[Makiah S]

So you only upgraded the coupling caps?

More gains to be had with upgrade of the cathode caps.

What are the difference that upgrading each introduces? Just to recap ;3

 

[Maxx134]

What are the difference that upgrading each introduces? Just to recap ;3

Since the Coupling cap is in between and "couples" the two stages (driver to power stage) then it is unavoildable that it is "in the middle" ...

So it is usually the bottleneck or most sonically affecting part of the amp overall,
Involving every aspect and signature of the amp,
So it is most critical...

The higher the cap voltage rating,
The better for "transients" and lower capacitor "ESR" value, wich equates to better response time.
Anything 600v or more here is excellent.
As for capacitance, any value .33uf - .47uf is excellent.

******


Cathode cap increase output and all else cathode caps do, like increased gain, lower output impedance, but also add some nonlinearity.
This is done by stabilizing the voltage drop there.
It is usually minimally applied (for cost cutting and other reasons).

But for the output stage, increasing this cap to a larger value provides greatly needed benifit here with this tiny PSU,
by holding the cathode voltage constant, in relation to current demands, so the bias (in relation to the Cathode volt drop) is not dynamically changed by the music.
So the tube is kept at optimal gain.

So under more heavy dynamic loads, with its increased reserve capacity, it will not weaken so will sound stronger for more sustained power when needed like bass impacts and transients.

Unfortunately there is still sonic changes to be improved here as electrolytics are not sonically perfect, and thus have an indirect impact to sound im upper frequencies.

This is why many instances the cathode cap is paralleled with a smaller film cap for the higher frequencies.

I recommend the "Audio Note KAISEI" electrolytics,
As they supposed to be the best or closest to the legendary "blackgate" caps, which were highly regarded but not made anymore.

Then I use a paralleled bypass cap for the electrolytic,
A film cap of the exact same type/model/sonic signature cap as the coupling cap,
at an arbitrary low value anywhere from .047uf - .1uf max,
( from my experience with this amp and my bigger amp.)
To help the electrolytics with the upper end spectrum.

This is all only my suggestion, as there are obviously other opinions,
So hope this general info help clarify things.

 

[Maxx134]

6F6GT Great tube, good in all departments, good soundstage, forward presence
6BG6GA Same as 6F6 but more soundstage.

I have just compared my best tubes for this amp (the russian tubes) with the 6BG6G (not the smaller narrow 6BG6GA) mm..
I have come to the exact same conclusion!

Really all except the 6V6 were all enjoyable listening experiences, differences were not great but
I do think the 6BG6's are something special, certainly the best tubes I have come across

I must now agree this tube has just "dethroned" my best Russian tubes(!),
As they have the same level of liveliness, with slightly more depth and Soundstage,
Without sounding duller in the process which all the past larger sounding tubes did in comparison.

I am not sure which tube brand you have,
But after looking at the internals,
Amd based on my (weak ) experience,
I would go for the RCA triple Mica first,
Then the NU
Then the Tung-sol.
The newer RCA seem as the rest of them.

Who knows if they all sound as good, but the RCA & Acturus I have definitely sound above all the past powertubes I tried on this amp.
I do have a tung-sol trying next.
*Edit*
Yes the Tung-sol is tied with the pre1950 RCA (triple mica)
Those are the best although Haven't tried the NU or Ken-rad yet.

So Basically you just can't go wrong with any these old 6BG6G tubes...
They big yet gorgeous sound for this amp,
With similar strong output as the other best.

This is excellent news.
I didn't think it could get better in tube selection.

If you have ordered adaptors for the 6BG6 "G"s then I hope you have ordered them with longer external wires than normal.
The ones I got initially were only suitable for 6BG6 "GA"s. The ones I have on order now are 20mm

Yes mine have just enough length thanks.

Oh, and as for the Dumont 6Q5G,
One died upon turn on so they were a bust.

 

[CZ4A]

Oh, and as for the Dumont 6Q5G,
One died upon turn on so they were a bust.

6Q5 is listed as a Thyratron tube, not a pentode or kinkless tetrode. I don't think they would have worked anyways- a quick Googling shows thyratrons aren't suitable for amplification, being more of a switch. Unfortunately, they appear to have little use in modern tube circuits.

Cathode cap increase output and all else cathode caps do, like increased gain, lower output impedance, but also add some nonlinearity.
This is done by stabilizing the voltage drop there.
It is usually minimally applied (for cost cutting and other reasons).

But for the output stage, increasing this cap to a larger value provides greatly needed benifit here with this tiny PSU,
by holding the cathode voltage constant, in relation to current demands, so the bias (in relation to the Cathode volt drop) is not dynamically changed by the music.
So the tube is kept at optimal gain.

So under more heavy dynamic loads, with its increased reserve capacity, it will not weaken so will sound stronger for more sustained power when needed like bass impacts and transients.

Unfortunately there is still sonic changes to be improved here as electrolytics are not sonically perfect, and thus have an indirect impact to sound im upper frequencies.

This is why many instances the cathode cap is paralleled with a smaller film cap for the higher frequencies.

I recommend the "Audio Note KAISEI" electrolytics,
As they supposed to be the best or closest to the legendary "blackgate" caps, which were highly regarded but not made anymore.

Then I use a paralleled bypass cap for the electrolytic,
A film cap of the exact same type/model/sonic signature cap as the coupling cap,
at an arbitrary low value anywhere from .047uf - .1uf max,
( from my experience with this amp and my bigger amp.)
To help the electrolytics with the upper end spectrum.

This is all only my suggestion, as there are obviously other opinions,
So hope this general info help clarify things.

To throw in my two cents for the cathode bypass cap, aluminum polymer caps are also worth a look and are what I'm using now. Polymer caps have very low ESR, high ripple current ratings, and excellent temperature and life ratings. The Sanyo OS-CON (which I think are made by Panasonic now) have been used in tube circuits with good results on other websites. I'm enjoying how my amp sounds now with the Wurth polymer caps- very quiet and even more detailed than before. Of course, you can also bypass the polymer caps with film caps if you so desire.

 

[Makiah S]

oooooh No I can't be hearing about BETTER tubes!!! I just got the Russians! NO MORE I say NO MORE lol, I'm upgrading first THEN going back and rolling MORE tubes xD

 

[DavidK35]

I have just compared my best tubes for this amp (the russian tubes) with the 6BG6G (not the smaller narrow 6BG6GA) mm..
I have come to the exact same conclusion!


I must now agree this tube has just "dethroned" my best Russian tubes(!),
As they have the same level of liveliness, with slightly more depth and Soundstage,
Without sounding duller in the process which all the past larger sounding tubes did in comparison.

I am not sure which tube brand you have,
But after looking at the internals,
Amd based on my (weak ) experience,
I would go for the RCA triple Mica first,
Then the NU
Then the Tung-sol.
The newer RCA seem as the rest of them.

Who knows if they all sound as good, but the RCA & Acturus I have definitely sound above all the past powertubes I tried on this amp.
I do have a tung-sol trying next.
*Edit*
Yes the Tung-sol is tied with the pre1950 RCA (triple mica)
Those are the best although Haven't tried the NU or Ken-rad yet.

So Basically you just can't go wrong with any these old 6BG6G tubes...
They big yet gorgeous sound for this amp,
With similar strong output as the other best.

This is excellent news.
I didn't think it could get better in tube selection.





Yes mine have just enough length thanks.



Oh, and as for the Dumont 6Q5G,
One died upon turn on so they were a bust.

I am glad you like them, I knew you would, LOL.
What this hobby/pastime is all about, enjoying better & better sound.
I have the RCA NOS tubes atm, will be getting some more but may be different brands, dont know until they arrive.
Mine are twin mica only.

 

[baronbeehive]

******

Cathode cap increase output and all else cathode caps do, like increased gain,

.....

Yes, there is definitely an increased perception of gain in output, the 3.5W is now more than enough power.

.....

So under more heavy dynamic loads, with its increased reserve capacity, it will not weaken so will sound stronger for more sustained power when needed like bass impacts and transients.

Yes, this explains the powerful bass response now, no need of a woofer in my system, (or a pre as far as I can see), and also explains the increased dynamics which, as I said before suddenly began to almost knock me off my chair with surprise after the mods, the transients now are crystal clear and powerful giving a most realistic sense of being at a live performance. Before the mods, the amp was extremely pleasant to listen to but didn't have quite the fullness of tone or the ability to handle sudden changes in dynamics that it does now.

....

Unfortunately there is still sonic changes to be improved here as electrolytics are not sonically perfect, and thus have an indirect impact to sound im upper frequencies.

This is why many instances the cathode cap is paralleled with a smaller film cap for the higher frequencies.

I recommend the "Audio Note KAISEI" electrolytics,
As they supposed to be the best or closest to the legendary "blackgate" caps, which were highly regarded but not made anymore.

Then I use a paralleled bypass cap for the electrolytic,
A film cap of the exact same type/model/sonic signature cap as the coupling cap,
at an arbitrary low value anywhere from .047uf - .1uf max,
( from my experience with this amp and my bigger amp.)
To help the electrolytics with the upper end spectrum.

This is all only my suggestion, as there are obviously other opinions,
So hope this general info help clarify things.

You are quite right again, and all the research that went into this on another thread obviously paid off. As I said previously, the bypass caps were necessary to put back the treble response which was somewhat lacking with the bigger Kaisei caps in place. I thought that just using the Kaisei's would be enough but I now believe that anyone using such large capacitance caps will need to complement them with the appropriate bypass caps as well. I've used Audyn copper foil polypropelene bypasses for the Kaisei caps, and the Jupiter copper foil wax and paper coupling caps, therefore the bypass caps are the same type but not the same model as the coupling caps but I couldn't be happier with the sound frankly.

Well I wonder then that since you have a different amp to the rest of us, that might be the reason the 12SL's work better for you?.
Previous experience with other amps I have found the 7/14 loctals perform better than the 6/12SL's. All the 14's have metal bases
so do not know if this is a factor. Mostly I have read that the metal based 6SL/N7 tubes are highly sought after.14/7 adaptors are inexpensive & the tubes will only set you back $7 or $8 a piece.
Just burning in my nos 14AF7 atm & waiting on the new adaptors for the 6BG6G's. The 6211 (12AT7 type) IMO is a totally underated/ignored tube
and deserves more respect (you can get GE 5 star 6211A's for $3 a piece). I did extensive tests over a long period of time in the past & these tubes outperformed all other 12AT7 types.
Of course we all like different types of sound but this one stood out for me personally.

Yes, quite right, they will be different on this amp, also the combination of power/driver tubes will affect it as well obviously. My experience of headphone amps is that the treble will sound clearer because there is not the bass impact that you get on speaker amps, so the treble is allowed to come through clearly so therefore any treble might sound more accentuated with a treble heavy tube.

Edit:
Incidently, I don't know if others have noticed but I think I experienced a difference in sound between a TS5751 with a "D" getter and one with an "O" getter, although I haven't gone into this, so tube construction is a factor.

 

[Makiah S]

So how would we introduce or solder in a smaller film cap in parallel bigger Kaisei's

 

[baronbeehive]

I have just compared my best tubes for this amp (the russian tubes) with the 6BG6G (not the smaller narrow 6BG6GA) mm..
I have come to the exact same conclusion!


I must now agree this tube has just "dethroned" my best Russian tubes(!),
......

Maxx.you're slipping..... I thought you had already tried every tube lol !!

.

 

[Maxx134]

I am glad you like them, I knew you would, LOL.
What this hobby/pastime is all about, enjoying better & better sound.
I have the RCA NOS tubes atm, will be getting some more but may be different brands, dont know until they arrive.
Mine are twin mica only.

Usually I don't have any opinions about RCA as they were always a normal bit unexceptionable tube in other types...
But the older (1940s) triple mica 6BG6G RCA has the best internal structure of all of them and is different than the newer (1950s) RCA.
They perform on par with the Tung-Sol, which to me sound the best out of the 3 names I have in that type.
It was no surprise the Tung-Sol would be up there as one of best, but the old RCA is so impressive for RCA.
Also, I do not expect the NU to surpass either of those two,
But it looks really nice inside at bottom so I may get one to try.
I don't like how the Tung-Sol has a getter at the side of tube and like how the old RCA has double getters at the bottom and two contacts going to its top instead of one.
All other 6BG6G tubes have only one wire going up to top...

Edit:
Also these tubes look very tall and intimidating with the adapters and top connectors.

 

[Maxx134]

I should add that the differences between the various 6BG6G tubes that I tried ,
were the most uniform & minor , or smallest variation I have seen.
I would say the sonic differences are quite even and probably less than 5% sonic differences.

 

[baronbeehive]

So how would we introduce or solder in a smaller film cap in parallel bigger Kaisei's

You connect them as follows: negative to negative, positive to positive.........obviously.

Usually I don't have any opinions about RCA as they were always a normal bit unexceptionable tube in other types...
But the older (1940s) triple mica 6BG6G RCA has the best internal structure of all of them and is different than the newer (1950s) RCA.
They perform on par with the Tung-Sol, which to me sound the best out of the 3 names I have in that type.
It was no surprise the Tung-Sol would be up there as one of best, but the old RCA is so impressive for RCA.
......

Its seems I'm the only one that likes RCA's.
Although they may be slightly lacking, I find the musical balance to be perfect on the 6SN7's for example.

 

[Maxx134]

Yeah well for our other larger amp,
the RCA had nice thickness,
But for this 6BG6G, they are top of the heap in construction, and I still haven't fully decided which I find better yet ,as its so close.

Also, the Russian tubes are still great,
just not as dimensional.

 

[baronbeehive]

My setup is Bifrost 4490 + APPJPA1502a(with Jantzen Superior Z-cap)+HD600. The only power tube I have is JJ 6v6s. Initially I tried 12AT7 mullard, JJ 12au7 and 12au7 RCA clear top and was not happy. Thanks to @Maxx and @baronbeehive suggestions, I purchased GE 12SL7(silver round plate) , Tungsol 12SL7, Tungsol 5751(vintage) and JJ 12AX7. With my setup, IMO the GE 12SL7 treble sounds just a tiny bit harsh(probably due to HD600s sound signature), however the Tungsol 12SL7 is perfect, followed by Tungsol 5751. Also as @baronbeehive said the JJ12ax7(still burning in) sounds fantastic with this setup.

......

In essence I found my expectation bias was totally contradicted by the unexpected results.
After all tubes were burnt in I found the best driver to be the little 6211A. It pretty much wiped the floor
with the 12SL7 and although the 12SN7 performed better, the treble was distinctly inferior. Words that came to
mind at the time were splashy/tizzy/smudgy sss's sibilant. ............

Just tried the GE12SL7 silver round plates, to see if indeed they do sound a tad harsh in the treble as some have said, or whether they sound more realistic on my system....

Now that I've had initial listening impressions I completely agree with the above 2 posts regarding the 12SL7 GE, but not the Tungsol, the sibilance is especially prominent because I haven't heard that on this amp before, so again I'm back with my TS5751, I don't think it can be beaten!

Just out of interest when the Miniwatt, or speaker APPJ came out several people posted about a diode mod and a pot mod but I haven't been able to find out anyone who can tell what was the effect of these mods. Just to be clear I'm not thinking of doing any more mods but I just thought I would throw this open to discussion to see what other members thought. I have no idea what a diode mod would do, and even if the pot could be changed there would not be room inside for it probably, but if the stock pot is suspect, and I don't think it is, a stepped attenuator would bump up the sound another notch. I'm sure it could easily be checked to see how well the 2 channels are matched but I'm not sure how to do this, so if anyone is interested let them try it......

I'm assuming that these mods could be done interchangeably on either APPJ.

Edit:
I've finished the listening session and I might have been a little hasty, I'm going to spend a bit more time with this damn tube, it seems to have got better as I've been listening and if it could be less sibilant and more open and resolving like the TS 12SL7 then it could be a good tube, it already has a nice wide soundstage. I'll report back when I've decided on it, and it's had more burn in.

 

[baronbeehive]

Re: the GE12SL7's I've had more time with them and revised my opinions of them somewhat. I still think they're slightly sibilant but I no longer think they're unclear, and as I said before the soundstage is good. Usually my first impressions are what I go by but I've had to go through the proper procedure and test them against my usual familiar test tracks because I wanted to be sure that the sibilance was not just really good detailing over and above what I've heard before. I can confirm though that this is not the case the detailing is good but not more so than say the Tungsols, moreover they are not as liquid as the Tungsols and that would be enough for me to stop using them but I think I will stick with them for a little while longer to see if they get any better. They are certainly good.

I think there is another reason why there is disagreement over some tubes and that is that there is another interaction with the mods we have done, and some mods would give a different sound signature and obviously the ones I have done do not affect these tubes negatively whereas some other mods using perhaps different component makes would have different affects on sound, if this is so then it makes comparisons between tubes difficult and probably members should try for themselves and just use what others have said as a rough guide.