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Messages - jfetter

Preamps and Effects / Re: dspic-codec
April 09, 2020, 03:30:16 PM
My last entry on this thread was 2011. 
So and update is in order. I retired ( if that even exists) in 2015 and although love the signal processors, have gone all analog target designs.
My 100% push since 2016 has been low voltage tube-ss hybrids.
I generally use the tube in fb loop with op-amp and have learned a lot along the way.
Pentodes and triodes work just fine at 30v potential (+-15VDC). No positive grid drive is used.
My test equipment is upgraded now with Motu M4 for spectra analysis. New scope and linear bench power supplies too.
For power amp I use the tpa3118 almost 100%.

Maybe one day re-visit the dspic32 but having too much fun all analog.

Hot on to do list is re-visit Germanium. Maybe an all discrete tube-Germanium hybrid will materialize.

Same hybrid ckt but high level out.
This is a harmonic profile pics of a triode single-ended.
I'm not aware of any solid state component that can do this across wide range of output levels.
The circuit is a 6sn7 / ne5532 hybrid.

Tubes and Hybrids / Re: Hybrid valve and TPA311x
September 13, 2019, 03:29:50 PM
A reliable pcb pot (ie Beckman ) cost quite a lot. So I put a servo-buffer opamp and configured as a ' super triode' . It took a long time to get it right...
This plot is using a sa5532 with 6sn7 in feedback loop.

It's raw right now in fact going to a lower gain tube but the plot shows 1khz signal , 2 khz dominant harmonic , 4th etc.
Third and fifth very low.

Tubes and Hybrids / Hybrid valve and TPA311x
November 15, 2018, 07:52:42 PM
Two years have tested others and this one sounds the best.
I built it point to point but now doing a board.
The tone tilt I think beats all others. Shown here in hifi mode but easy to add scoop.
Uses 12AU7 and $3.00 D class module.

Schematic attached. The fx loop is not fully tested.

Schematics and Layouts / More hybrid madness
September 21, 2017, 03:31:53 PM
Threw this together, its still on proto board and running tests. I'm crazy about fets and tubes together.

Jury is still out on this one, have to play it through my system.

Tubes and Hybrids / Re: Noisy pots
July 10, 2017, 05:26:21 PM
maybe leave plate resistor alone and put a single Germaniun diode frm tube cathode to ground, no capacitor.. then solder a 1M resistor across the 4.7M 'grid leak' resistor.

that amp's control panel graphics are a beautiful period example.

it sounds just peachey. all day yesterday in hi-fi mode with r&b and blues. The stereo summer was too low for CD outputs but worked fine with dragonfly. changed from 680 to 2.2k.

you wont have much headroom using a single jfet front end. if using with the Sz pair then lots of headroom. guitar needs 5v PP input range without clipping. i would do the tube/fet front end.

the bias pot allows setting harmonic content to max 2nd, max 3rd or a mix. For hi-fi max 2nd or simply lowest THD.
Opps this is the jfet-mos front end. The above zip is tube-p-mos.

Working on a new one now with some improvements, ie compressor so D amp never approaches clip.

As-built zip attached.

Tubes and Hybrids / Re: My Hyrid Tube / TDA2050 amp
June 30, 2017, 03:57:13 PM
:dbtu: :tu:
Tubes and Hybrids / Re: NAD!
June 30, 2017, 03:52:25 PM
Quote from: J M Fahey on June 02, 2017, 07:46:12 AM
Quote from: galaxiex on May 31, 2017, 09:19:28 PM
Thought I'd put this here since its a tube amp.  :)
What makes you think that?  :o
Last time I checked, site name said "SS"  :o

its kinda funny, i've put up a lot of diy data on hybrids on another site and it gets no love , even the students get upset. if i put test plots and schematics in SS they cry, then if i put in Tube section they cry. Its hybrid and homeless. Nice to see a hybrid section here.

congrats on your amp find.
The reverb looks like is using internal memory on a dspic.
Thanks for putting it up here. Nice to study other work.
Amplifier Discussion / Re: Class A solid state
April 19, 2016, 06:22:57 AM
i just finished the pre for you.
mounting in a test chassis now.

here is a link on other forum to it.

i like the amp you show. any fft etc available?
but i bite the bullet and go to symetrical power.

Amplifier Discussion / Re: Class A solid state
April 17, 2016, 08:30:04 PM
I had in mind something like the JLH circuit i.e. single ended with active loading.