So your RH84 uses 100 ohm cathode bias? What OPT's?
I notice the original schematic I have for RH84 uses 130 ohm cathode resistor. First cap after rectifier was 47uF followed by 220uF after a large choke. You may be fine, but you could increase the cathode resistor to bring down the total current draw, I'm probably only stating the obvious. Some PT heat is normal.
I notice the original schematic I have for RH84 uses 130 ohm cathode resistor. First cap after rectifier was 47uF followed by 220uF after a large choke. You may be fine, but you could increase the cathode resistor to bring down the total current draw, I'm probably only stating the obvious. Some PT heat is normal.
The RH84 shows 270 ohm on the cathodes. I am not sure if this is for one channel or for both though? I would assume it is a sound enough design that it doesn't use a shared cathode resistor. I am using 200 ohm resistors right now because it is all that I have.
The OPT's are the stock magnavox's, and this is the 86 chassis which is the little SE maggie. Mine came with magnavox branded Mullard EL84's. As for your concerns with power- I think that the original circuit had more power, or rather the assumption of more power, but it was notcibly a LOT dirtier. The distortion on this amp is so much lower, and the LF responce is a lot cleaner. The midrange is perfect and pops right out there and the Hf responce is as it was in the magnavox.
I think that the reson the magnavox circuit can be cranked more is because it is designed to limit LF extension to around 90hz or so, because I had to give it a lot of boost around 30hz to bring it up, and then it still didn't have the clean output that the RH84 does.
If I keep my EQ flat across the board I can get above 'average' listening levels with 84db speakers. When I cross them over at 90hz and run the rest to a sub I can get over 100db which is plenty for me.
The OPT's are the stock magnavox's, and this is the 86 chassis which is the little SE maggie. Mine came with magnavox branded Mullard EL84's. As for your concerns with power- I think that the original circuit had more power, or rather the assumption of more power, but it was notcibly a LOT dirtier. The distortion on this amp is so much lower, and the LF responce is a lot cleaner. The midrange is perfect and pops right out there and the Hf responce is as it was in the magnavox.
I think that the reson the magnavox circuit can be cranked more is because it is designed to limit LF extension to around 90hz or so, because I had to give it a lot of boost around 30hz to bring it up, and then it still didn't have the clean output that the RH84 does.
If I keep my EQ flat across the board I can get above 'average' listening levels with 84db speakers. When I cross them over at 90hz and run the rest to a sub I can get over 100db which is plenty for me.
I should create one dedicated to maggie SE's, I have tons of pics that I have saved form ebay auctions and found online, as well as multiple circuits they can be built into. Unfortunatly, this might cause prices to climb even higher 
I am hoping the receive the rest of my parts tomarrow so that I can convert my other chassis to an RH84. The chassis polished up nice and i clearcoated it. I ordered up some solen caps for the coupling caps because they were cheap. I am going to have a long period of time between classes tomarrow at college and I think I am going to take a box with the old amps in it and my two nova 6's to the student center. Should be fun for people to watch
http://www.audiokarma.org/forums/showthread.php?t=134055 here is the maggie as it sits now before being modded from the reworked magnavox circuit.
I am hoping the receive the rest of my parts tomarrow so that I can convert my other chassis to an RH84. The chassis polished up nice and i clearcoated it. I ordered up some solen caps for the coupling caps because they were cheap. I am going to have a long period of time between classes tomarrow at college and I think I am going to take a box with the old amps in it and my two nova 6's to the student center. Should be fun for people to watch
http://www.audiokarma.org/forums/showthread.php?t=134055 here is the maggie as it sits now before being modded from the reworked magnavox circuit.
OH yeah! That would be spelled going ... I got my parts today and am wiring everything up right now. So far its going smoothly. I also found more pictures of my last build on my school account so I will probably get them on my site as soon as I find time.
Thanks for the comment about the guitar amp!
Heres some photos of my workbench and some of my other amps:
I got my parts today and am wiring everything up right now. So far its going smoothly. I also found more pictures of my last build on my school account so I will probably get them on my site as soon as I find time.Thanks for the comment about the guitar amp!
Heres some photos of my workbench and some of my other amps:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Alright, so I tried the 47uf on the cathodes- didn't do it for me, I ended up putting 470uf back in. The 47uf rolled the bass off around 50hz or so, but with the 470 It goes very deep without clipping or saturating. It won't rattle windows ( well actually it does a little...!) but it reproduces the full spectrum very well with plenty of bass weight for movies and classical music. I guess it will do rap just fine too, which really does test the amp, but who cares about that since thats not what I'm into.
But was the 47uF a common grade electrolytic? Really, I put binding posts on the top of my SE amp, and "rolled" caps. Better quality poly Solen or Jantzen audio caps, even 5.1uf was a different experience, due to the light weight OPT's. again, I am using TL speakers that don't provide thumping bass, but rather overall balance. However, each of us has different music tastes, and as a musician yourself, i respect your preference. regards
Sparky, I only had cheap grade nichicon's in my parts bin for now. I'm sure high grade elko's sound great, but didn't have time to order some, and it sounds fine as it is.
I am going for overall balance here as well, but since I have low efficiency acoustic suspension speakers (for now) I gotta work with what I have.
I did however find that if I went as high as 1000uf that it got a little sloppy and less able to repond to transients. I think that between 100uf and 470uf is a good mix. I am listening to jazz right now and it sounds oh so sweet
BTW I am working on that website right now. I have a few things left and I may need some input from you guys. I would also like as many pictures as possible of other peoples creations out of this particular amp. I am going to post on audiokarma for permission to use thier photos as well.
Here's a quick teaser!
http://getchellaudio.googlepages.com/102_0710.JPG
I am going for overall balance here as well, but since I have low efficiency acoustic suspension speakers (for now) I gotta work with what I have.
I did however find that if I went as high as 1000uf that it got a little sloppy and less able to repond to transients. I think that between 100uf and 470uf is a good mix. I am listening to jazz right now and it sounds oh so sweet
BTW I am working on that website right now. I have a few things left and I may need some input from you guys. I would also like as many pictures as possible of other peoples creations out of this particular amp. I am going to post on audiokarma for permission to use thier photos as well.
Here's a quick teaser!
http://getchellaudio.googlepages.com/102_0710.JPG
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