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Best tubes for bass?

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ChopperCharles said:
I have a Yaqin MC-100B tube amplifier, and I'm looking to roll some tubes. I'd like to know what the best combination of tubes to use to get really kicking bass.

I've had no problems with bass with either 807s or 6BQ6GTBs. Not so sure how this is a function of tube type. Seems to be more related to having a decent OPT and a good damping factor for the speeks. The former meaning steer well clear of bad OPTs, and the latter by adding enough gNFB to improve damping for bass that isn't sloppy but still packs plenty of "authority".
Miles is right. There is a bit more to this. The Yaqin 100B is a HIFi amp.
Rather than blame tubes, it's the type of circuit + global nfb and the quality of the output tranny determines the bass extenstion and also how good the power supply can hold the B+ up on transients.
As the thd on the Yaqin 100B amp is quoted at 1.5% (I presume at 1Khz) this is mighty high esp in triode operation where I would be looking under 0.5%. and under UL ? (don't enquire).

I may be an old salt at tube amp design...but I'm well and truly stumped. (baffled). In my tube amps I can get thd as low as 0.05% on full load 100W with parallel p-p pairs using a conventional time tested circuit design using standard EI trannies with Sowter, Majestic and so many others. It's painless ! And still today after 60++ years of tube R&D, manufacturers still shove out HiFi push pull amps on the market with massive thd figures.

Back to the question...Judging by my comments above, the type of tube in the o/p stage then becomes insignifigant. It's the upper freq end that tube quality and type becomes noticable.

To the crux...It looks that todays manufacturers haven't really grasped how to design a tube amp or, as correctly mentioned in another thread just to market and to plunder the customer of his/her cash ? I think so.

With this Yaqin amp.....search engine commentary does indicate some user dissatisfaction.....? with one suggesting a rebuild ?

I'm a tube noob, I have no idea what all those TLA (Three Letter Acronyms) mean.

I'm personally quite happy with the amp, I don't have "problems" with bass. I just want more of it. I know it's not a tube amp's specialty, and honestly the levels are probably just about right... but I want these Vegas to shine with alternative and club style music for parties.

Also, all the reviews I've read about the 100B have been positive. Where did you see dissatisfied reviews?

To my ear, I can hear very little difference between the Yaqin MC-100B and my buddy's Rouge Audio Tempest amp. We compared them back to back, and yeah, the $2200 amp was better than my $700 amp... but not by much. Both are very musical amps, even with the stock tubes.

Canuck Audio Mart :: View topic - Yaqin MC-100B
In comes the Yaqin MC-100B. Personal experience tells me that the Chinese gear is of questionable quality and needs a lot of work to sound decent. ...
www.canuckaudiomart.com/forum/viewtopic.php?t=5680 [Found on Google, Yahoo! Search]

Not to put you off..I may have been a bit harsh..

After all these years working with tube amps, it's high time with all the accumulated knowledge around, it seems the performance of these bemoths is going down... and the thd up..there's really no excuse for it.

ChopperCharles said:
my $700 (tube) amp...
I would expect a set of iron for two channels of 100W that provide a good balance between extended bass, good midrange and realistic trebles to cost near that.
How can anyone add in all the hardware/chassis/components/labour/packaging/transport/sales overhead/profit etc and leave enough for good iron.
That's where the bass went. Less iron and copper saves costs in most of those areas
Richwalters, read that post again. Nobody there actually owned a Yaqin MC100B amplifier, they were just speculating and generalizing on Chinese quality.

Don't bash it until you've heard it. Anyone that wants to give my amp a listen is welcome to stop by. I live in Durham, NC. add at gmail.com to my username and you've got my email address.

Just because I'm looking for a different sound doesn't mean there's anything wrong with the current sound. :)

I own a yaqin 100b for more than a year.its a great amp,did you set the bias when you got it? What speakers are you using. i have a tone generator and using a 20hz tone can produce 65watts at 20 hz with no tble and no dropoff, as to weight it is very heavy.I use altec 9846-8A studio monitors. Maybe the amplifier is producing the bass and the speaers too but you don't think its enough? Have other people listen and see what they think.I found the quality of the amplifier to be excellent when I opened it up. Don't worry I was a electonics tech before retirement so i wont electocute myself.
I've found that best tubes for bass are 2SC5200 and 2SA1943. Driven by a proper tube driver they sound gorgeous!

Here is the schemo of the output stage below.

It is class A output stage. Single point input, overload protection, symmetrical and linear, wide bandwidth (I used b-c junctions instead of diodes).


Actually it is made of 2 complementary opamps with open collector outputs loaded on each other, connected as voltage followers. Diodes instead of transistors in differential cascades were used because b-e breakdown voltage is usually very low (I saw only one transistor that had nearly equal b-c and b-e breakdown voltages, but it was a small signal Russian transistor KT208), while output protection needs a breakdown voltage equal to supply voltage otherwise everything will be fried when output shorted. No big deal, since resistance of a feedback loop is very low right transistors in differential pairs could be substituted by diodes.

Interestingly, it sounds "tubey" as people said, probably because of very soft clipping caused by beta droop. The drawback is, resistors in tails has to be selected and their values depend on beta of output transistors. Fortunately, I had then already selected transistors with beta = 100 and CE breakdown voltages = 200. I tried later the same topology for output stages of car amplifiers and used any available suitable transistors selecting tail resistors properly.

Warning: please don't substitute resistors by CCS like in classical opamps because resistors provide an economical class A operations, while CCS will cause need for a quiescent current equal to a peak current, i.e. twice more that means more heat per output watt.

I hope this heretical information helps to convert more orthodox engineers to heretics like me who tend to develop a neat gear using all available components, from tubes to transistors and ICs. No compromises! :smash:
Stereophile helped me out here. I'm now running Electro Harmonix 12AX7's, which reduced the brightness and warmed the amp up significantly, along with Sylvania 6sn7 chrome domes, which really give the amp a rich, full sound and tightens the bass up wonderfully! I really have a beautiful sounding system now. I thought it sounded great with the Chinese tubes, but the sound with my current tubes just blows me away.

I think I'm going to concentrate my money on music now...

As spock would say "interesting". Does anyone know why tubes with the same number(eg 12ax7) would sound different. Is there some standard for the manufactures of tubes. When the chinese make the 12ax7,where did they get the equipment to make it? Did they buy the equipment from the U.S.What are they missing when they manufacture the tube? Any ideas?:confused:
keithgreenhalgh said:
As spock would say "interesting". Does anyone know why tubes with the same number(eg 12ax7) would sound different. Is there some standard for the manufactures of tubes. When the chinese make the 12ax7,where did they get the equipment to make it? Did they buy the equipment from the U.S.What are they missing when they manufacture the tube? Any ideas?:confused:

Tolerances of sizes, I suppose, so parameters are different.
ChopperCharles said:
Well, the insides of the tubes are completely different. You can look and physically see that the Chinese tubes and the reproduction Electro Harmonix tubes aren't constructed anything alike.


Yes, they are different. But your original question was about bass so I proposed to eliminate an output tranny and get better bass like I did when needed to fix a guitar amp ASAP when no output transformer was available at all, so I implemented a hybrid output stage. As the result, the amp sounded superb with bass guitar as well.

As you have found satisfaction, I should not comment further. But matters are a little confusing. A 12AX7 (ECC83) is a 12AX7, unless the manufacturer went very wild with his designations. When you say that the internal construction is "not anything alike", I begin to wonder; what exactly did you have? It would be most interesting to have close-up photos, but that might be impractical for you.

I am not going to open a hornet's nest about tubes of the same designation sounding different; just to say that in any half-decent design and with proper tubes, that will not happen. (By proper tubes I mean differing by no more than +/- 10% from the published characteristics.) I have seen the Russians being pretty liberal with their designations, e.g. using exactly the same innards for a KT66 and a 6L6 - but the former is twice the cost.

But I am glad that you seem to have solved your problem.
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