I know this topic has been beaten to death, but I never feel like it gets answered.
I currently have a diy amp my friend built me. It is a simple 6sl7 into a 350b strapped in triode. It sounds great, but I am hitting the limitations of what it can do and I think I am ready to graduate to the big boy tubes and I have run into that age old question. 2a3 or 300b.
Before we go any further, please know that I know circuit design is going to play a massive role in determining the sonic properties of the amp. The issue I am running into is that I have some design ideas, but I can't even settle on a circuit design until I figure out which output tube I should use.
Let me give you some back ground before we start. I am looking at making a single ended amp. I probably won't be using this amp with any speakers below 90db efficiency, so output power isn't that big of a concern.
I have heard the 300b and the 2a3 tubes in some audionote amps, But they were parallel 300bs vs a 2a3 amp. So it wasn't exactly apples to apples.
I am looking for a lush warm sound with a big sound stage and great imaging.
My current thought is to use a 2a3 or a 300b and some type dht driver tube in a direct coupled configuration.
Tell me what your thoughts are. Should I be focusing my efforts towards a 2a3 or a 300b?
I currently have a diy amp my friend built me. It is a simple 6sl7 into a 350b strapped in triode. It sounds great, but I am hitting the limitations of what it can do and I think I am ready to graduate to the big boy tubes and I have run into that age old question. 2a3 or 300b.
Before we go any further, please know that I know circuit design is going to play a massive role in determining the sonic properties of the amp. The issue I am running into is that I have some design ideas, but I can't even settle on a circuit design until I figure out which output tube I should use.
Let me give you some back ground before we start. I am looking at making a single ended amp. I probably won't be using this amp with any speakers below 90db efficiency, so output power isn't that big of a concern.
I have heard the 300b and the 2a3 tubes in some audionote amps, But they were parallel 300bs vs a 2a3 amp. So it wasn't exactly apples to apples.
I am looking for a lush warm sound with a big sound stage and great imaging.
My current thought is to use a 2a3 or a 300b and some type dht driver tube in a direct coupled configuration.
Tell me what your thoughts are. Should I be focusing my efforts towards a 2a3 or a 300b?
If you want a "lush warm sound" DHTs are not the way to go. An all-DHT amp will be crystal clear, transparent and detailed but not lush and warm. If you are prepared to sacrifice some of the detail and transparency, then use an indirectly heated driver tube with enough gain to drive a 300b or 2a3 output. Take your pick - anything with a mu of 60 or more. Plenty of designs including direct coupled. But the thing is that this is what you already have and you want something else. It would help to know why and what you are missing.
If you truly want to go down the all-DHT route and join myself and several others who only build with DHTs then you will be using tubes with a mu of between 8 and 15. Take your pick of 26, 01A, 112A, 10Y, 4P1L. All these can be used in filament bias.
Go to Bartola Valves website and look at 01A preamp Gen 2. This is the best line or driver stage out there - what I use myself. It uses Ale's Gyrator boards and Rod Coleman filament regs available from Lyrima.com.
On the Bartola site you will also find schematics for a 2 x 4P1L output stage in filament bias. This is what I use - just a 2 stage amp into my 89db speakers in a smallish room. Since the 4P1L has a mu of around 11 you can then build your 2 stage amp. The sound in filament bias is super clean - no cathode bypass cap. You will get the maximum transparency and clarity this way.
You need abandon conventional thinking if you go down this route. The circuit is very simple but it does require very clean filament supplies and Rod Coleman regs, a pair for each stage. I use choke input on the filament supplies as well. All this is on the Bartola site. Go over there and have a good read. None of us building in filament bias are using 300b or 2a3 outputs - they don't work that way and you'll need to directly bias them or use cathode bypasses. All this can be avoided by using 4P1L outputs, and they are very cheap and reliable tubes and in filament bias they're a direct match for 2a3 and 300b in sound quality.
If you truly want to go down the all-DHT route and join myself and several others who only build with DHTs then you will be using tubes with a mu of between 8 and 15. Take your pick of 26, 01A, 112A, 10Y, 4P1L. All these can be used in filament bias.
Go to Bartola Valves website and look at 01A preamp Gen 2. This is the best line or driver stage out there - what I use myself. It uses Ale's Gyrator boards and Rod Coleman filament regs available from Lyrima.com.
On the Bartola site you will also find schematics for a 2 x 4P1L output stage in filament bias. This is what I use - just a 2 stage amp into my 89db speakers in a smallish room. Since the 4P1L has a mu of around 11 you can then build your 2 stage amp. The sound in filament bias is super clean - no cathode bypass cap. You will get the maximum transparency and clarity this way.
You need abandon conventional thinking if you go down this route. The circuit is very simple but it does require very clean filament supplies and Rod Coleman regs, a pair for each stage. I use choke input on the filament supplies as well. All this is on the Bartola site. Go over there and have a good read. None of us building in filament bias are using 300b or 2a3 outputs - they don't work that way and you'll need to directly bias them or use cathode bypasses. All this can be avoided by using 4P1L outputs, and they are very cheap and reliable tubes and in filament bias they're a direct match for 2a3 and 300b in sound quality.
Andy is entirely correct. However, if you want a lush (as opposed to clear and accurate) sound a cascaded 6SN7 into 300B (eg Morrison, Joseph Esmilla circuits) would fit the bill, as would a standard WE91A 300B circuit.
There is a very intersting solution with 2A3-40 JJ that is a 300B with the filament at 2.5 volts. The curves are exactly the same of standard 300B
You can use the normal 2A3 or this one with same output trafo but different voltages and bias current and different input stage ( just to fix the right swing).
Walter
You can use the normal 2A3 or this one with same output trafo but different voltages and bias current and different input stage ( just to fix the right swing).
Walter
Thanks for the reply. Your insight is extremely interesting.
To start, I will give you an idea of what is going on with my amp. Like I mentioned before, I have a parallel 6sl7 (I am actually using a JAN 6su7gty) going into a valve art 350b strapped in triode. The biggest issue I have with is that it either has bass and the vocals are recessed, or the vocals are very forward with very weak bass.
It seems like those two characteristics are constantly fighting with one and other no matter what I do to the circuit. That's why I am actually trying to turn it into a directly coupled amp. I wan't to remove the coupling caps as a factor and see if that doesn't get me closer to what I want.
Even if I do manage to nail down the circuit and get a well rounded tone, I am afraid it still wont have the sound stage and imaging of a DHT amp.
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I am going to research this website before I open my mouth and ask any stupid questions. 😀
Interestingly enough, my friend who built my current amp is also building a tube dac based off the dac end. This 01a tube looks like a super interesting tube for a dac.
If you guys think an indirectly heated triode might be a better fit for me, then I als have a favor to ask. I had run across this tube the other day and I had made a note of it and lost it.
I think it was called a 5481 or something like that. It was a single INDHT with a mu above 30. I must have the wrong name because I can not find it.
If you guys know what I am talking about, could you let me know what it is and what your thoughts might be on using it over a 10y or a 26?
You mean 5842 or 417A
https://frank.pocnet.net/sheets/049/5/5842.pdf
Also look at D3A, E180F, E280F, E810F, EC8020, EC8010, 8532, 6GK5, and a few others including Russians like 6S45
I still think you're on the wrong track with DHTs. Again, you won't see huge improvements in soundstage and imaging. That's not what DHTs are about - they are about clarity. And coupling caps aren't the villains either - a good teflon coupling cap doesn't do much harm. Your problems with bass response and recessed vocals are also nothing to do with DHTs - something in your system is causing this anomaly.
I think you've spent too much time reading the popular Hi-Fi press and picking up some old wives tales along the way. You should hopefully get better information in this thread - there are some very sharp guys on this forum who really know their electronics.
https://frank.pocnet.net/sheets/049/5/5842.pdf
Also look at D3A, E180F, E280F, E810F, EC8020, EC8010, 8532, 6GK5, and a few others including Russians like 6S45
I still think you're on the wrong track with DHTs. Again, you won't see huge improvements in soundstage and imaging. That's not what DHTs are about - they are about clarity. And coupling caps aren't the villains either - a good teflon coupling cap doesn't do much harm. Your problems with bass response and recessed vocals are also nothing to do with DHTs - something in your system is causing this anomaly.
I think you've spent too much time reading the popular Hi-Fi press and picking up some old wives tales along the way. You should hopefully get better information in this thread - there are some very sharp guys on this forum who really know their electronics.
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Cool, thanks 😀
And yes, I am well aware of everything you are telling me. I should be a bit more specific. All DHT amps I have ever heard do actually have more sound stage than INDHT or pentode amps. I am not trying to make a generalization, I am simply stating that my personal experiences lead me to believe that I will actually gain quite a bit of sound stage over my current amp.
And yeah, as far as the caps go, I also know that coupling caps are not the enemy. But I have already tried russian PIO caps, and hovland signal caps. Other than throwing a crap ton of money at different coupling caps, I am kind of at a loss as to what I can do. My thought is that if I directly couple the tubes, and the vocals suddenly improve, then I will at least know I am on the right track and will feel a lot more comfortable buying the really expensive audio note caps.
As for your comment about DHTs not solving the problem....I agree but here is here is where my mind it. I guess I am at a point where I have two options. Keep trying to chase my own tail with this amp and dump a bunch of money into it with no promise that it will ever get better. Or just go with something totally different.
And yes, I am well aware of everything you are telling me. I should be a bit more specific. All DHT amps I have ever heard do actually have more sound stage than INDHT or pentode amps. I am not trying to make a generalization, I am simply stating that my personal experiences lead me to believe that I will actually gain quite a bit of sound stage over my current amp.
And yeah, as far as the caps go, I also know that coupling caps are not the enemy. But I have already tried russian PIO caps, and hovland signal caps. Other than throwing a crap ton of money at different coupling caps, I am kind of at a loss as to what I can do. My thought is that if I directly couple the tubes, and the vocals suddenly improve, then I will at least know I am on the right track and will feel a lot more comfortable buying the really expensive audio note caps.
As for your comment about DHTs not solving the problem....I agree but here is here is where my mind it. I guess I am at a point where I have two options. Keep trying to chase my own tail with this amp and dump a bunch of money into it with no promise that it will ever get better. Or just go with something totally different.
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What you are calling "DHT amps" are likely to be amps with indirectly heated drivers and DHT outputs. That's not an all-DHT amp and won't give you the real benefits of DHTs. For that your input stages also need to be DHTs. That's just as important as the outputs. But all-DHT commercial amps are extremely rare. You need to build an all-DHT amp as a DIY project.
It's worth doing - vocals are hugely improved, together with the clarity you get anyway. If you are really serious about DHTs build the projects on Bartola Valves site. Forget expensive Audionote caps - just use Russian FT-2 or FT-3 teflon caps. Very detailed and very cheap. Build a 01A Gen 2 stage into 2 x 4P1L outputs. Again - cheap tubes. If you can't build this kind of amp yourself you'll need someone who understands these circuits to build it for you. It can be done by anyone with a good knowledge of amp building - the information is available in a few DIY Audio threads on 4P1L, 01A and 26 preamp.
It's worth doing - vocals are hugely improved, together with the clarity you get anyway. If you are really serious about DHTs build the projects on Bartola Valves site. Forget expensive Audionote caps - just use Russian FT-2 or FT-3 teflon caps. Very detailed and very cheap. Build a 01A Gen 2 stage into 2 x 4P1L outputs. Again - cheap tubes. If you can't build this kind of amp yourself you'll need someone who understands these circuits to build it for you. It can be done by anyone with a good knowledge of amp building - the information is available in a few DIY Audio threads on 4P1L, 01A and 26 preamp.
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hmmmm, although I don't have the experience of these projects, this is the first thread I can remember where I'm reading that a good amplifier using IDHT as drivers for a 2A3 output are incapable of giving clarity and that an all-DHT system is required if that is the goal. I'm unable to think of any engineering reason for this either.
Ohhhhhhkay. Now I see what you are getting at. I will talk with my friend about the 01a gen 2 preamp. I kind of wanted a preamp anyways and this seems fairly cheap.
I will also try some teflon caps and see if that doesn't help the amp at all.
I'd go with the 300B due to the higher output power. I get 10 W out of my DG300B. I'm sure the 2A3 is sweet as well, but if I was going for lower power, I'd probably consider the 45 rather than the 2A3.
Tom
Tom
Tjj226,
If you are planning to use a 2 way or a 3 way speaker with the tube amp, take a look at the speaker's impedance curve. Some speakers are quite difficult to drive vs others even though sensitivity ratings might be similar.
Are you decided on the DHT route only? Or willing to explore other options?
If you are planning to use a 2 way or a 3 way speaker with the tube amp, take a look at the speaker's impedance curve. Some speakers are quite difficult to drive vs others even though sensitivity ratings might be similar.
Are you decided on the DHT route only? Or willing to explore other options?
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It would be nice if we had a schematic of your amplifier, including the 350B plate voltage,
self bias voltage (or fixed bias voltage; state which one), plate current, and transformer primary impedance.
It would also be nice if you state what loudspeakers you are using.
Here are a couple of examples of what a triode wired 350B can do.
(Compare that to what a New Old Stock (NOS) 45 can do 2 watts at 5% if the output transformer is very low loss).
Western Electric 350B Triode Wired
250V plate 250V plate
-20V grid -20V grid
50mA 50mA
5000 Ohm load 6000 Ohm load
1.7 Watts 1.5 Watts
5 % THD 6% THD
Start with exactly what you have, and perhaps one of us can get you where you want to be.
self bias voltage (or fixed bias voltage; state which one), plate current, and transformer primary impedance.
It would also be nice if you state what loudspeakers you are using.
Here are a couple of examples of what a triode wired 350B can do.
(Compare that to what a New Old Stock (NOS) 45 can do 2 watts at 5% if the output transformer is very low loss).
Western Electric 350B Triode Wired
250V plate 250V plate
-20V grid -20V grid
50mA 50mA
5000 Ohm load 6000 Ohm load
1.7 Watts 1.5 Watts
5 % THD 6% THD
Start with exactly what you have, and perhaps one of us can get you where you want to be.
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For 90db speakers I would build 2a3 PP. Just sayin' 🙂
Also, 5% or 6% THD is waaay too much for my taste.
Ian
Also, 5% or 6% THD is waaay too much for my taste.
Ian
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I didn't say that IDHTs don't give clarity - just that to my ears DHTs have an extra dimension of clarity. Again, the extent of the difference may be tiny and not show up on a scope. All the difference needs to be is audible. I've been working with DHT input tubes like 26, 01A, 10Y and 4P1L for around 8 years now and I can hear a difference otherwise I wouldn't use them. I'm clearly not the only one - the 26 preamp thread is huge, for example. Other people are hearing the same thing. I'm using the word "clarity" but others might use different words. It's hard to put sound into words as we all know, but we try.
The other point I'm making is that if you make the choice of a DHT output tube like 2a3 or 300b, then why would you not want to use the same criteria - whatever they are - for choosing a DHT input tube as well? By choosing a DHT output tube you are already admitting that this is a superior sound, otherwise why use it?
I had a PM about using filament bias with a 2a3. It's "possible" but I doubt if anyone would want to do it. You would want 45v at the top of the cathode resistor and it would be passing a current of 2.5 amps + 60mA. That gives you a resistor of 17.5 ohms. It would be required to be 115 watts and since it's going to get very hot you need to at least double that. So your cathode resistor is 17.5 ohms rated 250 watts. It will be hot, so think heatsinks. Your filament supply will be around 52v at 2.5A. That's some ask.
Two 4P1L in filament bias will give you the same power as a 2a3 - maybe a touch more even - and a mu of around 11 compared to around 4. Cathode resistor for two tubes wired with series filaments, then in parallel would be around 28 ohms at 25 watts. Filament supply would be around 29v at 630mA. That's quite easy to implement.
Two 4P1L in filament bias will give you the same power as a 2a3 - maybe a touch more even - and a mu of around 11 compared to around 4. Cathode resistor for two tubes wired with series filaments, then in parallel would be around 28 ohms at 25 watts. Filament supply would be around 29v at 630mA. That's quite easy to implement.
Uhhh, well . . . not all recordings are mixed and mastered the same so it's unrealistic to expect them to all have tonal characteristics that match your taste.
The solution is not to redesign the circuit or build an expensive new amp. Just add a studio quality EQ, either graphic or parametric, and adjust as necessary. Simple.
I know most here probably consider this advice as heresy 😱 but you can be absolutely sure that the recording and mastering engineers used exactly the same type of components during the recording, mixing and mastering process. Their EQ choices just don't seem to align with your preferences, that's all.
When a recording engineer doesn't like the tonal balance of a recording, they don't build a new studio, they tweak a few knobs.
my PP 6B4G amps run out of gas on big orchestra on 93db speakers, though it is a fairly large room.
They get loud enough - but the distortion at top output is too high. It's not bad - just not good enough.
There's a case to be made for a PP 300b amp. I'd use a 4P1L to drive the outputs, into a phase splitter interstage. Maybe something like a LL1660S. It would need to be gapped for 25ma.
http://www.lundahl.se/wp-content/uploads/datasheets/1660S.pdf
Then drive that with a 01A Gen 2 stage. Should sound great. I don't need the power, but I'm sure I'll build it one day just to see how it sounds.
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