Hello. I recently had my Willsenton R800i 845 burgled from my home along with some digital equipment and some speaker transducers. I have built a Troels Gravesen TL1 which is 95db sensitive and now I have to get another power amplifier(s). I fell absolutely in love with the sound of the 845 and I believe it sounds so good because it has enough power to drive all the speakers I have given it, but it is still a SET and still sounds so sweet.
So, instead of buying another stereo integrated or anything else, I want to build my next amp. I am not sure if building an 845 amp as my first amp build would be appropriate and so I might end up building a solid state class-A or even a higher-lettered class amp just to get things started.
I wanted to ask if there are any designs of 845 monoblocks that I can work towards building? I want point to point wired and as simple as possible with no features other than power amplification. I know relatively little about electrical engineering but can read diagrams, build crossovers and cables, have my own soldering setup and am on the passive preamp-builder level in terms of components. I don't have a lot of testing gear like a good oscilloscope (I have a cheap DIY version), but I can buy more over time.
If you don't know of a design that I can use for 845 monoblocks, maybe you can point me to a simpler design that will (sortof) meet my tube needs?
I can't really spend a ton of money because I am having to replace several components from the burglary. My thoughts are that I could spend up to $1,500 per monoblock. If I do not use 845 tubes on my first build I want to keep it affordable, like $500/monoblock so that my learning doesn't start to consume my entire financial income.
The primary purpose of this amplifier is to power the TL1, a full-range 95db sensitive hornloaded loudspeaker that is already in my home. I don't need a ton of power but want at least enough to run these beasts. I don't know if 300B tubes will put out enough power, but can anyone help me get started on my journey to finding the design that I want to build?
I went from not being able to build speakers to building world-class ones (in terms of design....im not bragging about my build skills) in about 3 months so I think a similar amount of time devoted to the art of amplifier building could yield the results I seek. I have many many hours a day to devote to the task and the only impediment to forward progress is money.
I look forward to hearing from you and happy DIYing!
So, instead of buying another stereo integrated or anything else, I want to build my next amp. I am not sure if building an 845 amp as my first amp build would be appropriate and so I might end up building a solid state class-A or even a higher-lettered class amp just to get things started.
I wanted to ask if there are any designs of 845 monoblocks that I can work towards building? I want point to point wired and as simple as possible with no features other than power amplification. I know relatively little about electrical engineering but can read diagrams, build crossovers and cables, have my own soldering setup and am on the passive preamp-builder level in terms of components. I don't have a lot of testing gear like a good oscilloscope (I have a cheap DIY version), but I can buy more over time.
If you don't know of a design that I can use for 845 monoblocks, maybe you can point me to a simpler design that will (sortof) meet my tube needs?
I can't really spend a ton of money because I am having to replace several components from the burglary. My thoughts are that I could spend up to $1,500 per monoblock. If I do not use 845 tubes on my first build I want to keep it affordable, like $500/monoblock so that my learning doesn't start to consume my entire financial income.
The primary purpose of this amplifier is to power the TL1, a full-range 95db sensitive hornloaded loudspeaker that is already in my home. I don't need a ton of power but want at least enough to run these beasts. I don't know if 300B tubes will put out enough power, but can anyone help me get started on my journey to finding the design that I want to build?
I went from not being able to build speakers to building world-class ones (in terms of design....im not bragging about my build skills) in about 3 months so I think a similar amount of time devoted to the art of amplifier building could yield the results I seek. I have many many hours a day to devote to the task and the only impediment to forward progress is money.
I look forward to hearing from you and happy DIYing!
If you haven't built tube amps before I wouldn't recommend an 845 project, as they usually operate at 750-1100 volts.
A 6BQ5 or 6V6 PP amp would give about the same power at "only" 300V plate voltage and be much easier and less dangerous to build.
A 6BQ5 or 6V6 PP amp would give about the same power at "only" 300V plate voltage and be much easier and less dangerous to build.
Fuling, Thank you so much for this input! I agree with the voltage thing. Does it ever become "safer" to do the 1kv stuff, even with experience?
Can you point me to a published design for a 6BQ5 or 6v6 PP amp so that I may begin to digest it? I don't know how this works: if they are freely available, commercially purchasable, or a combination of both.
Any pointing in the right direction would be greatly appreciated!
Can you point me to a published design for a 6BQ5 or 6v6 PP amp so that I may begin to digest it? I don't know how this works: if they are freely available, commercially purchasable, or a combination of both.
Any pointing in the right direction would be greatly appreciated!
Kilovolts are always dangerous, but solid experience decreases the risk of lethal mistakes.
300 volts is also dangerous but at least it won't jump up and bite you as kilovolts can do.
Wire insulation and other parts can behave a bit funny at high voltages, but not funny in a good way.
I think TubeLab sells a PCB for a small PP amp with 9 pin tubes, I haven't built it myself but it seems well documented and should be a good first project.
300 volts is also dangerous but at least it won't jump up and bite you as kilovolts can do.
Wire insulation and other parts can behave a bit funny at high voltages, but not funny in a good way.
I think TubeLab sells a PCB for a small PP amp with 9 pin tubes, I haven't built it myself but it seems well documented and should be a good first project.
First of all, sorry to hear about the theft! What a pain. But to your question:
I built a pair of SE 845 monoblocks over twenty years ago, for a friend. He is still using them today. The circuit is quite simple, I've attached the schematic. Another friend built a pair and used them for 20 years until they got too heavy for him to deal with and he sold them.
That said, I'll never build an 845 amp again. The voltages are too high, the components difficult to obtain, and the weight is too much. Willsenton is able to make them affordable and reasonably portable because they can source OEM components and crunch a lot of stuff onto PCBs. But if I HAD to do it again, Hammond makes just about everything you need, including output, plate, filament transformers and chokes. It would probably be a pretty decent-sounding amp. I used Magnequest output transformers but those are no longer available. Today I use homebrew copies of 1950 Williamson amplifiers, good for 20 wpc, and to my ears they offer everything an SE 845 offers and more, in terms of bandwidth, control, affordable tubes and relative ease of construction. But I understand the allure of the 845--it's quite a sound.
However, it's a very big risk.
Attachments
Same advice as others. kVs are involved. Experience working with such beasts needs to be built up. I've built many EL34, 300B and other tube amp kits. I thought about tackling an 845 or 211 design as that amout of SET power is attractive but sanity and reason would prevail. Really need a good test bench with a few years of experience working with high voltages (>1kV).
Have you looked at any of the Nelson Pass 1st Watt clone boards? Lots of support here and lots of parts (including PCBs and parts kits) available via the diyAudio store. I've built the F4 (sonically neutral as I've ever heard) and an F6 (warm but not tubby). They've converted me from using power tubes for output sections. MOSFETs are much easier to work with.
https://www.diyaudio.com/community/threads/the-diyaudio-build-guides.260319/
https://diyaudiostore.com/
Have you looked at any of the Nelson Pass 1st Watt clone boards? Lots of support here and lots of parts (including PCBs and parts kits) available via the diyAudio store. I've built the F4 (sonically neutral as I've ever heard) and an F6 (warm but not tubby). They've converted me from using power tubes for output sections. MOSFETs are much easier to work with.
https://www.diyaudio.com/community/threads/the-diyaudio-build-guides.260319/
https://diyaudiostore.com/
With 95db speakers, 2A3 SET may be a good starting point. Relatively simply to build with nice sounding.
No need for mono blocks/having to pay for main power transformers, chokes and caps in PSU twice - but definitely having PSU in a separate box (that’s better than mono), and using dedicated filament transformers for 2A3s. With a budget of up to $3000, you can use interstage transformers too.
No need for mono blocks/having to pay for main power transformers, chokes and caps in PSU twice - but definitely having PSU in a separate box (that’s better than mono), and using dedicated filament transformers for 2A3s. With a budget of up to $3000, you can use interstage transformers too.
6sX7, your advice is well taken. I don't know how I feel about introducing any solid state though. As I go through this if I find that is very cost effective I'll probably go that way just for that reason, but I feel like I have heard the "true" sound now with 845 SET and I want to keep it as "old-school" as possible i.e. point-to-point wiring, tube output, tube rectification....remember I'm a newbie but somehow I "feel" like this will sound the best. I am going to check out the build guides you put up and put considerable thought into them.
Fei, Thank you for your recommendation. I like that you referenced my speakers. That makes me feel like your recommendation might be right on. Regarding monoblocks, do you not like them simply because they cost more or are you saying that a stereo amp with a separate power box will sound better than monos? From what I've heard monos sound that much better and I want to experiment with them. What do you think about a 3-box solution?
Thank you again guys and gals, I know this is going to be a long journey and I'm glad I can walk it with the likes of y'all.
Fei, Thank you for your recommendation. I like that you referenced my speakers. That makes me feel like your recommendation might be right on. Regarding monoblocks, do you not like them simply because they cost more or are you saying that a stereo amp with a separate power box will sound better than monos? From what I've heard monos sound that much better and I want to experiment with them. What do you think about a 3-box solution?
Thank you again guys and gals, I know this is going to be a long journey and I'm glad I can walk it with the likes of y'all.
I've always wanted to ask experienced DIYers, do binding posts, wires, and fuses make a considerable amount of difference to sound quality vs components and layout? I've tried Synergystic Research fuses and they did increase the quality, at least to me. I have furutech binding posts on my speakers furutech xlr because they are very easy to work with and feel well built. Wondering what people think about spending another $500 for binding posts on an amp vs $50 and spending $400 or so on fuses instead of maybe $20...
I think I've narrowed it down already.
Nelson Pass Aleph J: having 25WPC will match the 845 on power exactly. Being pure class A this is attractive to me. Easy to build. Good documentation. Safe.
2A3 SET - Perhaps better sound??? Please everyone chime in on this. 3.5wpc seems uber-weak to me. Using 89dB speakers I could pound the 845 SET 23wpc into clipping without much problem...Will 6db of extra sensitivity take me from needing 23 to needing 3.5??
Thoughts from the wise?
Nelson Pass Aleph J: having 25WPC will match the 845 on power exactly. Being pure class A this is attractive to me. Easy to build. Good documentation. Safe.
2A3 SET - Perhaps better sound??? Please everyone chime in on this. 3.5wpc seems uber-weak to me. Using 89dB speakers I could pound the 845 SET 23wpc into clipping without much problem...Will 6db of extra sensitivity take me from needing 23 to needing 3.5??
Thoughts from the wise?
I don't have the patience for most of that stuff and would rather spend the money where it really makes a difference--quality transformers and tubes. Convenience is good, sturdiness is good. Exotic materials might make a difference, but they might also make the amp sound worse. ;-) I find this is especially true of boutique power cords. Coupling caps are important but again I favor "well-made" over exotic. Exotic caps can also break down (ask me about the $250 V-Cap that shorted and sent 150VDC to the input of one amp). Cornell-Dubilier 942C caps are excellent, IMO. Mundorf Supreme is about as fancy as I'll get. I prefer things that don't distort the signal.
My preferred binding posts are standard vintage bakelite and brass (not the newer ones, they snap off).
Hope that helps! ;-)
best of both worlds. 2A3 amp to drive a 1st Watt F4 clone. bam!
https://www.firstwatt.com/pdf/prod_f4_man.pdf
https://www.firstwatt.com/pdf/prod_f4_man.pdf
A First Watt F4 is an excellent idea. You may not need more than the 2a3 as driver. If you do I'd recommend a good step-up transformer on the input rather than a 9 pin valve. Keep it all DHT. I use a Hammond 1140-LN-C as input transformer. Good value and studio quality. Or just a 10Y input would probably do it - that would be marvellous.
I've thought about something similar, an F4 (or some other mosfet power follower) driven by a nice triode and an interstage transformer. No need for a complete tube amp with a dummy load on the output just to provide the voltage gain.
I found an input transformer better than an interstage - cap coupling the DHT with Russian FT-2 teflon caps. I suppose it depends on the interstage, though.
Since 845 voltage can be deadly i would recommend a VFET Power amp. Maybe build a SE with a Tokin THF-51S. Very popular in the Pass forum but some are only buffer like the F4 so a preamp with a high gain would be needed.
Andy: My first attempt to build an amp like this would probably be with a medium Rp triode and a 2:1 (or so) stepdown IT. The F4 has Jfet buffers which probably are a game changer but when I experimented with tubes and mosfet followers two decades ago the results where quite awful. My conclusion then was that small-signal triodes where unable to drive power mosfets properly, resulting in a shrill and unpleasant sound. Granted, this was long ago when I was new to tubes (and to mosfets...).
A low Rp triode can probably drive some mosfets just fine without stepdown IT, with or without input transformer.
It would be interesting to try 4P1L running at 20 mA or so into an IT with some stepdown driving a choke loaded SE mosfet follower. A bit off topic, but food for thought.
A low Rp triode can probably drive some mosfets just fine without stepdown IT, with or without input transformer.
It would be interesting to try 4P1L running at 20 mA or so into an IT with some stepdown driving a choke loaded SE mosfet follower. A bit off topic, but food for thought.
I thank you all for the continued support and input. FYI I will be using a passive preamplifier (stepped ladder attenuator) with XLR output. Source is digital 4V balanced // 2V unbalanced (read HOT). As far as I know I can use XLR jacks on the input of the amp and just send the negative to ground (?)
As I go through all this, understanding 20% of it and researching 70% of it, I feel like a multibox solution might be beyond what I can do for a first build. I wonder if a Bottlehead Kaiju 300B (8wpc/16wpc mono mode) would be the best bet? The wattage seems sufficient for 95db speakers and I would have pure DHT SET sound. It also allows for an upgrade path.
A few questions:
1. Do people think the 300B sounds "better" than the 845? What about compared to smaller tubes like 2A3?
2. Any comments on the bottlehead stuff, how easy it is for beginners and how much I can learn by building something like the Kaiju? How about their prices vs raw component prices?
Thanks again!
As I go through all this, understanding 20% of it and researching 70% of it, I feel like a multibox solution might be beyond what I can do for a first build. I wonder if a Bottlehead Kaiju 300B (8wpc/16wpc mono mode) would be the best bet? The wattage seems sufficient for 95db speakers and I would have pure DHT SET sound. It also allows for an upgrade path.
A few questions:
1. Do people think the 300B sounds "better" than the 845? What about compared to smaller tubes like 2A3?
2. Any comments on the bottlehead stuff, how easy it is for beginners and how much I can learn by building something like the Kaiju? How about their prices vs raw component prices?
Thanks again!
First of all, I think the fact that your speakers are 95db sensitive means that there is a chance 2A3 may work out. It needs to be tested, but I won’t jump to a conclusion that 845 is the only solution.
As to putting the PSU in a separate box, I believe that is a better sounding solution with the least interference from PSU to the amplification part. That’s what I always do myself. A caveat is that I use a separate LC before each tube/ after DC is sent to the amplifier box - so there is little interference between the two channels.
As to 2-box vs 3-box, it is primarily a matter of space rather than anything else. I’ve done both. I use lots of LCs in my amps and interstage transformers. 3-box means each box is manageable in weight and has less chance to break my back 🙂 But you will need shelf space for 3 boxes.