How many watts are really needed?

[nigelwright7557]

Originally Posted by Richard Ellis

Scott:

. There are of course higher powered tube amps but the price seems to increase exponentially.

You could always go for a hybrid amplifier.
I have seen hybrids upto 900watts peak.

[Glowbug]

Originally Posted by analog_sa

It's a great strategy provided you like the way the 100db speakers sound. I haven't been able to find such speakers irrespective of price.

Speakers of that kind of efficiency will also reveal noises farther up the signal chain that you'd never hear with lower-efficiency ones...I know I've gone through some preamps on 96dB/W speakers that other people haven't heard anything wrong with on more traditional designs.

[Shoog]

The real advantage of going for less than 10watts is that you can keep everything in class A without things getting to big and to hot.

Shoog

[boywonder]

Originally Posted by SDB777

I do not have advanced testing equipment(Fluke 88 is all I own and I don't use it very often). My soldering skills are okay(could always use more practice-but then couldn't we all). And I have no problem following schematics.
Are there any things that I would need to 'know' before ordering this kit? Problems, quirks, etc?

You can build a tube amp with a multimeter and a soldering iron. A scope, a function generator, and a variac are nice to have, but not required to get started. An additional multimeter may also be handy when bringing the amp up but not required. You will use the voltmeter to check your B+ voltage and adjust the bias of the output tubes when getting the amp up and running, among other things.

The various ST-70 kits around use different driver topology and tubes, I'm no expert here, but a search will most likely turn up some good info. Again, once built, plenty of tinkering opportunity for trying different driver boards, etc. There is also a dedicated ST-70 forum over at diytube.com :: Index IIRC, there is a kit available for sale over there also.

Use good solder, it makes things easier. There are a few people on ebay selling 20' of Cardas quad-eutectic solder for around $5 shipped, plenty to do a couple of amps. The stuff melts and flows like butter, and you'll be chasing less cold joints later.

It's nice to bring the voltage up slowly when first firing a newly-built project up. Without a variac, you can accomplish this with a lightbulb in series with the power cord. Search the forum for details.

Remember, tubes operate at high voltage, and can be dangerous/lethal. The B+ voltage in an ST-70 kit or similar PP amp is around 400V give or take a little, and this voltage needs to be treated with respect, like using clip leads (highly recommended) on your meter for hands-off testing. If you must probe a live amp always stick one hand in your pocket (use a clip lead on the neg side of the meter). Put bleeder resistors across the HV power supply caps to allow the high voltage to bleed off when the amp is powered down. I imagine modern kits include these.....

Read the sticky on safety at the top of this forum for other tube safety basics.

If you've got a little soldering/electronics experience, an ST-70 kit is a fine first project. It also can be modified over time so it can keep your interest for awhile.

[Glowbug]

Originally Posted by Shoog

The real advantage of going for less than 10watts is that you can keep everything in class A without things getting to big and to hot.

Shoog

No such thing

[Richard Ellis]

""No such thing"" ???
Let me get this right.... your wanting a relative noobie to do an ST-70 kit??
He'll get lost just in the part count! K.I.S.S. Try this one from 'Andreas'" schematics listings.....
Class A, really simple....just to get his feet wet. The idea of running a full PP is just asking for him to get discouraged. Besides.... kits really take away the real "fun", point to point wiring, the layout, dimensions......all the real good stuff.

__________________________________________________ ___Rick....

[Eli Duttman]

Originally Posted by Richard Ellis

""No such thing"" ???
Let me get this right.... your wanting a relative noobie to do an ST-70 kit??
He'll get lost just in the part count! K.I.S.S. Try this one from 'Andreas'" schematics listings.....
Class A, really simple....just to get his feet wet. The idea of running a full PP is just asking for him to get discouraged. Besides.... kits really take away the real "fun", point to point wiring, the layout, dimensions......all the real good stuff.

__________________________________________________ ___Rick....

The OP asked for a kit. He also wants to keep his speakers. The speakers rule low power SE circuits out. More than 1 ST70 has been successfully assembled by somebody "following the dots".

[nigelwright7557]

Nothing wrong with a kit for a first time build.
Even a ready made kit is useful.

At least with a kit/ready built module you get a pro pcb that looks really good.

Some of my point to point builds have been pretty rough even if they have worked !

[SGregory]

The tubelab kits, although not for this application, were a great learning experience for me. Gave me the opportunity to learn how to calculate values, and then see the answer. Most importantly the success at then end.
While I agree P2P is really fun and an adventure, a kit is a good place to start. Too bad George's PP board isn't ready for press yet.

[Loren42]

Originally Posted by Richard Ellis

""No such thing"" ???
Let me get this right.... your wanting a relative noobie to do an ST-70 kit??
He'll get lost just in the part count! K.I.S.S. Try this one from 'Andreas'" schematics listings.....
Class A, really simple....just to get his feet wet. The idea of running a full PP is just asking for him to get discouraged. Besides.... kits really take away the real "fun", point to point wiring, the layout, dimensions......all the real good stuff.

__________________________________________________ ___Rick....

The classic Dynakit kits were about as foolproof as it comes. The new ones are only better.

ST-70 Assembly Instructions

There are an abundance of pictures in the assembly manual. Not much can go wrong.

Add to the fact that the ST-70 has a huge number of followers and the amount of support available for that amp is second to none.