Does anyone care to ask an amplifier designer a technical question? My door is open.
Reminds me a bit of one a few years back on the 300SEI. Just look at the frequecy response into a quite easy simulated speaker load!! that’s unacceptable, over 5db variation. no power at 200hz and at 4.5khz, nothing below 50hz and above 10khz, and two peaks at 60hz and 1.5khz https://www.stereophile.com/images/archivesart/cad300fig1.jpg Cheers George |
krelldreamsIf your Alps pot’s passive pre, input to output measures 1.21kohm then you have a 5kohm Alps pot. Your source may well be doing it hard into this 5k load, and making things "leaner". Passives should be at least 10kohm to suit "most" situations. Or higher (>10kohm) if the amp is also >50kohm or more. Cheers George |
ramtubes I think that one comes later for free on line, as I'm such a tight arse, I only read the ones Stereophile drip feeds online for free. But it must be bad to beat the Leben CS300, check out the HF boost because either the output transformers are ringing or the circuit is oscillating. And it's shown in the 1khz square waves as well. To me another one, that should not be passed on final inspection to be sold. https://www.stereophile.com/images/1111Lebfig01.jpg https://www.stereophile.com/images/1111Lebfig02.jpg Cheers George |
ramtubes OP This is great advise for those here, to learn and understand these Stereophile measurements, it’s crucial to giving good informed advise to others, and to selecting the right stuff for even for themselves. As all decent manufactures use these types of measurements to design build and to test their products as well as all the EE laws that go with them. Anyone who doesn’t use or doesn’t believe in them, should be given a very wide berth as they have no idea what they’re talking about. Cheers George |
Hey, do you have a link to the complete review? I got 29 hits for Leben. A lot of mention for a poorly performing amplifier.https://www.stereophile.com/content/leben-cs300-integrated-amplifier-measurements JA does make mention of the ultrasonic resonance, but "maybe" because they're an advertiser, didn't make too big a deal of it. Cheers George |
could you provide a quick list of your favorite (currntly available) tube preamps?I don't know about Roger, but the best bag for buck for me is the Schiit Freya it has everything, it's three preamps in one to suit all "flavours" and it has probably the best mechanical volume control you can get. And Mike Moffat is no design slouch, his designs made Theta audio what it was when it was on top, now it's gone by the wayside just like Rowland Krell ect, when the real designers left or sold out, and the accountants moved in. What Mike has done is given the goods on the inside with the Schiit brand but the outside is low cost utilitarian, so the customer is not paying $KKK's for CNC machined polished chassis, that do nothing for the sound. http://www.schiit.com/products/freya Cheers George |
ramtubes I always post this one up by Nelson Pass, and some here "hate it" when I do, so just for them, here it is again. Quote from Nelson Pass "We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more. Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up. Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control. What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection. And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp." I must state, before all the haters start. The above is correct ( should have been included by Nelson Pass). If a 1:10 or more impedance ratio is met by the source and by passive to the the power amp, and in nearly all cases it is. Save for some a small scattering of high output impedance (>1kohm) tube output sources and low input impedance (<33kohm) poweramps. Cheers George |
ramtubes And when I say "easy simulated speaker load" (linked) it’s made for Sterophile and modeled on the easy to drive Kantor speaker by I believe the man himself Kenneth L. Kantor It’s a pretty poor amp design that can’t stay reasonbly flat in frequency (+ - 2db) into this easy load. Fig.4 Modified Kantor speaker simulator, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.). https://www.stereophile.com/images/archivesart/scan58.jpg Fig.1 Circuit of Ken Kantor loudspeaker simulator, intended to represent a two-way, sealed-box minimonitor with a nominal impedance of 8 ohms. https://www.stereophile.com/images/archivesart/scan55.jpg Cheers George |
I have some old Martin Logan Sequel II’s which when repanelled no longer sounded pleasant with my Plinius Integrated 9100 (100w), they became overly bright and shouty. All ML esl's need amps that can handle the load "below" without becoming tone controls and stay stable doing it. Stereophile tests: "The speaker drops to 3 ohms at 440Hz and to a hair over 2 at 24kHz, from which I infer that puny amplifiers, current-wise, should best be avoided. (Music has considerable energy at 440Hz, though only the occasional high-level cymbal crash will cause copious globs of HF current to be drawn from the amplifier.) MartinLogan claims a phase angle of 45° or less across the range; this graph confirms that to be the case, but the speaker’s ability to shut down the Krell with prolonged pink-noise drive did worry me." https://www.stereophile.com/images/archivesart/99Seqfig01.jpg Cheers George |
Many people believe that SET tube amplifier give more mid range magic than Push pull tube amplifier.The reason for this is because most SET amps act like tone controls. Here is a typical, response graph of a set amp into a very easy Kanton simulated load. It’s the wavy line. Here is the Jadis SE 300B monoblocks. Fig.1 Jadis SE300B, frequency response at 1W into 8 ohms (top at 10kHz) and into simulated speaker load (right channel dashed, 1dB/vertical div.). https://www.stereophile.com/images/396JADFIG1.jpg Note: how much higher the 700hz to 2khz (midrange) is compared to the rest, there’s your midrange emphasis and your tone control response. The straight line is what it does into a fixed 8ohm resistor,, which no speaker is. Cheers George |
What are the symptoms of the supply caps being on the way out and at what general age do they become seriously at risk?Sometimes caps can last a very long time, depending how hot they got how close to the limit the voltage was ect ect. Look for bulging. http://embedonix.com/wp-content/uploads/2015/09/good_bad_ugly_capacitors.jpg Top Leakage http://www.southseascave.com/wp-content/uploads/2014/12/IMG_1820sml.jpg Base leakage http://protectyourpower.com.au/wp-content/uploads/2016/05/Brisbane-Airport-UPS-Call-1.jpg Cheers George |
whitestix I have a friend that used these in his fully glitzed out Supratek Cabernet Dual preamp. http://www.supratek.com.au/uploads/1/2/2/5/122515010/published/corttop2.jpg?1539764225 An he thought the world of them, till I went to hear what he was on about, as soon as I heard it, I said "that euphonics you say your hearing, I’ll show what it is, stop the cd and leave the volume where it is" I sat him down in the listening seat and I gently taped the chassis of the preamp and there was a nice solid loud "donk donk" out of the speakers. Your hearing "microphonics not euphonics" I said to him, then I very gently taped the actual tubes with my finger nail, and it was even louder with added "tinkle" to the "donk donk". Say no more. Cheers George |
That’s interesting information concerning the 6SN7 tube. My power amps use them (NOS 1948 Raytheons) as cathode followers and the 6CG7 as a pair as input tubes.Gain is probably lower there, but just try the finger nail gently flick test to see what happens. You’ll soon know if you have a microphonic, oh sorry, euphonic tube. https://forum.audiogon.com/posts/1661211 I've set a 6sn7 in a preamp up on the oscilloscope and talked at it, and watched my voice being duplicated on the scope as wave forms superimposed on the 1khz test wave, and was quite eyebrow raising just how loud it was compared to the test wave. Cheers George |
almarg Yes Al there are so many that are and owners don’t even know they have them, they think it’s "euphonics" but in fact echo. I test "every tube" not just 6SN7’s that come by me, with a tap of the fingernail and watching the oscilloscope. Or in the listening system turn the volume up to normal and get someone to listen in front of the speaker/s while you flick gently with the finger nail. A "bonk" microphonic, with a "tinkle" can be loose/shaky heater filaments as well. A "runway" bonk (rotating feedback) that just gets louder and louder, a severely microphonic tube have your spare hand on the poweramp power switch. Cheers George |
almargThink I found it. Output impedance of the Mani at 75ohms is fine, but if you have a look (linked) there does look to be 2 x Wima output coupling caps on the Mani 's board, I say by the look of them maybe 0.47uf. These into a 5kohm load of the the passive Alps would give a -3db already at 67hz, and could very well be the leaner sound being heard. https://ibb.co/WsFNvhk Could even be the same with the DacMagic. Cheers George |
Mr. Modjeski seems to endorse passivesYes his amps are loved by passives and with my customers that use them. My power amp is a CJ Evolution 2000 its input impedance is 100k ohms, and input sensitivity is 900 mV to full output. It should also love passives, with that 0.9v input sensitivity. And that 100k input impedance you could of had a 20k Alps passive, not just 5k, A 20k Alps pot would have been fine for just about any source then, which by the way you have not told what you have as the source.?? because if it has high’ish output impedance it won’t be comfortable with that 5kohm Alps pot as it will load down it's output and also create a voltage divider. Cheers George |
krelldreamsWhat would your phono stage be, hopefully I can find it’s output impedance and if it has capacitor coupling and if that’s big enough, to work into a 5kohm Alps pot., if not it will roll off the bass prematurely, "creating a leaner sound" As far as the DacMaigic goes (at<50ohm output impedance) there’s no problem for it to see, your 5kohm Alps pot. But it has an output coupling cap also and with the 5kohm Alps pot that coupling cap has to be at least 5uf in size to be -3db at 10hz if smaller than this it could prematurely roll off the bass also, "creating a leaner sound". Cheers George |
Is the phase shift what they like?Could very well be Roger, that’s why I posted this as the possible explanation. Especially in this case with a 0.47uf Wima coupling cap on the output of the Mani phono which is then loaded with his 5kohm pot to ground, it’s a high pass that’s -3dB @ 67hz, and if it’s 1uf still -3db @ 32hz. The fix: Pot should be 10kohm or even 20kohm and the cap 1uF or more. Mani top https://ibb.co/WsFNvhk Mani bottom https://ibb.co/RyV6Gmt Cheers George |
I find no references to burn in in the 50s 60s 70s.. when did it start?I first heard of it, when the first burn in CD was produced to suck the gullible in so the makers could make some bucks, as they weren't cheap, I think it was Monster that did it to "burn in" their cables The only thing that "may" burn-in with 20hz lf tones, is the roll-surround on speaker drivers, that's more of a softening rather than "burn-in" Cheers George |
Technical question: Do certain electronic components, e.g. capacitors, need to "form" before they operate at their best?It takes electrolytic capacitors no time at all to form (certainly not days or weeks) with the correct polarizing voltage, and if they have zero or don’t have the correct polarizing voltage, it was a bad design. Cheers George |
I've been here since its inception.Does that give you the right to be a self proclaimed forum cop. That's the pot calling the kettle black I notice on this account that Georgehifi isn't being taken to task;Wow, you've really got something up you this morning, must be the bagging Class-D's getting on the other thread, and you keep saying (promoting) your is coming soon and it will fix all the problems with Class-D. |
Did I promote such a thing on that thread?Not on that specific thread, but you have numerous times, what was it that was said???oh yes!!! "LET HIM AMONG US, WHO IS WITHOUT SIN, CAST THE FIRST STONE" Think that was it, I remember reading it somewhere, "How to survive in the Australian outback" or something, correct me if I'm wrong. |
He dignifies the other person by doing that. Thank you RalphReally!!! by saying this about Roger, who is helping others with their questions with this thread. "But here’s the kicker: This thread was put up as a promotional device. You can tell because the manufacturer is talking about his products, often more than once in many of his posts." I think you have that totally "arse about face", marqmike Cheers George |
This is why I advocate the ZERO autoformer,It would be far more creditable of you to advocate the use of a different amp to handle the problem properly, even if it’s not OTL. Instead of this costly band-aid autoformer "fix" all the time, that "enables" an OTL to be used under diminished sonics. Maybe your new venture into Class-D will show another side. |
I have a pair of Acoustat Xs in need of amplification. Can you provider some information?This would be a dangerous amp to own if not made by someone who knows their stuff. I’m sure from what I’ve seen, Roger will be an ideal choice for this if he wants to take it on, as it’s not part of his line, and would be a special build. Who knows maybe it could be part of his future line, as there are many Acoustat X’s out there in need of HV direct drive amps. Not to mention other ESL’s that could sound better if they were converted to take HV direct drive amps. Cheers George |
robertrsThe way is it is made, it’s performance (8ohm) tap into a simulated easy speaker load (black wavy trace) https://www.stereophile.com/content/real-life-measurements-page-2 https://www.stereophile.com/images/1218Cary100fig02.jpg it does becomes a bit of a tone control, varying it’s frequency response up to +/- 4.5db!!! A good amp should be almost flat. This is probably as a result of it’s 4.4ohm!! output resistance, that’s a damping factor of under 2 !!! From the 4 ohm tap, it’s 2.3 ohms!!, still to high in my books. Not good to me, unless you purposely want to change the way a recording is meant to be listened to by the recording engineers, into today's semi demanding speaker loads, it will be fine into very easy to drive speakers, but they usually have their own set of problems Cheers George |
bdp24I too would like a link to this kit, I can't find it anywhere??? Cheers George |
