CC Source in a Spud?
- Dave the bass
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#1 CC Source in a Spud?
Imagine a Spud amp. One gain stage. Its to be used on a pair of Saburo (fairly large and efficient) speakers in a fairly small room (my workshop/guest bedroom). Source with be a SB Touch via an AK4396 DAC so 'line level'.
6C45, I've got a couple spare, that'd be an ideal candidate (IMO).
Now then, (I think I've got this right) using a 6C45 as the single gain stage ...if I were to put a CC Source in the Anode of that spud amp that should enable that stage to achieve maximum gain as it'll be swinging into a very high Z. So, is there anything that should stop me para-feeding off that node between CCS tail and anode via a quality cap and small inductor?
6C45 is a proper little grunt of a valve I believe, its got fairly low ra and thus lends itself to this application in that it doesn't require a high ratio step down op TX which may rob the stage of what little power its got already yeah?
LED cathode bias to prevent any local feedback/'degeneration' in the stage too perhaps?
Nobel prize for clever thinking or Knobhead Prize for being errr....a knobhead.
6C45, I've got a couple spare, that'd be an ideal candidate (IMO).
Now then, (I think I've got this right) using a 6C45 as the single gain stage ...if I were to put a CC Source in the Anode of that spud amp that should enable that stage to achieve maximum gain as it'll be swinging into a very high Z. So, is there anything that should stop me para-feeding off that node between CCS tail and anode via a quality cap and small inductor?
6C45 is a proper little grunt of a valve I believe, its got fairly low ra and thus lends itself to this application in that it doesn't require a high ratio step down op TX which may rob the stage of what little power its got already yeah?
LED cathode bias to prevent any local feedback/'degeneration' in the stage too perhaps?
Nobel prize for clever thinking or Knobhead Prize for being errr....a knobhead.
"The fat bourgeois and his doppelganger"
- pre65
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#2 Re: CC Source in a Spud?
Nice to see a valve project being talked about.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- Dave the bass
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#3 Re: CC Source in a Spud?
Ta, I've been 'somewhat involved in other crud' for so long its nice to be able to start thinking about ideas and projects again.
"The fat bourgeois and his doppelganger"
#4 Re: CC Source in a Spud?
Just remember that the valve will see the CCS in parallel with whatever load impedance you are hanging off it, so there is no free lunch.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
- Dave the bass
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#5 Re: CC Source in a Spud?
Meh, thats what I'd forgotten, I'm very rusty here.
"The fat bourgeois and his doppelganger"
- pre65
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#6 Re: CC Source in a Spud?
Something like an ECL82 (with a triode and pentode) may be more versatile ?
http://tdsl.duncanamps.com/show.php?des=ECL82
There may be other similar types in that old box of tv valves you once had ?
http://tdsl.duncanamps.com/show.php?des=ECL82
There may be other similar types in that old box of tv valves you once had ?
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- Dave the bass
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#7 Re: CC Source in a Spud?
Yeah I know Phil but I've been there and done that before on BOBA.
I really fancy a true spud (its nearly lunch time, arf) and after reading up a bit on CCS and Diode biasing again in Merlins latest Tome I'm beginning to get the itch to try Silicone around a valve.
I really fancy a true spud (its nearly lunch time, arf) and after reading up a bit on CCS and Diode biasing again in Merlins latest Tome I'm beginning to get the itch to try Silicone around a valve.
"The fat bourgeois and his doppelganger"
#8 Re: CC Source in a Spud?
There is no reason why what you want to do wont work. Andrew uses a 6c45p as a spud amp and it works well. Just dont forget the load when working out the loadlines. Also remember that unlike a inductor a CCS wont swing above B+
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
- pre65
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#9 Re: CC Source in a Spud?
Fairy nuff.
What about using the CCS in the cathode ? EDIT-- forget that suggestion.
What about using the CCS in the cathode ? EDIT-- forget that suggestion.
Last edited by pre65 on Tue Jul 11, 2017 11:35 am, edited 1 time in total.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- Dave the bass
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#10 Re: CC Source in a Spud?
Thats another thing I'd forgotten, kerrikey, I'm more rusty(ier) than I thought. OK, so in brief, a CCS will allow the Valve to swing into a massive AC impedance and in Merlins book he also mentions excellent PSRR and low distortion only limited by the 'linearity of mu' amongst other things whereas with an Inductor in the Anode, less so.
Yeah, I remember many years ago AndrewL saying he used 6C45 in a Spud and at the time was using huge Schicko (sp?) cabs to to make the most of it.
"The fat bourgeois and his doppelganger"
#11 Re: CC Source in a Spud?
Yep, a CCS is a easy way to get a large anode load and good PSRR with the proviso of the driven load setting the actual load the valve sees. The downside is you need a higher B+ to allow the headroom the CCS needs, which will increase the dissipation in the CCS. A choke load will do all the above, increase PSRR at AC, just not a DC, High load (again at AC) and makes the most of B+, so has little problem with dissipation. The downside of the choke is size and cost. In both cases, the quality matters as well and you can hear a bad CCS as well as you can hear a bad choke.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
- andrew Ivimey
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#12 Re: CC Source in a Spud?
Um mm in a spud amp the output transformer is the choke too, isn't it?
Was BOBA that bad? Nope. Could it be worth experimenting with, bigger chokes, better output tx ?
Was BOBA that bad? Nope. Could it be worth experimenting with, bigger chokes, better output tx ?
Philosophers have only interpreted the world - the point, however, is to change it. No it isn't ... maybe we should leave it alone for a while.
#13 Re: CC Source in a Spud?
Yes, the output transformer is doing the job of the choke. I think Dave wants to do stuff to learn stuff, not just to make a sound.andrew Ivimey wrote: ↑Tue Jul 11, 2017 2:33 pm Um mm in a spud amp the output transformer is the choke too, isn't it?
Was BOBA that bad? Nope. Could it be worth experimenting with, bigger chokes, better output tx ?
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
- andrew Ivimey
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#14 Re: CC Source in a Spud?
Yes I realise that. BOBA has many more variables to learn from. I well member AndrewL's 6c45 spud, at Owston. Imp ressive ++.
Did he use an input transformer as input?
Did he use an input transformer as input?
Philosophers have only interpreted the world - the point, however, is to change it. No it isn't ... maybe we should leave it alone for a while.
- IslandPink
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#15 Re: CC Source in a Spud?
Ooh, like designing loudspeakers then ?
Slippery slope ....
"Once you find out ... the Circumstances ; then you can go out"