Using Dynakit ST70 in the UK
 

Hi, I have been offline from this group for a while, but would
appreciate some advice on restoring a stock Dynaco ST70 for use in the
UK. Thanks, David

Using Dynakit ST70 in the UK
 

"dah" wrote in message
oups.com...
Hi, I have been offline from this group for a while, but would
appreciate some advice on restoring a stock Dynaco ST70 for use in the
UK. Thanks, David



David is one of my 'offroaders' and offlist I have pointed him to a stepdown
trannie for his 117 Volt Dynaco ST70, mentioned above:

http://www.eurobatteries.com/sitepag...tors-ac-ac.asp


Does anyone here know of any drawbacks or why one of these might not be
suitable for audio use? (I have never used one myself - my Dynacos being
240V....)

My thinking is that it would allow him to retain his original (I hope)
Dynaco power supply trannie...???

(Note the clever 'Brit plug/Yank socket' arrangement on the 16 quid model -
very handy for anyone with similar Yank kit with original power cables/plugs
on it...!!)

Using Dynakit ST70 in the UK
 

"Keith G" wrote in message
...

"dah" wrote in message
oups.com...
Hi, I have been offline from this group for a while, but would
appreciate some advice on restoring a stock Dynaco ST70 for use in the
UK. Thanks, David



David is one of my 'offroaders' and offlist I have pointed him to a
stepdown trannie for his 117 Volt Dynaco ST70, mentioned above:

http://www.eurobatteries.com/sitepag...tors-ac-ac.asp


Does anyone here know of any drawbacks or why one of these might not be
suitable for audio use? (I have never used one myself - my Dynacos being
240V....)

My thinking is that it would allow him to retain his original (I hope)
Dynaco power supply trannie...???

(Note the clever 'Brit plug/Yank socket' arrangement on the 16 quid
model - very handy for anyone with similar Yank kit with original power
cables/plugs on it...!!)

**Forget the 16 Squid model. Not enough grunt. The ST500 should do the trick
though. Other than that, step-down trannies pose no real problems. As with
most things in life, the bigger the better.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

Using Dynakit ST70 in the UK
 

In article ,
Keith G wrote:
Hi, I have been offline from this group for a while, but would
appreciate some advice on restoring a stock Dynaco ST70 for use in the
UK. Thanks, David



David is one of my 'offroaders' and offlist I have pointed him to a
stepdown trannie for his 117 Volt Dynaco ST70, mentioned above:

http://www.eurobatteries.com/sitepag...tors-ac-ac.asp


Does anyone here know of any drawbacks or why one of these might not be
suitable for audio use? (I have never used one myself - my Dynacos being
240V....)

My thinking is that it would allow him to retain his original (I hope)
Dynaco power supply trannie...???

(Note the clever 'Brit plug/Yank socket' arrangement on the 16 quid
model - very handy for anyone with similar Yank kit with original power
cables/plugs on it...!!)

An auto transformer will be fine - but make sure it is adequately rated
for the mains power *consumption* of the amp - not its nominal power
output. The power consumption on a UK device is normally on a plate
somewhere - can't speak for others.

For audio use this range which uses toroidal transformers with minimal
external magnetic field might be attractive.

http://www.tlc-direct.co.uk/Main_Ind...ter/index.html

--
*Change is inevitable, except from a vending machine*

Dave Plowman London SW
To e-mail, change noise into sound.

Using Dynakit ST70 in the UK
 

"Dave Plowman (News)" wrote in message
...
In article ,
Keith G wrote:
Hi, I have been offline from this group for a while, but would
appreciate some advice on restoring a stock Dynaco ST70 for use in the
UK. Thanks, David



David is one of my 'offroaders' and offlist I have pointed him to a
stepdown trannie for his 117 Volt Dynaco ST70, mentioned above:

http://www.eurobatteries.com/sitepag...tors-ac-ac.asp


Does anyone here know of any drawbacks or why one of these might not be
suitable for audio use? (I have never used one myself - my Dynacos being
240V....)

My thinking is that it would allow him to retain his original (I hope)
Dynaco power supply trannie...???

(Note the clever 'Brit plug/Yank socket' arrangement on the 16 quid
model - very handy for anyone with similar Yank kit with original power
cables/plugs on it...!!)

An auto transformer will be fine - but make sure it is adequately rated
for the mains power *consumption* of the amp - not its nominal power
output. The power consumption on a UK device is normally on a plate
somewhere - can't speak for others.

For audio use this range which uses toroidal transformers with minimal
external magnetic field might be attractive.

http://www.tlc-direct.co.uk/Main_Ind...ter/index.html



They are actually the wrong way round - step down is what's needed. (US amp
on UK mains.)

The step down range looks good:

http://www.tlc-direct.co.uk/Main_Ind...mer/index.html

But I've no idea what loading would be required - if the price approached
that of a replacement 240V power tranny it would arguably be not worth the
bother..??

Using Dynakit ST70 in the UK
 

In article , Keith G
wrote:


But I've no idea what loading would be required - if the price
approached that of a replacement 240V power tranny it would arguably be
not worth the bother..??


Can't comment on a specific transformer, but I can add a point to bear in
mind.

As well as the difference in mains voltage, the UK uses 50Hz, not 60Hz.
This means that the smoothing in the PSU has to cope with longer periods
between mains waveform peaks. So check carefully that the result is not a
noticable increase in hum/buzz. I suspect it will be fine as the design is
well regarded, but it may be worth keeping the possibility in mind.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Using Dynakit ST70 in the UK
 

In article ,
Keith G wrote:
For audio use this range which uses toroidal transformers with minimal
external magnetic field might be attractive.

http://www.tlc-direct.co.uk/Main_Ind...ter/index.html



They are actually the wrong way round - step down is what's needed. (US
amp on UK mains.)

Oops. ;-)

The step down range looks good:

http://www.tlc-direct.co.uk/Main_Ind...mer/index.html

Yup - they're also toroidal.

But I've no idea what loading would be required - if the price
approached that of a replacement 240V power tranny it would arguably be
not worth the bother..??

It might also be economic to have the existing transformer re-wound or
another made to the spec.

--
*The most wasted day of all is one in which we have not laughed.*

Dave Plowman London SW
To e-mail, change noise into sound.

Using Dynakit ST70 in the UK
 

"Jim Lesurf" wrote in message
...
In article , Keith G
wrote:


But I've no idea what loading would be required - if the price
approached that of a replacement 240V power tranny it would arguably be
not worth the bother..??


Can't comment on a specific transformer, but I can add a point to bear in
mind.

As well as the difference in mains voltage, the UK uses 50Hz, not 60Hz.
This means that the smoothing in the PSU has to cope with longer periods
between mains waveform peaks. So check carefully that the result is not a
noticable increase in hum/buzz. I suspect it will be fine as the design is
well regarded, but it may be worth keeping the possibility in mind.




Good point, but I suspect they have/had all bases covered - my Mk III
monoblocs (240V UK version) have '117 VOLTS 50/60~' actually printed on the
chassises's/es and there's certainly no hum, unless I tweak the biasing way
off!!

Using Dynakit ST70 in the UK
 

"Dave Plowman (News)" wrote in message
...
In article ,
Keith G wrote:
For audio use this range which uses toroidal transformers with minimal
external magnetic field might be attractive.

http://www.tlc-direct.co.uk/Main_Ind...ter/index.html



They are actually the wrong way round - step down is what's needed. (US
amp on UK mains.)

Oops. ;-)

The step down range looks good:

http://www.tlc-direct.co.uk/Main_Ind...mer/index.html

Yup - they're also toroidal.

But I've no idea what loading would be required - if the price
approached that of a replacement 240V power tranny it would arguably be
not worth the bother..??

It might also be economic to have the existing transformer re-wound or
another made to the spec.



Yes indeed, but if it wuz mine I'd strive to retain the original tranny
otherwise it'll end up like a Riley Pathfinder with a Mondeo engine in it -
might make a lot of sense, but who TF would want it?

Anyway, judging by the pix I was sent:

http://www.apah69.dsl.pipex.com/show/ST70-1.JPG

http://www.apah69.dsl.pipex.com/show/ST70-2.JPG


It looks like it's well rusted in anyway!! :-))

Using Dynakit ST70 in the UK
 

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.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

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.

Using Dynakit ST70 in the UK
 

"Andy Evans" wrote in message
oups.com...
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.



Nice ramble, Andy - 'islands of perfection'...?? I like that!! :-)

Not so sure about the older Leica lenses for *colour* though - a lot of them
are/were uncoated or available in both coated and uncoated versions.
(Stunning for black and white, of course...)