CC Source in a Spud?

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Nick
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#46 Re: CC Source in a Spud?

Post by Nick »

In practice as well :-), but reality may always get in the way.
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#47 Re: CC Source in a Spud?

Post by Dave the bass »

Meh! "Stoopid Reality" getting in the way again.

10K holds the well-behaved 6C45's in-check too. I'll try a known pesky 6C45. 10K is being driven fine by the source (SBT->AK 4396 DAC in standard trim).
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#48 Re: CC Source in a Spud?

Post by Dave the bass »

Andrew wrote: Wed Jul 19, 2017 10:13 pm The great thing about a Spud, for me, is it's so easy to try different stuff and see what floats yer boat.
Agreed, I should have done this ages ago.

Its started to get messy swapping bits in and out so proper bread boarded it all. Currently clip leading different OP TX's in and out.
Image

Back on Grid Choke but with 1K CC grid stopper, something very nice is working with this combo at the moment and a pair of AE 5K OP TX's but using the 16R tap with 8R speaker load.
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I haven't even got to got CCS/Parafeed yet let alone Series and Shunt PSU's. This project has got legs.
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#49 Re: CC Source in a Spud?

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animated-centipede-image-0005.gif
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#50 Re: CC Source in a Spud?

Post by Dave the bass »

^^^ Awwww! Look at his likkle smiley face :-)

Todays lesson has been listening to what happens aurally as you lower the primary impedance of OP TX's. I've gone from 14K and 10K Hashimoto's down through AE 5K and down further to a hefty pair of Majestic 1K25's. I noticed that if I go down to a 1K25 200mA OP TX all the dynamics and detail in the music is lost along with 'air'. It is however 'surprisingly' loud! I missed out a pair of 7K and 2K5 OP TX's. I'll clip those in next.
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#51 Re: CC Source in a Spud?

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Good stuff. I hope you plotted the different load lines. It may be that here is different optimal bias for different loads.
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#52 Re: CC Source in a Spud?

Post by Dave the bass »

Ta. I'm enjoying it.

I haven't plotted the loadlines, I've struggled for years to really get what others can read and see in them and failed despite trying to learn about them, maybe I should try again.

I've kept the Anode Voltage @ 150V which is the maximum according to the datasheet and with a Red LED held the cathode @ 2V, when swapping OPTX's I was purely going by what I heard. Anode dissipation is ~2.1W, well within the 7.8W maximum. I'm just tickling them I believe, in past the I've thrashed them when I've been using them as Interstage drivers, and it resulted in a sound that had been noted :)
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#53 Re: CC Source in a Spud?

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All sounds good & logical. Lower loads will give more power, up to a point, but the 2nd harmonic increases ( which also makes things sound louder ) too, but then if you go too low , all the distortion levels go up and eventually it has the same sound you get from loading a cartridge with a resistor the same value as its Zout - all goes a bit gray and mushy and uninteresting. The 1k25 would probably be in that territory.
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#54 Re: CC Source in a Spud?

Post by Max N »

Very interesting stuff Dave, thanks for sharing.
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#55 Re: CC Source in a Spud?

Post by Dave the bass »

IslandPink wrote: Thu Jul 27, 2017 8:23 pm ... all the distortion levels go up and eventually it has the same sound you get from loading a cartridge with a resistor the same value as its Zout - all goes a bit gray and mushy and uninteresting. The 1k25 would probably be in that territory.
Ah, thats a good description of what I found too Mark.

I think I need to do more studying on loadlines, in my head I can picture the loadline getting more steeper as the load Z drops in value, and with a CCS I can imagine it being near horizontal, aaahh, that'll be the 'CC' as in 'Constant Current' (ya wally DTB).


Ta MrN! Those brill B9a experimenter boards I got from here Max -> http://www.ebay.com/itm/9-pin-breadboar ... 25c0349421
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#56 Re: CC Source in a Spud?

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Dave the bass wrote: Fri Jul 28, 2017 10:43 am
IslandPink wrote: Thu Jul 27, 2017 8:23 pm ... all the distortion levels go up and eventually it has the same sound you get from loading a cartridge with a resistor the same value as its Zout - all goes a bit gray and mushy and uninteresting. The 1k25 would probably be in that territory.
Ah, thats a good description of what I found too Mark.

I think I need to do more studying on loadlines, in my head I can picture the loadline getting more steeper as the load Z drops in value, and with a CCS I can imagine it being near horizontal, aaahh, that'll be the 'CC' as in 'Constant Current' (ya wally DTB).


Ta MrN! Those brill B9a experimenter boards I got from here Max -> http://www.ebay.com/itm/9-pin-breadboar ... 25c0349421
Then imagine dots where the load line crosses each of the anode curves. The more equally spaced those dots are, the lower the distortion. If they are more spread out towards one side, that’s second harmonic (where the middle is the idle point), if they are spread out in the middle and compress at both sides, that’s third harmonic.
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#57 Re: CC Source in a Spud?

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Dave the bass wrote: Fri Jul 28, 2017 10:43 am

Ta MrN! Those brill B9a experimenter boards I got from here Max -> http://www.ebay.com/itm/9-pin-breadboar ... 25c0349421
I've used these in the past, good for more permanent installations.

https://www.hificollective.co.uk/tag_bo ... oards.html
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#58 Re: CC Source in a Spud?

Post by Max N »

Thanks chaps, I will have to get some of those 👍
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#59 Re: CC Source in a Spud?

Post by Dave the bass »

Whats a fella to do on a Saturday night when his beluvved is at a Party that he's not?!

Loadlines!
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#60 Re: CC Source in a Spud?

Post by pre65 »

So, would 3.5K (approx) be optimal ?
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