It's alive!!!
Haven't played music through it yet but did put a sine wave through it. One side looks slightly different than the other. Not sure it that can be heard.
The rails are +10.79 and -10.22. Nothing feels hot at all. Sine wave is very clean. With a 1.45Vac input I measure 1.39Vac on the output with the volume control at full up.
So far so good.
Haven't played music through it yet but did put a sine wave through it. One side looks slightly different than the other. Not sure it that can be heard.
The rails are +10.79 and -10.22. Nothing feels hot at all. Sine wave is very clean. With a 1.45Vac input I measure 1.39Vac on the output with the volume control at full up.
So far so good.
DUDE, I've been playing it now through my Leach Superamp for about a half hour or so. What a nice piece of gear. I have 4 other preamps, 5 counting the X-Bosoz I just about finished. This is hands down the best sounding of the bunch. Just wonderful. Vocals are beautiful. No nasty edges, just smooth. I can't wait to get this in a case so I can use properly.
Thanks to all those who made this available to the rest of us.
Blessings, Terry
Thanks to all those who made this available to the rest of us.
Blessings, Terry
Nice one Terry. Congrats. The sinewave diff can be due to the pot.
Run 100kHz squares too to make sure that the channels behave near enough time wise.
Run 100kHz squares too to make sure that the channels behave near enough time wise.
I try to get that hooked up again tomorrow. I can tell by looking at the sine wave that the timing is a little off. You can see that the wave over laps on the left but has a gap on the right. I never saw that before, that's why I posted the pic. What causes that and is it adjustable? I can't hear any problems. Maybe if I can find a recording with some lone rimshots. Right now it is just playing some beautiful music.
Two channels, fed with a y cord. weird little offset.
Thanks Gooch,
Really a pretty easy build. Took less than two weeks to get my Jfets from alweit. I still need to buy RCA plugs before I can complete a chassis.
I just hooked up and run a test for you.
This DCB1 on test has a 20K discrete resistors step pot.
Conditions: Pot turned fully up, I used coax test cables for the buffer loop, 100kHz square wave and sine wave signal from the 50 Ohm main gen output through the buffer. That is the yellow trace. The blue trace is the gen's sync output directly to the DSO. I suggest you do the same to make sure nothing goes phase funny in the Y split routing.
I kept the yellow trace lower in amplitude for visual clarity. Results look error free in the time domain. Same thing for both channels.
This DCB1 on test has a 20K discrete resistors step pot.
Conditions: Pot turned fully up, I used coax test cables for the buffer loop, 100kHz square wave and sine wave signal from the 50 Ohm main gen output through the buffer. That is the yellow trace. The blue trace is the gen's sync output directly to the DSO. I suggest you do the same to make sure nothing goes phase funny in the Y split routing.
I kept the yellow trace lower in amplitude for visual clarity. Results look error free in the time domain. Same thing for both channels.
Attachments
Yes I see that. Mine didn't look that way. Could have been cords I suppose. I had the Scope probes clipped directly to the output pins of the PCB plug. I didn't use a shielded cable on the input because they were only 3" wires. I'll try again tomorrow. Sure sounds great.
I just re-read your post. Some questions.
What is a buffer loop?
My sine wave generator only does sine wave or square wave, not both at the same time.
What is a DSO?
I can easily set it up to show generator on one channel and output on the other. I was trying to see how they compared to each other. Maybe having the generator hooked up to a Y cord cause some kind of feedback or something. I'll hook them up one at a time tomorrow.
If each buffer channel will show no time misplacement on your scope's input 1 VS the gen's sync output on scope's input 2 then there can be no time diff between the buffer channels themselves its the idea. The 100kHz square wave fidelity shown is great for an audio circuit nonetheless.
With buffer loop I meant the gen's main output going through the DCB1 and then to the scope.
Your gen's sync output does square wave time locked to its main output all the time. Check it out.
DSO=Digital Storage Oscilloscope
OK, I do it tomorrow. The screen shots in my earlier post was with a 1K sine wave. I'll use 100K next time if that works better for you.
Blessings, Terry
Blessings, Terry
100kHz is actually much tougher so I used it to highlight any possible issue easier. If your gen is at least 2MHZ capable, it should put out a fine 100kHz square.
Curiosity got the best of me so I went out and checked it. I don't know what I did before but I could not duplicate it. Now matter how I hooked it up, everything was dead on. One at a time, generator vs output, output vs output, Sine wave or square, not matter what, the waves lined up exactly. I obviously either had something hooked up weird or the unit just needed to burn in a little. Whatever, it is dead nuts now.
I don't understand the desire to "hot rod" this. It sounds absolutely lovely. Why make it run hotter? I'm leaving it right where it is.
Blessings, Terry
Oh, you are right, my generator does have a sinc output. However, I have no idea how to use it. 😀
I don't understand the desire to "hot rod" this. It sounds absolutely lovely. Why make it run hotter? I'm leaving it right where it is.
Blessings, Terry
Oh, you are right, my generator does have a sinc output. However, I have no idea how to use it. 😀
The aging Tek 475 could be a settling factor too. Testing always takes verification when funny stuff appears. All well then. 
What circuits are your other preamps?
What circuits are your other preamps?
Bryston .4B, Dynaco PAS 3, Sony EP9ES, Yamaha C85, and X-Bosoz, thought to be fair, the X-BosoZ is not completed yet.
Hey, I resemble that remark. 😉
Hey, I resemble that remark. 😉
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Still, we do calibrate from time to time through check ups etc. The venerable workhorse scope may has some highish ESR caps inside by now, couple of trimmers could need a bit of tweaking, who knows.
Quite a collection of preamp gear. Nice.