A plea to all you wise tube heads... I'm a constructor (not designer) looking for a design to build but am punch drunk at the number of choices out there. I need 10-20w into 4ohms. It must have great resolution, excellent transparency in the treble especially, and throw a nice walk in soundstage. The rest can take a back seat. I have experience of a KT88 PP amp which was a bit brash, also a triode strapped EL34 which was very good. The rest? No idea. I am willing to spend medium money on parts and take my time. Based in the UK. Thank you in advance for any words of wisdom.
Just to give us a head start, what sorts of options have you looked at? The big question is SE or PP. One candidate is the Tubelab SPP with EL84 PP, which is very well supported here. I used Toroidy transformers, and they can all be purchased for around £200 from TME.EU in the UK.
What sort of final presentation are you after?
What sort of final presentation are you after?
I've looked at EL34 and EL38 Baby Huey, Podwatt EL84 PP, Claus Byrith 5-20 PP in detail. Skimmed a million others. I think it will need to be a PP. A 10-20W SE will need something like a KT88 which as I outlined above didn't sound as sweet as the EL34's I heard.
I'm after a high resolution, natural presentation. I listen to a very wide range of music. I don't need lots of 2nd harmonic sugar but the presentation must have excellent high frequency control. I can't stand sibilance, grit or grain. Bass weight and extension are less of a priority for me.
I'm after a high resolution, natural presentation. I listen to a very wide range of music. I don't need lots of 2nd harmonic sugar but the presentation must have excellent high frequency control. I can't stand sibilance, grit or grain. Bass weight and extension are less of a priority for me.
Tubelab Simple Push-Pull EL84.
Proven design, works great and easy enough to build for a valve noob like me.
Here is my rendition:
Proven design, works great and easy enough to build for a valve noob like me.
Here is my rendition:
Around 10W all triode PP amp , low parts counts and is relative simple to be assembled.
https://www.dmitrynizh.com/hf60-dht.htm
https://www.dmitrynizh.com/hf60-dht.htm
Attachments
What are the manufacturer and model number of your 4 Ohm Loudspeakers?
DCR of the loudspeaker?
Efficiency?
Remember, 2.828Vrms is 2 Watts into 4 Ohms.
DCR of the loudspeaker?
Efficiency?
Remember, 2.828Vrms is 2 Watts into 4 Ohms.
I'll make my usual recommendation for an American-style Williamson. You won't find a smoother, more natural-sounding amplifier, IMO. ;-) Excellent high-frequency extension, realistic midrange and tight, full bass. Member THD+N has posted an 807 version using an Edcor output tranny, you can search the forum for it. Mine is based on the original "Musician's Amplifier" and uses a Heyboer copy of the Peerless S-265-Q output. I know three fellow hobbyists who have built this version and they love the amps. Just my two cents! ;-)
grovergardener,
Can you spell Heathkit W5-M?
Your posted schematic seems to be the same thing.
If you can find the Heathkit W5-M manual, there is a very important graph on the very last page.
It shows the harmonic distortion at very low frequencies, versus the delta quiescent voltages of the output tube cathodes (cathode current difference).
Even though there is global negative feedback around the output transformer, the low frequency harmonic distortion rises rapidly, if the quiescent cathode currents are not very well balanced.
All W5-M and Heyboer owners take note.
Can you spell Heathkit W5-M?
Your posted schematic seems to be the same thing.
If you can find the Heathkit W5-M manual, there is a very important graph on the very last page.
It shows the harmonic distortion at very low frequencies, versus the delta quiescent voltages of the output tube cathodes (cathode current difference).
Even though there is global negative feedback around the output transformer, the low frequency harmonic distortion rises rapidly, if the quiescent cathode currents are not very well balanced.
All W5-M and Heyboer owners take note.
No, it's not a Heathkit W5. The schematic was adapted from a W4, which is basically a "Musician's Amplifier" with a different output transformer, as were the W3 and W2. It differs from the "Musician's Amplifier" only in the step filter and phase-lead cap for stability, and a simplified power supply. As with all true Williamsons, the output tube balancing system is in place, with the addition of two resistors to make measuring the balance easier.
Nobody ever tries my own basically simple design of a PP UL EL84 amp that puts out 17Wch and sounds just lovely driving a pair of floor-standing 4 ohm Advent Maestros.
It's been in occasional service since 2006 and its performance is in my opinion outstanding.
But, I'll post it on here once again... in case.
It's been in occasional service since 2006 and its performance is in my opinion outstanding.
But, I'll post it on here once again... in case.
Yeah, but it's NOT for beginners. 😱
PP El84 class A is where it's at for someone starting out with tubes, where 12 watts/ch is enough. If you want more power than that, there are a bazillon choices.
jeff
Last edited:
A word of recommendation based upon 20 years of experience. Anything Grover decides is ready for the masses will be trouble free. I used his 845SE for 19 years never even blowing a fuse. I recently passed them on to their forever homes because at age 81 I am no longer strong enough to comfortably lift them and they were doomed to be dropped. 75 lbs is just more than I can handle and arises from the great amount of Cu and Fe in the iron the 845's require. These days, I doubt that you can even get a good pair of OPTs for less than $1,500. I passed them on after I completed my Williamsons which weigh about half as much. I can comfortably lift them and the Heyboer pp output transformers are about $ 500/pair and absolutely state of the art. I cannot tell a sonic difference between these amps and the 845s. The Williamsons are simply wonderful amplifiers.
Thanks for the words of encouragement, Roger! The Heyboer S-265-Q is extremely well done, lacking only the last bit of refinement compared to the originals. But I have the originals and actually prefer the Heyboers, which I use in my amps. They exhibit a bit less ringing and have a punchier midrange and bass. They sound like a lot more than 20wpc.
I think the original poster needs to provide a bit more detail about the sort of amp they want.