I really thought I had, but I obviously hadnt.
The amp has really really come alive with the feedback! Im going to put a pot in the path and do some listening tests like it was recommended.
I was just about to go out as well....!! Social life vs. Amps.... hmmm...
Looks like the pub loses again..
Thanks for the help, still learning
Charlie
Only if Mr. Nyquist is satisfied, then you get oscillation. It's just that positive FB has very limited uses for audio. It's much more helpful for RF where you want everything PFB accomplishes: higher gain, narrower bandwidth (i.e. greater selectivity) higher Zo (less loading of LC tuners i.e. higher Q-factors). It's quite possible to have PFB and remain stable -- done all the time with RF.
For one of my projects, I included variable gNFB, but Mr. Murphy connected the OPT for PFB instead. You had to advance the feedback pot quite a bit before the first oscillations began appearing (~1KHz sine waves) and further still until the OPT saturated, and it began to behave like a Royer (25Hz square waves) at full power. (Which is why you'd prefer to test into a test resistor and o'scope so's you don't deafen yourself.)
Thanks chaps
The amp is at a point where I dont think it needs any more tweaks (to newbie ears anyway), so it has been given to my Mum for Christmas. The deal was that she had to spend some cash on speakers.
So we went to a local HIFI specialist and we both liked the B&W 685's, even though they cost a lot the sound was really good and clear. But there was something missing from the demo, it was like I was listening to a wall instead of a stage. Then I realised that my amp sounds better than the shops expensive SS demo amp. Was very humbling. With the speakers connected to the BH the sounds is amazing. Never heard music like it! My old dear certainly has the best sound system in town.
So thank you to all for your patience and helping me with the build, just a shame I dont get to listen to it anymore!
I was going to post pictures but I cant upload for some reason...
Think the next project is the Red Light District...
Cheers
Charlie
The amp is at a point where I dont think it needs any more tweaks (to newbie ears anyway), so it has been given to my Mum for Christmas. The deal was that she had to spend some cash on speakers.
So we went to a local HIFI specialist and we both liked the B&W 685's, even though they cost a lot the sound was really good and clear. But there was something missing from the demo, it was like I was listening to a wall instead of a stage. Then I realised that my amp sounds better than the shops expensive SS demo amp. Was very humbling. With the speakers connected to the BH the sounds is amazing. Never heard music like it! My old dear certainly has the best sound system in town.
So thank you to all for your patience and helping me with the build, just a shame I dont get to listen to it anymore!
I was going to post pictures but I cant upload for some reason...
Think the next project is the Red Light District...
Cheers
Charlie
The RLD has a classic global feedback sound. Think of your expensive SS amp , but better of course. The friend who built one never really used it after building it and he has very very good taste in equipment.
Allen Wrights PP1 would be a fantastic project which couldn't help but impress.
There are a few partial feedback amps that have been designed on this board and a bit of digging should lead to some inspiration.
Br Cornelius
Allen Wrights PP1 would be a fantastic project which couldn't help but impress.
There are a few partial feedback amps that have been designed on this board and a bit of digging should lead to some inspiration.
Br Cornelius
Just use the RLD bias method into the BH !
Should be the wedding of the year
Yves.
Was going to have a little break for a while, ( to learn some theory
) but this sounds like a nice tweak before I go to fixed bias. And then there's all those red led's left over from the Chrismas Tree, sooooooo......
Charlie,
This might be sidelining you a bit but have you thought single-ended? EL84 or ECL86 based consoles can be had very cheap on Ebay. Ripping out the parts will show you how the "oul hands" did it, then screw the lot to a wooden board. One 12AT7 and two EL84's gets you an RH84. It's an interesting comparison between the RH84 and the Baby Huey.
Shoog,
Forthright personal opinion based on personal experience is good to hear, so thanks for that.
This might be sidelining you a bit but have you thought single-ended? EL84 or ECL86 based consoles can be had very cheap on Ebay. Ripping out the parts will show you how the "oul hands" did it, then screw the lot to a wooden board. One 12AT7 and two EL84's gets you an RH84. It's an interesting comparison between the RH84 and the Baby Huey.
Shoog,
Forthright personal opinion based on personal experience is good to hear, so thanks for that.