New Preamp: LS 100 and Options!

hrcapers · « **Reply #60 on:** 8 Oct 2010, 04:36 pm »

Sorry, I should read more carefully. If I remember correctly, in my modded XA-777ES, Dan took a feed off the tube output to power the headphone jack. I'd be surprised if the headphone circuit is NOT powered by the 6SN7s. Dan?

modwright · « **Reply #61 on:** 8 Oct 2010, 09:17 pm »

This is actually how it works:

The signal to the headphone circuit IS fed via the tube circuit. The output impedance of the LS 100 tube circuit is 300 ohms. Headphones range from 32-600 ohms generally speaking, with Grados being 32 ohm, Senn's being 600 ohm and others somewhere in between I imagine.

The rule of thumb between low-level (preamp) and high-level (amp) impedance ratio is about 100 x. Thus, our preamp would be ideally suited with amps having a min. input impedance of 3K.

in the case of speakers and amps, there is also a need for a ratio (called damping factor) between output impedance of amplifier and impedance load of speakers. Most SS amps have Zout of MUCH less than an ohm, hence product damping factors of 100-1000+ for SS amps. In the case of tube amps, it is typically much lower and this too attributes to the different control that SS amps have over speakers vs. tube amps.

The headphone is just a speaker, albeit requiring MUCH less power. Our headphone amp produces 1.5W at clipping into a 32 ohm load.

The purpose of the headphone amp itself, is to take the signal from the preamp tube output stage and buffer (amplify current) and provide impedance matching. In our case, we use a discrete FET stage to buffer current and provide the VERY LOW Zout (on par with SS amps) in order to drive headphone loads properly.

The other way that this is accomplished with tube preamps and headphone amps is with output transformers, that allow for impedance matching. I did not experiment with high-quality output transformers for the headphone circuit in our LS 100 because they would have added significant cost to the overall product.

Most mfrs. that add a headphone output, simply add an op-amp to the output of the circuit, which also buffers current and matches impedance, but does so with an inherently feedback-based device. In our case, the circuit is discrete, pure Class A and uses zero feedback.

I believe that this provides a high-quality headphone out as an added feature without significantly raising the product price.

We power the FETs in the headphone amp from the 12V windings of the transformer that power the heaters in the tube circuit. Obviously the headphone amp voltage is separately regulated.

I hope this clears things up.

Thanks,

Dan W.

hrcapers · « **Reply #62 on:** 22 Oct 2010, 07:55 pm »

Just received my RMAF demo today. Looks like I have won the very collectible "HEAPHONE" model lottery.

As far as the sound, all I can say is WOW!!!!!!!!
This replaces a very recognizable and expensive balanced preamp in my system and the difference is very noticeable. Modwright has another winner here. Thanks Dan. Incredible...

dminches · « **Reply #63 on:** 23 Oct 2010, 12:19 am »

You must be further west than I am (east coast) since mine won't get here until Monday.

modwright · « **Reply #64 on:** 26 Oct 2010, 09:03 am »

Thanks hrcapers! I appreciate the positive feedback. The LS 100 is a product that we are all very pleased with at MWI.

Take care and enjoy!

Dan

dminches · « **Reply #65 on:** 4 Nov 2010, 06:04 pm »

Quote from: Marco Prozzo on 23 Sep 2010, 06:17 am

More purty pitchers....

Are those balanced inputs and output on LS-100 or just XLR connectors?

dminches · « **Reply #66 on:** 4 Nov 2010, 06:08 pm »

Quote from: modwright on 10 Jul 2010, 11:20 pm

Compared to our 9.0SE that the LS 100 replaces:

We have added the following:

<snip>

Separate Home Theater Bypass - HT/BP - operable when unit is powered off.

<snip>

This is a very special product and I look forward to people's feedback once we begin shipping next month.

Sincerely,

Dan

I am not home now but for some reason I thought I read in the owner's manual that the unit has to be on for HT bypass.

For anyone who has not had the opportunity to play with this toy, it is a sight to be seen and an equally wonderful sounding unit. and I haven't even had the chance to roll in different tubes yet.

ted_b · « **Reply #67 on:** 4 Nov 2010, 06:21 pm »

No, the XLR's are available so as to use balanced cabling.

Quote from: modwright on 10 Aug 2010, 06:57 am

The LS 100 is not a balanced design, because this is achieved by our LS 36.5. Based on feedback from dealers and distributors however, we will likely make one set of the Main outs XLR, so that balanced cables can be used between the LS 100 and KWA 100.

Because of the unique input configuration of the KWA 100 (as well as KWA 150), both XLR inputs and RCA inputs are transformer input coupled (Lundahl) and thus RCA G is common to XLR -. As such, by making XLR jacks on the LS 100, even though not fully balanced, balanced cables may be used and the effect will be the same as using RCA's.

Thanks,

Dan

dminches · « **Reply #68 on:** 4 Nov 2010, 06:49 pm »

To allow you to use cabling you may already have? There aren't any sonics differences, right?

hrcapers · « **Reply #69 on:** 4 Nov 2010, 07:13 pm »

I'm running balanced cables from the LS 100 to the KWA 150. The only differences that I hear are all for the better

modwright · « **Reply #70 on:** 5 Nov 2010, 03:09 am »

The XLR connectors found on the LS 100 are there for convenience. The unit is still single-ended and they allow the use of balanced cables if you prefer to use them.

Because of the unique way that the inputs of the KWA 100/ 100SE and KWA 150 are designed, with RCA ground common to XLR (-) and transformer input coupled, it will function the same, whether using RCA or XLR cables.

The intent of this design was to take AS MANY of the comments and requests from the SWL 9.0SE as possible and include them in the LS 100:

1) Balance control (defeatable)
2) XLR input and outputs - even if wired SE.
3) Internal phono or DAC option.
4) Headphone Amp - Class A, discrete (no op-amps).
5) Home Theater Bypass (also on 9.0SE and LS 36.5)
6) Power, input select and 12V remote triggers on remote control.

We also improved the sonic design, switched to the 6SN7 tube and made it a more attractive piece.

To answer the other question about HT/BP, it DOES require the unit to be on in order for this function to operate.

Thanks!

Dan W.

dminches · « **Reply #71 on:** 7 Nov 2010, 08:44 pm »

When a preamp like the LS-100 has 2 6SN7 driver tubes does that mean that one is driving one channel and the other is driving the other channel? I really don't understand tube designs so I could be way off.

modwright · « **Reply #72 on:** 14 Nov 2010, 12:11 am »

In this case the two tubes are used one per channel. We chose to use one triode per channel and the other is unused. This gives the advantage of extended tube life as you can swap the tubes one channel for the other and then use the other triode per channel.

We theoretically could have used a single 6SN7, one triode per channel. In the case of our phono board, we do use a single 12AU7 and a single 12AX7 for two gain stages, again, using one triode per channel, per tube.

Thanks,

Dan

denjo · « **Reply #73 on:** 14 Nov 2010, 10:03 am »

Hi Dan

Would there be space in the chassis for BOTH a phono and DAC?
I was recently at your Singapore agent, AudioTrio's, showroom and was mighty impressed with the KWA 100 and LS100 Linestage! They had just arrived that morning and already the sound was something quite special!

Best Regards
Dennis

modwright · « **Reply #74 on:** 16 Nov 2010, 07:09 am »

I'm sorry but there is only room inside for one upgrade option. We will likely at some point, offer standalone DAC and phono, possibly based on our internal designs.

Thank you for your words of support.

Sincerely,

Dan

dminches · « **Reply #75 on:** 11 Dec 2010, 04:20 pm »

I recently acquired a pair of Audez'e LCD-2 headphones and have been listening to them with the LS-100. This combination sounds truly amazing and the LCD-2s aren't fully broken in (at least the cable isn't). I also listened to the LCD-2s with a $600 headphone amp and there was no comparison to the LS-100. As described by Dan earlier in this thread, the LS-100 is also a wonderful headphone amp.

Ern Dog · « **Reply #76 on:** 13 Dec 2010, 04:21 am »

What are the sonic differences of the LS 100 vs 9.0SE ?

vintagebob · « **Reply #77 on:** 13 Dec 2010, 10:09 pm »

I had a group of AC folks over on Saturday for a little DAC comparison. Most of these guys were familiar with my previous system and they were very impressed with the sound quality that the LS100 provided.

For me, compared to my previous preamp, the LS100 provides improvements in sound staging, especially instrument placement. I also like the smooth vocals and overall clarity of the presentation.

If you are looking for a new preamp I would at least hop on the demo tour and listen to the LS100.

Kudos to the Modwright team!

Charles Xavier · « **Reply #78 on:** 13 Dec 2010, 10:19 pm »

Quote from: vintagebob on 13 Dec 2010, 10:09 pm

I had a group of AC folks over on Saturday for a little DAC comparison. Most of these guys were familiar with my previous system and they were very impressed with the sound quality that the LS100 provided.

For me, compared to my previous preamp, the LS100 provides improvements in sound staging, especially instrument placement. I also like the smooth vocals and overall clarity of the presentation.

If you are looking for a new preamp I would at least hop on the demo tour and listen to the LS100.

Kudos to the Modwright team!

Did or when does the tour start ?

Audioclyde · « **Reply #79 on:** 14 Dec 2010, 03:46 pm »

Do the Black Treasure cv-181z's (ie, 6sn7) work in the LS 100, physically and electronically?