What has been your costliest mistake in this hobby?

For example :I recently learned a hard lesson- I accidentally ran voltage thru my $3000 MC cartridge (kiseki purple heart).  I have a TT with 5 prong connector and a phono cable with a 5 prong connector.  I accidentally swapped where they plugged into and ran electric thru the tonearm into the cartridge.  It was a stupid - not thinking- hasty mistake. When I corrected the problem the cartridge was fried.  An avalanche of four letter words followed!

So what has been your biggest and/or costliest mistake?
Cable drop, I added a whole new, meaning to four letter words..
I'm still fixing stuff. A single 300 deluxe VTL, a GG MC275, and two months after that I lost a channel (same side as the cable drop) on my C2500. 

Cost to replace off the shelf, 12K plus. Cost to repair, A LOT of time and money over 2,000.00 in parts alone. TWO transformers, not a single blown fuse, only at the main, THE MAIN. It popped a 20 amp breaker, but not a 5 amp fuse, on the surge protector, amps or preamp...

I must have looked like the Abominable Snowman, after he got his teeth pulled... Yup that was me.

Now I call PG&E and have them shut down WHOLE grid, when I work on my stuff.

Yup, you can blame me, for no power this summer, not the fires.
Doing a cable swap, "Shut down the grid" oldhvymec is at it again. ;-)

Not costly, but I just fixed a big disaster.

I was photographing equipment, put the leaves in the dining room table, put my 45 lb Cayin tube amp near one end of the table, out of sight while I was shooting my McIntosh tube preamp, closer to the other end of the table.

I went to turn the preamp around, to shoot the rear jacks, and, when I lifted it up, the weight gone, the table tipped over. I ’dropped’ the lighter preamp close to the floor, and ran to save the amp, saving neither. Cayin, like a cat, flipped over and the majority of the impact was to the upside down massive transformers. Big gash in wood floor from corner of the faceplate (thick, undamaged happily). Two snapped off power tubes, OMG, glass hither and thither. Two large tube sockets now ’loose’. That’s it, that Cayin is built like a brick ship house. Soon one of the 6sl7 internal damage caused it to fail.

Had spare 6550’s, but time to try some KT88’s I wanted to try anyway. Had spare used 6sl7, different brand, so changed the 2 6sl7’s to something that looked different than the 2 adjacent 6sn7’s (I mixed them up once). 

Preamp glass face cracked, that’s it.

McIntosh no help with mx110z glass, too old, found one company with replacement glass, $90. wait for it, or, what I did, order glass locally, $45. mask it and paint the back of the glass black like OEM. Whew.

Strong ceramic tube sockets of Cayin, but, the right channel tubes were a bit loose, occasionally I needed to tap them a speck on turn on to eliminate static, get full signal. I figured I would have Steve at VAS (Cayin USA rep) replace the tube sockets soon.

Yesterday I took it apart, from the top, using a tiny screwdriver I pried the contacts of each pin hole closer together. Then, from the bottom, a few pin connectors still wobbly, I inserted short lengths of small diameter copper wire to wedge those few snugly. Tubes very tight now.

Problem gone cost $45. I’ll meet Steve another day.

Got lucky once more.
STEALTH cables sold them all they have no resale value in the USA STAY AWAY overpriced 0 resale.
Paying too high of a price for a pair of Quad 57's and then, years later, having to sell them at a loss! The smart thing would have been to just keep them! But I needed some fast cash!
I'm going to exclude buying stuff that I ended up not liking, because purchases of audio gear are always experiments.  So the stupidest thing I did was trying to disassemble a ribbon tweeter trying to see if I could upgrade the wiring to and from the tweeter.  Destroyed the ribbon in the process of disassembling. 
I thought it would be fun to hook up a keyboard to my system and play some music. Due to a handling accident, I accidentally sent a 12V signal to my amplifier which proceeded to amplify that to what I calculate was over 140 volts with a fair amount of DC included. Needless to say, the speakers didn’t like it and refused to play again. The silver lining is that I replaced them with a pair of DIY speakers that I never enjoyed, but then learned of a design error I made and now they are my favorite speakers I’ve ever owned. Much better than the pair I blew. I never would have figured it out had I not blown the other pair. 
Reading reviews like if all pro-reviewers know what they talk about....This take me to bad choices...

After that i read simultaneously all non- pro- reviews and not only the pro-one about a product and succeed to buy my actual audio system and i dont look back anymore...Studying non professional reviewers and professional reviewers about a product is mandatory...

The costlier mistakes in this hobby is the universal consensus around the word "upgrade" and the sheeping crowd march toward frustration and the money pit, except for those who can afford the "illusion" given by an "upgrade" to the top of the line product...This is a myth, this is nor true nor false, this is an half truth....Worst than a lie....

The truth is ANY good audio system, not necessarily costlier, to attain his peak, to reach his optimal workings, must be rightfully embedded simultaneously in the mechanical resonant dimension, in the electrical grid and in the acoustical space....

The higher price of electronic components are testimony of their design quality yes, but created the illusion that all electronic design component is perfect to use ready out of the box and will give the better of itself without any other work by us.... This is false...This is a mandatory marketing lie....Nobody can sell a 10,000 amplifier saying that after buying it the job begins and some other works are needed from us.... 

Who will buy a problem instead of a solution?   :)

The price does not give you the audiophile experiences by itself, the rightful triple embeddings controls work will, at almost any relatively low price if you are creative....

That is a really good question!

I’ve been fortunate. No bad choices, just some that might have been better in hindsight had I been better educated at the time. Biggest lesson learned over time is perhaps to always do your homework regarding what things are most likely to work well together and be diligent to manage the financial risk associated with trying costly new items. Avoid snap decisions based on limited information.

buying a cool used piece that no one could fix when it failed (carver passive preamp)

very expensive cables
My only costly mishap was about 30 years ago when my dbx dynamic range expander took out a woofer in my JBL L96
Guess I had too much bass boost. 
I've rewired my room, whole panels, component mods, all kinds of stuff going back to building a Dynaco ST200 in high school. Trying hard to think, there must have been something accidentally dropped, or scratched, or burned out somewhere along the line. Sorry, but I'm drawing a blank.  
There was a made in China Jungson amp that turned out to be a total piece of defective crap, two reps from China even came out to see first hand the noises it made, lied to my face and then refused to honor their warranty. But my dealer stepped up so even the royal mistake of buying made in China didn't cost me anything but grief and frustration. 

Honestly the one bonehead mistake I made was putting a 0.8A Orange Fuse in the Melody. The value on the factory fuse was barely legible, so that was a factor, but how in the world was I so out of it as to think a 50WPC amp can run on less than one amp? Dope. So it blew. Instantly.  

Then of course I realized what happened. Told the dealer. And surprise, they replaced it anyway. So sorry, no sad stories here. Just happy endings: Buy American. Buy Synergistic. And they lived happily ever after.
I always shut down to change a rig. Biggest mistake was putting an opamp into EE DAC wrong orientation.  Not a major dollar crisis. I triple check all connections,  so no kabooms.

Dealt with two liars over the years, an that cost me a few hundred. 
The only big very big mistake i made in buying something, was after reading universal appraisal reviews of a very well known amplifier....I will not name the designer company... They dont deserve my wrath, aome reviewer does perhaps, but even them only win their life and bread then.... I am the only culprit to beat....

The amplifier was so bad that me and my friend were flabbergasted and laughing after one minute listening.... It was a perfectly working unit, i sold it immediately and easily few hours later....

Any piece of trash will be the heaven of some crowd.... :)

I was at this times looking frantically for "upgrade" for my unsatisfied audio system...I have not understood how to improve any audio system at this time.... But sometimes we must change the amplifier we have because it is a limitation.... I am not against upgrading , i am against ignorance disguised in "upgrading costume"...


Sorry i will never reveal the name of this universally loved piece of amplifier....
Foolishly bought a pair of speakers and:

1.  Didn't negotiate hard enough and paid $2K more than I should have
2.  Listened to the dealer when they said it would work in my room

I naively assumed that a dealer would actively try and solve my problem rather than just sell me anything they could.  The dealer (who shall remain unnamed as they are noteworthy) had zero interest in making sure I had a good solution for me, just moving a unit.  There are other dealers who are great and I have vowed not to be that guy in my own business, but it is quite frustrating when it happens.    

Fortunately, I found The Music Room and I was able to execute a trade for a DAC and the whole thing only cost me $500 rather than $2500 which is the loss I would have taken selling them.  
My biggest and most costly mistake was selling a Krell KPS20i cd player, that I owned and loved for many years. But after 20 years I assumed digital should have advanced enough to merit an upgrade. In the last 5 years various supposedly more 'advanced' cd players from brands like Metronome and Esoteric came and went. None of them delivered the sonic improvements I had expected.  

So after about $7500 worth of buying and reselling different players I finally accepted my mistake and decided to simply buy back the 20i. Back to the future. As chance would have it, the 'new' one is only one serial number removed from the one I previously had.......

It goes to show that technological progress, which is undeniable in digital, does not necessarily result in better sound. In fact the same applies to the discs themselves: most higher bit remasters don't sound any better than the first cd issues. 

Buying a sub (Miller & Kriesel) without knowing how difficult getting it to work right would be.  This wasn't that big of a cost in absolute terms, but I was a  young audiophile and everything seemed expensive, but that it derailed my listening experience.

I should have focused on the mid-treble, imaging and natural tonal balance over trying to get a 20 Hz response.
i made the same mistake exactly with the same sub (Miller and Kreisel) :)

I draw the same exact conclusion....

After that i embark in my intense experiments in listenings 2 years ago....


I never use the sub more than an hour and is here always.... I was too lazy to put it for sale i think....I will never need a sub, neither four one....  :)    
Probably not in keeping with the general path of this thread but: buying any stereo gear new. 

Thanks for listening.
@brownsfan ,

I used to swap spade connectors for soldered ones but on one occasion the heat from the gun melted/burnt out its voice coil wire.

Why oh why can't all companies, at the very least, just use non tarnishing spades and connectors for their drivers?

Seriously, how much are they saving on connectors which will look pitted a few years down the line?

I somehow got what was left resoldered and working but it was an unhappy experience.

As was my decade long foray into the bottomless-moneypit Linn/Naim nexus... 
@cd318, indeed!  I will never understand the thinking behind parts selection on speakers.   It seems that I do not understand the underlying economics.  On the other hand, it also seems that a few of the direct to customer guys are beginning to run in a different mode.  If I knew a bit more, I'd be inclined to try building my own.   
Going through loads of mid-fi equipment in the vain hope to find, by sheer ’magic’, some satisfying sound quality. Didn’t.

’Außer Spesen, nichts gewesen’...

Maybe the learning exercise was of *some* value.
The sound quality was just NOT getting there until very many years later.

Good sound doesn’t come easy - and not quite at bargain prices either. 😕
Be surprised if YMMV.
M. 🇿🇦
PS: oh dear, and one more nasty learning exercise.
When I connected my ML39 CDP, used as a pre-amp, to the digital satellite TV decoder.
One lightning strike, - the connected coax cable screen/ground must have gone sky-high, some 10k Volt for a split second and fried the Levison no.39.
One stinker of a repair bill. 

Some years later, I had a connection, to my ML36 DAC, from my DVD player, to my TV, to my Decoder -
and from there, wiress to the good Lords lighting.
Boom, - decoder, TV, not the DVD?!?, but the DAC nailed.
So, so sad, eish! 😭

Taking advantage of a trade-in and trade-up deal offered by a shop. I ended up not liking the bigger speakers nearly as much as the smaller ones.

Also, at a different time, not biting the bullet and buying some fairly costly speakers that I really liked but wasn't sure I could afford.  Not doing that led me on a years-long quest for satisfying speakers that eventually ended up costing me a good deal more than those original speakers would have.

No major losses here but one boneheaded self inflicted mistake I ordered a heavy pair of speaker cables. The manufacturer recommended spades but I insisted on banana plugs. After a few weeks the weight of the cable caused one of the banana plugs to snap off in the binding post of the speaker. I had them reterminated with spades after that.
Going through loads of mid-fi equipment in the vain hope to find, by sheer ’magic’, some satisfying sound quality. Didn’t.
If you are right, then why it was working for me?

The answer: dont upgrade it embed it first..... :)
Actually now that I think about it the most costly mistake I made was CD. It came out right after college when I was broke and moving around and storing my Technics and records. Bought into Perfect Sound Forever. Only years later when I dug it out of storage and hooked it up did I realize my mistake. Still had kept some records, but gave most away. Listening to stupid CD BS cost me thousands.  

Made up for it since though, let me tell you!
I had a Superphon DM220 amp on the floor. Ataxia was starting to make it difficult to balance bending over so I was pushing on the rocker power switch on/off with my toe. Missed one time and pushed the power LED in.  The amp became a welder and popped both woofers in the sacrifice.
Ended up with better woofers and a 400s amp.
Total ~$600 damage.
Hooked up an Audio Research D200 amplifier to a pair of low Ohm Electrostatic Speakers. Damage to both pieces. Definitely learned an expensive lession.
Was installing a brand new Benz LP Moving Coil cartridge, my first ever high end cartridge and was wearing a long sleeve shirt, well, you know what happened. I snagged the cartridge tip somehow with my shirt, and after a few expletives, saw what I had done...the tip was canted sideways. That was a bad day. 
Marantz DV9500 (B-stock): bad drawer mechanism, went tits-up after a couple of months, it was deemed unfixable; Marantz SA8260: ditto, plus background hiss and noise; Audio Research CA50: bad power supply caused massive pops at random during music, not disclosed by Agon seller who shall remain nameless. All three were not cheap and ended up being turkeys. I suffered a loss on all three.
selling my trl gt 400s, gtp preamp, and soundlab a1s. still chasing that lost Magic! rip P.W.
My costliest mistake was to buy nearly one thousand vinyl LP's over the decades that had only one song on the album that I liked.

The 'one' song per album I liked cumulatively proved very expensive.
Buying brand new what I thought was “ state of the art” only to find out 1-2 years later that was “out of date” and new changes had happened HDMI for instance and now my 6k gear was worth only $1k and couldn’t be upgraded. OUCH
I purchased Bob Carver M350 Black Raven amps and I thought they were great! I still do!
But, I thought that if the amps were so great then with his speakers together they must be a great combo. Wrong big time! The speakers required so much power that the amps meters were pegged, fuses blew, and they had a terrible sound. 8000hz and up was a disaster. Traded them in quickly for a big loss. 

Adding damping material tweak to my 15" woofers... when removing one of the woofers from the enclosure I dropped it resulting in the magnet moving and locking the voice coil... Slick move trying to get that final 0.001% improvement that killed a woofer that is no longer manufactured.  So after 6 months trying 3 pairs of woofers w/ similar thiel parameters I finally landed on a solution with a minor crossover change.  Note there is no damping material on the new woofers and I'm perfectly fine with that.  Ugg.
I bought a pair of Carver Silver 7 tube monoblock amps at an estate sale. Paid $250 for both.

Ive been offered $8,000. Each.

I still have them. But my wife reminds that I can sell them, every time we need quick cash.

i should never have let her see the text I got from the seller; the 23 year old kid who sold them to me at his grandfather’s estate sale. He still texts 3-4 times a year, asking if he can buy them back.

At the time I bought them, I was the only looker. I told him they were “organ amps” from an old Hammond electronic organ... not worth much.

So the kid is mad at me, my wife is mad at me.

I have a big smile on my face, every evening at 6:30 pm....
What has been your costliest mistake in this hobby?

Maintaining this hobby......
Tons of costly experimentations, my latest decision is one for the ages, I decide to install a secondary system in my basement to let my wife sleep better while I could listen to live music level downstairs thinking that I could be happy with a basic system...read limited budget...God how naive... I’ve spent 2/3 of my initial budget on room treatment alone and I’m wondering where it will end.
My wife still complaints that the music is too loud as well...
costliest mistake in this hobby?  it's "Starting"...according to my bank account
Well years ago I had a fight with my exwife I came home to find my audio system destroyed and thrown out side only about a grand. I have bought used equipment that was no good about 600 and a nice preamp that listed for 6000 new,that I got cheap like 500 of course it lasted about 4 months .Hey it's only money.

I buy albums off of Discogs and didn’t notice that this one album was warped. Put it on my turntable and my JICO (Shure) VN5xMR stylus snapped like a dry twig. I was crestfallen....

@tinear124. I’ve got one that is similar. I was replacing a blown woofer in a set of “expensive” speakers. Removed without issue with a powered screwdriver... then upon reinstalling, the screwdriver slipped and yep... straight through the woofer. There have been a few others, mostly along the lines of spending too much money on cables etc... but the screwdriver through the woofer stands out.
50K in the red and counting, but each time I set aside solitary time to listen, I get goosebumps, especially if the tracks are well recorded. 

40% of that was in retrospect unnecessary, but I remain convinced the cash was better spent than some guys I know who spent/spend similar coin on drugs/booze/women/poker/super bowl tickets etc.

Although I must confess, women sometimes I can almost understand.
Lost a pair of maggies 1.6 which my cat thiught to be giant scratching post .
Letting go of items that now I wish I hadn't....

But what makes sense @ one point becomes senseless later, but one has to live thru that sort of thing to find out... ;)

Oh, well....Another Miserable Day In Paradise....*L*