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Andrew
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#16

Post by Andrew »

simon wrote:
If you go to a directly heated driver, whether a 4P1L pentode say or another triode, then you need to get the filament supply right as it will hum like a good 'un. Andrew L here has developed some boards and might still have some, or try Rod Coleman on DIY Audio, whose boards are also very good. Or lots of chokes
Still got PCB left.
Analogue, the lost world that lies between 0 and 1.
Tomas
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#17

Post by Tomas »

You are absolutely right there, I can bury myself with what ifs and ideas. Thanks for that Simon and you as well Steve. :)
Tomas
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#18

Post by Tomas »

Hi Andrew, are these blank PCB with parts and instructions for the user friendly needy among us? Thanks Tom
Tomas
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#19

Post by Tomas »

Hi Mark, You're saying that a cap coupled C3g in pentode to 45 would be preferable to The IT that I have available?
simon
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#20

Post by simon »

Tomas wrote:Hi Mark, You're saying that a cap coupled C3g in pentode to 45 would be preferable to The IT that I have available?
Suck it and see. It's the only way you'll find out what you prefer.
Tomas
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#21

Post by Tomas »

I was asking to find out if the IT was suitable as is, thank you for your input Simon.
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IslandPink
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#22

Post by IslandPink »

Tomas wrote:Hi Mark, You're saying that a cap coupled C3g in pentode to 45 would be preferable to The IT that I have available?
If done correctly then I would have that opinion based on my ears and my recent projects . For instance my current amp was C3g pentode into KR300B , now uses a DHP ( 4P1L ) into 300B , and I'm not intending to change ( btw. I did run ECC40/45(choke-loaded)/300B for a spell in the past ) .

It's not going to be clear-cut, as there are system decisions to be made of course, and listening preferences.
Comparing C3g triode with by-passed cathode, and C3g pentode with un-bypassed cathode and about 8k anode load, you'll get slightly more gain ( 50? ) with the pentode, which may be irrelevant .
In the mids and treble , it's a bit dependant on the IT's which I would say is best - I'd want to see at least 50% nickel core in the IT's to match or beat a good cap & resistor .
In the bass I'm sold on the pentode option if used with a VR tube for the G2 . The pentode is nearly linear down to DC then, because it has no cathode by-pass cap and the cap/resistor coupling can be down around 1Hz cut-off with something like 0.47u/220k into the 45 . The triode/IT combo, on the other hand, has a cathode cap that might be 2Hz , and the IT inductance ( limited in SE transformers ) might give only 5 to 10Hz -3dB point . This will take away a bit of timing and low-bass tone .

If you've got the parts, and just want to build a neat chassis without a re-build, then don't let me stop you. The C3g/IT/45 will be a very nice amp. If you have the time, though , a breadboard to compare that against C3g pentode would be good.
"Once you find out ... the Circumstances ; then you can go out"
Tomas
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#23

Post by Tomas »

Thanks very much for the info and insight Mark. I suppose I have a couple of chokes on my hands to use for a future project. In a way the IT's were restricting my choices as I was pretty committed to trying to use them. This will open things up a lot and allow me to go in a new direction for a 2 stage. Thanks again. :)
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