Quick Product Poll! Tube Buffer with Volume Control?

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modwright

Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #20 on: 5 Aug 2018, 05:19 pm »
Hi Guys, first of all, any buffer we do will be more expensive and higher performance than a Yaquin unit. I can't compete with Chinese mfg. cost and I won't even try. Not that there is anything wrong with these units, but I am aiming for something to perform at a higher level and will be priced at a higher level.

As to the WFS STP-SE: I am not sure that I would use a digital display. Several reasons for this, but first of all, I would rather not use a digitally controlled attennuator for this. It does appear to be a very well designed and thought out device.

I would prefer to use transformer coupling for balanced output, simply because there are numerous benefits sonicly do doing so.  There is also cost however, for good quality transformers.

I will have to determine how far this design will be taken. There is a broad range between the Yaquin simple tube buffer and WFS full passive/active preamp design.

I will take all of this feedback in mind.  I expect there will be a couple of models, at different price/option levels.

Thanks,

Dan

paul79

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Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #21 on: 5 Jan 2019, 07:00 pm »
Tell you what I would really like.... A world class buffer with not one control at all, unity gain or maybe optional gain points if desired. Single ended RCA in/out and maybe offer another balanced version if desired. Input and output, that's it.

Most of the good DAC's out there now have excellent volume control implementations, but I have yet to hear a single DAC that did not benefit from a good preamp after it. That said, and since volume controls in good DAC's are already excellent, there is a hole in the market for a really damn good buffer between DAC and amps IMO.

Sonically, it must perform perfect at low volume as well as higher volumes, with an organic artifact free midrange. Still have good bass quantity and slam, micro/macro dynamics still obvious, and keeping a full scale performance while very quiet. I wish more products performed good at low volumes. If you can turn down your system and still enjoy it, your room problems diminish greatly.

modwright

Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #22 on: 5 Jan 2019, 10:48 pm »
I have a design right now that fits this bill. It is ultra low in distortion (<.03%). It offers frequency response flat from 20Hz-100Khz. Being a true buffer, it has VERY low output impedance, allowing for excellent interface with any tube or SS amp.

I agree, most DACs already offer good VC's. There are many DACs out there, that have great digital tech, but the analog stages are lacking. I have used the Pro-Ject S2 DAC ($350) as a prime example of this. By itself, the S2 DAC feeding $18K work of 150SE amp in bridge mono, driving Maggie 1.7i's in my office sounds good, but is a bit lean. I then route the same RCA out signal through the tube buffer and everything just fleshes out and sounds fantastic! I mention the fact that I am using this digital front end (DAC/Tube buffer combo) with high end amps and good speakers to illustrate the point that the source does NOT hold the overall system back!

Buffers have a bad reputation, in my opinion, of being a 'tone control', 'bandaid', or other 'additive' sonic device. Many tube buffers intentionally add tube distortion for added warmth. This can be an enjoyable sound, and can also reduce resolution, detail and overall sonics. Pleasant, but not accurate.

I have hesitated to spend the money to develop the enclosure and take the product to production, because I needed to be sure that the demand is there.

I suppose the thing to do is make a small number of prototypes and send them out for Beta feedback.

Any that are looking for what is described hear, and by paul79, please let me know!

What would you expect to pay for:
1) High quality tube buffer, with 1-2 RCA inputs and 1-2 RCA outputs.
2) Optional balanced outs via transformer coupling - add cost.
3) Including a linear power supply, 5VDC or other common voltage as required by the Pro-Ject and other DACs with external wall wart supplies.

The ideal would be a base design with optional XLR outs and optional integral LPS.

I have a  design that sounds great! I just need to know that there is a demand. I also need to know what people would expect to pay for such a product, designed nicely, in a compact enclosure with good quality build, but not over-the-top and expensive enclosure.

Thank you all in advance!

Dan

demodisc9

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Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #23 on: 6 Jan 2019, 02:12 am »
Good evening,

Dan,
My thoughts on what folks (me) might spend (my 2 cents). I have been looking to downsize over the past year and am taking a look at the ifi audio itube2, Schiit Saga(as a previous poster commented) and the Mapletree Black Buff. All three of these products sell for between, $349 and $475 (gain is also available/possible for two of them), which for me, if I am really downsizing:), would be the limit.

Personally I am looking for a single RCA input and a single RCA output and any cost savings that may be achieved could be applied elsewhere in the design, while keeping to the price point.

Mike

The Rang

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Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #24 on: 6 Jan 2019, 05:12 pm »
Do we know approximately how much this MW tube buffer would cost?

modwright

Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #25 on: 6 Jan 2019, 07:42 pm »
With power supply for the DAC and unity gain, I was thinking about $500. Fit and finish and options would effect this. It will be Hand Crafted in the U.S.A. and made with good quality parts. It will not be made in china or machine assembled.

paul79

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Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #26 on: 7 Jan 2019, 04:48 pm »
Being scared of sonic compromise, and that my linestage is very good, I would be willing to pay $1500-$2.5K for a really good one. Single ended RCA for my needs.

The benefit to this in my opinion, from an ultra simplistic engineering standpoint, is no extra volume control or anything mechanical mucking up the sound. I think ALL volume control implementations no matter, are a compromise, and if the DAC has a very good one already, this should be all we need.

I would be happy to try out what you have there Dan. If you want to talk, more context, let me know. I have what I believe to be a very resolving system with some of the best digital currently available.

RDavidson

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Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #27 on: 7 Jan 2019, 05:05 pm »
I really like the idea of a very high quality, simple, buffer with single input and dual outputs. No pots or switches in the signal path. Adjustable out voltage would be amazing, but perhaps too complex? This type of buffer would be GREAT for folks, like me, who have a nice DAC with high quality volume control, but need dual outputs to run amps AND subwoofers "direct" from the source. :thumb:
« Last Edit: 7 Jan 2019, 09:07 pm by RDavidson »

modwright

Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #28 on: 7 Jan 2019, 05:15 pm »
I agree with you guys that it should be simple and elegant as far as the signal path goes and connectivity. Adding relays, switches, volume controls all do more to add to the signal path in ways that are not desirable.

OzarkTom

Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #29 on: 7 Jan 2019, 06:07 pm »
Hi Dan,

Is there ever a chance for you to come out with a CD player modded with a volume control? I doubt if anything could ever beat that.

rollo

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Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #30 on: 7 Jan 2019, 06:21 pm »
  Dan if ya asked me I would want a CD player or DAC with a quality analog section of a Class "A" preamp. Then a volume control that gets out the way.
   For digital only systems a no brainer. Buffers mostly suck however if you are designing it another story. I just feel why spend on a buffer buy better components like yours.
   Dan why do we need an analog section in a DAC to begin with ? Cannot one design a DAC that outputs directly to a preamp after
 analog conversion from DAC ?

charles

modwright

Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #31 on: 7 Jan 2019, 07:08 pm »
Hi Rollo and others who have posted, and thank you.

First of all, the analog stage of a DAC/CD/DVD player does a few things:
1) If a current output DAC (common in better DACs) there needs to be a current to voltage stage (I-V) after the DAC.
2) Analog filtering needs to be present to filter out ultra high frequencies.
3) Analog stage gain.

A preamp serves several functions:
1) Input select.
2) Gain/buffer.
3) Volume control.
4)Tone controls in some, but not common these days.
5) Home theater bypass to allow integration of HT product with 2CH Stereo.
6) Possibly phase switching.
7) Possibly balance L/R control.

Today's DACs typically put out 2Vrms analog level in stock form. Most amps reach full power at 1V-1.5Vrms, unless a low gain tube amp or other unique designs. Pass's First Watt designs are necessarily low gain and there are some others that really do want additional gain.

So, a good DAC or player with a good (lossless) volume control and 2Vrms+ of output voltage, can drive an amp directly.

Why add a tube buffer then?

Well, first of all, how good is the digital component's analog stage?
We have been very successful with our tube modifications for the Oppo players and others, because we replace the stock analog stage with our own Class A, all tube analog stage, with zero feedback. Our designs also have low output impedance and can drive long cable runs no problem.

Most digital sources however (there are some exceptions at the much higher end), use standard op-amp based circuits, either single ended or balanced
. Op-amps are inherently feedback based and they are cost-effective to design with. This is not necessarily a bad thing and many sound quite good.

To my ears however, no tubes, no magic!

Using a tube preamp with a SS based digital and even SS amps, works and we have done this for years. Our amps have mostly been SS and our preamps all tube.

However, for a simple system in which your main if not only source is digital, and has a built in volume control, then you don't need a preamp. This is where a tube buffer is ideal IMHO!

Our tube buffer design IS low distortion and does not limit frequency response.

My first intention with this, was to offer another option for lesser cost digital gear, alternative to a full tube modification at higher cost. I started with the Pro-Ject DAC because it offered DSD, MQA and SABRE DACs as well as HP amp and built in lossless volume control, for $350?! In stock form it is good, but a bit lean sounding. I found that when our tube buffer was added to the circuit, performance was tremendously improved, adding body and weight as well as a big 3-D sound stage! Now for this product, we also included a GOOD 5V DC regulated supply. The stock DAC operates from a 5V wall wart supply.

Now obviously, if it makes an inexpensive DAC sound this good, of course it will make a higher end DACs sound much better too. Brands such as Exogal, Mytech and other well respected DAC designs in a similar price range with built in volume control, would all benefit from tube circuitry.

And lastly, while you may change DACs with changes in technology, the tube buffer will never be obsolete. Also, being as how it is a separate unit, it can be used with any digital or analog source for the life of your system.

Ways this could be done:
1) Clean and simple tube buffer, one input (RCA) and two pairs of RCA outs, unity gain, no volume control.
2) Same as above, but add a well regulated linear supply for the source.
3) For balanced systems, a tube and transformer coupled solution would be ideal. At this point, it may be a two box design with external supply.
4) If more gain is needed, transformer coupling could offer +6dB and +12dB gain, without switching or volume controls.

Ultimately the ideal would be a compact, clean and elegant solution with minimal if any controls. It simply goes between your source and amp.

The buffer has the following benefits:

1) Impedance matching between any source and amp, offering a VERY low output impedance, allowing matching to any SS or tube amp.
2) Provides tube tonality and 3-D soundstage to a system without the need for a tube preamp or more costly modification to your source.
3) Optionally also includes an upgraded external supply for your digital source (could also simply be straight buffer).
4) Ultimately offering a big sonic upgrade whilst reducing system complexity (no preamp) and at reasonable cost.


Thanks,

Dan Wright

paul79

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Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #32 on: 7 Jan 2019, 08:25 pm »
Agreed to all of the above Dan. I also agree that most buffers suck, but that is because there are not any good ones.

I for one, have what I believe to be an excellent DAC, but it actually has no output stage. Its output is derived directly off the discrete resistor ladder DAC's. Makes for an ultimately transparent DAC, but it MUST have an excellent preamp after it or the sound is not meaty enough. This is another situation as to why I would like a buffer instead of a more complex line stage. It requires an excellent stage, but does not require a volume control.

My preamp volume is set, and I use the DAC to control volume via remote. Just a wasted feature that I don't need in my all digital system.

MttBsh

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Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #33 on: 7 Jan 2019, 09:13 pm »
I have a nice server based setup with a very good DAC, passive (Tortuga) preamp and class D amp, but no tubes anywhere. I'm thinking a tube buffer would be a good fit, but I'm trying to figure out where the buffer would fit in this system.

I have two RCA outs from my passive pre, one goes to my amp and the other to my subs, so ideally the tube buffer would come before it (between my DAC and preamp) but I'm not sure if that's where it is designed to fit. If the buffer works best between my preamp and amp and has two RCA outs, could I send one of the buffer RCA outs to my subs? Thanks for any clarification!

modwright

Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #34 on: 7 Jan 2019, 09:47 pm »
Hi Paul79, don't you need some gain though? Is your preamp currently acting purely as an impedance matching device or is it providing gain? If the buffer was two-box, with external supply, then transformer coupling could be used to provide passive gain of +6dB to +12dB and the buffer would still serve as interface to the amp, and thus ideal VERY low impedance.

RE MttBsh, being as how the Tortuga is passive, it would REALLY benefit having a tube buffer between the passive and the amp.  It would allow for the impedance matching at the amp.  The two outputs could of course feed both the SW and the main amp.

paul79

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Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #35 on: 7 Jan 2019, 10:05 pm »
If this buffer is executed the way I have in mind sonically, this buffer could even benefit some active preamps too!

No gain required.
It also puts out 1.6V at around 600ohm I think.... Have to verify this. I have ran them amps direct. Very clear, like perfect sounding headphones clear, but no lower mid/upper bass grunt, lacks a bit of scale. It is designed to be used with a very good preamp, for this reason.

I am also strictly single ended all the way. Less is more for this guy.

modwright

Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #36 on: 7 Jan 2019, 10:22 pm »
OK, that makes perfect sense!

The best passive preamp will sound clear and clean, but will lack body and drive. This is essentially what you have, with a very high quality DAC and no means of properly buffering the signal to the amp. The buffering really referring to the impedance matching. A good buffer will have an output impedance of well below 100 ohms. Clearly low enough to even drive an amp with 5K - 10K input impedance. Most amps have a higher input impedance than this.

In addition to the buffering and impedance matching, there is something that tubes add in terms of harmonic texture and sense of space. I am certain that it has to do with how our ears hear and receive the harmonics from a tube circuit.

I was listening to a very good Jazz recording recently, on vinyl, through our tube phono stage (PH 9.0) and the sound of the vibraphone was so palpable and the harmonics (nature of the vibes) was just incredible. SS just seems to flatten these harmonics and this, to my ears, takes away from the 3-D sonic presentation.

paul79

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Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #37 on: 7 Jan 2019, 10:37 pm »
What I think it begs for, is a nice low output impedance, no noise floor, black quiet, and a very high input impedance buffer. Like even 1MOhm.

paul79

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Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #38 on: 7 Jan 2019, 10:42 pm »
Also, even in the most proper situations, a passive can sound magic at one spot, then you touch the darn thing, and life is gone. Not for me. Ok if you want your system to sing at pretty much one volume. I like to have my volume set to several different levels, recording, time of day/night, mood dependent. Buffer please.

modwright

Re: Quick Product Poll! Tube Buffer with Volume Control?
« Reply #39 on: 8 Jan 2019, 01:57 am »
Agreed, a buffer is needed!