Need Help Understanding/Optimising a Schematic

[ak_47_boy]

I'm a bit of a noob to this stuff.
The schematic of amp i'm choosing to build is not noob friendly. It has no wattages on resistors, no voltage on capacitors, unnamed tubes, hell i don't even know where inputs and outputs are. If somone would be so kind as to do a little ms paint edit on it i will try to re cad it. I need a suggestion on scematic cad too. I would like to cad in everything so it is complete and working with no fill in the dots.
This is the amp:

http://www.bonavolta.ch/hobby/en/audio/kt88_7.htm

thanks

[316a]

Originally posted by ak_47_boy
I'm a bit of a noob to this stuff.

In that case build something much simpler . A 400watt valve amp is not a good first project . The cost of the output valves , mains transformer and output transformer alone will cost an arm and a leg plus there is the safety and debugging aspect to consider . Buy a book such as Morgan Jones 'Valve Amplifiers' or buy a kit , it will save a lot of hassle

cheers

316a

[nickds1]

Originally posted by ak_47_boy
I'm a bit of a noob to this stuff.
... hell i don't even know where inputs and outputs are.

No disrespect intended but you need to get a grasp on reality. I have a degree in EE, and 25 years of experience, in a mix of tecnologies, and even though I can well understand the schematic and have built a few small valve designs, I wouldn't consider building this one - I'm working my way up through other, less risky, designs.

Apart from the physical risk to yourself and others, you will spend many 100s of dollars and end up with something that, if it doesn't catch fire first, will probably not work.

As another poster has said, get a copy of Mogan Jones' book, and try to learn about that you are trying to do. This isn't Lego, it's not kids stuff, it's dangerous and could easily kill you (or more worringly, someone else)...

[lndm]

This seems to be a Williamson amplifier with cathode followers and multiple output devices.

FWIW, I think that the common implementation of the Williamson is quite reasonable, ie more straightforward to build and sounds good. http://www.xs4all.nl/~ideas/amps/chapt14.html

[ak_47_boy]

Don't worrie. This is why i am asking about this stuff, i could have just built it but there would have been a 50% chance that i messed somthing up. What are those unlabled tubes?

edit: btw i'm reading that link right now

[ak_47_boy]

The scematic is mono but the powersupply can run stereo right?

[Eli Duttman]

For a Stereo amp, you need 2X the B+ current that a mono amp needs.

Build monoblocks or you WILL get a hernia. The "iron" for that circuit is VERY heavy.

The unlabeled O/P tubes are KT88 beam tetrodes.

I, as do other posters, think you are in WAY over your head with this project. There is a GOOD chance you will get yourself killed. Get your feet wet on a simpler, safer, project (possibly a preamp).

BTW, what sort of "Watt Hog" speakers do you have in mind for use with such a powerful circuit?

[Wavebourn]

Originally posted by lndm
This seems to be a Williamson amplifier with cathode followers and multiple output devices.

FWIW, I think that the common implementation of the Williamson is quite reasonable, ie more straightforward to build and sounds good. http://www.xs4all.nl/~ideas/amps/chapt14.html

Looks similar (bubbles with dotted lines inside), but absolutely different devices. Were sir Williamson an engineer actually?

[sorenj07]

for a really really simple circuit to practise on, and that should barely cost you anything (assuming that you had the money for that 400w beast), try this following schem from the acrosound catalog:



very simple, i'd use the hammond 1650E as an output and probably 6SL7's instead of 12AX7's but it's the same idea. power supply could be a 274bx rectified by a 5ar4 feeding a 550uF 385V cap through a 193J. i'm not exactly sure what the load is but it's bound to be under 200ma.

you'd be doing both yourself and us a favor by starting on a small project, yourself so you don't hurt yourself, and us (namely me) so i don't worry about you hurting yourself . don't make me regret giving you that schematic

[tubelab.com]

I took about 1 minute to look at the schematic, and figured out that if built as shown it would melt down rather quickly! The 2uF caps in the bias supply are in backwards. They will not live long, followed by death of the 6X4, and then all of the KT-88's due to lack of bias.

If this is fixed, and there are no other mistakes in the schematic, the design would require a matched set of 10 output tubes. They all run off the same bias supply with no individual adjustment provisions. This would reasonably well matched tubes. The tubes that are made today are nowhere near matched enough to use without a selected set. 10 matched KT88's alone could cost $300 USD at least, the OPT another $250, and the power transformer another $150. This will easilly be a $1000 per channel amp.

As stated by everybody else, this is not a first time build. It would take some experimenting to get it to work. The chances of success are not great, and the cost of the build is high. Spending a bunch of time and money on a project that never works will kill enthusiasm for a new hobby rather quickly.

I have seen many people quit this hobby for this reason. I have bought a few of their projects cheap, just for the transformers. I started building tube amps in 1965, and I still make amps that I wind up tearing down.

You will (hopefully) learn by building amps, and get ideas about how to do it better next time as you go along. Find a suitable amp for your first build. It should be a design that has been built by other people. Build it exactly as shown. This will allow for a high probability of success. Then modify the **** out of it. Learn what makes it sound better, and what makes it sound bad. Blow it up a few times (you will figure this out on your own), and learn how to fix it. Then you can tackle a more complicated project. If you built that monster amp, and it didn't work, how are you going to know if you made a mistake, or it was a bad schematic?