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    Some Questions about VTA Preamps

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    TorontoDave

    Posts : 24
    Join date : 2013-03-18

    Some Questions about VTA Preamps

    Post by TorontoDave on Wed Apr 03, 2013 12:13 pm

    I'm relatively skilled with kit electronics, I've built numerous Nixie Clocks, a ST-120 (thank you Bob), and assorted odds and end around the house. I can read resistor bands, and have a well used and competent solder station.

    Having recently completed my ST-120 build I'm looking at upgrading my sound by adding a good Pre-Amp. My concerns:

    1) On a SP-14 kit is it possible to get a full kit without the Chassis (which is currently on backorder)? This would include the transformers dials, IEC, and input panel.
    2) are the wires on the transformers identified in the accompanying docs?
    3) are the accompanying docs sufficient for someone with a good electronics background (outside of amps) to build?

    Reaching out to anyone thats built one of these - how was it? Is it something an experienced newbie can build?

    David

    sKiZo

    Posts : 1287
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Some Questions about VTA Preamps

    Post by sKiZo on Wed Apr 03, 2013 3:27 pm

    The bait is taken, the hook is set ...

    Got an ST-120 kit in the mail as we speak, and I've also been eyeballing the preamp kits ... so ...




    pigface

    Posts : 70
    Join date : 2011-04-10
    Location : pittsburgh

    Re: Some Questions about VTA Preamps

    Post by pigface on Wed Apr 03, 2013 7:44 pm

    David , My FIRST ever real electronics project was an ST-120 amp . It worked perfectly first plug in and has performed flawlesly since .
    I have since built the SP-14 and PH-15 with only minor build problems. The wireing diagrams are minimal but sufficent to get the job done . You should check out Roy's build pages on the sp-14 pre amp , it will make building it easier . The links are here on this page http://www.tubes4hifi.com/SP14.htm I worried myself for months wondering whether I could build these till I tried , so if a complete newbee can build them someone with some experience should have no problem . There are also a couple SP-14 builds with photos posted on the board here just do a search .

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: Some Questions about VTA Preamps

    Post by tubes4hifi on Wed Apr 03, 2013 9:18 pm

    yes, I sell tons of these preamp kits without chassis, especially right now!! The PCB kit with parts is $269 without tubes.
    Transformers and whatever other parts you want (RCA jacks, switches, IEC filter, etc) all available. Email or PM me.
    Many many customers make their own chassis, or use an existing one, or buy an alternative new one.

    ruffian

    Posts : 43
    Join date : 2010-02-26

    Re: Some Questions about VTA Preamps

    Post by ruffian on Wed Apr 03, 2013 9:55 pm

    My experience mirrors pigface's. I had no problem putting an SP-14 together with my only other practical experience being building a VTA ST70. You should have no problem either. You dont get step by step instructions like with Bob's kits, but Roy's diagram for stuffing the board was more than adequate. Figuring out the transformers took me a while, since Roy's picture essay was made using different trannys. Someone posted pictures using the transformers that I received which gave me the necessary clues to put it together.

    Avinunca

    Posts : 26
    Join date : 2012-04-15
    Age : 59
    Location : Shrewsbury England

    Re: Some Questions about VTA Preamps

    Post by Avinunca on Sat Apr 13, 2013 3:41 am

    David,

    I built a PH15 and then a SP14. These were my first forays into the valve world.
    The builds were mostly straightforward. The pcbs are excellent and parts and instructions very good.
    A couple of things I couldn't figure out I emailed Roy about and he responded quickly.
    It's easy to work out the transformer wiring. I took photos of the wiring schematics on the transformers to help me when they were mounted and less easy to see.
    I bought a variac on EBay to gently power mine up after very careful checks of the build. Fortunately I have more patience than the last time I was building as a teenager.Both kits worked first time except I had a dirty rectifier tube pin on the SP14 (self supplied tubes) which had me thinking a while.
    I made use of photos of the builds on the Roy's website which explianed a couple of things.

    sKiZo

    Posts : 1287
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Some Questions about VTA Preamps

    Post by sKiZo on Sat Apr 13, 2013 11:16 am

    Got started on my ST-120 last night and just about knocked out the VTA board. Little shortcut ... instead of having to deal with all those little plastic bags, I just threw all the resistors into a cup and picked at random as I went along. I mean ... they all look alike, right? Shocked

    What's with the kaboom? There wasn't supposed to be an earth-shattering kaboom!

    *********

    Now I got the bug, also looking at the PH15 and SP14. Problem being, I'm a quad kinda guy. Tried going stereo here in anticipation of a "clean" signal path, but no ... just ain't gonna do it. That leaves me with my Sansui QRX still in the cabinet, and if I'm gonna do that, might as well use that as a pre too, as well as an amp for the rears.

    I do like the idea of a tube stage though. Not long ago, I would have thought it wouldn't be enough to make any difference as I have a decent enough outboard phono now, but that all changed when I got my TubeMagic DAC. That's just one tube, but changes the entire flavor of the output.

    So now all we got to do is get these guys to put together a tube quad kit and a tube DAC, and we're good to go!

    Oh, and a tube expander, and a tube holographic stage, and a tube bass synthesiser, and a ... pig




    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: Some Questions about VTA Preamps

    Post by tubes4hifi on Sat Apr 13, 2013 8:08 pm

    sKIZo - easy solution, you just buy two each SP14 and PH15, and I'll even give you a discount ! Very Happy

    sKiZo

    Posts : 1287
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Some Questions about VTA Preamps

    Post by sKiZo on Sat Apr 13, 2013 10:35 pm

    Czech's in the mail! Along with a Bulgarian who snuck in when I wasn't looking ...

    Here's how I'm feeding my current SS amp ...



    Just your basic "Y" off a tape loop on the quad receiver. I don't expect to have to do anything more than change the cables so they reach the new location up top of the cabinet.

    Rabindu

    Posts : 1
    Join date : 2016-02-13
    Age : 61
    Location : Mississauga, Ontario, Canada

    Re: Some Questions about VTA Preamps

    Post by Rabindu on Fri Jul 29, 2016 4:14 pm

    My first kit build was the ST-120, took my time and double checked every step. The step-by-step instructions are absolutely fool proof and I learned a lot along the way. I also pondered whether I was able to build one of Roy's kits with minimal instructions. The wiring diagrams and the build pix at tubes4hifi are excellent resources to get things figured out. I took the plunge and successfully built a PH16 and an SP14. It's nice to have an all tube system that functions flawlessly.

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