Quick Product Poll! Tube Buffer with Volume Control?

modwright · « **on:** 2 Apr 2018, 11:18 pm »

What do you guys think of the following, in lieu of a full tube mod to a digital source?

Tube Buffer with volume control, ideally remote control.
Two inputs: Simple system with say vinyl and digital source.
Zero gain, low output imepdance for matching with any SS or tube amp.
Low Noise, Low distortion.

Goal: Act as a preamp/passive preamp or volume control while adding BUFFERING, which is the most important part of any preamp!
Mulitple source input and R/C volume act as preamp functions, but without unwanted complexity, circuitry and cost.

This would add tube tone to any system, SS or otherwise.
It would improve the sound of less than stellar digital sources.
Can be used with different digital sources.
Also, being as how it is unity gain, would also integrate into a HT system without the need for a bypass.

Form factor would be medium size, one box.
Finish would be classic ModWright: Elegant, clean and sophisticated.

Cost: $995 as a starting point.

Input welcome!

Thanks,

Dan

mresseguie · « **Reply #1 on:** 3 Apr 2018, 01:25 am »

Hello, Dan.

I'm potentially interested in such a product. However, I'd want to compare it to a tube preamp in order to fully understand each unit's advantages and disadvantages - fortunately for me I'm relocating to the greater Vancouver, WA area soon.

Michael

JerryM · « **Reply #2 on:** 3 Apr 2018, 02:46 am »

What tubes?

Mark Korda · « **Reply #3 on:** 3 Apr 2018, 03:10 am »

Hi Modright,
What you just described is every thing that the Schiit Saga does at under 400 dollars....Mark Korda

oem-wheels · « **Reply #4 on:** 3 Apr 2018, 03:36 am »

how about a line stage / preamp with a sub in/out ?

modwright · « **Reply #5 on:** 3 Apr 2018, 04:23 pm »

Hi and thank you all.

Tubes: 6922

A buffer is actually all that is needed for modern digital sources, where the gain level is high enough. That is why it was suggested to me that this could be a viable product. The tube buffer allows for impedance matching with the amplifier. By adding a volume control and more than one source, it serves as a preamp.

A preamp will typically have gain and impedance matching, more controls and greater functionality overall. However, one of the most important things that a preamp does is offer a LOW output impedance. This allows for better dymamics and body to the music, as opposed to a purely passive attenuator.

Being a tube circuit of course, it also brings the magic of tubes to a system that may be pure SS otherwise.

I will take a look at what Schiit Audio is offering in this regard.

Regarding a SW in/out, what exactly did you have in mind? The ability to control the volume for the SW?

Thanks guys!

Dan

Rusty Jefferson · « **Reply #6 on:** 3 Apr 2018, 07:10 pm »

I very much like tube based preamps/buffers with low output impedance. The iFi buffer improved dynamics with my horn speakers when placed between the passive pre and amplifies. Then I was blown away by the MicroZOTL replacing the pre/buffer. It drove 2 nominally low input impedance SS amps with no problem. Killer dynamics and transparency. Unfortunately, it's not really a preamp, and will pass dc and both my amps are direct coupled, so I don't want to chance using it.

If you can make something as transparent and uncolored as the MZ with low output impedance and a low noise floor, you're going to have something I'd want at that price point.

I appreciate that implementation will probably have more to do with how it sounds than tube selection, but I have been moving away from 6922 based preamps the past couple years, though that wouldn't stop me from trying one. Perhaps the 6sn7/12sn7 could be considered?

I demoed the Tortuga tube buffer last year and was expecting a particular sound from it based on the tubes used (6h30) and was surprised that it sounded quite the opposite of what I expected. It is a good buffer, but was not as transparent as the MZ, and was a little soft on top, though I think many people would like the softened highs.

modwright · « **Reply #7 on:** 3 Apr 2018, 07:30 pm »

OK, thanks.

Dan

oem-wheels · « **Reply #8 on:** 4 Apr 2018, 02:32 am »

"Regarding a SW in/out, what exactly did you have in mind? The ability to control the volume for the SW?"

I'd like to add a subwoofer in my 2 channel system (2.1 really).. For me, I have the Oppo205 (Modwright) and now I feel I don't need my Classe SSP800 processor except for volume control and the subwoofer.. When I listen to cd's and downloads I have it run the through 2 channel output to the Classe's 7.1 bypass where only the volume control touches the signal.. Of course no sub can be added in this configuration.. Oppo says you can't integrate the sub out from the 7.1 output with the 2 channel output.. When I watch movies, I use the HDMI, there the sub comes in.. Classe does the processing there.. If I can get a preamp with a sub then Classe is out.. (While typing this, I'm starting to think its not possible).. Only Parasound that I know of builds a preamp with a sub out.. I guess they have a built in digital crossover that can degrade the sound (????) .. I've read many wishing they can find a preamp with sub.. Maybe get some towers ?? But then I'd lose the advantage that 2 way speakers has over 3 way towers ??? ugh

Rusty Jefferson · « **Reply #9 on:** 4 Apr 2018, 03:24 am »

I'm not sure I understand the sub issue. A preamp/buffer with low output impedance can easily drive the full range amplifier and a pair of self powered subs, or the full range amplifier and crossover/amp for a pair of passive subs (what I use) with dual outputs on the pre/buffer.

oem-wheels · « **Reply #10 on:** 4 Apr 2018, 04:05 am »

so how do you set the crossover between the bookshelf speakers and the sub ? do you let the bookshelf and sub overlap each other ? say between 50Hz and 120HZ region ?

oem-wheels · « **Reply #11 on:** 4 Apr 2018, 04:05 am »

where they both can reach ?

oem-wheels · « **Reply #12 on:** 4 Apr 2018, 04:10 am »

digital crossover between the preamp and the sub and set it at the lowest point the monitors can play ? ha, I think that's it

Rusty Jefferson · « **Reply #13 on:** 4 Apr 2018, 04:26 am »

Quote from: oem-wheels on 4 Apr 2018, 04:05 am

so how do you set the crossover between the bookshelf speakers and the sub ? do you let the bookshelf and sub overlap each other ? say between 50Hz and 120HZ region ?

It depends on preference. I run my full range speakers full range without crossover, and just bring the subs up to meet them at about 60hz.

If you play the speakers at concert level where distortion from the 2 way woofer becomes an issue then you can high pass the 2 ways and appropriately low pass the subs via a crossover, but I personally prefer the first example and like not having an added crossover in the full range circuit.

Either way, a low output impedance pre/buffer can drive the load.

NavyDoc · « **Reply #14 on:** 4 Aug 2018, 08:20 pm »

If it looks and sounds like a Mod Wright product I am interested. I would love to see a high quality analog XO for running a 2.2 music system (stereo subs) with a variable XO point from 50 to 200 Hz (above 80 Hz calls for careful placement, Wayne Parham of Pi Speakers calls them helper subs and they are great for adding extension to speakers with restricted low end).

A single XO point could also work, but not as flexible.

modwright · « **Reply #15 on:** 5 Aug 2018, 12:00 am »

OK, thank you. I will consider adding a XO filter pole to the buffer/follower design.

Dan

eis · « **Reply #16 on:** 5 Aug 2018, 01:02 am »

Your initial thoughts on a simple tube buffer with volume control is exactly the type of device I would be interested in. The addition of a second line out for sub woofers would be icing on the cake.

modwright · « **Reply #17 on:** 5 Aug 2018, 05:46 am »

Thank you for that! I have a couple of very good 6922 based tube buffer designs proven, that are very low in distortion and with exceptional bandwidth. It could easily be configured as you say. This can greatly improve any system and especially digital, without the unnecessary addition of high tube distortion and bandwidth limitation. Most sources have more than enough gain, but there should be a good buffer circuit between the volume control and amplifier input.

The best passive preamps lack this buffer stage which allows for ideal impedance matching between the volume control and amplifier input. Sonically, the lack of a buffer or active preamp stage can make things sound thin and lacking in body.

Thanks,

Dan

RDavidson · « **Reply #18 on:** 5 Aug 2018, 04:01 pm »

I've been a fan of the Wyred 4 Sound STP-SE for a long time, which is essentially a solid state version of what you describe. Aside from its great performance and reliability, I LOVE its versatility (plenty of inputs and outputs including 12v triggers). It is also very easy to use. However, there are 3 things I really don't like about it : 1. It's ugly. It just doesn't look good in the living room. 2. It isn't the standard 17" width which is a little visually odd if you need to stack components. 3. The display is small and hard to read at 8ft + away.

If you can do (most) of what Wyred 4 Sound has done cost effectively, while fixing the issues I've stated, and swap the solid state buffer for tubes, man oh man that'd be one sweet line stage. My guess is that something like this would have to be $2000+, though. Note the Wyred is balanced, so I imagine keeping yours single ended would save a good amount of $$$.

Hope this helps give a sense of the kinds of features and conveniences I'd like to see.

WireNut · « **Reply #19 on:** 5 Aug 2018, 04:40 pm »

A tube buffer is just what I'm looking for to replace my 2 yaqin buffers.
I use one for phono, and one for CD, since the yaqin's only have one input.