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1970s Design Indulgence
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RichW View Drop Down
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Joined: 21 Jan 2013
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Points: 1471 		Post Options Post Options   Thanks (0) Thanks(0)   Quote RichW Quote  Post ReplyReply Direct Link To This Post Posted: 18 Jan 2024 at 10:34am
Hi Jon,

A loan of the 7eventy would be great - can I get in touch in a few weeks?
Thanks.
Majestic/Enigma, Accession MM & MC.
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dave View Drop Down
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Points: 3 		Post Options Post Options   Thanks (0) Thanks(0)   Quote dave Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jan 2024 at 12:36pm
Originally posted by Graham Slee Graham Slee wrote:

In all unregulated single supply transistor power amplifier circuits, the output's DC level is bound to change gradually with load. Now, where have I heard that before? I haven't!

Why didn't JLH say it? Did Self say it and I didn't understand? All they ever said was the output capacitor caused distortion, as well as saying class-B causes distortion.

JLH did say that it appears that there's more bass when a regulated power supply is used, but without explanation.

All I did was put a DVM between the OP stage DC and ground, and swept the signal amplitude up and down, and noticed how the DC changed with the droop on the HT (due to load).

And all I've done (with Bruce's measure thrice to the power of lots - to cut once) is to stop that happening by giving the voltage stage a regulator.

But I do understand they didn't have TL783's in the 60's or 70's, after which amplifier design had moved on anyway. And here it only just fits the required voltages. And you do have to fully grasp what a bootstrap does (negative current on positive swings).

It hasn't broke yet after being on for 24 hours, so I hope it has dealt with the unmeasurable distortion my ears were complaining of.


humour me several years out of time.... This is very exciting, and a personal preoccupation of mine. don't like seeing cones flapping around, and I have unstable mains in my house to add to the joy. It gets everywhere, so I try and regulate / stabilise input / driver stages in my tube amps when ever I can. 

Must read on to see how it sounds. The suspense :)
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Fatmangolf View Drop Down
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Joined: 23 Dec 2009
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Points: 9695 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jan 2024 at 1:44pm
Originally posted by RichW RichW wrote:

Hi Jon,

A loan of the 7eventy would be great - can I get in touch in a few weeks?
Thanks.



That works for me Richard.
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Fatmangolf View Drop Down
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Joined: 23 Dec 2009
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Points: 9695 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 25 Nov 2024 at 8:17am
I have the 7eventy amp boxed up and ready for someone else to try. Please PM me if you would like to borrow it next.
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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