[Nik]

I hope you understand my english translation of what a techincian told me about the Manley 300B preamp:

“The Manley 300B preamp adopts in the final stage the 300B tubes, direct heat triodes (the filament and cathode are one only thing), this has a good sound characteristics for the simplicity of the mechanic, but produces a noise problem, because the filament at 5V/1,3A transmits the electricity line noise (50Hz and the 100Hz) to the cathode. Any thing you do for silent the filaments do not will have a signal/noise at the same level of a indirect triode heat. This kind of noise if is acceptable with speakers is not with headphones.”

Nicola

 

[Wodgy]

Interesting! I've always wondered about that aspect of direct heated tubes.

 

[Joe Lau]

We have simulair problem on design 2A3 Headphone amps before ! It need a clean DC filament power supply. Very Pure low ripple B+ to get low noise enough for Headphones.

 

[ddriveman]

Hum is worst if the design uses AC for direct heating. Having a choke filter can help. I noticed that with low impedance, high sensitivity cans like Senn PX-200, hum is quite noticeable. But same amp with a high impedance can like Senn HD-600, gives very little hum. Almost not noticeable. I also find that using different 2A3 tubes can give different hum levels. For my Opera Cyber 30, low hum tubes are Sovtek, RCA, GE 2A3 but TJ mesh and Valve Art 2A3 have higher hum.

 

[manleylabs]

Hi Nicola,
You know it is thanks to you that we did go back and look at the noise performance of these Manley 300B Preamplifiers. Two of my guys have been examining all this since last week when you brought this buzz to our attention. As I told you before I did listen to your preamplifier before it left here. I listened on a pair of our 60 ohm 106dB sensitive Sony's we have here which are comparable to what you have. Nothing out of the ordinary stood out at me at the time. If I had had our less sensitive AKG's on, "less than nothing" would have caught my attention.

After you wrote to me complaining about a noise, I pushed the guys to get another preamp on the bench to have a look. That's where we last left off on this thread.

First thing I did was strap on those Sony 'phones and plugged 'em in. Now that I was looking for it, I heard the slight buzz, with a little 120Hz hum lying under it, more apparent when I pushed the cans tight against my head. OK. Let's see this on the scope. Yup there it is. Faint, but there. You were right, Nik.

(But not right about it being only a European problem. We'll hear 120Hz here as our mains run off 60Hz. You would have heard that hum at 100Hz, double your line frequency of 50Hz.)

Now why is it there, what is causing it and who put it there? The first thing we eliminated as the cause was the actual mains transformer. As I told you, we recently changed to a lower flux power tranny to combat mechanical vibration and I was sure it was not the problem. The boys took the power transformer out of the chassis and remoted it away from the audio and the ground planes to eliminate radiated fields infecting things as a cause for the problem.

Next, was it a grounding error? We went through the ground path and played around with all that to eliminate grounding issues as a source for the noise. We cut up the board and moved all the grounds here and there with no change. Grounded the input grids. Noise still there. Grounded the 300B input grid. Noise still there. It's apparently somewhere in the output stage. But where?

Next, focus on the 300B. How is the ripple on the supplies? The B+ has a nifty ripple eliminator and tube regulation. We took out these "extras" as a test just to make sure our cleverness wasn't getting us into trouble. It wasn't. No change playing with those circuits.

OK. That leaves us with the DC filament supply for the 300B. Let's look there. OK, we are running DC supplies already, one per tube, and not AC so we aren't starting off totally stupidly. (Just minorly stupidly.) First look. Why is there ripple left here? There shouldn't be. We have our bridge and our filter caps. What is going on here? For kicks, we took the battery out of the famous Manley War Wagon ('86 Olds station wagon, a real beater...) and made a quick little 5V supply out of it to hook up to the 300B's. Voila. Noise and buzz gone. OK. So what's wrong with our supplies? Yesterday morning (before you started THIS thread, Nik,) Humberto found it. (I had to run off for the day so I didn't get the chance to report this yesterday.)

The existing filter cap arrangement was set up to try to become a big battery. 30,000 uF per tube. But why not filter this directly to ground too? Well, with direct heated tubes, sometimes you cannot. Depending on the grid bias situation. Depending on the cathode side of the equation. Depending on some other things that react with this stuff. The original designer of this part of this circuit chose to go with the "battery" method.

Questioning the "why not" side of things, Humberto added a cap directly to ground from each leg of each tube's DC heater supply (with HF bypass caps for good measure) and the Manley 300B Preamplifier Problem was suddenly solved. And they are big enough caps as to not roll off the frequency response of the 300B. It did change the gain of the tube a little, but it's ok here in this circuit. Here we are lucky it all works together fine. Noise Floor went from -76dB to -86dB (that's noise floor down from 0dBu). That yields Signal to Noise Ratio better than 110dB (depending on what output, what load, what reference, don't have time right now to go through all that...). Now it is quiet. For real.

So Nicola, we have you to thank for making us go through this exercise. We have all learned a new thing or two in researching and solving this problem. The new mods are going into production immediately. Also, we will make available this easy modification to all existing owners of the Manley 300B Preamp. Everyone has you to thank, Nik. Thank You!

(I am cross posting this to the other thread too for clarity to all.)

 

[elnero]

Wow! Now there is a class act if I ever saw one. If only other manufacturers took the time to not only address problems in this manner but to inform the owners in such a detailed and honest manner. I applaud you for your efforts.

Now can we talk about Manley building a headphone amp for the masses...

 

[psyco1]

Wow, I'm impressed.
A lot of companies wouldn't do anything like that.

 

[ServinginEcuador]

Whoever bought Nik's Manley amp just got an early Christmas present in the way of this fix. I bet an email to Manley for the part numbers and values of the stuff changed would yield a very happy new owner of this amp.

 

[Joe Lau]

I think Manley not try to delivery noise amps but they have same problem as me before. I also test with a SoXX 107 db Headphone and a Victxx HP-D31x . It also state very high senstitive. I use them to test Hum and noise reference ! It cause me can not found the problem. I can not heard any hum by Japan Headphone but can heard by HD600 & Grado SR125. I think Manley should buy more cans for Noise/Hum reference.

I have many Cans on hand for testing now. I had
HD600 , Grado SR125 , AKG-K400 , AKG-1000 , a electrostatic , Stax SR sigma(This one for future R&D) , Victor HP-D310. It really need more Cans to test headphone amps to judge which is acceptable. May be I still to buy more Cans for reference. Belive me ! Don't belive on specification ! How many db sensitive ! It has many testing method ! Hearing is beliving to what you heard. It is a paid story on old MG-Head DT/ MG-Head OTL. Some of them is OK ! Some of them is Noise. It is cause by same reason ! Belive on specification of high sensitive Can ! We need to learn more and get more feed back from users and then can improve products. I think OTL mark II don't have noise problem any more.
I hope to heard feed back if it still have problem.
Oh ! Say more ! Don't trust on your equiement ! It only can use as reference. Yes ! All products should pass testing equiement but also should pass listen test by Headphone ! It is no meaing on how many db ? It should compare with same output level and testing condition. Due to it is compare noise with Max output Voltage !

I'm also appreciate Manley service , He is so open and I can learn this technique to modify our products to better. I hope all manufacturer can provide such service.

 

[manleylabs]

Hi Joe,
Thank you for your compliments. (But, I am a SHE...)

Please do not assume that because that day when I listened to Nik's preamp before it went to him I HAPPENED to pick up the Sony 'phones, that we do not have more headphones kicking about. That happened to be the pair Martin was using on his bench that day. Then as it turns out, they had similar published specs to what Nik was using, so it made comparisons make sense as far as what is Nik hearing? OK what are we hearing? The same thing!

We do also have Grado's (Hutch has the second pair Joe ever built.) We also have some 600 ohm AKG's. We test all our mics upstairs on some cool ol' Stax's, and the Sennheisers... we should have them but there was a mixup during the NAMM show... I have been meaning to buy a coupla pair o' those after they loaned 'em to us for NAMM. Got some Etymotics too. I mostly use them on my H-D or while travelling. (I love those!) So yeah, we are into the popular 'phones... the Sony's are the best for listening to noise as they are the most efficient ones of the bunch we have.

We also have a 20dB gain block on each test bench (which drive 0.300V sensitive 50w amps driving 94dB efficient speakers) to really get a huge microscope, as it were, on hearing noise through the bench speaker setups (or through headphones.) When they had the preamp running through that setup, even the deaf could hear the hum!

But listening isn't everything either. There was a spike on the distortion trace off the analizer. But it was very faint. Easy to miss in routine test. But we should have taken better notice of it and explored it... years ago.

When I am working on new designs I do rely on relative measurements, relative to other things we build, relative to our Audio precision machines and Sound Tech machines. Measurements, when understood and qualified are very useful. I didn't take the time to post all the reference levels at what frequency, bandwidth, etc etc etc that one should do when stating measurements but suffice to say, we have a good handle on proper measurement techniques and how to interpret what we see and what that all means to us. (It doesn't mean that we are always and every day on the lookout for a certain problem, though. We're just human just like the rest of youze.)

I then use the overkill extra 20dB gain stage driving both speakers and headphones to search for noise. Then of course you have to keep all things in balance. What do you see? How do you interpret the numbers? What do you hear? And then, is it workable in real life or can we do better?

Case in point was this situation: that preamp was a follow on model based off an older design we had been building since 1996. Because "it had always been that way" since the old regime, and because NOBODY ever complained that the noise floor was unacceptable, it just wasn't a real life problem for us or anybody, except finally, Nik.

But now we know it was... and the exciting challenge was to find the cause and solve it. Constructive criticism helps us always improve. So again, thanks, Nik. And the best to you, Joe.

 

[minya]

Quote:

Originally posted by manleylabs Hi Joe, Thank you for your compliments. (But, I am a SHE...)

Oh, the irony!!!! Manley is a SHE!!!

...

[size=xx-small]*cough*[/size]

Sorry... can't.. help myself... sometimes.

- Chris

 

[evilcthul]

That's Eva Anne Manley though isn't it? Manley is just a last name... In Sydney, there is a suburb called Manly but I digress.

Good work to both of you and Nik for solving the problem. It's great to see the industry addressing end user problems no matter how big or small. Now if only I could afford the Neoclassic...

Eva could you possibly tell us about any future plans (in the headphone realm)? Are there going to be any lower priced offerings?

 

[manleylabs]

Thanks. Well we have a whole pile of future plans. More plans than we ever will have time to build. I can say this: that lurking on this board for the last little while (actually I started watching this board a while ago, before this thread started, when I was researching purchasing those Etymotics) has furthered my interest in catering to headphone users and I'll do my best to work on more things for ya'll... just can't say what or when.

We have a crew of over 40 people building over 65 different products here at this factory. This includes all our Manley brand hifi gear, pro studio gear both Manley and Langevin brands, and we also manufacture George Massenburg's pro studio GML gear here for him as well. Needless to say, our plates are rather full. Here it is past midnight and I have been working about 17 hours today and I am still at the factory typing and not home sleeping. So I can't promise ya'll we'll have some more dedicated headphone products for ya soon or not... but ya never know.

If you have a recording studio and need a clever little headphone mixer, we do build one o' dem already.

Ya'll keep up this good resource here on this forum. Good for the customer, good for the manufacturers. As the recycling slogan here in California goes: "Good for the bottle, good for the can..."

 

[jaskin]

Hi EvaAnna,

I'm sure the Head-Fi community would definately look forward to the introduction of headphone specific products from Manley Labs. I myself was very interested in a Manley Stingray Int. Amp but couldnt' find one used

Cheers
J

 

[Nik]

Good! If one day I’ll go to California I have a work…
I have to thanks EveAnna and all the equip of Manley labs. because they demonstrated a good attention to his clients and even professional humility in recognise his own difficulty. I even thanks to our HeadFi.org because without this public instrument I doubt that any important known factory could be so interested in revealing things. Nobody is perfect, but all we are in perfection’s research, I think. In this particular fact I’m just a very simple listener or better an insatiable headphone listener that hears his ears and feels himself. I’m not a technician and for this reason I prefer my ears to the instruments and scopes… I must to tell for truth that the Manley 300B preamp (not thinking to the problem now solved) has a fine sound especially pleasant for those who like typically tubey sound, relaxing and musical sound. The quality sound improves considerably (especially in bass control, med clarity and hi extension) adopting a selected NOS tube set (like those I had on my unit: Alesa Vaic 300B Reference, Mullard ECC35 1957 black base, Philips Miniwatt GZ34 metal base 1950, but this combination costs around 1400$). I’m especially happy for those have the idea to buy the Manley 300B preamp for headphone use, now these lucky men have the way smoothed. (I paid a little in this adventure because wait two mounts for a toy, spend a lot of money and own the object only for few days is too much!!!). But, as I’m looking for “the absolute best” I know I’m going to these kind of inconvenient, and I continue on my road. If you are happy with a simple source with headphone out socket you have not any problem, but… As I wrote, if I can, I suggest to the Manley: why you do not adopt your Shrimp preamp as a headphone amp? Less expensive, minimalist design and perhaps more indicated for cans. But this is just an idea of a simple headphone listener. Good luck Manley!

AND NOW?

As you know my next (and LAST) step will be the two box Angstrom Research (Italian made) that is a no compromise ultimate headphone amp, this piece is projected to be the very best ever made in headphones amps. I have notice of each steps in this building, as the output transformers that needed 20 days each to be ready, the builder probably caught his hands for the extremely thin metals parts realise. About the signal tubes probably the Sovtek 6C45 goes better than the WE437A, the two triodes are not exactly identical, the Sovtek have more power and is difficult to find a pair of matched WE in very perfect condition, the tube is 1934! Very old! And is possible to have not so perfect “vacuum” inside of glass. The construction of the Angstrom separated power supply is totally dual mono and for this reason the volume knob will be situated on the middle of the front panel. The pot is a extremely hi quality Penny&Giles (double blinded). Capacitors and resistors are of the best quality available. Construction totally hand made, air cabled point by point. And the sound? I know that will be unimaginable because I remember well the first Angstrom I had (that one I sold to Jatinder) and I never experienced in my life that kind of emotion listening through a headphone. Period. I’ll tell you about the Angstrom at the end of May.


Nicola