GREAT HIGH GAIN TUBE PEDAL/PREAMP!!

[frickecello]

I found this schematic its from a crazy dutch guy called Louise Goedhoop, If you have been searching for a really good sounding valve pedal and you know how to work with valves then this is for you, it needs 3 valves, (ecc81, ecc82 and ecc83). The circuit topology is familiar but it has been fine tuned to get rid of nasty excessive fuzzy distortion to get a more focused tight distortion, bass response is great and is an excellent valve preamp too!!

I used this valves to build mine:

Sovtek 12AX7LPS
Mullard ECC81
Haltron ECC82

Its really quiet, however shielded wire on sensitive places is recommended.

Take a look:

http://www.paginasprodigy.com/guitardoc/nicegirlharddriver.wmf

[puretube]

what does that little red line on the very top of the schemo say? - oooh, my eyes... 

[frickecello]

Caution! Valves are not replaceable do not install a different valve without adequate bias adjustment.

[John Lyons]

Looks interesting. The input starts with a low gain high current tube and the tubes get higher gain as they get toward the end.
Is there any other information on this. Soundclps etc?

John

[puretube]

ahh, thanks, fricke! 

[JimRayden]

Looks interesting. The input starts with a low gain high current tube and the tubes get higher gain as they get toward the end.
Is there any other information on this. Soundclps etc?

Funny, I'd do it the other way around so the softer clipping low gain tubes stay at the end of the circuit and start distorting first... Or am I missing something here...

---------
Jimbo

[bancika]

Looks interesting. I've got all tubes needed for it but unfortunately don't have much time for it. I've scheduled kalamazoo amp and hi-gain amp based on XTC or Rectifier to build next...

[MartyMart]

Anyone know how I can open this file on a mac ??
Tried :
OSX Preview
Windows media player
Photoshop 7
Adobe Acrobat 7

...... I'm running out of programs here !!

MM.

[JonFrum]

Five gain stages - Criiminy! Lead dress would be very fussy in that build - it's a noise machine.

The Tweed Bassman and Deluxe have a 12AY7 in the first hole, and it contributes to the characteristic sound, so lower gain can be good in the early stages. As a general principle, you want the highest possible gain at the input to keep the noise floor down. That's why pentodes have been used as imput tubes.

[John Lyons]

Marty

I just emailed it to you. Not my schem but I was interested as well. Had to "printscreen" a few times and then paste together in  photoshop.
Ah windows...!

John

[MKB]

Might be hard finding a 12AU7 and 12AT7 with low noise and microphonics to use in such a beast, especially a 12AU7.  Those aren't used very often in high gain circuitry, and perhaps microphonic suppression wasn't high on the design list like in a 12AX7 or 12AY7.

[frickecello]

Looks interesting. The input starts with a low gain high current tube and the tubes get higher gain as they get toward the end.
Is there any other information on this. Soundclps etc?

John

This preamp is part of an hybrid 250 watt guitar amplifier, that Goedhoop and me (Marcelo Fricke) designed and built for an university project, it features a 7 band active opamp eq before the preamp (which features actual musical octaves as resonant frequencies) an active opamp crossover and separate L-mosfet power amplifiers for treble and bass which drive a tweeter and a woofer. We wanted a more modern sound, thats why we chose SS for the power amp.

I have recorded some short clips but I cant upload them here, I can send you a short clip to your mail.

We are designing a digital reverb/delay stage, and thinking about a crazy idea we had about adding a second woofer controlled by a mechanism that sends signal to one or other depending on sound (like an auto pan) and also rotate the speakers (like a 3D effect) we are studying robotics so we need to focus more on robots XD

Five gain stages - Criiminy! Lead dress would be very fussy in that build - it's a noise machine.

You should see the SLO and the 5150 first if 5 gain stages are too much for you XD

You can tweak it to your personal taste, tone is very subjective...

Have fun...

These were the valves we used to build it:

Sovtek 12AX7LPS
Haltron NOS ECC82
Mullard ECC81

Goedhoop & Fricke

[brett]

Hi
the microphonics issues of 12AT7s and 12AU7s can be helped a lot by not hanging them upside down behind the speaker.  Putting valves behind speakers is one of the dumbest ideas that any combo amp designer ever had.  I love to play loud and two of my favourite combo amps have valves behind the speakers, so I've rattled many tubes to bits, including those with a reputation for low microphony such as 12AX7s and EL34s.
As many people know, there are some very cool high-gain pre-amps in Marshalls that only use 2 x 12AX7s.  They are often very quiet and very sweet. 
The Real McTube uses a single 12AX7 in high-gain mode (plate resistors of 680k and 330k IIRC) for some really wild tones.
cheers

[JonFrum]

I know the SLO very well, thank you very much. I think the design is a particularly bad one for anyone without a good deal of experience building guitar amps. It may sound great, but people reading this thread should know that it would be a difficult build for anyone who hasn't debugged high-gain preamps in the past. And that's just assuming it's going to be used in an amplifier. In pedal form, it would be even more difficul to get it rightt.

[Ardric]

I don't think that heater power supply will work as drawn.  There's no way a 220 ohm R26 can pass enough current for 3 tubes at 6VDC.  You could drop your current requirements in half if you simply wired the tubes for 12V.

Huge bright caps, huge grid blocking resistors, lots of grid bypass caps and a big 3n lowpass on the end.  Conventional wisdom suggests that will get you dark-sounding and hissy at the same time.

[brett]

Hi
looking at the schematic in more detail I notice a couple of minor point that you might consider:
an LM7806 is shown for regulating DC for the heaters.  With 3 heaters to run, the 7806 will be near its current limit and over its power limit unless it in stalled on a large heatsink.
Also, the grid resistors at the input indicate a grid-to-ground resistance of 1.5M.  It might be better to use a much smaller grid stopper (e.g. 68k) and a smaller grounding resistor (470k to 680k).  I've never been a fan of a grid stopper (ie they can be left out), but some people suggest that you pick up radio interference without them, so it probbably doesn't hurt to have one.
Don't take these suggestions too seriously coz I'm certainly not an expert.
thanks for sharing this cool design.

[petemoore]

  I opted for separate amp cabinet, special 'mushy' feet, made from...yupp bicycle inner tube. Nice and mushier than feet I could find, glued in 1/2'' staples hold in 2 'U' folds...works great, probably extends tube life/reduces microphonics.
  I like my cabs kind of resonant.

[frickecello]

I know the SLO very well, thank you very much. I think the design is a particularly bad one for anyone without a good deal of experience building guitar amps. It may sound great, but people reading this thread should know that it would be a difficult build for anyone who hasn't debugged high-gain preamps in the past. And that's just assuming it's going to be used in an amplifier. In pedal form, it would be even more difficul to get it rightt.

Sorry, we cant post a DIY guide, we just share the design if someone finds it helpful, gets some ideas or may give it a try...

I don't think that heater power supply will work as drawn.  There's no way a 220 ohm R26 can pass enough current for 3 tubes at 6VDC.  You could drop your current requirements in half if you simply wired the tubes for 12V.
Huge bright caps, huge grid blocking resistors, lots of grid bypass caps and a big 3n lowpass on the end.  Conventional wisdom suggests that will get you dark-sounding and hissy at the same time.

Relax...
You are right, that resistor has nothing to do there, and yes a 12V DC supply would be ideal, however most valve power trannies have a 6.3V secondary instead of a 12.6V. Tone is very subjective... what you may consider good tone can be for others crappy tone. Thats what we considered good and worked for our personal tastes, conventional wisdom was surpassed by engineering knowledge long before you were born.

These are the files with corrected heater supply issue and LTSpice simulation if anyone wants to tweak (try other valves, other cap/resistor values, etc) test and hear it before building it: (even try your own designs)

http://www.paginasprodigy.com/guitardoc/nicegirlharddriver.wmf
http://www.paginasprodigy.com/guitardoc/nicegirlharddriver.asc

nicegirlharddriver.asc file contains instructions to simulate your own sound clips with the NGHD preamp, you can use those commands to simulate your circuits. (if link is broken I can send it to your email address)

Get LTSpice completely free at:

http://www.linear.com

CALM DOWN PEOPLE!!! you are not forced to build this thing  so RELAX! 

How many DIYers are needed to change a lightbulb?
R: 8, one to change it and 7 that consider they would have done it better and faster. 

Best regards.

G & F

[frickecello]

Sorry people, the link is broken...

Follow this link to download the LTSpice NGHD circuit simulation file, after downloading change the file extension to .asc and open it with LTSpice, be sure to read the instructions contained in the file.

http://www.paginasprodigy.com/guitardoc/nicegirlharddriver.jpg

[frickecello]

Instead of clicking it, right click and select save as...