#4710 safety valve

KOSMO MODULES
61

Cheers, always good to have a reference for what your trying to achieve. I was just using a basic wave out of the 3340 VCO.

Ta

Rob

62

There’s always this one (demo starts at ~5:40):

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63

yeah try oscillator, filter then the safety valve, it makes soft hi cut sound a lot warmer in that capacity

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64

I tried with one Oscillator through the GRRRRRRR, same response.

I did discover the super self oscilating with the input unplugged.

I went through it all and checked everything. I then did what I should have done and got a second Oscilator…

Yay it works :slight_smile:

Footnote: Tube is a JJ Valves ECC83s from hotrox https://www.hotroxuk.com/jj-electronics-ecc83s-12ax7.html

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65

awesome sounds grand!!! glad its working and stuff!!! the light around the back of the valve looks cool!!!

also another I hadn’t touched on and was planning to do so in the vid, is the tone control stops being that useful when volume is near its max, purely because its right at the top end and the tone just doesn’t reduce clipping on the outboard.

so if you think the tone doesn’t work, likely it does but before the outboard clipping.

for my setup I have one maxed out on everything, and in another part of the synth I have another where volume is about 50 percent, gain is max and the toned down low to sound like a soft saturation

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66

Just got mine in the mail yesterday! Super excited to start this venture.

Anyone able to find those 114BX 1/4" jacks for cheap? Hard to justify spending $3.50 for each one!
Was thinking of just using my standard 1/4" input and soldering the appropriate leads to the board instead.

67

@Mezzanine I use the ones from Tayda:

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68

Got mine working today, I did have to solder in the valve in the end otherwise I didn’t get a good enough connection. Also realised I needed to put the direct out of the oscillator out of my crave into it to get anything out with it turned ON

I did notice that in feedback/drone mode the volume drops off significantly the higher pitched the drone, I’m assuming this is expected behaviour?

70

Jacks

71

Thanks for the links! I’ll definitely be looking into those. Cheers!

72

:metal: Just placed my order! Thanks!

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73

Okay now seems like it’s decided to stop working again, it’s not even getting into self oscillation mode either.

I can hear an incredibly faint tone with an input plugged in if I whack the levels up to max but that’s it any idea what could be causing this? It was working just fine yesterday

74

Do you have resistance across the heater to ground, check that 27r and the actual valve heater resistance and continuity.

Have you got a scope you can put on the input to the OPAMP? Check that your getting a signal before that?

After that it’s back to the usual of following the diagram and checking all the rest of the circuit and components.

75

Everything seems fine with the valve, it gets warm when it’s been on. I have noticed that the 27R does get really quite hot however further up the thread seems to suggest whilst this isn’t ideal it’s not awful.

Unfortunately I do not have a scope no, I really should grab one because it would make debugging things like this a lot easier, something to add to the list!

Think we’re on checking the circuit and components and continuity. It is very odd that it was working fine a few days ago but has decided now is the time to shit the bed!

76

CryoS: try putting some 51Rs in parallel instead of 27R to spread the load out.

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77

Unfortunately all I have are 47Rs that’s about as close as I can get. gets me to about 23R, they’re still getting far too hot and I’m still not getting any signal on the output with it turned on :confused:

EDIT: I do get some sort of signal if I bugger about with the valve pins around the back with my finger but only very short bursts.

Continuity test for everything to the opamp and past the opamp all seem to be fine too.

78

Far to hot for you, or for the resistor?

Two 47 ohm resistors in parallel would give you 12/(47/2+12.6/0.15) = 112 mA through the circuit, and each resistor sees half of that or 0.056×0.056×47 = 0.15 watt which is well within spec for a 1/4 watt resistor. See the graph here for how using more resistors lower the power dissipation for each individual resistor.

If you’re still concerned, you could try shorting the resistor. The valve can handle the full 12 V just fine.

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79

If it’s well within spec then I have no issue, I just won’t touch them :grinning_face_with_smiling_eyes:

Going to order a scope so I can see what’s going on a bit better, have swapped out the opamp but that didn’t seem to make a difference.

80

Some scope discussion here

For not so cheap scopes I can recommend the Rigol DS1054Z.

81

I got this one that he also liked

pretty much the same price. Half the channels, 4x the bandwidth.

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