Startup Cost?

[thereverend]

Hello,

I am new to the DIY game and I have built a CMoy headphone amp on perfboard and a SOHA based upon a PCB and sourced parts and etc. I am very interested in building a nice line stage like the 12B4 based one I saw in another thread, but I am concerned that the cost will be particularly high, especially with the power supply and etc. I appreciate all advice and I am looking forward to hearing from everyone. Thanks!

Colin

[soundbrigade]

Don't know where you come from, but a few points from my Swedish horizont.
What costs are transformers, tubes and HV caps. I have tried building amps on massive wooden boards (Smorgasboard ) - that is cheap and handy.

I have a big pack of tubes I have picked up in Russia, else I send an order to TubesAndMore.

Transformers, well, I order mains transformer cheaply from a small company nearby. A transformer suitable for a 10W SE (stereo) costs less than $100 (including P&P) - that is cheap in Sweden. A small x-former for a line amp would end up around $50.

O/P are bought from several places, making serious considerations and compromises. I find it better to build two rather good amps instead of one SUPER-amp, though I would once build THE AMP (got a bunch of 6B5G:s ). Here I have sources in Germany and a good supplier in England and of course there're the Hammonds and Edcores.

On caps; I look around and buy just what I need for a specific project, BUT I accidently found caps from German electronic store Conrad - 470uF/450V - marked at $1,50 each. I bought me 15 of these. Will last some time...

I have been looking at a simple 12B4A line amp project myself and I plan not to spend more than $100 in total, but of course I have a pack of chassis I was given, caps, resistors and potentiometers in my drawers.

Some links:
Röhrentechnik - Germany
Welter Audio - Germany
Ask Jan First - Germany
Elettronica Novarria - Italy Mike's Site - England
EDCORE USA - USA
Svebry - Sweden
TubesAnd More - USA Conrad.de - Germany'

[OzMikeH]

Is it worth salvaging the filter capacitors from computer power supplies? these are often 300 or 400V at 200 or more uF

[planet10]

Originally posted by OzMikeH
Is it worth salvaging the filter capacitors from computer power supplies? these are often 300 or 400V at 200 or more uF

and discarded computer monitors...

dave

[DigitalJunkie]

Just about anything with a SMPS,really. (VCR's,TV's,Printers,etc)
They all have atleast one 200/400V cap after the rectifiers.

Just scrapped yet another ATX supply the other day myself.

[Shoog]

PC power supplies caps tend to be 200V.
Monitor tend to be 400V.

Power supplies of around 200V can be created by using back to back transformers (in Europe at least). To get the most out of this type of arrangement chokes are required so you don't lose to much voltage to filtering.

CCS loading allows you to use a 150V power supply where resistive loading asks for 250V, it also generally sounds better.

Old dead integrated transistor amps can make very nice preamp cases, if you aren't wedded to the idea of having those valves on show (which I ain't). Both of my preamps are in old Pioneer cases, they usually come with at least 4 sets of phono inputs pre-mounted to the case

Shoog

[thereverend]

Thanks for the replies. I remember reading that the PS is the most expensive part of the amp. Reading through the 12B4 thread, it seems that there are many ideas about power supplies in general. I am mostly concerned with building a good amp (not the greatest like the second post mentioned) and have trouble filtering through PS preferences in terms of their cost and generally "well-likedness."

[soundbrigade]

And for preamps it is possible to go with two 12V mains transformers piggybacked:
230V:12V - 12V:230V.You get 12V for the heaters and 230V for the supplyvoltage.

[kevinkr]

Small power supply transformers, particularly the much maligned Hammonds are not that expensive. Allied Signal and others still make tube friendly power transformers at reasonable cost. Surplus ones can often be found at Hamfests and on eBay for reasonable money.

High voltage electrolytics are generally under $5 from Digikey or Mouser, I'm not all that enthused about using salvaged caps from computer or monitor SMPS - they don't last forever and have pretty hard lives in their intended applications. ESR after some years of use is going to be much higher than in a comparable new cap.

I avoid salvaged parts with the exception of transformers, film caps, and hardware in my own projects. Still they can be an excellent source of parts for a low budget project if you are careful.

Set yourself a budget, shop around carefully and see how close you can get. It's a challenge! A 12B4 based pre-amplifier should not run you too much. With great care you might do it for less than $100.

Old tube Tektronix scopes often found going into the dumpster at the end of hamfests are a great source for hardware, sockets, tubes (sometimes) and ceramic standoffs.

In Davis, CA you are likely to have a lot of local hamfest activity, I'd track down the local hams and find out. Sometimes they will have tubes and other stuff they will sell you as well.

[thereverend]

All this sounds very encouraging, I will definitely be looking further into this and perhaps start ordering bits and pieces as I move along.