SS Tremelo for my tube intercom guitar amp - diyAudio
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Old 2nd March 2014, 04:42 AM   #1
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Default SS Tremelo for my tube intercom guitar amp

I realized I didn't have enough B+ to use a tube oscillator in my (Iso xfmr driven) line AC supplied intercom/amp, so I built the Weber circuit. They currently aren't selling it, supply problems they told me, so I just breadboarded it. Used a 9V battery (I like single supply OP amps!) - their circuit doubles then rectifies the 6.3VAC heater voltage - just to get it up and running. Only about 1.5Vp-p, now to figure how to integrate it into my amp!
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File Type: jpg 1.7Vp-ps.jpg (152.1 KB, 28 views)
File Type: jpg WEBER SS CKT ZOOM.jpg (127.6 KB, 28 views)
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Old 2nd March 2014, 06:19 PM   #2
JMFahey is offline JMFahey  Argentina
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Is that enough?
Looks like very little amplitude to do much, if any at all.
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Old 2nd March 2014, 07:52 PM   #3
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Have been testing it, and it is more than enough! Varying grid voltage on a preamp tube by 1.5 volts (by varying the cathode bias with the tremelo) worked so well I had to put a 5K pot on the tremelo to tone it down.... Weber also has examples of inserting the tremelo in the DC bias supply for power tubes, which should notice a couple of volts up & down? Also, I'm only using a 9-volt battery. More supply voltage (up to 32 VDC) will increase output swing. You could push plate voltages around with that (perhaps - I'm pretty much still a newbie on this, but I'm learning).
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Old 4th March 2014, 01:31 AM   #4
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At that voltage, you should have a B+ around 150 to 180 volts DC, correct? This should have been plenty for a 12av6 based tremolo such as was included in many period budget amps.
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Old 4th March 2014, 03:00 AM   #5
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Voltage doublers use large electrolytics at medium to high voltage ratings (not stuff I have laying around!), and I'm having good success just inserting it at the cathode. Probably will take 12VAC off a preamp tube (the last one in line - heaters are strung across 117VAC, tubes have 34, 50, 12 & 12 volt filaments), 1/2 wave rectify it, add an electrolytic, and have 10-11 VDC (Weber circuit uses a voltage doubler on a 6.3VAC winding). Best thing I've done to the original circuit is smooth out the "points" on the tremelo wave with a cap from pin 5 to gnd (thanks to help from a thread I posted on the Solid State forum!). Eliminated a "slapping" I was getting in the amp.

Last edited by LATUBEGEEK; 4th March 2014 at 03:04 AM.
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Old 4th March 2014, 03:33 AM   #6
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Nevermind, you should have about 130-140 then, which would let half of a 12av6 oscillate. Just search for 12av6 tremolo. And also, I hope you dont change any of the current draws in the filament circuit as it will change their operating voltage.
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Old 4th March 2014, 05:17 AM   #7
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I'm not sure where you're getting this "130-140' V from....and a 12AV6 is a single triode, so how can 1/2 of that oscillate? Yes there are plenty of tube tremelos using the 12AV6, it has a high enough mu. A 12AX7 (or a 12AT7 barely) works also, but I need a lo mu 1st gain stage, and don't want to use a hi/lo mu dual triode, so I've settled on a 12AT6 or 12AU6 (single triodes) for a 1st preamp stage, and going SS for the tremelo. Finally, taking a few mA (to run a chip tremelo) off a heater? It won't even notice it....
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