Dual Showman Low Volume

Rick McDuffie · Post by **Rick McDuffie** » 20 Feb 2003 7:07 pm

I have a '68 Dual Showman and I'm not sure it's putting out all the volume it's capable of. I can open it all the way up to 10 (I'm playing through an 8 ohm 2X12 cabinet) and it's still pretty clean and comfortably loud at 8 or 9. HOWEVER, I would think it should be screaming and at the pain threshold at 9 or 10. This has me wondering if it's putting out all it's capable of. I've just done a complete retube of it. My tech has worked on it (the power and audio output transformers were fried when I got it, so we replaced them with Mojo parts)and he says it's right... but he's not a guitar player and doesn't have a world of experience w/ high-powered Fender tube amps. I don't have another Showman to compare it to. Can anyone offer any wisdom on this? I just want to be sure it's operating at peak efficiency. It sounds great- clean and PLENTY of low end. Help??

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Rick McDuffie
Debbie Elam Band
www.tarheelmusic.com

Tony Prior · Post by **Tony Prior** » 20 Feb 2003 7:45 pm

Rick, an amp such as a Fender Showman, well actually all Tube amps, especially Fender , should have the transformers replaced with exact replacements and re-tubed with exact or better replacement tubes.

You can open up the amp if you have not already and check the transformers # to see if they are correct.

If the power transformer is putting out less HI Voltage for the output tubes than required..that equals low volume.

IF the output transformer is not matched to the output tubes...yes..low output again..

Transformers are not like playing horsehoes..close doesn't count.

I think your assesment may be correct. The Showman should be pretty much shaking the nails loose in the rafters at volume 8 or 9... I can relate to my former Twins..basically the same power amps..I don't recall ever playing it at 8 or 9..geeze
4 or 5 , sometimes a tad around 6 was probably the most I ever attempted at a gig before they were screaming at me with offensive language..

It may be worth bringing the amp to another experienced Fender amp tech in your area to have it checked out as well.

good luck

tp[This message was edited by Tony Prior on 20 February 2003 at 07:50 PM.]

Donny Hinson · Post by **Donny Hinson** » 20 Feb 2003 7:52 pm

A good tech has a wattmeter, and can check to see how much it's actually putting out. There is a possiblility that, though the subbed transformers will function, they aren't a perfect match. This would result in a loss of some power. Of course, so could about 40 other things!

This amp should easily put out 60-80 usable (clean) watts. How loud that is (or sounds) depends on myriad factors, not the least of which is how you have the tone controls set. The reason players sometimes need 200 or 300 watts is not because the amp needs all this power, but because the player needs this much total power to put out what is required (desired) at a specific frequency.

Example: Try this with your amp...

Set the bass, middle and treble all at "2", and the volume at "10". Notice how loud it is?

Now...set the bass, middle, and treble at "10", and the volume at "3". (Can't stand it now, can you?)

The moral is...high frequencies require a mere fraction of the power that low frequencies require to sound "loud" to us.

Ken Fox · Post by **Ken Fox** » 20 Feb 2003 8:03 pm

A 1968 Dual Showman with reverb should see a 4 ohm total load, not 8 ohms. That will lower your power a bit. If both channels are equal or close to equal in volume, the culprit could be a weak 12AT7 driver tube (tube prior to the power tubes as you look at them fromt he rear of the amp). Tube #3 is a 12AT7 (reverb drive). Pull it out and sub it in that position to see if there is a difference in volume. Weak power tubes and improper bias could be a problem. Mojotone tranformers are very good, if he picked the right one. Tube layout should be as follows:

V1 12AX7/7025 channel 1 preamp
V2 same channel 2 preamp
V3 12AT7 reverb drive
V4 12AX7 reverb recovery and channel 2 final mix/preamp stage
V5 12AX7 tremolo oscillator
V6 12AT7 inverter/driver
V7-V10 6L6GC power tubes

Hope that helps a bit.

Ken Fox · Post by **Ken Fox** » 20 Feb 2003 8:08 pm

Donny reminded me of something else. The tone controls on a Fender amp are really volume controls at selected bandwidths! Turn the tones all to "0" and you will have no gain at all! As he also stated, it could be a lot of other things. It will take an experienced tech to get to the bottom if tubes and correct impedance match do not seem to help. Also, how efficient are the speakers. JBL's and Black Widows, for example, are a lot louder that a Jensen with the same input power applied.

Rick McDuffie · Post by **Rick McDuffie** » 20 Feb 2003 8:37 pm

Thanks, Ken. I was hoping you'd weigh in, as I've read your posts in the past and you seem to know your stuff. I've been wondering whether 4 ohm vs. 8 ohm impedance question would make a big difference or not.. sounds like it will. I'm aware of how the "tone" controls impact volume, and consequently have had them opened up pretty much all the way. Also (I play six-string electric through this amp) I'm using a Japan Telecaster with relatively low-output pickups, as opposed to a more efficient pickup. This could be playing a part. This is a sealed-back, late model Fender cabinet, and I honestly don't know what's in there... I assume Eminence. Definitely not BW's or JBL's. The amp sounds so GOOD that it's hard to believe it's not working properly. Thanks also to Tony and Donny for the good input. The Forum is such a great resource! I'll hook it up to a 4 ohm load (which would probably increase the wattage by at least 50%, right?) and see what happens. Thanks, guys!

Rick McDuffie · Post by **Rick McDuffie** » 20 Feb 2003 8:38 pm

Ken, this is a non-reverb amp.

Ken Fox · Post by **Ken Fox** » 21 Feb 2003 6:28 am

Rick, I re-checked that. For your amp, it is still a 4 ohm total. Just make sure you are also using a good speaker (not guitar cable) to the extension cab. Sounds like a good cabinet, should be plenty loud. Your tube layout should be more like this: You could temporarily substitute V1 fro V4 (gain is 100 as opposed to 70 for a 12AT7).

V1 12AX7/7025 channel 1 preamp
V2 same channel 2 preamp
V3 12AX7 tremolo oscillator
V4 12AT7 inverter/driver
V5-V8 6L6GC power tubes

Rick McDuffie · Post by **Rick McDuffie** » 21 Feb 2003 10:37 am

Ken and fellas, I put a 4-ohm load on the head, replaced the 16 ga. cable w/ a 12 ga. and I can tell a considerable difference. Let me try it awhile and I'll back to you. I have confidence that the transformers are the right ones. Thanks very much.

Jody Carver · Post by **Jody Carver** » 25 Feb 2003 6:47 pm

Schumacher manufactured all of Fenders transformers over the years.He is located in
Illinois.

The replacements sold after market are not the same even though they work.

That Dual Showman should tear the walls down. Re check your output and power transformers.

Tony Prior said it all....

Ricky0ne1 · Post by **Ricky0ne1** » 25 Feb 2003 9:26 pm

I don't know about you guys, but when I think about a Fender Showman on 10 I start to tremble.

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Rick Summers

Jody Carver · Post by **Jody Carver** » 26 Feb 2003 8:16 am

Ricky
And have the fillings in your teeth if any checked before
listening.

[This message was edited by Jody Carver on 26 February 2003 at 10:04 AM.]

Jim Florence · Post by **Jim Florence** » 26 Feb 2003 1:24 pm

This sounds like a crock, but I'm from the "Old School". On a tube type amp, you can get a reasonably good test on the output power [admittedly the impedance match is horrible] but a 60 watt amp will light a 60 watt light bulb up pretty good, and you don't have to make a bunch of noise. On a Showman the average ear is not going to be able to tell the difference in output between a 4 ohm load and an 8 . Unscientific,
yes but it works. Try it.
Jim

Rick McDuffie · Post by **Rick McDuffie** » 26 Feb 2003 1:49 pm

Thanks, bro. That's interesting, and I sure would have never thought of it. Are you saying my ear is average? : )

My Fender Stage 100 goes to 160 watts at 4 ohms, and I assure you I can hear the difference.

But seriously, all this input helps. Thanks a bunch!

P.S. You guys remember that since the Twin and Dual Showman were built, things like the Mesa Boogie and the Peavey Ranger (that I use) have been developed. The Ranger is a 120 watt all-tube amp, and it'll damage your hearing if you're not careful. My store sells Peavey AND Fender, and we sell things like the Peavey XXX and 5150 which are capable of some serious volume and SPL's. My Nashville 1000 has a 300-watt digital power amp in it. Even though I well remember when the Dual Showman was just about the biggest, baddest thing there was, that's been a long time ago. It's 40-year-old technology and and just isn't in the same category (volume-wise) as more modern all-tube, high-gain amps. (I know I may be opening Pandora's box with a statement like that.)

Our band plays a lot of outdoor festival/fair gigs and I HAVE to have something that is capable of major league volume when needed. I guess what I'm saying is that, after listening to and playing through some of these REALLY LOUD amps for the past few years, my idea of how loud a Showman should be may be a bit skewed. But compared to the 15-watt Silvertone I had in 1967, it's a monster!

------------------
Rick McDuffie
Tarheel Jazz Q-tet
Debbie Elam Band
www.tarheelmusic.com

Michael T. Hermsmeyer · Post by **Michael T. Hermsmeyer** » 6 Mar 2003 2:30 am

Hey Rick, this may sound like an exceedingly simple solution, but it was for me: Do you have two speaker outputs? Are you using the one that says "extension speaker"? Try the other one. Many years ago, I traded a Twin back in after a week because I made this mistake, wondered why a Peavey Bandit 65 was blowing it away. I didn't realize the mistake I made until I bought my Dual Showman a few years ago. I simply plugged the speaker into the wrong output jack. Seemed like I had only 30 to 40% of the power I should have had. Switched the jack and WoW!! I can't tell you why this is without looking at the back of the amp, but these Fender guys like Ken and Tony can.
Just thought this might help, along with all the things that they brought up.
Thanks, God Bless,
Michael T.

------------------
UTILITY MAN PRODUCTIONS
'73 EMMONS D10 FATBACK, '92 EMMONS D10 LASHLEY LEGRANDE,
'85 DOBRO 60DS, '95 DOBRO F60S,
'95 MELOBAR CUSTOM, 1955 FENDER TRIPLE NECK STRINGMASTER. EVANS, FENDER, PEAVEY,
and MESA BOOGIE Amps.

Tony Prior · Post by **Tony Prior** » 6 Mar 2003 3:59 am

First off , I am not a real expert here on Fender amps, I do have some experience and did repair some amps back in the 80s. There are many on this forum who are well versed on these issues.

Concering the EXT out jask, that is to be used only after the regular speaker out is connected to an 8 ohm load. Thats why it is labeld EXT.

I am not certain about the wiring as I sold all of my manuals, but most likely the EXT speaker out is wired in a configuration which requires the impedance of the regular speaker output to bring the total load down to 4 ohms. It's possible that without the reg Speakers plugged in the EXT load alone may be 16 ohms..maybe higher, which results in a power output equal to a Fender Champ !

tp

Michael T. Hermsmeyer · Post by **Michael T. Hermsmeyer** » 15 Mar 2003 11:54 pm

How did your problem turn out Rick?

On the back of my Dual Showman Reverb, there are two speaker jacks. One says simply "Speaker" and the other says "Ext. Speaker". You are hooked up correctly if you are using a 4 ohm load (one 4 ohm 15" or two 8 ohm 12") plugged into the "Speaker" jack.

As Tony mentioned, the other jack should only be used after the first jack is hooked up. I assume that would be another 4 ohm load, but I am only guessing. Perhaps it is designed for two 8 ohm loads, I do not know.

Since a Dual Showman came in piggyback form, it could be a common mistake to use the "Ext. Speaker" jack because you are using an extension speaker. Perhaps Fender used the same backplates for twins and duals. A small oversight.

If this is not the cause of your trouble, then please follow Carl's advice as he is much more in tune with tube amps than I am.

Hope all is well with your amp.

God Bless, Michael T.

After reading Tony's last post again.....
Tony, am I wrong in assuming that the speaker out is for a 4 ohm load? I have an Evans Eclipse 4 ohm speaker in my custom walnut cabinet with my Dual Showman Reverb chassis. I don't use any other speaker in combination with the Evans. Is this ok? It has been fine for many years now, but if I am causing a long distance problem, please let me know. Thanks.

Sorry I don't have a better pic of the finished amp. My website is down. I'll try to take some tomorrow.

------------------
UTILITY MAN PRODUCTIONS
'73 EMMONS D10 FATBACK, '92 EMMONS D10 LASHLEY LEGRANDE,
'85 DOBRO 60DS, '95 DOBRO F60S,
'95 MELOBAR CUSTOM, 1955 FENDER TRIPLE NECK STRINGMASTER. EVANS, FENDER, PEAVEY,
and MESA BOOGIE Amps.

[This message was edited by Michael T. Hermsmeyer on 16 March 2003 at 12:00 AM.][This message was edited by Michael T. Hermsmeyer on 16 March 2003 at 12:11 AM.][This message was edited by Michael T. Hermsmeyer on 16 March 2003 at 12:13 AM.]

Tony Prior · Post by **Tony Prior** » 16 Mar 2003 4:00 am

Michael.I am not certain .It's been a while and I sold all of my manuals.

tp

Danny Naccarato · Post by **Danny Naccarato** » 16 Mar 2003 7:49 am

Michael,

Here's what I learned recently from Ken Fox and a tech guy here in town..... My '80 Vibrosonic (same as Twin, Dual Showman Rev) has a reg. speaker jack and Ext Speaker jack. The amp says 8 ohms and had a stock EV 15 8 ohm. When you hook up an additional 8 ohm speaker in the ext jack, the transformer "switches" to 4 ohms. Per Ken's and the local Fender guru, I've put a BW 1501 4 ohm in the regular speaker jack, and a Dead plug in the Ext. jack, so the transformer is switched to 4 ohms automatically.

Rick McDuffie · Post by **Rick McDuffie** » 16 Mar 2003 12:41 pm

Hi fellas- Yes, I've had the speaker plugged into the correct output jack. My tech says he needs to re-check the bias, but we haven't gotten around to it yet- too many other (money-making) projects!

I've got 2 8-ohm Scorpions in the cabinet, wired parallel, which gives me a 4-ohm load.

Rick

Michael T. Hermsmeyer · Post by **Michael T. Hermsmeyer** » 17 Mar 2003 7:53 pm

OK, so do I need to put a dead plug in the other jack?

Here is a new shot of my finished amp.

Michael T.

Rick McDuffie · Post by **Rick McDuffie** » 17 Mar 2003 8:12 pm

I'm not sure what good it's going to do to put a dead short on that output jack... a dead short equals no impedance, and if you've already got a 4 ohm load on the main output jack... gee, that sounds risky to me. That's going to take the impedance down to 2 ohms or less, isn't it?

The new amp cabinet looks great, Michael. Fender meets Boogie : )

Gino Iorfida · Post by **Gino Iorfida** » 17 Mar 2003 8:15 pm

Actually, if you plug nothing into the main speaker jack, you are running the amp into a dead short- the main jack is the shorting type, so if you accidentally unplug the cable the amp will not see the deadly 'no load' condition... only the newest of Fenders have switching jacks to change speaker impedance taps. Assuming your's is stock

Ken Fox · Post by **Ken Fox** » 17 Mar 2003 8:19 pm

Caution!! The 80's Twin (135 watt model) and other amps of that era (Super Reverbs and others) had an ultralinear output transformer. These amps all had a higher power rating than Blackface and early to mid 70's Silverface amps. These were the only amps in that era with a special switch arrangement to actually make a correct impedance match for an external speaker. The Twin of that era would actually put the external speaker load in series with the internal load and switch to an 8 ohm tap on the transformer. That way the internal 4 ohm and external 4 ohm load would be correctly matched. The regular Blackface and early 70's Silverface amps have a shorting jack on the main speaker jack. If no speaker is connected there, the amps sees a dead short and this will protect the output transfomer from a melt down (with a no load situation you will deliver all the power to the transformer primary windings, not good!). When you add an external speaker to a Twin, Showman or what ever amp from the Blackface and Silverface era, you are actually still operating on the same output tap of the transformer (these speaker jacks are merely in parallel). You will have an impedance mismatch, theoretically not so good. Most Fender amps (except a Super reverb with its 2 ohm internal load) will tolerate this. Due to reflected voltages back to the primary of the transformer (due to the impedance mismatch) there is some cause for possible long term damage to the primary windings and the plates of the power tubes. Why they put an extension jack on a Super Reverb is a great mystery. You would be better off to do a series/parallel wiring and get 4 ohms on a Super, before adding an extension speaker.

Rick McDuffie · Post by **Rick McDuffie** » 18 Mar 2003 4:55 am

So, if there's already continuity across the speaker output jacks (when speaker cables are unplugged), what's the benefit of putting a "dead plug" in one of them?

Maybe I'm misunderstanding the use of the term "dead plug". I took that to mean a plug that was shorted. Do you mean a plug that leaves the circuit open? This would actually raise the impendance, wouldn't it?