Single Ended Amps - What do you think of them?
Dwaine Garden
amps. So I bought them.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3019603406&category=3284
What do the rats think about some simple single ended
mono blocks for the office?
I'm going to replace the discs cap with something better, and
some 1% resisters.
This will be the first time I've heard single ended amps before.
Can anyone tell me what to expect?
I contacted the company to see if they had any still kicking around.
They don't, but the sales person said they are thinking about having
another tube kit for cheap dollars. The company thought it would sell
really well.
Dwaine
Fabio Berutti
"Dwaine Garden" <Dwaine...@rogers.com> ha scritto nel messaggio
news:u64ra.7536$M81....@news02.bloor.is.net.cable.rogers.com...
> Saw this auction on ebay. I'm interested in the single ended
> amps. So I bought them.
>
>
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3019603406&category=3284
>
> What do the rats think about some simple single ended
> mono blocks for the office?
IMHO they are good value for money.
>
> I'm going to replace the discs cap with something better, and
> some 1% resisters.
>
I wouldn't spend more money on such a simple kit. The nice thing is the
price/quality ratio.
> This will be the first time I've heard single ended amps before.
> Can anyone tell me what to expect?
>
In fact it is the audio section of a TV set from the Sixties. This is why
it is called a "student project", the parts were all cheap, readily
available mass-market items.
The project itself is so simple that nothing can go wrong (ie, sound bad),
but I suppose that the output transformer is a very simple, 2W paper-bobbin
one gutted from a TV set: these are not HiFi transformers, having a
frequency response in the 100 - 10000 Hz range, because they were meant to
drive a (mono, no HIFI) TV speaker: a good one delivers a very pleasant
"voice" in the midrange (after all they were designed mostly for speech, not
for music), but do not expect 20-20K performance.
If You connect Your amps with high efficiency, good loudspeakers, You'll get
1W of relaxing, mellow sound, good for "ambience" listening. Maybe single
instruments (classic guitar) will sound better than on some expensive HiFi
units.
The only "tweaking" I'd try is to connect the 50C5 in triode mode (anode to
grid G2 through a 1K/2W resistor), but check the datasheet before. Many
pentodes do not like very much to be triode strapped.
Fred Nachbaur
Fabio Berutti wrote:
> [...]
> The only "tweaking" I'd try is to connect the 50C5 in triode mode (anode to
> grid G2 through a 1K/2W resistor), but check the datasheet before. Many
> pentodes do not like very much to be triode strapped.
50C5's don't mind being triode-strapped, through about a 100 ohm
resistor. But unfortunately they don't sound a whole lot better, and it
drops their power considerably.
The 50C5 was essentially meant for table radios, running at low B+
voltages (line-derived). They have really hot cathodes, and are
therefore capable of quite a bit of peak current (and therefore power).
But they have lots of distortion, and in my opinion are not the greatest
sounding tube in their class.
My vote would be to replace the 50C5 with a 35C5. You'll need to make up
the extra filament drop using a resistor (100 ohms, at least 5 watt, or
replace the existing one with a resistor 100 ohms higher). You'll get a
little less maximum power, but a *much* cleaner output at around 1 watt.
If you want to get "creative," it looks like there's enough room on the
chassis to add a second 35C5. Replace the output transformer with a
push-pull unit, and built yourself a "Lafayette KT-92"!
http://www.dogstar.dantimax.dk/tubestuf/4x4howit.htm . (Of course, it
obviously won't be single-ended anymore...) :)
Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects: http://dogstar.dantimax.dk |
+--------------------------------------------+
Robert Casey
> In fact it is the audio section of a TV set from the Sixties. This is why
> it is called a "student project", the parts were all cheap, readily
> available mass-market items.
> The project itself is so simple that nothing can go wrong (ie, sound bad),
> but I suppose that the output transformer is a very simple, 2W paper-bobbin
> one gutted from a TV set: these are not HiFi transformers, having a
> frequency response in the 100 - 10000 Hz range, because they were meant to
> drive a (mono, no HIFI) TV speaker: a good one delivers a very pleasant
> "voice" in the midrange (after all they were designed mostly for speech, not
> for music), but do not expect 20-20K performance.
I'd try some feedback from the output transformer secondary into the
input triode's cathode. A simple way would be to connect the cathode
to the output transformer secondary, and the other end of the secondary
to ground. If it oscillates, reverse these connections.
Also, I notice that it's a hot chassis design. If you connect it to a PC
soundcard, you'll probably get ground loop induced hum. An isolation
transformer will help here.
Don't be suprised if the electrolytics are dried out thus bad in something
this old. Even unused....
GerryE123
<fabio....@libero.it> writes:
>In fact it is the audio section of a TV set from the Sixties.
Very Sixties! The seller is located in Bethel, NY. Site of the original
Woodstock "Festival".
Gerry