Blonde bandmaster tone caps

[Redwood Bridge]

My first post! ...exciting ... My question is along the lines of "but that's not what the schematic says..." My amp is a 61 blonde Bandmaster (single 12 with tone ring) and the tone caps are .047uF, but the 6G7-a schematic calls for 0.02uF. The caps are blue Molded like the rest of the caps on the board so I suspect they are original. I have had the amp since 71 so not likely changed. I finally got around to trying a new 0.022uF in the normal channel, not expecting a big difference but it changes things significantly...that channel now seems much more complex and thicker....more bassman/Marshall/Traynor sounding. I love having the two different voicings. So...assuming they were original, I am curious as to whether they were often .047s at this point in time or whether mine was just fitted with what they had on hand.

[pompeiisneaks]

Welcome! I'm going to move this to the Fender channel as some of the Fender guru's may not read it in Technical Discussion.

I don't know the answer myself, but hope they get to you soon!

~Phil

[Stevem]

Since your comments are in reference to the .047 uf ( .05 uf on the schematic) you are talking about the plate decoupling caps, not the tone caps which are generally referred to as being in the tone stack.

Yes, both the normal and vibrato channel used those .047 uf caps pass the audio only ( not the D.C. Plate voltage ) on down stream to the next gain stage, and they will effect how much low end gets passed on to that next gain stage.

Those blue cap sounded pretty good for there price point back when these amps where made, but yes when compared to modern caps the blue ones do lack clarity!

You can change these to the uf value that most suites your playing needs, but as in any amp the value you may likethe sound of best will be different at different volume levels, and using lesser values will help the amp to break up latter and not far out in the low end at these high volume levels

Myself I like running smaller value caps like .022 uf especially on the plates of the PI tube.

I find all of my 17 tube amps sound best when at my average playing volume the tonestack controls are close to being 75% wide open, and this means reducing bass output by means of these preamp and PI section coupling caps.

[Redwood Bridge]

Hi. Thanks for the reply...I was refering to the tone cap..on the 6g7-a schematic the tone stack shows a .02uF attached to the bass pot but my amp came with .047s. The later version of the Bandmaster (AA763) uses .047s . The plate decoupling cap is .047, as you said.

[Stevem]

Well your amp has a presence control that the blackface Bandmasters do not, and this can have a effect how low ( frequency wise) and how tight the bass responce can be in regards to using a bassyer .047 uf cap there.
Try one out there and see if you like it better overall , you wil electronically harm nothing by doing so!