Using Dynakit ST70 in the UK
 

"Jim Lesurf" wrote in message
...
In article . com,
dah wrote:

Thanks for the advice. I couldn't access a computer this morning and
ended up getting a Maplins 200VA transformer. It is nice and quiet in
operation. When fully powered up there is a moderately loud hum from
the speakers which I think is due to the big electrolytic filter cap
and coupling caps. caps. The values of these a
big filter cap consists of 4 caps: 1x 30uF, and 3x 20uF, but rated at
525V.
coupling caps are 2x 0.05uF and 2x 1uF, all at 400V
(transformer also uses 2x 0.02uF at 1000V).
Any suggestions on a UK source for these?

Can you say why you have concluded that all these caps are responsible for
the hum, and thus conclude that all need replacing?

Have you tried using the unit with its inputs shorted? Or checking the
earthing arrangements?

If you have not already done so - it may be worth your while to remove the
caps and check their values before deciding which of them may need
replacing.



I don't know why David hasn't followed this up but he's told me he's 'gone
for it' and fired it up as is - I'm sure he won't mind me quoting this
extract he

"Emboldened by your comment that these amps are built like tanks, I
have just powered up the Dynie again, and fed a source (Technics CDP
and cheapo ss preamp) into minute KEF bookshelf speakers. After a
few coughs and splutters, the little tyke burst into life: sweet,
beautiful, full bodied sound! Like wow, man, far out.

The main filter cap is no longer humming--maybe it needed a source?
It *is still* getting hot, and needs to be replaced for long term
use; I've found a guy called Jan in Germany who does a modern, drop
in replacement for £27 all in. Check it out he http://
www.askjanfirst.com/eindex.htm"


I had told him 'It's a Dynaco, just stuff the lecky into it and retire to a
safe distance!' (Or words to that effect!! ;-)

My Mk IIIs are 95% forty or so years old and they will (and do) run all day
long - cracking amps, easily as good as any of the modern stuff I've heard!!

(Summat'll go pop one day and when it does I'll replace it!! :-)

Using Dynakit ST70 in the UK
 

Further update, till the four part big filter cap arrives next week. I
think the hum was due to no inputs. No problem with the 220-110
transformer.

Ran the amp for about an hour on and off tonight, biased the valves
after warmup and after half an hour. Filter cap still running very
hot, so glad that a replacement part is on its way. Still sounds v.
good to me, even amplifying a low quality source. I look forward to
hearing it with a good quality source and valve preamp.

One of the EL34s has a mildly glowing plate. I'll move it to other
sockets to see whether it's the valve or location. No other good
reason why I thought to replace the bias filter caps too, beyond what
I've read on the net. Not intending anything else at present--valve
power amps are new to me, so I'm learning inductively. Thanks for
assistance. David

Using Dynakit ST70 in the UK
 

My memory of restoring a Dynaco is getting dim, since it must be a good
25 years ago. I remember not much space under the chassis. These days I
use Russian teflon coupling caps in all current amps - cheap on ebay
and sound very good indeed, but they are pretty big. Polystyrene is
another nice coupling cap, made by LCR
or Phone Work: (+44) 0 1495 307070. I
haven't tried these exact ones, but have used polystyrene in the past
and it sounds very good, plus is smaller so fits better in
restorations.

There's some interesting stuff on www.audioasylum.com about using 6B4Gs
in this, instead of EL34. Do a search and you should find quite a few
posts - it's a mod that has been well tried.

Using Dynakit ST70 in the UK
 

"Andy Evans" wrote in message
oups.com...
My memory of restoring a Dynaco is getting dim, since it must be a good
25 years ago. I remember not much space under the chassis. These days I
use Russian teflon coupling caps in all current amps - cheap on ebay
and sound very good indeed, but they are pretty big. Polystyrene is
another nice coupling cap, made by LCR
or Phone Work: (+44) 0 1495 307070. I
haven't tried these exact ones, but have used polystyrene in the past
and it sounds very good, plus is smaller so fits better in
restorations.

There's some interesting stuff on www.audioasylum.com about using 6B4Gs
in this, instead of EL34. Do a search and you should find quite a few
posts - it's a mod that has been well tried.




Andy, you appear to be replying to me - I ain't got no ST70, I got MkIIIs
and they're a 6550 valve for a start....

Using Dynakit ST70 in the UK
 

Andy, you appear to be replying to me - I ain't got no ST70, I got
MkIIIs
and they're a 6550 valve for a start....

Hi Keith - just joined the end of the chain, that's all. Mk 3s - very
nice. Do you run them in triode?

Using Dynakit ST70 in the UK
 

"Andy Evans" wrote in message
oups.com...
Andy, you appear to be replying to me - I ain't got no ST70, I got
MkIIIs
and they're a 6550 valve for a start....

Hi Keith - just joined the end of the chain, that's all. Mk 3s - very
nice. Do you run them in triode?



No, I don't use them very often (due to be somewhat over-amped) but they are
completely 'stock' and are living proof that amplification has gone
*nowhere* in half a century!! ;-)

.....if you go by the sound and ignore the *figures* that is....

Using Dynakit ST70 in the UK
 

Keith G wrote:
"Andy Evans" wrote in message
oups.com...
Andy, you appear to be replying to me - I ain't got no ST70, I got
MkIIIs
and they're a 6550 valve for a start....

Hi Keith - just joined the end of the chain, that's all. Mk 3s - very
nice. Do you run them in triode?



No, I don't use them very often (due to be somewhat over-amped) but they are
completely 'stock' and are living proof that amplification has gone
*nowhere* in half a century!! ;-)

.....if you go by the sound and ignore the *figures* that is....





Even going by the figures *that matter* there hasn't been a lot of
progress. Once an amplifier can produce 20-20kHz +- 3dB at less than
0.1% distortion and with noise -80 to -90dB, any improvement in the
numbers won't be audible.

However, there has been *some* progress:-

Power outputs have increased considerably; 50 years ago 10-20 watts was
typical, now outputs over 100 watts are commonplace, and with much
better current delivery, and a lot better reliability. Of course that's
of little interest to horn/SET users.

Price has come down very significantly. In 1968, a Rogers HG88 15 watt
valve integrated amplifier was £ 59.50. This is £ 654.50 today (using
the inflation indicator on
http://www.safalra.com/other/cumulative-uk-inflation/)

A Leak Stereo 30 transistorised 10-15 watt integrated was £ 58.10,
equivalent to £ 639.10 today.

Nevertheless, I concur with Keith's general thrust, that vintage hi-fi
can produce results which stand up very well by today's standards,
albeit, with perhaps rather more care being taken in their use and
maintenance. Much like driving a vintage car, using a vintage camera, or
anything else that was designed at a time when users were expected to
have at least some knowledge of the equipment.

S.

Using Dynakit ST70 in the UK
 

"Serge Auckland" wrote in message
...
Keith G wrote:
"Andy Evans" wrote in message
oups.com...
Andy, you appear to be replying to me - I ain't got no ST70, I got
MkIIIs
and they're a 6550 valve for a start....

Hi Keith - just joined the end of the chain, that's all. Mk 3s - very
nice. Do you run them in triode?



No, I don't use them very often (due to be somewhat over-amped) but they
are completely 'stock' and are living proof that amplification has gone
*nowhere* in half a century!! ;-)

.....if you go by the sound and ignore the *figures* that is....





Even going by the figures *that matter* there hasn't been a lot of
progress. Once an amplifier can produce 20-20kHz +- 3dB at less than 0.1%
distortion and with noise -80 to -90dB, any improvement in the numbers
won't be audible.


Even relative noobies/technical illiterati like me mostly have a suspicion
that audio engineers/designers back in the forties and fifties had a pretty
good idea of which way was up....




However, there has been *some* progress:-

Power outputs have increased considerably; 50 years ago 10-20 watts was
typical, now outputs over 100 watts are commonplace, and with much better
current delivery, and a lot better reliability. Of course that's of little
interest to horn/SET users.



Not at all, even I'm well aware that the power supply is *all* - nowhere
more so than on a SET amp...


Price has come down very significantly. In 1968, a Rogers HG88 15 watt
valve integrated amplifier was £ 59.50. This is £ 654.50 today (using the
inflation indicator on
http://www.safalra.com/other/cumulative-uk-inflation/)


Interesting but I would be tempted to be guided by it....

(Or else I've managed to lose about 2 million quid's worth of Dinky Toys
over the years..!! ;-)



A Leak Stereo 30 transistorised 10-15 watt integrated was £ 58.10,
equivalent to £ 639.10 today.


Actually, that sounds about right...???

Plus VAT of course....



Nevertheless, I concur with Keith's general thrust, that vintage hi-fi can
produce results which stand up very well by today's standards, albeit,
with perhaps rather more care being taken in their use and maintenance.
Much like driving a vintage car, using a vintage camera, or anything else
that was designed at a time when users were expected to have at least some
knowledge of the equipment.


And some skill at using it. I expect the next generation would even struggle
to load a CD into a player....

The mistake a few here make is thinking that, just because something is not
*brand new*, it's no longer fit for purpose - wear and tear
notwithstanding....

Using Dynakit ST70 in the UK
 

"Keith G" wrote


Price has come down very significantly. In 1968, a Rogers HG88 15 watt
valve integrated amplifier was £ 59.50. This is £ 654.50 today (using the
inflation indicator on
http://www.safalra.com/other/cumulative-uk-inflation/)


Interesting but I would be tempted to be guided by it....


********, the salient 'not' is missing there....

Using Dynakit ST70 in the UK
 

Much like driving a vintage car, using a vintage camera, or anything
else that was designed at a time when users were expected to have at
least some knowledge of the equipment.

The interesting argument is whether some of the older products were in
fact "better" in some ways. It's not so much that the research and
technology was better - Leica lenses today out-perform previus models
in performance, if by that we mean sharpness - more that certain things
were very well made and their subjective and indeed sometimes objective
quality remains valid (I'm sure we could include some classic cars or
parts of cars). Some users like the older Leica lenses for bokeh,
colour and other subjective qualities. Todays transistor amps as a
whole are better than almost anything available in the 30s, but then
some of the discreet componants like directly heated triodes (e.g. WE
300B) were masterpieces and are collected and used in modern circuits
with modern componants (including loads of ss devices in the circuitry)
right alongside modern equipment. The valves themselves, as discreet
amplifying devices, seem to have survived remarkably well. But then so
have the best old Leica and Schneider lenses, even when camera
technology is miles ahead. So yes, technology marches on but it leaves
in its wake little islands of perfection from past ages.