The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    New product - VTA SP14 preamp

    Share

    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    New product - VTA SP14 preamp

    Post by tubes4hifi on Tue Jan 10, 2012 3:40 am

    somebody had to do it, might as well be me!
    introducing the super performance SP14 preamplifier . . .



    January 10, 2012

    I am very proud to present my best ever preamp, the SP14


    photos and more info posted here



    Let me start with an introduction to this product. This is a major upgrade with many refinements to my previous best SP12 preamp.

    This preamp is NOT intended for the casual listener. This preamp is for those who are NOT satisfied with a $3000 preamplifier.

    This preamp IS intended for those DIY builders who may have already experienced my SP12, or who want the best preamplifier kit available at any price.

    This preamp IS intended for those who want a $6000 preamp but who can't afford that. This preamp built as a kit will total under $1000,

    or I can supply it custom built and ready to use.


    Strong statements? YES! Do I stand behind them? YES!

    I have been building, testing, evaluating, and designing tube preamps for nearly 25 years. Up until last year, my products were aimed at the DIY builder on a budget.

    But my customers have been graduating from budget projects, and my better products have been attracting the attention of non-builders who want a super preamp at a super price.

    So I decided it was finally time to design a cost-no-object preamp. As a lifelong audiophile and electronic design engineer, I have listened to and evaluated MANY high-end products,

    and I can tell you from the inside view that a typical $3000 preamp has about $300 worth of parts inside a $300 chassis. The rest is all mark-up and profit, to pay for expensive

    manufacturing engineers and production lines, massive marketing and advertising expenses, reserves for spare parts, and reserves for warranty work.


    Let's get to a description of what makes this a great sounding product. First, start with a great but simple circuit design that has been proven (my SP12 product).

    Now let's graduate to the bigger octal tubes, that were popular at the peak of tube audio back in the 1950s and 60s. The small common 12AU7 tube used in the SP12

    was derived from the 6SN7 octal tube. Tube fanatics that have been around for more than 10 years, or even better, the ones who were around in the 1950s, know that the

    6SN7 is a much better sounding tube than the 12AU7. And because they are no longer as popular as they were 30-40 years ago, their prices are very reasonable for the higher quality tubes.

    Next, the basic power supply of the SP12 is replaced with a fully dual-mono design. Each channel has it's own B+ and it's own filament supply. This gives better separation between channels

    and lessens the load and interdependence. The B+ power supplies are tube rectified (the ONLY way to go in a tube preamp, none of that solid-state hash) which gives a soft-start

    and simplifies the design compared to a solid-state design, and it also sounds better! Then the B+ is fed to a voltage regulator for each channel that eliminates all variation

    in the supply, and reduces the noise by at least 20db, making for a deep, totally dark background.

    The two filament supplies (one for each channel) use ultra-fast schottky diodes, and then the filament voltage is regulated by a low-noise, low-impedance device that is completely

    isolated from the audio signals.


    Finally, since we aren't worried about high-priced parts, the important signal output coupling caps are chosen by the user.
    On this first build I've added a pair of Russian military surplus K40Y PIO capacitors, which are relatively inexpensive for their performance,
    along with my standard issue SoniCaps, similar to AuriCaps.

    Another capacitor for the next comparison will be Mundorf Silver-Oil PIO capacitors.



    OK class, let's get on with it!!


    The build is here


    pay attention, take notes, and do it right. No questions please until this build is finished!

    ...



    Last edited by tubes4hifi on Sun Jan 22, 2012 12:59 am; edited 1 time in total

    Tube Nube

    Posts : 643
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: New product - VTA SP14 preamp

    Post by Tube Nube on Tue Jan 10, 2012 3:05 pm

    Roy, you've been working over time to bring out some really exciting new products and upgrades over the last couple years or so. Congratulations on this exciting "giant-killer" pre amp.

    Now, before I'm overcome with financial better judgment, I'd like to order one!

    I'll email you to discuss the details!

    -Brenton

    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: New product - VTA SP14 preamp

    Post by tubes4hifi on Tue Jan 10, 2012 7:16 pm

    for those few that didn't get the pics on the webpage, it's fixed now . . . enjoy

    Tube Nube

    Posts : 643
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: New product - VTA SP14 preamp

    Post by Tube Nube on Wed Jan 11, 2012 11:59 pm

    Well i've gone and done it. I pulled the trigger and ordered up one of these pre amps!

    j4570

    Posts : 141
    Join date : 2010-08-30

    Re: New product - VTA SP14 preamp

    Post by j4570 on Fri Jan 13, 2012 8:31 pm

    I wish I wasn't broke. I'd order a full kit. Just no money for projects like this right now. This looks like a lifetime investment though, and would pay easily in the long run.

    Let's see, if I paid $10 a month,.......hahha.

    Nice looking kit. I was going to rebuild a PAS-3, but I'm almost tempted to sell it, and use it as the base for saving for this.

    skypilot_one

    Posts : 3
    Join date : 2012-01-19

    Re: New product - VTA SP14 preamp

    Post by skypilot_one on Thu Jan 19, 2012 1:53 am

    Where are the specs and phono stage?

    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: New product - VTA SP14 preamp

    Post by tubes4hifi on Sun Jan 22, 2012 12:36 am

    sorry for the delay, I've been without power and internet for a few days.
    I'll be posting more photos of the build, finished the first SP14 preamp on Wednesday and finally got a chance to listen to it today.
    Very nice . . . and it runs really cool, the big tubes have twice as much glass to dissipate heat, and the filaments are running
    at the low end of their 6v range, with power split into 4 separate power supplies (2 B+, 2 filament).
    SPECS? I don't need specs, I need music! I don't have alot of test gear, but I can hear an improvement over the SP12,
    and I've never done any preamp that didn't have flat freq response from at least 10Hz to 100KHz.
    There's only 2 resistors and 1 capacitor in the signal path . . . simple is pure and elegant and sounds awesound when done correctly!
    Status: Mike's is done and shipping Monday, TubeNube's gets started on Monday, and Troy and Jean get their kit's shipped Monday.
    My own SP14 will have to wait a week or two! Then my M70 octal drive monoblocks. SP9 octal kit for James will be ready in about a week.

    Tube Nube

    Posts : 643
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: New product - VTA SP14 preamp

    Post by Tube Nube on Sun Jan 22, 2012 12:51 am

    At the risk of sounding like an adolescent, "Woo Hoo!"


    captn

    Posts : 14
    Join date : 2010-01-17
    Location : Coastal Virginia

    Re: New product - VTA SP14 preamp

    Post by captn on Sun Jan 22, 2012 9:52 am

    Roy, Thanks for the status update. Glad you have power and are back on-line again.

    James

    Tube Nube

    Posts : 643
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: New product - VTA SP14 preamp

    Post by Tube Nube on Mon Jan 23, 2012 1:09 pm

    As I'm about to go for my Monday morning Coffee, I'm thinking Roy's probably sitting at his bench now, coffee already in hand, looking over MY new SP14, soldering iron a smokin', bits and pieces gradually taking their place!

    The anticipation is excruciatingly exciting.

    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: New product - VTA SP14 preamp

    Post by tubes4hifi on Mon Jan 23, 2012 3:45 pm

    2nd page of SP14 build

    OK class, let's get on with it!!

    The 2nd part of the build is here

    pay attention, take notes, and do it right. No questions please until this build is finished!

    Don't ask me how it sounds, it sound great! Any other opinions should not be mine!

    here's a preview interior photo of the finished preamp:
    [/left]

    skypilot_one

    Posts : 3
    Join date : 2012-01-19

    Re: New product - VTA SP14 preamp

    Post by skypilot_one on Tue Feb 14, 2012 8:43 am

    tubes4hifi wrote:

    SPECS? I don't need specs, I need music! I don't have alot of test gear, but I can hear an improvement over the SP12,
    and I've never done any preamp that didn't have flat freq response from at least 10Hz to 100KHz.


    Agh,

    What is the B+ voltage?
    Is it run in class A?
    What type of circuit? SSRP, CF?
    What is the gain?
    Can a phono stage be fit in there and what is the gain of your phono stages?


    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: New product - VTA SP14 preamp

    Post by tubes4hifi on Tue Feb 14, 2012 12:10 pm

    The actual circuit design (schematic) of the SP14 and SP12 are identical, except that the SP14 has it's own pair of filament and B+ power supplies for each channel, plus another separate power supply for the HV tube.
    Due to those extra power supplies the SP14 board is physically about twice as large as the SP12, and thus the SP14 version pretty much fills up the entire chassis, leaving no room to add a phono amp in the same enclosure.
    The circuit design is AIKIDO, a very high quality cascode amp followed by a noise-canceling cathode follower.
    I don't bother to check frequency response below 10Hz or above 100KHz. It's perfectly flat in that range.
    The B+ voltage is not critical, in this design with the power transformers I use (240v)the B+ is regulated at 265v.
    The filaments are regulated at 12.5v The gain using four 12AU7 type tubes is 12db, typical for a line preamp.
    I have 4 different phono amplifiers now (PH6, PH10, PH12, PH14) they all have a minimum gain of 40db which is the industry standard.
    The PH10 has max gain of 45db, the PH12 has max gain of 50db, and the PH14 has max gain of 53db.
    These will all fit within a SP12 chassis but not within a SP14 chassis, since that board is so large.
    There are several reviews of most of these products on this forum and on AudioAsylum and a few other audio forums.
    There's a fairly good one here on my website from a very happy satisfied and repeat customer:
    SP12+PH12 review

    Sponsored content

    Re: New product - VTA SP14 preamp

    Post by Sponsored content Today at 12:32 pm


      Current date/time is Sat Dec 10, 2016 12:32 pm