Alternative use for HT bypass

wireburn · « **on:** 25 Mar 2003, 01:21 pm »

I've been mulling over HT sub integration with the GK-1, Options 2 and 3. Here's an idea: What if I were to put a separate mono sub input on the GK-1 which would be routed to one channel of the second output when HT bypass is engaged? Since the second output and volume control are cut off when HT bypass is engaged, why not use that second output to route the HT processor's sub out?

-Mike

AKSA · « **Reply #1 on:** 27 Mar 2003, 03:40 am »

Mike,

Send me a schematic or block diagram of what you have in mind and we'll talk some more. Unfortunately I can't envisage what you have in mind at this stage.....

Cheers,

Hugh

wireburn · « **Reply #2 on:** 27 Mar 2003, 01:12 pm »

Hi Hugh,

I seem to remember you mentioning a 4PDT switch that was to be the HT bypass. When enabled this switch would route the signal from the SS stage before the pot directly to the primary output, allowing the input to "pass through". I'd like to add a sub input (mono) that would be routed to one of the secondary outputs when the HT bypass switch is engaged, essentially allowing a third channel to "pass through" on a shared secondary output.

In effect, what I'm trying to do is get better HT sub integration by allowing the HT processor's sub out to pass through the GK-1, but only in HT bypass mode. In normal mode, I'd like the sub to get the tube-bypassed, but still level controlled output from the secondary, just as you've described previously.

If you need a picture I can attempt to draw one and post it, but not knowing your schematic it may not even work the way I have in mind. The relay-based nature of Option 3 may complicate this, I'm afraid.

Thanks for listening,
-Mike

MaxCast · « **Reply #3 on:** 27 Mar 2003, 01:44 pm »

Mike, I'm not sure if I follow correctly, but this is a great idea if it could work.

When HT bypass is on, using a HT system the sub out of the processor would go through the 2 ch preamp. Un-processed just like the mains.

When HT bypass in off, using a two channel source the 2 ch preamp sends the signal to both outs allowing use of the sub for 2 channel also.

There may be some crossover issues to adjust, but may be worth it. Also, keep in mind the use of two subs.

wireburn · « **Reply #4 on:** 27 Mar 2003, 01:48 pm »

Yes, there will be crossover and level-matching issues to contend with, but my processor is very flexible in this regard. I shouldn't have to touch the sub's level for music or movies after calibration.

Two (or more) subs could be used with this approach.

-Mike

wireburn · « **Reply #5 on:** 27 Mar 2003, 04:19 pm »

Here is a quick image I put together:

The SS section could be moved to the other side of the switch, but I seem to remember Hugh mentioning that the signal still went though the SS section when HT bypass is engaged.

Would something like this work, Hugh? How about with Option 3? I'm not scared of adding another relay and doing some Atmel tweaking.

-Mike

AKSA · « **Reply #6 on:** 27 Mar 2003, 09:12 pm »

Hi Mike,

Yes, it would work no problem at all!

My pleasure to 'listen'! Wow, I do this for a living.......!

ON both the Option 2 and the Option 3 the existing HT Bypass switches input from a selected source directly to output; the signal does pass through the selector switch (a high quality Lorlin from the UK). As it is presently configured it does not in fact pass through the SS section, or pot, when the HT Bypass is ON. This was a design point; I didn't want it going through either the pot or the gainblock/tube since it had to be a bypass in the true sense of the word, and my understanding was that in this mode the digital volume control on the HT processor would take care of attenuation and would also have low Zout. While the signal will still be passed to the SS gainblock and tube, it won't be switched to a load at the output, so the signal seen at the output is precisely what goes in at the input.

It should be quite simple to use existing circuitry without mods to the ATMEL controller, because if the HT Bypass merely switches another relay the additional current - 30mA or so on a 5V NAIS Aromat - would easily be handled by the ULN2003A diode-protected darlington array which does the switching (up to 800mA @ 5V, in fact).

Alternatively, you could use a four pole relay rather than a two pole. Then one of the two extra poles could be used to switch in the third channel. Can't see an issue either way.

Ben and I are working feverishly on the Option 3 pcb at present. This is a difficult pcb to do single-sided, and will take some time. I normally count on at least five iterations, sleeping on it for a couple of nights between each iteration. This gives a better outcome; pcb layout is tricky and involves the image oscillation of optical illusion. It takes time to envisage all the images!

Cheers,

Hugh

wireburn · « **Reply #7 on:** 27 Mar 2003, 09:22 pm »

HAPPY DAY! SIGN ME UP!

I certainly don't want to rush you, but can you give a hint on when the Option 3 will be available?

Thanks,
-Mike

AKSA · « **Reply #8 on:** 27 Mar 2003, 11:20 pm »

Hi Mike,

A little tricky to predict. We have timelined six to ten weeks, depending on the following:

1. PCB design.
2. Prototyping and final draft.
3. Sourcing.
4. Photography
5. Documentation.

After pcb design, the uncertain phases are sourcing and documentation. These are the big ones. Documentation is likely to run to 35 pages, and at least 20 photos/diagrams. With maybe 12,000 words, this takes time. I try to write it so that someone with minimal experience can learn the jargon and do the assembly and double checks as he goes. Some of my customers have not build before, and this is quite a tall order.

As I indicated in my NEWS section on the website, I may choose to offer Option 3 only as a fully built up, retail product, so if you want a kitset, there might only be a finite window of opportunity. All reports are that this preamp beats most of the big guys, and I need to make a little more money than DIY to expand. R&D is quite costly and I'm getting REAL tired.....

Cheers,

Hugh

wireburn · « **Reply #9 on:** 28 Mar 2003, 11:45 am »

Interesting! I can wait as long as it takes, as I can still languish in the sound of my AKSA 55's.

Do you think you'll be outsourcing the build to a factory of some sort or will you need a few compentent build-to-order types? If the latter, I'd be willing to put together a few for you state-side.

Getting OT here, sorry!

Thanks again, Hugh.

-Mike

fred · « **Reply #10 on:** 31 Mar 2003, 04:53 pm »

I'm confused. Please help me understand the recommended way to integrate a GK-1 Option 3 into my HT system. I want to use my subwoofer both for 2-channel music (using GK-1) and in HT 5-channel mode (presumably including use of the HT bypass).

My sub has only two inputs: theoretically for L and R channels. I currently connect sub-out from my prepro to the "L" input of the sub. I had thought I could connect the Sub-out of GK1 to the "R" input of the sub. But...it sounds like this might not work since the signal is passed through it. My sub would be getting signal on both L and R simultaneously. Not good.

Does this mean Wireburn's circuit is a must?

wireburn · « **Reply #11 on:** 31 Mar 2003, 05:10 pm »

It's not as difficult as I think you're making it seem. You'd hook your sub up to the secondary output of the GK-1 Options 2 or 3 in stereo. The sub should have no problem handling a stereo signal if it has two inputs, which are most likely summed internally. When the HT bypass mode is engaged, the mono sub signal is passed through from your HT processor on the L channel only.

The circuit diagram I posted will likely be implemented by design or would be an easy addition by the builder.

-Mike