Headphone amp?
Recycling - giving old equipment a new life.
- Thread starter rock soderstrom
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gepicaster
Member
rock soderstrom
Tour de France
Yes, a headphone amp for Kong or a new practice bass amp for Lemmy!
I decided what is going into the housing. It will be a tube spring reverb with the following features:
for studio or live use
low and high Z inputs
2 channels, stereo or 2x mono with different decay times, depending on the configuration.
can also be fed oldschool single channel for stereo out or 2 different springs combined.
Of course with bling bling "VU" meter for level and on/off indication.
optional dubby delay, I'm not sure yet if that makes sense...
I already have the circuit board and the springs.
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A few things to keep in mind when using parts from the long ago and used to be. Old transformers are not wound with modern insulation on the wire. Could be prone to breakdown at high temps. 'Lytics dry out, changing their characteristics or can short if not slowly brought up to working voltage,aka reformed. Paper caps can be unstable. Carbon resistors can be very noisy or drift way off value. It's all great for the hobbyist, just not reliable for new equipment. Suggest testing parts before you put the effort into making something new out of them. Problems may not even show up until after the build.
Good luck!
Good luck!
rock soderstrom
Tour de France
This is indeed something to keep in mind. I actually use very few old electrical components, never electrolytic capacitors, very rarely resistors. As already described, sometimes I build fuzz pedals with them for fun, but otherwise mostly new components. If I use something old, I test it extensively.
I want my equipment to play and function safely for a long time.
I want my equipment to play and function safely for a long time.
I mainly used the old steel chassis, and the power switch. It was one of those on-ON-OFF switches that first powered up the tube heaters, before applying full supply voltage to the circuits. Instead I used the first on position to power up the amp power supply through a series resistance to minimize the turn on current surge from the several ten thousands of uF reservoir caps. The loudspeakers were connected via relays only after engaging the second on position. So no turn-on funnies and immediate silent turn-off at power down.
JR
JR
Rotary switch or toggle? I would bet you can't find those toggle switches new. Maybe surplus houses?
cpsmusic
Well-known member
Wow, fantastic! When my father passed away I inherited his electronics workshop which contained about sixty years of accumulated stuff. Sadly I couldn't store most of it so a lot of it went to e-waste however I have kept a few things, mostly components that could be used for guitar amps or studio gear. For example, I have a nice box of old meters that probably date to the 1930s which I'm thinking of adding to things just for show. If I'm ever featured in one of the music mags I can say that it's a special, custom audio processor (which actually will be the truth) 
nashkato
Well-known member
that came from a permanent fleamarket inside a hall.
lots of furniture , clothing and bad pop music vinyl there.
i got no idea what it‘s original purpose has been . could be anything , not necessarily audio .
was quite scary to bring it up to 230v without knowing what to expect to measure it‘s outputs.
with bad luck it could have been a welding station .
with selenium rectifiers of course one has always take into account their voltage loss across them
OK, not that esoteric. Thanks
The modern industrial style rotary mains switches are usable , various contact arrangements are available , bulky , but a lifetime job on something like a big poweramp .
A rotary mains switch is something Ive used with tube gear on several ocassion , as Off/standby/on ,
If your carefull about how you do it , no noise when you power up or down , the sound just fades in or out gradually .
Just looking at what you collected together Rock ,
Think about the possibility of incorporating the meter drive as limiter of sorts , an extra load that can be placed at the drive end of the circuit , , the lightbulb limiter is also something well worth building in to a spring reverb driver of this kind
Incorporating your nice Tele mains transformer inside a box with a couple of tanks is going to be a chalenge ,
Your best result might be to make this box the drive amp only end ,sheild and remote the tanks themselves as much as is nessary to get rid of the induced mains hum , and use something else dedicated at the recovery end ,preferably right close to the tanks . There might well be a case to build in a dedicated recovery stage into the tank housing itself , minimise any chances of noise ,
An adjustable pad in the form of a wirewound pot I also very much reccomend incorporated to trim the drive levels to the tank. it gives a good range of tones depending on how you adjust the gain staging , it avoids causing gross distortion in the transducer and spring itself , yet still have the output stage running hot as hell .
A modern 2 channel desktop interface with low noise inputs works well as a reverb recovery sub mixer , just short patch leads , choice of mic line or instrument input is a matter of audition and see , the different load impedences involved will change the sound of the spring output appreciably , it adds more of a sonic pallette to play around with.
The typical desktop interface sloped top panel control surface lends itself perfectly to the job, a simple set of controls , one function per control , no messing with menus , straight in to the sonic sweet spot ,with an entirely analog signal path all the way .
A rotary mains switch is something Ive used with tube gear on several ocassion , as Off/standby/on ,
If your carefull about how you do it , no noise when you power up or down , the sound just fades in or out gradually .
Just looking at what you collected together Rock ,
Think about the possibility of incorporating the meter drive as limiter of sorts , an extra load that can be placed at the drive end of the circuit , , the lightbulb limiter is also something well worth building in to a spring reverb driver of this kind
Incorporating your nice Tele mains transformer inside a box with a couple of tanks is going to be a chalenge ,
Your best result might be to make this box the drive amp only end ,sheild and remote the tanks themselves as much as is nessary to get rid of the induced mains hum , and use something else dedicated at the recovery end ,preferably right close to the tanks . There might well be a case to build in a dedicated recovery stage into the tank housing itself , minimise any chances of noise ,
An adjustable pad in the form of a wirewound pot I also very much reccomend incorporated to trim the drive levels to the tank. it gives a good range of tones depending on how you adjust the gain staging , it avoids causing gross distortion in the transducer and spring itself , yet still have the output stage running hot as hell .
A modern 2 channel desktop interface with low noise inputs works well as a reverb recovery sub mixer , just short patch leads , choice of mic line or instrument input is a matter of audition and see , the different load impedences involved will change the sound of the spring output appreciably , it adds more of a sonic pallette to play around with.
The typical desktop interface sloped top panel control surface lends itself perfectly to the job, a simple set of controls , one function per control , no messing with menus , straight in to the sonic sweet spot ,with an entirely analog signal path all the way .
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not esoteric but almost 100 years old and still working.... while I haven't turned on that amp for several years.
JR
Are we still talking about the equipment?
Just the switch... the amp I built inside that old WE chassis is only 45+ years old.
JR
rock soderstrom
Tour de France
That's an interesting idea, we should talk about it again when I'm ready. I still have to think about the "VU" integration.
These are valid points, I have had some experience with hum from spring reverb tanks in the past. Nevertheless, I want to try to get everything into one box. I try to manage the challenges with a careful layout and additional shielding measures if necessary. I will most likely hate myself when implementing this plan.
At the moment I have planned a fixed pad at the input for line signals plus a dwell pot.
Here is the schematic: (see this thread for further info)
Good ideas!
Back to the old donor case:
The blue resistors from the original PCB of the measureing device are electrically in top conditions, they measure extremely well and are much better than 1% accurate.
They are also from Rosenthal.
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I've been curious about this for a long time and waiting for a good opportunity to ask someone here, and/or find out what the consensus is on old parts.
I want to know if there are critical qualities to a capacitor that one could miss by simply testing for capacitance value? Or critical qualities to a resistor beyond resistance value?
For several years now I've built effect devices using vintage parts--mostly for aesthetics reasons. I like the way they look, and I like the construction details of well designed '60-'70s hand-made electronics. I frequently sell these builds and I haven't yet had a repair due to a failed component, knock on wood.
Most of the problems I've encountered with old parts have to due with corrosion on the component leads making them resistant to lasting solder joints, for one, and then secondly. brittle/comprimised/crumbling CC resistors and film caps.
So it's more like mechanical problems I encounter. But am I potentially missing other electronic shortcomings?
rock soderstrom
Tour de France
Yes, leakage currents, for example, are a critical parameter for capacitors. If they are too high, the operating point of the subsequent amplification stage can be shifted. It gets really nasty when you replace an anode to output transformer coupling capacitor in your vintage U47 microphone with an untested and leaky old capacitor and you kill the original transformer with it.
Always test old components under real conditions.
As I said before, I don't use old electrolytic capacitors and only tested resistors and non-electrolytic caps, mostly in guitar pedals, so there's not much that can go badly wrong.
Edit:
Today, just for fun, I measured the film capacitors from the donor device. The capacitance of both is much higher than specified, which is not a good sign when a 0.5uF capacitor has almost twice the capacitance. Leakage currents and ESR were also increased. There are people who try to compensate for this by formatting, but I don't do that any more. It's too unsafe for me, the savings are too small, and in the event of a fault, it requires more work. My life time is too valuable for that.
By the way, does anyone know what the 98Wp"P" on the black Wima means?
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sortedaudio
Member
What do people think about re using semiconductors? When it comes to silicon power transistors, and some small signal types, I prefer NOS, but have used recycled ant tested (by me) types, over some offered for sale that are quite possibly fakes.
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