Impedance switch for SII?

[Deke609]

Thanks PB.

I'll stick with balancing at the speaker outs and build two 2 DPDT boards (sans resistors) for impedance switching.

 

[Deke609]

I built and installed the impedance switching boards today and they work! Very cool.

My only issue is that flux found its way to the contact pads of the DPDT slide switches. I was able to get most of the flux off the throws, but the poles at the center are inaccessible without opening up the switch. Does anyone know a trick for cleaning the center poles of slide switches?

cheers and thanks,

Derek

 

[Deke609]

And here is how I implemented PJ's ingenious 2-DPDT solution for impedance switching, in case anyone is interested. I dealt with balancing separately.

I believe my implementation is correct, but can't vouch that it is. But it sounds good, other than 16 Ohms which is too quiet and distorted on my LCD4s - I think the current is too low to drive them. 

 

[Paul Birkeland]

But it sounds good, other than 16 Ohms which is too quiet and distorted on my LCD4s - I think the current is too low to drive them.

No, this is likely a wiring issue with the proto board.  16 ohms should be noticeably louder than the lower impedance settings. 

 

[Deke609]

Thanks PB. Hmm. Weird that 2, 4 and 8 sound great.  I'll re-evaluate the 16 Ohm config. I must have goofed something specific to the 16 Ohm wiring.

 

[Deke609]

Update: checked my wiring, and couldn't find a problem in my implementation, so I tried switching to 16 Ohms again ... and lo and behold it sounds great and louder than at 8 Ohms.  Not sure what was going on last night when I tested it. Last night it sounded horrible. Maybe the flux on the switch pads prevented good contact?  16 Ohms was the first config I tried last night.  Maybe subsequent switching cleaned the switches?  Dunno. But it's working now.

 

[denti alligator]

I would still love to get my hands on one of these. Any chance they would be sold as a kit?

 

[Paul Birkeland]

We have no plans to put that kit back out.  It was unusually hard for our suppliers to keep the little switches in stock, and explaining how to properly use the kit was something we had to do over, and over, and over again.  This is a big part of why the new SEX amp says to wire for 4 ohms for headphones or 8 ohms for speakers.  This has eliminated a lot of "I wired my amp for 16 ohms to use with Grados and it's too sensitive and I hear some noise" kind of threads. 

 

[Jameson]

Unrelated: Anyone heard from Derek? Hope he’s ok.

 

[Paul Birkeland]

Unrelated: What happened to Derek?

Derek and I had a disagreement over a post he wrote here.  I suggested that content would be better posted in a different forum and I believe I offended him in doing so and he left.  There was never any intention for him to stop participating here, but this is not the first time that this exact chain of events has happened, nor will it be the last time. 

 

[Jameson]

That’s too bad. I hardly ever understood what he was talking about, but his pursuit of perfection was admirable in a way.

I actually edited my original post in case it was something like this.

 

[Paul Birkeland]

I wouldn't sweat it.  The big groaner of taking actions like I did is that it makes me nervous that other people will hesitate to post on here. 

 

[Jamier]

Have you tried to contact him to, you know, patch it up?

Jamie

 

[Jamier]

One of the problems with theses forum posts is that our written words are often mis-interpreted. I mean, when someone is really coming after you it’s usually pretty clear, but many times well intentioned statements get taken the wrong way.

Jamie

 

[Paul Birkeland]

He's welcome back whenever he want to be here.

 

[Paul Joppa]

He's welcome back whenever he want to be here.

For the record, I second that motion - he's welcome back any time.

 

[Doc B]

PB has expressed himself very well here and I support his explanation 100%. I've been doing this forum thing for about 22 years now. One of the things I have learned that keeps a forum healthy is for it to have a well defined purpose. Here it is pretty clear cut, the purpose is being a support forum for Bottlehead kit builders. It's very flattering that we are often asked our opinions of more esoteric design aspects. Luckily there are very good and popular boards that are for exactly that kind of thing, like DIYAudio.

Our intention was not to drive someone away. Unfortunately we can't know how a person will react to this kind of suggestion. As PB mentioned this wasn't the first time someone who is a fairly frequent poster took their ball and went home. I don't imagine it will be the last. The door remains open to anyone who wants to discuss the topics that are relevant here.

 

[Left my hat]

Hi all –

A forum member alerted me to this discussion. This is all water under the bridge. Yes, I was a little surprised and embarrassed, and even at little offended at first, when I saw PB’s post a while back that prompted me to leave, but it’s all good. Surprised and embarrassed b/c I didn’t clue in earlier. That was my misunderstanding. I always knew that, as a matter of fact, discussion on the BH forum is focused almost entirely on troubleshooting the kits and the normal types of mods, tube recommendations, etc. But I didn’t clue into the fact that this was the intended focus, and mistakenly thought that my “out there” stuff was kosher and even felt a bit encouraged by the subtitles to the General Discussion and Technical Topics subforums. But PB had indeed hinted to me in the past that my stuff better belonged elsewhere and I failed to pick up on those hints. As even some of the people who love me say, I only pick up on 80% of the obvious.  ;D

As for briefly feeling a bit offended, well, that’s on me and the feeling has long passed. I’m a big boy. After dusting myself off and putting my big boy pants back on I realized that PB was right (except about me belonging on the Tweakers forum – sheesh  ). My stuff does belong better elsewhere. And more importantly, I never thought that anything PB posted was intended to insult. So we’re all good!

And just b/c I can’t help myself, I’ll mention that I continue to pursue my esoteric stuff. I’ve been unusually busy with work this year, but I plan to get to my experiments with taming the Q of my grid chokes and playing around with resistor bias in my rebuilt Kaiju later this summer. @PJ: I am hoping I can hit you up with the odd question every now and again over on AA. I’ll keep the questions non-BH focused and more general so as not to offend the rules against hawking commercial interests on non-commercial subforums – BH doesn’t sell the stuff I’m playing with, in any event, but just so there’s no question that it’s 100% above board.

Lastly (this has turned into a retirement speech), there really are no hard feelings. I’ve learned tons from the BH crew and I remain very appreciative.

Aha! There’s my hat.

cheers and all the best, Derek

 

[dpwoos]

It's not a secret, I think this has been posted before. Here's the circuit. They are DPDT switches, except the balanced/unbalanced which is SPDT.

I plan on implementing S.E.X. 4/8 ohm switching using a single 4pdt switch - 2 poles for each channel. My question is about the routing of the OT wires and the placement of the switch. Do I need to worry about hum? Thanks!

 

[Paul Birkeland]

My question is about the routing of the OT wires and the placement of the switch. Do I need to worry about hum? Thanks!

The output impedance driving these connections is very low, so noise pickup isn't as much of a concern, but as always you'd want to try things out before drilling any holes.