[casperry]

Hi,
 
I agree on the burn in time, my pair has been running for quite a while before the sound improved. I picked up a used pair of EF91 mullards cheaply on ebay. I also have a pair of EF91 zaerix tubes as well as a bunch of EF92 mullards. They all share one good merit and it is a wide soundstage and a mellow, relaxing sound. Since some definition is lost in comparison to ef95 tubes I listen to them either through speakers or my beyerdynamic dt150s which are not as resolving as the hd600s which I prefer with ef95 tubes and my personal favourite m8100. Actually I don't have favourites carved in stone but different tubes satisfy my ever changing cravings, like one day I like strawberry ice cream but the next day I will eat chocolate one

 

[infinity650]

Hey casperry,
 
do you have the Mullard CV 4015 and if yes, could you compare them to the CV 4010 (M8100) and the Voskhods? I'm looking out for them at a nice price for a while and just want to know they're worth buying owning the M8100, Voskhods and Mullard CV 4014 EF91?
Which EF92 and EF 91 tubes do you own specifically?
 
 
Thanks,
 
Nik
 
 
EDIT:: I'm confused! Which one of the Mullard CV 4014 tubes is the best? They're quiet a lot different versions, Best would be with photos and exact name of them. Please help me.
 
I got these ones right now, think they're the CV4014 6AM6. Right?
 
http://www.tube-shop.com/ebay/tubes/CV4014.jpg

 

[casperry]

Quote:

Hey casperry,
 
do you have the Mullard CV 4015 and if yes, could you compare them to the CV 4010 (M8100) and the Voskhods? I'm looking out for them at a nice price for a while and just want to know they're worth buying owning the M8100, Voskhods and Mullard CV 4014 EF91?
Which EF92 and EF 91 tubes do you own specifically?
 
 
Thanks,
 
Nik
 
 
EDIT:: I'm confused! Which one of the Mullard CV 4014 tubes is the best? They're quiet a lot different versions, Best would be with photos and exact name of them. Please help me.
 
I got these ones right now, think they're the CV4014 6AM6. Right?
 
http://www.tube-shop.com/ebay/tubes/CV4014.jpg

Hello Nik,
 
I'll write some comparisons later because it is late now and should be sleeping already. You have there in that picture the Mullard ef91 tube. You are spot on about the different versions of Mullard tubes. The best ones are the ones which were made for military (M8161,M8083,M8100). Civilian type is usually marked with the letters CV (CV4010 for example). Commercial type may have just the family name on it - ef92. I also have the cv131 which is a general purpose ef92 mullard tube and apparently belongs to yet another class because the civilian version is named cv4015 and the military is M8161 respectively. Go for the military version if you can afford it!
 
Regards,
Cas

 

[infinity650]

Hi,
 
considering your last post I will go for the military specs. I know there's the "large shield" version, but how about these?
 
http://www.ebay.de/itm/MULLARD-VALVE-TUBE-CV5377-EF91-MIL-SPEC-NOS-NIB-/310377236679?pt=UK_Consumer_VintageAudio_RL&hash=item4843ecc8c7
 
Can you guys recommend them?
 
Greets
 
Nik

 

[casperry]

Quote:

Hi,
 
considering your last post I will go for the military specs. I know there's the "large shield" version, but how about these?
 
http://www.ebay.de/itm/MULLARD-VALVE-TUBE-CV5377-EF91-MIL-SPEC-NOS-NIB-/310377236679?pt=UK_Consumer_VintageAudio_RL&hash=item4843ecc8c7
 
Can you guys recommend them?
 
Greets
 
Nik

I haven't heard of CV5377s but the proper military version of this family is M8083 (this code is printed on a tube itself).  I have the M8100 and CV4010 from the ef95 family and the M8100 sounds better.
 
http://www.r-type.org/exhib/aaa1166.htm

 

[Yekrut]

Hey Guys,
 
An update on my problem. After Mordy's suggestion I checked both the driver and power tubes for signs of oxidation. Indeed the front driver tubes seemed to have some discoloring that I was able to scrape off. The good news is that this solved my previous problem! So big thank you to Mordy for the tip.
 
The bad news is I seem to have a new problem: sometimes my left channel completely gives out. I have to tilt my amp to the right, gently tap it for it to come back. It's a bit frustrating and I'm not sure what's causing this issue. I've also noticed some crackling when I turn the volume knob after leaving at a set position for a couple of hours.
 
Both these symptoms are worrying me a bit, and I was wondering if anyone had experienced similar problems? If not have any of you attempted to open your amp? I might be able to find something wrong internally.
 
Cheers!

 

[PanamaRed]

Just a heads-up, I am currently selling one of these bad boys with very little use on it (less than a year old):
 
http://www.head-fi.org/t/595301/littledot-mkiii-mk-iii-with-matched-mullard-81000

 

[mordy]

Hi Yekrut,
 
Did you try to switch around the tubes to see if the problem moves to the other channel? First try it with the driver tubes, then separately, with the power tubes.
My personal experience has been that intermittent but persistent crackling in one channel comes from a bad driver tube. If you have other sets of tubes to change with, try that, but only one pair at a time (first driver tubes, then power tubes).
Lower volume in one channel was traced to a bad power tube.
I would not open up the amp  before trying different tubes.
Good luck!

 

[Yekrut]

Thanks for the help once again Mordy.
 
It appears that one of CV4010 tubes was acting up a bit and was the source of the crackling. I replaced the right channel with the stock tube that came with the amp and the crackling went away. I'm now back to the two stock tubes, which although highlight the treble a bit too much for my taste, are mor enjoyable simply do to the lack of crackling. I'll want to make sure that the tubes were the source of the issue, and not something else in the amp, before starting to look for new tubes again!

 

[mordy]

Hi Y,
 
Glad you found the problem. Since both channels in the Little Dot MkIII amp are completely separate, it is quite possible to use two different driver tubes. I have tried it, especially when I have two similar tubes from the same manufacturer, such as 6AK5 and 5654, and it works fine. (The same would work for Mullard CV4010 and EF95 or M8100 or CV850.) The same tube from a different batch with different looking plate and getter also works fine for me.
Somehow, it seems to me that two very different tubes from different manufacturers, say a Tung Sol and a RCA, may have a slight detrimental effect on the sound.
In general, my experience has been that complete matching is not really necessary to get good sound.

 

[john57]

It has been my experiences that tube testers do not really test the tube with the same load or voltage that the tube will be under in an amp unless you have one of the tube lab testers. I had some tubes that will pass the tester but will fail in an amp when the tube is fully warmed up. I even had tubes that failed in a tester but will work in an amp depending on the situation.

 

[Lord Soth]

 
 
 
Quote:

It has been my experiences that tube testers do not really test the tube with the same load or voltage that the tube will be under in an amp unless you have one of the tube lab testers. I had some tubes that will pass the tester but will fail in an amp when the tube is fully warmed up. I even had tubes that failed in a tester but will work in an amp depending on the situation.

Yes, that is quite true.
 
To really test a tube (especially for matching), one has to use a tube tester which allows different settings for plate voltage and grid voltage.
 
An example of which is the Tube Imp
 
http://www.tube-imp.co.uk/
 
The problem with most tube testers is that they only test tubes at fixed rather than variable test settings.
 

 

[infinity650]

Hi,
 
my collection of different tubes is growing, not all have arrived, burned in and compared. Just an overview with some impressions so far:
 
(2x = a pair, so don't be confused)
 
 
Powertubes:

2x 6H30-DR                        supertube, slightly better detail and authority, especially more contro in bass than the gold-pin
2x 6H30PI Gold-Pin             very good, nice price-performance ratio


Drivertubes (EF95):

2x Voskhod 6ZH1P-EV                           : very detailed, very! nice voices, structured bass    -> allrounder
2x M8100/CV4010                                  : darker, groovy, lot of bass, "flow" to the music       -> singer/songwriter, agressive recordings become less annoying
2x RCA 5654 (Black Plate)                      : still BURN-IN  -> so far little bit cold, could be a perfect match with classic music
2x GE JAN5654W EF95                            not arrived yet
4x Voskhod 6SCH1PEV gold grid             : still BURN-IN   -> astonishing warm, striking different sound than the Voskhod above, further report coming soon
4x Raytheon JAN-CRP 6AK5 5654             not arrived yet
5x Tung-Sol 6AK5                                     not arrived yet


Drivertubes (EF92):

4x Mullard ?                                              not arrived yet, was an absolute bargain not knowing what tubes to expect. Let's see!



Drivertubes (EF91):

2x Mullard M8083                                           BURN-IN
2x Mullard 6AM6 CV4014                          still BURN-IN: relaxed, no harsh highs, voices unspectacular and so far a little bit disappointing
 
 
 
So, that's it for the moment, will update by time and having listened more intensively!
 
 
Greets,
 
Nik

 

[jsvilla93]

Hello, Ive been tube rolling for a long time and cant believe the differences in sound. But lately Ive added a oneac isolation transformer upgraded the caps inside and cant believe that it made an actual difference in improving the sound. Had a couple of friends listen and come to the same conclusions. Has anyone else  done the same. I live close to silicon valley and working in the semiconductor Field Ive noticed every piece of equipment hooked up to one of these isolation transformers because dealing in sub-micron geometries requires steady and clean AC. Meanwhile ill have fun checking my tubes again with the isolation transformer in place

 

[infinity650]

Hi,
 
my english isn't that good but what I can read out of your post is that you stick too much to technical explanations for possible differences in sound. Music is emotion - try to stay emotional in comparing different tube sounds and I'm pretty sure you'll hear at least slight differences!