Author Topic: My Tube Journey (Read 199481 times)

Cjtjader · « **Reply #930 on:** Feb 27, 2017 at 02:05 PM »

Thanks

Regards,

Cal

tony · « **Reply #931 on:** Mar 02, 2017 at 04:33 PM »

832, 829b, 5894 pp amp now playing.....
6rhh2 input voltage amp tube, 6SL7 long tail phase splitter
voltage doubler psu genarating 400v B+ loaded...
90 watt power consumption, psu has high power factor...
still tweaking for the low frequency wobble in one channel...
but already sounds good....

tetablanco · « **Reply #932 on:** Mar 10, 2017 at 12:02 AM »

Quote from: tony on Mar 02, 2017 at 04:33 PM

832, 829b, 5894 pp amp now playing.....
6rhh2 input voltage amp tube, 6SL7 long tail phase splitter
voltage doubler psu genarating 400v B+ loaded...
90 watt power consumption, psu has high power factor...
still tweaking for the low frequency wobble in one channel...
but already sounds good....

My next Master Tony tube amp?

tony · « **Reply #933 on:** Mar 10, 2017 at 07:26 AM »

abangan....

tony · « **Reply #934 on:** Mar 10, 2017 at 08:25 AM »

completed repair on another Antique sounds 1006 SET power amp..

to those interested, this amp is a single ended amp capable of at least 20 watts of output power....power dram from meralco is around 170 watts...

topology of this amp is like these: 6SN7 srpp voltage amp input stage, buffered by a paralleled section 6SN7 cathode follower feeding another 6SN7 active loaded voltage amp that feed the 845 grid, the 845 is fixed bias at around 80mA for an idle dissipation of around 80 watts...

you might be wondering what the 6L6gwb and the 6sl7 tubes are doing there, well, they are a voltage regulators that supplied low impedance power to the 3 6SN7's...the 6L6gwb is the series pass element and the 6sl7 tube is the error amplifier using a zener voltage reference at its cathodes..

in the course of repairing this amps, i found out that there were 3 coupling caps in the signal path, compared to the original published schematics with only two, so i investigated and found out that the second stage cathode follower were converted to cascaded cathode follower to justify a third cap....i have never seen such a practice before and can not see any logic behind it, so i simply restored the amp to its original configuration....done away with one cap and a power resistor...

imho, the 2nd stage 6sn7 cathode followers can be taken out altogether i do not see any compelling reason for putting it there except to say that Antique sounds might have truckloads of 6sn7's....but hey, this is not my amp so i will just let it be...

sorry for the long post....

audiojunkie · « **Reply #935 on:** Mar 10, 2017 at 10:51 AM »

Nice post and amps sir Tony...
I'm thinking that my amp SET GTA SE40 it could have similarity in topology that also using two 6sn7 at input and three 6L6GC or 5881 output, adjustable bias up to 640mV and can output 40w stereo or 80 mono.

tony · « **Reply #936 on:** Mar 10, 2017 at 12:23 PM »

6L6GC or 5881 is far easier to drive than an 845,
for starters gain of 845 is only about 4 while the 6L6gc is around 8.....
to push the grids of the 845 you will need more than 60 volts peak of signal drive, whereas for the 6L6gc you can get by with kjust 20...
needless to say, they are not the same...as drive requirements are
not the same...

Quote from: audiojunkie on Mar 10, 2017 at 10:51 AM

Nice post and amps sir Tony...
I'm thinking that my amp SET GTA SE40 it could have similarity in topology that also using two 6sn7 at input and three 6L6GC or 5881 output, adjustable bias up to 640mV and can output 40w stereo or 80 mono.

audiojunkie · « **Reply #937 on:** Mar 10, 2017 at 01:03 PM »

Quote from: tony on Mar 10, 2017 at 12:23 PM

6L6GC or 5881 is far easier to drive than an 845,
for starters gain of 845 is only about 4 while the 6L6gc is around 8.....
to push the grids of the 845 you will need more than 60 volts peak of signal drive, whereas for the 6L6gc you can get by with kjust 20...
needless to say, they are not the same...as drive requirements are
not the same...

Thanks sir Tony . . sa explanation.. Dagdag kaalaman from tube master....
I read back your previous post, I overlooked to note that the 6L6 and 6sn7 only act as regulator not the power tubes.

tony · « **Reply #938 on:** Mar 10, 2017 at 01:44 PM »

do you have schematics? i am trying to hunt it down, if i see it i can comment more precisely....

tony · « **Reply #939 on:** Mar 10, 2017 at 04:10 PM »

there is much more to learn about tubes than simply pulling them out
and sticking another one in....
tubes are certainly more than that.....a whole lot more....

tube journey rolls along, no end in sight just as yet...

audiojunkie · « **Reply #940 on:** Mar 10, 2017 at 05:27 PM »

Unfortunately, not yet found but still looking ...

Can I post PCB picturre sir Tony?

tony · « **Reply #941 on:** Mar 10, 2017 at 05:44 PM »

yes...

audiojunkie · « **Reply #942 on:** Mar 10, 2017 at 05:58 PM »

PCB layout from online group (highlighted parts to be replaced)

Upgraded board:

Top

Bottom

Thanks for the permission...

tony · « **Reply #943 on:** Mar 10, 2017 at 06:01 PM »

mukhang eto yan...

audiojunkie · « **Reply #944 on:** Mar 10, 2017 at 06:02 PM »

Yan nga po...

tony · « **Reply #945 on:** Mar 10, 2017 at 06:02 PM »

ano nga pala issues?

audiojunkie · « **Reply #946 on:** Mar 10, 2017 at 06:06 PM »

Some parts daw working on or beyond voltage limit

tony · « **Reply #947 on:** Mar 10, 2017 at 06:20 PM »

says who? if parts can not take it they burn out...

audiojunkie · « **Reply #948 on:** Mar 10, 2017 at 06:34 PM »

Quote from: tony on Mar 10, 2017 at 06:20 PM

says who? if parts can not take it they burn out...

Common experienced ng mga owners, the amp will work but evenly will start to show abnormal functions and typical affected parts. So decided to update than fix the problem if something happen atleast I'm assured it's on top condition. Isa pa, can use other tubes.

Stock board before upgrade.

tony · « **Reply #949 on:** Mar 10, 2017 at 07:42 PM »

such is the nature of tubes, tube amps are never bullet proof,
that is why owners need to learn a minimum of maintenance...

as you know, i am not into boutique parts that many audiophiles like,,
to me, if you can not justify as to how and why, then better not do it...

many are stuck on the what of things......

audiojunkie · « **Reply #950 on:** Mar 11, 2017 at 03:08 AM »

That's why I'm trying to learn the bias adjustment without assistance from a tech.

I agree that not all boutique parts cost not always equate to level of improvement if there is.

Back to amp diagram, can I get your opinion and is it possible to use kt66 tube?

tony · « **Reply #951 on:** Mar 11, 2017 at 09:54 AM »

i do not believe that the designers of this amp are that stupid
to put in parts that are not suitable, they must know what they
were doing...
having said this, parts do fail although unintentional,
such is the nature of tube amps...during the production
life cycle of this amp, revisions upon revisions will happen,
all are aimed to improve performance...
and if i were you i will never take what others say about this amp,
what matters most is what your experience is with yours...

Quote from: audiojunkie on Mar 10, 2017 at 06:34 PM

Common experienced ng mga owners, the amp will work but evenly will start to show abnormal functions and typical affected parts. So decided to update than fix the problem if something happen atleast I'm assured it's on top condition. Isa pa, can use other tubes.

Stock board before upgrade.

tony · « **Reply #952 on:** Mar 11, 2017 at 10:08 AM »

the kt66 is the british version of the 6l6GC,
kt or kinkless tetrode, so called was
to circumvent the american patent on beam tetrodes
that the 6L6gc and siblings belong to...
https://en.wikipedia.org/wiki/KT66
so go ahead and use it....

thing about biasing is to get all three tubes at the same cathode currents, when paralleling tubes, it is important to get tubes that
are well matched at the operating point, and bias pots are provided for this purpose....

so how do you bias them?
the plate dissipation for the tube is your limit,
say your tube can do 30 watts, for reasonable tube life,
we do not want to run then at full 30 watts, 80% is a reasonable
target or 24 watts..
then knowing your plate voltage, you can adjust bias to get
your cathode current set...
say your plate voltage is 300 volts, so at 24watts, this means
80ma...
you may also follow recommended factory settings...
as for me, i will not bias the kt66 at more than 60mA cathode current, 40-50 is just fine...

Quote from: audiojunkie on Mar 11, 2017 at 03:08 AM

That's why I'm trying to learn the bias adjustment without assistance from a tech.

I agree that not all boutique parts cost not always equate to level of improvement if there is.

Back to amp diagram, can I get your opinion and is it possible to use kt66 tube?

audiojunkie · « **Reply #953 on:** Mar 11, 2017 at 11:37 AM »

Many thanks sir Tony for your opinions and a very nice explanations on bias setting. From manufacturer recommendation 640mV but from other owners suggested to set at 610-615mV only, don't know it's equivalent in mA.

tony · « **Reply #954 on:** Mar 11, 2017 at 12:36 PM »

lower bias settings means cooler running tubes,
cooler running tubes lasts longer....
higher bias means hotter tubes, and probably better sounding,
but tube life can be shorter....
so you have a choice....

640mv/11 ohms (cathode resistor) = 58 mA just about right imho..
610/11 = 55mA......
not too much of a difference from factory settings..
the thing is to be able to set the bias at a lower setting
without degrading performance or sound quality...

also lower bias settings lowers power output somewhat,
but heck a 2 to 3 watts power difference in not audible,
you will not miss it...

Quote from: audiojunkie on Mar 11, 2017 at 11:37 AM

Many thanks sir Tony for your opinions and a very nice explanations on bias setting. From manufacturer recommendation 640mV but from other owners suggested to set at 610-615mV only, don't know it's equivalent in mA.

audiojunkie · « **Reply #955 on:** Mar 11, 2017 at 12:51 PM »

Thanks ulit sir Tony ... Great infos and saved all these in my notes pad.

tony · « **Reply #956 on:** Mar 11, 2017 at 01:34 PM »

you are most welcome, just ask if you need anything tube audio, clarified...

tony · « **Reply #957 on:** Mar 11, 2017 at 01:36 PM »

i started a thread here to get reactions from international audience.....http://www.diyaudio.com/forums/tubes-valves/304966-yet-another-antique-sounds-1006-845-set.html

tony · « **Reply #958 on:** Mar 12, 2017 at 07:21 AM »

Quote from: audiojunkie on Mar 11, 2017 at 12:51 PM

Thanks ulit sir Tony ... Great infos and saved all these in my notes pad.

if you look at the schematics, each output tubes have an 11 ohm 1% small resistors at the cathodes, these resistors served
two purposes, one. to use a bias monitoring ports, and the other as protection for the amp in case of output tube failure,
these resistors will fail as an open circuit without letting the magic smoke out...

so you see, there are reasons why designers put components in, it would be very helpful to find out why they do it...

tony · « **Reply #959 on:** Mar 15, 2017 at 12:29 PM »

or repairing a pair of ASL AQ-1006, i was paid a quad of 8045's, what do you think?