Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: hesamadman on May 27, 2015, 08:54:39 pm

Title: Looking for info on diode clipping
Post by: hesamadman on May 27, 2015, 08:54:39 pm

Been playing with some diode clipping in a couple of my amps. Ive seen a lot of videos of people doing it and using a double throw switch which gives two different values of clipping. Well, I am getting some neat tones but my problem is loss of volume. I lose way too much. Any idea how to remedy this?

Title: Re: Looking for info on diode clipping
Post by: PRR on May 27, 2015, 10:50:00 pm

Add gain after clipping.

Title: Re: Looking for info on diode clipping
Post by: TIMBO on May 28, 2015, 12:47:20 am

This is how the JTM60 does it.

Title: Re: Looking for info on diode clipping
Post by: VMS on May 28, 2015, 07:03:19 am

You can put few diodes in series so that Vt voltage increases from 0,7V to 1,4V or 2,1V and so on.

Or you can use zener diodes.

Title: Re: Looking for info on diode clipping
Post by: hesamadman on May 29, 2015, 07:08:21 am

Quote from: VMS on May 28, 2015, 07:03:19 am

You can put few diodes in series so that Vt voltage increases from 0,7V to 1,4V or 2,1V and so on.

Or you can use zener diodes.

I was hoping to do this without adding a tube. But if not possible I just wont mess with it on this amp. But can you explain your method of the two diodes in series? Where do I put those in the circuit? Im pretty sure I used zener diodes on the mod but I can double check as I just had them clipped in.


Right now the diodes are installed to ground with the drop down resistor right before the grid of V2a of my 2204. Two diodes. One down flowing. One up flowing.

Title: Re: Looking for info on diode clipping
Post by: 2deaf on May 29, 2015, 06:33:59 pm

Zeners give a sharp clip with a harsh sound.  If you want to try them, hook two in series either pointing towards each other or pointing away from each other.

A lot of the time when people use multiple regular diodes (e.g. IN4007) in series, they will use more in one direction than in the other.  This more closely imitates preamp tube clipping.

For more fun, try using a resistor and a diode for the cathode of a preamp tube.

One strategy is to get some amount of distortion from the tubes and then clip with the diodes.  See the Marshall 2210 schematic which straightens out to three diodes up and three diodes down.  Or look at my attachment which is a variation of the same idea.   

Title: Re: Looking for info on diode clipping
Post by: VMS on May 29, 2015, 06:47:26 pm

Here is some examples:

diodes in series to increase headroom:

http://www.diystompboxes.com/cnews/mods.html (http://www.diystompboxes.com/cnews/mods.html)

Full-wave zener diode clipping:

http://www.electronics-tutorials.ws/diode/diode-clipping-circuits.html (http://www.electronics-tutorials.ws/diode/diode-clipping-circuits.html)

DIY amp with clipping option:

http://www.tube-town.net/cms/?DIY/Amps/TT-SAM_MKII_%28engl%29 (http://www.tube-town.net/cms/?DIY/Amps/TT-SAM_MKII_%28engl%29)

ceriatone chupacabra schematic:

http://forum.metroamp.com/viewtopic.php?f=3&t=34858&start=105#p416455 (http://forum.metroamp.com/viewtopic.php?f=3&t=34858&start=105#p416455)

Title: Re: Looking for info on diode clipping
Post by: Fresh_Start on May 30, 2015, 08:17:36 am

Thanks VMS. Helpful links.

Chip