Hotrodding Dynaco Mark III Tube Amps

Hotrodding Dynaco Mark III Tube Amps

Joined: February 2nd, 2002, 1:32 pm

May 15th, 2006, 2:54 am #1

I have a pair of Mark III's that I'm rebuilding, detailing, and upgrading. I know squat about electronics and tube technology. But that's not to stop me! the amps have been significantly upgraded over the last 40 years.

Anyone familar with these amps willing to look at some pics and recommend suitable mods? these drive my JBL L100's. I have a Phase Linear 400 I use for the subs, and a Phase Linear 4000 preamp split with a Paradigm x-30 crossover.

Don
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Joined: July 26th, 2002, 1:52 am

May 15th, 2006, 6:21 pm #2

don't know nuthin' ! might wanna look at quicksilver audio's latest tube amps ,for ideas at least ,they are very simplistic ! the preamp may not be but the amp uses a couple mercury magnetics transformers ,usually el34 tubes ( although 6550 and kt88's can be used) a capacitor and little else !
There is no bull about those things !

Are you running stock l100's ? I have a pair , people talk about doing this that or the other to them but I'll leave them alone . I may build some supro deluxe jbl's with le14/le10/le5/066 drivers and try the Xover out of my sansui sp2000's as they are 4 way.

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Joined: February 2nd, 2002, 1:32 pm

May 15th, 2006, 8:22 pm #3

Not familiar with Quicksilver tube amps, but will do some research.

The L100's are stock. Look like they came from a museum. The cabinets are perfect. Although, I've replaced the foam grilles with a new type of foam that doesn't breakdown. The L100's have 123A-1 woofs, LE-5-2 mids, and LE26 tweets.

I built a pair of subs using Infinity Kappa Perfect 12.1D dual coil drivers. They are fantastic with the Phase Linear 400 driving them. The Paradigm x-over cuts the L100's off at 80hz. Since they aren't doing the heavy lifting any more I may plug the port to tighten up the lower end a bit. I'll use a removable plug. The L100 is fantastic! I love their sound, and there's nothing I'd rather have. There's no substitute for cobalt magnets. Adding a pair of subs takes the L100's to a new level. I'm a retro guy. Old cars and old hifi gear.
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Joined: July 26th, 2002, 1:52 am

May 15th, 2006, 9:31 pm #4

the amp portion is bare bones and will help you visualize what a rock solid power amp requires for hifi.

The dynaco may sound great as long as the components are still good , if they aren't I'd just fix that piecemeal and see how they sound , might not wanna change nuthin !

I may get another pair of L100's or 4311 , but first I need a real amp ! I've got an old sansui that ain't bad but ain't particularly good either ! I've had my eye on yamaha cr-1020 cr-2020 ca-1010 . I think any one of those would do nicely and they have walnut cabs which match my L100's !

I paid 350 for these L100's and with 300 or so more for a good reciever , even if it needs fixing, I just don't see how a man could beat it for the money ! All that for under 1000 and I could blow anything I've seen at circuit city off the map ! circuit city ain't got nothin but PLASTIC ! CHINESE, PLASTIC, STEAMING HORSESHIT !
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Joined: May 2nd, 2001, 1:57 am

May 16th, 2006, 12:23 am #5

I have a pair of Mark III's that I'm rebuilding, detailing, and upgrading. I know squat about electronics and tube technology. But that's not to stop me! the amps have been significantly upgraded over the last 40 years.

Anyone familar with these amps willing to look at some pics and recommend suitable mods? these drive my JBL L100's. I have a Phase Linear 400 I use for the subs, and a Phase Linear 4000 preamp split with a Paradigm x-30 crossover.

Don
There are all sorts of kits to rebuild your MKIII. You can also just rebuild the original circuit with stock parts as well.

I owned a bunch of Dyna stuff, and I used the ST70 with a rebuilt ST35 and a modified pair of Heathkit tube electronic crossovers to bi-amp my Altecs. I also had a pair of MKVI monoblocks, the 120 watt monsters made in 1976.

With the MKIII, basic mods include replacing the tube rectifier with diodes, and cramming in as much filtration as possible. This will enhance headroom and tighten up the bass.

So what have you done already? Lets see those pix!

"Tyranny, like hell, is not easily conquered… What we obtain too cheap, we esteem too lightly: it is dearness only that gives every thing its value. Heaven knows how to put a proper price upon its goods; and it would be strange indeed if so celestial an article as FREEDOM should not be highly rated."
-Thomas Paine
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Joined: February 2nd, 2002, 1:32 pm

May 16th, 2006, 3:16 am #6

I'm going to have the tranny bells gold or nickel plated. The new chassis is nickel plated. I'm considering pulling the caps and replacing them with the Triode Electronics quad-cap upgrade board. No improvement, but will cleans things up. Also going to replace the single tube PC board with the Troide Electronic dual tube upgrade board. Will go with a pair of Sovtek KT88 tubes. Also will replace all the connectors. Will use gold jacks compatible with the JBL's and the Phase Linear gear.





These are the subs I built to support the L100's. They are walnut and as close a match to the JBL cabinets as I could get. Real thumpers. Floors vibrate and you can feel it in your gut! They have JBL blue foam grilles that go around the aluminum supports. The top cabinet stacks upside down on the bottom cab - not as they are pictured.



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Joined: July 26th, 2002, 1:52 am

May 16th, 2006, 2:32 pm #7

I thought you were talking about a reciever , cause the old dynaco I had was a reciever . What you've got there is the essential parts of a really good tube amp , you can fool around with the caps ,tubes and resistors as needed .
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Joined: May 2nd, 2001, 1:57 am

May 16th, 2006, 7:21 pm #8

I'm going to have the tranny bells gold or nickel plated. The new chassis is nickel plated. I'm considering pulling the caps and replacing them with the Triode Electronics quad-cap upgrade board. No improvement, but will cleans things up. Also going to replace the single tube PC board with the Troide Electronic dual tube upgrade board. Will go with a pair of Sovtek KT88 tubes. Also will replace all the connectors. Will use gold jacks compatible with the JBL's and the Phase Linear gear.





These are the subs I built to support the L100's. They are walnut and as close a match to the JBL cabinets as I could get. Real thumpers. Floors vibrate and you can feel it in your gut! They have JBL blue foam grilles that go around the aluminum supports. The top cabinet stacks upside down on the bottom cab - not as they are pictured.



You don't need us, you just need space to work LOL!

Try brushing some chassis black on the tranny cores before you reassemble them.

As for tubes, I have always preferred the Slovakian/Tesla tubes to the Sovteks. Even the Svetlanas sound better to me.

For room, you can just eliminate that octal socket on the back since you are not powering any devices from it.

I think I would go ahead and use three-prong AC cords on it, and bring everything to a common power strip for a king of star ground. Use big cords, and replace the cord on the strip with a big one as well. Look for some fast, 3 or 5 amp diodes and just use two for the power supply to speed things up. I used to keep a bunch of 1N5408 diodes around for all diode replacements. I'm sure Triode could suggest something better.

http://www.fairchildsemi.com/pf/1N/1N5408.html

As always, I like to get my parts from Mouser. Good prices, no minimum.

http://www.mouser.com

I really dig the subs. Share your recipe?

"Tyranny, like hell, is not easily conquered… What we obtain too cheap, we esteem too lightly: it is dearness only that gives every thing its value. Heaven knows how to put a proper price upon its goods; and it would be strange indeed if so celestial an article as FREEDOM should not be highly rated."
-Thomas Paine
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Joined: February 2nd, 2002, 1:32 pm

May 16th, 2006, 10:00 pm #9

Tom, Where would the diodes go in the power circuit? Definately going with a beefy grounded AC power cords.

I am really happy with the subs. Initially I was going to go with a JBL 2245H, but decided against the 8 cu. ft. box. Finally realized it would have to be a 12" driver in order to keep the cabinet size reasonable. I wanted two cabinets so I could use them as pedestals for the L100s if I so chose, or stack them out of sight. I settled on the dual voice coil Infinity 12.1D. They are killer drivers! I designed 1.75 cu ft enclosures with 4" x 12" ports. I have Ford and JBL blue blood in my veins. I wanted to use JBLs for the subs, but the Kappa 12.1D performed best in the small footprint enclosure. The walnut veneer looks fantastic with the L100s. They all actually look like a set.

While the Mark IIIs are being rebuilt I'm using a Phase linear 400 to drive the L100s. I have a 10' x 10' spare room where I play with my hobbies (computers, hifi, etc.). In this room I have the two Phase Linear 400 power amps (750 Watts each), the JBL L100s, and the two subs. It's like being in the front row of a Blue Cheer concert! It's interesting how sound travels. The bass from the subs is actually louder in other rooms of the house. I love listening to "Long Time Gone" by CSN. The base line vibrates the entire house at a 32 db setting on the PL3000 preamp. I love it! The Falcon's tied up at the body shop so I'm playing with hifi gear to keep busy.
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Joined: May 2nd, 2001, 1:57 am

May 17th, 2006, 1:16 am #10

Correct me if I am mistaken but it appeared to me from the pix that the 5AR4 rectifier tube have been replaced by the diodes I think I see in the lower left of the open chassis pix. Izzat right? If so, I would replace them with two high current ones. Kevin was asking about subs a while back, I will try to direct him to this thread.

"Tyranny, like hell, is not easily conquered… What we obtain too cheap, we esteem too lightly: it is dearness only that gives every thing its value. Heaven knows how to put a proper price upon its goods; and it would be strange indeed if so celestial an article as FREEDOM should not be highly rated."
-Thomas Paine
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