Hi RATs,

OK, I've lurked long enough, time to pony up some $ and get involved.

Am looking for something to get me in to toobs on the cheaper end, am
reasonably handy with a soldering iron, but am somewhat apprehensive
when it comes to playing with several hundred volts required to build my
own and many of the popular kits seem insanely overpriced or difficult
to ship to Australia. Cheap-ass chinese amps all over ePay are looking
interesting, but am not keen to put down a few hundred dollars for
something that's going to be shipped pre-broken that I'll have to try
and fix myself (see earlier comment about playing with electricity).
How does one dip a toe in the water (reasonably) cheaply and with
minimal risk to life & limb.

Suggestions appreciated, links welcomed, flames to /dev/null.

M.

I'd look for one of these good, old, trusty Mullard or GEC schemes involving
tubes like EL84 or ECL82. Voltage is 300V or lower, iron is not so
expensive, power out is 7W or more (which is enough for starting).
Personally, I built a PP amp using just four ECL86 (the 82 is +/- the same):
long-tail phase splitter+gain using the triodes, UL output stages using the
pentodes thru Hammond 1610 OPTs. It is (+/-) the Mullard scheme, but I
removed everything that was not strictly required, ie. feedback loop, extra
gain stage (ECC83), tubed PS and so on.
The result? Well, it sounds, and definitely not so bad. Sure it is not in
the same league of a 211 SE, but it cost like the power cord of a boutique
amp.

Welcome to the Vacuum State!

Fabio



"Mark Lar" ha scritto nel messaggio
...
Hi RATs,

OK, I've lurked long enough, time to pony up some $ and get involved.

Am looking for something to get me in to toobs on the cheaper end, am
reasonably handy with a soldering iron, but am somewhat apprehensive when
it comes to playing with several hundred volts required to build my own
and many of the popular kits seem insanely overpriced or difficult to ship
to Australia. Cheap-ass chinese amps all over ePay are looking
interesting, but am not keen to put down a few hundred dollars for
something that's going to be shipped pre-broken that I'll have to try and
fix myself (see earlier comment about playing with electricity). How does
one dip a toe in the water (reasonably) cheaply and with minimal risk to
life & limb.

Suggestions appreciated, links welcomed, flames to /dev/null.

M.

Mark Lar wrote:

Hi RATs,

OK, I've lurked long enough, time to pony up some $ and get involved.

Am looking for something to get me in to toobs on the cheaper end, am
reasonably handy with a soldering iron, but am somewhat apprehensive
when it comes to playing with several hundred volts required to build my
own and many of the popular kits seem insanely overpriced or difficult
to ship to Australia. Cheap-ass chinese amps all over ePay are looking
interesting, but am not keen to put down a few hundred dollars for
something that's going to be shipped pre-broken that I'll have to try
and fix myself (see earlier comment about playing with electricity).
How does one dip a toe in the water (reasonably) cheaply and with
minimal risk to life & limb.

Suggestions appreciated, links welcomed, flames to /dev/null.

M.

Some of the chinese amps at least look remarkably good.
The measured claims for performance look enticing.
There are better chinese amps than Jolida...
But you take a risk buying anything....

Then there are better tube amps than anything chinese, and thse cost a lot,
ARC, CJ, Jadis,
etc.
Maybe you can buy a s/h thing from Trevor Lees, watch aus.hi-fi,
sometimes amps for sale in Oz appear there.

But regardless of where they are being sold, in the shops ppl
pay a grand or two to get 40 new watts per channel.
But old watts are just the same as new watts.

A client of mine decided to aquire a tube amp at little expense,
and won a bid on Ebay for an ST70 Dynaco
for about usd $250.

His previous purchases of about 4 solid state items were not lucky,
and 3 large power amps had serious faults, and other things he bought
have also needed my repair skills, and he has had a
20% success rate at buying properly working audio gear.
This means that the ST70 now in transit could have a stuffed OPT
and may need an expensive fix, or perhaps since he has had so many lemons
that its time he got real lucky, and finds the ST70 is in mint,
or has been restored or modded sensibly.

It appears to me that Ebay is a clearing house for audio gear
that has problems. Nobody owns up to the problems.
Buyers don't bother to ask, is there a noisy power
tranny, is the fan so noisy can it be heard 5 blocks away?
The seller is coy about the occasional OPT with shorted turns,
so that you get 15 watts from one good channel, but only 3 from the other.
Sure it works, but how come one channel is down a bit, and sounds
like there is no bass......
Ask any repair man like me, are there any horror stories,
Yeah, sure are.

Anyway, he isn't worried, as he is on good terms with me and
I can just about fix any darn thing he buys.
Even after I fix it, the item was still cheap as the alternative
is 15 dB more expensive.

ST70 is a fair entry amp, and lots were made, and lots are bought and sold
in the US.
They usually will need a 110 v step down tranny.
They can be worked on to make them sound better and work better.

Unless you have had some experience, never expect to rewire or rebuild
or build from new any tube power amp.
Even a kitset SS amp is a challenge; its one thing to solder a few parts,
another to get it to work, to measure and trim the operation,
and to find your own mistakes, and for all that you need gear.
Its far better to start with a line stage preamp using a couple of triodes,
and that will take months, but you learn some basics.

Meanwhile, try to borrow a tube amp that is in good order.

The power you need must be established.
If you like heavy metal or rap at neighbour irritating levels,
then don't expect a 20 watt per channel class AB tube amp to do the
business.


Patrick Turner.

I started with a ficher 500c that i restored.
But when you buy in ebay you have to read between the lines.
The guy that sold me the fisher sold it because his father died.
The fisher was stock and i was able to restore it with fisher doc resto
pack.
Nice introduction to tube gear. Not too complex to do.

After that i rebuilt quad II that a friend sold me.

And now i'm in the process to build one from scratch : clearly it is
another story.

I thin if i were you i would buy chines amp at ebay :
http://stores.ebay.com/eAudioguy-Onl...QQftidZ2QQtZkm

And with that starting point i would try to improve it maybe.

Yes!

Mark, the Dynaco Stereo 70 is plentiful and fairly cheap and simple to work
on. The heart of the system is it's trio of xfmrs (1 pwr & 2 opt). If any
of these are bad, replacement$ are availible (but it is best to avoid those
problems).

Patrick hit the eBay nail squarely... ALWAYS ask about every possible
problem you can think of.... and remember, shipping costs extra.
Also, pick an unaltered unit... even if you intend on replacing everything
but the xfmrs.

You will be able to find oodles of how-to articles about revamping this
amp. They'll show you what parts need to be replaced and where to find
them.

You will be able to find kits for replacing everything under the chassis &
on the circuit board. Even a suitable replacement quad capacitor is
availible. Replacement cicuit boards (with or w/o parts already soldered in
place) are also availible.

|||Please don't flame me for even suggesting the following...|||
Variations also exist... many outlets carry modified circuit designs and
even solid-state power supplies. Some cost a bunch and each maker or
vendor thinks his is best, and that he is god of all vacuum tube knowledge.
(newsgroup flame-avoidance system prevents me from listing specific products
or brands... whether they are good, bad or that you should even consider
using one)

Wecome to tubes - enjoy yourself - experience the feel & smell of freshly
electrified skin.

"Fabio Berutti" wrote in message
...
I'd look for one of these good, old, trusty Mullard or GEC schemes
involving tubes like EL84 or ECL82.

(snip)

I agree. Here's the one I like (Mullard 5-10). I built two of them
decades ago.

http://www.bonavolta.ch/hobby/en/audio/el84_7.htm

There's a similar GEC one with, IIRC, a different phase splitter
(conventional single triode, equal anode and cathode resistors.)

Cheers,
Roger

Mark Lar wrote:

Hi RATs,
snip
Yes, I know it's poor form to reply to yourself, but I thought it better
than lots of little replies to everyone.

Thanks all for your input, I've already got a SS amp for annoying the
neighbours, so I'm really after something for when I actually want to
listen to music with.

Since nobody has anything particularly awful to say about chinese amps,
I think I'll probably end up starting with something like this if the
budget will permit:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=5767224 795

If the $ don't work out, I'll look for a classic amp I can demo before I
buy, to poke around in once I'm a bit more experienced.

Off to count the pennies...

M.

It's no sense trying to build anything electronic until you have a
good grounding (no pun intended) in basic electronics. You are only
going to be wasting parts and time. You need to be able to read
schematics, understand DC and AC electricity, signal flow, etc. Some
people can learn out of books, some need tutelage. I would then get
some old electronics-for-hobbyists books from the 50s through 70s and
build some of the simple projects. Lindsay Publications offers a few of
these old books.

You also need test equipment. Not a PC, and not just a DMM. Without an
audio generator, and some sort of scope, I would not even attempt any
project. Suitable gens and scopes are available cheaply enough. I
recommend the HP200 signal generator and either a working 'simple
scope' (an old Heath or whatever) or a NEW basic modern scope if you
can swing it.

I've tried to get Antique Electronic Supply to offer a modern version
of the old Eico signal tracer for years as a kit. I would design it so
it could double as a practice amp (easy to do) and with B+ and clean
6.3DC (heaters or solid state) regulated current limited output for a
little RF front end so you could have a radio.