adding an OD section to an amp

[TUBEDUDE]

I've done it many times with a 5879 distortion stage after the tone stack. Sounds great. My favorite topology actually, 2 gain stages, cathode follower, tone stack, 5879, cathode follower, split to Eff loop, P.I. 6v6 PP cathode biased.

[ChopSauce]

Thank you very much for the information. If it is not to be held secret: which PI do you use?

NB: I was not aware of the 5879. It does seem to sound really good - from what I could catch from Google videos

[TUBEDUDE]

Schmitt inverter

[ChopSauce]

Thank you very much for the pointer. I'll have to study this (also.)

[Ken Moon]

A simple way to add a gain stage is to use an LND150 instead of a tube. It wouldn't be hard to come up with a small PCB implementing the Dumble OD circuit using LND150s.

Marshall used one in their 1-watt JCM1 amp, and some of the guys at AX84 have experimented a lot with these, and have tips and example circuits.

Just search AX84 for "LND150" - the nice thing about these devices is that they operate at the high B+ levels found in tube amps. They can also be used for reverb recovery and active effects loops, among other things. Googling "LND150 gain stage" will yield some other schemos and posts from the audio tube amp pages.
Here's the basic concept:



more scoop:

http://www.hawestv.com/amp_projects/amp ... _200v1.htm

[xtian]

RG Keen's MOSFT follies is a great page for more on this:

http://www.geofex.com/Article_Folders/m ... tfolly.htm

[dorrisant]

Fine minds think along the same channel... I have been doing a Songwriter type preamp with a switchable ODS style overdrive... into a single fixed bias 6V6. Holy crap it is loud!! I'm totally diggin' it and encourage others to experiment. I have built this preamp into several different amps so far... a few at 10-18 watts p-p, a couple 50 watts p-p (one is a Line 6 Spider (2 x 12")) and several single ended units. Nothing but love from all of the people who have sampled the goods.

[ChopSauce]

This is really tempting, of course, but is a choke definitely required - for optimal filtering - when "inserting an OD section within a "simple" circuit, which usually doesn't need one?

more scoop:

http://www.hawestv.com/amp_projects/amp ... _200v1.htm

As the sample seems to sound, I am rather tempted to follow RG Keen's advice and use only MOSFETs where it is sonically transparent, for example as a "cathode" follower behind a pentode - rather

[M Fowler]

TAG member Henry owner of Redplate contributed many schematics and photos in the early days which are great to follow or get ideas from.

BASS_CONV.GIF

bassman_board.jpg

Hyp_Bass2.jpg

layout_bassman_d_clone_final_186_191_570.pdf

[TUBEDUDE]

Wow, no cathode ground on the power tubes? So the source of the tubes cathode current is..... the other tubes grid cirrcuit??

[ChopSauce]

Thanks! This is something of an answer (which raises even more questions )

[dorrisant]

I am in the middle of a project that involves adding a Dumble style overdrive to a Trainwreck Songwriter amp. This adds a nice switchable overdrive to one of the best sounding clean amps and includes a footswitched relay to go back and fort between the two channels. I am about 90% done with the design work and hope to build the amp before too long...

Attached is the prototype overdrive design...

Beat you to it!!! Lol! Although, it is not 30 watts, more like 11 or so with one fixed-bias 6V6GT. It is packed in there but still the quietest single-ended amp I've built yet.

[RJ Guitars]

Beat you to it!!! Lol! Although, it is not 30 watts, more like 11 or so with one fixed-bias 6V6GT. It is packed in there but still the quietest single-ended amp I've built yet.

I'm cool with that... good to have something else to look at. The guy hasn't come thru with the funds for the project I've got started so I'm holding off until he builds his so maybe we can learn a thing or two from each other.