Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Foreplay III => Topic started by: craigtone on December 15, 2012, 08:21:06 AM
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I just sorted through my box-o-tubes and found a stash of about a dozen 6CG7/6FQ7's. I did a Google search and found many preferred them over the 12AU7. I myself have struggled with the 12AU7 over the years in my Foreplay III and the driver of my ST-70. I have "compromised" on the RCA Clear Tops.
I dug up an old thread on the AA forums and modified my Foreplay III to use the 6CG7's with a grounded shield and I was blown away! The bass bloomed and there is more depth to the sound (front-to-back soundstage). Female vocals almost have an eerie 3-D sound to them now as well.
For those considering this upgrade, I give it 3 thumbs up (???)! It only took about 30 minutes with a soldering iron:
1. Unhook heater wires from the 12AU7 tubes.
2. Unhook heater ground reference from Pin 9 of the one 12AU7.
3. Re-wire the heaters to Pins 4&5 of the 12AU7's (observe polarity!).
4. Tie the heater ground reference to Pin 4 of the one 12AU7.
5. Tie Pin 9 of both 12AU7's to the closest ground terminal (one used for cathode LED ground).
6. Replace 12AU7's with 6CG7/6FQ7's.
7. Enjoy!
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hi
i am glad it sounds so good
i just used an adaptor and plug a pair of 6sn7 in and it was an improvement balanceced spectrum an more base definition
enjoy
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interesting stuff. Got to love this hobby...
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Hmmmmmm, no resistor changes? I remember one of the finest preamps I heard used a single 6FQ7 in each channel. I might have to make an adapter and buy some tubes.
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I always loved the days of alchemy. It lives in audio... You call me a dreamer - but I'm not the only one.
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But isnt the heater voltage different on 6CG7(6 volts?) compared to a 12AU7(12 volts)
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But isnt the heater voltage different on 6CG7(6 volts?) compared to a 12AU7(12 volts)
The tube can be run in series, (12.6v) or parallel, (6.3v).
Cheers,
Geary
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The FP 2 and III had a 6.3V heater winding with higher current. For a 12AU7 the 12.6V heater arrangement draws 0.15A, the 6.3V heater wiring draws 0.3A, double what is drawn at the double voltage wiring. There is no free energy but the center tapped heater allows for greater compatibility.
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gaylons/grainger, Thanks. Now that makes sense.
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I am going to give this tube swap a go this weekend.
It's been nearly 6 years since I've played with my Bottlehead gear (Foreplay 1 and Foreplay 3, Seduction and Paramours) and the system fired right up with nor problems! It is funny to see how my soldering evolved from the the original Foreplay and Paramours to the newer stuff. Overall the system is sounding kind of shouty...could be the speakers and the new environment they are in...it's too soon to tell.
Love this board
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I too, have had the shout problem. In my case it was the speakers. Controlled that problem with device from Decware. Seems like it was called gizmo. Some kind of coupling transformer with a variable input, allowing different effects for different speakers.
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How about trading something for a couple of your excess stash of these tubes? interested? Jan Olsen.