My parallel stereo single ended triode is now ready :)

[kalee20]

Originally Posted by Gabe001

Incidentally, the el34s are running 465v at plate with a 620 Ohm resistor. Each draws around 54mA. Cathode voltage is almost 34v, so each dissipates 23w. I can't see any signs of distress in the dark

Might be my mistake! 23W is within the max anode dissipation (from memory), so you're OK whatever! Looking at your video, it did look as though the anodes were glowing a very dull red - I grabbed a screenshot:

[G.Castle]

They are JJ valves Peter, it may just be the red printing that gives them that colouration?

[G.Castle]

BTW Gabe, lovely construction! If you have the .asc files, they would be of interest. Have you found a good set of models of the valves for the lib in spice? I never found it to be particularly realistic.

[Gabe001]

Originally Posted by kalee20

Might be my mistake! 23W is within the max anode dissipation (from memory), so you're OK whatever! Looking at your video, it did look as though the anodes were glowing a very dull red - I grabbed a screenshot:

I see what you mean. I think it's the JJ logo. The low video resolution blurs it and gives that impression. A better picture is attached.

According to George from tubelab who torture tested JJs at 32w (max 25w), they're good till about 27w. I was tempted to run them at 27w, I must admit, until common sense prevailed

A quick note about JLCPCB. I had to use 600v caps which are all snap fit. Usually I use the large 500v dual cans, but they weren't suitable in this case as the rectified voltage exceeded 500v. I thought a PCB would be a tidy way of mounting the snap fit capacitors. Kicad was quite easy to learn, using a few YouTube tutorials as guides. The PCBs are simple single and dual layer which made things rather straight forward. Minimum order is 5, so I have 4 spare of each. Total cost including delivery from memory was about £18

Finally a quick note about feedback. This amp does not have global negative feedback, but there is some local feedback around the el34, including the output transformer. In practice it amounts to around 6db. It improves THD and damping factor. I got the idea from the attached write up (see pdf - no viruses!). It's a great read. Page 9 onwards.

Andy, you mentioned low frequency management. LT spice can simulate the frequency response of the various stages for you, which I spent countless hours doing, running a simulation every time I changed a capacitor value to make sure I didn't upset anything. This circuit was quite straightforward. The ones with global negative feedback spanning a few stages can be really tricky. If you limit the bottom end in the latter stages you can cause a LF boost in the front end. I'm sure there is a proper way of doing this, but I struggle with this as you do. Sometimes following established designs saves a lot of time and energy, particularly with circuits using large amounts of feedback spanning 2 or more stages.

[Jez1234]

JJ are a brand I wouldn't touch with a barge pole!

[Gabe001]

Originally Posted by Jez1234

JJ are a brand I wouldn't touch with a barge pole!

In fact I had to return a new el34 valve. It was passing a massive amount of current during warmup, then after about a minute it settled down again. But the damage was done - the 10w 620ohm resistor glowed red and the 2w screen resistor was half cooked. This was the only mishap I had, which wasn't my fault. Watford valves replaced it without issue though.

Which new production valve brsnd do you recommend? I thought JJ had a good reputation

[Gabe001]

Originally Posted by G.Castle

BTW Gabe, lovely construction! If you have the .asc files, they would be of interest. Have you found a good set of models of the valves for the lib in spice? I never found it to be particularly realistic.

Thanks, yes. Pm me your email address and I'll send them over

[kalee20]

Originally Posted by G.Castle

They are JJ valves Peter, it may just be the red printing that gives them that colouration?

It's been answered I see, and you're right Greg!

(Good job they weren't yellow print Mullards, else I might have accused Gabriel of taking them to near melting point!)

[Jez1234]

Originally Posted by Gabe001

In fact I had to return a new el34 valve. It was passing a massive amount of current during warmup, then after about a minute it settled down again. But the damage was done - the 10w 620ohm resistor glowed red and the 2w screen resistor was half cooked. This was the only mishap I had, which wasn't my fault. Watford valves replaced it without issue though.

Which new production valve brsnd do you recommend? I thought JJ had a good reputation

They do have a good reputation but I've no idea why! I had loads of trouble with them when I used to repair lots of guitar amplifiers. The only time I've seen EL34's with the glass actually melted through was with JJ.. and several times. Original Tesla though were very good.

Of new production I find Russian ones to be by far the best. A bit tricky under the present circumstances though. Loads of different brands but they all come from only a couple of factories. New valves branded with various famous names from the past (Mullard, Genelex etc) are all Russian.

NOS Russian valves from the Soviet era are generally excellent and as good as NOS Mullard etc. However often they are not exactly the same as western equivalents and some valves (EL34 is one example) were never made by the Russians until modern times for export.

[Edward Huggins]

WRT Post 12, I was simply using the best words that I could muster to describe a "sound". No attempt at audiophoolery was intended!
WRT to Post 14, whilst my new laptop has Harmon Kardon/Sound and Dolby Atmos as bells and whistles, it is hard to tell the difference. From what I heard the triode offering had more bass weight.

[G.Castle]

Originally Posted by Gabe001

Thanks, yes. Pm me your email address and I'll send them over

Thanks! Will do, it will be interesting.

Originally Posted by Edward Huggins

WRT Post 12, I was simply using the best words that I could muster to describe a "sound". No attempt at audiophoolery was intended!

It's near impossible to convey an impression of sound quality, descriptive nouns are never graduated, except by words like 'very' or 'little', so it's a lost cause unless the writer and his/her readership have both agreed on the terms having listened to samples first! I think Peter made that comment firmly tongue in cheek!

[Jez1234]

I reckon sound can be described reasonably well. For better or for worse it probably requires much time reading hi fi mags and attending hi fi shows etc before a reasonably large proportion of people are reading from the same hymn book on the interpretation of the adjectives. It can all get a bit "wine tasting" ish of course!
It's far more useful than using a mobile phone to record differences!! I thought this was a joke when I first saw it a couple of years ago TBH... people using the tiny mic on a compressed digital audio phone in a room with god knows what acoustics to demonstrate £20,000 hi fi systems on the interweb thingy... yeah right

[G.Castle]

Originally Posted by Jez1234

I reckon sound can be described reasonably well. For better or for worse it probably requires much time reading hi fi mags and attending hi fi shows etc before a reasonably large proportion of people are reading from the same hymn book on the interpretation of the adjectives. It can all get a bit "wine tasting" ish of course!

Quite. Edwards description of his amplifier being evocative of his parents PX 4 equipped HMV conveyed more to me than any description could: but if there ever is an audiophile/muggle translation dictionary ever written I hope that the word Mellifluous has an entry.

Mellifluous the sound of luxurious opulence.

[kalee20]

Originally Posted by G.Castle

It's near impossible to convey an impression of sound quality, descriptive nouns are never graduated, except by words like 'very' or 'little', so it's a lost cause unless the writer and his/her readership have both agreed on the terms having listened to samples first! I think Peter made that comment firmly tongue in cheek!

Well... yes, a light-hearted, yet questioning, response to 'soft, non-forward, mellifluous bass.'

I'm not averse to appropriate imagery for describing sound - 'tinny' comes to mind as a good adjective for a sound peaky in treble but lacking in bass, but I struggled with the 'non-forward' bit - and Greg's elucidation of 'mellifluous' as 'the sound of luxurious opulence' hasn't helped really helped...

Edward observing that the sound is akin to his parents' PX4 radiogram, now, that gives more of a clue - an opulent piece of furniture (rather than an opulent sound!), probably a 10" loudspeaker, in a solidly built enclosure, maybe a bit of bass resonance helping to extend the LF response at the expense of some ringing (the PX4 providing a bit of damping rather than a lot), and HF response drooping above 9kHz - that gives a clue. Add to the slight colouration due to second-harmonic distortion (which isn't unpleasant!) and I can imagine the sound.

Further, I'd know what I had to do if I wanted to recreate it! Quantifying what's being aimed at, does at least give a designer an idea of how to get there.

[David G4EBT]

Getting a bit off topic, but for what it’s worth, the reason ‘mellifluous' is a nice sounding word is that it’s ‘euphonic’ – a word or phrase that, in itself, has a pleasant sound. It’s from Latin mellifluus (“flowing like honey”), from mel (“honey”) + fluō (“flow”). Dulcet (“sweet speech”), from the same root, is an alternative Latinate term with a similar meaning. The sounds in a euphonic word or phrase flow with soft consonant sounds, like “tremulous, floral, euphoria”.

If you were a stranger on a Tube train in London, glanced at the tube map and saw ‘Pimlico’ and Wapping’, which would you think was the nicest place? And if you were in a spaceship about to land on another planet inhabited by two tribes – one friendly and the other one hostile, one called 'Grattax' and the other Melodians, which would you think was the friendly tribe? For some reason, 'sl' words are often unpleasant. ('Sleaze, slime, slug, slut, slag, slap, slop, slither')

(Google 'Phonaesthetics', and Prof David Crystal).

I find it weird that I'm now the same age as old people.

[kalee20]

Thanks for that, David - and 'flowing like honey' could indeed be appropriate!

(The controversial nature of myself would then be decrying the stickiness left behind where honey's flowed, and the flies and wasps - I've recently been using honey as wound treatment. It works well apart from the mess!)

But surely 'mellifluous' is better applied to the music that's played - Jesu Joy of Man's Desiring, by JS Bach, or Goodbye to Love by Karen Carpenter would surely sound mellifluous whatever? Yet even Gabriel's best efforts with EL34 triodes could hardly apply mellifluity to Shostakovich's 10th symphony, or the Sex Pistol's Greatest Hits!*

* if there are any...

[David G4EBT]

A while ago on the forum, I posted a thread about a £13,000 turntable with a veneered plinth. Of interest to audiophiles, at 32 mins, the cabinet maker fits a £5,000 ikeda 345 tonearm, an Audionote 0-10 cartridge, (another £5,000) and a Garrard 301 turntable. Then right at the end of the video, for his outlay of £13k (plus speakers and amp), the customer plays an A-cappella sea shanty. The antonym of 'euphonic' is 'cacophonic' and to my ears, an unaccompanied sea shanty is to cacophony what mellifluous is to euphony!

https://www.youtube.com/watch?v=vKFQ8B4cx64&t=25s

Each to their own.

[Richardgr]

My favourite description of the sound from a great amplifer was an audio review for a Line Magnetic offering, I think it was, where he was describing listening to the test pieces of music. He loved the way it performed (and I paraphrase since I can't find the original) ... 'By now the tears were flowing uncontrollably, as I moved to Diana Krall ...'.

I have to admit when the soundstage is so good I am scared to play some tunes myself!

[Robert Gribnau]

Originally Posted by GrimJosef

...
the circuit shows the output valves with g3 connected internally to the cathode. This is true of many octal based tetrodes and pentodes but, unusually, not of the EL34. Mullard chose to bring g3 out separately on base pin 1, alongside the cathode on pin 8, in that case.
...
GJ

This seems to imply that Mullard designed the EL34. But as far as I know, it was Philips who designed the EL34, and introduced it in 1950 (as the successor of the EL60, which is electrically identical to the EL34, but has a Loctal base).

In the 4654 (the 600 V anode voltage version of the EL5) introduced in 1939, Philips also had g3 come out separately, so it could be used for amateur transmitting purposes. Perhaps Philips had something similar in mind for the EL60/EL34, although the 4654 has its anode come out at the top of the valve, while the EL60/EL34 do not.

[GrimJosef]

Sorry, that was careless of me. I normally try to say Philips/Mullard. Mullard was founded in 1920, was already in partnership with Philips in 1923 and all the Mullard shares were sold to Philips in 1927. I'm not sure where the design work was done for the EL34 but wherever it was geographically it would have been inside Philips corporately.

Cheers,

GJ