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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 307

post #4591 of 10500
Quote:
Originally Posted by i luvmusic 2 View Post
 

I finally did my first 9pin(Driver Tubes) adapter for LD 1+ and LD MK III i've used a 12AU7/12AU7A(Rogers,Electro- Harmonix,JJ Electronics and  Chinese made)those are the only tubes i have.They all hum on both amps i doubble checked all my solder joints and pin connections to the amp(unplug/plug it back)still humming.Could it be the Tubes?

 

Quote:
Originally Posted by kvtaco17 View Post
 

I had the same issue and regardless of what I tried it never went away... UNTIL I added an external DC regulator of the heater circuits AND grounded the - lead to the chassis as per Gibosi... hope that helps.

 

Disregard this lol I need to learn to read better when I'm sleep deprived (yay hr 34!)

 

Boom! lol

post #4592 of 10500
What kind of adapter did you build / use? Do you have any pictures of your adapter setup you could post?
post #4593 of 10500

Ive made a 6DJ8 adapter a 12AX7 and an 6SL7octal adapter and i have only1 tube that has a very very faint hum  out of 7octals. the 12ax7 the 6DJ8 nothing .I would like to know how come some adapters hum and some others dont .Like Mojorisin adapter on my amp perfect on his amp buzzing how come i would like to know the answer to that one .Any ideas guys !

post #4594 of 10500

Lexan is the Answer!  Now what was the Question?

Oh yeah Hum...

 

Lexan piece cut to fit the top of the driver tube rings, center front screws hold the lexan in place and it's very easy to install and remove if required. I had cut the bottoms out of those nasty NEC 6AV6's to use as B7A plugs and remembered that pins 5&6 had been cut off. No big deal the adapter just has to run in EF92 mode instead of EF95.

 

Ceramic B9A socket attached to the lexan and wired up to the old 6AV6 base pins, short wires A/G/K wires with a twisted heater supply and this adapter is totally silent with no music playing.

 

The Lexan was cut with a jig saw so it is far from perfectly shaped, I'd kill for a scroll saw and a drill press... :D

 

So without further ado... The money shots with a 6Н2П-ЕВ

 

Top View

 

Side View

:beerchug:

post #4595 of 10500
Quote:
Originally Posted by MIKELAP View Post
 

Ive made a 6DJ8 adapter a 12AX7 and an 6SL7octal adapter and i have only1 tube that has a very very faint hum  out of 7octals. the 12ax7 the 6DJ8 nothing .I would like to know how come some adapters hum and some others dont .Like Mojorisin adapter on my amp perfect on his amp buzzing how come i would like to know the answer to that one .Any ideas guys !

 

AC input noise is my very early assumption... Mine had a ton o' hum initially... running it with my home theater power conditioner reduced 90% of it... BUT going to the DC regulator and tying the - input lead to the chassis ground solved everything 100%! I'll look into it more tomorrow.

post #4596 of 10500
Quote:
Originally Posted by TrollDragon View Post
 

Lexan is the Answer!  Now what was the Question?

Oh yeah Hum...

 

Lexan piece cut to fit the top of the driver tube rings, center front screws hold the lexan in place and it's very easy to install and remove if required. I had cut the bottoms out of those nasty NEC 6AV6's to use as B7A plugs and remembered that pins 5&6 had been cut off. No big deal the adapter just has to run in EF92 mode instead of EF95.

 

Ceramic B9A socket attached to the lexan and wired up to the old 6AV6 base pins, short wires A/G/K wires with a twisted heater supply and this adapter is totally silent with no music playing.

 

The Lexan was cut with a jig saw so it is far from perfectly shaped, I'd kill for a scroll saw and a drill press... :D

 

So without further ado... The money shots with a 6Н2П-ЕВ

 

Top View

 

Side View

:beerchug:

well done!

post #4597 of 10500
Quote:
Originally Posted by TrollDragon View Post

What kind of adapter did you build / use? Do you have any pictures of your adapter setup you could post?

I just used the 9 pin socket saver from Ebay soldered 18 gauge speaker wires on the pins and used coax cable solid conductor on the other end of the 18 gauge speaker wires(Pin)for plugging it in to the amp.Sorry i already took it apart i just tried it while i'am waiting for my ceramic tube sockets and other parts from the online retailer i just can't wait for it that is why i used what i have for now.I will give it a try once all the proper parts arived.

I will let you guys know when i'am done with the new one, i hope i'am not going to have the same problem.You guys are helpful  THANK YOU!

post #4598 of 10500
Quote:
Originally Posted by TrollDragon View Post
 

Lexan is the Answer!  Now what was the Question?

Oh yeah Hum...

 

Lexan piece cut to fit the top of the driver tube rings, center front screws hold the lexan in place and it's very easy to install and remove if required. I had cut the bottoms out of those nasty NEC 6AV6's to use as B7A plugs and remembered that pins 5&6 had been cut off. No big deal the adapter just has to run in EF92 mode instead of EF95.

 

Ceramic B9A socket attached to the lexan and wired up to the old 6AV6 base pins, short wires A/G/K wires with a twisted heater supply and this adapter is totally silent with no music playing.

 

The Lexan was cut with a jig saw so it is far from perfectly shaped, I'd kill for a scroll saw and a drill press... :D

 

So without further ado... The money shots with a 6Н2П-ЕВ

 

Top View

 

Side View

:beerchug:

Very nice, the socket you have is similar to the one that i ordered(9 PIN CERAMIC CHASSIS MOUNT)the one i just did is more like what you have in your pictures only deffirence is i did not used a shrink tube on the pins to the amp Oh and my is UGLY.


Edited by i luvmusic 2 - 1/4/14 at 7:02pm
post #4599 of 10500
Quote:
Originally Posted by kvtaco17 View Post
 

 

 

Boom! lol

I have to look into that once i'm done with the proper adapter.THANKS

post #4600 of 10500

I have discontinued the use of the 6CG7/6FQ7 tubes as power tubes since I am afraid that they are not suitable and will overdrive and damage the driver tubes. Measured over 208/216V plate voltage on a 12AX7 tube which I think is too much .

 

When I get my voltage regulator (on a slow boat from China) I will try these tubes as driver tubes.

post #4601 of 10500
Quote:
Originally Posted by gibosi View Post
 

 

Mordy,

 

Perhaps Ctritical Bill (CB) will weigh in on this.... However, from one of his earlier posts, it would seem that this is not good....

 

http://www.head-fi.org/t/563884/little-dot-tube-amps-vacuum-tube-rolling-guide/4125#post_10027162

 

If I understand CB correctly, a plate voltage of 173 V on your 6SL7 driver tube may be close to over driving your 6CG7 output tubes. Again, if I understand correctly, the 6SL7 works best with a plate voltage around 200 V and the LD simply cannot provide a driver tube with voltage this high. So even though it sounds good, it is probably not advisable....

 

But again, if I understand correctly, this is more an indication of the unsuitability of the 6SL7 as a driver tube in the LD, than it is a problem with using the 6CG7 as an output tube. Once you get an external heater, using a 6SN7 or 6CG7 as a driver could well be better.

 

What you are seeing here is the effect of an unregulated power supply. The 6N6P powertubes put out about 20 ma and the 6CG7 probably less than half that so the lower current draw increases the B+ . You have it exactly right in saying the 6SN7 is a better choice than the 6SL7.

I noticed on the Little Dot forums this post - http://www.littledot.net/forum/viewtopic.php?f=3&t=2558&sid=178231eb44fc074676fcd7b72f273695 where David Zhezhe says "The 6CG7 is usable however the 6BQ7 is not." in response to a question on power tube rolling in the MK111. However, someone tried the 6CG7 and was not impressed but I think this may be due to the use of lower impedance headphones as with higher impedance the lack of current shouldn't be a problem.

post #4602 of 10500
Quote:
Originally Posted by TrollDragon View Post
 

Lexan is the Answer! 

 

 

Now this is one good looking adapter. Congratulations!

Hum is one serious problem with tube amps. And if DIY adapter or amp is not humming one could be very pleased with himself. I can't stand any hum, it drives me crazy.

 

Here is something about my latest DIY amp, if someone is interested...

http://www.head-fi.org/t/698282/my-diy-6sn7-6as7-headphone-tube-amp

 

btw my 6sn7-6as7 amp is much smaller on desk area than LD MK IV, but higher.

post #4603 of 10500
Quote:
Originally Posted by TrollDragon View Post
 

 

 

Ceramic B9A socket attached to the lexan and wired up to the old 6AV6 base pins, short wires A/G/K wires with a twisted heater supply and this adapter is totally silent with no music playing.

 

 

 

Hi all.

I've also just finished to build my 9pins --> 2x7 pins adapter for LD MKII+ , which includes a switch to commute between 6DJ8 and 12AX7 modes (for the moment not yet into a case as I'm still slooooooooooooowly waiting for the case delivery).... but it's humming a lot  :-(

Strangely, the hum depends on how high I pull the driver tube (a 6N23P Voskhod 1975): if it's stretched all the way up (wires completely extended), it hums like hell; if I push it down almost in between the 7 pins sockets... dead silent.

I guess that by pushing it down, I keep some wires apart and so I reduce some cross interferences. Or maybe I ground some wires by touching them and this solves the problem. I do not know.

 

As I'm a noob in electronics, I'm actually quite curious about the sentence in bold above: what actually does it mean to short A/G/K wires with a twisted heater supply, and will this potentially help me to reduce the hum?

 

BTW, I also made an octal --> 2x7 pins adapter, and this one is humming a bit less, but still not silent :(

 

 

I take the chance of this message also to thank all of you for your precious help, inspiration and suggestions for taking this further step into the LD tube rolling realm.

Without your ideas (especially Artsi's help, with his wonderful walkthrough for the switched adapter), I'd have never made this attempt into the "diy adapters" world.

And for whoever is thinking if they should try to build these adapters, I can just say DO IT !

It's easy, cheap, rewarding and with the help of guys like gibosi, mordy, TrollDragon, MIKELAP, Artsi, etc you can not go wrong (but I take no liability for encouraging you to take this step if your amp explodes, incinerates, detonates, evaporates, implodes or melts while you test your adapter  :wink_face:)

post #4604 of 10500

Thanks @kvtaco17 @i luvmusic 2 @Artsi and @vic2vic I think this one performs so much better than my copper pipe adapter for 6DJ8's, but I will modify the pipe for octal tubes.

 

 

Quote:

Originally Posted by vic2vic View Post
 

 

Strangely, the hum depends on how high I pull the driver tube (a 6N23P Voskhod 1975): if it's stretched all the way up (wires completely extended), it hums like hell; if I push it down almost in between the 7 pins sockets... dead silent.

 

As I'm a noob in electronics, I'm actually quite curious about the sentence in bold above: what actually does it mean to short A/G/K wires with a twisted heater supply, and will this potentially help me to reduce the hum?

 

BTW, I also made an octal --> 2x7 pins adapter, and this one is humming a bit less, but still not silent :(

Hey vic2vic

 

With most builds of tube amps out there the heater wires are twisted together to cancel out the AC 60Hz hum. When they route these wires they either run them close to the case or at 90° to the other wires. When you run the heater wires parallel to the Anode / Grid / Kathode wires the AC will induce a magnetic field into the parallel wires and you get hum, this is the case with my copper pipe adapter. So what I am going to do is either run the heater wires outside of the pipe up the back so they are not visible, or run shielded heater wires with the shield attached to the top and bottom of the pipe pieces. Both of these possible solutions have to be tested yet and will probably be later on as I will be enjoying my music with the little lexan adapter for a while. :D

 

The external DC heater board will solve your hum problems but it also depends on your application and situation if the external is feasible or not. I was pondering the use of a Low Dropout Rregulators (LDO) with a Schottky Bridge and a few caps... built into the back of the LD MK IV as the LDO's will still regulate with a source of only 0.2V higher than the output. Taking in account the voltage drop of the diodes and filter capacitors, it could be done with a MK III or IV chassis, not too sure about the MKII as there is less room.

 

To sum it up I would move your heater wires around, make them longer and keep them away from the other wires, route them at 90° if possible and see if that doesn't remove the hum. The BOLD part in the quote tells me that it's most likely a wire routing thing. I tried to keep my A/G/K  wires as shot as possible on the lexan adapter to see if that had a any effect. It shouldn't since others are running the BreadBoards with 6" of wire from the vectors to the board all in the open air BUT with enough distance from the heater wires.

 

Modify, test, adjust and modify more, It's all part of the fun we have here when you have something that is hum free take some time and enjoy your music as that is the whole purpose.

:beerchug:

 

 

* Always remember there are LETHAL voltages on some of the pin's, so be careful and have fun. *

post #4605 of 10500

It's nice to see so many people finally taking a leap of faith and building their own double triode adapters! Trust me, it's the best decision you'll have ever made for your LD! :beerchug:

 

Of course now you need good tubes for your sparkly or less sparkly adapters. While I can give ideas and review tubes, I can't make pretty adapters like all those cool kids here lol. But, I can help choose premium 6DJ8 (and empty your wallets)!

 

So, after spending ~30h with my Pinched Waist Amperex Holland 6922 (7L3 batch), I tested the Amperex Holland non-PW D-getter 6922 from the 7L4 batch.

 

Basically another tremendously good tube, honestly. Transparent and ultra-detailed as hell, with a sense of immediacy and PrAT that's possibly the second best I've heard in the 6DJ8 family. Highs and lows are well extended, with shimmering treble and tactile bass. Soundstage and sense of 3D are excellent with pinpoint accuracy and instrument placement; truly one of the best tubes I've heard to date. Listening to this tube with virgin ears (as in not right after listening to another tube for an hour), I almost started to think it was better than the PW 6922, and in some ways or for some people it very well may be. For the first three songs, the illusion was almost perfect, but after 15 minutes I started to have a doubt.

 

So of course, after letting the amp cool down, I threw the PW back in and let it warm up again. It didn't take me long to figure out what had been bothering me. In one word: the music. Let me explain.

 

I'd mentioned the last time around that the PW almost made it seem like you were in the music and not just listening to it - and also mentioned that it was often destabilizing and difficult to get used to depending on the track (hard to get "into"). Well, that may be the non-PW 6922 7L4's only fault: to be the best tube to reproduce music but not to be in it. I know this sounds silly, but let me explain what I mean a bit more.

 

The second you play a track with the PW, you don't even need to close your eyes to feel that you're in a enclosed space with realistic reflections (a sense of true "wetness" to the sound) and liquid tame instrument and voices playing. There's no real 3D or holographic effect anymore, just a studio in front of or in between your eyes, like you're in a smoky club after five drinks or in a studio after working 20 hours without a break, just staring at the musicians in a daze and letting the music "sink in" because you're too tired to tap your feet and really listen at this point. Well that's what the PW are like, and it can make you feel uncomfortable when you're expecting a punchy and forward headphone music session.

 

The sound just doesn't sound immediate, forward or infinite. It sounds like the exact opposite, it's like a dreamy vague yet ultra-precise room with a sense of absolute boundary that's there but hard to pinpoint. The dream vs music analogy is actually as accurate as I can be in describing the difference between both tubes. the non-PW 7L4 is the best for rendering music, punchy and immediate, but it's still just reproducing a signal; while the PW 7L3 shows you a vivid dream of that very same signal with finer details like your brain is filling in the gaps in the story (think about how realistic some dreams are, despite being pure brain fiction of stuff you may have never seen or heard), and as we all know how some dreams can leave a very very strong impression for days at a time and others forgotten right away. So for some tracks the PW almost sounds too much like a waking dream and not immediate enough, making you want to switch back to a tube that just reproduces the music and does it well, but at the same time once you've seen the dream, it's hard to go back to reality lol...

 

I guess if you were to twist my words just a little, you could sum up all this crap I wrote and describe the PW as a wet dream, and the non-PW as a cool concert. Both might leave a strong impression on you, but in a dramatically different way lol...

 

Last thing, the Holland D-getter 6922/E88CC I just tested actually reminds me quite a bit of the US 6922 (early ones, 1962 and before): punchy, dynamic and extended, but the Holland D-getter version is more detailed and realistic. Oh, and both the 7L3 PW and 7L4 non-PW tubes are basically perfectly quiet; not mute like the E188CC but totally silent.

 

Edit: Speaking of my Tour de France of premium 6DJ8, I'm still waiting for my single US Amperex VR0 D-getter 7308 (about as rare as the PW 6922, if not rarer) which is still stuck somewhere between the US and Europe after a forced - and slightly ironic - layover in Israel on Xmas eve lol... Hopefully, it isn't really lost... I'm looking forward to this tube since it would be a good chance to compare some of the absolute oldest an most premium US 6DJ8 to the European ones. Anyway, we shall see...


Edited by Audiofanboy - 1/5/14 at 8:22am
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