To Audiowize
ok your consideration but the question is on the phase
Maybe the results are fine for him
And the triode connection on 84 gives you lot of easy work on OT
Regarding the subwoofer I think can be fine to get there the signal
With this configuration maybe the answer at low frequency will be scarce if you take the signal from 8 ohm with resistor partition
Walter
ok your consideration but the question is on the phase
Maybe the results are fine for him
And the triode connection on 84 gives you lot of easy work on OT
Regarding the subwoofer I think can be fine to get there the signal
With this configuration maybe the answer at low frequency will be scarce if you take the signal from 8 ohm with resistor partition
Walter
I assure you that this little stereo amplifier sounds very good... compared to the last schematic I have only increased the resistor on the CF from 1k to 1k8 to give more breathing space to the low frequencies... the only defect which probably depends on the quality of the OTs is that with large orchestras the sounds of the various instrumental sections are a bit confused... this is also why I was wondering if it could also depend on the inverted phase... by inverting the speaker cables I resolve that of the high frequencies, but I don't know how to do for the signal that comes from the pre to the sw... maybe it's better to leave everything as it is, without inverting anything?
Bravo!!!
Then the confusion is also by the limited power you have ( probably also for the efficiency of speakers)
Walter
A 12AX7 connected as a mu follower will easily drive a pentode connected EL84 / 6BQ5.
The bare pentode EL84 will have a rather useless Damping Factor (DF). There are two simple ways to improve that.
First method is Negative Feedback from the secondary of the Output Transformer (OPT) directly to the EL84. With one end of the OPT secondary connected to common, one of the OPT secondary taps is taken to the bottom end of the EL84 RC bias network. If the gain increases, switch the secondary connexion around the other way. When connected to the 8R tap the NFB is about 5 db & the DF is about one. One is a lot better than none & gives better control of the loudspeaker.
The second method sends NFB from the OPT secondary back to the top of the cathode bias resistor of the bottom triode of the mu follower. If the gain increases, switch the connexions on the OPT secondary. Start with something like a resistor of 100K to avoid instability. This way DFs of 3-5 are easily got. And loudspeaker control is much better. 👍
Why two power supplies when one would do?😀
The bare pentode EL84 will have a rather useless Damping Factor (DF). There are two simple ways to improve that.
First method is Negative Feedback from the secondary of the Output Transformer (OPT) directly to the EL84. With one end of the OPT secondary connected to common, one of the OPT secondary taps is taken to the bottom end of the EL84 RC bias network. If the gain increases, switch the secondary connexion around the other way. When connected to the 8R tap the NFB is about 5 db & the DF is about one. One is a lot better than none & gives better control of the loudspeaker.
The second method sends NFB from the OPT secondary back to the top of the cathode bias resistor of the bottom triode of the mu follower. If the gain increases, switch the connexions on the OPT secondary. Start with something like a resistor of 100K to avoid instability. This way DFs of 3-5 are easily got. And loudspeaker control is much better. 👍
Why two power supplies when one would do?😀
Easy to invert the signal at one speaker simply by reversing the cable connexions at one of them.
Don't sweat it.😀
I expect to find an HD start at half volume, but, using 93dB monitors (Cabasse IO2), I just turn it less than 1/3 to hear more than enough sound level in my room. It doesn't seem to me that the problem is the HD, but the OT's ability to follow more complicated musical passages... anyway, I'll try some better OTs soon and I'll let you know about.
Two separate power supplies make my life much easier because I can use them separately for different configurations, because I don't have to recalculate all the circuit parameters every time I make changes to the circuits and for many other reasons. This does not mean that it cannot be built with a single power supply if someone is interested in the project.
Two separate power supplies make my life much easier because I can use them separately for different configurations, because I don't have to recalculate all the circuit parameters every time I make changes to the circuits and for many other reasons. This does not mean that it cannot be built with a single power supply if someone is interested in the project.
" Easy to invert the signal at one speaker simply by reversing the cable connexions at one of them.
Don't sweat it."
The sw problem remains... so I would have the main circuit in phase and the sw in counter phase.
Don't sweat it."
The sw problem remains... so I would have the main circuit in phase and the sw in counter phase.
It's worth considering that commercial recordings are made with no attempt to maintain any sort of absolute polarity, and that many, if not most, loudspeakers have drivers operating with opposite polarity to each other. You may have a preferred polarity for some recordings, but it will be wrong for the other half. If you really can hear absolute polarity as important to you, then you need a switch somewhere to change it for each recording. Back in the 1980s when this was a fad, folk would mark their recordings with their preferred switch setting. (ref: Wood effect). Later, folk got over it.
All good fortune,
Chris
All good fortune,
Chris
Maybe the Sw doesn't respect the absolute phase.
To check it if you have a scope check at the terminal of sw loudspeaker the wave then with other channel of scope you can compare the input and the output of OT
Walter
I forgot: 6FD7 tubes can be replaced directly with the similar 6DR7 and 6CY7 (in this last case the Grid of unit 2 must be strictly connected to pin n°3)... If you want to use octal sockets instead, you can use 6EA7/ as preamp 6EM7 tube.
I have often converted line stages in pre-amplifiers with too much gain into cathode followers (only unity gain) without ever causing a deterioration in the sound character.
But I have heard from many developers of tube amplifier circuits consider these tube buffers to be bad in terms of sound character because of the unmusical character that supposedly results from them.
Without exception, the strong negative feedback was always given as the reason, although no one I spoke to was able to clearly distinguish between series feedback (cathode follower) - go to
http://www.valvewizard.co.uk/accf.html
and parallel NFB - go to
http://www.valvewizard.co.uk/localfeedback.html
What disadvantage (except only unity gain) could be present in case of the use of a cathode follower (single triode or dual triode in parallel mode) in the signal pad resp. power amplifier driver ?
P.S.: this threads don't provide the wanted information:
https://www.tubecad.com/2011/08/blo...r relies on,voltage relative to input voltage.
https://www.diyaudio.com/community/threads/cathode-follower-yay-or-nay.30180/
http://www.valvewizard.co.uk/accf.html
https://wtfamps.com/cathode-follower/
But I have heard from many developers of tube amplifier circuits consider these tube buffers to be bad in terms of sound character because of the unmusical character that supposedly results from them.
Without exception, the strong negative feedback was always given as the reason, although no one I spoke to was able to clearly distinguish between series feedback (cathode follower) - go to
http://www.valvewizard.co.uk/accf.html
and parallel NFB - go to
http://www.valvewizard.co.uk/localfeedback.html
What disadvantage (except only unity gain) could be present in case of the use of a cathode follower (single triode or dual triode in parallel mode) in the signal pad resp. power amplifier driver ?
P.S.: this threads don't provide the wanted information:
https://www.tubecad.com/2011/08/blo...r relies on,voltage relative to input voltage.
https://www.diyaudio.com/community/threads/cathode-follower-yay-or-nay.30180/
http://www.valvewizard.co.uk/accf.html
https://wtfamps.com/cathode-follower/