Dual Showman/Weber C15CA tone machine (long)

[Cliff Swanson]

Some of you have encouraged me in email to report on my new amp rig, so I decided to make it a "public service" announcement here . I recently traded a '73 sf Super Reverb straight up for a sf Dual Showman head. I did this via the Internet...pics of the amp head and phone conversation with the owner of the music store in Atlanta where the amp was for sale. I could tell from the aluminum grill trim strip that the amp was '68-69 vintage, but they hadn't taken the chassis out to check the codes for a more exact dating, and the store owner was reluctant to do so. Well I figured it was worth it for me to trade and I'd get the amp brought to AB763 (blackface) circuit specs if I needed. Upon receiving the amp and pulling out the chassis myself, I discovered, much to my delight, that the amp is in fact the much desired AB763 circuit, and that this particular amp is a very early sf version having been built in the Fall of 1967! (Chassis date code T353967, all pots and transformers '67 date coded.)

I bought NOS Phillips 7581A power tubes and had the amp biased by fellow Forumite and local amp tech, Matt Farrow (thanks again Matt!). Matt also modded the amp to include a vibrato circuit defeat (wired to the ground switch so no cosmetic changes in the amp) and reconfigured the foot switch jack as a line out.

Doug Holt of Jenkins Sound Shop built me a downsized 1x15", open back cabinet that I loaded with a Weber VST C15CA, aka "California 15", speaker. The speaker cab is 20" tall x 23.5" wide x 10" deep; which matches the width and depth of the amp, and is finished in black tolex with blue/black/silver grill cloth to match the amp cosmetics.

OK guys...I'm playing my mica Fessy D-10 with a Lawrence 910 pickup in the E9 neck, and this rig kicks tone butt!!! I wouldn't hesitate at all to load the California 15 into anything as a replacement/substitute for a JBL D130F The Webers are available in 4 or 8 ohm versions with choice of paper or aluminum dust caps...mine is 4 ohms/paper cap. I chose to go the amp head and cabinet route to cut down on the weight factor per unit (instead of a Twin for example), and I'm happy I did. For anyone considering the idea of buying an old Twin and converting it to a 1x15" from the 2x12" ala Vibrasonic, or doing what I did with a head and cabinet arrangement, I'm HIGHLY recommending the Weber C15CA speaker. At $95 I just don't see any substantial reason beyond "gear snobbery" to spend more on a JBL that's old and expensive. From my tone-freak perspective, the sonic qualities of the Weber are a dead-on match. I played this rig mic'd at a gig last night on a fair sized stage in an open room filled with about 400 people. With the amp set a few feet behind me and the volume on 4 I could hear every string and the tone was resonant, round, rich, and "present" without being thin or overly glassy. All-in-all a great tube rig for pedal steel IMO.

Thanks to all of you who responded to my posts here as I sorted through some technical things relating to tubes. I have a small variety of preamp tubes with which I'm going to experiment to see how the tone is affected and what seems most pleasing to my ears. Right now I'm running 7025s at the front, but I'm going to change to 5751s and see how I like them.

Cat<FONT SIZE=1 COLOR="#8e236b"><p align=CENTER>[This message was edited by Cliff Swanson on 20 January 2001 at 11:48 AM.]</p></FONT>

[Mark Herrick]

Regarding your evaluation of the Weber 15" speaker. How would you compare the Weber to the Black Widow 1502 used in the Nashville 400? Would the Weber be a viable replacement for that speaker? Also, any tonal differences between the paper dust cap speaker and the aluminum dust cap?

[Ron Whitworth]

CONGRATULATIONS Cliff;
How does it feel to be there in "tone heaven"??..It sure does get funny that some keep reinventing the wheel & we end up back at the original wheel..Glad to hear that your rig turned out sooo nice sounding..I just love the sound of my '68 Showman Reverb(modded back to '66 Twin specs)& my JBL D130
in a seperate cab also..I have many amps but NONE sound as good-some come close tho..
Later...Ron

[Chris DeBarge]

Awright, good for you Cliff! How about a sample of the sound?

[Cliff Swanson]

Thanks for the replies...

Mark - I can't really reply objectively to a comparison between the Weber and the BW other than to say that the Weber is designed and built by Ted Weber and Co. to be a direct replacement for the JBL D130F, so it's voice is that and not a BW. I can tell you that I tested the Weber using my Evans SE150 amp by simply unplugging the Eminence speaker in the amp and connecting the Weber cabinet. The sound of the Weber is more open than the Eminence to my ears. I'd give serious consideration to replacing the Eminence with a Weber in my Evans amp.

Ron - glad to hear your rig is up and running and meeting your expectations too! Thanks for your help and advice along the way.

Chris - Responding to Mark's question got me thinking about the idea of doing a comparative sampling of the Evans amp and the Dual Showman through each speaker, Weber and Eminence. I'd play each sample using the same guitar. Could be interesting. I'll see what I can do about this.

[Bob Hoffnar]

Cliff,
I am interested in the difference between NOS Phillips 7581A power tubes and 6L6's.

thanks, Bob

[J D Sauser]

Bob, the 7581 is a 6L6GC but can withstand much higher plate voltage and therefor a "hotter" bias. What all that means to you is that you can have much more headroom or "clean" volume.
I've had them and found all that to be true but also that it sounded too harsh and steril for me.
I now went into a completely opposit direction using lower output 5881 (6L6WGB). I like my tube amps to be never really clean and also never really crash into real distortion... but that's my personal preference for that "old", sweet sound.

Read more here: http://users.erols.com/bluestat/#7581A


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The future belongs to culture. jaydee@bellsouth.net

[Cliff Swanson]

Bob,

What JD says is right on. Go to the web site he's referenced. It's Mike Kropotkin's site and Mike is a real tube guru. I had a lot of email with him while I was making initial decisions about how to tube my amp and he's very helpful. I bought my power amp tubes and a phase inverter tube from him.

Basically, I'm approaching the tone picture wiht the idea of using the 7581A power tubes as a base upon which I'm modifying the signal by using different preamp tubes. I'm in the process of trying out a few variations on the 12AX7 vs 12AY7 vs 12AU7 types of preamp tubes. One of the reasons I chose this route is because good quality preamp tubes can be had for quite substantially less investment while in experimentation mode than can a matched quad of power amp tubes. It's just another way to approach the whole thing.

I am quite sensitive to the harshness that some Twins present with a steel guitar and I think that JD is experssing the same sentiment. Honestly, the 7581As are not harsh or brittle sounding at all to my ears in this amp. Right now I've got RCA 5751s in the preamp gain slots. These tubes have slightly less gain than a 12AX7. I like the sound a lot. I've also got some military versions (JAN designation in tube nomenclature) of the 12AU7 and 12AY7 tubes. Each of these has less gain than teh 5751 as well, and I'm going to try them all using the same 7581A power amp quad. Maybe use one type in one channel and a different type in the other channel of the amp.

Sorry for running on here .

Cat

[Bob Hoffnar]

Cliff,
Yea, I think that power tubes are the key to the sound. Then working up from them is the way to go also. I like KT88's and EL34's the best so far. There is a smoothness of response to them in the mids that I find lacking in a 6L6. Hopefully I'll get to check out your set up someday. It seems like a fantastic rig.

JD, Thanks for the link and info.

Bob