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Post subject: Black Knob, Dual Input Fender Twin Amp Questions
Posted: Sun Apr 01, 2012 10:03 pm
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Greetings from Tulsa! I recently purchased a dual input Twin Amp (for $300 :shock: ) that came with a pair of eminence speakers rated at 8 ohms; one Tonespotter and one Tonker. I don't personally care for how they sound in the Twin Amp. To my untrained ears, the clean channel sounds like a blackface and the overdrive channel is early mesa boogie, but I feel as if the tone could be better, so I'm looking for speaker suggestions. I dropped the two middle tubes and switched the impedance selector in accordance to the owners manual and run the amp at 60 watts, playing primarily clean and over-driven rock music. If I utilize the 1/4 power switch, the amp gets extremely hot, which I assume isn't normal, so I'll continue running it with two tubes.

I'm also having a problem with the foot switch/channel switching. The amp will run on the normal channel or the gain channel, but not the overdrive channel. When I unplug the foot switch, it will only run on the overdrive channel. I do know that the knobs are push pull for channel select when the foot switch is unplugged. Am I missing something here or is there a malfunction within the amp? I just had it recapped and re-tubed and I feel that when I get this thing sorted out it will be a great sounding/versatile amp. Any thoughts or suggestions would be greatly appreciated.

Regards,

Roland

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Post subject: Re: Black Knob, Dual Input Fender Twin Amp Questions
Posted: Sun Apr 01, 2012 11:21 pm
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I would try a pair of Eminence Texas Heat's, Celestion V30's, or -- if you have a couple of roadies to load and carry the damn thing -- Electro-Voice EVM-12L's.

Arjay

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Post subject: Re: Black Knob, Dual Input Fender Twin Amp Questions
Posted: Mon Apr 02, 2012 7:25 pm
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Thanks for the reply Retroverb. Anyone have any idea whats up with the footswitch and the quarter power switch?


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Post subject: Re: Black Knob, Dual Input Fender Twin Amp Questions
Posted: Tue Apr 03, 2012 8:53 am
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Your channel switching isn't working properly. You should be able to access all three modes (clean, "vintage drive", drive) with or without the footswitch. Since the push/pulls aren't working correctly when the footswitch is unplugged, the malfunction is probably in the amp, not the footswitch. It's a complicated circuit with several relays and opamps, but those amps were a little prone to wiring problems so it might be something as simple as a cracked solder joint.

When I had one it didn't run hotter in the 1/4 power mode. That switch reduces the plate voltage, it doesn't turn it into Class A or switch to cathode-bias so it shouldn't run any hotter. It doesn't run noticeably cooler though -- in either power setting the amp will get very warm if you crank it up and play for an hour. (If it gets significantly hotter in the 1/4 power mode, something's wrong though.)

Mine had the stock speakers. They sounded wonderful for the clean and vintage drive channels but the lead channel sounded fizzy and harsh. I was never sure if that was the speakers or the lead channel itself -- I never got around to swapping speakers in it (I decided it was way too heavy and loud for my needs).


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Post subject: Re: Black Knob, Dual Input Fender Twin Amp Questions
Posted: Sat Jun 23, 2012 6:59 am
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[quote="71cutty"]Greetings from Tulsa! I recently purchased a dual input Twin Amp (for $300 :shock: ) that came with a pair of eminence speakers rated at 8 ohms; one Tonespotter and one Tonker. I don't personally care for how they sound in the Twin Amp. To my untrained ears, the clean channel sounds like a blackface and the overdrive channel is early mesa boogie, but I feel as if the tone could be better, so I'm looking for speaker suggestions. I dropped the two middle tubes and switched the impedance selector in accordance to the owners manual and run the amp at 60 watts, playing primarily clean and over-driven rock music. If I utilize the 1/4 power switch, the amp gets extremely hot, which I assume isn't normal, so I'll continue running it with two tubes.

I'm also having a problem with the foot switch/channel switching. The amp will run on the normal channel or the gain channel, but not the overdrive channel. When I unplug the foot switch, it will only run on the overdrive channel. I do know that the knobs are push pull for channel select when the foot switch is unplugged. Am I missing something here or is there a malfunction within the amp? I just had it recapped and re-tubed and I feel that when I get this thing sorted out it will be a great sounding/versatile amp. Any thoughts or suggestions would be greatly appreciated.

Regards,

Roland

[ I have an amp here of the same vintage/knobs/silver face. This one howls on Chan 2 with no input. One of the 12AT7 tubes at the reverb circuit was microphonic. Chan 1 master volume wont work and signals play thru the amp with ALL the volumes turned off.
Chan 1 LED doesnt light either. What a mess!!!...I'll be back with more details soon. I repair audio for a living so this one NEEDS to work....I have another twin like it that switches channels by itself. Need to pick up at Retro Music in Keene NH today. You guys should check out his website. LOTS of vintage amps and guitars.

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Post subject: Re: Black Knob, Dual Input Fender Twin Amp Questions
Posted: Mon Jun 25, 2012 6:58 am
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This is the model known as the "94 Twin". I’m running one of these now myself.

I’m thinking there is something wrong with the switching. Mine is also having problems with channel switching (though not exactly the same problem that you’re describing*) so maybe these are prone to that for some reason.

*I am generally *not* using the channel switching much on mine and am getting my distortion and overdrive from pedals. I do still keep the footswitch out because I use it to control the reverb. Sometimes when I am playing, one or both alternate channels will cut in and out. This results in a really scratchy sound coming out of the amp and the indicator lights for the channel will “stutter”.

Regarding the 1/4 power, I have used mine like that, but have not had the problem you are describing. First, as noted earlier, the back of the amp will get warm when running regardless. Mine gets noticeably warm, but not what I’d call “hot” no matter how I run it.

I have heard of others with a similar problem with this amp, though, with the amp running dangerously hot in the 1/4 power mode and seem to recall that this was a malfunction in the circuit controlling that. You might talk to your amp tech about it or do some googling to see what you can learn about it. Use (94 Twin as your search key as that's how most people will refer to this model).


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Post subject: Re: Black Knob, Dual Input Fender Twin Amp Questions
Posted: Mon Jun 25, 2012 9:03 am
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RedShark92, your random-switching problems are what can happen if you use a guitar cable to connect the fooswitch instead of using a speaker cable. Some shielded guitar cables work fine, some cause constant problems, others cause intermittent problems (you can use the same guitar cable for a long time without problems, and then have it start causing problems).

The manual has a brief comment saying that speaker cable is "preferred" for the footswitch, but it doesn't explain why. People seem to naturally assume that shielded guitar cables are the proper choice for any low-power connection, and since guitar cables often work fine it's easy to get in the habit of using them and not even think about the cable as a possible suspect when channel-switching problems happen.

A worn cable that shorts/opens on its own would cause similar problems, whether it's a speaker cable or a guitar cable. Since no audio signal flows through the footswitch you wouldn't hear the snaps, crackles, and pops that bad cables normally cause. Footswitch cables tend to get stepped on and yanked on, kinked and stretched. But because they don't crackle and buzz when you move them, it's easy to forget that they can develop intermittent problems just like any cable.

The cable may have been the first thing you checked when your channel-switching started misbehaving. But it's easy to overlook the simple things -- I do it all the time.


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Post subject: Re: Black Knob, Dual Input Fender Twin Amp Questions
Posted: Mon Jun 25, 2012 9:30 am
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strayedstrater wrote:
RedShark92, your random-switching problems are what can happen if you use a guitar cable to connect the fooswitch instead of using a speaker cable. Some shielded guitar cables work fine, some cause constant problems, others cause intermittent problems (you can use the same guitar cable for a long time without problems, and then have it start causing problems).


I'm not using a guitar cable - I'm using the speaker cable that came with another Fender amp I have (Princeton Chorus). It is fairly old, though, so it's possible that it's a bad cable. I'm playing it again tomorrow night so I'll try it without that and see what happens.


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