What's wrong with the kiss, boy?

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After more careful inspection - the 30AWG +CCW wire from the pot to the board had completely sacrificed itself also. That makes sense since tracing back through the schematic this goes to positive side and to GND.

Sad... since the lovely tiny JFETs are right there in the circuit, but since the pot touched back (pin 2) of M3 - it is starting to make sense.

I will replace obvious and suspicious parts in shunty and move forward hoping the precious JFETs are okay.

Any other advice is always greatly appreciated. I have a challenge with the schematic and circuit traces trying to ensure proper troubleshooting plan.

:cheers:
 
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LOL!

Well... today was my day... then it wasn't. Boy am I a dodo. I've now fried the PSU section for the relays on this board. R1 and R3 up in smoke. I was a complete dodo and unplugged my soldering iron instead of the pre-amp. As I was re-assembling the unit - I brushed the body of the pot up against the back side of M3.

I have to put it aside for today ... too much for my heart to take. I had it 100% working... then I killed the recovering patient.

I have to laugh. I learn as I goof... so there's that.

:cheers:

I dropped a tiny screw driver and it touched the relay power supply. The tiny cap made a small pop and the outside cover flew off. The caps leads were still soldered on, but cap was reduced to small cotton ball.

Have you had a chance to pair Iron Pre with BA3? That's a really nice pair. Just rotated BA-3 back into set up with Iron Pre. Very nice.

Russellc
 
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I have made every attempt possible to goof this project up...

Shorted V+ / V- for the PSU for the relays on one board while testing the relays.
Had a bad (99% sure) diode in the relay section that caused inputs 2 and 3 to activate together on the other board. That took two days for me to diagnose... But I did finally figure it out.
Now this... LOL!

As my Dad would say, "That's why you can't have nice things". :rofl:

re: Iron Pre and BA-3 - YES! :D Did it with the SE Iron Pre that I still have on cardboard. That's what inspired me to try doing the BA3 balanced monoblocks and the Iron Pre Balanced together. If I can ever get it done... :D :D :D :D :D
 
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Well, I started with a fresh and calm brain this morning.

I measured every semi while also trying to learn a bit more about how the circuit functions. I compared all measurements to the known-working-good board. After feeling confident I had replaced all dodo parts... I moved on.

I used dim bulb (I need some smaller wattage bulbs... maybe candle bulbs) and a Variac to very slowly bring it up. The 29W bulb limited it a little bit, but I was able to get it close enough to feel comfortable removing the dim bulb. It didn't show a dead short... so...

Slowly (about a 10 min process) ramped up Variac in 5V or so increments until I got a steady 36VAC at the board. I measured the V+ and V- along the way and did a nose and visual / touch check for hot parts or smoke until I got to the final 36VAC.

I think success! :D :D :D

Lovely +15V00 and -15V00 rails. I did a quick check of the offset again to verify. It was a few mV, so I zeroed it to 0.00mV per the DMM. It is rock steady on both phases. I have it on the bench warming for an hour or so to check for stability and in case I've done anything else silly. I'll tweak offset and bias after it's warm.

ZM... Maybe I should just make "Planky Junior". Every time I try to put this wonderful project in a chassis, I goof it up. Maybe it was meant to roam free and wild and can't be in a "cage". :D :D

I also noticed that I never put in a proper wire for the chassis GND for the boards. So, I have added that. DOH!

Once again, thanks to everyone for the support. I always learn quite a bit when I goof something up... but it doesn't make it any more fun.

:cheers:
 
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so, IAIMH, when we can expect listening impressions?

RussellC - :rofl: :rofl: :rofl: :rofl: I love it!

ZM - I have it all buttoned up with all bolts for chassis all tight except top on the bench now for final bias and offset cook with chassis. So... probably one to two hours. Now, I need the BA-3 monoblocks for a balanced amp. Right now, I just have the BA-3 and the Babel J2. Those are for Sissies :D

Thank You! :worship: :cheers:
 
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RussellC - :rofl: :rofl: :rofl: :rofl: I love it!

ZM - I have it all buttoned up with all bolts for chassis all tight except top on the bench now for final bias and offset cook with chassis. So... probably one to two hours. Now, I need the BA-3 monoblocks for a balanced amp. Right now, I just have the BA-3 and the Babel J2. Those are for Sissies :D

Thank You! :worship: :cheers:

feed Babel J2 balanced
 
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Well - It's in the system :D

I was a huge scaredy cat. So, I checked... rechecked... checked again... Then I checked all inputs and that the "Bal to SE" was working.

I had to repair and put some strain relief (just little bends) on a few of the 30 AWG itsy bitsy wires, but no worries.

All good!

Then, because I am crazy, I took the bottom off and put some rubber in place so there is no chance that the toroid bolts can touch the bottom. I'm still never 100% re: shorted turn, but I feel like some thick rubber from an old toroid mount and some proper adhesive is a safety check I can do for peace of mind. Then, it took me far too long to get the pots aligned and the way I wanted them for a smooth turn.

Here are some pics of it in the rack and topless with the BA-3.

ZM, the Babel J2 is literally sitting right next to the BA-3. So, I will definitely get it warmed up and try balanced in. I have it wired properly already for that. :D

First song was "Once In a Lifetime". I thought that was appropriate.

I'll post some more thoughts re: sound tomorrow - but, first impressions are just like when it was on the cardboard. Totally transparent. That's why I wanted it in a proper chassis to use in the system so badly. It is incredible.

The only thing I think may have changed... and I don't know why... the top end seems a bit more revealing and the soundstage is monstrous. Although... with all the pain I caused this poor baby... I know my brain is going to make it sound good. :rofl:

As always... thank you to the Mighty ZM! :worship: :cheers:

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LOVE IT :D

I got up early this morning to do some listening. The house is quiet, and generally, I listen to music at ~65 to 67dB at my seat. So, it was a great time.

I listened to a ton (3+ hours) of music with the pre and never wanted to skip songs, which is a great sign. I also did the same thing I did prior. I removed the pre-amp from the chain and ran the DAC straight to the source. I still think this is one of the most transparent pre-amps I've used.

Why do I say that? With the Iron Pre Balanced in the chain, I hear things almost identically if not maybe even a slight bit better. What could be better? To my ears, I get a bit more "air" in the soundstage along with some added space left and right. Depth seems the same. There may also be a slight clarity on the top end / cymbals … light background tambourines etc.

However, it is very challenging to ensure a proper level-match at low volume for me. I used a phone app and then my new mic from MiniDSP and REW to balance out the channels and levels, but...

So, what’s better than just running the source to the amp? I have to use digital attenuation (albeit, I think it's very good) when running the DAC to the amp, since I don't just have a passive attenuator laying around. Also, from what I've read, a pot and its properties can be very important to SQ. In addition, I occasionally will use alternate sources like directly from a computer, TV, and I may throw in some actual physical media like a CD on occasion :eek: Switching is nice :D

So, what’d I do for listening? Listing tracks again seems boring.
Usually the first thing I do is see how the music makes me feel. Am I tapping my toes; does anything give me goosebumps; do I shed a tear; do I want to accompany the band with some drums or air guitar; am I singing along; etc.?

Conversely, do I ever wrinkle up my nose or do the “RCA Dog” look? Is anything “obvious” missing? Am I constantly moving to the next track?

My audio memory is for crap, and I’m always finding new little things that I hear in some song or another, so I never focus too much on “detail”.

tl;dr – I knew I wanted to get this project into a proper chassis and keep it in the system from when I had it on cardboard. It’s a phenomenal pre-amp. The only thing I think may have changed a wee bit from cardboard is (from my lousy audio memory) that I think the soundstage and detail in the treble has improved. Why… I dunno? Proper grounding, itsy bitsy / proper length I/O wires…. ??? Either way, one would think that adding something to the chain would take something away or “color the sound”. I don’t think so at all.

Not that my recommendations bear any weight, but really… I recommend building this or its almost literal ½ brother the Iron Pre SE. I can’t imagine anyone not loving it.

Listening with Babel J2 using balanced inputs will come later. :D
 
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:clown:

so, you had just a sniff of Real McKay...... still having damn resistive attenuators in chain,even if nice amount of Iron Magic is veeery helpful :devilr:

when using Iron Pre (Bal) as SE In- SE Out , sound is pretty much the same as with Iron Pre SE, with two slight differences:

- Bal iteration is having each buffer driving just one of 4 identical windings in xformer (while SE is having buffer driving two windings in series, when 6db gain is set, one winding when 12db gain is set),

- and - so-so important difference - in case of SE - channel buffers are isolated "just" with cap multipliers (fed from common Good Gemini reg) while in case of Balanced - each channel is having own separate Good Gemini reg

huh, I sorta complicated it above, but lazy to go back and untie it :rofl:
 
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:rofl:

I think I understand. I seem to like the "increase" in iron. I loved Iron Pre SE. Iron Pre Bal is staying in the system. The gemini shunty and the output are remarkably stable. Rails have not moved from 15V00 for all 4 phases even with small fluctuations in mains. The offset is stable within a 10th of a mV with changes in temp.

I'm really looking forward to trying with Babel J2. Fully balanced chain from DAC through input stage of amp.

Re: getting rid of resistive attenuators... It will come some day for me. :D I think I said sometime earlier in the thread that a Black Sabbath song came to mind.... Iron Man. :joker:
 
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last time at SR, I did saw but practically in leaving time - Papa's B1X - Ubercute looking preamp , with biiiig MoBo, few parts inside, but two proud standing Cinemags in a middle

there was some talk about it in last year or so, and I remember nudging Pa to make something as that at least year before that; he said something about not being overly interesting as commercial piece and , there it is - in flesh :clown: (Variac boy getting that one as personal gift is example of being a right guy in right place in right quark of time)

I know that Pa is ....... well - Pa , which means - his sense and level of engineering practicality** is hard to both achieve and compete with, sorta; one of thing giving me a leverage to differ is my insistence on Shunt Regs (at least for sissy loads), strongly believing that it simply sounds better that way :)

**each of Papa's is having one (or even more) important quirks, as main rational reason for existence, while rest of construction is on strictly industrial "good enough for task" level of performance; examples :

-M2 - old trick of xformer gain, combined with Uberfunny biasing mechanismus; for my eyes/brain/aspirations - still stays as etalon of elegance and 42

- F3 - LU JFet, made to work

-F7 - small glass covered box broken for trick of Yore

etc. ...... as I said - each of them having own quirk , each alone worthy of Constructor's Inducement in R'n'R Hall of Fame

so, me being Pa in Attempt :rofl: , I have at least one qiurk, if not exactly my own , at least I'm stubborn with it - wherever you see a hole, plant a Shunt Reg :clown:
 
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