spritzer

I guess they are just trying to make people forget about the HEV70...

With only one winding then the trick is to pick some compromise which means the tubes never see a load which they don't like. The tubes are also driven well below their limits which helps in this regard. Nothing beats multiple taps though... It's better than the older amps but looks like there is at least one cold solder joint on the tube sockets (top 4 pin with blue wire attached) and he's still using those awful rotary switches. Looks like somebody gave Alpha a call and ordered some 24mm pots...

Yup, that's the GB board. I agree that the M3 is a nice amp and very simple to build but it is very much lacking compared to the Dynalo with the LCD-2's. Large part of the problem are the parts used and the compromises needed to make it so simple to build. Still better than 99% of the commercial crap out there...

It will be fine. The 900V rating on the 1968's is conservative as most units surpass it by quite a margin.

Thanks for that Larry. The negatives are certainly not switched but I can't see if they are tied together. Different bias supply, in your unit it is a voltage doubler fed into a voltage divider.

Fixed bias is indeed a much better way to do this. For the extra negative supply I'd just make small, fully floating, regulated supply but pretty much anything works. Batteries are a fun way to do it especially with a large sign saying not to touch... One of my friends got a bit too close to the ES-1 when I was testing it's revised output stage but one mention of the batteries floating at -460V was enough for him to back off. While we are on the subject, I'm making slow but steady progress on my B-10 (improved A-10): Trying to keep this as small as is possible so 1U for the amp and same size 2U chassis for the PSU.

I think I still have those made in the USSR tubes somewhere...

The top opens up and what I'm after are the bias supply setup and the speaker input/switching. On the unit I'm currently trouble shooting the bias supply is handled by a off the shelf voltage tripler from a CRT tv which is utterly unsuitable for this role. There is also no ballast resistor for the bias supply which is a bad... very bad idea. Second issue is that all the black speaker posts are tied together and the switch only switches the red. Plug in a bridged amp (Class T, high power SS, circlotron) and it will go BOOM!!! No mention of this "feature" anywhere I can see...

Quite right.

Hey, if you used our lovely letters then you'd type less. For example, though would be þó. Edit. I really don't know what the Finns are adding to their water supply to end up with that...

To bad they can't spell the names correctly. I wonder how many realize the name is bif-röst and not bi-frost....

Would anybody with a Woo WEE mind opening it up and posting pics? I'm troubleshooting one unit and I have some major concerns about the design which I need to verify.

I don't even want to think about all the pending projects and the cost of building them...

The HD600 leaving us is sad news indeed. I think I need to borrow a set and spin some Dire Straits...

Yup, it's just a very busy time of year for me so it will have to wait. I still haven't tested any of the last prototype boards I ordered... I do have a bunch of 6BL7's sitting here so I'm ready when the time comes.

There were some other circlotrons but every one was a bit different. It's been a while since I read up one this but a lot has to do with the way feedback was handled. Some of the older amps would oscillate like mad...

Reducing transparency to make them work is only part of the equation. If I wanted to do so then I'd just construct some heavily AC coupled amp and use the cheapest capacitors I could find. Hell, let's not stop there and mess with the operating points so the tubes are as non-linear as I can make them. In essence this is what Sennheiser did with the earliest Orpheus amps but they were after a certain "sound" and those transducers need a sympathetic match to reach their full potential. Put them on a wire-with-gain amp and the results are underwhelming. With the 009 you have a similar situation except they are a Stax Omega so transparency and neutrality are the name of the game. I just think they took the transparency too far, as in it pushes detail into your face instead of just putting it out there. Tame this a bit and you end up with a much more pleasant listening experience. I've said so before but I do think that the Stax voicing for their cans has been a bit "off" as of late. When making the diaphragms there are certain compromises that have to be made and I think Stax just ventured into the wrong direction. This might be done intentionally to make the cans fit the amps better or is could be something as simple as the new diaphragm material acting up. Let's not forget that Stax went to 1um in 1987 but back up to 1.5um after the extensive research done for the SR-Omega design in 1993.

They are basically circlotrons so the high impedance issue of tubes is tackled with multiple triodes in parallel so no output transformers or huge output caps..

I'm using the isolated USB connection most of the time. It's better than any transport I've tried recently but something like the ML31.5 might beat it.

My main source is a MSB DACIII Platinum with the standard modules but I have the same results even with the very warm AudioZone DAC-1.

Looks like a great time but you guys need some more gear...

There are no etch issues with the 009 but it shares many of the Lambda traits. Another candidate would be the SR-X Mk3 Pro which is pretty much a properly done Grado so a bit bright and upfront. I will never buy another cable so that's a no go and the only exception would be some Kimber Select stuff since it holds its value. The TCSS is too stiff for headphone cables though but I have a generous amount of mil-spec (made in 1957) silver wire courtesy of Kevin.

So it's basically what NXT were doing 10-15 years ago? Way to go ML for inventing something... Reminds me of their great advances such as Clearspar™ technology which are just transparent spacers inside the electrostatic element. Yay for transparent plastic...

Stax have never aimed for the euphonic mess which is the Orpheus setup but the 717 and 727 both employ circuit topologies aimed to make them sound a bit thicker while sacrificing as little resolution as is possible. With the 727 this is partially linked to higher distortion but some of it is just down to how the circuit is voiced. I'm not a fan of this any more than I'd cram an amp full of cheap polyester caps just to dull the sound. My way of thinking was sparked by the whole misplaced SS vs. tube debates out there and people not fully understanding any of it. Back in the day Stax were designing state of the art amps with the technology available at the time and that meant very low distortion amps but fitted with fully singled ended output stages AC coupled to the output. The rest of it is all DC coupled with current sources and a rather nice PSU so perhaps this would mean just the right amount of tradeoff... It certainly works for me but I have to find time to finish and test my version of this will all modern parts and report back. As a darker BHSE, I think part of the issue is adding some color to the amp, not having an "endless" current reserve available at a moments notice.

With Easter looming I seem to be making an endless stream of cakes. Here's one to make you all a bit hungrier... That's a chocolate and almond base with a chocolate, raspberry and cream mouse topped off with some 66% chocolate ganasch.