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1975 Silverface Fender Twin Reverb, AB763 Circuit
Old 27th August 2014
  #31
Gear Guru
 
FFTT's Avatar
 

Jacob, what you have then is a solid workhorse Fender, but with such extensive
work, the re-sale value has been seriously compromised.

I hope you find a buyer who appreciates the amount of work you've put into it.
Old 28th August 2014
  #32
Quote:
Originally Posted by FFTT View Post
I tend to prefer Fender combos with 10's

More focused and if you're running AlNiCos pushed, they absolutely sing!

Pro Reverb, Super Reverb and Vibrolux Reverb are all really close.

Speakers can make a huge difference.

While the VR is more focused, the Super is a wall of sound, but both are only
40 watts.
Pro reverb has 12s.
Old 28th August 2014
  #33
Quote:
Originally Posted by FFTT View Post
Can't remember the output impedance of the Pro, but for recording if the impedance matches, unplug the pro speaker connection and just run a jumper over to the Tweed deluxe to use as an extension cab.
It's 4 ohms, but it'll run fine with anything between 8 and 2.
Old 28th August 2014
  #34
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kafka's Avatar
Quote:
Originally Posted by Jacob Zanin View Post
This is a great sounding amp and it has been carefully built to last a long time.
Well, that's cool if you were able to get a solid amp out of it. I obviously haven't played it or lived with it, so there's no way I can say it's better or worse sounding, or more or less reliable than a Twin (ok, Twins are tanks, so you'd have to do something really special to make it more reliable. )

The problem with trying to get top dollar is that a buyer is going to have to take your word on the work. It's not so much a question of the quality of the work, as it is convincing someone else it's worth it. The best case is it's everything you say it is. The worst case is they get electrocuted.

Anyway, good luck, and I hope your amp ends up in the hands of someone who can appreciate it.
Old 28th August 2014
  #35
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FFTT's Avatar
 

Quote:
Originally Posted by John Eppstein View Post
Pro reverb has 12s.

I didn't say the Pro Reverb had 10's just that I prefer 10"s

Otherwise the three amps are quite similar just different speaker configurations.
Old 28th August 2014
  #36
Quote:
Originally Posted by FFTT View Post
I didn't say the Pro Reverb had 10's just that I prefer 10"s

Otherwise the three amps are quite similar just different speaker configurations.
Not quite. The Super Reverb has a 2 ohm version of the Bassman transformer, which has significantly more iron in the core compared to the transformer shared by the Pro and the Bandmaster. I'm not certain which one the Vibrolux used but my guess it's the one in the Pro.
Old 28th August 2014
  #37
Quote:
Originally Posted by Jacob Zanin View Post
Just found this thread and it is my amp, so I thought I would reply with some more info on it.



It sure looks a hell of a lot better than the original factory lead dress.



The tube sockets were changed from the original plastic ones to nice ceramic sockets. This was because the old ones were loose and would not retension very well. The original eyelet board was black, and yes it's a new board. All of the transformers are original. Believe me, it sounds way better than any TRRI I have ever heard.



This is BS! All the values are the exact same as the AB763 and it sounds like the other BFTR I have played through. Way more mojo than a Reissue, and built better. I buy lots of gear on Craigslist and I despise those who try to deceive others on CL. This is a great sounding amp and it has been carefully built to last a long time.
It looks like you did a fine job on the rebuild but there are really some issues that devalue the amp.

1. The case in that vintage Twin is particle board (MDF), not finger jointed pine. This makes it both heavier and structurally less sound. It also slightly affects the tonality since particle board is not resonant.

2. The transformers are not the same as the real AB763 trannies - the power tranny puts out a higher plate voltage, which increases the clean headroom and power output (to approximately 100 watts rather than the original 88.) The output tranny has more iron in the core, so even with the ultralinear taps desoldered and tied off it's still not going to saturate quite the same as an original blackface.

3. Some of the new parts you used are of a higher quality than the originals. This will make slight differences in tonal quality. Whether this is significant is really up to the player. Some probably won't even notice, some will. In particular replacement of the old molded carbon resistors will make a difference, as well as replacing coupling caps with newer, higher quality ones - the real AB763 used pretty cheap paper couplers and substituting modern plastic types (Mylar, etc.) will change the tone a bit. The reason for this is that the older, cheap parts induced a little subtle distortion into the signal that the newer, higher quality parts don't produce. In most electronic applications this is regarded as a good thing, but guitar amp electronics as ass-backwards in some respects as far as desirability is concerned.

4. The circuit boards have been replaced with ones that are obviously aftermarket. The only sane reason for doing that is if the amp had caught fire at some point (i.e. if a component failed badly enough to burn a hole in the board material.) That may or may not e true but that's what some people are going to think.

At any rate the alterations have removed any possible collector's interest in the amp. The only value it has now is as an amp for the working musician, which means that essentially it's worth about as much as somebody is willing to pay for it, whatever that might be. That's also a function of how long you're willing to wait before it sells.

FWIW I've worked on Fender amps since around '72 and own an original, unaltered amp of the same model yours started as, complete with the optional Fender badged JBL D120Fs. It makes a killer amp for pedal steel just the way it is and that's the use it commonly sees in my studio.
Old 28th August 2014
  #38
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Quote:
Originally Posted by Oldone View Post
The Amp is not a real 1972. It's a rebuild from parts. Here is a real 1972 layout.

fender twin 1972 schematic - Bing Images

The amp is not worth more than $300 for parts.
I'm curious could one really be built for $300? if so where could you get the parts easily?
Old 28th August 2014
  #39
Gear Guru
 
FFTT's Avatar
 

Average price for a standard refurb, parts and labor, runs $250.00 - $325.00 and that's usually
just for caps, filters, any death cap removal, three prong cord, and general checkover and cleaning.

Figure average bench time at $80.00 per hour.

If the preamp tubes were original, they alone would be worth quite a bit of money.

One good AlNiCo speaker can easily run into $200-$300 range these days,

I'm actually a bit surprised Jacob went through all that trouble and didn't go to heavy mil spec Garolite
board.
Old 28th August 2014
  #40
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Quote:
Originally Posted by chainrule View Post
I'm curious could one really be built for $300? if so where could you get the parts easily?
I'm currently looking at a desk full of bits from Ampmaker, Bluebell Audio (for Hammond trannies), and Mouser. Building your own is a cheap way to get your hands on some modern boutique amps or old classics from Fender etc. Either that or get electrocuted, as Kafka said.

A DIY kit with step-by-step instructions is a good way to start.
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