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My new tube preamp build

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Comments

  • Yeah but nothing beats the portability of the AccuMASTER device.  I can see myself using it to make sure I'm still standing straight at the bar.  When it hits 45 degrees, it's time to go home. 
    Turn24thtryPWRRYDkennykS7910D1PP1NThumperTom
    My signature goes here
  • Cool looking inlay.  When you glue that up, how do you keep the glue from oozing out the top and messing up the finish?  Your board looks very clean along the edge.
  • Yeah great question.  Not sure if I did it correctly since this is my first try.  The inlay fit was tight, so much so I had to tap it into the slot with a hammer.  I brushed yellow wood glue into the slot and rolled some more glue onto the inlay.  Then I tapped it into place.  Quite a lot of glue squeezed out so I used a damp cloth to wipe everything clean (several times), then a dry cloth.  I clamped it up and let it dry over night. The inlay was sitting proud about a 1/16th so I planed it down.  I still need to sand the whole thing smooth.  I plan on doing that after the wooden case is all glued together.  We'll see.
  •  My compound miter is off both on blade angle and cuts. 

      D1pp1n, I have noticed what you're saying about the rails flexing.  The further the saw is extended, the easier it is to flex.  Whacking the ends of 2x4's for studs, it's no problem, but making longer 10' or so cuts, like needed for building boxes, is a major pain.  The way it locks in place makes it very hard to set so it cuts a straight line.  Get the blade trued with a square and try and lock it down and the guide snaps into place at its preset indent, which is right back where I started from.  Aggravating to say the least.  I've resorted to just marking the wood with a square and cutting along the dotted line.

        Need to find a good, cheap, well built table saw. 

       To get back on subject, powrryd, I need to place an order to PE early next week and need a little more $ to get free shipping.  What can be ordered for the preamp?                      
  • Kb, is there 2 adjustment screws for adjusting tbe stops for vertical angle and left to right zero? Should be on the back some where.
  • To get back on subject, powrryd, I need to place an order to PE early next week and need a little more $ to get free shipping.  What can be ordered for the preamp?                       
    Sorry, I can't answer that.  I haven't finished the prototype yet or even heard this thing.  It will be a couple month process before I would consider releasing a recommended BOM or anything.  I might get this thing together and not like it at all.  It wouldn't be the first time.
  • Kornbread, I spoke in haste.  Here are some parts you can order that could be use for this tube project, a different tube project, or even an amp board project (like the Sure boards), etc.

    Alps volume pot 023-208
    IEC jack with fuse holder 090-443
    Power cord 110-178
    Rocker switch 060-670
    RCA jacks 091-1120
    A knob for the volume pot
    Feet for the case

    These are just examples.  You may like a different style power switch or longer power cord for example.
    ani_101
  • I just ordered a bunch of tubes directly from a Russian vendor.  Their prices were excellent and shipping was only $8.  Excited to hear how they sound compared to the made in USA tubes I already have.  Their website says the usual shipping time to the US is 17 days :)
  • I just did a quick search - are you building the single stage, B+ = 350, Rk = 500 ohm with a 100uf bypass? I'll have to see if I can convert my old VTV 6SN7 SRPP to try this one. That VTV design never really thrilled me, but it could be my PS parts & topology. See what did Craig - you got me tinkering with tubes again.... ;)
  • B+ = 300 - 350
    Rp = 5k
    Rk = 680
    Ck = 1000uF
    Screen strapped to plate with 120 ohm
  • Looks like I need to keep reading that thread. There are over 51 pages, so I would assume they have this design pretty well fleshed out. I'll have scrounge tonight to see if I can find some high wattage 5k resistors in my stash. What are you using for the output coupling cap?
  • Nothing fancy at first, probably an Audyn Q4 2.2uF 400V.  Maybe later try a silver cap or something.

  • Tom I just finished testing my prototype power supply and the results look great!  The NOS Amperex 5AR4 tubes you sent me test the best closely followed by a NOS RCA 5Z4 with the large coke bottle glass.  Dead last was a NOS RCA direct heated cathode 5Y4... huge voltage drop and almost instant full B+
  • I'm glad those tested so well! Are you close to an audio test?

    I was looking through that thread for info on that regulator circuit and saw this sweet chassis. Hard to believe it's DIY. It gives me new ideas for future projects!
    D1PP1NjhollanderPWRRYD
  • Yeah that chassis is awesome!  Wonder if the pistol is a .357 or .44 mag.
  • Are you sure it's not a toy cap-gun?
  • It's obviously a toy gun.
  • I bet that sippy cup is loaded!
  • Is that how you take your liquor, Cheesehead?
  • It's been a while since I've had a chance to work on this project.  Here is what I was able to get done this past weekend.  I still need to finish making the cutout for the IEC power jack/fuse on the back and the front mounted power switch.  I also need to completely sand it then apply some nice finish.

    S7910R-Carpenter
  • Looks great so far! I can't wait to see the finished project. 
  • Thanks Tom.  I hope to have the case fully sanded and finish applied this weekend.  Gonna try spraying semi-gloss lacquer for the first time.  
  • build up with gloss and top coat with semi. You'll get nicer looking chunk of wood.
  • Thanks Roman I'll do that.  I assume lots of very light coats to avoid runs?
  • edited December 2017
    Yep. That's always a good idea.
    Good looking project!
  • Thanks.  I always have a hard time bridling my furvor when spraying paint or finishes.  Light coats look so crappy going on compared to wet coats.  Alas I've had to sand off runs and start over more than once :(
  • I cut to size the aluminum top plate as well as some small hickory blocks that I will glue inside the case so that I have some meat to screw into and attach the top and bottom plates.



  • The case is now officially sanded so I'm heating up my garage so that I can start spraying coats of clear lacquer (gloss Roman ;)  )
  • Just finished applying  the first coat of lacquer, gotta wait to apply the second coat.  Wow three comments:

    1) It looks incredible already!  The lacquer makes the hickory grain "pop" just like shellac always does.

    2) It darkened the mahogany just like I hoped for to give a really nice contrast.

    3) Man this lacquer stinks!!!  I've had to open and purge the garage a couple times to keep the stink from entering our kitchen.

  • Are you using a can or spray gun?  Would there be a fire hazard if enough fumes built up in the garage and, say a compressor kicked on?  
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