Hi, John , i was building a DHT 300B, with 6e5p, 6e6p ,6s45p, they work exceptionally well and for a few bucks, D3a is exceptional too, but Is not the only option.
Hi,
Yes, I built the 6e5p-300b already, and it does work quite well! I tried IT coupled first, but now am using LC coupling and like that very much. I loose the A2 capability, but the sound is very dynamic.
Previously I had been using a direct coupled cathode follower based on 6n6p, which was also quire good.
Really not sure one is better than the other just yet.
I should eventually try the 46 as the driver if I, like Andy, can work out the gain issue in my system.
But, no hurry, I’m really enjoying it as is!!
Best regards,
John
Yes, I built the 6e5p-300b already, and it does work quite well! I tried IT coupled first, but now am using LC coupling and like that very much. I loose the A2 capability, but the sound is very dynamic.
Previously I had been using a direct coupled cathode follower based on 6n6p, which was also quire good.
Really not sure one is better than the other just yet.
I should eventually try the 46 as the driver if I, like Andy, can work out the gain issue in my system.
But, no hurry, I’m really enjoying it as is!!
Best regards,
John
Hello,
force of 1/2 wrote: "Yes, I built the 6e5p-300b already, and it does work quite well! I tried IT coupled first, but now am using LC coupling and like that very much. I loose the A2 capability, but the sound is very dynamic."
Hi force,
A few questions:
1. What IT did you try? What didn't you like about its result?
2. When you changed to LC coupling, what L and what C did you use?
3. What 300B?
I have not built with 300B, but am amassing parts and curiosity.
Thanks and Best Regards,
RC
force of 1/2 wrote: "Yes, I built the 6e5p-300b already, and it does work quite well! I tried IT coupled first, but now am using LC coupling and like that very much. I loose the A2 capability, but the sound is very dynamic."
Hi force,
A few questions:
1. What IT did you try? What didn't you like about its result?
2. When you changed to LC coupling, what L and what C did you use?
3. What 300B?
I have not built with 300B, but am amassing parts and curiosity.
Thanks and Best Regards,
RC
Hi rchamber,
There are many more experienced persons here who would be a better guide, but I will share my two cents. (if it indeed amount to two whole cents!)
1. One of the reasons I may have preferred LC rather than IT coupling was that I used the Hammond 126b. There are, reportedly, much better Interstage Transformers. This is a highly critical component, soundwize, in the circuit (perhaps THE central component in such a simple circuit), but the 126b came to me very cheaply, so I gave them a try.
Transformer coupled, the amp sounded fine! Nothing really to criticize, but it just sounded a little bland, a little held back.
2. The L was the primary of the 126b (rated at 44H @ 30mA). The C was a .47uf K40Y (Russian/Soviet PIO)
3. The 300Bs are Emission Labs 300Bxls. Silly money I spent in a reckless moment, but I do like them. Probably worth the money compared to the Electro Harmonix (EH) 300Bs I have. Especially since they have some real driving power. Biased at 84mA, even in A1 operation, they have no trouble driving my 88db sensitive monitors to very reasonable listening levels. The EH in the same circuit cannot do this.
--After enjoying the amps LC coupled for a month, I recently converted them back to the Direct Coupled cathode follower circuit I had previous to the 6e5p. This driver will stay.
It is an old design, and cathode followers are not in fashion, the amp is 3 stages, but it sounds very lively and real. And A2 operation, I think, is still preferable-- so long as one is not pushing too hard. Lower distortion on transients makes a nice difference.
I linked the schematic below. It is from a radio handbook scanned and posted by Wavebourn.
Post #22 below:
300B schematic recommendations
Good Luck!
Best regards,
John
There are many more experienced persons here who would be a better guide, but I will share my two cents. (if it indeed amount to two whole cents!)
1. One of the reasons I may have preferred LC rather than IT coupling was that I used the Hammond 126b. There are, reportedly, much better Interstage Transformers. This is a highly critical component, soundwize, in the circuit (perhaps THE central component in such a simple circuit), but the 126b came to me very cheaply, so I gave them a try.
Transformer coupled, the amp sounded fine! Nothing really to criticize, but it just sounded a little bland, a little held back.
2. The L was the primary of the 126b (rated at 44H @ 30mA). The C was a .47uf K40Y (Russian/Soviet PIO)
3. The 300Bs are Emission Labs 300Bxls. Silly money I spent in a reckless moment, but I do like them. Probably worth the money compared to the Electro Harmonix (EH) 300Bs I have. Especially since they have some real driving power. Biased at 84mA, even in A1 operation, they have no trouble driving my 88db sensitive monitors to very reasonable listening levels. The EH in the same circuit cannot do this.
--After enjoying the amps LC coupled for a month, I recently converted them back to the Direct Coupled cathode follower circuit I had previous to the 6e5p. This driver will stay.
It is an old design, and cathode followers are not in fashion, the amp is 3 stages, but it sounds very lively and real. And A2 operation, I think, is still preferable-- so long as one is not pushing too hard. Lower distortion on transients makes a nice difference.
I linked the schematic below. It is from a radio handbook scanned and posted by Wavebourn.
Post #22 below:
300B schematic recommendations
Good Luck!
Best regards,
John
"Silly money I spent in a reckless moment..."
Hi John,
Did that last night...bought a pair of the current WE300B...Ouch!
But cjeck the Rossville Works website to see what they're doing...
Rossville Works Manufacturing Facility — Western Electric - Maker of electron tubes and high fidelity
Best,
Robert
Hi John,
Did that last night...bought a pair of the current WE300B...Ouch!
But cjeck the Rossville Works website to see what they're doing...
Rossville Works Manufacturing Facility — Western Electric - Maker of electron tubes and high fidelity
Best,
Robert
> Emission Labs 300Bxls. Silly money I spent in a reckless moment, but I do like them. Probably worth the money compared to the Electro Harmonix (EH) 300Bs
I agree - the EML are better value than EH, despite the high price. The build quality is so much better, and the lifetime seems to match it. The EH still appear to have the filament breakage problem that has been around them for decades. The EMLs sound better to my ears. EML consider A2 operation to be running them out of specification, perhaps best use it sparingly, and forget to mention it if you do need to call on their guarantee.
> It is an old design, and cathode followers are not in fashion
regardless of fashion, a DC-coupled follower is very important to get the best out of 300B SE. Without it, blocking distortion spoils them. Power FET source followers are better still, but all are better than no follower.
I agree - the EML are better value than EH, despite the high price. The build quality is so much better, and the lifetime seems to match it. The EH still appear to have the filament breakage problem that has been around them for decades. The EMLs sound better to my ears. EML consider A2 operation to be running them out of specification, perhaps best use it sparingly, and forget to mention it if you do need to call on their guarantee.
> It is an old design, and cathode followers are not in fashion
regardless of fashion, a DC-coupled follower is very important to get the best out of 300B SE. Without it, blocking distortion spoils them. Power FET source followers are better still, but all are better than no follower.
I only use LC coupling these days. Various plate chokes, some amorphous, and teflon FT-2 coupling caps. The best sound I've had. You could use the excellent Lundahl LL1667 or LL1668 as plate chokes. I've moved on from the 46 and all the gain issues of DHTs. Now using a variety of indirectly heated tubes. The usual suspects - C3g, D3a and also 5A/152M, another German Post tube, all in triode. I only have EH 300bs, nothing exotic. But i use DC Link capacitors as cathode bypasses in self bias and these make quite a difference. The Vishay and Kemet ones I'm using are nicely transparent, and there's also Epcos and WIMA.
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Should work on paper but it didn't work in practise. I did that with a 126C. Big treble drop whichever way you connected it, and I did try everything. I think this is because it's bifilar wound. Works fine as just a plate choke using the primary.
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This brings me to ask a question I have been wanting to ask, but I've been a bit squeamish on starting any trouble with it.
Why is it that, like Andy, I seem to constantly prefer choke coupling to transformer coupling?
Theoretically, a transformer coupled circuit should be free from blocking distortion, too--if it were only a matter of blocking distortion.
Even with my DHT preamps using good quality Lundahl transformers, I prefer LC coupled output, employing the transformer as a choke. This sounds more realistic to my ears, coupling cap and all.
Do I need to go up even further in price with the transformers?
Or is there something inherent in transformer coupling that just isn't jiving with my expectations?
Now, I am not suggesting that signal-duty transformers are categorically flawed. I really like my Sowter 1480 phono Step Up Transformers. No matter what phono pre I have hooked up, it always sounds better with the SUTs than without.
The simplicity of transformer coupling makes it rather seductive to pursue for one like me who is no E.E.
I'm being lazy, perhaps.
Best regards,
John
I can only agree. I've used LL1660/18mA as either interstage, or plate choke using just the primary. Coupling caps are teflon FT-2. I prefer the sound when using it as a plate choke. I've read that the LL1660 and maybe other similar interstages are best used in step down, but that's not my case - I want the full available output.
Well, Lundahl builds great chokes. The Power Transfromer as well
But the IT are not the best you can get. Monolith is another class. But still has its own sound. Got some custom wound and now I have a transparency coupling caps cant match...
I like the beauty of how many things a IT does for you at the same time....constant current source/horizontal load line, energy storage, decoupling, grid-choke just to name a few....so IF you find a winder you are saftisfied with, its quiet satisfying.
But the IT are not the best you can get. Monolith is another class. But still has its own sound. Got some custom wound and now I have a transparency coupling caps cant match...
I like the beauty of how many things a IT does for you at the same time....constant current source/horizontal load line, energy storage, decoupling, grid-choke just to name a few....so IF you find a winder you are saftisfied with, its quiet satisfying.
Well said, theoretically. In practice there are few transformers that will perform as intended.
It's not just the transformer but also the driver. You have to find the right combination which might lead to a different solution, like you can't do a 2 stage amp with the 300B....
Choke load allows you more freedom in picking a driver.
Having said this I had great success in driving the 300B with the 46 and Tango NC-20. Far superior to choke loading which was the initial solution. The 6H30 also worked very well with the NC-20.
On the other end if you use self-bias for the 300B and pick the right working point you avoid driving into positive grid and the blocking becomes a minor issue or even irrelevant. With the 300B, you get more efficiency by going into positive grid but the gain in output power is considerably less than other triodes. This is because the 300B is already quite efficient in class A1. 30-33% anode efficiency is not difficult to obtain.
Well Lundahl not really great ITs except, maybe, the LL1692a and the LL1660 in few specific applications. The LL1635...you remember the pair I bought from you...still sitting in a box. Not really good and very fussy about mounting and wiring layout. They are extremely prone to pick up parasitic capacitances which in turns is reflected in poor frequency response. In some cases the frequency response was dropping already at 6-7 KHz, despite I did not do anything different from usual.....
I wonder how the CCS loaded C coupled drivers perform soundwise...I just bought a cheap chinese kit for a quick and dirty 6sn7 - drives - 300B with tube rectification project.
The schematic of the chinese was rubbish, I checked the pcb and its a directly coupled 6sn7 drives 6sn7 driver, c coupled to the 300B...I put it into LTspice and the performance of that driver...well...needed help. I can post the schematic.
No matter what I tried, I could not make the 6sn7 RC loaded with 22k and approx. 5mA to behave nicely enough to drive the 300B. The game started to vhange when I give it an IT or a CCS load at least...in LTspice. I wonder how well this sounds with the CCS, which fits as a low cost solution for such a low cost setup...
The schematic of the chinese was rubbish, I checked the pcb and its a directly coupled 6sn7 drives 6sn7 driver, c coupled to the 300B...I put it into LTspice and the performance of that driver...well...needed help. I can post the schematic.
No matter what I tried, I could not make the 6sn7 RC loaded with 22k and approx. 5mA to behave nicely enough to drive the 300B. The game started to vhange when I give it an IT or a CCS load at least...in LTspice. I wonder how well this sounds with the CCS, which fits as a low cost solution for such a low cost setup...