OK so I bought a small valve pre amp project kit from Fleabay. The description insists that I use a 12v AC power supply or it won't work. Problem is all of the power supplies and transformers I have found are all sodding DC. It needs to be a minimum of 1.8 amps. I would prefer more. Any ideas any one?
Remove bridge rectifier from transformer based adapter? Or just buy a transformer (there is no such thing as "dc transformer", they need alternating current to function). Though I doubt it really needs AC, can you post schematic?
Don't have the schematic yet, assume that will come with? http://www.ebay.co.uk/itm/311772613331?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT Noting - Instructions: 6J1 Tube Buffer 0.85 times magnification, connected between the source and before or after class, can effectively filter digital flavor. 1, AC 12V Input: using DC5.5*2.1 socket, AC 12V transformer. Reminder: Can not use DC power input, otherwise it does not work!
This looks promising to me: http://www.ebay.co.uk/itm/220-240v-...882342?hash=item3f7cde49e6:g:P4wAAOSwdGFYttg~
I decided to buy that one, thanks Wolf. Man, AC output power supplies are expensive ! Still, that one was a good price and looks like it will fit the bill nicely
I ran into the same problem. Can't really use DC for valves and solenoids, because they end up being so much harder to open/close for some weird reason. Also, working with audio stuff, AC is probably better anyway. You could use a transformer, but you'd then have to be very careful as you have a power supply with the capability to draw a huge current (although, frankly 1amp is a thousand times as much needed to kill anyway). I don't know how AC-to-AC power supplies work, but it looks like they just use diodes with some passive magic, probably also with an initial step down transformer to galvanically isolate everything. But it's expensive because it's reasonably high power, and because AC-to-AC supplies are esoteric.
Thanks for the info. I will definitely do my research next time. As it stands it will cost me less than £40 for a custom boxed pre amp. When I say custom box I mean like, walnut burr. Brushed gold leaf vinyl. And gold knobs (ooer) So that's not half bad really Will no doubt replace the valves with something better over time.
I wonder if those gold knobs would look good on a cream telecaster? Always surprised at how crummy the switches and knobs are on guitars.
AC is not "better" for audio, you'll be rectifying it to DC regardless. The one you linked is a capacitive dropper supply - basically a capacitor acts as a resistor. Never ever use such powers supply in a non-double insulated device.
I've got one (the knob) on a headphone amp I changed around and modded. It's nice and solid (literally solid metal) and the allen grub screw stops them coming loose. They're quite heavy though.
some wallwarts can be a bit noisy for stuff like this - if yours is, I can build you a bespoke powersupply if you need. if I was getting this I would probably do away with teh wallwart all together and just wire a transformer and some caps into the box with everything else, and then use a kettle lead, would be nice. Plus - the valve will almost certainly be pants if it's from asia, if you want to upgrade anythign in this when you get it, that would be the first thing to look at.
I don't know much about audio tbh, just know that you still get the hum off conventional amps which I thought was from using AC directly (but thinking about it, may just be DC ripple). But goes to show, don't mess about with mains power unless you know what you're doing.
This really should be built by now. Sadly life has gotten in the way, and I have had a ton of stuff to do which has taken my focus away. It shouldn't take long, but I want a clear head when I do it and I've not had one of those for a week or more I did ID all of the components and have set them out like so. I just need a day free to get into it.
Well if you look at the pic above you can see I made a mistake. I have labelled two different types of resistors with "470K". Unfortunately I did not notice until I had soldered and cut two of them so fun ensued trying to get them off without breaking them. I managed it in the end Here is the board with no caps. After I found a reference pic online and sorted the polarity of the caps. As you can see I have used plenty of solder, so hopefully it can continue to work for much longer than my Little Dots did. Both suffered solder failure on the valve holders within 6 months. It then took me a while to figure out the polarity of the power supply. It was not labelled at all so I had to take the plug apart. Thankfully when I did one wire was red and one was black. So I made a gold cable. Which I ain't gonna lie, took longer than making the sodding amp itself. I tried various braiding techniques which all failed, then my braiding tool that Elf so kindly made for me fell apart half way through another attempt and so on. Was worth it though, adds a touch of class for zero pence. I already had the connector left over from when I modded my Bose sub to take a regular amp. Any way, time to test. Phone - pre amp - amp - headphones. I left it running for an hour or so with a cheap pair of cans on it in case it decided to blow up but nope, came through fighting. I then hooked it up to my Graham Slee (once I felt safe) and it sounds gorgeous. The mid range has really sprung to life and I found I did not need to add any EQ at all. I just set it flat in WMP and flat in the Asus control centre and it really adds some dynamics to the sound. What it has also done is boosted the sound of the Asus DX very well. It was kinda low before, so achieving decent volume was OK on some recordings yet on others I would have to drive the amp to about 2 O'clock and push the windows volume slider to 100%. I've now adjusted it all so that I can achieve ear splitting volume (I will give up before the cans do) and run it at around 60% on the Windows slider. Very happy boy. For £10 I am 100% going to build another too. Well, if I can get another one or two of those super cheap PSUs that Wolf found for me. Talking of which, the PSU is awesome. Must be a high quality unit because it's built really well and there is no hum or such like. Deffo want to build more of these. VALVE THE EVERYTHING ! Oh yeah, talking of which... Margo, what valves do you recommend for the best sound quality? I gotta say, these valves do a great job and I can't complain about the SQ at all (maybe because this amp is a MF?) but yeah, better is always better Think I will get creative on the next one and change out the LED colour. Overall? not had that much fun for £10 in eons. I have looked at larger kits, but they are no more complex oddly enough. Everything is just much bigger lol. Will start the shell soon. Need to get some contact adhesive for the laminate (gonna use Evo Stik).
Margo. Wanted your opinion please. Last night I saw this... http://theproaudiowebblog.com/beyerdynamic-a2-review.html And then I saw this... http://www.ebay.co.uk/itm/HiFi-A2-P...e9f57d7&pid=100005&rk=5&rkt=6&sd=272321618079 As well as this. http://www.ebay.co.uk/itm/HiFi-PCM2...store&ssPageName=STORE:HTMLBUILDER:SIMPLEITEM What do you reckon mate? worth a go?
Almost makes me want to break out my old electronics gear. Just need some good project ideas to get me going. Can anyone think of a good use for some old VFD display modules?
