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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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PostPosted: 10 Dec 2018, 04:24 
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Joined: 23 Feb 2017, 02:02
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This is the 4 stage op amp from ages ago but with latest output stage and photos are from septebmer 16.
Very low distortion by fixing some plorbems the emitter and collector resistorless output stage had intially.
Photos are into 8R load and has supply voltage of regulated +-8.5v.

The open loop response has some oscillations but had been fixed by isolating the op amp from OPS with small resistor then we killed the overshoot by externally compensating on feedback resistor.

Not supprised that the sound quality gain was quite small. listening results confirms with theroticall results where the orignal hf distortion visible at 24khz is not auditable due to it being way past 20khz auditable range and speaker can't output 20khz higher.


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PostPosted: 10 Dec 2018, 05:19 
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Joined: 26 Dec 2016, 03:46
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Location: Bayarea
How about large signal like 30V?


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PostPosted: 10 Dec 2018, 16:59 
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Joined: 23 Feb 2017, 02:02
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Its a head amp with +-8.5v but you and I will know fairly soon after I do some more research to perfect my 4 stage then research into hybrid with 4 valves for 4 stage then build a power amp for it.


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PostPosted: 10 Dec 2018, 19:33 
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Joined: 26 Dec 2016, 03:46
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Location: Bayarea
Large signal is the key, that's where all the problem starts. OPS is the one that cause all the headache, the front end is easy.


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PostPosted: 10 Dec 2018, 20:14 
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Joined: 23 Feb 2017, 02:02
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I can easily dump in a conventional ops and expect flying perfomance with such open loop gain theres no stopping me from getting top perfomance


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PostPosted: 10 Dec 2018, 20:28 
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Joined: 26 Dec 2016, 03:46
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Location: Bayarea
Try it. You'll see.


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PostPosted: 11 Dec 2018, 00:26 
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Joined: 23 Feb 2017, 02:02
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+-24v emitter collector resistorless power amp worked perfectly, this makes me feel very confidant that it will also work perfectly with +-36v which is my project after I upgrade my op amp for +-24v class a amp


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PostPosted: 08 Jan 2019, 02:23 
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Joined: 23 Feb 2017, 02:02
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I got this one done on 28th, took me a long time made two testing boards and at first dosen't like the idea of having 3 vaccum tube gain stages out of 4 with +-12v.
Then the second one nulled the plorbems and got it going.
A stereo uses allot of transitors 58 pices excluding output transitors

Sounds very much like valve only amp but with extreme low distortion and you can hear all the diffrences from changing valves.

I got forced to use geniune only transitors cause that was causing my pre amp to blow. Fako has unstable capcitances and transition frequency causing the amp to fall into oscillations ocasionally and eventually die. I swapped all geniune and never had a oscillation.


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Last edited by ILoveHiFi on 08 Jan 2019, 02:56, edited 1 time in total.

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PostPosted: 08 Jan 2019, 02:49 
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Joined: 23 Feb 2017, 02:02
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I've hit 3 birds with one stone, making the super hybrid 4 stage forced me to dig deep.
Fine tuning the 4 stage op amp to maximize open loop voltage gain, about 20-40db increase in openl loop gain.
Corrects all errors in 5 stage op amp and got it working this one has about 40-50db more gain than improved 4 stages.

The 5 stage op amp shows very high speed and high gain low distortion very awesome, about 50v/us with closed loop gain of 3.1.
Can be 70-100v/uS if I increase the closed loop gain.

I thought I never was gonna be able to make the 5 stage work so I decided to upgrade everything to 4 stages.
Don't have much time left so I'm gonna leave the +-36v class a amp alone for now. Theres zero point in me buildling it if it cannot rock my wolrd at least once a day near clipping volumes.
Due to parrents renting out the other half of the house.

The +-12v 4 stage hybrid is v awesome with bias of about 0.38A yeilds heat sink at 70c at 25c ambient. gets you 6.5W Class B


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PostPosted: 08 Jan 2019, 03:10 
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Joined: 23 Feb 2017, 02:02
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To be sure I'm not cheating with the voltages I uploaded a few more pics, duall mono construction.
The SMPS cost 0.4USD each geniune 2A 12V directly from China


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