silver face to black face

[billcreller]

 A friend asked me to fix up his silver face twin.  I asked if he wanted it " black faced" How much difference is there between those, tone wise etc?  I haven't ever done that, but figured I could get it done. ( with help from here !!)  He's the guy I sold the Princeton Reverb to, that I built.  He loves it...I didn't !

[HotBluePlates]

I didn't notice much difference in tone in a silverface Twin I blackfaced for a guy.

Most of it was about undoing the silverface layout, making that layout as much like a blackface as possible, removing small caps to ground at the output tube grids (and a couple of other items that were not like the blackface version), and converting the bias balance to a bias adjust.

In the end, it still sounded like a Twin to me. He seemed to like it though.

Blackface Twins also had higher plate voltages, but with today's climbing wall voltage, this particular Twin may end up with a B+ close to the blackface spec.

[smackoj]

Full agreement with senor Hot Blue. The silver to blackface mod is about undoing the theorhetical attempt by Fender amp gurus of the early 70s, late sixties timeframe that were trying to make a war horse into a lost lamb for the general public's consumption. They wanted to use that bias design so people could bias AND use poorly matched tubes to still get good Twin RV output/performance. But, as we hear on a daily basis nowadays from the wizards of smart on the boob tube, there were "unintended consequences".

Those small caps you remove off the power tube grids were put there to tame down oscillations without having to trouble shoot the whole thing looking for lead dress probs. And, the other BIG diff. that CBS did on all the SF amps, was to stop using cloth covered wire and replace it with the colored plastic stuff that doesn't stay where you put it. I had an old amp guy here in Nebraska tell me that he calls those amps wired with that teflon stuff the Fender "Spaghetti" amps cuz they look like italian dinner plate inside.....wires going everwhichaway in a jumbled up wad. So, even after careful chop sticking the guts to find the 'quiet' zone, the wires won't stay where you put them unless you get creative or use diff. wire that stays put.

So, with the caps removed from the output tube sockets, there should be more 'highs' although the freq. range may not even be in the human hearing plot and you will never hear those sounds. Way high up there where the eagles fly most likely.

good luck with the endeavor.   

[drgonzonm]

My two cents, 

Provide a blackface schematic and layout with the date of conversion.  That way some day in future, some good money won't be spent on a tech trying to figure out what happened.  Also attach in an old Bull Duram bag, the parts you removed.  Again, some day, someone might want to change the amp back to silver. 

[Ed_Chambley]

I have done one of these and did not notice much difference except you can bias hotter.  It is not difficult as I remember.  I made a few resistor changes and recapped the amp at the same time.  Still, I ended up with a metallic sound in the upper mids.  After making the changes, the biggest "improvement"  was disconnecting the NFB wire and changing the OT.  The amp sounds really good, but I am selling it.  Too heavy and loud.  Turn it up where it needs to be to have a great tone, I have to use it at outside gigs.  I did notice a major difference when you get to about 6 on the volume.  It will breakup and start giving back whereas before it just got louder.  Great for playing old country music, but the newer country has more grind.

[billcreller]

Thanks for the replies.  Maybe in this case I should just get it working OK.  The cab needs a recover, so that alone may keep the guy happy if the amp works decent.

BILL