Lars,
"but the sensitivity is very high at 100mV rms"
could you elaborate please. Input sensitivity? Thanks
"but the sensitivity is very high at 100mV rms"
could you elaborate please. Input sensitivity? Thanks
desperateaudio said:
Input voltage required to give full output.
CD player gives 2.00v !!
Usual input sensitivity is around 0.75v for maximum output.
Remember
With 6080, apply filament ( heater ) supply for at least 2 minutes before applying the high voltage........
Andy
Why not swap the 6sn7 cascode for a ccs'ed 5842 or 6c45 for lower distortion (see pete millets research) and better drive capability?
@fuling: at how much do you estimate the material costs for the chokes you winded?
Simon
@fuling: at how much do you estimate the material costs for the chokes you winded?
Simon
Klimon: The 6SN7 is not connected as cascode. Desperateaudio had allready breadboarded the 6SN7 cascaded driver so I just checked it for him. Wouldn´t recommend it either!
Your recommendations are great!
Without NFB 6C45 is the best choice, albeit it normally sounds better with a high B+ 400V and anoderesistor. Remember Milletts measurements are without load! 5842 is a nice sounding, descent tube but suffers from limited swing capability compared to 6C45.
One could even add a small amount of NFB to the 6C45 and still get an acceptable senstivity.
If one decide to use NFB a cascaded 6H30 would be the obvious choice. My idea is that the feedback shouldn´t be over the whole configuration, the input tube should be left outside the loop.
Your recommendations are great!
Without NFB 6C45 is the best choice, albeit it normally sounds better with a high B+ 400V and anoderesistor. Remember Milletts measurements are without load! 5842 is a nice sounding, descent tube but suffers from limited swing capability compared to 6C45.
One could even add a small amount of NFB to the 6C45 and still get an acceptable senstivity.
If one decide to use NFB a cascaded 6H30 would be the obvious choice. My idea is that the feedback shouldn´t be over the whole configuration, the input tube should be left outside the loop.
This is called "shunt feedback". The grid will be virtual zero and Zin 22k. When feeding you must use a lowZ source, so it won´t work with an input pot.
Just finished breadboarding the original design last night. Plugged the CD Player into a passive preamp volume control (50K) and then directly into amp. Sensitivity is an issue as previously discussed as I cannot get volume to go above a few clicks before distortion. The orginal design cannot be good for more then a few watts. Keep volume in check and she sound like she has potential.
Couldn't the shunt feedback circuit you posted be modified to a classical cathode-cathode feedback design (+ volume pot) with satisfactory results?
That's some quick result. Keep us posted on the evolution.
Simon
The original will give you below 1W at 5% THD into 8ohm. If you want less than 1% you will have under 0,1W!
And if you happen to have a 32 ohms speaker you will more than triple your available output power!
And if you happen to have a 32 ohms speaker you will more than triple your available output power!
With a 0,75A CCS and three 6080s at 100V Ua 135V B+ you can get ca 2W 5% 8ohm and 0,15W 1% 8ohm. More tubes are needed when going 8ohm!
The problems with ESLs are that that they have extremely low Z at 20kHz. But up there not so much is needed. Still I think you should have at least 5 parallelled for that kind of use!
Poynton: Why not the old Philips 9710, 800ohm😀!
The problems with ESLs are that that they have extremely low Z at 20kHz. But up there not so much is needed. Still I think you should have at least 5 parallelled for that kind of use!
Poynton: Why not the old Philips 9710, 800ohm😀!
revintage said:
Well I put it together as a stereo amp 3 per side as a test. I will now take it and convert it to a mono block 5 or 6 tubes and see what happens. Give me a fee day. ALso I will try and psot pic's tonight.
Go for six, must be a winner! Will go for five myself, as I have to nice chassis with five octals in each.
Was thinking of using a conventional 12V SMPS from a computer-supply for heaters.
Was thinking of using a conventional 12V SMPS from a computer-supply for heaters.
Fuling, how would the simplest possible PSU for a monblock SE OTL with 5x6080, B+ 135-140V at 1,25A look?
Should be nice if a choke wasn´t needed.
Raw B+ is 155V so I can drop 15-20V without problems.
Will use SMPS for heaters and drivers B+.
Should be nice if a choke wasn´t needed.
Raw B+ is 155V so I can drop 15-20V without problems.
Will use SMPS for heaters and drivers B+.
poynton said:
The original design. My power supply PT transformer, choke and heater trans were all from a military 6AS7 power supply using 6 - 6AS7's so they are all poted trans with extreme current capabilities. I will post pics tonight before a start on the other. Also I will post current voltage measurements and power schematic.
- Status
- Not open for further replies.