if you put the ccs on top of the 5687 the gain will be about 17x.
I dont know what value the anode resistor on the 5687 now is? If its large than the gain should be at least 10x. (i'm guessing here) so you increase the sensitivity 2x. The d3a has a gain of 70x; so thats a whole different story: 7x the sensitivity. if you want 2v pp sensitivity: 70x 2v = 140v to the grid of the 2a3. the 2a3 has about 4x gain, so the abs. max swing would be 4x 140=560v pp. so if there's no feedback, your amplifier wil be more sensitive than the wanted 2v. (with the d3a)
If you want 2v rms sensitivity, the d3a is overkill. (but it wouldnt hurt) 2v rms is 5.64v pp. 5.64x70x4= 1579.2v pp. Of course we should be calculating the other way around. I presume you're V+ is about 300 v? so your max swing on the OPT should be about 300v pp. 300v /4=75v pp. so you need at least 75v pp on your grid of the 2a3. so for 2v rms sensitivity (5.64v pp) its 75v/5.64v= 13.3x. In this case you need a minimum gain of about 14x. For 2v pp its: 75v / 2v = 37.5x.
What I would do is this: if I wanted 2vrms I would use the 5687 with a ccs. If I wanted 2v pp I would use the d3a with a ccs.
I dont know what value the anode resistor on the 5687 now is? If its large than the gain should be at least 10x. (i'm guessing here) so you increase the sensitivity 2x. The d3a has a gain of 70x; so thats a whole different story: 7x the sensitivity. if you want 2v pp sensitivity: 70x 2v = 140v to the grid of the 2a3. the 2a3 has about 4x gain, so the abs. max swing would be 4x 140=560v pp. so if there's no feedback, your amplifier wil be more sensitive than the wanted 2v. (with the d3a)
If you want 2v rms sensitivity, the d3a is overkill. (but it wouldnt hurt) 2v rms is 5.64v pp. 5.64x70x4= 1579.2v pp. Of course we should be calculating the other way around. I presume you're V+ is about 300 v? so your max swing on the OPT should be about 300v pp. 300v /4=75v pp. so you need at least 75v pp on your grid of the 2a3. so for 2v rms sensitivity (5.64v pp) its 75v/5.64v= 13.3x. In this case you need a minimum gain of about 14x. For 2v pp its: 75v / 2v = 37.5x.
What I would do is this: if I wanted 2vrms I would use the 5687 with a ccs. If I wanted 2v pp I would use the d3a with a ccs.
The ASL Tulip is a 2 stage 12AX7 - 2A3 design
Mine sounded very nice though I had problems with hum. Unfortunately I can't find the schematic to send to you.
If building from scratch I'd seriously consider an Aikido (John Broskie's Guide to Tube Circuit Analysis & Design) input/driver stage.
Mine sounded very nice though I had problems with hum. Unfortunately I can't find the schematic to send to you.
If building from scratch I'd seriously consider an Aikido (John Broskie's Guide to Tube Circuit Analysis & Design) input/driver stage.
Finally reached a conclusion
I think I have come to a conclusion...I am going to go back to basics and build this amp (Clarion) as per the original design add the CCS to the plate of the 5687. I am going to use two separate driver tube sockets and use 1/2 of a 5687 per channel leaving the other 1/2 unused. This will allow the flexibility of adding an extra gain stage using the unused 1/2 of the 5687 or I can change over to the D3a, one tube per side. Having built the layout like this I will undoubtedly tinker with the driver stage after it is built and try all these topologies at some point down the road. Maybe even a few others too.
You guys have been great! I will post some updates and pics as I progress for those interested.
Right now I have the 4 sides of the chassis and the end corners all cut from some Spanish Modena (dark heavy grain, almost as dark as ebony in some places) and the parts all bagged up in baggies and labeled. I have some work to do, I better get started!
Jeff
I think I have come to a conclusion...I am going to go back to basics and build this amp (Clarion) as per the original design add the CCS to the plate of the 5687. I am going to use two separate driver tube sockets and use 1/2 of a 5687 per channel leaving the other 1/2 unused. This will allow the flexibility of adding an extra gain stage using the unused 1/2 of the 5687 or I can change over to the D3a, one tube per side. Having built the layout like this I will undoubtedly tinker with the driver stage after it is built and try all these topologies at some point down the road. Maybe even a few others too.
You guys have been great! I will post some updates and pics as I progress for those interested.
Right now I have the 4 sides of the chassis and the end corners all cut from some Spanish Modena (dark heavy grain, almost as dark as ebony in some places) and the parts all bagged up in baggies and labeled. I have some work to do, I better get started!
Jeff
Hello Jeff,
Good to know you come to the conclusion. Build the amp first and tweak it later. The important thing is get a good pair of output transformer that affect the sound the most. Use double choke fitler if possible for best B+ ripple filtering. It would allow you to adjust the B+ by changing the value of the first input capacitor.
Have fun.
Happy New Year,
Johnny
Good to know you come to the conclusion. Build the amp first and tweak it later. The important thing is get a good pair of output transformer that affect the sound the most. Use double choke fitler if possible for best B+ ripple filtering. It would allow you to adjust the B+ by changing the value of the first input capacitor.
Have fun.
Happy New Year,
Johnny
2.5K vs. 3.5K tap on the OPT
Quick question,
I am using the James 6112HS in place of the UBT OPT Jim Hagerman used for the Clarion. The UBT has a single 3K primary and the James has the 2.5K and 3.5K. I was wondering which of these I should use sice I don't have a 3K. Also, should I make any adjustments to my cathode resistor value since I will be using a different primary impedence?
Thanks,
Jeff
Quick question,
I am using the James 6112HS in place of the UBT OPT Jim Hagerman used for the Clarion. The UBT has a single 3K primary and the James has the 2.5K and 3.5K. I was wondering which of these I should use sice I don't have a 3K. Also, should I make any adjustments to my cathode resistor value since I will be using a different primary impedence?
Thanks,
Jeff
Progress
Here is a few picks of my layout. I just finished the chassis today, still need to drill the top and bolt the top to the sides but all in all it is basically complete.
The sides are Spanish Modena, a very dry, brittle, and light weight hardwood I found at a specialty hardwood store in Dallas, TX. The top is strips 1"x0.5" and 19" long of White Tiger Maple laminated together to make a 1/2" thick plank. I did the lamination like this to bring out the multiple stripes that are best seen on the cut edge of the Maple. the grain has a 3D dimension to it not seen in the photos at all.
Binding posts are from VT4C and James. The IEC filter is a Tyco and the pot is a Alps Blue Velvet (will be shunt moddded).
Hard part is almost over, just need to drill the plank and wire it up!
Next pics will be upon completion, hopefully with some traces.
Jeff
Here is a few picks of my layout. I just finished the chassis today, still need to drill the top and bolt the top to the sides but all in all it is basically complete.
The sides are Spanish Modena, a very dry, brittle, and light weight hardwood I found at a specialty hardwood store in Dallas, TX. The top is strips 1"x0.5" and 19" long of White Tiger Maple laminated together to make a 1/2" thick plank. I did the lamination like this to bring out the multiple stripes that are best seen on the cut edge of the Maple. the grain has a 3D dimension to it not seen in the photos at all.
Binding posts are from VT4C and James. The IEC filter is a Tyco and the pot is a Alps Blue Velvet (will be shunt moddded).
Hard part is almost over, just need to drill the plank and wire it up!
Next pics will be upon completion, hopefully with some traces.
Jeff
Attachments
A little further along
Just completed the chassis. It is all hand built from scratch. Again, the sides are Spanish Modena and the top is laminated White Tiger Maple. These are better photos and the 3D like appearance of the grain is now seen. On the bottom I used some Cherry veneer ply (3 layer) and glued it down to give it more strength across the laminations.
Seen here is all the connectors (Vampire and Connex) and x2 chokes and x2 2.5vct filament transformers. The vent plates for the tube sockets were purchased from VT4C.com. The James 6112HS output transformers are from TCTubes.com (best deal I have found with s/h included). The power transformer is Hammond as well, disassembled ans mounted sideways with a hand built cap out of the same wood as sides and top. Caps are ASC 45uF 370vac. I will parallel these with a 10uF Solen on each side for a total of 100uF as the last caps before the output stage. The 200uF between the 2 chokes will be a combination of Nichicon and Solen as well. I haven't decided on the 100uF called for at the driver stage, depends on how much real estate I have under the chassis as I get going. Either Elna Cerafine or a combination of Solen and ASC.
Hard part is done, the rest is a piece of cake. Should have it done by tomorrow afternoon if all goes well.
Remainder of parts are PRP resistors, Silver 18 & 22 gauge wire, Black Gate bypass, and Copper foil in oil coupling caps. I also will be using the K&K audio CCS on the drivers for plate load.
Jeff
Just completed the chassis. It is all hand built from scratch. Again, the sides are Spanish Modena and the top is laminated White Tiger Maple. These are better photos and the 3D like appearance of the grain is now seen. On the bottom I used some Cherry veneer ply (3 layer) and glued it down to give it more strength across the laminations.
Seen here is all the connectors (Vampire and Connex) and x2 chokes and x2 2.5vct filament transformers. The vent plates for the tube sockets were purchased from VT4C.com. The James 6112HS output transformers are from TCTubes.com (best deal I have found with s/h included). The power transformer is Hammond as well, disassembled ans mounted sideways with a hand built cap out of the same wood as sides and top. Caps are ASC 45uF 370vac. I will parallel these with a 10uF Solen on each side for a total of 100uF as the last caps before the output stage. The 200uF between the 2 chokes will be a combination of Nichicon and Solen as well. I haven't decided on the 100uF called for at the driver stage, depends on how much real estate I have under the chassis as I get going. Either Elna Cerafine or a combination of Solen and ASC.
Hard part is done, the rest is a piece of cake. Should have it done by tomorrow afternoon if all goes well.
Remainder of parts are PRP resistors, Silver 18 & 22 gauge wire, Black Gate bypass, and Copper foil in oil coupling caps. I also will be using the K&K audio CCS on the drivers for plate load.
Jeff
Attachments
I use some stuff from Home Depot, it is a 440 grit sanding product that is purple foam, about 2.5inx5in sheets. I go around them with these sanding sheets until they sparkle then I shoot a coat of clear lacquer over them.
Sorry I cannot remember the exact name for these sanding sheets but look for purple at the sand paper isle, I am sure you will be able to find it. If your caps are particularly rough, start with the 220, then graduate to the 330 then 440 grits. I am not exactly sure what the cap cans are made from, some sort of alloy that appears to have aluminum. It makes a very fine black powder when you sand it and this stuff will stain your clothes. Didn't come all the way out after 3 washes on my white t-shirt.
Be sure to use real lacquer. I used enamel once but it causes a cloudy white appearence to the finish as you get it to a good thickness. The lacquer does a better job of getting a thicker coat without clouding. Multiple thin coats with a 440 sand in between is best. Lacquer is pretty thin and will run easy so go light.
Jeff
It is all about the tools....you have the right tools you will get the right results, period. Of course you have to know how to use them but that is the easy part.
My workshop consists of a table saw, miter box saw, belt sander, drill press, and planer as staples. You can never have enough good quality clamps either. If you ever see a special at Home Depot or in garage sales, buy them. I am always wishing I had more clamps (I have about 12 good ones but think I need about 30 at times!)
And always use the old saying "measure twice and cut once". I take my time with everything, I learned early that haste creates lots of waste. I have ruined $100's of exotic wood when I first started.
For me the wood working is almost 3/4ths of the fun. I have thought about building chassis for hire but not sure I would have the time. If I did it for a living I would go broke b/c I can't do tis stuff very fast.
Jeff
Running for a week or so now
I haven't posted on this thread since I got her up and running. I had some problems at first that ended up simply being a bad 5687 tube. I had another used one that worked and it sounded great. Since then I ordered some good NOS 5687 tubes and also got a pair of NOS NIB RCA 2A3's too. It is up and running with these "upgrades for about a week now and I am really likeing it more and more as it gets broken in. The first batch of K&K CCS were actually bad and I had to send them back for replacements so I just went with a 10K plate load resistor and a bypassed cathode. It has enough gain to get some decent volume but it will not drive to clipping. I will have the CCS on it in about 2-3 days and I am hoping for a little more "ooommpphh" from it. All in all I like it very much though and I can achieve good listening volumes the way it is just fine.
It actually has more bottom end than I expected, about as much as my S5 502-K kit amp 8wpc amp did! (I think that amp was more like 5wpc though in reality).
I built this one as my first DHT with intentions to sell it eventually but now I am having a hard time imagining that.
I will try the CCS soon and will report back on how it works. As far as the D3a, I ended up getting 4 of them and now I have to build something that uses them. I might try that "New 2A3" posted earlier on this thread, nor sure yet. Also thinking of a 2A3 Self inverting push pull (SIPP) like the Oddblocks use and use the D3a to drive them. So many choices out there and so little time!
Jeff
I haven't posted on this thread since I got her up and running. I had some problems at first that ended up simply being a bad 5687 tube. I had another used one that worked and it sounded great. Since then I ordered some good NOS 5687 tubes and also got a pair of NOS NIB RCA 2A3's too. It is up and running with these "upgrades for about a week now and I am really likeing it more and more as it gets broken in. The first batch of K&K CCS were actually bad and I had to send them back for replacements so I just went with a 10K plate load resistor and a bypassed cathode. It has enough gain to get some decent volume but it will not drive to clipping. I will have the CCS on it in about 2-3 days and I am hoping for a little more "ooommpphh" from it. All in all I like it very much though and I can achieve good listening volumes the way it is just fine.
It actually has more bottom end than I expected, about as much as my S5 502-K kit amp 8wpc amp did! (I think that amp was more like 5wpc though in reality).
I built this one as my first DHT with intentions to sell it eventually but now I am having a hard time imagining that.
I will try the CCS soon and will report back on how it works. As far as the D3a, I ended up getting 4 of them and now I have to build something that uses them. I might try that "New 2A3" posted earlier on this thread, nor sure yet. Also thinking of a 2A3 Self inverting push pull (SIPP) like the Oddblocks use and use the D3a to drive them. So many choices out there and so little time!
Jeff
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