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In Reply to: thanks rod posted by nigelbetts on December 30, 2003 at 15:03:57:
...I have several circuit ideas (and some tried and true) looking for chasis. This is THE major sticking point right now between my hobby and my girfriend. I unfortanately have no metal working experience, but I have developed several ideas for chasis.Upgrades are a great way to get your feet wet, and a cheapo PAS mod would be a good reference for future activities. But really you will want to go to point to point wiring, better power supply, ect... I would recomend the RCA passive phono stage for this second step. Also I would suggest a full preamp (phono + line) and taking the power supply off board (seperate chasis). Spend some time on the power supply and overbuild it so you can play with lots of tubes. Also get a few B+ taps going, and pehaps a couple of channels. Then put the Foreplay circuit in the first chasis with your RCA phono circuit. I suspect this whole project would run in the $300 range, and would definitely sound nice.
I can certainly help you with the PAS phono stage, little money, good improvement tweaks.
Follow Ups:
i have more access to woodworking machinery than metalwork, although i could possibly get to use a break/bending station(bends custom sheet metal),as towards punching holes--well i have a large hole saw collection/access to a drill press & an old multi sheet metal punch.
anything else in woodworking for me is like scratching my butt(pretty easy) ive been a furniture maker for 20 years.----if you can lay out a chassis design via drafting table or autocad--the chances are i can get it made . a prototype of aluminum could be easier--as alumimum cuts on woodworking machinery.plus jigs & templates can be made for routers & drilling positions, i just need a decent set of drawings thats all.
I live in baltimore,maryland.
thanks again for the info.
feel free to email me.
I recently did up a PAS. I started with a rebuild/refresh of the stock circuitry. Then moved on to some simple mods...removal of tone controls...replacement volume pot...etc. Then I picked up Curcio's boards. If you buy just the boards and source the parts yourself the price ain't bad, especially if you have the tubes already.After the work is all said and done it isn't a PAS anymore. The other thing kept is the power transformer and chassis. A new heater transformer is installed and all voltages are regulated. Enough about the details though. The sound is quite good...good enough to give most any affordable preamp a serious run for it's money(I compared it head to head with a highly modded A.I. M3A and was very pleased with my work). And the work can be done in bits at a time to keep the budget in check.
If nothing else the phono board could be used by itself in another unit if you can supply the right B+. I had auditioned a fully tricked out Foreplay and IMHO it's not even remotely in the same league.
...much, much cheaper. Moreover, I really focused on the power supply and on the phono stage (as I was comparing some at the time). I think the line stage is basically a basket case. Sure you can get a little better performance with it (active loads or diode bias, removal of the tone controls, ect...), but basically your still left with 12AX7's. Sure you can add another tube (which requires a new power transformer), but by this time you are better off building from scratch. I am sure a RCA style passive phono stage into a Foreplay type circuit (also first described in the RCA manual, although not an exact match) will beat the pants off the PAS and many others. The price for this project would be under $250.I am not trying to slam the PAS. I just want to point out that it may be allot easier to scratch build rather than redesigning the PAS. You all know I love to modify things, but a total makeover is really not my personal approach to vintage equipment. Moreover, if this is your intent, you are much better building around the Eico HF-85 which has point to point wiring, more tube sockets and plenty of room.
Take care,
...I live in Washington DC. My email is "drjrb2" at "yahoo" dot "com"
(Hopefully this protect me from the bots).Perhaps we can set something up so that you can hear some of the cicruits we have bee talking about. I have a all out Foreplay, modded PAS, HF-85, Fisher 80C, ect...
Take care,
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