Guessso if i replaced the 820uf with a 22uf would that be OK (or should i just try it ?)
The Doddington Special
#136
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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Dave the bass
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#137
Nice work Phil,
They look great, well done they're very smart. Hows it sounding today?
DTB
They look great, well done they're very smart. Hows it sounding today?
DTB
"The fat bourgeois and his doppelganger"
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pre65
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#138
Hi-this morning i have made permanent my clip lead earth mods on the monoblocks,and now the hum (if thats what i can ONLY JUST hear with my lughole right up against the speaker cone) is minimal.
I have also extricated the 820uf caps from the power supply and replaced them with 22uf motor run caps (which i had in my box) and now its playing again.
I will compare later in the day with the Rankin 45 DC CC as that is of similar power (2W ish) and also uses the ECL82.
Today is a good day !
A nice man has topped up my heating oil tank and a 25 yr old blonde looking for an "older" man has viewed my profile on a dating site !!
Not that i would be interested of course,but i can dream.
I have also extricated the 820uf caps from the power supply and replaced them with 22uf motor run caps (which i had in my box) and now its playing again.
I will compare later in the day with the Rankin 45 DC CC as that is of similar power (2W ish) and also uses the ECL82.
Today is a good day !
A nice man has topped up my heating oil tank and a 25 yr old blonde looking for an "older" man has viewed my profile on a dating site !!
Not that i would be interested of course,but i can dream.
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)
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Dave the bass
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#139
It might be one of us in a wig after your new amppre65 wrote:.... a 25 yr old blonde looking for an "older" man has viewed my profile on a dating site !!
Don't be fooled!DTB
"The fat bourgeois and his doppelganger"
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pre65
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#140
Hi-still liking the ECL82 sound.
I had a problem the other day with the stereo image not being central,and tapping the red amp (RH side) produced a loud crackle.Investigations revealed that i had not soldered the wire to valve pin 9 properly !
Now the image is rock steady in the middle (when its supposed to be) and no crackling.
I look forward to showing this "little" amp at the next fest.
I had a problem the other day with the stereo image not being central,and tapping the red amp (RH side) produced a loud crackle.Investigations revealed that i had not soldered the wire to valve pin 9 properly !
Now the image is rock steady in the middle (when its supposed to be) and no crackling.
I look forward to showing this "little" amp at the next fest.
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)
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pre65
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#141
Hi-looking at the ECL82 application data it says Ia (for the pentode) is 35ma but the limiting value for Ik is 50ma
If i were to put a CCS on the Kathode should i go for the "limit" (ie 50ma) or back off a bit to say 40ma ?
I am a bit wary of trying to "improve" on such a good design so what does the panel think ?
If i were to put a CCS on the Kathode should i go for the "limit" (ie 50ma) or back off a bit to say 40ma ?
I am a bit wary of trying to "improve" on such a good design so what does the panel think ?
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)
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pre65
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#143
Hi-well,just shows up my ignorance !
So is it only for PP amps then ?
So is it only for PP amps then ?
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)
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Cressy Snr
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#145
Hi Philip
In a single-ended amp wouldn't you want a constant current source in the anode circuit rather than a constant current sink in the cathode.
In this application a sink would cause 100% negative feedback via the grid / cathode path unless it was bypassed by a capacitor, in which case you might as well have stuck with a simple resistor.
The CCS to replace the anode load resistor on the other hand would give constant current draw without any problems, but you would have to build one that was able to withstand the HT.
Just thinking out loud so I could be wrong.
Steve
In a single-ended amp wouldn't you want a constant current source in the anode circuit rather than a constant current sink in the cathode.
In this application a sink would cause 100% negative feedback via the grid / cathode path unless it was bypassed by a capacitor, in which case you might as well have stuck with a simple resistor.
The CCS to replace the anode load resistor on the other hand would give constant current draw without any problems, but you would have to build one that was able to withstand the HT.
Just thinking out loud so I could be wrong.
Steve
Sgt. Baker started talkin’ with a Bullhorn in his hand.
#146
Not sure, always ready to be wrong, Have you a circuit for the Rankin amp?
My reading of it, is a transformer is a current device, its the change in current that causes a change in flux, and so a change in the secondary voltage. If there is a CCS in the cathode, how can the current on the anode change? (ignoring A2)
Its different in the case of a PP, there the total current through both valves remains constant, but the proportion through each valve changes along with the signal.
My reading of it, is a transformer is a current device, its the change in current that causes a change in flux, and so a change in the secondary voltage. If there is a CCS in the cathode, how can the current on the anode change? (ignoring A2)
Its different in the case of a PP, there the total current through both valves remains constant, but the proportion through each valve changes along with the signal.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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pre65
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#147
Hi-on the Rankin 45 Direct coupled Constant current amp the pentode section of the ECL82 is used for that purpose.
That is why i asked the question as i assumed that constant current was a good thing.
http://i111.photobucket.com/albums/n146 ... cdc004.jpg
That is why i asked the question as i assumed that constant current was a good thing.
http://i111.photobucket.com/albums/n146 ... cdc004.jpg
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- ECL82 cc dc002.jpg (23.91 KiB) Viewed 8216 times
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)
#148
Ah, I see, I stand corrected (ish), in that circuit, its bipassed by a cap, so its only a CCS to DC. So I can see it would work in that case.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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pre65
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#149
So,if i were to use a LM317 based CCS on the ECL82 Pentode side cathode with say a 34R resistor (2 x 68R) to give 37ma what size capacitor would i need across the CCS ?
With a 390R cathode resistor i am getting 33.8ma (LH) and 30.8ma (RH)
When i measured the cathode voltages i got 13.2v (LH) and 12.02v(RH).
Would that be down to unmatched valves ?
HT is 186v(LH) and 188v (RH).
With a 390R cathode resistor i am getting 33.8ma (LH) and 30.8ma (RH)
When i measured the cathode voltages i got 13.2v (LH) and 12.02v(RH).
Would that be down to unmatched valves ?
HT is 186v(LH) and 188v (RH).
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)
#150
Don't know, I would assume the same size you use to bipass the cathode resistor would be a place to start.what size capacitor would i need across the CCS
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.