[Oskari]

  Got another one this one is suppose to be Mullard made Philips Miniwatt GZ32 also has same bite marks with RK 71 /B0E  .is it a Mullard .thanks

 
R71 B0E tells that it is a 1960 Blackburn Mullard GZ32.

 

[MIKELAP]

 

  Got another one this one is suppose to be Mullard made Philips Miniwatt GZ32 also has same bite marks with RK 71 /B0E  .is it a Mullard .thanks

 
R71 B0E tells that it is a 1960 Blackburn Mullard GZ32.

Would it be a good deal at $50.00

 

[Oskari]

  Would it be a good deal at $50.00

 
Better than the Mullard-branded one at twice the price or so. 

 

[Nic Rhodes]

Mike
 
as others have said, definately a Mullard. It is more normally labelled GZ37 and in my favourite goto tube in GZ range. These are the tubes I turn to first for full wave rectifiers like this. These rectifiers are indirectly heated (as opposed to 5U4G type directly heated) to combat cathode stripping and therefore have a nice slow controlled warm up (as opposed to 5U4G American types). U54 is just the GEC number that was used by GEC / Cossor etc however they labelled many examples as theirs that Mullard made for them with this distinctive thin slim ST look (They made their own fatter bulb version which is brilliant and earlier). Mullard made a huge number of these especially in the 66 / 67 era for the military (CV378) that many have stockpiled. All the GZ30, 32, 33, 34 and 37 are fine rectifiers worth looking at further. Most have a Uxx number or something like 52KU or 53KU used when supplied / made by others. The only thing you need to watch with all of these full wave rectifiers is the capacitance limitations and that will determine the PSU design and where / how you can swap. Filament voltages are often less than 5U4Gs. The voltage drop of the U54 / GZ37 is a bit less than the 5U4G but more than a GZ34 / 5AR4. The GZ33 is also a very similar tube to the GZ37.

 

[MIKELAP]

  Mike
 
as others have said, definately a Mullard. It is more normally labelled GZ37 and in my favourite goto tube in GZ range. These are the tubes I turn to first for full wave rectifiers like this. These rectifiers are indirectly heated (as opposed to 5U4G type directly heated) to combat cathode stripping and therefore have a nice slow controlled warm up (as opposed to 5U4G American types). U54 is just the GEC number that was used by GEC / Cossor etc however they labelled many examples as theirs that Mullard made for them with this distinctive thin slim ST look (They made their own fatter bulb version which is brilliant and earlier). Mullard made a huge number of these especially in the 66 / 67 era for the military (CV378) that many have stockpiled. All the GZ30, 32, 33, 34 and 37 are fine rectifiers worth looking at further. Most have a Uxx number or something like 52KU or 53KU used when supplied / made by others. The only thing you need to watch with all of these full wave rectifiers is the capacitance limitations and that will determine the PSU design and where / how you can swap. Filament voltages are often less than 5U4Gs. The voltage drop of the U54 / GZ37 is a bit less than the 5U4G but more than a GZ34 / 5AR4. The GZ33 is also a very similar tube to the GZ37.

Thanks guys  for all  the infos on these tubes according to Woo i can use all those rectifiers. I ended up getting the Mullard made Philips Miniwatt gz32 will see how that sounds .  Thanks                                                                                                                                                                                                                                                      

 

[Acapella11]

Swapped the MKIII for an MKIVSE and the first thing I noticed was the size difference. The MKIVSE is substantially bigger than the MKIII, I would say at least double the volume. It also sounds different, somewhat harder and more neutral. Also, I noticed that, with the MKIII and and C3GS, I put the volume control to about 8.30 - 9.30 o'clock, whereas now I am at 11-12 o'clock.

 

[TrollDragon]

Gain Setting?

 

[i luvmusic 2]

  Swapped the MKIII for an MKIVSE and the first thing I noticed was the size difference. The MKIVSE is substantially bigger than the MKIII, I would say at least double the volume. It also sounds different, somewhat harder and more neutral. Also, I noticed that, with the MKIII and and C3GS, I put the volume control to about 8.30 - 9.30 o'clock, whereas now I am at 11-12 o'clock.

  Now that you mentioned the difference between this two amps it makes me wonder if the MK IV SE is comparable to the CRACK.
IMO even i'am now using the C3g's sounds to me that the MK III still can't compete with the CRACK..

 

[MIKELAP]

  Swapped the MKIII for an MKIVSE and the first thing I noticed was the size difference. The MKIVSE is substantially bigger than the MKIII, I would say at least double the volume. It also sounds different, somewhat harder and more neutral. Also, I noticed that, with the MKIII and and C3GS, I put the volume control to about 8.30 - 9.30 o'clock, whereas now I am at 11-12 o'clock.

Interesting, more neutral  you say, is that with the Senns and by the way nice aquisition .MK4 has different sound signature ,does that mean better sound quality

 

[MIKELAP]

The Littledot mk3 use a 1A fuse does anybody know if its a fast blo or slo blo fuse 

 

[TrollDragon]

  The Littledot mk3 use a 1A fuse does anybody know if its a fast blo or slo blo fuse 

Probably a fast blow which looks like just a wire inside.
 
A slow blow fuse looks like this one.

But check your fuse and see.

 

 

[MIKELAP]

 

  The Littledot mk3 use a 1A fuse does anybody know if its a fast blo or slo blo fuse 

Probably a fast blow which looks like just a wire inside.
 
A slow blow fuse looks like this one.

But check your fuse and see.

 

Thanks i checked mine is a thin wire so it would be a fast blo.Woo amps is like your picture a slo blo .Woo says you can use a 2A or 3 A fuse thats weird which one would you use . Thanks 

 

[TrollDragon]

  Thanks i checked mine is a thin wire so it would be a fast blo.Woo amps is like your picture a slo blo .Woo says you can use a 2A or 3 A fuse thats weird which one would you use . Thanks 

That is strange they say you can use a 2A or 3A...
What is in it? I would stick with what is labeled on the amplifier or fuse socket or manual.

 

[MIKELAP]

 

  Thanks i checked mine is a thin wire so it would be a fast blo.Woo amps is like your picture a slo blo .Woo says you can use a 2A or 3 A fuse thats weird which one would you use . Thanks 

That is strange they say you can use a 2A or 3A...
What is in it? I would stick with what is labeled on the amplifier or fuse socket or manual.

i checked its a 3.15 A 250V.                                                                                                                                                                                                                                                        

 

[mordy]

Hi,
 
Still fighting my hum problem from my PC. A long time ago there was a post on this forum about somebody who plugged in an isolation transformer between the wall outlet and his LD amp and claimed an improvement in sound.
 
I found an inexpensive one and plugged it in between the wall outlet and the LD MKIII,  but did not notice any change in sound. Now I decided to try to plug it in between my PC and my wall outlet to see if it would reduce the hum.
 
This is how the unit looks like: (mine looks a little better but it is used)
 

 
Here are the specs:

 
There is definitively less hum, but it has not gone away completely. However, I can play quite loud without objectionable hum (hum can only be noticed when I pause the music at loud levels). I did an A/B comparison with my laptop, playing the same song at the same time, switching sound sources. The laptop has less hum (on pause), but the sound from the laptop is thinner with less impact. The PC sounds better with a more fleshed out and fuller sound.
 
I really have no idea about the electrical implications of what I am doing. It seems to me that this isolation transformer was used to clean up noise in telephone lines (echos of the C3g?):
 
Have two questions: The unit is rated 0.69A input and 0.625A output. It is getting somewhat warm to the touch, but not hot. Is it safe to use with a PC with a 420W PS?
As seen above on the bottom left, although it uses a grounded plug, there is a provision for an "environmental reference ground" according to a sticker on the unit. Would I benefit from using this ground? And if so, how?
 
Would appreciate help with this.