mhamel
500+ Head-Fier
- Joined
- Jan 30, 2003
- Posts
- 626
- Likes
- 135
Everyone has their own version of "Maxed Out" for this amp, and this is my interpretation of a "Mostly Maxed Out" version. There's definitely more I could do with it, but right now it sounds pretty damn good.
First, I decided to go with an outboard power supply instead of the rail splitter/buffer. I went with the Gilmore power supply, based on the board from HeadAmp.com. It proved to be a bit unstable, but a few gray hairs and some spare parts later, it's running very well.
I also decided to go this route since I can use the power supply for many other amplifier projects. Now all I need to do is add the appropriate power jack to the chassis. Since I most likely won't be using more than one of them at a time, unless I sprout some extra ears or a 2nd head, it should make for a good "universal" supply.
On to the amp. Like I said, this is my version of "Mostly Maxed Out." I'm using 4x1800uF 35v Panasonic FC caps on the board, and 2x10,000uF Panasonic "Audio" caps (pulled out of a Yamaha surround decoder) off-board.
The resistors are all Beyschlag .40w 1% metal film. I've had very good results with these so far, so I'm sticking with them for at least the time being.
The input caps are 1.0uF Sprague Orange Drops, which I managed to fit onto the board, sort-of. A bit of creative lead-bending and some heatshrink tubing and it's all good.
Right now it's got an overall gain of about 11 - which I've found is a bit too low once the crossfeed board is installed. It's powering a pair of DT770Pro/250's, so I think I'll be happier with a gain of around 20-25.
I originally planned on going with a pair of OPA627s, but ended up with the AD8620. In this particular configuration, I found the 627s to be too dark. I think they had a bit deeper bass than the 8620, but overall I preferred the later. I am running it with the current source.
Buffers are 3x stacked EL2002s.
The pot is an Alps Blue 20K. I was trying to buy a 50K, but I got sort of impatient, and I had the 20K on hand, so in it went, and it sounds very good.
Input jacks are from Triode Electronics - they look a lot like one of the Vampire jacks from Welborne, but they're $2.95 each, and built VERY well.
The output is a 1/4" Neutrick locking jack.
You might notice the crazy huge mounting nut on the panel LED. I was looking for something that would work well in the panel thickness I was working with, and came across a few things on Allied's site. This is a "Vandal Proof" panel indicator... the thing is built like a tank, all stainless steel. Just in case vandals decide to attack my amp, at least the LED will be safe.
On to the enclosure. I was originally going to put it into a Hammond 1455 to match the power supply, but I couldn't get everything I wanted on the front panel in place, mainly because I wanted to keep the volume pot board-mounted. A few months ago I came across an old cigar box with a pretty cool shape, built very well, but dirty and a little beaten up. After some cleaning, the finish turned out to be in very good condition, and (to me at least) the other imperfections give it some character.
Unfortunately, I'm not really happy with the front panel layout. I really should have mounted the volume pot on the panel and run leads to the amp board. That way I could have moved the control knobs over to the right about another inch, then moved the jack over to the left to balance it out a bit. I should have also taken the time to do a mock-up in Photoshop before I started cutting... I would have also put the switch on the back panel. But, its ok for now, and f I come across another enclosure that really strikes me, I can always take this apart and redo it.
As for the sound... well, it's still breaking in... but so far - Wow. I'm very impressed. I'd previously been driving my DT770s with a CMoy or off of the headphone out on a modified Velleman preamp. Now I know what the term "Holy****Bass" is all about with these cans. They still need some EQ in the high end, but so far it sounds great!
The jury is still out for me on the crossfeed. Once the amp goes through a good break-in period, I'll spend some time listening to it and decide which way I prefer the sound.
Here are the pics - they are in no particular order:
Mike's Gilmore Power Supply
Mike's Meta42 Amp
-Mike
First, I decided to go with an outboard power supply instead of the rail splitter/buffer. I went with the Gilmore power supply, based on the board from HeadAmp.com. It proved to be a bit unstable, but a few gray hairs and some spare parts later, it's running very well.
I also decided to go this route since I can use the power supply for many other amplifier projects. Now all I need to do is add the appropriate power jack to the chassis. Since I most likely won't be using more than one of them at a time, unless I sprout some extra ears or a 2nd head, it should make for a good "universal" supply.
On to the amp. Like I said, this is my version of "Mostly Maxed Out." I'm using 4x1800uF 35v Panasonic FC caps on the board, and 2x10,000uF Panasonic "Audio" caps (pulled out of a Yamaha surround decoder) off-board.
The resistors are all Beyschlag .40w 1% metal film. I've had very good results with these so far, so I'm sticking with them for at least the time being.
The input caps are 1.0uF Sprague Orange Drops, which I managed to fit onto the board, sort-of. A bit of creative lead-bending and some heatshrink tubing and it's all good.
Right now it's got an overall gain of about 11 - which I've found is a bit too low once the crossfeed board is installed. It's powering a pair of DT770Pro/250's, so I think I'll be happier with a gain of around 20-25.
I originally planned on going with a pair of OPA627s, but ended up with the AD8620. In this particular configuration, I found the 627s to be too dark. I think they had a bit deeper bass than the 8620, but overall I preferred the later. I am running it with the current source.
Buffers are 3x stacked EL2002s.
The pot is an Alps Blue 20K. I was trying to buy a 50K, but I got sort of impatient, and I had the 20K on hand, so in it went, and it sounds very good.
Input jacks are from Triode Electronics - they look a lot like one of the Vampire jacks from Welborne, but they're $2.95 each, and built VERY well.
The output is a 1/4" Neutrick locking jack.
You might notice the crazy huge mounting nut on the panel LED. I was looking for something that would work well in the panel thickness I was working with, and came across a few things on Allied's site. This is a "Vandal Proof" panel indicator... the thing is built like a tank, all stainless steel. Just in case vandals decide to attack my amp, at least the LED will be safe.
On to the enclosure. I was originally going to put it into a Hammond 1455 to match the power supply, but I couldn't get everything I wanted on the front panel in place, mainly because I wanted to keep the volume pot board-mounted. A few months ago I came across an old cigar box with a pretty cool shape, built very well, but dirty and a little beaten up. After some cleaning, the finish turned out to be in very good condition, and (to me at least) the other imperfections give it some character.
Unfortunately, I'm not really happy with the front panel layout. I really should have mounted the volume pot on the panel and run leads to the amp board. That way I could have moved the control knobs over to the right about another inch, then moved the jack over to the left to balance it out a bit. I should have also taken the time to do a mock-up in Photoshop before I started cutting... I would have also put the switch on the back panel. But, its ok for now, and f I come across another enclosure that really strikes me, I can always take this apart and redo it.
As for the sound... well, it's still breaking in... but so far - Wow. I'm very impressed. I'd previously been driving my DT770s with a CMoy or off of the headphone out on a modified Velleman preamp. Now I know what the term "Holy****Bass" is all about with these cans. They still need some EQ in the high end, but so far it sounds great!
The jury is still out for me on the crossfeed. Once the amp goes through a good break-in period, I'll spend some time listening to it and decide which way I prefer the sound.
Here are the pics - they are in no particular order:
Mike's Gilmore Power Supply
Mike's Meta42 Amp
-Mike
