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Old 30th December 2012, 04:58 PM   #1
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Default Other Applications of Vacuum Tubes

Several DIY solid state amps use light bulbs as incandescent load resistors. For example, the De-Lite Amplifier by Mr. Pass, the SIT amp by Mr. Rothacher, and wrenchone's L'Fake amp. Mr Pass hailed their resultant sound as Organic and different in character than using common load resistors and current source loads. So, why not use the heaters of vacuum tubes in a similar application. Apparently, this idea is not new. Please see the thread in the Pass Labs Form by the DIYer wrenchone which has a title beginning with L'Fake...Its last page shows such applications. I'll reproduce mine in this thread.
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Old 30th December 2012, 05:52 PM   #2
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Default Alright Antoinel

Thanks for opening this thread. Look forward to seeing and discussing these types of amps. I'll post my "An Humble Amp" when I can get a readable schematic together.
Later......

Terry
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Old 30th December 2012, 11:15 PM   #3
DF96 is offline DF96  England
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A valve heater might work better* than a bulb, as it is likely to have greater thermal mass so will introduce less bass or signal envelope distortion. Of course, those people who prefer distortion will prefer to use a bulb.

* in this context, 'better' really means 'less badly'
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Old 31st December 2012, 12:11 AM   #4
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Default curious resistors

Quote:
Originally Posted by DF96 View Post
A valve heater might work better* than a bulb, as it is likely to have greater thermal mass so will introduce less bass or signal envelope distortion. Of course, those people who prefer distortion will prefer to use a bulb. * in this context, 'better' really means 'less badly'
Hi there: Intend to use my toster, ele'c coffee pot, and toster oven for circuit reistors, and if needed for parallel output devices a pair of waffel irons. To use an old jazz term...should that "should cook". ....regards, Michael
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Old 31st December 2012, 04:35 AM   #5
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Look at Pete Millett's Starving Student Headphone amp. It uses the tube heaters as the load for a mosfet follower. The amp was succesful enough to deplete the worlds supply of 19J6 tubes.

Starving Student hybrid
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Old 31st December 2012, 12:43 PM   #6
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Thank you all for your valuable input. I'll post today a picture of the prototype. I wish you a happy, healthy, and prosperous 2013.
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Old 31st December 2012, 06:39 PM   #7
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Quote:
Originally Posted by Antoinel View Post
Thank you all for your valuable input. I'll post today a picture of the prototype. I wish you a happy, healthy, and prosperous 2013.
A picture of the prototype amp is attached. I'll show its attendant schematic in a following post. I built it on a 1" by 6" wood board. Its power supply is a regulated dual +/-15 VDC, and enters at the terminal strip on the left of the picture. Ouput power to a loudspeaker [full range 8 Ohms or 16 Ohms] exits at the terminal strip via the the DC blocking cap [4,700 uF]. The circuit of LM386 was assembled on an experimenters proto board. The vacuum tubes [12AX7] were mounted on terminal strips by soldering on them one of their mounting holes.

I was pleased with the sound quality. Clear, detailed, no hum and tonally balanced. I'll have more on its subjective and objective measurements in upcoming posts.
Best regards
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Old 31st December 2012, 06:56 PM   #8
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Default Schematic of proto amp

Here is a picture of the schematic of the proto amp. Please go to Posts # 91 and 92 in wrenchone's thread which is partially entitled "L'Fake..." in the Pass Labs Forum for additional discussion of it.
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Old 31st December 2012, 08:29 PM   #9
Enzo is offline Enzo  United States
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Can't remember just where, but some guitar amps have been made with preamp tube heaters as cathode resistor for the power tube.


By other uses, I assume you do not mean things like computer logic, thryistor tubes controlling solenoids, and so on.
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Old 31st December 2012, 09:56 PM   #10
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Originally Posted by Enzo View Post
Can't remember just where, but some guitar amps have been made with preamp tube heaters as cathode resistor for the power tube.


By other uses, I assume you do not mean things like computer logic, thryistor tubes controlling solenoids, and so on.
Thanks Enzo for your info. Please show schematic(s) when you stumble upon them. Incandescent load apps. Surprisingly [or not] the modulated heater current [while driving a loudspeaker] reaches the cathode, grid and plate as a varying voltage.
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