Can someone please post the resulting Schematic with all the changes noted?
Sorry, but its pretty confusing to read the whole thread and the changes people recommend. (that is if you are a NEWB....)
Thank you.
Sorry, but its pretty confusing to read the whole thread and the changes people recommend. (that is if you are a NEWB....)
Thank you.
Hey petrnyc: The attached are the values I eventually ended up using. This is thanks to the many excellent helpful suggestions of a number of inputs on this thread, esp. from Ketje. Thanks guys! Note that I am using Edcor 8K output transformers, not Hammond (as the title of this thread.) I had great success with these values and the amp sounds beautiful.
The diagram shows the values compared to the original design. Note that my input stage is now triode-strapped, and on the output I added switches to select from the Pentode mode to Ultra-linear mode. (I must say, my old ears cannot really hear the difference).
I have also included some final DC voltage values at various points (brackets are the second channel values) - these are for my board, others may not be quite the same.
I have vids of the amp here if you're interested:
Cheesy show of amp:
Tech explanation:
The diagram shows the values compared to the original design. Note that my input stage is now triode-strapped, and on the output I added switches to select from the Pentode mode to Ultra-linear mode. (I must say, my old ears cannot really hear the difference).
I have also included some final DC voltage values at various points (brackets are the second channel values) - these are for my board, others may not be quite the same.
I have vids of the amp here if you're interested:
Cheesy show of amp:
Attachments
sorry one more, do you find it having enough gain to run straight from I phone (or similar source) to louder listening level?
Nice work, Jikkelstikkel! Regarding your measured voltage - I’m puzzled that in the schematic on the Voltage Amplifier section you show different voltages on the plate and screen voltage for this triode-connected pentode. Is there a mistake?
Thank you. Volume is absolutely fine for my purposes. I'm using a pair of JBL S310BE speakers (supposed to be around 91dB sensitivity- not that great).
I haven't measured anything yet, but I play it both on my Samsung phone and that older green ipod nano seen in the video, and it is really loud. If I turn it up a lot it will go into clipping, so the input sensitivity is more than enough. I think this configuration is supposed to offer up to 17W output. I think the Vrms output power from cellphones and audio players is pretty good these days.
Ha. You're very right Francois! Yes that's an incorrect copy paste from the other tube that shouldn't be there. So, the Pin 6 and 3 are at the same 74V/66V potential on that ECF80. Thanks for pointing it out.
Hello, Help....
Anyone near in tristate (NY, NJ, CT) area would be able to help scope out the feedback values for bunch of beer or wine? The unit is built, voltages are all well, it works, but has some ringing at different volume settings.
thanks
Anyone near in tristate (NY, NJ, CT) area would be able to help scope out the feedback values for bunch of beer or wine? The unit is built, voltages are all well, it works, but has some ringing at different volume settings.
thanks
Hello,
Sorted out the ringing problem, but after a while I found out the amp doesn't have enough gain (I am using it as an integrated amp and its forcing me to use a preamp) in the ECF80 triode mode.
My question:
In case I want to hook it up as intended, in pentode mode on the ECF80 , do I scrap the extra diode 1N4148 that was added in Ketje (Mona) schematic and add in all the original hook up resistors and caps the schematic calls for?
Sorted out the ringing problem, but after a while I found out the amp doesn't have enough gain (I am using it as an integrated amp and its forcing me to use a preamp) in the ECF80 triode mode.
My question:
In case I want to hook it up as intended, in pentode mode on the ECF80 , do I scrap the extra diode 1N4148 that was added in Ketje (Mona) schematic and add in all the original hook up resistors and caps the schematic calls for?
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