I have made several push pull and SE. Hi Mu triode amps, the internal impedance can be as high as 8 ohms even with feadback. best to use Overdamped speakers such as Altec 515, JBl 2220's. and more.
I have horn loaded altec 515's & JBL 2240's no sign of boom. If you use transistors with these speakers they sound bass light.
Phil
I have horn loaded altec 515's & JBL 2240's no sign of boom. If you use transistors with these speakers they sound bass light.
Phil
Hey Magz, I've read through this thread a few times, and I think I remember somewhere you talking about drilling the frames of the chokes in your filaments a little bit to be able to insert a bolt to tighten everything up.. Am I right?
If so, was there any trick to that? I can see that there are already holes through the choke that are just kind of blocked by the frame that holds things together.
One of my filament supplies has a fairly noisy Hammond 159ZJ choke, and I thought maybe it would be worth tightening up both chokes a bit.
If so, was there any trick to that? I can see that there are already holes through the choke that are just kind of blocked by the frame that holds things together.
One of my filament supplies has a fairly noisy Hammond 159ZJ choke, and I thought maybe it would be worth tightening up both chokes a bit.
The trick is to be careful when drilling so that you drill the frame and not the laminations. What I did was to make an indentation in the frame with a punch to center the drill bit, then drill slowly and carefully with a small diameter drill, then follow up with the diameter needed for the bolts. Before drilling I squeezed the frame with big channel lock pliers to bend it against the laminations as much as possible. After drilling I coated the holes with an acrylic conformal coating just in case I scraped any of the lams, then bolted it all together.
I also jammed thin pieces of wood (such as popsicle stick wood) coated with conformal coating (you can use varnish, too) between the center lams and the bobbins wherever there was space.
That helped quite a bit, but I still needed to mount them inside the chassis on Deflex bushings to minimize the vibration transfer to the chassis top.
If you can fit them in the chassis, go for chokes rated twice what your current draw is - I would have used 20A if I could have fit them!
.
Last edited:
Thanks for the info!
I'm using 5A rated chokes with 845's, so there's a bit of breathing room there.. But there's definitely more vibration than I would like with these..
Maybe I can get away with just isolation / dampening bushings.. Where did you order those bushings from?
I made the bushings from sheet Deflex material (sorbothane I believe, from Parts Connexion) using cork boring tools; basically a Deflex washer on top and bottom and a Deflex tube through the oversize bolt hole.
100 Watt SE Amp
Its been quite a while since I have posted anything here so I thought I would take sometime out to make a contribution. I have been working on building a 100 watt per ch SE Amp....it has proved to be difficult for me as I kept on changing the design and layout. The situation now is that the PSU has become so massive that its getting impossible for me to single handedly move the chassis around. Anyway see the pics....I am almost finished and hope to be powering up (the PSU only) over this coming weekend. If its all okay I will soak test it under load for a few days before moving on to making the actual amplifier..... schematics and more pictures to follow later
Its been quite a while since I have posted anything here so I thought I would take sometime out to make a contribution. I have been working on building a 100 watt per ch SE Amp....it has proved to be difficult for me as I kept on changing the design and layout. The situation now is that the PSU has become so massive that its getting impossible for me to single handedly move the chassis around. Anyway see the pics....I am almost finished and hope to be powering up (the PSU only) over this coming weekend. If its all okay I will soak test it under load for a few days before moving on to making the actual amplifier..... schematics and more pictures to follow later
Attachments
Why don't you start a new thread on this build instead of "hi-jacking" this one.
I'm sure there's plenty interested in your project.
I have a question about the caps.
It's not mentioned on our website, but we have a CNC router and can machine holes now too. We need at least a good sketch with hole size and placement dimensions. Though dwg or dxf files are preferred, a pdf or picture of your layout will suffice. Below is a picture of some work we did one weekend.
Attachments
Hey Dave,
I'll be sending more business your way soon. I'm working out the details of The Midlife Crisis V1.1; basically just moving most of the 833 filament supply and all of the 6E5P heater supply off the main chassis, and cleaning up the cooling fan supply a bit too. This way I can use a 20A choke for the filament first L and eliminate the low buzz I get with the 10A choke, put the 6E5P DC heater supply on a separate transformer from the 6E5P B+, drop the noise floor even further by removing the 10A AC from the chassis (it's at 300uV with input shorted now), and reduce the weight of the main chassis by 15 lbs or so.
I'll also be doing a vacuum impregnation of the Hammond 733A 2.5kV main power transformer to get rid of the buzz from that (inaudible from the listening chair but still pisses me off!).
One question:
Can you use Front Panel Express .fpd files for your machining?
I'll be sending more business your way soon. I'm working out the details of The Midlife Crisis V1.1; basically just moving most of the 833 filament supply and all of the 6E5P heater supply off the main chassis, and cleaning up the cooling fan supply a bit too. This way I can use a 20A choke for the filament first L and eliminate the low buzz I get with the 10A choke, put the 6E5P DC heater supply on a separate transformer from the 6E5P B+, drop the noise floor even further by removing the 10A AC from the chassis (it's at 300uV with input shorted now), and reduce the weight of the main chassis by 15 lbs or so.
I'll also be doing a vacuum impregnation of the Hammond 733A 2.5kV main power transformer to get rid of the buzz from that (inaudible from the listening chair but still pisses me off!).
One question:
Can you use Front Panel Express .fpd files for your machining?
I have a Landfall chassis too. It is strong enough to drive a truck over, and very well made. All 0.125 thick aluminum.
I started on this little rack mounted 125 WPC amp right before Motorola laid me off a year and a half ago. It never got finished before I had to pack up my life and move.
Now 18 months later, and 1200 miles further north, it will be finished......I just need to build a new lab first. That is underway now.
I have collected all the pieces for something on the scale of Magz amp, but without the Corvette budget. Maybe a Chevette budget, but I am aiming for 1KW of vacuum tube audio power. Not ready for chassis dimensions yet, but I know who to call.....If Dave can make me one big enough! This will be one BIG and HEAVY amp.....or maybe two.
I started on this little rack mounted 125 WPC amp right before Motorola laid me off a year and a half ago. It never got finished before I had to pack up my life and move.
Now 18 months later, and 1200 miles further north, it will be finished......I just need to build a new lab first. That is underway now.
I have collected all the pieces for something on the scale of Magz amp, but without the Corvette budget. Maybe a Chevette budget, but I am aiming for 1KW of vacuum tube audio power. Not ready for chassis dimensions yet, but I know who to call.....If Dave can make me one big enough! This will be one BIG and HEAVY amp.....or maybe two.
