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#1 |
diyAudio Member
Join Date: Mar 2005
Location: HK
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Recently I bought a integrated amp. The power output stage is using parallel push-pull EL84. Total 8 tubes.
The output transformer is 4K pri. impedance. I don't need that much power and considering using only 4 tubes. That is changing from parallel push-pull to single push-pull. What modifications do I need to do without changing the output transformer? Bigger cathode resistor? Or no need to modify anything? The B+ is kind of high, 450 VDC. Thanks for any help. |
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#2 |
diyAudio Moderator Emeritus
Join Date: Jan 2004
Location: Jakarta
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You will need a higher load impedance. I doubt if you can get away without changing the OP tranny, unless you can use different secondary taps for the speakers, e.g. connect 8 ohm speakers to the 4 ohm tap.
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#3 |
diyAudio Member
Join Date: Mar 2005
Location: HK
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I have forgotten to mention that the output transformer is ultralinear.
Tks. |
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#4 |
diyAudio Member
Join Date: Mar 2005
Location: HK
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It does has 4 ohm taps.
One thing I dont understand is that even the ratio is correct, the load impedance still doesn't match. |
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#5 | |
diyAudio Moderator Emeritus
Join Date: Jan 2004
Location: Jakarta
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Quote:
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#6 |
diyAudio Member
Join Date: Jun 2004
Location: big smoke
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If you don't need that much power why not try strapping them triode? Assuming the driver cleanly handles the increased grid capacitance.
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#7 |
diyAudio Member
Join Date: Mar 2005
Location: HK
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Thanks a lot! I will try that.
It is using parallel PP and I thought that make it single PP may have a positive effect on the sonic quality. The cathode resistor is 10R for each tube. So I will double it for the 4 tubes. What is good for cathode resistor for output stage? WW or carbon composite? Thanks for your help. |
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#8 | |
diyAudio Moderator Emeritus
Join Date: Jan 2004
Location: Jakarta
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Quote:
Also, I don't believe changing from parallell to single PP will make any audible improvement to the sonics. Indeed, the opposite is more likely to be true. If you want better sonics, then it might be better to try rdf's suggestion. |
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#9 |
diyAudio Member
Join Date: Mar 2005
Location: HK
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Here is the schematic of the output.
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#10 | |
diyAudio Member
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Quote:
It very probably will. I have never heard parallel tubes sound better. For reasons i don't understand parallel EL84 sound particularly bad. |
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Thread | Thread Starter | Forum | Replies | Last Post |
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