did you use audio coupling caps? I find that cancels out the video-ness of TV tubes - the sound comes out smoother, not in a 525 line format.
;-)
6BM8, also known as ECL82, is an audio valve. It, or its cousin PCL82, was used for audio in TV sets but also in general audio amps. In the UK they sounded better on 625 lines, but that was because 405 used AM audio.
6GW8, also known as ECL86, is also an audio valve. It is slightly more recent than the ECL82 and generally reckoned to be better than the ECL82, apart from the issue of long-term reliability.
6GW8, also known as ECL86, is also an audio valve. It is slightly more recent than the ECL82 and generally reckoned to be better than the ECL82, apart from the issue of long-term reliability.
I did use coupling caps, but interesting was that various values of grid load resistor made quiet a big difference on the sound, dark, bright, more mids...not something I experienced so much with using more standard tubes.
True about the 6GW8. In PP 6GW8 amp (Playmaster) I have used daily some years ego, they wore out and gone out of balance fairly soon. I have about 20 of them used and measuring bias while powered they all wary wildly.
True about the 6GW8. In PP 6GW8 amp (Playmaster) I have used daily some years ego, they wore out and gone out of balance fairly soon. I have about 20 of them used and measuring bias while powered they all wary wildly.
30hz distortion
I've got couple of Hifi SE 6v6 amps, they both don't handle 30hz bass well. It's the type of bass one can hear on those subwoofer vids on YT but with "normal" music it normally doesn't happen. It's not much like a distortion but more of a heavy saturation choking effect. Various values of cathode caps have no effect.
My other amp which is PP amp handles the 30hz fine. Could it be that 6V6 in SE just can't handle it over say 50% volume being only 5W tube?
I've got couple of Hifi SE 6v6 amps, they both don't handle 30hz bass well. It's the type of bass one can hear on those subwoofer vids on YT but with "normal" music it normally doesn't happen. It's not much like a distortion but more of a heavy saturation choking effect. Various values of cathode caps have no effect.
My other amp which is PP amp handles the 30hz fine. Could it be that 6V6 in SE just can't handle it over say 50% volume being only 5W tube?
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I'm not a toob expert, but with high output at such a low frequency, my guess is the output transformer is saturating. "Normal" music usually doesn't go below 40Hz, which happens to be the lowest note on an electric bass guitar.
Details of the actual O/P transformer ratings, the anode/plate voltage and other circuit details would help to indicate a problem area. Trying to squeeze 6 watts out of a 6V6 bottle even with a brand new one, is pushing things a bit. Allowing for a gapped SE O/P transformer to operate 'cleanly' at 30 Hz involves a massive core and even so total distortion (without feedback) would be in excess of 12%.
Just thinking, you've been playing with loads on odd transformer taps. Among other things this changes the damping factor.
O.K. Moving the post titled ''30 Hz distortion'' to this section allows more background relating to the problem . It appears that 6V6dude needs to improve his knowledge of circuit design and the differences defining Hi Fi amplifiers vs basic amplifiers.The O/P transformer is a critical component that will determine the overall performance that can be obtained. Without knowing the specifications of the item used and then following a perusal of the original schematic with its plethora of basic mistakes and the retractions that follow, is a cause for concern. Changing secondary tappings won't help much, as the inductance has to suit the primary load impedance and the desired low frequency response.
6V6 SE is not h-fi.6V6dude said:
That is because PP allows a reasonable size OPT to have enough inductance to go down to low frequencies. SE can't do this without using a huge OPT. Also, PP is likely to have more power - needed for the typical loudspeaker/room and person to hear 30Hz.
No Jan, B+ is fine it was a schematic error. The ams are fine now only the 30hz saturation was something I wondered about. As VaNarn and DF96 mentioned it sounds like an OT is not big enough. These are OTs from an old stereo amp (Trio and some other one), possibly not made to handle 30hz and bellow too well. Listening to "normal" music, I never come across this saturation anyway so it's not a problem. I thought (hoped) maybe the saturation in that range could be caused by something else but it makes sense it's probably the OTs afterall.
In most valve amps the LF limit is set by the OPT. This is not too much of a problem with real music unless you like it really loud.
2x 5W is plenty for me but if really need to get down, I turn on the PP 2x8W Playmaster and take it near the edge of clipping. My sweet spot when I need loud.
Remember we talked about NFB and that I didn't like it? Well, I've implemented NFB in both of the amps I've recently rebuild after all. But just a little to keep mainly the vocals from peaking to distortion and to tidy up the general sound without too much NFB to make it sound sterile. Took a lot of listening and testing to select right values but now I see the real benefit and is worth it.
Remember we talked about NFB and that I didn't like it? Well, I've implemented NFB in both of the amps I've recently rebuild after all. But just a little to keep mainly the vocals from peaking to distortion and to tidy up the general sound without too much NFB to make it sound sterile. Took a lot of listening and testing to select right values but now I see the real benefit and is worth it.
NFB is supposed to make it sound "sterile" - that shows that the amplifier is simply amplifying and not making music itself.
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