Home » Audio » Thermionic Emissions » Super simple linestage.
Super simple linestage. [message #9136] Sun, 31 July 2005 17:35 Go to next message
Thrint is currently offline  Thrint
Messages: 43
Registered: May 2009
Baron
For those who don't need any additional gain I ahve an idea. It is even all SS, though the development model is completely valve.

One needs a high gm, low input capacitance device to act like a cathode follower. Some pentodes work quite well, but a pair of DN2540 mosfets rigged in cascode as in the Guinevere plate loads is even better. No set resistor is needed.

Have this device ride on a goooood CCS. Again the Guinevere plate loads will do well, and this time we *WILL* build the complete thing. Set it to sink 10 mA.

Attach the volum pot's wiper to the lower gate, and cap couple from its source( as in Guinevere ).

Supply a +/- 60V set of rails and we're off...low output Z, wideband response, and no silly high voltage capacitors needed.

For parts, a 120V CT power TX, two 10 Hy/100 mA chokes and two good capacitors are all that's required. Figure $100 max if you don't want a gold-plated box...
regards,
Douglas

Re: Super simple linestage. [message #9137 is a reply to message #9136] Sun, 31 July 2005 21:27 Go to previous messageGo to next message
colinhester is currently offline  colinhester
Messages: 1349
Registered: May 2009
Location: NE Arkansas
Illuminati (3rd Degree)
Please O' Great One, tell us more. I should be finishing my current project in a month or so and would like to have something else lined up. Wayne suggested doing an amp based on 12V space-charge tubes (any thoughts), but if there is interest in a linestage, I'm in....Colin

Re: Super simple linestage. [message #9138 is a reply to message #9136] Mon, 01 August 2005 13:42 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
So why is it we would want to build this unit? If you don't want gain why not just run a pot?

Re: Super simple linestage. [message #9139 is a reply to message #9138] Mon, 01 August 2005 18:11 Go to previous messageGo to next message
Thrint is currently offline  Thrint
Messages: 43
Registered: May 2009
Baron
I did not say that anybody wanted to build this unit. Or that there were no other ways to achieve the results. It is just another way of doing things.

If you're sugesting a simple voltage divider pot, the pot and buffer I just laid out ought to run circles around it.

Since I have a feeling that there is substantial prejudice against SS stuff, I thought to show a way it could be used to good effect. Always use the best design to solve the problem. Sometimes it might just be a SS one. FWIW, I don't recall anybody complaining about the performance Guenivere delivered.
regards,
Douglas

The suggested PS of 60-0-60 would yeild ~50 volts at the L-C filters.

Re: Super simple linestage. [message #9140 is a reply to message #9139] Tue, 02 August 2005 03:33 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
I understand but it seems such a radical change of direction that curiosity prevailed hence the question. I agree; whatever does the job.
Just that you always seemed to favor and design around tubes so the question becomes what precipitates this new direction.
Was there some experimentation that caused you to find this worth pursueing?

Re: Super simple linestage. [message #9141 is a reply to message #9140] Tue, 02 August 2005 04:58 Go to previous messageGo to next message
Thrint is currently offline  Thrint
Messages: 43
Registered: May 2009
Baron
I built a similar circuit with tubes, and found it complex to implement. Lots of B+, lots of tubes....

I have most of the parts, and need a proper sized box. I will probably try a remote PS and see how that experiment goes. I have a bunch of photo flash caps salvaged from disposable cameras which have done well in audio circuits to try( they're small 330VDC/160 uF ). It is interesting enough, being completely SS to try IMO.

There is a certain satisfaction to be gained in favourably comparing to something far more expensive and Off-the-Rack, no?
regards,
Douglas

Re: Super simple linestage. [message #9142 is a reply to message #9141] Tue, 02 August 2005 08:19 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
Yes; without a doubt. I have a phono stage built with photo flash caps. Cheap and they sound good.
I believe you can never know enough about any hobby; so try everything.

Re: Super simple linestage. [message #9143 is a reply to message #9136] Wed, 03 August 2005 00:34 Go to previous messageGo to next message
metasonix is currently offline  metasonix
Messages: 103
Registered: May 2009
Viscount
I'd like to see this implemented, tubes or no tubes.

Nice Spam. Didn't you nitice this is a TUBES forum? (nt) [message #9145 is a reply to message #9136] Thu, 04 August 2005 14:13 Go to previous messageGo to next message
Rek_O_Kut is currently offline  Rek_O_Kut
Messages: 4
Registered: May 2009
Esquire
asdf

Re: Nice Spam. Didn't you nitice this is a TUBES forum? (nt) [message #9146 is a reply to message #9145] Thu, 04 August 2005 14:28 Go to previous messageGo to previous message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
Spam?? You mean potted meat?

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