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My idea... [message #30002] Wed, 22 December 2004 13:11 Go to next message
Damir is currently offline  Damir
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Registered: May 2009
Illuminati (2nd Degree)
Build the linestage in little larger chasis (enough additional space for two SE OPTs and two tube sockets), with overdimenzioned PS (additional DC current say >120mA), with B+ about 300V. Choose OP for the 5687 a little higher (15-20mA, Ugk=4-6V, Uak=110-150V), CCS load.

Then we can build line stage first, with amplification about tube mu, or 17. We can use it for (pre)amplification of low-signal sources (hundreds of mV) to "drive" power amplifier.
But, our linestage can be a good "driver" for SE tube amp with CD player input - 2Vrms, say for EL34 in triode, or even 2A3/6B4G.
Once "armed" with experience building line stage, additional work for SE output stage would be trivial :-).

Re: My idea... [message #30006 is a reply to message #30002] Wed, 22 December 2004 15:11 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
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Registered: January 2001
Illuminati (33rd Degree)
What do you think about maybe doing a power amp? Or maybe a headphone amp?

Re: My idea... [message #30011 is a reply to message #30006] Thu, 23 December 2004 08:41 Go to previous messageGo to next message
Damir is currently offline  Damir
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Registered: May 2009
Illuminati (2nd Degree)
Thank you for your confidence. It`s no problem - when we have a driver, SET power amp is just a few resistors, capacitors, OPTs, output tubes+sockets. But - if we use about 300V B+, then we have a few choices for the output tube. One of the simpler solutions would be EL34, triode connected.
Pro`s - IDHT with "standard" 6,3V heater, easy to drive (say 16Vrms max, then our line-stage can "drive" it with 1Vrms input, +"reserve" 6dB with 2Vrms CD output). Bias is easy - just one resistor + capacitor (cathode bias).
Con`s - With Uak about 280V, and Ugk =20...24V, and OPTs with Za=2,5k-5k, we can expect only about 2-3,5W output. Sensitive speakers is a must...
Another candidate could be 2A3, "classic" OP (Uak=250V, Ugk=-45V, Ia=60mA, Za=2k5, Pout=3,5W). "Cool" DHT, but now we have some complications - we need 2,5V filament winding, filament hum balancing pot, and the most important - 2A3 "needs" 45Vp=90Vpp=32Vrms input AC voltage for max. power. Our 5687 linestage has A~17 and this is just enough, but with no "reserve" - it`s desirable to have at least 3dB more amplification, for "quiet" CDs. We can (almost) get it if we use similar ECC99 tube (mu=22).
Well, I`d like to see some discusion (if anybody is interested) - what to do - separate linestage and power amp, or no. Then - which tube to use, topology, etc.
I can post a schematics, calculate the component values, give descriptions and some building guidance, etc.
Where to find the parts - I`d like to see a discussion, too.

Re: My idea... [message #30012 is a reply to message #30011] Thu, 23 December 2004 10:10 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18670
Registered: January 2001
Illuminati (33rd Degree)
What's your favorite output circuit?

Re: My idea... [message #30013 is a reply to message #30011] Thu, 23 December 2004 10:21 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
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Registered: May 2009
Illuminati (13th Degree)
I personally like the idea of a seperate linestage at this point which enables us to tinker with the circuit independant of the power section. Using the 5687 linestage as a driver stage for a future 2a3 SE amp is a great idea. Do you think the linestage can be used as a building block for this application?

Line stage [message #30014 is a reply to message #30011] Thu, 23 December 2004 10:42 Go to previous messageGo to next message
colinhester is currently offline  colinhester
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Registered: May 2009
Location: NE Arkansas
Illuminati (3rd Degree)
I vote for the line stage.

The amps wpuld be next the next obvious progression. However, instead of using the 2A3 is there another, less well known, power tube we could use? I don't know, just something to be different......Colin

Favorite output circuit [message #30019 is a reply to message #30012] Thu, 23 December 2004 14:39 Go to previous messageGo to next message
Damir is currently offline  Damir
Messages: 1005
Registered: May 2009
Illuminati (2nd Degree)

Well, I didn`t try them all, of course. The last 5 years I listen to the music through my DIY monoblocks (PPP, 4xEL34 or 5881 sometimes, concertina phase splitter, Plitron/Amplimo toroidal OPTs, triode or UL, no NFB loop). I`m satisfied, only criticism can be low damping factor - little "boomines" through rear ported speakers, JBL4208.
As you can see, I`m not an audiophile, I even listen "lo-fi" recorded music...
I have "neverending" breadboarded 300B amp, tube rectification (CLC + LC for the driver), I constantly (but slowly) try different things. Right now it has a cascode 5687 driver...maybe I`d solder this mess together in the 2HE rack case one day... Two toroidal PTs, 2 Lundahl 3k OPTs, 4 chokes, Svetlana 300B tubes.
Well, to answer your question directly - for the good, but simple enough amp I`ll vote for PP, good quality OPT, say "Plitron" 6k:5Ohms. Individual bias pots for the each output tube (say EL34, 6550, KT66, etc.). Split load (concertina) phase splitter with E182CC, ECC99 or 5687 tube. Power supply with another "Plitron" toroid, SS rectification, CLC+ LC for the driver(say, Lundahl chokes),B+ about 390V, good quality passive parts. About 25W in UL or half of that in triode. No NFB loop, AC heaters (good enough, IME). As you can see, 90% from the Vanderveen`s book, but it works well. (Hehe, Pltiron/Amplimo even has a similar kit - no affiliation:-)).
That`s very subjective and YMMV, etc. To be continued...

Merry Christmas to everyone!

Monobloc picture - VDV3070 amp (V1.0) [message #30020 is a reply to message #30019] Thu, 23 December 2004 14:44 Go to previous messageGo to next message
Damir is currently offline  Damir
Messages: 1005
Registered: May 2009
Illuminati (2nd Degree)
Please, try the link:

Re: Monobloc picture - VDV3070 amp (V1.0) [message #30021 is a reply to message #30020] Thu, 23 December 2004 16:07 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18670
Registered: January 2001
Illuminati (33rd Degree)
That looks great!

I'm thinking that when we get around to doing a power amp project, it might be nice to have it be something like a parafeed SE amp. Not too complicated to build, good for a beginning DIY'er and nice sounding. Maybe a parafeed 300B?

Re: Favorite output circuit [message #30024 is a reply to message #30019] Thu, 23 December 2004 16:53 Go to previous messageGo to previous message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
Say Damir; I like the way you wired that amp with those little sub-assemblies to tag boards. Merry Xmas to you.

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