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Post subject: Re: Transformer Inductance vs Bass in old BF/SF Amps
Posted: Sat Feb 20, 2016 11:53 pm
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According to ampwares.com:

http://ampwares.com/amplifiers/fender-silverface-quad-reverb/

The Quad Reverb is 31½ x 26½ x 11½ and weighs 89½ lbs - 100 or 135 watts.

http://ampwares.com/amplifiers/fender-super-six-reverb/

The Super Six Reverb is 40½ x 26½ x 11½ and weighs 98 lbs - 100 or 135 watts.

Jerry

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Post subject: Re: Transformer Inductance vs Bass in old BF/SF Amps
Posted: Sun Feb 21, 2016 3:08 am
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jmallard wrote:
According to ampwares.com:

http://ampwares.com/amplifiers/fender-silverface-quad-reverb/

The Quad Reverb is 31½ x 26½ x 11½ and weighs 89½ lbs - 100 or 135 watts.

http://ampwares.com/amplifiers/fender-super-six-reverb/

The Super Six Reverb is 40½ x 26½ x 11½ and weighs 98 lbs - 100 or 135 watts.

Jerry


Indeed!

Both of those monstrosities qualify as the world's first "crew-served" combo amps.

:lol:

Arjay

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Post subject: Re: Transformer Inductance vs Bass in old BF/SF Amps
Posted: Sun Feb 21, 2016 9:25 am
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It is a beast. But the owner is young and strong. He likes the fanfare effect of the four speakers over his Twin so he's stoked with the sound.
The two amps are only 66 serial numbers apart. Yet the Quad at XX069 has a standard OT primary and the Twin a S# XX135 has the Ultralinear OT.
Does these numbers bracket the introduction of the ultralinear OT or did they mix up the production?


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Post subject: Re: Transformer Inductance vs Bass in old BF/SF Amps
Posted: Sun Feb 21, 2016 11:43 am
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I believe the 100-watt chassis was discontinued when the ultra-linear model was introduced in 1978. I bought a new Twin Reverb in February of that year and was surprised to see the output jack marked "135 WATTS RMS". I still have that amp though it sees little use now.

Arjay

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Post subject: Re: Transformer Inductance vs Bass in old BF/SF Amps
Posted: Sat Aug 27, 2016 7:34 pm
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Reviving this post 8 months later.
Previously, I posted the differences between SF and BF amps. Recently, I had a few different BF Super Reverbs come across my bench. They has different output transformer measurements. They were all 125A9A but had different inductance, resistance, and lamination thickness. The performance graphs also showed up significant differences.
Now I’m no expert at the dating or production series, so what I’m looking at needs interpretation and corroboration from more experienced hands. So I’m just here to present the data.
All transformers listed have the same physical dimensions


Serial number A08725
OT# 125A9A
EIA# 606-418 424 is stamped in white over the 418
STAMP# 018343
Blu-Brn resistance 115 ohms
Blu-brn inductance 12.25 Henries
Lamination .0125"
2KHz peak 1.11Vrms


Serial number A0786
OT# 125A9A
EIA# 606-438
STAMP#
Blu-Brn resistance 91 ohms
Blu-brn inductance 5.06 Henries
Lamination .02"
2KHz peak


Serial number A25090
OT# 125A9A
EIA# 606-719
STAMP# 022855
Blu-Brn resistance 97 ohms
Blu-brn inductance 6.6 Henries
Lamination .0185"
2KHz peak .56Vrms


Serial number CR254103 reissue
OT#
EIA# 606-MS2-10
STAMP# A036485
Blu-Brn resistance 96 ohms
Blu-brn inductance 6.88 Henries
Lamination
2KHz peak 1..08Vrms


The first unit listed, 08725, is the one I have presently. It intrigued me because it has a much higher inductance than the other versions. I can’t rule out that the OT was changed. Some of the solder was not factory. It looks period with the same amount of rust as the PT.
Also, it is a Multitap transformer. The extra wires bundles in a plastic zip tie. Is this period correct?
Another odd aspect is when I measure inductance across the primaries BLU-BRN, I get 12.25Henries. When I measure Blu-Red or Brn-Red, I get zero inductance. On all other transformers I have measured, I get ½ the total by measuring to the red wire. I really don’t understand how it could be configured to get this measurement or why someone would try to accomplish it..
If this is an original transformer, it might indicate that CBS was fiddling with transformer design before it was generally recognized.
The easiest visible difference is in the lamination thickness and stacking. Two thin leaves stacked together or lamination under .018” might be signs of changes. I do not have pre CBS data yet for the BRSR. Here’s the pics.
[img}http://i1083.photobucket.com/albums/j399/Darlene_Breeden/Mobile%20Uploads/Bf%20cbs%20sr%20front_zps5apvueaw.jpg{/img}
[img}http://i1083.photobucket.com/albums/j399/Darlene_Breeden/Mobile%20Uploads/20160824_054107_zpsp0ydfdre.jpg[/img]
[img]http://i1083.photobucket.com/albums/j399/Darlene_Breeden/Mobile%20Uploads/20160824_054140_zpsxbbufdhd.jpg[//img]
Image
Image
Image
Image
Image
Image
Image

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Post subject: Re: Transformer Inductance vs Bass in old BF/SF Amps
Posted: Sat Aug 27, 2016 9:19 pm
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TimsAudio wrote:
The first unit listed, 08725, is the one I have presently. It intrigued me because it has a much higher inductance than the other versions. I can’t rule out that the OT was changed. Some of the solder was not factory. It looks period with the same amount of rust as the PT.
Also, it is a Multitap transformer. The extra wires bundles in a plastic zip tie. Is this period correct?


I know of no Super Reverb ever made with a multi-tap O/T. Thus, I'm doubtful that it's original to the amp. But what's remarkable is the P/N. That's formatted from the old FEIC inventory, ie: pre-CBS. Hazarding a WAG, I'm going to surmise that it's a re-wind using an original core.

Ignoring for the moment that first specimen, all of the other O/T's (whether FEIC, FMI/CBS, or the re-issue) are relatively similar in performance spec's. I would take the mean average of those measurements and use them as a datum point for the blackface (late '63 through mid '67) Super Reverb tranny. I cap the timeline there because I know for fact that silverface editions of some amp models began shipping from Fullerton as early as April but in the case of the Super Reverb, I don't think those started showing up at dealers until July (I personally owned a silverface SR that was built in August of that year).

Good job of collecting and correlating data!

Arjay

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Post subject: Re: Transformer Inductance vs Bass in old BF/SF Amps
Posted: Sat Sep 03, 2016 10:09 am
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I had my suspicions that it wasn't original because of the multitap. Your suggestion that it is a one-off piques my imagination. Why would a factory pull it for modification? Who was it modified for? Who modified it?
I've had a run of Supers come through this summer. Another early silverface is going out the door next week that has 4.88H inductance. I agree these are all variations within one model except the multitap.

I am still on the lookout for CBS changes though. I ran across a CBS deluxe reverb that I wanted to measure inductance of the OT. I thought my new meter was broken when it wouln't measure the primary or even half of it to the red wire.
After measuring the higher than normal resistance, I surmised that it is over the 20 Henry capacity of my meter. This seems uncharacteristic of other early Fenders. It could also be explained by nickel-steel laminations which would give it very high inductance over the stock silicon-steel.
So while I have my suspicions about the OT, I can't document them and I have no baseline BFDR data yet for comparison. I was lucky to have so many Supers to compare.

Overall, though, I've found the higher inductance in an output transformer gives a better efficiency to energy transfer. You get more power out of the same amplifier.
But for guitar amplifiers, builders started with and reissue amps continue to buils with low inductance OT designs. The early bass saturation is the most prominent feature of this design. This enables the midrange component to be the focus of transformer efficiency. And that is where guitar music resides.


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Post subject: Re: Transformer Inductance vs Bass in old BF/SF Amps
Posted: Sat Sep 03, 2016 1:18 pm
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TimsAudio wrote:
The early bass saturation is the most prominent feature of this design. This enables the midrange component to be the focus of transformer efficiency. And that is where guitar music resides.


Maybe that's why my Spankmaster Reverb conversions sound so damn ballsy. One is FMI, the other is FMIC. Both are equipped with a 15-inch JBLs. The amp chassis delivers smooth fat mids and the D130 speakers enhance the overall frequency response by providing a throaty bottom end and bright, crispy highs.

Arjay

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Post subject: Re: Transformer Inductance vs Bass in old BF/SF Amps
Posted: Sun Sep 04, 2016 9:08 am
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I've had the good fortune to hear those JBLs roar. The 4 inch voice coils get a grip on the cone like nothing else
Now, not being a picker myself, the sentiment I pick up is that they are great for clean country, jazz and blues, but don't break up for rock.
What is your take there, Am I advising these guys right?


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Post subject: Re: Transformer Inductance vs Bass in old BF/SF Amps
Posted: Sun Sep 04, 2016 9:29 am
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TimsAudio wrote:
I've had the good fortune to hear those JBLs roar. The 4 inch voice coils get a grip on the cone like nothing else
Now, not being a picker myself, the sentiment I pick up is that they are great for clean country, jazz and blues, but don't break up for rock.
What is your take there, Am I advising these guys right?


To an extent, yes. JBL's do not "break up" as with speakers of conventional construction. The shallow cone does not resonate as with say, a rare-earth Jensen or an Eminence or a Celestion. As well, it's difficult to saturate an 11½ lb magnet structure regardless of signal compression or the presence of near square-wave input. OTOH, if the player is relying on the amp's innate ability to distort and create harmonics (whether alone or by augmenting the input signal via stompboxes), the JBL is a superb instrument. And the efficiency of the design, ie: the SPL, maximizes every available watt that the amp is capable of producing.

Duane Allman (when performing live with "the brothers") played a Les Paul through a Marshall stack, just as Jimmy Page during the heyday of Led Zeppelin. But their respective tones could never be mistaken for one another's. The difference? Duane preferred JBL D120F's while Jimmy liked the Celestion V30's (or sometimes the greenbacks). Thus it can be inferred that the JBL is neither "better" nor "worse" for a given genre of music. But an experienced player who's acquainted with its capabilities can wring some beautiful sounds from it.

Arjay

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