From: info@turneraudio.com.au   
      
   On Thursday, 6 December 2012 00:04:34 UTC+11, Alex Pogossov wrote:   
   > "patrick-turner"  wrote in message ne   
   s:0bad46cc-e336-417e-ac98-..... But your statement "Definitely such insulator   
   will give a "wooden" sound -- shallow, flaccid, limp bass." - is utter rubbish   
   because the bass quality of the    
   reformed Jadis is nothing short of spectacular, and sounds like a good 50W   
   amp. *** I was only kidding and teasing. Sorry if you took offence. Probably   
   wood is OK if you do not drive +500V screws near some sensitive grid circuits   
   screws...    
      
   Its usually very easy to choose terminal locations to avoid high PD between   
   connection points that are close. I do it routinely, with whatever board   
   material I use.     
      
   I don't take offense, anyone is free to criticise, and then they should expect   
   my robust defence of my practices. But hardwood ply well sealed with   
   polyurethane varnish IS good enough for amps made in very low numbers by   
   DIYers, or by specialist pp like    
   myself. Its all about HOW one used stuff. In the under-chassis space in the   
   original Jadis they had a small heatsink to dissipate 13Watts from cathode   
   heater regulator, plus a single Rk at about 10W plus other R so total heat   
   under chassis was about    
   25Watts. This doesn't escape easily, so chassis got quite warm and temp under   
   chassis tended to be hot. Moving all hot R to a larger heatsink above chassis   
   meant underchassis is cool as cucumber and nothingis heat-stressed. Nothing   
   hot is used near    
   anything wood. Come back in 50 year's time and all will still be well. Timber   
   was routinely used in oil filled HV transformers.   
      
   But I would not use timber. Teflon is very costly, of course, so I use   
   polysterene sheets or even pieces of kitchen plastic cutting boards, but they   
   are not high temperature material. Only low power circuits can be laid out on   
   them.   
      
   Kitchen cut-board is crap because of low temp melt. Never leave one near   
   hot-plates. But small fragments of board end up in food and I guess they are   
   inert. I have used the same wood cut board I made for 30 years now.    
   Plastic Cut boards Great insulaion, they seem to be polyethylene or polythene.   
   You can't heat it, and screws will loosen, and so I'd never use it. But,   
   polythene is good else where and has extensive apps because its dielectric   
   constant is so low at about    
   1.5.    
      
   Kitchen top laminate used to cover particle board cabinets is available   
   usually in 0.8mmm thicknesses and it you glue several layers together it makes   
   a good phenolic board. Offcuts can often be found in joinery dumster bins. It   
   tends to curl over time,    
   and needs to be stored flat. Some is thicker than 0.8. Using 2 glued with good   
   contact glue well applied seems OK. 1.2mm copper wire tracks can be used with   
   wire hooked under board so lamintions won't come undone. One used to be able   
   to buy 3mm thick un-   
   drilled sheets meant for circuits, maybe you still can, but I ain't seen any   
   around, except what's taken from old gear. Its excellent stuff for small   
   boards and for home made turret strips where strips 15mm wide are cut and   
   mounted on stand-offs. Some    
   shops sell pre-drilled phenolic board to suit DIY circuit boards for SS   
   projects and holes are and 0.1 inch centres to suit opamps etc. Its like the   
   old "biscuit boards" used in countless TVs sets and cheap electronics. Its   
   less than 2mm thick, and    
   brittle, but glued up layers are OK. Now many ppl expect to see fibreglassed   
   resin boards used. Best are 3mm thick, but usually only 2mm is used. Jadis had   
   white fibre glass 2mm usually used for making transformer bobbins. I've used   
   ths too, and its OK.    
   The boards can absorb moisture into fibres, but while kept dry they are OK, so   
   after making a board and parting it, I paint over with varnish including all   
   edges. Making tag trips with strips of fibreglass is doable, but its flimsy   
   like the cheap    
   tagstrips using pressed metal lugs on the thin phenolic biscuit board, usually   
   8 lugs for $2. As long as thay re not disturbed, tagstrips last indefinately,   
   as I have seen in so much old gear. Latest tag strips I bought had Bean   
   Counter metal lugs, and    
   metal lug thickness has suddenly been halved, and what was equivalent to old   
   stuff is now quite inferior, so I won't be buying any more for old radio work.   
   Ther's always some cunt who thinks he's a fukken hero by making a product   
   crummy. I'm no fan of    
   turrets. I have seen many examples where they have become loose, or are on   
   verge of pulling out - even in Quad-II-40, which has terrible board and parts   
   layout underchassis.    
      
   Where you want a terminal to remain forever in a fibreglass or phenololic   
   board or in 5mm hardwood ply, the use of M2mm brass bolts and nuts is hard to   
   beat.   
   No rivetting. Nut on bolt is far more reliable. I've used such to terminate   
   many winding connections from an OPT on a board fixed to the bobbin. Its neat   
   and tidy, and terminals don't losses much with repeat soldering, say for   
   changing load matching of    
   the OPT. In the Jadis, the original had 8 x M4 bolts in a 2mm fibreglassed   
   board for the OPT terminations. But in the revised amp, there is onlt ONE wire   
   which needs to be moved to one of 3 available screws in a wood strip. It'd   
   take years for re-   
   soldering to ruin the wood. The wood withstands the heat OK, and sure, the   
   screw that was tight becomes loose, and easily turned, but no more than that   
   and the course thread retains very strong attachment in the wood. I've got the   
   Jadis set up for max SE    
   PO to occur for 5.3 ohms which suits everyone with speakers with Z above 3   
   ohms, so the termiations won't need to be changed - ever. But some audiophule   
   may well try to change it sometime in the future. They'll whinge and moan and   
   bitch on to their mates,   
    while not knowing what they do, and are likely to get muddled, use 12 ohm   
   terminal, then connect 4 ohm speakers, because well, 4 ohms is less ohms, so   
   it must be easier to drive, and you get more "drive" from "higher" ohm outlet.   
   I cannot guard against    
   idiots.   
      
   Of course if anyone insists on me using teflon, and on anything else   
   "special", then fine, they pay the extra, no problem. Some insisted I use high   
   silver content solder, OK, they have to buy a roll for me. Now we have lead   
   free solder, and I'm not sure    
   if audiophules hate that too. But its everywhere now, and you need a hotter   
   soldering iron it seems.   
      
   Patrick Turner.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)