Lots of reading on forums resulting in scattered thoughts and led to me seek out some advice. I'm not afraid of the soldering iron, have worked with big caps before, and know how to use a multi-meter, but this is the first time I've considered building a complete amp. I’m assuming I first need to pick a schematic, then determine the necessary components, and finally the physical layout and design.
For the schematic, I'd like to DIY something that sounds lush (like many 300B SE amps) but with the power to drive basically any speaker I might decide to use today or in the future. I don't have high-efficiency speakers now and don't anticipate buying/building anything purely based on efficiency either. Am I correct that a push-pull design of some sort would best fit these criteria?
Assuming PP is the way to go, there seem to be a number of such DIY designs out there. A few seem the most popular. I see a lot of threads about Dynaco clones (ST-7, ST-125 , MkIII, VTA M-125) and also a few about HK Citations, and perhaps the Oddblock KT120. Based on the little I know, and the fact I’ve been wanting a set of Monoblocks for as long as I remember, the MkIII, the M-125, or something similar could definitely be top contenders.
Obviously the MkIII and M-125 have the advantage of being offered as kits and are well proven. But there are some things that hold me back. I don’t like the way these chassis look (yes, it doesn't affect the sound), but perhaps all I need to do is buy only the PCB’s or even wiring point-to-point on a chassis of my own. The quality of the transformers is widely accepted to be the deal breaker anyways, right? Speaking of which, I’m not interested in expensive tubes or parts like Lundahl or Plitron (at least for now). The likes of Edcor and AnTek are in my range, and it might even be a toss-up based on price versus the transformers offered with the kits anyways. Also, I’ve read these designs perhaps aren’t as good as a more modern design. Unfortunately, I have no idea the difference in sonics or how much more difficult it would be to build a modern design.
Would love any comments, and thanks in advance!
For the schematic, I'd like to DIY something that sounds lush (like many 300B SE amps) but with the power to drive basically any speaker I might decide to use today or in the future. I don't have high-efficiency speakers now and don't anticipate buying/building anything purely based on efficiency either. Am I correct that a push-pull design of some sort would best fit these criteria?
Assuming PP is the way to go, there seem to be a number of such DIY designs out there. A few seem the most popular. I see a lot of threads about Dynaco clones (ST-7, ST-125 , MkIII, VTA M-125) and also a few about HK Citations, and perhaps the Oddblock KT120. Based on the little I know, and the fact I’ve been wanting a set of Monoblocks for as long as I remember, the MkIII, the M-125, or something similar could definitely be top contenders.
Obviously the MkIII and M-125 have the advantage of being offered as kits and are well proven. But there are some things that hold me back. I don’t like the way these chassis look (yes, it doesn't affect the sound), but perhaps all I need to do is buy only the PCB’s or even wiring point-to-point on a chassis of my own. The quality of the transformers is widely accepted to be the deal breaker anyways, right? Speaking of which, I’m not interested in expensive tubes or parts like Lundahl or Plitron (at least for now). The likes of Edcor and AnTek are in my range, and it might even be a toss-up based on price versus the transformers offered with the kits anyways. Also, I’ve read these designs perhaps aren’t as good as a more modern design. Unfortunately, I have no idea the difference in sonics or how much more difficult it would be to build a modern design.
Would love any comments, and thanks in advance!
You might want to check out what George is up to on the Tubelab forum:
Tubelab Universal Driver Board, 2015 version
Tubelab Universal Driver Board, 2015 version
I'm currently building one of Pete Millett's amplifiers. His "Engineers Amplifier" is a push-pull. I've already built three others (one solid state, one hybrid, and one SE tube) by him and I can vouch for the quality of the sound. There is lots of documentation on this forum about the Engineers Amp, The same George mentioned above took the engineers amp to insane levels without straying too far from Pete's original design. This same amp has also been re-designed by Pete in a monoblock version. You should visit Pete's web-site (Pete Millett's DIY Audio pages ) and check them out. Pete sells his PCB's on ebay and Edcor has several of his transformers on their site. Pete also list the BOM for his projects to make it easier for the diy crowd.
Not getting the idea that the tubelab universal board will be my cup of tea. I haven’t yet read through the entire thread but I’m pretty sure I want to stick with something fairly well proven vs a new concept.
Can anyone comment on the Sonics of the 50W monoblock Engineer’s Amp compared to say the MkIII?
Other than being assembled in a large single package (instead of mono blocks), I find this custom built unit very interesting: YouTube
Can anyone comment on the Sonics of the 50W monoblock Engineer’s Amp compared to say the MkIII?
Other than being assembled in a large single package (instead of mono blocks), I find this custom built unit very interesting: YouTube
Pitchinwedge,
The "lushness" you describe in SE 300Bs is due to the considerable amount of 2nd harmonic distortion the type produces. Choose between HIFI and an effects (euphony) machine.
There are several threads in the archives about PP KT88 builds that employ Mullard style topology. Mullard style topology is both a solid performer and "idiot resistant" against some builder errors. That's the "route" I suggest you take.
There are some speakers that should never be mated to tube amps. A glaring example is the big Thiel. While that item is nominally 4 Ω, it exhibits dips down to 1 Ω or a bit less and those dips occur in the critical bass region.
The "lushness" you describe in SE 300Bs is due to the considerable amount of 2nd harmonic distortion the type produces. Choose between HIFI and an effects (euphony) machine.
There are several threads in the archives about PP KT88 builds that employ Mullard style topology. Mullard style topology is both a solid performer and "idiot resistant" against some builder errors. That's the "route" I suggest you take.
There are some speakers that should never be mated to tube amps. A glaring example is the big Thiel. While that item is nominally 4 Ω, it exhibits dips down to 1 Ω or a bit less and those dips occur in the critical bass region.
I helped a buddy put one together (ok, I built it for him really) and can say it is a fantastic amplifier.
It is a very transparent amplifier that faithfully reproduces whatever you feed it, much like a good solid state amp will, and has practically no "coloration" of its own, as a good push pull design should... Highly recommended. It is not a SE amp, and will not sound like a big fat 2A3 or 300B will, as it is much lower distortion.
You'll end up with an Electronics Lab experimenter's mess, unfinished, if you do. Those are scattered across these forums like spring dandelions. Go down to the hardware store and buy a 12x12 steel plate and get out your drill to test your fab skills. Cheap lesson that could save you a lot of future frustration and may bring your ambitions back down to earth.
I built a PP amp using two tubelab simple se boards. You'll need a balanced source though.
I built with 6v6 tubes, but could easily be built with kt88 if you use the correct transformer.
Been running for 8 years, often every day. Sounds amazing.
Dual Simple SE's in Push Pull w Differential Input
Would work perfect as monoblocks- one stereo tubelab board in each block. Tons of support in that forum too.
I built with 6v6 tubes, but could easily be built with kt88 if you use the correct transformer.
Been running for 8 years, often every day. Sounds amazing.
Dual Simple SE's in Push Pull w Differential Input
Would work perfect as monoblocks- one stereo tubelab board in each block. Tons of support in that forum too.
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Thanks everyone for your comments. They are very helpful for sorting out my priorities.
I'm trying to keep the goals from being overly ambitious, and making sure my fabrication skills are adequate is certainly a valid point. A kit chassis wouldn't really be a deal-breaker. It's just a preference.
Sonics, however, are a different matter. I accept my first build will require compromises, perhaps many, so I want to make sure I do enough homework to be aware of what to realistically expect. No sense in building a race car for the track (ie. SS amp), if I what I really want is to play off-road (lots of 2nd order harmonics?). But, a lush amp that can't drive my speakers won't do me any good either. As suggested, perhaps my best option is a good PP design with a certain bias adjustment.
Candidates thus far:
As for the Mullard topology, I need to research these in the forums. Would appreciate if anyone could point me to some ideal ones. Also, any thoughts on toroids for output transformers? They don't seem common. Does AnTek make any?
No surprise, but I'm getting excited about this. I blame a number of years listening to a Carver "tube voiced" amp. Some love, some hate, but it led me here nonetheless.
I'm trying to keep the goals from being overly ambitious, and making sure my fabrication skills are adequate is certainly a valid point. A kit chassis wouldn't really be a deal-breaker. It's just a preference.
Sonics, however, are a different matter. I accept my first build will require compromises, perhaps many, so I want to make sure I do enough homework to be aware of what to realistically expect. No sense in building a race car for the track (ie. SS amp), if I what I really want is to play off-road (lots of 2nd order harmonics?). But, a lush amp that can't drive my speakers won't do me any good either. As suggested, perhaps my best option is a good PP design with a certain bias adjustment.
Candidates thus far:
- MkIII
- M-125
- Engineer's amp
- 2 x Tubelab SSE?
- Some Mullard style topology
As for the Mullard topology, I need to research these in the forums. Would appreciate if anyone could point me to some ideal ones. Also, any thoughts on toroids for output transformers? They don't seem common. Does AnTek make any?
No surprise, but I'm getting excited about this. I blame a number of years listening to a Carver "tube voiced" amp. Some love, some hate, but it led me here nonetheless.
Yes, the Simple SE is a single ended stereo board.
You just need to have a balanced signal to start with.
- But take one single ended channel, run a signal into it
- Take another channel, run a 180 degree out of phase signal into that
- Bridge the two channels with a push pull OPT, and voila you have a push pull amp (one channel)
You just need to have a balanced signal to start with.
Unless I'm mistaken, SE designs are not a good match with inefficient speakers. Hence, PP?
I measured a 10V sine wave at the outputs, so I think that's 100/8 = 12 watts or so peak, 6w rms per channel. Not too shabby out of a 6v6
Does AnTek make any? I bought Antek Out put transformers they are Junk.
These polish ones are excellent:
Tube output transformers - Shop Toroidy.pl
These polish ones are excellent:
Tube output transformers - Shop Toroidy.pl
I use Triad VPT series as OPTs. If you balance DC the current through primary they have excellent frequency response.
If you buy an automatic bias board such as the one at audioamp.eu it's quick and easy to do, and it's actually cheaper than using Hammond 1650 series.
If you buy an automatic bias board such as the one at audioamp.eu it's quick and easy to do, and it's actually cheaper than using Hammond 1650 series.
I use Antek power toroids for power, and I've used a few as output transformers, they work fantastically well if used correctly. Even at high ratios. You need to overspec them, and keep a balanced DC load current through them for them to operate properly, and they will not work for SE unless you are using them in parafeed.
I understand they did a run of output transformers a while back that were limited bandwidth for musical instruments and guitar use, but never had a chance to try them. I hear they weren't very good for high fidelity use...
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