Fender Twin Question

[Telewanger]

I purchased a Fender Twin Reverb from ebay a couple of years ago. It sounds great. The previous owner said that it has been Blackfaced, but I would like to know what has really been done to the amp.

I would appreciate it if you could look at the photos and info, and tell me if it has really been Blackfaced or not!

I have added some sound samples of the amp!

Here is the link: www.atlanticplumbing.net/fendertwin.html (http://www.atlanticplumbing.net/fendertwin.html)

[John Phillips]

Yes, it appears that it has, and to a very high standard of workmanship and parts quality.

The only thing that doesn't look right is that the screen resistors (the whitish ones on the power tube sockets) appear to be 100-ohm (brown/black/brown bands), which is the wrong value - they should be 470-ohm (yellow/purple/brown). But they may be 1000 ohm (brown/black/red) if the color hasn't come out clearly in the pics, which is fine, although not stock.

The reason the Hum Balance control is missing is because the BF circuit doesn't have one; it uses the two fixed resistors that you can see on the lampholder. But since there is no disadvantage to having the control (it doesn't affect the tone at all, and can sometimes be useful), it was pointless to remove it.

The amp was made in 1976 BTW, since it has the J-clips for the chassis securing bolts, rather than them passing right through the chassis with nuts underneath - this came in around 1975. This is consistent with the power and reverb transformer and choke codes (620 = 20th week of 1976, 549 = 49th week of 1975, 632 = 32nd week of 1976, and there should be an equivalent 606 code on the OT); if it was later than 1976 it would have started as a 135W model, which have no choke, and some other parts (Output Tubes Matching control, Line Output jack, and a terminal strip along the end of the chassis) which were never fitted to that chassis; so it is a 1976. The speakers look like 1966s though - Fender were certainly not using Jensens in the 70s, and I'm not even sure they were still in production.

Hope that helps, and welcome to TGP :).

[jjasilli]

It's hard to tell just from photo's. Looks like the signal caps were replaced with orange drops; ceramic caps mostly replaced with silver mica. Olld electrolytic caps are replaced with quality caps. Substantially rewired - very neat and professional looking job. The wires are different colors than fender uses, nicely twisted and tied. Carbon comp resistors where they "should" be; quality power resistors elsewhere. I'm sure the amp sounds as good as it looks!

[Telewanger]

I appreciate all of your information! Is it okay for me to call this a Blackfaced Twin?? ( or maybe "Wife Of Frankenstein" )

I have no idea how old the tubes are right now, so I think that I will buy some new ones. I can hear a slight glass bell chime or ringing sound coming from the back sometimes, like something vibrating in one of the tubes.

What are the best tubes for this amp. ( Brand Name ) I want it to sound as original or Blackface as possible?

I paid $900.00 for this amp. I looked for a real Blackface Twin for about a year, all over the internet. Every time I saw one in nice condition, it was about $1,500.00 - $3,000.00. Even some of the real beat up looking Twins are going for $1500.00.

Some people say that the price was too high, but I have it now, and I don't plan to ever sell it. I have made some recordings with it and I am really happy with the performance.

For many years I was a Les Paul / Marshall Man and played in Blues, Hard Rock, and Progressive Rock bands.

Several years ago I started listening more to Jerry Reed, Brent Mason, Danny Gatton, Jerry Donahue, Scotty Anderson, Johnny Hiland, Roy Clark, Albert Lee, etc. Now when I pick up my guitar, I usually want to learn more of their tunes. I don't play much distortion guitar anymore. For years, distortion and a bunch of effects just covered up all of my mistakes. Now with a Tele and a Twin, it is not forgiving. If you make a mistake, everyone knows!

[s2amps]

Whoever worked on this amp was clearly a stickler. Your electrolytics are fairly recent Sprague Atoms, which are (IMHO) the best. The ceramic caps have been replaced with silver mica, which is an upgrade. The other coupling caps appear to be some variant of orange drops. Fender started using these in the late 70's, but many amps still had the blue poly caps or a combination of both. I haven't seen many silver amps with all orange drops. I can't say if those have been replaced or not, but I'm leaning toward yes. The metal film resistors are certainly not stock. The amp was made with carbon composition, but the resistors that have been replaced (although probably not necessary) are the ones that don't matter in terms of tone.

It looks to me like you have a nice amp there. If it makes you feel better, think of how much it would cost to buy a similar hand-made amp from a booteek builder today (like me).

I think you've done well.

[John Phillips]

I have no idea how old the tubes are right now, so I think that I will buy some new ones. I can hear a slight glass bell chime or ringing sound coming from the back sometimes, like something vibrating in one of the tubes.

What are the best tubes for this amp. ( Brand Name ) I want it to sound as original or Blackface as possible?It's hard to be sure from the pics, but it looks like your power tubes are two cleartop GEs and possibly two Sylvanias. A matched set would probably be better, but there's no actual reason it's bad like that if the tubes have been checked and are all roughly similar. If so, don't change them unless they die or you have equivalent quality replacements - 'new' is not the same thing! At the very least, don't throw out the old ones even if you do buy new.

Those old-production tubes have never been equalled for quality or tone, and likely never will be - even in well-worn condition, they still sound better than new-production ones.

The same goes for the preamp tubes - if it has old-production US-made ones, keep them in there until they go bad (microphonic, hum, or weak tone) - don't believe the 'change tubes every few years' myth. I've worked on dozens of amps from the 70s and even some from the 60s with their original tubes in, working perfectly - preamps especially can last decades.

For the ultimate BF tone you really want RCAs throughout, with Blackplate power tubes, but they are very expensive and you will get very nearly equal results with other less expensive old-production US tubes, especially GEs.

I paid $900.00 for this amp. I looked for a real Blackface Twin for about a year, all over the internet. Every time I saw one in nice condition, it was about $1,500.00 - $3,000.00. Even some of the real beat up looking Twins are going for $1500.00.

Some people say that the price was too high, but I have it now, and I don't plan to ever sell it. I have made some recordings with it and I am really happy with the performance.That's an absolute bargain for an amp of that performance and quality. The rebuild work alone is probably worth at least half the price, and the amp will now be good for another twenty or more years before it even needs maintenance, apart from possibly the odd tube.

[AL30]

Wow !!!! That's some clean work. Whoever did that did a very nice job. Check out the heater wires. :AOK


AL

[epluribus]

Color me tuned in. I could stand to learn the right ways to put stuff together.

:munch

--Ray

[Swarty]

Very nice work, but why would someone replace all the tone/coupling caps? Soldering practice? The blue blob (Paktron?) caps that are stock seem to be very robust?

[John Phillips]

Some techs believe that all caps need replacing periodically, not just electrolytics.

IMO they're wong, but it's not actually detrimental - IMO it does change the tone a bit, but just to 'different', not 'bad' - and at least that one has been done to a high standard.

In fact, the one thing that concerns me is something that hasn't been changed - the bias supply limiting resistor is still a carbon-comp. If that fails, goodbye power tubes. The diode could also be changed for maximum safety, although that type are not failure-prone in my experience.

[Wakarusa]

A couple of curious bits --
I notice that one of the PI plate loads is replaced with a metal film while the other is either original or a replacement carbon comp (I'm betting original). Nothing wrong per se, just curious.

The other part is the bias circuit -- I agree with John that the feed resistor before the diode should be something a bit more robust, but both it and the tail resistor after the pot are odd values (120 ohm and 15K ohm respectively if I'm readin' my stripes right). Wouldn't hurt to check the power tube bias and range of adjustment to confirm the changes are correct.

One last note for those intending to blackface a silverface Fender -- some of the later power transformers produced a higher bias voltage than the blackface PTs, so you can run into trouble if you change everything to blackface specs. I.e. the 470/27K blackface bias voltage divider may not give the correct adjustment range.

[Telewanger]

Well,

It looks like this amp is real "Mutt". I don't know who did the work, but I still love it anyway.

It's like the Johnny Cash song. " 51, 52, 53, 54, 55, 56, 57, 58, 59, automobile!"

I will still get some new tubes soon. I have never heard it with new tubes, so I don't know what I am missing, or not!

I just added some songs that were recorded with the amp to give an idea of the tone.

Check them out:

http://www.atlanticplumbing.net/fendertwin.html

[Telewanger]

I appreciate all of the feedback and information on the amp. I would feel better knowing that there are new tubes in the Twin. I will save the old tubes, of course!

I want it to sound as close to a 1965 Blackface Twin as possible within reason. I can't really spend $600.00 on tubes right now. I was told to use 4 Black Plate 6L6's, 2 each 12AT7, 1 each 12AX7A, and 3 each 7025.
Every company says their tubes are the best.

Philips, Svetlana, Ruby, TAD, Groove, GE, Sovtek, and on and on!

What do you think? :crazy

[Chris Scott]

Just a few points:

For that amp of yours to pass muster from the likes of John, Tim and Todd, you're looking pretty good to go IMHO. And as hard as I looked, I couldn't find any glaring (or even not-so glaring) errors- whoever did the work obviously knew what they were doing, and cared enough about the job to make it visually presentable as well-probably done by a reputable tech who's also a total gear slut.:drool

...and to those that say you paid too much, just ask 'em to go out and find the same amp done to anything close to the same level of professionalism for that price (or even TWICE the price)- that'll shut 'em up.

ENJOY!!:BEER

[JJGross]

Another little trick lots of guys with Twins do (like me) to warm them up at a little less that brick shattering volume is to pull either the two inner or two outer power tubes and just run it with 2 instead of the whole rack of four. You can then run it a little hotter on the controls and get a little more meat out of it while still managing a usable volume. As long as you pull them in pairs like that, it causes no harm to the amp.

* Just don't do that if you also run another cabinet with it. Pulling two power tubes cuts not only output power, but impedance in half and adding more speakers cuts output impedance again. That'll beat up or kill your transformers, probably the most expensive parts of your amp. It's fine with the speakers in the cabinet. After all, why use another cabinet if you're trying to warm it up with less volume? Want loud? Get another cabinet and use all 4 power tubes. It's a TWIN! WHAT?! I SAID .... ;D

Cheers,
- JJ

BTW, love the neat wiring in there!

[John Phillips]

Another little trick lots of guys with Twins do (like me) to warm them up at a little less that brick shattering volume is to pull either the two inner or two outer power tubes and just run it with 2 instead of the whole rack of four. You can then run it a little hotter on the controls and get a little more meat out of it while still managing a usable volume. As long as you pull them in pairs like that, it causes no harm to the amp.

* Just don't do that if you also run another cabinet with it. Pulling two power tubes cuts not only output power, but impedance in half and adding more speakers cuts output impedance again. That'll beat up or kill your transformers, probably the most expensive parts of your amp. It's fine with the speakers in the cabinet.No, it won't do any harm to the transformer. Even though the transformer is less efficient with the mismatch, half the power is being produced overall and so even though a greater proportion of it is ending up in the OT, it's still less than that at normal full-power operation. Mismatching downwards like that is very hard on the remaining two tubes, but that's all.

You can fix the impedance mismatch easily, anyway - especially if you're running an extension cabinet. Rewire the speakers to series (easy if they still have the original push-connectors), which gives 16 ohms, then add the extension cabinet (assuming 8 or 16 ohms) which gives either 5.33 or 8 ohms, and is a good match for two power tubes.

[Wakarusa]

Philips, Svetlana, Ruby, TAD, Groove, GE, Sovtek, and on and on!

What do you think? :crazy

For my $$ the closest you'll get to blackplate RCA in a current production tube is the short bottle TAD. They're actually made by Shuguang in China so are available from vendors other than TAD (often for fewer $$).

For current production tubes, my personal favorite in this amp is the S-logo Svetlana (i.e. from Mike Matthews' Russian production). While they sound crystal clear with excellent headroom, they can also be microphonic in a combo. Note too that I'm in the minority with this one -- most folks seem to go for the C logo Svets. Of course they're wrong... ;)

If (eventually) money is no object, a quad of JAN/Philips 7581A in there is pretty much magic.

[slider313]

I happen to like the new Tung Sol 6L6 STR's in my Fender amps. They seem to have a nice tight envelope with clarity and a smooth top end. My '64 Vibrolux never sounded better and has taken on a more "woody" tone.