andyjevans: I placed an order on a pair of 1140-LN-C. I figure that if I don’t use them on the push-pull discussed in this thread, I can use them in a single ended amp with a low amplification front end. I have many 26 tubes, so I’ll probably go that route instead of the 10Y, that are expensive and that I don’t have. I have a nice selection of 46 tubes as well.
I really like your building method using sub chassis that are easily exchangeable. I have moved toward an analogous building method that uses interchangeable aluminum top plates that are screwed into a standardized wooden frame. Thanks for the idea!
45: Thanks for your post. I have three matched quads of EL34s on hand, and was hoping to use them in a push pull build. My primary motivation for leaving my SET comfort zone is the pair of Plitron, Menno van der Veen designed, push pull output transformers languishing in my parts pile. I have to look at the model number, but I recall them being 6K to 6 ohms. I don’t have any type 49 tubes, but I do have many 46 on hand. They are not nearly as efficient as the 49, , but I have them and the transformers required to run their filaments with a Coleman regulator. I have many 26 tubes too.
46 is an excellent tube. I love it next to the 10Y. Gain is less - 5.6 instead of 8. But you would be OK with EL34s and a step-up. I used it in filament bias, but that was for SE. It needed a big heat sink and the cathode resistor on top of the chassis. You probably wouldn't want to bother in push-pull.
The 26, on the other hand, is easy to use in filament bias.
The 26, on the other hand, is easy to use in filament bias.
You can use the 46 and other similar tubes but I see them as overkill. The 49, I can tell you where to buy it at modest cost. Your Plitron will be fine.
My Gold Standard
So here I am, John L Stewart, former boy experimenter with my Gold Standard Amp. My wife & some of my less than critical friends agree that my Gold Standard Amp sounds very good indeed.
So one day, another former boy experimenter visits & tells me the amp sounds very natural, whatever that means. He asks me to bring my Gold Standard Amp to his house, let his wife hear this marvel.
At the appointed time I appear with the amp & we hook it up to my friends very expensive, high end loudspeakers. To my amazement my Gold Standard Amp no longer sounds the same. But still OK, everything in the system is OK.
So what happened? I’m thinking maybe my friends loudspeakers have added a different flavor to the sound we are hearing. What to do?
The sound system comes to us in at least three parts. The amplifier is only one of those. And besides the loudspeaker there is also the listening space. And as a side issue we could add in some good wine. Or maybe weed, your choice & enjoy.
So here I am, John L Stewart, former boy experimenter with my Gold Standard Amp. My wife & some of my less than critical friends agree that my Gold Standard Amp sounds very good indeed.
So one day, another former boy experimenter visits & tells me the amp sounds very natural, whatever that means. He asks me to bring my Gold Standard Amp to his house, let his wife hear this marvel.
At the appointed time I appear with the amp & we hook it up to my friends very expensive, high end loudspeakers. To my amazement my Gold Standard Amp no longer sounds the same. But still OK, everything in the system is OK.
So what happened? I’m thinking maybe my friends loudspeakers have added a different flavor to the sound we are hearing. What to do?
The sound system comes to us in at least three parts. The amplifier is only one of those. And besides the loudspeaker there is also the listening space. And as a side issue we could add in some good wine. Or maybe weed, your choice & enjoy.
Attachments
Room acoustics, quality of the recordings and source are definitely the most important ones in the audio chain. Then come the loudspeakers and how they integrate into the room. Finally the amplifier which is definitely the strong link.
The loudspeaker load needs to match the capabilities of the amplifier as there are 3 types of the latter: constant current, constant power and constant voltage type. Tube amps are constant power type. The reason why the loudspeaker load need to change is that it's much easier to do so with some tweaks, not every time tough, while one type of amp cannot change into another. That's all.
The industry has chosen amplifiers that behave, or try to behave, as constant voltage source because it's cheaper and more convenient but there is no best. Every solution has its strength and weakness. I said "try to behave" because very few can really do it while tube amps work as they should or very nearly all the time and that's why they are still fine if loudspeakers match.
At the end of the day an overall standard is impossible if following technical specs, simply because room acoustics, which is the n.1 element for importance, changes wildly from one user to another even if nowadays there are some solutions to tame some issues. When I hear standard based on technical specs, I immediately think of an illusion that has been created by industry to sell. Remember the low distortion race a few decades back?
The musical sound is the only possible standard. That's how I see it.
The loudspeaker load needs to match the capabilities of the amplifier as there are 3 types of the latter: constant current, constant power and constant voltage type. Tube amps are constant power type. The reason why the loudspeaker load need to change is that it's much easier to do so with some tweaks, not every time tough, while one type of amp cannot change into another. That's all.
The industry has chosen amplifiers that behave, or try to behave, as constant voltage source because it's cheaper and more convenient but there is no best. Every solution has its strength and weakness. I said "try to behave" because very few can really do it while tube amps work as they should or very nearly all the time and that's why they are still fine if loudspeakers match.
At the end of the day an overall standard is impossible if following technical specs, simply because room acoustics, which is the n.1 element for importance, changes wildly from one user to another even if nowadays there are some solutions to tame some issues. When I hear standard based on technical specs, I immediately think of an illusion that has been created by industry to sell. Remember the low distortion race a few decades back?
The musical sound is the only possible standard. That's how I see it.
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John: You are very right. Synergy between components and room really are important. The state of mind of the listener is a very important part of that synergy. When you consider the inherently artificial nature of stereo reproduction, especially as compared to how we experience music in person when it is performed live, the obsession with fidelity to the source makes less sense. The source is intentionally artificial. Mono is all the sound coming from one place, which is artificial, and stereo is all the sound coming from two sources, which is also artificial. Maybe certain types of distortion are needed to improve the perceived realism of this artificial construct? Regardless, THC enhances this perceived realism and our enjoyment of a system. Using the admittedly small sample of people that I know, this appears to be a nearly universal experience. How do we go about measuring this reality objectively?
If one is to use an input transformer then that's the phase splitter right there. From that point on just make the circuit symmetrical.
I like the word flavor in audio. Flavorless audio is "neutral" and boring. Get that DHT flavor as much as you want.
I like the word flavor in audio. Flavorless audio is "neutral" and boring. Get that DHT flavor as much as you want.
I'll probably go with a 26 with filament bias or a 46 without it. 45 recommends the 49, but I went through my stash and couldn't find any, and I'm loath to buy some when I have so many tubes already that I'm not using and could.
I'm unfamiliar with push-pull amp topologies. Is there a schematic that I could look at that uses this topology?
Mono might be boring sometimes.
But then, listen to Andres Segovia play his guitar. Mono is great!
All you need is a good Mono Recording Engineer.
And, do not try and play that back on a 2 channel stereo; only use 1 channel.
If you play it on two channels, you are totally missing the point.
But then, listen to Andres Segovia play his guitar. Mono is great!
All you need is a good Mono Recording Engineer.
And, do not try and play that back on a 2 channel stereo; only use 1 channel.
If you play it on two channels, you are totally missing the point.
I find that I like mono best when the recording is of a single musician playing their instrument. It is most like what you would experience if you were at the performance.
Much better than the 30 and better than 26 as well.
In general, I NEVER attach tubes directly to the chassis. There is NO tube that doesn't show microphonics whatever type you wanna consider and whatever selection you wanna do.
So something along the lines of a PP version of the inverted SET (iSET) concept that Andy introduced a while back. Glad to hear that your 30 / 6BQ5 version turned out well. I also built an iSET last year, which I've dubbed the Nuance. I used 26s on the input after breadboarding numerous DHTs.
My current project is using those Hammond 1140-LN-Cs, also on Andy's recommendation, and I'm really liking them in the SE amp I have on the breadboard, which is using all DH tubes in a directly coupled design.
And, one of the two input tubes that have impressed me the most so far is the 49, which "45" is suggesting. It's wonderfully detailed and I haven't experienced any problems with microphonics in normal use.
I would, however, suggest that you audition input tubes rather than decide on one type going in. Just because one tube sounds good in one amp doesn't mean it's the best choice in a different design. For example, I tried the 26s in my current project and they didn't sound nearly as good as the 49 (which I hadn't tried before) or the 12A, which I had tried when I was breadboarding the Nuance where it was unimpressive.
The 7591 / 7868, which you mentioned earlier, is easy to drive but I can't say I've ever heard of it being used in triode so I wonder if there's a reason for that? I've thought of using it SE (but not in triode) as its power output is greater than a 6BQ5, which is also very easy to drive. But then I noticed that its published SE power rating is at 13% distortion, so I wonder if, when measured at the same distortion levels, it really offers much more power than a 6BQ5. It seems to be one of those tubes that works much better in beam mode and PP.
For the Nuance I used the 6N6G, which is a dual dissimilar triode that's also very easy to drive. We've discussed it before. I also used them in a modded PP Magnavox amp that originally ran 6V6s and I really like them there too. It runs them in 'normal' PP mode, where they put out 10 wpc, but the data sheet also describes a 'high power' PP mode that produces 20 wpc.
This thread has got me thinking about a similar project since I also like to use parts I have on hand and I've got a slew of PP transformers that I've collected over the years.
Given my positive experience with the 1140-LN-Cs, I'm especially interested in the idea of using an input transformer to invert phase. The 1140s are installed "backwards" in order to create a step up. I assume they could be flipped and used for phase inversion (??) but then you'd lose the step up that's necessary.
It seems like a configuration like this would require both a step up and inversion, right? It would be nice if a single transformer could be used but I suppose you could also use one as a step up and a separate one for inversion. This is unknown territory for me.
Does Hammond make something that would be suitable as a single solution to provide both step up and inversion? Or could two 1140-LN-Cs (per channel) be used in combination? Their price / performance ratio is very favorable.
Tubes designed for or have inherently low microphonics 26, 264 & 864. Each have a short, thick filament. 👍
Charlie: It is unknown territory for me as well. This goes for using transformers for gain and phase splitting, and for phase splitting in general. I have had many years of building SET amps and largely ignoring push pull topology. If I understand one option correctly, a Hammond 1140-LN-C can be used at the input for both gain and phase splitting, and then, basically, a separate set amp can be built per phase and then put back together at the push pull output transformer. This is the one that makes sense to me as a complete push pull novice. Coming to this hobby with no electronics training whatsoever, I need to learn more. In general, using a decent, by most accounts, reasonably priced transformer like the 1140-LN-C allows for many more options with a two stage topology across the board. In the case of single ended triode amps, the 1140-LN-C allows for the use of lower gain DHT triodes that would otherwise not have enough gain to be useable with most power tubes in a two stage amplifier. I suppose that the transformer can be considered a stage, so that technically, it isn’t a two stage amp anymore if you use one.
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I think the 1140-LN-C will work very well as phase splitter. It's a bridging unbalanced-to-balanced transformer and it has even higher input impedance than the Sowter at 36K. Like the Sowter, the Hammond is low distortion as well and can take 21 dBV. All good!
The only problem would be that it's a step-down (4:1 full primary to full secondary) while the Sowter 1475 is step-up (1:2) in the same configuration. So it will be nearly impossible to make a 2 stage power amp with the Hammond + DHT driver. Maybe some fancy tube like the 841. But is it really worth?
Instead it would work great with signal tubes like a 12AY7, 12BZ7 and anything linear with mu around 40 or higher, IMHO. High mu tubes will be fine also respect to Miller capacitance as the transformer is step-down.
The only problem would be that it's a step-down (4:1 full primary to full secondary) while the Sowter 1475 is step-up (1:2) in the same configuration. So it will be nearly impossible to make a 2 stage power amp with the Hammond + DHT driver. Maybe some fancy tube like the 841. But is it really worth?
Instead it would work great with signal tubes like a 12AY7, 12BZ7 and anything linear with mu around 40 or higher, IMHO. High mu tubes will be fine also respect to Miller capacitance as the transformer is step-down.
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