The latest post on the KT88SE builder's thread diverging from the KT88 to the 300B:
"Jeff, since you are ready to build the 300B SE, start a new thread and I'll chime in as catch up to building it.
Questions:
1. Which JEL 300B SE amp are you going to build exactly?...
2. Monoblock or Stereo?...
3. What will be the Edcor TX and choke design values because I might still go with Walton's 300B because I only have matched NOS Sylvania 6SN7GTB's?...
Pending on the values, I am in for the Edcor design PTX and chokes - better choice than Hammond!
I have the Hammond iron for the SE KT88, and for me, it looks like junk - very thin and frail wiring. I've heard it's also prone to buzzing, noise in refined applications - so I am mounting them to the chassis plate with rubber washers and grommets for electromechanical isolation. However, there are those who are perfectly happy with Hammond. I'll see how it turns out...
I should have gone with Edcor in the first place even with their blue color and all, it's better spec'd too with 200ma instead of 175ma, which doesn't leave much for dynamics or headroom. Sensing that Hammond doesn't have a 200ma 375V PTX in their line up, all of a sudden, they've listed the 273BX as 201ma (1 ma better than Edcor) without any without any design change to the transformer. I emailed the HQ in Canada to be sure. Even their OPT are not spec'd 20-20khz, and bass is where it's at with OPT. I am with you, Jeff - EDCOR!
This is where I got my ASC motor run caps - inexpensive and they sell mounts too. I think the 47uF for the PSU is for an arbitrary value for polypropylene or electrolytic caps. I am using the 50uF ASC motor run caps as they are well within the 10% tolerance anyway. Here is the link:
ASC Capacitors - X386S-50-10-440 - Allied Electronics
They even have the 7.5uF ASC that Derrick was trying to find, and ended up using two 15uF... "
88man,
I think I am going with the JEL monoblock DX design. The JEL will allow you to use your 6SN7GTB tubes in the driver position.....
I will state here what I mentioned before in the KT88 thread.
I have asked Edcor to design a replica of the Angela Universal power transformer as well as the chokes required for the JEL SE300B DX. I am going to pay the first design fees of $40 each part so after the design is finished subsequent DIYers can purchase these at regular cost. I am not yet sure what the final cost will be but judging from there comparable power transformers (and chokes not listed on their website) I imagine the power transformer will run between $95 and $110 USD, The Chokes will likely fall in the range of $25 to $45 each as well. I am not sure if the chokes will be open bracket or bell ended. Personally I like the open bracket as I prefer to mount underneath the chassis.
The OPT from Edcor that will work in this design sells for $83 each. So I figure for a monobock set of amps built with all Edcor iron you will be looking at about $500 give or take $50 either way depending on what the final prices will be.
Here are the links to the 2 websites most of the design will come from on this build:
300B Mk1 Tube Amplifier
And
SE300B classic and DX
More to come.....
Jeff
"Jeff, since you are ready to build the 300B SE, start a new thread and I'll chime in as catch up to building it.
Questions:
1. Which JEL 300B SE amp are you going to build exactly?...
2. Monoblock or Stereo?...
3. What will be the Edcor TX and choke design values because I might still go with Walton's 300B because I only have matched NOS Sylvania 6SN7GTB's?...
Pending on the values, I am in for the Edcor design PTX and chokes - better choice than Hammond!
I have the Hammond iron for the SE KT88, and for me, it looks like junk - very thin and frail wiring. I've heard it's also prone to buzzing, noise in refined applications - so I am mounting them to the chassis plate with rubber washers and grommets for electromechanical isolation. However, there are those who are perfectly happy with Hammond. I'll see how it turns out...
I should have gone with Edcor in the first place even with their blue color and all, it's better spec'd too with 200ma instead of 175ma, which doesn't leave much for dynamics or headroom. Sensing that Hammond doesn't have a 200ma 375V PTX in their line up, all of a sudden, they've listed the 273BX as 201ma (1 ma better than Edcor) without any without any design change to the transformer. I emailed the HQ in Canada to be sure. Even their OPT are not spec'd 20-20khz, and bass is where it's at with OPT. I am with you, Jeff - EDCOR!
This is where I got my ASC motor run caps - inexpensive and they sell mounts too. I think the 47uF for the PSU is for an arbitrary value for polypropylene or electrolytic caps. I am using the 50uF ASC motor run caps as they are well within the 10% tolerance anyway. Here is the link:
ASC Capacitors - X386S-50-10-440 - Allied Electronics
They even have the 7.5uF ASC that Derrick was trying to find, and ended up using two 15uF... "
88man,
I think I am going with the JEL monoblock DX design. The JEL will allow you to use your 6SN7GTB tubes in the driver position.....
I will state here what I mentioned before in the KT88 thread.
I have asked Edcor to design a replica of the Angela Universal power transformer as well as the chokes required for the JEL SE300B DX. I am going to pay the first design fees of $40 each part so after the design is finished subsequent DIYers can purchase these at regular cost. I am not yet sure what the final cost will be but judging from there comparable power transformers (and chokes not listed on their website) I imagine the power transformer will run between $95 and $110 USD, The Chokes will likely fall in the range of $25 to $45 each as well. I am not sure if the chokes will be open bracket or bell ended. Personally I like the open bracket as I prefer to mount underneath the chassis.
The OPT from Edcor that will work in this design sells for $83 each. So I figure for a monobock set of amps built with all Edcor iron you will be looking at about $500 give or take $50 either way depending on what the final prices will be.
Here are the links to the 2 websites most of the design will come from on this build:
300B Mk1 Tube Amplifier
And
SE300B classic and DX
More to come.....
Jeff
T-Rex 300B
Maybe you all have seen this. Great article, nice power supply. Looks like a good candidate.
The T-Rex SET Amplifier -- A DIY Project Article By Dick Olsher And John Broskie
Maybe you all have seen this. Great article, nice power supply. Looks like a good candidate.
The T-Rex SET Amplifier -- A DIY Project Article By Dick Olsher And John Broskie
Good to move the discussion in a separate thread.
Both approaches are very attractive, one is very simple and linear, the other more complicated.
I have to say that, at least in theory, the regulated PSU make sense as much as the CCS for the cathodes. This is actually one of the reason why I was also interested to the tubelab approach.
What I am not sure about the T-Rex, is that sound to me as "I want tubes and tubes only" approach. I have the feeling that tubes are great for amplification, but in other business, as regulation, solid state can be a better solution.
For what concern me I would like to go for a monoblock, hoping to keep the cost of the PSU reasonable.
Jeff what design of PSU do you want to go for ? 20 H/400mA that's a huge piece of iron !! Is this the choke you asked Edcor to produce ?
As OPT I think I will settle for the Hashimoto H-20-3.5U, I have the constrain that I need the 4 ohm tap, that Tango for example does not have it.
As I am a kind of gipsy, now I live in a 100V country, but sooner or later I will move again to a 220V country, so I would really approciate if I could find a power transformer that has these two input. The Angela replica you proposed, would be great for me, but I am not sure I can run 20 % down. Maybe Edcon could accomodate this in the custom design.
From Hashimoto I saw that there is the possibility to have the PT-220 with 220V, but I still did not understand if it is 220V only or it has different taps.
Let's see what comes out. This time I will build prototypes before assembling the chassis 🙂
Merry Christmas,
Davide
P.S. In Japan this is a working day :-(
Both approaches are very attractive, one is very simple and linear, the other more complicated.
I have to say that, at least in theory, the regulated PSU make sense as much as the CCS for the cathodes. This is actually one of the reason why I was also interested to the tubelab approach.
What I am not sure about the T-Rex, is that sound to me as "I want tubes and tubes only" approach. I have the feeling that tubes are great for amplification, but in other business, as regulation, solid state can be a better solution.
For what concern me I would like to go for a monoblock, hoping to keep the cost of the PSU reasonable.
Jeff what design of PSU do you want to go for ? 20 H/400mA that's a huge piece of iron !! Is this the choke you asked Edcor to produce ?
As OPT I think I will settle for the Hashimoto H-20-3.5U, I have the constrain that I need the 4 ohm tap, that Tango for example does not have it.
As I am a kind of gipsy, now I live in a 100V country, but sooner or later I will move again to a 220V country, so I would really approciate if I could find a power transformer that has these two input. The Angela replica you proposed, would be great for me, but I am not sure I can run 20 % down. Maybe Edcon could accomodate this in the custom design.
From Hashimoto I saw that there is the possibility to have the PT-220 with 220V, but I still did not understand if it is 220V only or it has different taps.
Let's see what comes out. This time I will build prototypes before assembling the chassis 🙂
Merry Christmas,
Davide
P.S. In Japan this is a working day :-(
The Edcor designs I have requested are for an exact replica of the Angela power transformer (universal). I have also asked for a 10H 125mA choke and a 8H 65mA choke. I am looking at the Deluxe version at the JEL website for the Monoblocks.
Yes, Edcor can make anything you wish for an additional fee of $40. This is the cheapest most reasonable company out there for design fees! You will still be able to benefit from the chokes I will have designed as I will have already paid the design fees for these.
I would bet you could get by using the 110V transformer at 100V without much compromise. You could also change some of the resistor values slightly too if needed.
Nikon, If you could find a few more of those rotary switches in Japan I would gladly pay you for your troubles in getting them to me, they look very nice, I have not seen anything comparable at Mouser, Digikey, or elsewhere I have looked. How much did they cost you in appx USD, do you recall?
Jeff
Yes, Edcor can make anything you wish for an additional fee of $40. This is the cheapest most reasonable company out there for design fees! You will still be able to benefit from the chokes I will have designed as I will have already paid the design fees for these.
I would bet you could get by using the 110V transformer at 100V without much compromise. You could also change some of the resistor values slightly too if needed.
Nikon, If you could find a few more of those rotary switches in Japan I would gladly pay you for your troubles in getting them to me, they look very nice, I have not seen anything comparable at Mouser, Digikey, or elsewhere I have looked. How much did they cost you in appx USD, do you recall?
Jeff
The Angela is rated 120 V, so it meand that I would be 20% off, not 10 %. Playing with the primary voltage is annoying, as all the secondaries would be off, not only the HT. I had enought trouble with the PSU of the KT88, I don't want to go the same way. I'll ask edcor how much would be to ship to Japan, or will try to find a provider in Japan.
Just one question, what's the difference between a "good" power transformer and a bad one ?
I also already have a 3.5 KW step up-down transformer. Maybe I can just set it up nicely to have a 100 V source in Europe. They always say to to do it with power amplifiers, but I don'r really understand why. If the transformer is big enough. Somewhere outside your apartment there is a transformer.
Changing all the PTW in three years would be painful, especially with monoblocks :-(
BR,
Davide
Just one question, what's the difference between a "good" power transformer and a bad one ?
I also already have a 3.5 KW step up-down transformer. Maybe I can just set it up nicely to have a 100 V source in Europe. They always say to to do it with power amplifiers, but I don'r really understand why. If the transformer is big enough. Somewhere outside your apartment there is a transformer.
Changing all the PTW in three years would be painful, especially with monoblocks :-(
BR,
Davide
First of all, I do not want to offend anybody today 
or get into any ideological discussion
.
But even I, not being an expert in tube technology at all, know that the idea of building a 300B amp with a cascaded 6sn7 is not clever any more. There is a lot of information right on this forum that tells you that if you do not believe me.
Any mu-stage, mu-follower, drd design, the already mentioned T-rex, or this one Gary Pimm's DIY audio pages will give you a lot more pleasure for the buck.
or get into any ideological discussion .But even I, not being an expert in tube technology at all, know that the idea of building a 300B amp with a cascaded 6sn7 is not clever any more. There is a lot of information right on this forum that tells you that if you do not believe me.
Any mu-stage, mu-follower, drd design, the already mentioned T-rex, or this one Gary Pimm's DIY audio pages will give you a lot more pleasure for the buck.
Jaap,
I don't think anybody here would be offended but to tell the truth, most of us (I think 3 or 4) involved in this new thread are fairly new to the hobby. I myself want to keep things simple rather than clever. The JEL and Walton (essentially the same basic circuit) are well tested and fairly easy to implement. Maybe a year or 2 from now I will be ready to try something a little more clever but for now I am still getting my feet wet with DHTs and would like to have fun putting something together I understand and is not too difficult to build. Thanks for the ideas though, I will certainly keep all these in mind for future adventures.
Merry Christmas,
Jeff
I don't think anybody here would be offended but to tell the truth, most of us (I think 3 or 4) involved in this new thread are fairly new to the hobby. I myself want to keep things simple rather than clever. The JEL and Walton (essentially the same basic circuit) are well tested and fairly easy to implement. Maybe a year or 2 from now I will be ready to try something a little more clever but for now I am still getting my feet wet with DHTs and would like to have fun putting something together I understand and is not too difficult to build. Thanks for the ideas though, I will certainly keep all these in mind for future adventures.
Merry Christmas,
Jeff
I reacted because because when i was still less expierenced than I am now I also started this hobby with the cascaded 6sn7 => 300B. I consider this now as a (expensive) mistake and hope that others can cut corners.
I now think that if you want to combine "simple and clever" you better start with the el84 (or russian equivalent). I also think now that most people are better off with a PP amp. For a starter one of the proven designs (tubelabs, pete millett, etc.) that provide a PCB is also a good idea, less mistakes and easy to build (not so easy to tweak). If you insist on SE look at the RH84. You can always built your 300B amp later 😛
But I also realize that everybody has to find his own way through the tube jungle to the Sierra Nirvana
merry christmas
well 1000 volts of B+ is indeed too much for anybody with a family (including me), so this was not such a good suggestion I admit
Ok Jaap, you got my attention with the T-rex. I barely noticed it at first. BTW I have built about 10 different amps altogether over the past couple of years, So I am not cutting my teeth at this point. Just cutting my DHT teeth. So, convince me some more. Who knows, I might have to have the moderator change the name of this thread when it is all said and done.
Have you built the T-rex? The more I look at it the more I like it. I am quite partial to the 5687 tube. I have built a few different things with it. One of my favorite is the Simple 5687 preamp found at DIYparadise.com.
I am wondering about the OPTs with the T-rex....I have looked at the Lundahl 1664 and it is not too terribly expensive. The Plitrons are a bit out of my price range at this point. I wonder if one could sub the James 6123HS sucessfully in this amp.
Which amp did you ultimately end up building?
Thanks,
Jeff
Have you built the T-rex? The more I look at it the more I like it. I am quite partial to the 5687 tube. I have built a few different things with it. One of my favorite is the Simple 5687 preamp found at DIYparadise.com.
I am wondering about the OPTs with the T-rex....I have looked at the Lundahl 1664 and it is not too terribly expensive. The Plitrons are a bit out of my price range at this point. I wonder if one could sub the James 6123HS sucessfully in this amp.
Which amp did you ultimately end up building?
Thanks,
Jeff
70VDC source?
Can anybody tell me where the 70VDC comes from on the T-rex? I did not notice a seperate transformer for this. I did notice a 70VDC "tap" at the top of the second 5687 tube. Is this the source of the 70VDC to raise the filaments? Just making sure.
Jeff
Can anybody tell me where the 70VDC comes from on the T-rex? I did not notice a seperate transformer for this. I did notice a 70VDC "tap" at the top of the second 5687 tube. Is this the source of the 70VDC to raise the filaments? Just making sure.
Jeff
Don't be seduced by tubes! Let's keep our focus. An expert Dutch speaker maker once told me, "don't be seduced by drivers," as I implored him when I was building a speaker system with the finest drivers available.
There have been dozen's documented builders for the Walton and the JEL 300B SE Amps worldwide who have achieved great sonic success. For beginners like myself and perhaps a few others, we need to place trust in the example of many builders who have consistently attained the same level of success. The Walton and JEL circuits are the real deal with full documentation. I personally like the 6SN7 driver tube - it's one of the reasons I am even building tube projects. I've heard what it does in the Blue Velvet preamp, AE-3, and Cary amps.
I am staying with the Walton or JEL 300B guys!
There have been dozen's documented builders for the Walton and the JEL 300B SE Amps worldwide who have achieved great sonic success. For beginners like myself and perhaps a few others, we need to place trust in the example of many builders who have consistently attained the same level of success. The Walton and JEL circuits are the real deal with full documentation. I personally like the 6SN7 driver tube - it's one of the reasons I am even building tube projects. I've heard what it does in the Blue Velvet preamp, AE-3, and Cary amps.
I am staying with the Walton or JEL 300B guys!
I am in the process of building a 2A3 right now and I am thinking of stealing the driver stage (just the 2nd 5687 tube) for my 2A3 design from the t-rex.
Yeah, and that T-rex is expensive too.......The Plitron OPTs will run 700 bones alone.
I have most of the parts needed for the JEL 300B too and I have a beautiful set of American 76's I am just itching to hear in this circuit.
Another Part of the T-rex I was looking at that might work well is the, I think it is called, "DC balanced cathode drive". Did you see how that works on the cathode instead of a hum pot? It will require a couple of $20 Hammond 5vct filament transformers to do but I'll bet it is worth it.
I put some self made DC modules on the filaments of the KT88 and they work great. I have not heard the amp without them but I can tell you my KT88 is dead silent. I am pretty sure I am going to implement that cathode system on the JEL. If it works well fine, if not, I have some 75R pots.....
Jeff
Yeah, and that T-rex is expensive too.......The Plitron OPTs will run 700 bones alone.
I have most of the parts needed for the JEL 300B too and I have a beautiful set of American 76's I am just itching to hear in this circuit.
Another Part of the T-rex I was looking at that might work well is the, I think it is called, "DC balanced cathode drive". Did you see how that works on the cathode instead of a hum pot? It will require a couple of $20 Hammond 5vct filament transformers to do but I'll bet it is worth it.
I put some self made DC modules on the filaments of the KT88 and they work great. I have not heard the amp without them but I can tell you my KT88 is dead silent. I am pretty sure I am going to implement that cathode system on the JEL. If it works well fine, if not, I have some 75R pots.....
Jeff
I have not built the T-rex myself because that design came up when I was on a different route. Look for information on John Broskie's Guide to Tube Circuit Analysis & Design . You can trust the designer John Broskie, I suppose he even looks like a tube.
In my view the designs of John Broskie, Allen Wright, Lynn Olson and Gary Pimm are among the best.
I have one more suggestion for a nice and simple amp: the poindexter 6V6 PP amp
300B SE needs >90dB sensitivity speakers. I listen at the moment to a PP-1C amp: Schematics
Jel 300b dx
Jaap, thanks again but I am going to stick with the JEL 300B DX for now. I may graduate to the T-rex down the road. One thing is for sure, I have never lost a dime in my amp projects, always been able to sell them for a little (if not alot) more than what I put into them so this won't be a costly decision if I choose to do something different down the road. I will just sell these later.
Ok, so I am looking at the DX power supply. It is basically like this: 47uF/10H/47uF/2-8H/47uf/33K/47uF
A couple of questions.....
First is I am waiting on Edcor to get back with me about the Angela Knock-off. Until then I am modeling it with my Edcor 375-0-375, should I have to use this trannie, I have one and can purchase a second for the other channel.
I chose to use all 50uF ASC caps instead of the 47uF electrolytics. This changes the final voltage just a tad but offsets the 5v difference in the Angela vs. Edcor (380 vs 375). So no big deal. Where I am a little stuck is the choke value in the second choke. There is not much detail about this choke, just 2-8H at 60mA. Depending on the value and DCR of this choke it really affects the modeling of the final B+ on the 76 tube (anywhere from 260v to 340v) The design calls for 320v here. I guess my final question is......does anybody know what the designer used exactly in this position.....what choke and DCR?
Thanks,
Jeff
P.S. I have sent an email asking this question to je245@myactv.net, the JEL website address (I assume the builder)
Jaap, thanks again but I am going to stick with the JEL 300B DX for now. I may graduate to the T-rex down the road. One thing is for sure, I have never lost a dime in my amp projects, always been able to sell them for a little (if not alot) more than what I put into them so this won't be a costly decision if I choose to do something different down the road. I will just sell these later.
Ok, so I am looking at the DX power supply. It is basically like this: 47uF/10H/47uF/2-8H/47uf/33K/47uF
A couple of questions.....
First is I am waiting on Edcor to get back with me about the Angela Knock-off. Until then I am modeling it with my Edcor 375-0-375, should I have to use this trannie, I have one and can purchase a second for the other channel.
I chose to use all 50uF ASC caps instead of the 47uF electrolytics. This changes the final voltage just a tad but offsets the 5v difference in the Angela vs. Edcor (380 vs 375). So no big deal. Where I am a little stuck is the choke value in the second choke. There is not much detail about this choke, just 2-8H at 60mA. Depending on the value and DCR of this choke it really affects the modeling of the final B+ on the 76 tube (anywhere from 260v to 340v) The design calls for 320v here. I guess my final question is......does anybody know what the designer used exactly in this position.....what choke and DCR?
Thanks,
Jeff
P.S. I have sent an email asking this question to je245@myactv.net, the JEL website address (I assume the builder)
Hello Jeff,
Surely you can use ASC motor run 47uF capacitors in the power supply circuit. However, it would have huge difference in the sound with the kind of HT bypass capacitors that you use. It would be fun to try various kind to find out which kind you really like or it perform the best suit your taste. Unfortunately, the very famous BlackGate WKZ capacitors are obsolete and sold out these days. They now worth about US$500 each - can you imaging that??
2-8H choke for the 6SN7 driver stage - You can use chokes with 5, 8, 10, or 15H chokes and rated 20mA would be fine.
For the DCR of chokes, it would be lowest the best. I found Lundahl's C-core choke is having very low DCR in comparison with others. I would use them in case I need to build amplifiers later on. They can also be configured as balanced choke mode to minimize the common mode noise from the mains.
Johnny
Surely you can use ASC motor run 47uF capacitors in the power supply circuit. However, it would have huge difference in the sound with the kind of HT bypass capacitors that you use. It would be fun to try various kind to find out which kind you really like or it perform the best suit your taste. Unfortunately, the very famous BlackGate WKZ capacitors are obsolete and sold out these days. They now worth about US$500 each - can you imaging that??
2-8H choke for the 6SN7 driver stage - You can use chokes with 5, 8, 10, or 15H chokes and rated 20mA would be fine.
For the DCR of chokes, it would be lowest the best. I found Lundahl's C-core choke is having very low DCR in comparison with others. I would use them in case I need to build amplifiers later on. They can also be configured as balanced choke mode to minimize the common mode noise from the mains.
Johnny
Johnny,
I think we are on the same page....I plan to use 50uF ASC in place of the 47uF electrolytics. I have had superb results with the ASC oil/film can caps in the HT filter circuit. I doubt I will eve use anything else unless somebody dies and leaves a few Black Gates in their estate for me. Until then it will have to be ASC.
I was actually thinking of subbing a pair of 10H 65mA 205 DCR Hammonds that sell for about $20 a piece at AES.
Seems to how there is a 33K resistor following it to drop the voltage I would think the DCR has little to do with this part of the circuit be it 50R or 400R.
Jeff
- Status
- Not open for further replies.