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Old 1st July 2007, 09:24 PM   #1
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Default 1st Time project - Report 1

Hi folks,

Not sure how much interest exists out there but as mentioned earlier on I am embarking upon my first valve amplifier. I have decided upon a slightly modified version of the Dynaco ST-70. Earlier, I indicated that I would file a progress report so that anyone who was interested could follow my progress. I have found it enormously challenging understanding the concepts and sourcing parts, and I hope that by posting my progress someone following may find the task a little easier. I should mention that most of my initial research was via the internet and by far the most useful information was from this site. I have included references to the suppliers so my trail can be followed. Also, I would be grateful for any mistakes to be pointed out to me before electrocution/fir/explosion/discontinuity of space time continuum!

Anyhow, so far my progress is as follows –

1. I have built a purpose workspace (see attached photo), including multiple power outlets, good light (there are 4 different lights and the overall effect is very bright although this is not really demonstrated in the photo) and an isolation trip switch covering all power outlets (I understand that this does not fully protect against shock!!)

2. Have purchased Morgan Jones’s books on valve amplifiers – building valve amps and valve amps (amazon.com)

3. I have procured some equipment including a decent heat controlled soldering iron, a Phillips multimeter/oscilloscope and a fluke multimeter. I have also included a fire blanket and extinguisher.

4. I have bought some basic essentials, good solder with 2% silver and a melting point of 290 degrees.

5. I have sourced all of the caps and resistors (from Jaycar in person and Farnell on-line)

6. I have just received the output and power transformers from Triode electronics (online) – they provided a great service BTW.

7. I am in the process of ordering 18 AWG solid cloth covered wire in 6 colours from Radio Daze and these guys seem really helpful as well (online)

8. I have designed the layout, made a cardboard mock-up and taken this to a local sheet metal worker – after invaluable advice from the forum I decided upon aluminium 3mm on top and 2mm everywhere else.

Anyhow, enough for now. I will post again when I have made some more progress.

Cheers,

Rob
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Old 1st July 2007, 10:59 PM   #2
Klimon is offline Klimon  Belgium
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Quote:
I have also included a fire blanket and extinguisher.
Don't forget to include a life jacket and spare parachute in case your amp crashes over the open sea!!! (couldn't resist)

Seriously: looking very nice; have fun at your new working spot and keep us posted!

Simon
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Old 2nd July 2007, 03:38 AM   #3
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wow - fire equipment - you are either over-prepared or under confident!!! Good luck with this first go. I have been a lot more conservative in my first attempt. I bought around seven old console stereos, stripped them out and retained the trannies, valves, speakers and very little else, then used a random SE 12AX7 / EL84 design to build four little amps for the kids. I figure the indentical layout gives me an opportunity to side by side compare tweaks, it cost me around $5.00 NZ for each of the donors, I get to try out some different speaker enclosures as a side project and the kids get amps that don't go "booom booom booom" in the room next to me. HEehehehehehehe. Oh, a cheapo DMM, a $12.00 soldering iron, $15 of sheetmetal and $15 of perspex rounds out the investment... Looking forward to your next post as you get into the build - your amp is likely to look a little more professional than my effort!
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Old 2nd July 2007, 07:12 AM   #4
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Well I was preparing with a quote from Morgan Jones's book in mind - 'when I first power up an amp, I expect it to explode, catch fire or both'! Besides, my wife would never forgive me if I burnt the house down.
I will keep you posted and thanks for the comments.
Rob
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Old 2nd July 2007, 08:22 AM   #5
EC8010 is offline EC8010  United Kingdom
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Welcome to the forum, let's hope you never have to use the fire blanket or extinguisher; if you're that careful about your preparations, you shouldn't need to.
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Old 2nd July 2007, 12:29 PM   #6
corne is offline corne  Netherlands
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Rob,

Nice workshop.
I like the Lancaster picture. The Lancaster has some very good audio valves (PT15s in the T1154 transmitter) onboard.
I build both SE and PP amps using PT15s. I've attached a picture of one of the PP PT15 mono blocks I've build.

Corne
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Old 2nd July 2007, 01:20 PM   #7
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Default Every journey starts with a small step

Hi There
i succumed to the fever about one year ago.. my workspace appears as if a bunch of drunk sight impaired interior decorators arranged it, so I am envious of your work space. You are no doubt fastidious and methodical; as for the blanket and extinguisher, good call. Better to have them and not need them I say. (i am the kind of person that wore his seat belt whilst watching a movie at the drive in).
You may well need some rosary beads depending on your religious leanings to help you in times of Tube conflict. Valium may also help... lithium is better if the problem cant be fixed by the 7th attempt. I think Farnell may even sell it!!
There is one thing i can tell you that makes it all worthwhile.. when you marvel at the sound of a tube amp(s) and how people who know little of them comment on how good the music sounds. To know your amp began life from planks of wood and sheets of aluminium to the glowing beauty that sits before you is a pleasure that is highly rewarding to say the least.
May all your projects fire up (pardon the ominous pun) first time and good luck.
The road i chose is very steep but boy i like the view
Regards
Nick.
ps. This forum is full of great and helpful people.. without diy audio...who knows where i would be.
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Old 2nd July 2007, 05:15 PM   #8
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Rob....that workshop is way too tidy...

richj
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Old 2nd July 2007, 07:52 PM   #9
jduffy is offline jduffy  United States
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Rich, I like the tilt of the chassis when you're working on it. Are you using an easel?

I always come up with something involving blocks of wood and packing tape. Pretty ugly but it works, usually!
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Old 2nd July 2007, 09:08 PM   #10
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Quote:
Originally posted by jduffy
Rich, I like the tilt of the chassis when you're working on it. Are you using an easel?


Yup...no other way with the big game.....50kg iron and plenty of glass plus a stiffened bench (no use kitchen table). The pale green flat bit of the "jenny" screws on to the back plate of the amp with pair M6 Allen machine screws on each end and then one can tilt up. These screws are high tensile. When all is done simply bring down to the normal position then simply unscrew.
A botch-up gizmo for anyone with welding ability can save alot of trouble.

richj
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