Topic: AMX Tube Products

[Garp]

vrion,

if you have a so-so source, you will have so-so output regardless of the topology. but, i would say that more of the so-so-ness will be revealed by the Class A amps.

in short, bad source = bad output.

however, a good source on a Class AB might have less detail, some may not be audible (extremely good circuit) but will be measureable when compared to a Class A circuit. do we hear measurements? some people actually do. you might.

i suggest you go make a comparison, let's say a 2A3 amp (naturally revealing) and any push pull amp. forget the POWER for the meantime, and don't use monitor audio speakers. they're not good for tubes, because their impedance over the frequency range is wild. i'll choose  Spendor S3/5 as a reference.Maybe Andrew over simplified, but what you posted is not entirely the whole story, as i have previously posted. in addition, the "division" you mentioned is technically known as phase-splitting. there are many differences in phase splitter designs. Phase splitting is mandatory in Class AB.

Arnoldc,
Unfortunately most of us are stuck with moderately sensitive speakers with minimal impedances of about 3-4. I think its already a given that SET yields the best sound but if we match a low powered SET with power hungry speakers, wouldn't the result be worse than pairing the same speakers with tube PP design, (assuming the PP can cope better with the speaker's requirements than the SET)?

[iceman90a]

but if we match a low powered SET with power hungry speakers, wouldn't the result be worse than pairing the same speakers with tube PP design, (assuming the PP can cope better with the speaker's requirements than the SET)?

we once tried dynaudio speakers on Superman's 2a3 and it sounded like a cheap transistor radio   needless to say that took all of 10 seconds listening before we stopped  

[john5479]

we once tried dynaudio speakers on Superman's 2a3 and it sounded like a cheap transistor radio   needless to say that took all of 10 seconds listening before we stopped  

In contrast I read in a review that the dynaudio audience 42 sounded good on a scott 299 push pull el84 based amp.

[iceman90a]

In contrast I read in a review that the dynaudio audience 42 sounded good on a scott 299 push pull el84 based amp.

Yup - we also tried a Scott299d with my Audience 52 at Hyperaudio's place: Magic!

[akyatbundok]

nakupo nalito na naman ako... 6550 SE vs. EL34 PP/PSE ?

i'm just assuming 2 EL34 tubes per channel would cost about the same as a single 6550 tube per channel, which is as much as i could spend on an amp right now... can't say i could completely disregard my speaker, i already spent for it so might as well consider it's power requirements when choosing the amp... hmmm if only master andrew has an EL34 PP on display we could easily compare it.

[arnoldc]

Arnoldc,
Unfortunately most of us are stuck with moderately sensitive speakers with minimal impedances of about 3-4. I think its already a given that SET yields the best sound but if we match a low powered SET with power hungry speakers, wouldn't the result be worse than pairing the same speakers with tube PP design, (assuming the PP can cope better with the speaker's requirements than the SET)?

i am not evangelizing on a topology. i was responding to the question posted here. SET is NOT for everyone, just like tubes is NOT for everyone.

[arnoldc]

does this mean that being push-pull or class AB, st70's don't sound as good as SET's ?

to me, yes. but it does not mean the ST-70 or any push pull amp is not good. FWIW, i have owned an Anthem Amp 1 40wpc ultralinear push pull.

6550 SE it is!  

the 6550 has a maximum plate dissipation of 35 watts, and in Class A (single ended) that means, with a theoretical maximum of 50% efficiency, you will get 17.5 watts with more than 15% total harmonic distortion.

the 6550-A has a maximum plate dissipation of 42 watts and can yield, in Class A (again, single ended) 12.5 watts at 7% total harmonic distortion or about 20 watts at 13.5% total harmonic distortion. of course, if you like less distortion, you have to go lower wattage.

a typical Class A operation is generally accepted (debatable) to be 25% of plate dissipation, to get acceptable (highly subjective) distortion figures, in single-ended terms.

i thought you ought to know, and for the benefit of the others too.

i apologize if this is not of help to you.

[arnoldc]

we once tried dynaudio speakers on Superman's 2a3 and it sounded like a cheap transistor radio   needless to say that took all of 10 seconds listening before we stopped  

the cone will not even move  

that is expected, if you tell me it sings, i won't believe it.  i had the 52 partnered with a Yamaha with all its 100++ power and the sound was lifeless and boring to me. oh yes, it took me over 20 seconds to give the Yamaha a chance.

that same 2A3 amplifier, which i also own, sings with an 89dB Infinity Kappa 200, 88dB JBL Ti2K, 90dB JBL LX2002, and 84dB Spendor S3/5.

as i said, many times, it is about matching. SET requires high efficiency speakers, with stable impedance load. impedance load coming off more important, than high efficiency, but both are mandatory for SET. so obviously, i'm also not done as far as speakers are concerned. but i do have a good compromise. matching.

FWIW, the Audience 52 SE has an impedance of 3.4 ohms - 19.3 ohms from 20Hz to 200Hz, and 3.4 ohms to 6.7 ohms from 200 Hz to 20 kHz.

[akyatbundok]

the 6550 has a maximum plate dissipation of 35 watts, and in Class A (single ended) that means, with a theoretical maximum of 50% efficiency, you will get 17.5 watts with more than 15% total harmonic distortion.

the 6550-A has a maximum plate dissipation of 42 watts and can yield, in Class A (again, single ended) 12.5 watts at 7% total harmonic distortion or about 20 watts at 13.5% total harmonic distortion. of course, if you like less distortion, you have to go lower wattage.

a typical Class A operation is generally accepted (debatable) to be 25% of plate dissipation, to get acceptable (highly subjective) distortion figures, in single-ended terms.

yikes, those THD figures are kinda scary... how about other tubes like EL34, KT88, 2A3 and 300B, do they also exhibit THD like those?  or is it that in the tube world different standards exist, so THD doesn't have to have so many zeroes (like 0.005%)... jolida is claiming less than 1% distortion on their class AB amps... very interesting, i wonder what tube will give the best compromise between sound quality & power in a single-ended circuit... any suggestions?  i read that kt90's can be a replacement for 6550's if you desire more power.

[arnoldc]

yikes, those THD figures are kinda scary...

not if you don't hear them. they certainly looks nasty on a distortion meter.

how about other tubes like EL34, KT88, 2A3 and 300B, do they also exhibit THD like those?

if you push them, yes. for example, an EL34 in Class A single-ended PENTODE pushed to 8 watts will have 10% total harmonic distortion for. in single-ended TRIODE configuration around 6 watts with 8% total harmonic distortion.

or is it that in the tube world different standards exist, so THD doesn't have to have so many zeroes (like 0.005%)...

since tubes handle distortion better than solid state, yes there are different "personal" standards.

jolida is claiming less than 1% distortion on their class AB amps... very interesting,

when done right, yes. for example, a KT88 in Class AB1 push-pull triode strapped can give you something like 17 watts at 1.5% total harmonic distortion. a good EL34 design can achieve around 25-30 watts in Class AB1 ultralinear push-pull with about 0.8 - 1.5% total harmonic distortion.

i wonder what tube will give the best compromise between sound quality & power in a single-ended circuit... any suggestions?  i read that kt90's can be a replacement for 6550's if you desire more power.

just don't push the tube to its limit, and you can get very decent THD figures. because any tube, when pushed hard will have high THD.

[akyatbundok]

thanks sir arnoldc, i think the THD figures probably won't matter too much with my current setup & listening requirements... i compared geko's 6550 SE to my accuphase amp which has "guaranteed" 0.02% THD from 0.25W to 130W, and they sort of come out equal as far as detail & resolution as long as i don't push the volume past 2 o'clock... i suspect my source is the weak link (universal DVD/CD/SACD player), since i've heard better cd playback on other players.

[H a n $]

Akyat,

Magulo pala yan design hehehe basta da best ang sound panalo na yan what more kung affordable pa!!


Garp,

Agree with you sir kaya nga i bought a customized AMX EL34 60watts tube amp to match my power hungry MOnitor Audio speaker eh..  SET sound great but with the type of music and speaker i have naku di pwede.. preference talaga..  

[H a n $]

Akyat,

... hmmm if only master andrew has an EL34 PP on display we could easily compare it.

Pre wait lang balita ko meron project AMX for 89 to 91db with 4 to 6 ohm speaker.

[arnoldc]

kung saan ka masaya, kung saan ka satisfied, duon ka.

i presented these things para at least alam nyo. may nag sabi kasi sa akin noon na parang niloko sya with regards to tubes. maraming di sya alam, binenta lang sa kanya, binili naman nya.

after this, informed decision man o hindi ang gawin nyo, at least sinabi ko sa inyo. para walang lihim regarding tubes.

[akyatbundok]

kung saan ka masaya, kung saan ka satisfied, duon ka.

i presented these things para at least alam nyo. may nag sabi kasi sa akin noon na parang niloko sya with regards to tubes. maraming di sya alam, binenta lang sa kanya, binili naman nya.

after this, informed decision man o hindi ang gawin nyo, at least sinabi ko sa inyo. para walang lihim regarding tubes.

ummm... clarify ko lang sir, yung nabili na tube amp at parang niloko yun buyer,

di naman siguro AMX tube amp yan tinutukoy niyo?

[arnoldc]

hindi local experience yang sinabi ko sa iyo

[akyatbundok]

ah ok thanks!

so eto natutunan ko so far:

- best sound fidelity can be achieved in a single-ended circuit used below the clipping point.

- but the tradeoff is you need tube-friendly speakers which have a stable impedance, not necessarily high sensitivity.

- if your speaker isn't that, either change the speaker or change the amp... if you choose the latter, you will need higher power output, which can be achieved with parrallel single-ended or push-pull, with a little compromise in fidelity.

- you may or may not notice the compromise in fidelity.

question: how will we know if a speaker is tube-friendly?  is there a test track that we can use, say a frequency sweep, to check if our speaker can be driven by the amp?

[arnoldc]

question: how will we know if a speaker is tube-friendly?  is there a test track that we can use, say a frequency sweep, to check if our speaker can be driven by the amp?

this issue is only magnified when using SET. you can look at the manufacturer's impedance across the frequency range, but not all manufacturers publish them (for example, my Infinity Kappa does not have any, i was just lucky).

I think this SPEAKER TIPS for NON-AUDIOPHILES article would be helpful.

Pentodes, Triodes & "Fake" triodes is a good read to find out why an EL34 is better than other Pentodes.

And finally, Suggested speakers for low power triodes.

[akyatbundok]

wow... i never knew that the fabled zen triode amp used el84 tubes, and now they have a el34 version... come to think of it, just last month i didn't know the difference between a 2A3 to a 300B, a 6550 to a KT88, and a el34 to a el84... well, i probably still dont, except that they have different cost & wattage, and that interestingly cost & wattage aren't proportional.

the schematics of the SE84B and SE84C are available for download... anybody tried yet?  the site claims it's stable to 2 ohm loads, can it be that it may not be too picky with speakers.

[arnoldc]

akyatbundok,

do you want to make one? you have 5K to spare? of course this is a prototype.

[arapaap]

kung saan ka masaya, kung saan ka satisfied, duon ka.

i presented these things para at least alam nyo. may nag sabi kasi sa akin noon na parang niloko sya with regards to tubes. maraming di sya alam, binenta lang sa kanya, binili naman nya.

after this, informed decision man o hindi ang gawin nyo, at least sinabi ko sa inyo. para walang lihim regarding tubes.

thank you and looking forward to generous advises like this one.  

btw, on el84 amp (zen) - isn't that too much effort for little accomplishment (in terms of matching flexibility)? but as they say, the first watt matters most.

[akyatbundok]

akyatbundok,

do you want to make one? you have 5K to spare? of course this is a prototype.

really?!  a zen clone for 5k?!  hehe... isip isip... sir arnoldc, will i be able to know if the estimated 4-5watts can drive my speakers?  more options is making me more confused but as a first ever tube amp i'm now leaning towards the more affordable single-ended... hmmm i didn't notice, are the schematics just for the prototype only.

guys kelan ba natin makikita the much awaited kt88 pp?

[arnoldc]

akyatbundok, no the schematics are not for prototype, but the 5K budget is for prototype of course when you go for a real chassis it would jack up the price. a Hammond chassis will already cost you around 2K additional.

the offer is for you to be able to appreciate how a tube circuit works, the fun and fulfillment of making your own based on a proven design not for commercial intent.

if you'll be attending the tube 101 session, we can iron this out.

[john5479]

I'm also keen on building the zen amp, starting with the basic circuit and if it sounds good, might opt to do the tweaks i've read. sir arnoldc you have the parts available or parts list? thanks!

[arnoldc]

akyatbundok, sorry. EL84 nga pala yung Zen, hindi EL34.

john, all parts can be readily purchased locally.

let me issue a disclaimer: this amp will do 2W at most (in triode-strapped mode).

arapaap, yes. hence, the disclaimer.

in all fairness to this thread, i think we should open up a new one like the gainclone thread. but please, don't call it a zenclone make it more generic, like "building a tube amp" or something like that. baka mas ok kung sa wiredstate na lang buksan, mas appropriate.

[john5479]

thanks for the schema sir arnoldc.

I'm still waiting for my amp to be finished, after that with some time in my hand i might try out this design as my first diy amp. Is it possible to adapt this design using 2 el84s in parallel per channel and tube rectified?

*sigh* malapit na ang 15 target date na matatapos yung monoblocks ko, buhatan at puyatan na naman ito hehe

[H a n $]

John,

Congrats in advance sa new toy mo sir..

[geko]

thanks for the schema sir arnoldc.
*sigh* malapit na ang 15 target date na matatapos yung monoblocks ko, buhatan at puyatan na naman ito hehe

4 days & counting...  heheheh.  lapit na, bro!   excited na rin ako!

btw, i will be on leave the whole of next week.  pwedeng-pwede akong makigulo sa 'yo...  heheheh.  

[john5479]

hope thats not a permanent leave hehe. sana matapos yung amp by 15 nang mastress test next project a flea powed single ended amp OT me new speaker na ginawa c anthony, 96 dB sens. and 16 Hz - 22Hz ang range according to him. 5 feet ang height.

[H a n $]

John,

Pwede maki-join sa gulo?? hehehe