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| Preamp + headphone amp http://dcaudiodiy.com/phpBB3/viewtopic.php?f=4&t=1122 |
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| Author: | SoundMods [ February 2nd, 2018, 1:34 pm ] |
| Post subject: | Re: Preamp + headphone amp |
Pelliott321 wrote: Two questions Please explain the feedback loop. Why the caps and why is it connected to the input tube's cathode? If one did not need the headphone output what transformer would ne use or just loose it and use a cap Feedback to the first stage cathode is not unusual, however; that's a strange one to say the least. The feedback loop sets the overall gain -- so why capacitive-couple the feedback loop which results in full gain below approximately 6-Hz. ???? |
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| Author: | Pelliott321 [ February 2nd, 2018, 1:43 pm ] |
| Post subject: | Re: Preamp + headphone amp |
Dave I would be interested in more info about the 6C45P transformer coupled spud amp |
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| Author: | David McGown [ February 2nd, 2018, 2:55 pm ] |
| Post subject: | Re: Preamp + headphone amp |
Pelliott321 wrote: Dave I would be interested in more info about the 6C45P transformer coupled spud amp Paul, Very simple circuit. But been a while since I put it together. I used a pair of custom wound Electroprint line output transformers, 3K:600ohm that I had from a preamp project. Just a simple grounded cathode circuit, with LED bias (though I might have replaced that with SiC diode bias, have to check). Running around 30 mA through the tube. Carbon comp grid stoppers (x2) cathode stoppers (x4) and plate stoppers. Used shunt regulators on each tube, consisting of a 0D3 voltage regulator fed by a DN2540 cascode current source (150V). Power supply uses tube rectifier to choke input supply, filter caps are all motor run (oil), with Russian teflon bypasses. Goldpoint attenuator for a volume control. I will have to trace out what I did and write out a schematic. David |
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| Author: | Jay Bala [ February 2nd, 2018, 4:34 pm ] |
| Post subject: | Re: Preamp + headphone amp |
DC block cap and a filter. Did anyone try this "Zen"? Tom? http://sound.whsites.net/project36.htm |
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| Author: | tomp [ February 2nd, 2018, 5:41 pm ] |
| Post subject: | Re: Preamp + headphone amp |
Other than the Cherry Bomb I never built a class A power amp. Although the CB is a very interesting and unique design my other SS amps will blow it away. I don't use it on a daily basis. For phono and line level stuff I use some of the modern Op Amps. Much simpler if you just follow a few rules. Some people think simple is boring but if I can get great results with less hassle I'm all for it. |
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| Author: | Jay Bala [ March 4th, 2018, 7:26 pm ] |
| Post subject: | Re: Preamp + headphone amp |
Is there any poor man’s Telefunken ECC83 / 12AX7 Smooth Plate? These are $500. Any suggestion for high-quality low gain 12AX7? or 12AX7 subst: 1964 RCA 5751 Black Plate JAN 5751 U.S. Made |
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| Author: | David McGown [ March 4th, 2018, 8:34 pm ] |
| Post subject: | Re: Preamp + headphone amp |
Concerning 12AX7's I personally like the Gold Lion B759, but there are so many options out there, it is hard to say, and it probably depends on how it is used. If you want a Telefunken copy (made on the same tooling), a vintage EI smooth plate is alot cheaper than $500, but not sure if that is as good as the best of modern production these days. David |
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| Author: | Roscoe Primrose [ March 5th, 2018, 8:15 am ] |
| Post subject: | Re: Preamp + headphone amp |
If you're not stuck with 9-pin miniature, 6SL7... |
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| Author: | Jay Bala [ March 5th, 2018, 8:53 pm ] |
| Post subject: | Re: Preamp + headphone amp |
Thanks David and Roscoe. |
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