That'll Teach Me... (Chinese Valve Amp)
 

Keith G wrote:
"Steve" wrote in message
...

You seem to be in very good hands, Steve:-)
Try to get one of these two gents to trace out the
circuit for you. It might be useful in the future.

Oh, and come back and tell us how it all
turned out. The whole world loves a happy ending:-)

Iain


I visited Nick on Sunday. It took him just a few minutes to identify a
dodgy
resistor



Jammy sod....

:-)





Yep, that was it, just randomly checking things, and I fell on the fault
entirly by chance.

:-)

--
Nick

That'll Teach Me... (Chinese Valve Amp)
 

"Nick Gorham" wrote in message
...
Keith G wrote:



I would be interested in your opinion on the *sound quality* when
you've got it bashed into shape, Nick!





Hopefully that should be tonight. If RS have been as prompt as normal.



OK, good luck with that then!

I subscribe loosely to the same view as M. Jute that, even if
perceptably *lesser*, the sound from the cheepie chinkies is not that
far behind amps costing as much as ten times the price and that the LODR
kicks in fairly harshly thereafter - my cheapo Bez has certainly held
its own against Ray's Glasshouse number with all the top-of-the-range
'audiophile' bits in it!

That'll Teach Me... (Chinese Valve Amp)
 

"Nick Gorham" wrote in message
...
Keith G wrote:
"Steve" wrote

I visited Nick on Sunday. It took him just a few minutes to identify
a dodgy
resistor



Jammy sod....

:-)


Yep, that was it, just randomly checking things, and I fell on the
fault entirly by chance.


Well you'll be pleased to hear that your email diagnosis/fix on the
Bluebell Audios has held up nicely - I was speaking to Tony on the
blower last night and he tells me they are rock-steady (meters) and
sounding absolutely fine!

That'll Teach Me... (Chinese Valve Amp)
 

"Dave Plowman (News)" wrote in message
...
In article ,
Keith G wrote:
One thing people seem to overlook is that, disregarding the innards
entirely for the moment, you couldn't get the *casework* for anything
like the price of these amps and I believe this particular amp even
comes with a remote control?

Same applies to any mass produced piece of audio gear.


True enough - I've lost count of the sodding remote controls here....

:-)

That'll Teach Me... (Chinese Valve Amp)
 

"Keith G" wrote in message
...

"Nick Gorham" wrote in message
...
Iain Churches wrote:
"Steve" wrote in message
...

Thanks to you all for advice/support.

In particular, thanks to Martin and Nick for offers of help in fixing
the amp, I've emailed them to arrange a consultation.

Steve



You seem to be in very good hands, Steve:-)
Try to get one of these two gents to trace out the
circuit for you. It might be useful in the future.

Hmm, not too keen to do that :-)

http://hi-end.on9mart.com/products/a...8-photo_13.JPG

Oh, and come back and tell us how it all
turned out. The whole world loves a happy ending:-)


One of the 680R 50W ali clad wirewounds in the 300b cathodes had gone
open circuit. Should be replaced tomorrow. Clipping in a 1k (didn't have
680R) it all seems to be ok, so think it was just a failed resistor.

I will give it a quick once over once the R is changed, I suspect that
voltages might be a tad high, dur to the mains being 240v at my place. I
notice the same amp has a mention on rat about killing rectifiers. Seems
ok at the moment.

It seems to drive 300bs hard, the good chan had 70v on its cathode, which
makes it 100ma current, and about 400v on the valve, so not for mesh
plates. It might get better with both chans pulling current though.


I would be interested in your opinion on the *sound quality* when you've
got it bashed into shape, Nick!





Me too, Nick!

Steve

That'll Teach Me... (Chinese Valve Amp)
 

Keith G wrote:
"Nick Gorham" wrote in message
...

Keith G wrote:




I would be interested in your opinion on the *sound quality* when
you've got it bashed into shape, Nick!





Hopefully that should be tonight. If RS have been as prompt as normal.




OK, good luck with that then!

I subscribe loosely to the same view as M. Jute that, even if
perceptably *lesser*, the sound from the cheepie chinkies is not that
far behind amps costing as much as ten times the price and that the LODR
kicks in fairly harshly thereafter - my cheapo Bez has certainly held
its own against Ray's Glasshouse number with all the top-of-the-range
'audiophile' bits in it!




Hmm, well, to me thats saying it doesn't matter what it sounds like. To
my mind phrases like "not that far behind" and "LODR kicks in" is
missing the point. I don't (and never have been able to) see how you can
try and "measure" the subjective difference between the sound of two
amps and try and decide the distance per pound metric, and then invent a
notional DPP value below which its not worth continuing.

The amp in question measures ok, I haven't done any great amount of
objective testing other than it seems to have -3dB points about 20hZ and
40kHz at 1w output, and square waves have a good enough leading edge,
with a bit of damped ringing, say about 4 cycles of what looks about 60kHz.

The biggest problem I can see, is like other Chineese amps I have seen,
this one is designed for 220v mains, on the back it says as much, 220v
+- 10%, so that just covers the 240v mains I have here. AFAIK, the
current UK mains voltage spec is 230V +10%, -6%, so even if thats
adhered to, it could be 6% above what this amp is designed for.

But more important IMHO in this case, is the fillament supply for the
valves, at 220v in, the 300b is seeing spot on 5v, but my 240 gives (of
course) 5.5v on the fillament, this is just too high IMHO, and I
certainly wouldn't suggest putting WE 300b's in it.

The second thing that the meter found, was with one chan not pulling
current the B+ on that chan was over 500v, and the other about 470. With
both pulling current, the B+ dropped to about 430v, and the 680R cathode
resistor was passing just over 100ma, so the valve was disapaiting about
36w which is ok.

It does point to poor regulation of the B+ supply though.

I was unsure just what to say about the subjective sound, its not my
amp, it doesn't have to live up to my requirements, so my views actually
have little merit, but as Steve has asked for an opinion, I will give it.

As far as it goes, it sounds ok, no obvious buzzes (a little hum with
94dB/W/m speakers but it sounds like a clean 100hz, no extra harmonics).
It makes sounds. The general sound isn't the most dynamic I have heard,
but I think thats a bit of a 300b quality when compaired to (say 2a3s
amd PX4s), part of that is the top end is ok, but hasn't the crystal
clear quality that can be had from SET's (though I havn't heard a
commercial one that does that, so maybe its not that common), bass
extension is also ok, but the bass doesn't play that many tunes, and
this is with speakers that present a easy load. Again, I am maybe not
being entirly fair with it, as again I am compairing it against the best
DIY amps I have heard.

The biggest problem I have with it, and this is what to my ears makes
its low price of no importance (sorry Steve, you did ask), it doesn't
seem capable of reproducing music. I am not sure how to describe what
its lacking, and I am not sure how it relates to the terms the mags use
to describe stuff, but what it does is make all the noises that were on
the recording, but somehow, doesn't assemble then in the correct order
to make it sound like music, hard to describe, I think its a lot to do
with the quality of the power supply, I think the lack of a solid B+
voltage means that the dynamic bits are interfeering, so all the leading
edges of the sounds are getting in the way of each other, so it just
sounds like the musicians are not listening to each other, and not
playing in sync, just near but not on the pulse of the music.

Its not just this amp that has this problem, I should say, but for me,
its what made me want to stop using the amp after about a hour. So for
my ears it doesn't do what I would expect an amplifier to do, so it just
doesn't cut it.

It may be that with less dynamic material it would be fine (I was mostly
listening to the Jaco Pastorious solo recording).

In fact, if this was the only SET I had heard, I would be happy to agree
with the description of their shortcommings that some of the more
commercially trained EEs on the NG mention every time the topology is
discussed.

I suspect that I am being rather excessivly crytical of the amp, and
perhaps the above should be viewed in that light, but I can only apply
the same standards I apply to amps I might build myself, or listen to
that others have built. If I don't at least try and have a standard to
compare against, then it makes any attempt to build something that at
least does what I want (even if its not to anyone elses liking) will
never have a hope of success.

There you go, just my 2d worth.

--
Nick

That'll Teach Me... (Chinese Valve Amp)
 

"Nick Gorham" wrote in message
. uk...
Keith G wrote:
"Nick Gorham" wrote in message
...

Keith G wrote:




I would be interested in your opinion on the *sound quality* when you've
got it bashed into shape, Nick!





Hopefully that should be tonight. If RS have been as prompt as normal.




OK, good luck with that then!

I subscribe loosely to the same view as M. Jute that, even if perceptably
*lesser*, the sound from the cheepie chinkies is not that far behind amps
costing as much as ten times the price and that the LODR kicks in fairly
harshly thereafter - my cheapo Bez has certainly held its own against
Ray's Glasshouse number with all the top-of-the-range 'audiophile' bits
in it!




Hmm, well, to me thats saying it doesn't matter what it sounds like. To my
mind phrases like "not that far behind" and "LODR kicks in" is missing the
point. I don't (and never have been able to) see how you can try and
"measure" the subjective difference between the sound of two amps and try
and decide the distance per pound metric, and then invent a notional DPP
value below which its not worth continuing.

The amp in question measures ok, I haven't done any great amount of
objective testing other than it seems to have -3dB points about 20hZ and
40kHz at 1w output, and square waves have a good enough leading edge, with
a bit of damped ringing, say about 4 cycles of what looks about 60kHz.

The biggest problem I can see, is like other Chineese amps I have seen,
this one is designed for 220v mains, on the back it says as much, 220v +-
10%, so that just covers the 240v mains I have here. AFAIK, the current UK
mains voltage spec is 230V +10%, -6%, so even if thats adhered to, it
could be 6% above what this amp is designed for.

But more important IMHO in this case, is the fillament supply for the
valves, at 220v in, the 300b is seeing spot on 5v, but my 240 gives (of
course) 5.5v on the fillament, this is just too high IMHO, and I certainly
wouldn't suggest putting WE 300b's in it.

The second thing that the meter found, was with one chan not pulling
current the B+ on that chan was over 500v, and the other about 470. With
both pulling current, the B+ dropped to about 430v, and the 680R cathode
resistor was passing just over 100ma, so the valve was disapaiting about
36w which is ok.

It does point to poor regulation of the B+ supply though.

I was unsure just what to say about the subjective sound, its not my amp,
it doesn't have to live up to my requirements, so my views actually have
little merit, but as Steve has asked for an opinion, I will give it.

As far as it goes, it sounds ok, no obvious buzzes (a little hum with
94dB/W/m speakers but it sounds like a clean 100hz, no extra harmonics).
It makes sounds. The general sound isn't the most dynamic I have heard,
but I think thats a bit of a 300b quality when compaired to (say 2a3s amd
PX4s), part of that is the top end is ok, but hasn't the crystal clear
quality that can be had from SET's (though I havn't heard a commercial one
that does that, so maybe its not that common), bass extension is also ok,
but the bass doesn't play that many tunes, and this is with speakers that
present a easy load. Again, I am maybe not being entirly fair with it, as
again I am compairing it against the best DIY amps I have heard.

The biggest problem I have with it, and this is what to my ears makes its
low price of no importance (sorry Steve, you did ask), it doesn't seem
capable of reproducing music. I am not sure how to describe what its
lacking, and I am not sure how it relates to the terms the mags use to
describe stuff, but what it does is make all the noises that were on the
recording, but somehow, doesn't assemble then in the correct order to make
it sound like music, hard to describe, I think its a lot to do with the
quality of the power supply, I think the lack of a solid B+ voltage means
that the dynamic bits are interfeering, so all the leading edges of the
sounds are getting in the way of each other, so it just sounds like the
musicians are not listening to each other, and not playing in sync, just
near but not on the pulse of the music.

Its not just this amp that has this problem, I should say, but for me, its
what made me want to stop using the amp after about a hour. So for my ears
it doesn't do what I would expect an amplifier to do, so it just doesn't
cut it.

It may be that with less dynamic material it would be fine (I was mostly
listening to the Jaco Pastorious solo recording).

In fact, if this was the only SET I had heard, I would be happy to agree
with the description of their shortcommings that some of the more
commercially trained EEs on the NG mention every time the topology is
discussed.

I suspect that I am being rather excessivly crytical of the amp, and
perhaps the above should be viewed in that light, but I can only apply the
same standards I apply to amps I might build myself, or listen to that
others have built. If I don't at least try and have a standard to compare
against, then it makes any attempt to build something that at least does
what I want (even if its not to anyone elses liking) will never have a
hope of success.

There you go, just my 2d worth.

--
Nick

What amuses me /irritates in equal measure about all the above is that even
staying with valves, a PPUL EL84 amplifier like the Mullard 5-10 or GEC
equivalent has a little more power than the SET, with a whole lot less
distortion and lower output impedance such that is *does* make music very
satisfactorily, without having to make apologies for the SETs shortcomings.
It would also be cheaper to build as a PP output transformer is considerably
cheaper than a half-decent SET one, and a pair of EL84s cost much less than
a single 300B. The only thing I can think of in a SETs favour is that it
looks a lot more dramatic with those DH big triodes.

S.

--
http://audiopages.googlepages.com

That'll Teach Me... (Chinese Valve Amp)
 

Serge Auckland wrote:


What amuses me /irritates in equal measure about all the above is that even
staying with valves, a PPUL EL84 amplifier like the Mullard 5-10 or GEC
equivalent has a little more power than the SET, with a whole lot less
distortion and lower output impedance such that is *does* make music very
satisfactorily, without having to make apologies for the SETs shortcomings.
It would also be cheaper to build as a PP output transformer is considerably
cheaper than a half-decent SET one, and a pair of EL84s cost much less than
a single 300B. The only thing I can think of in a SETs favour is that it
looks a lot more dramatic with those DH big triodes.

S.


Fine, I didn't set out to amuse or irritate you, but if it does, then
thats not my problem.

I was asked by two people on the ng to post what I thought of the sound
of the amp in question, one being its owner, I did so because of that, I
wouldn't have done so otherwise. Especially as I could have (and still
might have) offended the amps owner.

I don't think at any point I made any apologies for anything's
shortcomings, I just posted my own subjective impressions. I made a
point of specifically describing them as subjective, and being my own.

But somehow, this upsets you enough to feel the need to spout a bunch of
unasked for, unconnected and rather condecending opinions.

Hey, when the owner first asked for help, maybe you should have
suggested he send the thing to the tip, and not to consider that it
could be fixed by replacing a £3 resistor.

I am sure you have saved many of the worlds population from being
corrupted by the existance of certain output device and topology.

--
Nick

That'll Teach Me... (Chinese Valve Amp)
 

"Nick Gorham" wrote in message
. uk...
Keith G wrote:


I subscribe loosely to the same view as M. Jute that, even if
perceptably *lesser*, the sound from the cheepie chinkies is not that
far behind amps costing as much as ten times the price and that the
LODR kicks in fairly harshly thereafter - my cheapo Bez has certainly
held its own against Ray's Glasshouse number with all the
top-of-the-range 'audiophile' bits in it!




Hmm, well, to me thats saying it doesn't matter what it sounds like.
To my mind phrases like "not that far behind" and "LODR kicks in" is
missing the point. I don't (and never have been able to) see how you
can try and "measure" the subjective difference between the sound of
two amps and try and decide the distance per pound metric, and then
invent a notional DPP value below which its not worth continuing.



No, it's simpler than that (AFAIAC) - an item is either worth bothering
with or it isn't (at any price) and if it is, spending more on a
'better' version of that item is either worthwhile or it is isn't. It's
a highly subjective/personal thing - Rolex vs. Timex, if you like...


snip interesting review which was pretty much what I expected


I suspect that I am being rather excessivly crytical of the amp, and
perhaps the above should be viewed in that light, but I can only apply
the same standards I apply to amps I might build myself, or listen to
that others have built. If I don't at least try and have a standard to
compare against, then it makes any attempt to build something that at
least does what I want (even if its not to anyone elses liking) will
never have a hope of success.

There you go, just my 2d worth.


Thank you for that. The reason I asked is that the much-mentioned Tony
asked me about the very same amp (on eBay for not a lot, at the time)
and I said that it would likely be OK, may well need some TLC at some
stage and that he might do better to spend a bit more money on summat
that was less 'on the outside' and a little more 'on the inside' (or on
top, in the case of valve amps) - is how he came to buy the Bluebell
300B SET monos!

Note to Steve:

Bear in mind that Nick is a highly experienced *valvie* who has pushed
himself much further into the art than many of us could (or would want)
to go - asking him for an opinion on any cheap amp is never going to get
the reaction 'Cor, I wish I had bought one of these instead!!' My own
*general* opinion of Chinese cheepies remains the same - better *any*
amp you can afford, providing it's at least 'OK', than not having one at
all because you can't afford it or don't want to part with the money!!
They at least get you into the game and, if it proves to be the right
way to go, there's nothing to stop you upgrading at any time in the
future - I'm doing this with mics atm, myself!

That'll Teach Me... (Chinese Valve Amp)
 

"Serge Auckland" wrote


What amuses me /irritates in equal measure about all the above is that
even staying with valves, a PPUL EL84 amplifier like the Mullard 5-10
or GEC equivalent has a little more power than the SET, with a whole
lot less distortion and lower output impedance such that is *does*
make music very satisfactorily, without having to make apologies for
the SETs shortcomings. It would also be cheaper to build as a PP
output transformer is considerably cheaper than a half-decent SET one,
and a pair of EL84s cost much less than a single 300B. The only thing
I can think of in a SETs favour is that it looks a lot more dramatic
with those DH big triodes.


What bothers me with what you say Serge is how much your visit here may
have coloured your opinion of SETs. Apart from the fact I only have a
cheepie Chinkie and a homebrew here, I wasn't too well 'speakered'
then - the Jerichos with the Visaton drivers you heard (as did Nick, the
last time he was here) and Lowther EX3s I tried in them some time after
your visit never did come right and now dwell in my garage until I can
get creative with them. The Fidelios I have now (with lesser Lowther
units in them) are streets ahead in every respect.

(Factor in the secondary system with the 'blameless' Technics pre/power
MOSFET combo you appraised 'on paper' for me playing into the TLS80s I
now have and I reckon I could keep most people happy, one way or
another! :-)