Earspeakers

Yeah I've got the complete Gould. I understand the engineers tried their best to edit out his humming, I wish they hadn't bothered. Adds to the performance IMO. This is the later Gould, the early version bores me to distraction. Funny to hear new stage noises in recordings I've listened to for years. "What are they doing back there?" I keep catching myself thinking.

These are newer recordings. I used to do recording engineering (non professional), with big groups you can't avoid miking the hall so pick up on the total ambiance. Davies Sym hall in SF (where I played for years) is a double wall construction. To get inside you go through thick double doors, the outer hall is essentially a shell. I would sometimes go out on stage and it would be almost dead silent (a tiny bit of low frequency air conditioning that was impossible to entirely remove.) In the middle of San Francisco, it was magical. The most famous for this is the Opera house in Rome, name is slipping my mind at the moment, you can hear Vespas zipping around the plaza outside. The Callas recordings are known for this. No sir! KGSSHV next couple weeks, then climbing Megatron Mountain, and finally summiting T2.

Back to these amazing amps, what's really weird all the traffic noise I hear. I only listen to classical music, a lot of concert hall recordings (or almost all). I've had this happen once before with some horns, but now even more I'm getting major traffic noise from the recordings. Especially the older halls are prone to this. I keep having to pause just to make sure it's not in my environment (I'm in a very quiet room on the edge of town (almost the country). Truly amazing little amps, congratulations to the Mafia and community.

Now I have a moral dilemma, since I'm building every mafia design I can get my hands on (and documenting them for posterity), should I also build out the revisions??? I actually do have a second KGST transformer, and a smaller one wouldn't hurt .... must stop ...

Might check that Kevins site has the latest, I just did a board run not long ago and it was still 1.5k. In fact I can see the PS board is quite different. Looks like it's the "mini" version. Amp boards look to be unchanged other than the 1.2k.

Which I did, which is why I'm also making sure to write about it here so follow on people get the news. I'm also working on a FAQ and documentation for these boards, my small contribution. Ah that makes sense now. Don't get up in arms, but just to note, Birgir has been tweaking the KGSSHV. Not long ago I happened to buy one of his (one of the last) with the feedback, shortly thereafter he removed it, that's certainly a bigger change then a little text. Also don't get the wrong impression here, I'm not complaining. The reason I mention it is if the community would like to avoid newbie builder issues in the future (e.g. constant questions about the resistor) the easiest thing would be to change the writing. Just saying!

Well I mean change the legend, for the newbies.

Well, because I love doing rework so much I swapped out the 1.5k with a 1.21k, fortunately having some on hand. Now it seems I can calibrate again. Curious, this seems like a common enough problem, why not just make it a 1.2k, or split the difference with 1.37k?

The bias is measured from the test point The adjustments are all open with the case open, so yes it's warmer with the case closed. But this has pretty good ventilation (see a page back), but maybe that's the problem? Change the resistor in series to try what value? Increase it, decrease it? Looks like 1.2k or 1.37k from 1.5k is the answer. EDIT: Wuupsies (maybe) Looking closer at the circuit board I see mostly obscured, two little circles on the trims, indicating where the trim adjustment should go. I've got the balance in backwards. But these trims are symmetrical, aren't they so it shouldn't matter? And if they weren't, why did they calibrate so easily when I first turned them on?

Thanks, that's perfect. So I've been running the KGST for a couple of days and am checking bias/balance/offset again. I had previously set these numbers by the procedure above, letting them run an hour or longer and readjusting. The headphone bias drooped to around 517V One channel balance was around 10 volts and offset was 17, I could zero the balance but can't get the offset to zero The other channel had good balance, but the offset is likewise 17 or something, and I can't zero it. Help! Why would these be just fine when I set them before, then decide to uncalibrated? How can I get them calibrated again?

Hmm, at $2.50 a pop. At least it gives us the part number for the shoulder washers http://www.mouser.com/Search/ProductDetail.aspx?R=7721-7PPSGvirtualkey53210000virtualkey532-7721-7PPS What about the 7721-7PPSG? That's what AAVID uses in their TO-220 kit above.

Yeah I think that discussion is the one the pointed me towards the wrong isolators.

Do you have a mouser link for the isolators from one of your past orders? I got some here on somebodies advice, and measured with my caliper and they seemed correct, but don't work.

"Otherwise I'm not interested in farting around with 007-mk1, 404's or whatever else." Famous last words, I received a 007mk1 early version (carbon box) and have 404's. On the Siggy they're finished and on the way. Look beautiful, the repair shop offered to buy them from me

I need some more Peek screws and so would split an order with anybody. I have the ones Laowei links to above and they're great.

getting an error trying to access that

I tried to tempt Birgir into doing a doing a SOTA low end amp. One board, wall wart powered, current parts, like a high end 252S. He was like "I see no reason to do that", lol ... except I'd have a good amp at work. If I wasn't so busy building I'd try my hand at it. Anyhow interested in their future offerings of course.

Checked the Hosa - yeah 1 and 3 are on ground. Don't know, but the stupid thing hums. On the KGST - further listening. Truly a beautiful little amp. Information retrieval is remarkable, I heard a Bach Cantata on period instruments, there's a trumpet back there! Poor guy must have been shy trying to play this period piece, but he was buried in the orchestra. Now I'm hearing him. And the presentation is overall warm, inviting and relaxed, but not overly so. However, the bass sounds uncalibrated to my ears (so far). Too much, and a bit more indistinct than it should be maybe. I need to listen to this with the 007/009 and 4070 to make sure, but cellos and basses are too bassy. Too big, too round, too powerful. Or it could just be me.

Thanks, KGSSHV this weekend. I have everything except (surely) some parts, so have Mouser on 24 hour emergency team notice to dispatch me what I need right away. The KGST was a first get my feet wet. Made a few mistakes with the chassis I'll do better with the KGSSHV. Anyhow expect that in three or four weeks. After that, the Megatron (if my Teflon caps come in on time), then ... the T2! After that, a BHSE on order that I'm wondering why I ordered, and then I won't know what to do afterwards. Probably a FrankCooter 845 Stax amp. Oh yeah, here's my handiwork. I call it The Ham Because it has a Hammond Chassis and HAM radio parts. Having worked in measurement labs my whole life I like the industrial cold war instrument chassis look. These Hammond Chassis - while Hammond quality and finish (both good enough for my book) - are a treat to work with. I like an easy build and lots of ventilation, these have both in spades. I also have access to a machine shop but prefer just doing some drilling in my garage. I'm going to flesh these out with some dials probably (VU) and a few more knobs and lamps. I should add, the metal work was simple. Bought a circuit plate in .125 aluminum from OnlineMetals, cut to my specification. Drilled that out with a row of big ventilation holes (hard to see - horizontal under the amp boards) and all the other necessary holes. Attached to the chassis via four 2" standoffs, simply reusing the ventilation holes on the bottom to attach. Then mount all the hardware via standoffs as seen, with the toroid transformer suspended underneath the power supply board. So all the AC is under the circuit plate, and all signal is above. Then it was just drilling out the back plate for XLR and power, and the front panel, both of which were included. If you want to go with FrontPanelExpress obviously you can easily have whatever you want made.

Some sockets put shield automatically to socket body, and thereby immediate chassis ground. Neutrik generally has a tab to make it be your choice. Ideally you would run a ground wire to the star ground point. However, with any normal amp your star ground point will turn into a big enormous lump of solder, so cutting that down a bit helps. Second and perhaps more importantly, it is probably better to let the source ground the shield to not set yourself up for a potential ground loop. As long as one side grounds, it's good. Edit: I should say I don't know if that's any standard practice, but what I often do. Not sure it makes much difference in any case. The impedance of these cables isn't critical (i.e. 50 ohms) because it's all extremely low frequencies, and it's twisted triplet anyhow, so do what works for you. I worked with a guy who spent 10 years working on ground for a project (super high sensitivity measurement device). He used to say "there is no such thing as ground".

Which resistors are you using, the Vishay brown 600V versions I hope? Share your BOM, I'd like a decent KGST BOM for once and I've got another to build.

Good question, probably not. Pieces of crap I just bought for this. I'll get the Neutrik. Edit: This one I guess http://www.mouser.com/ProductDetail/Neutrik/NA2MPMF/?qs=sGAEpiMZZMv0W4pxf2HiV9y0EyfHsAgRVcOPr0CUs0o%3d Damn this amp has a lot of bass control. Scary. Just listening with my test headphones (207) for a few days at least. I'll try a 404 next, my go-to headphone at the moment. It's a warmer amp than the 323S too I believe, but it might be the 207's that I haven't heard in a while. There's some muddy too which is the 207's, need to try some better headphones soon.

Fired up! Sounds good, reeeeeeeeeel good. I get a hum at the top of the volume range, but I'm using a Hosa RCA to XLR converter plug and it's only with that plugged in. Pulled it's dead silent. Pulled out a cheap DAC with XLR output and it's dead silent, except near full bore there's a oddball slight noise that comes in at one channel and then travels to the other, then disappears at full volume. Odd, need to look into that. The gain seems a little low, compared to the 323. I've got just enough, maybe that was the intent to have the amp playing at the low end of the volume control. Wow, quite a delicious little amp. Compared to the Stax offerings there's far greater separation between instruments, each is more distinctly themselves. Presumably better separation between channels compared to the 323S.

Desoldering anything sucks, don't do it unless you have to.

Great thanks Laowei! Even with the stability, why not use the servo? Seems like it can't hurt.