diytube.com

http://www.torresengineering.com/index.html
http://www.tedweber.com/
http://www.duncanamps.com/
These websites contain a wealth of parts, kits and information on guitar amps and the like.

Here is a great site for Marshall info and schematics:

http://www.drtube.com/marshall.htm

Is this the schematic you want to use?

http://www.drtube.com/schematics/marshall/1978u.gif

Why did you choose this? Interesting, ultralinear, Fender tried this briefly and dropped it quickly as it didn't sell. The first bass amp I built was UL, but the second one was not. KT88 is a good tube for this, but expensive.

http://www.diytube.com/forumpix/viper_in.jpg

I should submit new pics as I made some changes in transformers and layout since these were taken. When I designed the layout, I made sure there was enough room for KT88s.

I like the 6L6s because they are cheap to buy and common as grass.

Keep us posted,

Don

Just wondering.... shouldn't the two grid resistors for V3 be 270K, and not 270 ohms ?

And at the "intersection" in the cathode of the second half of V2, (phase splitter) should it be a connection and not a "jump" between the 2.7K and 100K resistors ?

The junction between the two 200 uF caps, and of the two 56K, 2W resistors, should be connected. (lower right hand corner of the schematic)

On the bias voltage winding, there should be a connection from ground to a center-tap on that winding.

/ed B in NH

Man have you got sharp eyes or what! I spotted the 270 VS 270K but the other ones I missed. Another reason to design and build from scratch. And hey, since we're talking, why not take out the second half of V2 and make V3 a Schmidt style PI? Personally I would get rid of V2 and the tone controls altogether, but hey that's just me!
The business with the bridge recitifier is kind of interesting, not sure I understand the purpose of all that.

Don

The bit with the bridge rectifier is probably that electrolytics with the proper voltage rationgs were unavailable, or very expensive, back then.

I've used a similar approach in some of my hone builds, just to use parts I already had rather than shelling out the ca$h for HV caps. It's also a handy way to generate two different B+ voltages, say 400V for the power tubes and 200V for the preamp section.

My SWAG about the schematic "errors" is to keep the "copy cats" at bay, but the guitar amp techs could figure out their way through them.

This is typical 60-70s era "value engineering", make it cheap, but still good enough to do the job. In this case, a little extra distortion is a good thing.

But play an FM tuner or CD player through it, and it will sound like someone's swinging an alley cat around by the tail Yellow_Light_Colorz_PDT_09

I've screwed around with enough tube amps since the "dinosaur days" that I can spot these flubs from a mile away, with one eye closed Yellow_Light_Colorz_PDT_06

/ed B in NH

ampman1961 wrote:Hello...
Do yourself a favor and do not use the Marshall power supply as the platform. You do not have to use an Ultra Linear output transformer to get good results.
Billy

I think Ultra Linear transformer will give more power rather than sound quality. Sufficient power supply is good for providing High Power, if you want Hi-Fi and realistic sound, use lower B+ like below 300Vdc, and chose a real HI-Fi tube like 6V6, EL84 or even 6AQ5. These tubes can really give you real sound, of course don't use PP, take SE operation.

I myself, love music, but not the lousily ones, if you compare your equipment with German made like Telefunken, Grundig, or other brands, you will see the difference. Yellow_Light_Colorz_PDT_21 Yellow_Light_Colorz_PDT_21 Yellow_Light_Colorz_PDT_21