Hi Folks,
I realise that I may be opening a can of worms here but...
I am looking for ideas for my next project. I have completed both a KT88 and EL34 PP amp. I am extremely pleased with both but I am itchy for a new project.
I am looking to build something really special and I understand that this is largely in the eye/ear of the beholder but I need some input from the members of this forum.
OK, lets pretend that money is no option (it is but lets pretend). My only requirements are as follows -
1. Output tubes different from above (ie no EL34 or KT88)
2. At least 8-10w (or at least something suitable for speakers of 90db sensitivity)
3. No kits
4. Voltages < 600v
I am keen for as little or much advice as you can give especially with regards to specific schematics - I can see myself heading down the 300b road but maybe there is something better out there! I am not looking for a quick or easy project - this one needs to be a killer amp (well, not literally hence the voltage restriction but you know what I mean)
Once again I appreciate the huge scope of the question; perhaps I could rephrase it - with regards to the above criterion, what would you build?
Cheers,
Rob
PS Please find attached a picture of my KT88 at night
I realise that I may be opening a can of worms here but...
I am looking for ideas for my next project. I have completed both a KT88 and EL34 PP amp. I am extremely pleased with both but I am itchy for a new project.
I am looking to build something really special and I understand that this is largely in the eye/ear of the beholder but I need some input from the members of this forum.
OK, lets pretend that money is no option (it is but lets pretend). My only requirements are as follows -
1. Output tubes different from above (ie no EL34 or KT88)
2. At least 8-10w (or at least something suitable for speakers of 90db sensitivity)
3. No kits
4. Voltages < 600v
I am keen for as little or much advice as you can give especially with regards to specific schematics - I can see myself heading down the 300b road but maybe there is something better out there! I am not looking for a quick or easy project - this one needs to be a killer amp (well, not literally hence the voltage restriction but you know what I mean)
Once again I appreciate the huge scope of the question; perhaps I could rephrase it - with regards to the above criterion, what would you build?
Cheers,
Rob
PS Please find attached a picture of my KT88 at night
Attachments
Paul Joppa's 102 dB. rule indicates that 15+ WPC are appropriate for your speakers. A 7591 based "El Cheapo Grande" satisfies both PJ's and your criteria. 
An ECG produces approx. 30 WPC in UL mode and 15 WPC in triode mode.
I'll try to EMail the lower powered "El Cheapo" schematic to you. Circuitry that drives "12" W. multi-grid power O/P tubes also drives the 7591. "El Cheapo Grande" uses the same 12AT7 based splitter/driver that EC uses.
An ECG produces approx. 30 WPC in UL mode and 15 WPC in triode mode.I'll try to EMail the lower powered "El Cheapo" schematic to you. Circuitry that drives "12" W. multi-grid power O/P tubes also drives the 7591.
"El Cheapo Grande" uses the same 12AT7 based splitter/driver that EC uses.
Go with 845 single ended, using 5687 cap. couple to KT88, then use interstage to drive 845, under this config., you would not regret.
Don't be afraid of the high tension for 845, there is only 2 wiring points must take high attention - the long cable from the cap filter to the output HT and the cable from the "P" pin of the output to the 845 socket.
Carefully to treat this in safe, then nothing should be afraid of !!!
Of course, the high voltage section should be arranged as closer as possible and in a result the wiring can be made as short as possible within the area of the high voltage section, this will avoid the chance of electric shock !!!
Believe me, follow this wiring arrangement your machine should be running for years in safe !!! I am dare to claim that it sounds excellent to you and better than 300B, no matter the punching or textures.
As you mentioned, money for nothing, the output and the interstage you have to use well known brand or reliable one, such as Tamura, Audio Note, Lundhal or its like, because any iron participates in a tube amp. plays a very very important role and the rule of "money is no option" must be obeyed for the quality of iron !!!
I do not quite agree that it should use excellent schematic design and the irons only need to play a proper role is ok. Tube amp is not a rocket science, complicated excellent schematic will not make things easier and understandable, it just make things complicated further and discourage a diyer, that's what I think.
If you don't like the tenant - KT88 living in your house, try KT66 or even 300B as the driver tube. But I don't think 300B is a good choice because it is a waste !!!
Also, it will give you about 20W something for the output power and it is not a big number in terms of output rating. Because you just use one to two watts to drive your sensitive loudspeakers in general listening range and under this range, the 845 can give you a very little distorted sound. Absolutely better than 300B if under same listening level, at least more un-distorted and realistic low bass punch can be reproduced.
Try it and you will find it is worth to try it and own it.
Don't be afraid of the high tension for 845, there is only 2 wiring points must take high attention - the long cable from the cap filter to the output HT and the cable from the "P" pin of the output to the 845 socket.
Carefully to treat this in safe, then nothing should be afraid of !!!
Of course, the high voltage section should be arranged as closer as possible and in a result the wiring can be made as short as possible within the area of the high voltage section, this will avoid the chance of electric shock !!!
Believe me, follow this wiring arrangement your machine should be running for years in safe !!! I am dare to claim that it sounds excellent to you and better than 300B, no matter the punching or textures.
As you mentioned, money for nothing, the output and the interstage you have to use well known brand or reliable one, such as Tamura, Audio Note, Lundhal or its like, because any iron participates in a tube amp. plays a very very important role and the rule of "money is no option" must be obeyed for the quality of iron !!!
I do not quite agree that it should use excellent schematic design and the irons only need to play a proper role is ok. Tube amp is not a rocket science, complicated excellent schematic will not make things easier and understandable, it just make things complicated further and discourage a diyer, that's what I think.
If you don't like the tenant - KT88 living in your house, try KT66 or even 300B as the driver tube. But I don't think 300B is a good choice because it is a waste !!!
Also, it will give you about 20W something for the output power and it is not a big number in terms of output rating. Because you just use one to two watts to drive your sensitive loudspeakers in general listening range and under this range, the 845 can give you a very little distorted sound. Absolutely better than 300B if under same listening level, at least more un-distorted and realistic low bass punch can be reproduced.
Try it and you will find it is worth to try it and own it.
What is your budget? The 300B's themselves can be a bit pricey but other than that the costs aren't to bad. If you need the increased power you could do a Parallel SE or Push/Pull 300B. Stick something fun in front for a driver and drive the back end with an interstage transformers.
http://www.audiodesignguide.com/my/sep_mk2.gif
Example (^); most of your cost is going to be in iron and tubes....like all things. The 417A/5842 from Raytheon can be found for $20-$30 USD, a matched pair of 300B's, the same ones I am looking at for my build, are $175USD for EH Gold Grids. The interstage would be costly though, you want to use a high quality unit here, no skimping. As for the B+, it is under 600v at 380v. Most simple 300B designs that I have come across use 350v to 425v or so, only a few use up to 700v, Electra-Print DRD 300B SE for example. The JE Labs 300B SE would be a simple and cheap implementation to get a bit of 300B taste. That is the design I considered but since starting a thread here on my build I have decided otherwise.
Another option that could be done on the cheap. Buy some 12HG7's, they are great drivers when pentode wired or triode wired, and they can be found cheaply. Couple it to a 300B and you would have a great little amp. You could simple wire it up as a triode or you could use the pentode option and make a 91A type amplifier. You could even do something fun with it like choke load, DRD, or interstage drive. For the cost of a single WE 417, or even a Raytheon, you could get a small handful of 12HG7's.
Why not take something like a power pentode like the KT88 (sorry) and make a SE amp. To try something different you could use 807's (beware of plate cap). These can still be found fairly cheaply even as NOS. I have about 16 807 that I am planning projects for, all NOS, I love 807's. There is just something about the seductive coke bottle ST shape with a cap on top, and they glow heavenly. Although they don't glow quite as heavenly as a GM70. Parallel 6L6's could do the trick, or do a 6C33C SE. You could take a KT88, 6L6, 807, etc... and set it up for triode operation with a switch so you can switch it back to UL operation if you need to or want to. You can get a quasi taste of SET sound without paying for the classic SET tubes like the 300B, 50, and 2A3.
http://diyaudioprojects.com/Tubes/KT88/index.htm
The above is just an option to consider. You could look at the 813 (directly heated pentode) also, it likes 900v+ but you can get by right at your 600v maximum. With a full 900v or more though you can get 20watts or more in triode mode and almost 50watts in UL. Beware though, this beast has a plate cap, not good for kids, pets, and wandering fingers
.
Cheers
James
http://www.audiodesignguide.com/my/sep_mk2.gif
Example (^); most of your cost is going to be in iron and tubes....like all things. The 417A/5842 from Raytheon can be found for $20-$30 USD, a matched pair of 300B's, the same ones I am looking at for my build, are $175USD for EH Gold Grids. The interstage would be costly though, you want to use a high quality unit here, no skimping. As for the B+, it is under 600v at 380v. Most simple 300B designs that I have come across use 350v to 425v or so, only a few use up to 700v, Electra-Print DRD 300B SE for example. The JE Labs 300B SE would be a simple and cheap implementation to get a bit of 300B taste. That is the design I considered but since starting a thread here on my build I have decided otherwise.
Another option that could be done on the cheap. Buy some 12HG7's, they are great drivers when pentode wired or triode wired, and they can be found cheaply. Couple it to a 300B and you would have a great little amp. You could simple wire it up as a triode or you could use the pentode option and make a 91A type amplifier. You could even do something fun with it like choke load, DRD, or interstage drive. For the cost of a single WE 417, or even a Raytheon, you could get a small handful of 12HG7's.
Why not take something like a power pentode like the KT88 (sorry) and make a SE amp. To try something different you could use 807's (beware of plate cap). These can still be found fairly cheaply even as NOS. I have about 16 807 that I am planning projects for, all NOS, I love 807's. There is just something about the seductive coke bottle ST shape with a cap on top, and they glow heavenly. Although they don't glow quite as heavenly as a GM70. Parallel 6L6's could do the trick, or do a 6C33C SE. You could take a KT88, 6L6, 807, etc... and set it up for triode operation with a switch so you can switch it back to UL operation if you need to or want to. You can get a quasi taste of SET sound without paying for the classic SET tubes like the 300B, 50, and 2A3.
http://diyaudioprojects.com/Tubes/KT88/index.htm
The above is just an option to consider. You could look at the 813 (directly heated pentode) also, it likes 900v+ but you can get by right at your 600v maximum. With a full 900v or more though you can get 20watts or more in triode mode and almost 50watts in UL. Beware though, this beast has a plate cap, not good for kids, pets, and wandering fingers
. Cheers
James
Here's a special one. It meets all your stated criteria, and you won't find any of these on your block. A lot going on under the hood - would be a real learning experience: http://www.intactaudio.com/forum/viewtopic.php?t=549
Sheldon
Sheldon
How about parallel (or accordian) SE DHT using some of the less glamorous bulbs. What is that one that is a 6V heater 2A3? 6A5 I think. Add transformer coupling and you have something quite different that what you have done.
Or do something other than a power amp like a tuner, phono preamp, mixing board etc. Just thinking outside the box.
mike
Or do something other than a power amp like a tuner, phono preamp, mixing board etc. Just thinking outside the box.
mike
JPeitzman said:
I enjoy the way he thinks. I've built a couple of projects based on his designs and have been pleased with the outcome. If I were looking for 45 of sweet pp power, I'd build this one. Relatively efficient for that power level too. I don't know much about building the controller, but everyone of us probably has a friend that does.
Sheldon
Hi all,
Thanks for the replies so far – some great ideas here.
I can see that I need to clarify a couple of things. To answer James, my budget is about $2500 Aus (which will be about 2600 USD in a couple of months! - apologies to my American friends) – this is for components and excludes the chassis. I believe that I can build a decent amplifier for this sort of money and I am definitely interested in opinions concerning quality transformers and caps.
Eli, you are correct, I probably do need the 15w/channel, so I will have to upgrade my original specks. I would be very interested to see the schematic of the El Cheapo Grande.
Ty, I agree, I think that I am looking for SE, triode.
Tim, I enjoyed your post immensely and admire your impassioned argument for the 845’s. I do love the idea of these tubes and it is a very tempting option but I am just a little too wary at this point in time to dabble with ultra high voltage. Call me soft if you like!
Sheldon, what can I say? That amp is amazing. There is little doubt that I would be the only owner on the block. I did have in mind something a little more ‘classic’ but I will definitely have a closer look at this one over the next day or two.
Mike, part of my interest in theses amplifiers is the classic old world beauty of the glowing tubes, so along with a great sound I am also keen to build with glamorous bottles this time. The more glamour the better (but not 1000v glamour).
So far I like the look of James’s MKII. This is the sort of thing that I was thinking of, simple yet elegant and less parts so I can allocate resources to quality components. Having said this, I am a long way from making up my mind, so keep the ideas coming. I like the idea of a bit of an exotic front driver as well.
One final query, I have never seen a ‘live’ 300b. Do they have a pleasing glow; many of the photos that I have seen make it look a little less than impressive. This is a small point but I have to get the ‘art’ side of it right as well.
In summary, I am now firming up some more criteria (but not set in concrete) –
1. Upgrade power requirements to 15w/channel
2. Triode, single ended
3.‘Glamorous' tubes!
Once again, thanks for the input so far.
Rob
Thanks for the replies so far – some great ideas here.
I can see that I need to clarify a couple of things. To answer James, my budget is about $2500 Aus (which will be about 2600 USD in a couple of months! - apologies to my American friends) – this is for components and excludes the chassis. I believe that I can build a decent amplifier for this sort of money and I am definitely interested in opinions concerning quality transformers and caps.
Eli, you are correct, I probably do need the 15w/channel, so I will have to upgrade my original specks. I would be very interested to see the schematic of the El Cheapo Grande.
Ty, I agree, I think that I am looking for SE, triode.
Tim, I enjoyed your post immensely and admire your impassioned argument for the 845’s. I do love the idea of these tubes and it is a very tempting option but I am just a little too wary at this point in time to dabble with ultra high voltage. Call me soft if you like!
Sheldon, what can I say? That amp is amazing. There is little doubt that I would be the only owner on the block. I did have in mind something a little more ‘classic’ but I will definitely have a closer look at this one over the next day or two.
Mike, part of my interest in theses amplifiers is the classic old world beauty of the glowing tubes, so along with a great sound I am also keen to build with glamorous bottles this time. The more glamour the better (but not 1000v glamour).
So far I like the look of James’s MKII. This is the sort of thing that I was thinking of, simple yet elegant and less parts so I can allocate resources to quality components. Having said this, I am a long way from making up my mind, so keep the ideas coming. I like the idea of a bit of an exotic front driver as well.
One final query, I have never seen a ‘live’ 300b. Do they have a pleasing glow; many of the photos that I have seen make it look a little less than impressive. This is a small point but I have to get the ‘art’ side of it right as well.
In summary, I am now firming up some more criteria (but not set in concrete) –
1. Upgrade power requirements to 15w/channel
2. Triode, single ended
3.‘Glamorous' tubes!
Once again, thanks for the input so far.
Rob
Well with $2600 to spend and a desire for glamor PSE 300s is not a bad direction to head and if I am not mistaken would get you very close to the 15W you seek as I have seen a lot of claims of about 8W for single 300s.
With that budget you can afford some interstage iron and/or experiment with some off the beaten path tubes. Maybe try taming the 6S45 which has high gain and low rp. See if you can come up with a clever but simple way to deal with Cmiller. Or maybe combine the boutique output tubes with some vertical deflection tubes from the other side of the tracks.
The possibilities are endless...
mike
With that budget you can afford some interstage iron and/or experiment with some off the beaten path tubes. Maybe try taming the 6S45 which has high gain and low rp. See if you can come up with a clever but simple way to deal with Cmiller. Or maybe combine the boutique output tubes with some vertical deflection tubes from the other side of the tracks.
The possibilities are endless...
mike
mashaffer said:
Mr Miller can be hammered into submission with a mosfet follower. Even allows excursions into A2 territory, which makes it pretty easy to get to 15W from a variety of tubes. Check out our very own Tubelab's site: http://www.tubelab.com/
George is another one of those guys with lots of cool and practical ideas.
Sheldon
Rob11966 said:
You gonna design this new project, or use a preexisting design? I like taking the road less traveled myself.
You could:
Do an OTL.
Class AB2 PP 45s
PP 6CK4s
Something with those RF triode finals
My next project is an 845 amp, since 1000+ Vdc doesn't put me off.
Hi Miles,
The Australian version of 'a road less traveled' is an expression 'off the beaten track' which means essentially the same thing.
In general I enjoy the 'off the beaten track' approach and use it often. However, to successfully navigate the remote dirt roads one needs a great big 4 wheel drive with long range fuel tanks, GPS and a satellite phone. Unfortunately with respect to electronics and hollow state in particular, I own a second hand Hyundi with half a tank of gas!!
My projects so far (I feel) have been very successful and satisfying and I have picked up an awful lot but I am still on the steep part of the learning curve. In short, I will require a pre-existing design which I will tweak around the edges. I accept that it may be boring driving on the highway but I have only been driving a little while.
Hi Lowrider, I do like the look of the Ciuffoli amp which is the same one presented by James. The PSE side of it concerns me a bit as I have read that it represents some of the worst qualities of the pure SE and PP amps - any ideas? This opinion may be garbage or may be one of the compromises that I have to make to obtain the power output that I need. Also, any opinion on the 5842 driver - can I do better?
Finally, 300b tube glow......is it glamorous enough!?
Cheers and thanks again for the help so far.
Rob
The Australian version of 'a road less traveled' is an expression 'off the beaten track' which means essentially the same thing.
In general I enjoy the 'off the beaten track' approach and use it often. However, to successfully navigate the remote dirt roads one needs a great big 4 wheel drive with long range fuel tanks, GPS and a satellite phone. Unfortunately with respect to electronics and hollow state in particular, I own a second hand Hyundi with half a tank of gas!!
My projects so far (I feel) have been very successful and satisfying and I have picked up an awful lot but I am still on the steep part of the learning curve. In short, I will require a pre-existing design which I will tweak around the edges. I accept that it may be boring driving on the highway but I have only been driving a little while.
Hi Lowrider, I do like the look of the Ciuffoli amp which is the same one presented by James. The PSE side of it concerns me a bit as I have read that it represents some of the worst qualities of the pure SE and PP amps - any ideas? This opinion may be garbage or may be one of the compromises that I have to make to obtain the power output that I need. Also, any opinion on the 5842 driver - can I do better?
Finally, 300b tube glow......is it glamorous enough!?
Cheers and thanks again for the help so far.
Rob
Attention Eti
Sorry Eti,
Did you manage to get your hands on the schematic for the El Cheapo Grande?
Cheers,
Rob
If you have trouble with my email through the forum, it is -
xrobx.turnerx@ozemailx.comx.au (just remove all of the x's)
Sorry Eti,
Did you manage to get your hands on the schematic for the El Cheapo Grande?
Cheers,
Rob
If you have trouble with my email through the forum, it is -
xrobx.turnerx@ozemailx.comx.au (just remove all of the x's)
Rob11966 said:
Well, it is SE, so whatever "worst qualities SE amps have", it would have; except that it would have lower Zout than a single tube 300b amp (usually considered a good thing, especially for bass reproduction in a full range application). Only downside I can see (but haven't heard) is that some claim that paralleled tubes affect clarity, others like them just fine. Rob11966 said:
Better in what way? http://www.mif.pg.gda.pl/homepages/frank/sheets/138/5/5842.pdf
Rob11966 said:
Well, it's got a bunch of tubes? Keep the glamour and sound separate. Build a nice reflective top plate, and brass or chrome plate your transformer covers, so it's all sparkly in the dark. Use a gas reg tube for each leg of the bias supply to tart it up a bit more (and maybe improve the supply a little).
If you want to keep the voltages lower and still get you 15W or so, use a single tube, add a mosfet follower and set it up to go into A2.
Sheldon
Thanks Sheldon,
The loss of clarity with the parallel circuit was what I was referring to - I agree this was phrased poorly. I am not sure how much of a real issue this is?
With respect to the reflective tops, my last amp was gold plated and the one before bright nickel. This works well with the KT88's and the EL34 - my point with the 300b tubes is that I have never seen them in real life and and was specifically wondering whether the heater was largely visible (with a decent glow) or hidden within the plates. With this particular project, I am considering coloured glass tops for something different. Clearly the sound is the most important aspect but the visual side of the project is important to me as well as you might have noticed from my previous amps. My point is that with this project, I want it to all come together, sound and looks.
I have not seen the gas rectifier tubes but I will look into them. I will have to think about how to work them into this particular circuit, a task which may seem simple and intuitive to some but one that poses challenges for me as I am more of a 'recipe' builder at this stage.
Rob
The loss of clarity with the parallel circuit was what I was referring to - I agree this was phrased poorly. I am not sure how much of a real issue this is?
With respect to the reflective tops, my last amp was gold plated and the one before bright nickel. This works well with the KT88's and the EL34 - my point with the 300b tubes is that I have never seen them in real life and and was specifically wondering whether the heater was largely visible (with a decent glow) or hidden within the plates. With this particular project, I am considering coloured glass tops for something different. Clearly the sound is the most important aspect but the visual side of the project is important to me as well as you might have noticed from my previous amps. My point is that with this project, I want it to all come together, sound and looks.
I have not seen the gas rectifier tubes but I will look into them. I will have to think about how to work them into this particular circuit, a task which may seem simple and intuitive to some but one that poses challenges for me as I am more of a 'recipe' builder at this stage.
Rob
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