Building tube amp in wooden box(es) - Page 3 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 31st May 2003, 12:11 AM   #21
diyAudio Member
 
Join Date: Sep 2002
Location: Oregon, USA
Quote:
Does fire hazard mean anything to you at all??
If you ask my wife, you'll get a vehement "Yes!" to that

Yes, of course, that is a concern. I also realized that my PS design which had resistors feeding the output tube's B+ would require some very high powered resistors. I wondered by most PSU designs I've seen fed the output tubes straight from the choke, now I think I know why.

Maybe I'll just spend the money and buy the punches/hole saws I'll need.
  Reply With Quote
Old 1st June 2003, 05:16 AM   #22
Morse is offline Morse  United States
diyAudio Member
 
Join Date: Jan 2003
Location: US for now.....
Hi Frank;

>>>...Does fire hazard mean anything to you at all??...<<<

Good point. Yes that's a valid concern with any DIY electronics no matter of chassis type. For my own personal 'risk/reward' ratio, I'm willing to take the tiny added risk of a wooden chassis with metal mountings for combustables but others may want to delete all wood from their projects (though it breaks the heart of this long time amateur woodworker to type it). That's one reason that I advocate the use of the metal mounting plate for the tube sockets themselves.

Anyway, some other fire hazards to consider are the use of carbon comp resistors in spots where they can fail catastrophically (and burn!) and worst of all the wax coated cotton insulated wire that was used commonly in the good 'ole days. Covering insulation wire in cotton's bad enough - but to soak it in wax just makes your wiring into a candle waiting for a match.....

For all novice woodworkers, another BIG fire hazard is the infamous 'oil soaked rag' - particularly if you're using something like linseed oil. That stuff is a notorious spontaneous combustion hazard!

As far as moisture absorbtion in wood is concerned, I've never been able to measure anything other than "infinity" for resistance on any of my amp chassis. Still, it's best to ensure that no 'live wires' can contact the chassis directly as with any other chassis type.

A good post Frank. Thanks for injecting a little sobriety into the discussion.

All the best,
Morse
  Reply With Quote
Old 2nd June 2003, 05:55 AM   #23
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Blog Entries: 18
Quote:
Does fire hazard mean anything to you at all??
Offcourse it means nothing to an American. They build their houses of wood..
  Reply With Quote
Old 2nd June 2003, 06:04 AM   #24
diyAudio Member
 
Join Date: Sep 2002
Location: Oregon, USA
I just ordered all the parts for my first amp. I decided to play it safe and went with a standard Hammond aluminum chassis, and bought the metal punch kit from Triode Electronics. So my first amp won't be unique and exotic and wooden, but hopefully it'll be a little safer

FWIW, I'll be building the Angela/JE Labs 2A3 SET, the 6SL7 SRPP version.
  Reply With Quote
Old 2nd June 2003, 06:22 AM   #25
Morse is offline Morse  United States
diyAudio Member
 
Join Date: Jan 2003
Location: US for now.....
Hi Saurav;

Nothing wrong with playing it safe. If you want to dress up a plain jane chassis, you could consider some wood side panels. Just go to the local 'big box' home improvement store and pick out a nice stick of the hardwood of your choice.....

By the way, what brand valves you going with? I'm using SovTek 2A3's, Reflektor (Russian NOS, same as SovTek) 6SL7's, and an RCA 5U4GB in my JE Labs 2A3 (I built the 2001 ed rather than the SRPP).

Please let us all know how the SRPP sounds by the way! I've considered trying mine out in SRPP since the rewiring is not really that big a change.

Good luck and all the best on your project!!
Morse
  Reply With Quote
Old 2nd June 2003, 01:54 PM   #26
arnoldc is offline arnoldc  Philippines
diyAudio Member
 
Join Date: Apr 2003
Location: Makati
Send a message via Yahoo to arnoldc
hey saurav, great to hear that. let us know how it progress.

morse, i also built the SRPP 2A3 and one thing that impresses me is that it sounds good from classical to heavy metal i also use Sovtek 2A3, red base RCA 5691 and RCA 5U4G.

one benefit of the JE Labs SRPP 2A3 is that a change in cathode resistor to 1K5 and addition of 1K from coupling to grid and it can now accommodate a 45 it's on Esmillia's site as well.

am still looking for a furniture maker to make my wooden base for my other projects... i might give up though and just use acrylic
  Reply With Quote
Old 2nd June 2003, 03:31 PM   #27
diyAudio Member
 
Join Date: Sep 2002
Location: Oregon, USA
I just bought the tubes that Triode Electronics sells, so I think I have Sovtek everything.

Morse, I've thought about wooden side panels, that should be easy enough to do and look pretty good. I'll probably leave the bottom open, or put something perforated there, so I didn't buy that piece.

How does one calculate gain and output impedance for an SRPP stage? I looked through my Morgan Jones book this morning, and the closest thing I could find that's been analysed is a mu follower. Maybe I should read the Tubecad SRPP article for a third time and see if I understand any more from there.

For those of you who've built the SRPP version, do you have a rough idea of the input sensitivity? My linestage is passive, so I'm a little worried that it won't drive this amp to full output.

Thanks,
Saurav
  Reply With Quote
Old 2nd June 2003, 07:05 PM   #28
Morse is offline Morse  United States
diyAudio Member
 
Join Date: Jan 2003
Location: US for now.....
Hi Saurav;

The SRPP Deconstructed article is less of a number crunching exercise than it is a treatment of variations on the SRPP theme.

There's actually more than one TubeCad article on SRPP, so the best answer I can give on SRPP design parameters like gain, etc. is for you to look them up at http://www.tubecad.com/may2000/page5.html and following.

Frankly I would not trust myself to type those formulae in by hand, so I just gave the link to the page with 'em! Please note that there's a correction to the formula for finding GM of the SRPP given in the next issue of TubeCad so you'll need to find that in the index of past issues.

You'll do well ordering from Ned; I've bought a LOT of valves, etc from him and never had a problem yet (knock on wood for luck after typing something like that!! ). The SovTek 5U4G rectifier is a beauty in a lovely ST type coke bottle - you'll be very pleased with the cosmetics on that one!!

If you should happen to need to brace the underside of the chassis to better bear the weight of the trafos, you can buy aluminium bar stock cheaply at most any hardware store.

Good luck and all the best,
Morse
  Reply With Quote
Old 2nd June 2003, 07:09 PM   #29
diyAudio Member
 
Join Date: Sep 2002
Location: Oregon, USA
Quote:
Good luck and all the best
Thanks. I finally "took a deep breath and jumped in", so to speak. Let's see how this goes.

Thanks for the link, I'll go browse the Tubecad site for the other articles.
  Reply With Quote
Old 2nd June 2003, 07:16 PM   #30
Morse is offline Morse  United States
diyAudio Member
 
Join Date: Jan 2003
Location: US for now.....
Hi arnoldc;

Thanks for the tip on the mod to use the 45 in that circuit.

Hmmmm, acrylic for a base material?

Will you use a metal top plate then? It's certainly got potential...you might want to draw out some designs and try for an art-deco look with something like that. Have you ever seen the Shanling 2000 CD player?

Maybe you could use a rounded rather than square shaped base? Or perhaps a coloured acrylic in conjunction with an anodized alluminium top plate? You could even combine some mirror polished wood components for a really unique look.

Only real hassle I can think of with all this is that the thermal expansion/contraction cycle might be problematic - in other words, you'll have to allow for the more "mobile" parts to expand freely without stressing out the rest of the chassis. You could take a look at how furniture makers allow for the expansion and contraction in real wood via moisture absorbtion.

Interesting idea, though. Please keep us all posted - I bet it could be a really nice looking amp!

Good luck with it!!
Morse
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Building RH84 SE tube amp. Forsman Tubes / Valves 152 29th April 2012 07:41 PM
Building a Tube Mic Pre Chocolatemotor Tubes / Valves 21 20th April 2004 01:01 AM
help building tube mic preamp rafafredd Parts 1 19th December 2002 05:15 PM
Building First DIY SS or Tube??? d-audi Solid State 10 9th October 2002 08:00 AM


New To Site? Need Help?

All times are GMT. The time now is 06:50 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2