[Prune]

I've seen several DIY designs and the KGSS with the Blue Hawaii output stage looks like the best thing out there. In a few months when I have the money I think I'll try to put one together.
What I want to ask is how many people have built it, and if they can share their experiences.
This far I've only found these two threads:
http://www4.head-fi.org/forums/showt...threadid=17717
http://www4.head-fi.org/forums/showt...threadid=23465
Only two people have built this?

By the way, in the Blue Hawaii schematic, is the top of the 2SC3675 connected to the horizontal wire or just crosses it?

 

[eric343]

The KGBH/Blue Hawaii+KGSS/Hybrid/WhateverYaWannaCallIt is almost certainly the best electrostatic headphone amplifier. Period.

Actually, I think the number is 3, though the third might just be building KGSS-en and not hybrids. Only person who I know for sure builds hybrids for sale is Zzz.

Kevin Gilmore happens to be our resident electrical engineering god. Zzz is just nuts, and/or very bored, with experience and formerly money. (building high end Gilmore designs while hanging out on Head-Fi kind of does that to you.)


For the ultimate in el-cheapo design (as suggested by zzz), you could try rigging up a bias supply and running the stators off a regular headphone amp with *very good* resistance to oscillation when driving capacitative loads and lots of voltage swing. If you don't know what I'm talking about, ignore the previous sentence.

 

[Prune]

Thanks for the reply!

Quote:

Originally posted by eric343 Only person who I know for sure builds hybrids for sale is Zzz.

OK, but I'm not looking to buy. I plan to build it myself. I've not much building experience (few amps and a DAC) but I think I'll manage. I'm not worried about the HV since I've messed around with that before.

Quote:

running the stators off a regular headphone amp with *very good* resistance to oscillation when driving capacitative loads and lots of voltage swing.

I thought electrostatic cans need hundreds of volts of voltage swing. I don't know what regular amp has that. In any case I've decided to make the Blue Hawaii.

I redrew the KGSS input stages (taken from Headwize) and Blue Hawaii output (taken from Gilmore's drawing) into the diagram below. Again, I'm not sure whether the top of the 2SC3675 is connected to that horizontal wire. I left feedback connections as they were in the KGSS since I don't know how to change this (or whether there should be feedback at all)

. There are probably other errors as well since I wasn't sure about some things; maybe someone could take a closer look.

(Excuse the png format, but it's smaller and better than gif.)

(Yes, I also posted this image at Headwize and Diyaudio but wasn't able to get much advice there

, so I'm trying here, where people are more familiar with this.)

Looking at the cost of quality parts (Goldpoint attenuators, etc.) it looks to be about $1000 US excluding the chassis.

 

[kevin gilmore]

The top of the 2sc3675 does in fact go to ground and
the schematic is correctly drawn as is. At some point
in the next few months a person will finish his board
layout, then people will be able to submit that to advanced
circuits for compete boards. Makes it much easier to build.

quote
For the ultimate in el-cheapo design (as suggested by zzz), you could try rigging up a bias supply and running the stators off a regular headphone amp with *very good* resistance to oscillation when driving capacitative loads and lots of voltage swing. If you don't know what I'm talking about, ignore the previous sentence


NO! unless you have krell or other balanced output amplifier
just laying around. You need to drive both stators.

A pair of krell monoblocks with their 100 volt output should
actually work pretty nice.

 

[eric343]

Quote:

Originally posted by kevin gilmore NO! unless you have krell or other balanced output amplifier just laying around. You need to drive both stators. A pair of krell monoblocks with their 100 volt output should actually work pretty nice.

Hey, you've got 'em, try it and report back

Seriously, though, your dynamic amp can be run in balanced output mode, no? Also the HeadRoom Blockhead is a balanced output amplifier... Gotta try it sometime, be interesting to hear one of those amps on a real pair of headphones (

) even if they wouldn't have the dynamic range of a proper electrostatic amp...

 

[Prune]

I've begun to put together a parts list (unfinished):
http://www.cs.ubc.ca/~trifonov/blue_hawaii_parts.txt

 

[eric343]

If you can do a Hybrid for $1k with all those premium parts, please post a completed parts list with sources ASAP!!!

Oh, and do tell us where to get that titanium/magnesium chassis! Sounds like the ultimate portable amp, doubles as armor in case of civil war

 

[Prune]

Well I just updated the list, and the only thing missing is the resistors and chassis/knob/legs. Resistors are cheap. Titanium enclosures are used for medical equipment, and there are several manufacturers on the Web, but I doubt they'd make a custom one for just a single unit. One can always buy titanium sheets and find a place to cut them. As for magnesium, I haven't looked, but should be possible; after all, it's used for the cases of some notebooks and minidisk players.
Adding up the numbers, it's around a grand. Add the enclosure and resistors, it is probably going to come out around $1300 total.

 

[Jupiter]

Prune,

zzz was selling the 2SA1968 pretty cheap. You could ask him if he has any left.

I hope you're pretty confident in your DIY skills or you might want to consider building the KGSS first. (I'll build the KGSS first.)

 

[Prune]

Jupiter, I'm not buying anything yet, since I won't be doing this for a few months.


OK, now I have a bunch of questions; please excuse the dumb ones:

1. For the wattage rating of resistors in the Blue Hawaii diagram, unless they were marked, I assumed 1/4 W (as in the KGSS); is this right?
2. Above the LED connected to the 2SA1156 gates in Gilmore's drawing it says '-300'; what is that?
3. Since there are two channels with balanced inputs, a quad attenuator is needed. Unfortunately, Goldpoint doesn't have quad versions of their ladder type (the best one), so what about mechanically linking two stereo attenuators?
4. Is it a problem to use point-to-point wiring instead of a PCB?
5. Is 19.5 awg Cardas litz wire OK for the signal paths?
6. In the project addendum for the KGSS at Headwize, someone preferred the MAT02 in place of the 2SK389. Any thoughs on that?
7. Are 2 W ceramic potentiometers (such as in the parts list) OK for the voltage adjustments?
8. Is 2 W enough for the zeners?
9. The current rating of the LED doesn't matter as long as the voltage drop is 1.7, right?
10. Looking at the purple part in the diagram, can a potentiometer be used here?
11. What EL34s should be used? Are JJ OK (box of four is only $48)?

 

[zzz]

yes, 1/4w is enough, though you have to watch for voltage rating occasionally. -300v is a marking on a schematic. you don't have to use balanced inputs but yes, pairing up stepped attenuators works. point to point wiring -- heh heh. indulge yourself. wire itself doesn't matter as much as its insulation. I actually need to try mat02 myself. any pots would do, but I'd suggest going with multiturns. all zeners would work. you can't really find a high voltage zener with an unappropriate power rating. ideally, you want the voltage drop to be 1.6v at the biasing current, but the design is not too sensitive about this. purple part in the diagram is a potentiometer (commonly with wiper and one of the other legs wired together). doesn't magnesium powder combust? anyway, drill at your own risk. I'm all out of a1968's while bdent isn't. you don't *have* to drive electrostats by a balanced signal, it's just that the performance wouldn't be as good. I wouldn't recommend that amp if you're not planning to get the omegas as well. src-5 can be had from audiocubes.

Quote:

Originally posted by Prune Jupiter, I'm not buying anything yet, since I won't be doing this for a few months. OK, now I have a bunch of questions; please excuse the dumb ones: 1. For the wattage rating of resistors in the Blue Hawaii diagram, unless they were marked, I assumed 1/4 W (as in the KGSS); is this right? 2. Above the LED connected to the 2SA1156 gates in Gilmore's drawing it says '-300'; what is that? 3. Since there are two channels with balanced inputs, a quad attenuator is needed. Unfortunately, Goldpoint doesn't have quad versions of their ladder type (the best one), so what about mechanically linking two stereo attenuators? 4. Is it a problem to use point-to-point wiring instead of a PCB? 5. Is 19.5 awg Cardas litz wire OK for the signal paths? 6. In the project addendum for the KGSS at Headwize, someone preferred the MAT02 in place of the 2SK389. Any thoughs on that? 7. Are 2 W ceramic potentiometers (such as in the parts list) OK for the voltage adjustments? 8. Is 2 W enough for the zeners? 9. The current rating of the LED doesn't matter as long as the voltage drop is 1.7, right? 10. Looking at the purple part in the diagram, can a potentiometer be used here? 11. What EL34s should be used? Are JJ OK (box of four is only $48)?

 

[Prune]

Thanks, zzz.

Quote:

Originally posted by zzz doesn't magnesium powder combust?

It's an alloy, not pure magnesium. You'd need an acetylene torch to burn it.

Quote:

you don't *have* to drive electrostats by a balanced signal, it's just that the performance wouldn't be as good

I plan to use a balanced source.

Quote:

I wouldn't recommend that amp if you're not planning to get the omegas as well.

Of course. But I want to have a working amp before I go out and buy the Omegas.

Your point about wire insulation: what insulation do you consider sufficient here?
Also, what about the brand of EL34?
BTW, would the MAT02 be a direct drop-in replacement here (without adjusting anything else)?

Another thing I forgot to ask: does it make sense to use DC for the filaments, or is AC better?