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Fender Super Twin Bass Head

#181
Glazenn said:
JohnK_10,

Do you have a cooling fan in your Super Twin head cabinet? I read that over-heating in a head cabinet (with 6 power tubes) could be an issue due to air flow constraints (that is almost not the case in a combo).
Click to expand...
yes, in that one I installed a fan plugged into the rear panel AC socket.

Glazenn said:
Do you know when Super Twins had the backplate power socket (and the ground switch) added? On mine (sn #B63085), the chassis has holes to receive the socket and the switch, while the backplate doesn't. Both features are shown in the '180 watt Guitar Amplifier' schematics dated (or numbered?) 012380.
Click to expand...
I don't remember what years had an AC socket on the back panel, but mine does.

Glazenn said:
Last one, do you have a shield (24-1/2" wide metal sheet) under the cabinet upper panel, that comes above the chassis? I have one in the combo that is just stappled onto the wood.
Click to expand...

i'd have to look at it again, but I don't think that I remember it having one.
 
#182
Glazenn said:
Last one, do you have a shield (24-1/2" wide metal sheet) under the cabinet upper panel, that comes above the chassis? I have one in the combo that is just stappled onto the wood.
Click to expand...

It helps to have the shield in place. I buy rolls of aluminum from the roofing department of a hardware store. Perfect thickness and it is pretty inexpensive. The metal can be easily cut to size with heavy scissors or score it and bend it back and forth until it breaks. Staples work well.
 
#183
It's done! The amp works fine. Just a few minor things still to add: a shield, a back panel, maybe a cooling fan, and redo the grillcloth with the pattern the right way this time...

All tubes except the 12AU7A are Fender, likely original from factory. The 6 power tubes were not in place when I received the combo (actually, I think they may have dropped during the transport, I found them scattered on the bottom, one was even stuck in a loudspeaker, but by chance, none was broken), so I don't know which goes where. Just betting they are a matched sextet...

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#188
I have ordered new electrolytic capacitors for my Super Twin. Hoping it will remove all the distortion I have in the lower notes (that mainly happens on the B and E strings when the amp is warm) and some minor hum noise.
The Studio Bass has two 750µF 3V bypass filter caps (Fender schematic 013606), one for each of the V1 and the V3 (to pin 8) while the Super Twin has a 750µF 3V and a 150µF 6V respectively (Fender schematic 012380).
On the same matter, I have read on the [URL="Invalid Link Removed that "the larger the cap, the more lows that are boosted". So, I will replace the 150µF 6V on V3 with a second larger cap (actually a pair of Sprague TVA1163 1000µF 16V as 750µF 3V is now out of stock) as it is on the Studio Bass. I will report of any noticeable difference.
Any comment ?
Note : JohnK_10 said in another thread there is even no need to replace these 750µF 3V caps with new ones as they barely age or wear.
 
#189
johnk_10 said:
Just thought I'd post a few pics and info on my new (old) Fender Super Twin amp that I converted to a bass head.

I made the head box cabinet from pine and went over the circuit to make sure that everything was up to snuff. I replaced the bias and filter caps with new Spragues and also installed a bias control (in its stock form, the amp just has an output tube "balance control"). After playing thru it, all i can say is WOW! For some reason this amp sounds alot more powerful and transparent than the previous three fender "Studio Bass" heads that I've had, and they have basically the same circuit. I'm currently running Chinese 6L6GC's ( look like coke bottle KT66's) in it and so far, they are my favorite sounding output tubes in this amp (and inexpensive too). Even with the tone controls set flat, it sounds awesome, and can go from "old school" vintage tones to modern since its EQ is so flexible. Instead of the standard feet, I made some feet out of 1/2" thick sorbothane and now the head doesn't "see" or feel ANY of the cabinet's vibration, even at extreme levels.

This just might be the best sounding tube bass amp that i have, and that's comparing it to my two SVT's (a '69 and a VR), my Sound City Bass 150, my Sunn 190B and 2000S, and a Traynor YBA200-2. It is super punchy and feels like it's almost as powerful as an SVT (2/3rd's as powerful anyway) so I just put it on the scope and ran a few output tests on it. Just before a 400Hz sine wave distorts on the scope, it is putting out 193.667 Watts RMS at 4 ohms, but it feels like even more.

To me, these Super Twins are one of the best kept secrets out there for bass and they can be found complete with the 2-12 cabinet for around $500.00 or less. Then you can sell the empty cab and speakers and you'll have about $300 into one of the best bass heads that you'll ever play thru. They also made a Super Twin Reverb, but I didn't want the verb or the extra circuitry for it.

anyway, here's some pics of it with it's 2-15 JBL K140 cab:

supertwin-2-w.jpg


supertwin-4-w.jpg


supertwin-6-w.jpg


supertwin-5-w.jpg
Click to expand...

Is this a Fender cabinet, or did you build it yourself? I'm very much interested in this thin design, could you share the dimensions please?
 
#196
well, I have to disagee completely. I've gigged with it a lot and it's a awesome sounding cab with the K140s. and that's with a loud rock band with no FOH bass support.
and I just have to ask, are you saying that you actually had one with K140's in it? or were they some other speakers? the stock speakers were awful in it.

yes, my 200S with 2X15 K140's was a bit louder (especially a few feet out, but this one has always 'felt' louder near field, and my drummer (sitting slightly off to the side and behind it) loves when I use it.
 
#198

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#199
Looks unreal! Those 15s kill!

Question for you guys. I have a 2x15 as well... But for rehearsals and such I found myself needing something a bit more portable. I picked up a 1x15. Sounds great, issue is its 8 ohms. I know I'm not getting optimum power but I want to know if mismatching the impedance on the ST will hurt it at all?
 

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