now I'm looking for something a bit more intriguing.

Could I build an AC30 top boost preamp and substitute the 12AX7's for AU7's, running it off of 9 volts? 

[Supakas]

Hellou,
Anyone have a schematic, if i want to use 6n2p tubes?

[Riffraff]

I just finished my first and I LOVE THIS THING! I'm hooked, I need to build more variations.
Here it is. I was too excited to paint the box first.   



Clips:

Volume 5, Tone 5, Gain 5

http://www.youtube.com/watch?v=iPNvE5oUk98

Volume 5, Tone 5, Gain 8

http://www.youtube.com/watch?v=L_0vt802HYo

[zaubertuba]

Epic thread, guys!

I've been looking to put together a dual preamp to add some tube overdrive/boost to my NS/Stick.  I happened on Tesaling's Valvecaster 2.0 (http://www.instructables.com/id/The-Valve-Caster-20-Tube-Boost-and-Overdrive/), which seems like a nice fit for the guitar side, and there's plenty of tips here for "cleaning up" the boost of a single-tube Valvecaster which seems like it would work well for the bass side.

I already have a cadre of AMB's alpha20's built up that can be used for output (and if necessary, input) buffering, and a lovely-clean bipolar PSU: http://www.twistedpearaudio.com/power/lcdps.aspx.

My question is - while really clean, the current output on the LCPDS is not that great.  The Alpha 20's ideally need about 100mA each (allowing for headroom).  I've heard a range of current requirements for the valvecaster on this thread anywhere from 150mA to 400mA.  Should I just look at adding a separate power supply for the tube parts of the circuits or could the LCPDS yet be made to work?

Looking to stick patch the guitar side into the preamp loop of my MPX-G2.   

[valve999]

Wanted to relay my thanks to the writers of this thread - I've just built my first effects circuit (a Valvemaster) and I think it sounds pretty good for about £10 of parts plus some scavenging! Not mounted it in its enclosure yet - might upload a photo when I do...

A question to all - why are commercially produced valve pedals not more popular? The Vox Cooltrons (low voltage starved plate like our own beloved Matsumi boxes and variants) are discontinued, as are the Electro Harmonix Hot tubes pedals. You can get them from Blackstar at more than I paid for my amp (and indeed amp and guitar put together!) - but they aren't exactly all over the place, are they? Seems strange, given the fun I'm having with mine! Be interested in your comments...

[Thecomedian]

Beavis what program do u use for drawing those schems up?

[backinnam]

Can I decrease plate voltage by lowering the values of r2 and r3 on the standard schematic? Or do the plates already get the full 9 volts?
If that wouldn't work I can just build a charge pump.