Difference between 2 x EL84 and 4 x EL84 board architecture?

[Mike Sulzer]

The same is true for the test power, because the same speaker gives a different subjective picture at different power (2 x EL84 or 4 x EL84)

But the amplifiers must sound very different if they are capable of different power outputs, but played at the same power. Significant nonlinearity is involved in the output stages. Nonlinearity implies big differences at different powers.

[vintagekiki]

Amplifiers must sound very different if they run different loudspeakers because the frequency range, efficiency ... ... are different from the model to the model of the loudspeaker, so the subjective impression is different.

Therefore, when the difference between 2 x EL84 and 4 x EL84 board architecture is discussed, the difference between board architecture 2 x EL84 and 4 x EL84 should be separated.

If there is an amplifier board architecture, a choice of speakers, etc, a free choice of constructors, so there are differences between the amplifiers.

After all, look at board architecture Vox AC4 and board architecture Fender Vibro Champ. As for the sound, the subjective impression is completely diametric.

[vintagekiki]

"Loud thinking"

There is a constant discussion about the difference in sound between Fender BF and SF.

Guitarists, instead of dealing with note arrangements, study the amplifiers schematics, and from servicing technicians seek absolutely irrelevant steps to make BF from their SF.
But the truth is on the other side. Board architecture BF and SF amplifiers are very similar.
The "secret" is only in speakers.

Fender BF amplifiers use Magnet AlNiCo
https://www.tubesandmore.com/products/speaker-jensen-vintage-alnico-10-p10r-25w

Fender SF amplifiers use Magnet Ceramic
https://www.tubesandmore.com/products/speaker-jensen-vintage-ceramic-10-c10r-25w

To break the myth of BF vs SF, try the following.

Set "one by one" BF Fender Super Reverb and SF Fender Super Reverb.
Amplifier set up (volume and tone) in both cases must be as much equal

Connect the amplifier head BF Fender to the SF Fender speakers and try. Your amplifier head BF Fender sounds like SF Fender.

Try the same but vice versa. Connect the amplifier head SF Fender to the BF Fender speakers and try. SF Fender sounds like BF Fender

And for the end
Connect to head SF Fender, then head BF Fender to any speaker box (eg Marshall).
See if there is a more significant difference in sound in both case.
To recall. Amplifier set up (volume and tone), brand tubes in both cases must be as much equal

[bob p]

Fender didn't make any move to compliance with that until the late 70s.

I think the AA769 Twin Reverb did that in 1969.

[Chuck H]

I think the AA769 Twin Reverb did that in 1969.

[ATTACH=CONFIG]44520[/ATTACH]

And no one liked it!?! Loud and clean is what the engineers wanted from that model. Leo was hip enough not to let them make such changes while he was calling the shots. Whether he knew better or not doesn't matter. His considerations were more likely returns, failure rate and return customers. Just because something was not technically "correct" wasn't a reason not to sell the crap out of it. If enough of the old design were failing to offset profits or a dedicated following then I'm sure Leo would have ordered the change. Instead, the engineers chomping at the bit were just waiting for the old guard to fall away so they could make "better" amps. Which, in retrospect didn't sound as good (subjectively speaking based on customer response).

I know this wasn't your point and I'm not calling you on anything. I just used the subject as a jumping point for this factoid.

[pdf64]

I think that the objective for the AA769 may have been to reduce failures, rather than 'louder and cleaner'.
Lower stress on the tubes would lead to a longer operational life and perhaps most importantly, reduce the number of catastrophic tube failures within warranty; note the HT of only 405V and, as noted, the lower g1-k resistances.
I guess that the AB673 TR (460V HT) may have had excessive failures, which it looks like the CBS engineers put down in some part to tube stress.
The lower HT of the post Leo TR would have had a somewhat lower power output; that would have reduced speaker failures too.
Note that the PT has the same 125P34A ref in the AB763 as well as the AA769, despite the HT winding voltage being lower

Those AA769 look to be well designed, with good mitigation for blocking distortion; perhaps corporate financial pressures forced the use of cheaper speakers? I think that's more likely to have got those amps a bad rep, rather than the changes to amp design.

Did Fender start offered premium speaker upgrades (eg EV, JBL) around that time?

[Justin Thomas]

Leo was always after louder & cleaner, but he always listened to his customers first. If he could have found a way to keep the CHARACTER of his amps along with loud and clean, he would have. With Music Man he did just that. I think Leo was ALWAYS about "being cheap," just not to the detriment of the final product - theory would always lose to practical tastes of his customers. When he left, all the "theory" about what sounded good overruled the tastes of musicians without their coñsent.

As far as the earlier and later amps sharing the same transformers, those part numbers are Fender's house numbers. They would have ordered trannies by the hundreds, and if they changed the specs for that house part, they just send the new specs with the next order to Schumacher, who update their order files.

As for "premium speaker upgrade" options, I believe those started in the early 60s with the tan Showmans & Twins.

I like your theory on speakers getting the SF amps a bad rap more than the designs... how many musicians then would have seen a speaker as such a vital part of the final sound?

Justin

[bob p]

And no one liked it!?! Loud and clean is what the engineers wanted from that model. Leo was hip enough not to let them make such changes while he was calling the shots. Whether he knew better or not doesn't matter. His considerations were more likely returns, failure rate and return customers. Just because something was not technically "correct" wasn't a reason not to sell the crap out of it. If enough of the old design were failing to offset profits or a dedicated following then I'm sure Leo would have ordered the change. Instead, the engineers chomping at the bit were just waiting for the old guard to fall away so they could make "better" amps. Which, in retrospect didn't sound as good (subjectively speaking based on customer response).

I don't agree with the opinion that BF = Good and SF = BAD. We can thank the Internet for that nonsense.

I'm also not 100% sure that Leo didn't have a hand in some of the first changes to the big amps. More on that later.

Prior to the age of the Internet we only had to deal with a couple of self-proclaimed amp-guru book-writers (who I don't feel the need to name) who were badmouthing SF amps. Not that many people bought into the nonsense because not that many people had access to their books. As a result the world was perfectly happy with BF and SF Fenders. Those who liked the BF Fenders for their specific attributes bought them (they weren't expensive or hard to find at the time) and most people were happy enough with SF Fenders. Both series of amps were cheap and plentiful and everyone was happy. At that time there weren't that many people doing amp repair and custom builds as a hobby. There wasn't a lot of easy communication back then. At best, we had a dial-up BBS system back then, or maybe Compuserve. The ability for mass dissemination of information by end users was limited. You couldn't download a bootlegged PDF of a book back then, information exchange was slower than it is today, knowledge was considered "esoteric" and it was often guarded.

The world stayed happy with SF Fender amps until the age of the Internet when more people gained exposure to the opinions of the self-proclaimed amp-gurus and those opinions started getting traction. Suddenly there was a wild explosion of people who became interested in amp DIY, there was a limited amount of knowledge out there, and with nowhere else to turn for information a great many people bought into the opinions of the self-proclaimed amp-guru book-writers... and they bought into it hook line and sinker.

Those who didn't know much began to parrot those opinions ad nauseum on web forums so much that they became sticky internet facts. Now everyone believes that BF=GOOD and SF=BAD.

I don't agree that CBS ruined the Twin Reverb, allegedly because they took away the amp's ability to break up and turned it into something loud and clean. It's easy to get an amp to break up -- if you want more break-up, it was easy to downsize your amp. Back in the day some musicians owned several different Fender amps, depending on the size of the venue they needed to play. Life would have been simpler with a stompbox and a big amp that always stayed clean, allowing you to play any sort of venue. But that wasn't how things worked back then.

Loud and clean in a BIG amp is a GOOD thing. 50 years after the SF amps came along we tend to forget how well received those big fenders really were. I might be in the minority on this, but I think that the changes that CBS implemented in the SF amps were a good thing.

Back in the day there were many musicians who complained to Leo Fender that their BF amps weren't loud enough and clean enough. People commonly think of pedal steel guitarists in this regard. The stereotype is that guitarists don't like what CBS did during the SF era. That stereotype completely ignores people like Steve Howe who loves his CBS-era Twin/Dual Showman and has lugged it all over the world with Yes since the 1970s.

The stereotype also ignores that people like Dick Dale, King of the Surf Guitar, who was complaining that his BF/Blonde amps weren't loud enough or clean enough. Back then Dale was using two Showman amps to get loud and clean. Being a local boy who hung with Leo, he complained that his amps weren't loud/clean enough. The story goes that neither Leo nor George could understand what Dale was complaining about until they made a field trip to one of his shows. Once they saw his live act they immediately recognized the problem and fixed it. (I wish I had a link to this story, but I can't seem to find it.)

I'm not 100% convinced that CBS is completely responsible for the first changes to the Twin Reverb / Dual Showman as SF models. I think that Dale got some of those "improvements" directly from Leo and George before CBS took them to production.

OTOH, I am 100% convinced that the sticky internet lore that BF=Good and SF=Bad is responsible for the price appreciation and general unavailability of BF amps on the used market, because they're now all being hoarded by vintage gear hounds.

[bob p]

I guess that I should also mention that I'm old enough to have gigged with SF Fender amps in the 1970s when SF amps were new. In the 70s I could buy a new SF amp at my local music store and I had the choice of both SF or BF amps on the used market. Back then almost everyone who played a Fender wanted the SF amps. Nobody cared about BF amps back then. Nobody regarded them as anything special. They were just used amps.

Things are totally different 50 years later. Now there is an absolutely irrational "mania" for collecting "vintage" gear. People are applying huge premiums to everything that is considered "vintage," and the term "vintage" is being indiscriminately applied to anything that's not recent production. I was at GC the other day and I saw a "vintage" tag hanging on a late 1980s Mexican Strat. It was priced too high.

I think that much of the mania for collecting BF amps is artificially contrived. Many people want BF amps just because they're collectible, and because they've been told that they're "better." As a result the BF amps end up being sequestered from the market by collectors, which makes them more rare, more collectible, more valuable. And to support the rationalizations of the price appreciation, collectors remember them as being far more special than the people who actually gigged with them back in the day. In the 1970s when SF amps were new, nobody cared about BF amps.

[Justin Thomas]

I favor both BF & SF for different reasons. There's a thread here from some time ago addressing SF "pull." It's an irrepressible topic, but I think it's there, and I like it. And I think a loud SF is closer to SRV than a loud BF...

I think another issue to consider is that by the time the SF amps came along, Marshall was becoming a serious contender, especially with the British hard rock invasion & Hendrix. The guys who wanted distortion and breakup in the 70s knew exactly where to get it, and the guys who wanted clean knew where to get that. If you couldn't get a Marshall, a BF or tweed would get you closer than a SF, I bet...

OT: Huh. I wonder why nobody ever suggested smaller coupling caps to Dick Dale for his Showmans...

Justin

[Chuck H]

FWIW I was never expressing my personal feelings on the SF vs. BF matter. It was solely based on customer response at the time that the demographic was growing, but the change in design by Fender to the SF models with significant changes didn't produce the sales that CBS expected and barely matched the BF sales and then began to drop on particular models. Just because it wasn't your world doesn't mean it wasn't happening. And Fender, in fact was VERY aware of it. CBS fumbled for awhile and then sold the company decades later for what they paid!!! Then some employees invested and picked up the pieces to start the reissue thing that got it all going again to put Fender back on the playing field. The freeking internet didn't do that. That happened before the internet had enough influence. And even then, we're talking about musicians and business. Give them what they want is the credo. The SF amps sold because they were good amps and people respected the Fender brand. But experienced musicians did indeed feel the better tones were from the BF amps. So you could say that the LACK of an internet was the reason for the SF amps doing even as well as they did.?. Less information. CBS Fender and the SF amps were absolutely riding on the coattails of the empire Leo built. They were too big to fail the moment they owned the company. Then they failed. I can't put it plainer than that. And, again, I never said there was anything wrong with most SF amps. I said musicians in the know preferred the BF predecessor. And I don't believe that happened because of the internet. That's based on the companies history and the time line.

[vintagekiki]

I don't agree with the opinion that BF = Good and SF = BAD. We can thank the Internet for that nonsense.

I do not agree that we can thank the Internet for various "nonsense" because the Internet is not responsible for the knowledge or knowledge of its users. The Internet is just a medium with information from us.

To get back to the thread.
Can any of the appreciated discourse explain to me the difference in the schematics that is subjectively reflected on the sound between BF and SF.

BF schematics
http://www.thevintagesound.com/ffg/super_reverb_bf.html


SF schematics
http://www.thevintagesound.com/ffg/super_reverb_sf.html

[Justin Thomas]

Try putting up a schematic of the later SFes, too. For the most part, there were only two versions of most BF amps, maybe 3 (Bassman). They only ran for 5 years. The SF line ran for nearly 15.

I'll use the Bassman as an example because I know the iterations by heart...
BF: AA864, AA165, AB165 (ran into the SF line)
SF: AB165, AC568, AA1070 (I think), AA371, Bassman 50 (non MV), Bassman 50 (MV). Then you run into the MV series, then the ultra-linear high-wattage series...

The main difference in the EARLY SF amps was the "mixed bias" arrangement and the addition of the suppression caps. The Bassman started getting really screwy with the AB165, with local negative feedback even before the mixed bias. Negative feedback loops, power supplies, various "pull boosts" etc., PI changes, suppression caps due to sloppy lead dress, construction changes, speaker changes... ever notice most BF amps are a lot lighter than late SF ones?

A lot of the smaller amps never changed except for cab construction and speakers; the larger amps got both circuit and construction changes. And as always, with any amp, it's hard to point to one little tweak and blame the whole reputation on that one tweak, but taken as a whole, the circuits did evolve dramatically enough to change some stuff. So much so that I do indeed believe they can all be made to sound "good" in the hands of the right player, but no, a late-70 s SR will never sound like an AA763.

And for the record, I personally prefer the sound of early- to mid-CBS-era Fenders.

Justin

[vintagekiki]

What you find is the difference between the amplifiers you are calling for it is that only when compare the amplifiers without use any standards.

In order to see the difference between the amplifiers, in the guitar - speaker chain only one component can be changed and all the others must be the same.
In this case it is
- The same guitar
- The same guitar tone combination
- The same amp tone combination
- The same loudspeakers
- The same test power

When compare, I set the controls to the max at the guitar, and set the amp bass and treble controls to max, and the mid control to min.
If the amplifier has two volumes, MV control set to max, and (first) Volume at 30 - 50% power.
Volume value at 30 - 50% power I set up with tone generator to input and voltmeter parallel to speaker.
Only if the standards are as high as the benchmarks become a realistic sound picture

[vintagekiki]

Off topic

To better understand the difference in sound between Fender and Fender, look at the schematics board architecture.

One schematics for Fender 45WRMS (2x6L6) is identical to 3 amplifiers
Super reverb (410), Bandmaster reverb (212), Pro reverb (212)
http://www.thetubestore.com/lib/thetubestore/schematics/Fender/Fender-CBS-45W-Super-Pro-Bandmaster-Reverb-Schematic.pdf

One schematics for Fender 100WRMS (4x6L6) is identical to 5 amplifiers.
Vibrosonic reverb (115), Twin reverb (212) Dual showman reverb (215), Quad reverb (412), Supersix reverb (610)
http://www.thetubestore.com/lib/thetubestore/schematics/Fender/Fender-Twin-Reverb-SF-100-Schematic-Mastervolume-Schematic.pdf

The difference is only in the used sound cabinets (loudspeakers).
To remind that Fender is at the beginning except Jensen built JBL speakers