[zzz]

I expected this to be ready for Christmas, but some issues took (and some are still taking) a sweet time to get adequately resolved. It still isn't as perfect as I would want it to be, but when did such mundane little things stop a diy'er from bragging?

So anyhow, it all started with a 26cm x 28cm board (one for both channels):

Then this board got populated and started to look like that:

However, since the amp didn't want to just start working, most of the time the board assumed a see-thru vertical position:

Now, many moons later, it almost works but still looks all the same:

Now, a little about the amp. It gets hot. Tubes obviously get hot, they're supposed to. Large heatsinks are hard to touch, probably around 80-90 deg c. Smaller heatsinks fluctuate as tubes warm up but aren't too bad. Transformers get boiling hot. Small filament tranny is probably well over a 100, even though it's the only transformer I'm not overdriving (it's 12.6V @ 4A being used at 12.6V @ 3A). My dad is going to get a measuring tool from work tomorrow, so it would be possible to find out how hot it *really* is instead of me guesstimating that. But I suspect that the amp might need a small quiet fan after all.

Sound... Weebl still occasionally oscillates mildly (sometime later I'll talk about that). Still, right now I'm going through rediscovering Omegas all over again (couldn't use them for over a month now) and I simply love them all over again too. I'll get back to the issue of quality in about a month when I put Weebl in a nice enclosure and compare it to my old trusty KGSS.

There.

Happy new year to you all.

 

[zzz]

A few hours ago I replaced Electro-Harmonix E34Ls that I used for most of the testing with JJ EL34 and the sound became a little more coherent and spacious. However, this came at a price of more apparent 60hz-based oscillations.

Both types of tubes sing along to music quite loudly. I don't yet know why or if it's supposed to be like that. Oh well.

 

[Budgie]

Is the topology your own, or is it a design you found somewhere?

 

[grinch]

Quote:

Originally posted by Budgie Is the topology your own, or is it a design you found somewhere?

this is zzz's implementation of the gilmore blue hawaii hybrid electrostat amp. as far as i know, he is the first to ever attempt to build something so crazy. gilmore apparently has built two amps with this design, but i have not heard of anybody else doing it. very cool stuff. can't wait to hear more about it when it's done.

 

[skippy]

insane. just insane.

 

[kevin gilmore]

quote

insane. just insane.



Not insane at all. All you have to do is listen to it for a few
minutes and you will know the glory of grounded grid.
Absolute magic. Combined with omega2's or he90's and
a scd-1 and you have reached full feng shui.


Now insane would be a pair of 845's in each channel as
the output tubes. (and corresponding 100ma bias per tube)
The drive circuit has plenty of muscle to do this.

 

[KR...]

Quote:

I'll get back to the issue of quality in about a month when I put Weebl in a nice enclosure and compare it to my old trusty KGSS.

Make it fancy enough and you too can be added to my page

Great job there!
I never liked the STAX amps from what I heard at the meet. But, you know what they say "when you want something done right..."

 

[eric343]

Crazy... Congratulations, though, I seriously envy you.

Quote:

Originally posted by kevin gilmore Not insane at all. All you have to do is listen to it for a few minutes and you will know the glory of grounded grid. Absolute magic. Combined with omega2's or he90's and a scd-1 and you have reached full feng shui.

Oh, NOOOO... PLEASE, Kevin, have mercy, I'm just building a KGSS, I don't want to upgrade, I don't want to upgrade, I don't want to upgrade.

ZZZ, you ever considered selling me a PCB or two?

Anyone know where to get a cheap SCD-1?

 

[zzz]

Quote:

Originally posted by eric343 Crazy... Congratulations, though, I seriously envy you. Oh, NOOOO... PLEASE, Kevin, have mercy, I'm just building a KGSS, I don't want to upgrade, I don't want to upgrade, I don't want to upgrade. ZZZ, you ever considered selling me a PCB or two? Anyone know where to get a cheap SCD-1?

Solid state unit is a very good amp, and man, it's waaaay easier to get working properly once you have a PCB with no traces missing. And you don't have to deal with tuberolling either. And one more thing, weebl will make you a basshead if you aren't one already. You sure you want that?

Unfortunately since I didn't have appropriate caps in my `collection`, I had to put something really large (0.02uf, Kevin suggested something around 400-500pf which is about 500 times smaller) on the tubes to damp oscillations, and the amp is a little dark. I'll address that when I have a chance.

Current board revision relies on certain heatsink shapes, some of which (the huge ones) just happened to be lying around so I don't think you'd be able to get anything like that unless you want to make them yourself. Actually, it could make sense to add another tap to the transformer and another rectifier/filtering bank to waste a little less energy on the 2SC3675 pass transistor. Dunno. Would be a little more expensive, but certainly wouldn't run as hot.

Problem with this board is that it's a major pain to make one. Etching is easy (only had to get a larger tank), but drilling a few hundred holes get a little boring. Getting some PCB house to make a few would be much better but at that size boards aren't going to be cheap.

I may try making a unit with 845 or some other power triodes sometime this winter if I can be bothered enough to do that (and if I have enough money -- 845s are not cheap), but using solid state plate current sources with them would be suicidal. Mmmmm, 300W filament transformer...

 

[zzz]

Ok, I think my quest to stop oscillations is successfully over.

1) 22pf between gate of 2sk216 and output (4 caps total),
2) 220pf between control grid and anode on all of the output tubes

1) was done long time ago but I'm not sure it's even necessary at this point. I went from 44pf to 22pf with no change in amplifier behaviour yesterday, and it very well could be that even these 22pf are now redundant. It's a minor pain to desolder them though as they are in a crowded spot, so I'm not going to bother for a while.

2) was done today. As I said, I used 0.02uf before, and the amp was a little dark and had a grayish background. With new and much smaller caps amp finally opened up. Yes, it is pretty amazing and now I see that it is quite a bit better than KGSS.

Anyhow. Cary has been shipped to my new place today already. Weebl is going to be disconnected and partially disassembled today or tomorrow and put aside for the time being, and KGSS is going to get its parts back. Oh well...

 

[kevin gilmore]

quote

2) was done today. As I said, I used 0.02uf before, and the amp was a little dark and had a grayish background. With new and much smaller caps amp finally opened up. Yes, it is pretty amazing and now I see that it is quite a bit better than KGSS.


YESSIR!

I think my stax quest is finally at an end, because from here
i just don't know how to make it any better!
(well real 1kv triodes...)

Onward to the Uber amp...(production version)

 

[kelly]

Quote:

Originally posted by zzz Yes, it is pretty amazing and now I see that it is quite a bit better than KGSS.

I know it's not finished yet but can you elaborate any? In what ways does the hybrid sound better?

 

[NotoriousBIG_PJ]

I call dibs when its finished. ^.^

Biggie.

 

[zzz]

Quote:

Originally posted by kelly I know it's not finished yet but can you elaborate any? In what ways does the hybrid sound better?

I will have to talk from memory because there isn't an easy way to try the solid state amp at the moment. Apply doubt as necessary.

A thing that really stood out for me was hybrid's bass. It is incredibly well controlled (eg, first track on Massive Attack's `Mezzanine`: with KGSS some of the bass notes in the beginning still blend together, weebl clearly defines when one begins and another one ends), goes ultra deep, and it seems easier to track the bass-lines through the song no matter how many layers of sound are there. Imaging sure feels more precise as I don't remember ever `seeing` such a vivid picture in headphones before.

There are a few more things that I feel are different (and different for good), but I'll have to compare the amps side by side to say more, as otherwise I wouldn't know if there actually is something or I'm just imagining it.

Most Cocteau Twins CDs still sound pretty bad though.

 

[eric343]

Just out of curiosity - is it possible to use the Blue Hawaii output stage together with the KGSS as an input stage?