Tube amp build (s)

[JohnH]

AU$250 incl postage for 2 transformers = BARGAIN.!!

I had a customer come in with a Lexicon Signature 284 that wanted it modified from USA 120VAC to Aussie 240VAC... Transformer had to be custom made by Voltran in Melbourne... Cost AU$280 plus shipping, and then add my time to fit it (and get rid of some hum issues due dud 25yo caps)... But damn, it is a very nice sounding class A tube amp at the end...

Oof, that is expensive. I feel like transformers are going to provide a world of intrigue and wallet emptying in the near future, ha ha

[jonwhitear]

I built a stereo valve amp several years ago, and got the transformers from Edcor in the USA. Shipping’s takes a while, but at the time the we’re very competitive. Don’t know how they stack up now with the current exchange rate, or indeed if they make units suitable for a guitar amp, but they might be worth checking out.

[JohnH]

I built a stereo valve amp several years ago, and got the transformers from Edcor in the USA. Shipping’s takes a while, but at the time the we’re very competitive. Don’t know how they stack up now with the current exchange rate, or indeed if they make units suitable for a guitar amp, but they might be worth checking out.

Good to know - I'll check them out!

[JohnH]

Just put in an order for some more parts, so am updating the running cost:

$120 for the chassis
$41 for tonnes of wire and resistors
$80 for capacitors
$47 for turret board, stand offs, assorted hardware, and an iec socket

[JohnH]

Have managed to organise a whole set of tubes for Xmas, which is exciting. I still need the transformers and a few other odds and ends before I can start the build, but on track to start mid-Jan when the kids are away.

Also got a new Hakko FX888D soldering station, which is a pretty big improvement on my $20 Jaycar one

[Simon Barden]

Looks great! A worthwhile investment.

[artyone]

In reply to an earlier posting within this thread about matched output tubes they don't necessarily need to be matched and a little research, beyond all the superstition that the world will fall apart if they aren't, is worth the effort.
Basically the criteria for basic matching is really basic and tubes can be all over the place in other ways and even a randomnly picked set of tubes that are at least new and/or NOS new will be close enough together that using them as a pair in a push pull amp ain't at all not a bad idea.
The thing is that the slight mismatch in the proprietary way of matching tubes could actually result in some quite useful sonic characteristics and the more on to it boutique builders will actually put a nice big wire wound pot between either the cathodes in a cathode biased amp or between the negative voltage feed on a... you guessed it, grid biased amp (doesn't need to be a wire wound pot here though as it's just voltage) so that two tubes working at different power levels can be brought a little closer together with the point being equalising the amount of DC sitting on the opposing windings of the primary of a OT.

Look into it as in reality you're already setting up measuring cathode currents and voltages anyway and these possibilities just make it a bit wider what we can do there.

[Simon Barden]

However if the valves are too far adrift, then they could have very different plate dissipation values (unless you compensate for that within the circuit by allowing for individual bias adjustment so they match within normal tolerances), and so quite different power outputs. Which means that the mains hum on the DC to the power valves isn't cancelled out that well, so the amp could put out a lot of hum. You can counter this by better filtering of the DC to the power valves, but this isn't standard.

[McCreed]

Also got a new Hakko FX888D soldering station, which is a pretty big improvement on my $20 Jaycar one

That looks like a good soldering station, and def a step up from a basic "stick"!

If you haven't already, I would recommend getting a chisel tip for it. A pencil tip (usually provided as the stock tip) will still be challenging to heat up the back of a pot no matter how high you set the temp on the base.

FWIW, my station is a 48w Duratech (Jaycar brand) and has served me well for over 10 years. Not as flash as the Hakko (password protected heat setting???) but I think it was $99 back then, up to $119 now.

OK... now go melt some lead!!!

[JohnH]

If you haven't already, I would recommend getting a chisel tip for it.

One step ahead of you! ha ha.

I bought a few chisel tips at the same time, as everyone seemed to recommend them. I got some extra stock tips too, because it's a good size for pedal PCBs.