Hifi tube amp advice please

horse

I know it's not a guitar amp, but I'm hoping to benefit from some tube expertise please:

I have a hifi tube amp (fatman 252 / rebranded Dared MP60) which has blown one of its 4 output valves (no longer glows). I think the amp is quieter than before, but the stereo balance stills seems to be correct (eg the right side with 2 tubes isn't louder than the left side with 1 working tube). Any idea why one side isn't louder / will this be putting additional stress on the other tubes or other components?

There is some ambiguity about what replacement tubes are required. The manual says they are 5881/EL34 (which I understand to not be the same thing), and there are a couple of stories online of people blowing internal fuses by trying EL34s, and then successfully using 5881s after getting their amps fixed. I see there are different types of 5881s, and I believe the stock ones in the amp are 6L6WGB (which seem pricey in the uk, particularly as I think I need to buy 4?). Anyone know whether other cheaper types are likely to be ok, such as these EHX 6L6GCs?

http://www.watfordvalves.com/product_detail.asp?id=278

Any other advice / things I need to be aware of?

Thanks in advance

UPDATE: for anybody who has the same challenge / finds this page from google in future:

Had an email from Fatman which said 'The 4 output valve tubes for iTube 252 are 6L6G, they can also be replaced by 5881.'

Looked up 6L6G, and noticed the ones available at £20 a pop said they were 'upgraded to 6L6GC spec', so I thought sod it and just got some EH 6L6GCs cheaper instead. Working fine so far, although think they might have less top end detail than the stock ones.

Thanks again to those who provided help below.

thumpingrug

I have a fatman tube amp and very please with it I am.  A couple of years ago I bookmarked this just in case.

http://www.avforums.com/threads/where-to-buy-vacuum-valves-for-fatman-itube.755544/

Its now a few years old but may be of use to you.

horse

thumpingrug said:

I have a fatman tube amp and very please with it I am.  A couple of years ago I bookmarked this just in case.

http://www.avforums.com/threads/where-to-buy-vacuum-valves-for-fatman-itube.755544/

Its now a few years old but may be of use to you.

Yeah, I enjoy mine too. Thanks for the link, but my search still goes on!

Misterg

horse said:

...Any idea why one side isn't louder / will this be putting additional stress on the other tubes or other components?

 

I guess a perception thing, and it could be stressing the remaining power valve on that side (depending on the circuit).

The manual says they are 5881/EL34 (which I understand to not be the same thing), and there are a couple of stories online of people blowing internal fuses by trying EL34s, and then successfully using 5881s after getting their amps fixed

EL34s draw much more heater current than the 5881s (1.6 amps each vs 0.9 amps each), which is what might blow fuses - I wouldn't fit them unless you were sure the amp could handle the extra heater current.

 

EL34s also require an enternal connection from the suppressor grid (g3) to the cathode - i.e. pin 1 to pin 8 on the base. In 5881, 6L6, etc. this conection is internal with pin 1 not connected. This leads some (lazy) designers to use pin 1 on the socket as an anchor point for unrelated components (which is fine until you plug an EL34 in) - I would check this, too.

...

I see there are different types of 5881s, and I believe the stock ones in the amp are 6L6WGB (which seem pricey in the uk, particularly as I think I need to buy 4?). Anyone know whether other cheaper types are likely to be ok, such as these EHX 6L6GCs?

http://www.watfordvalves.com/product_detail.asp?id=278

Any other advice / things I need to be aware of?

Thanks in advance

5881 is 5881; 6L6 is 6L6 (in its various guises).

This from TDPRI: "6L6WGBs are technically 26w tubes, vs 6L6GCs which are 30 watt rated. True 5881s, like the venerable Tung Sols, are 23 watt tubes. (Note: A strong feeling exists that the JAN 6L6WGBs are really 30 watt tubes. Their internals are identical to the JAN 6L6GC of the same manufacturing period.)"

6L6GC has a higher voltage and power rating than the 5881 (and the same heater current), so if you have 5881s already, the 6L6GC should work OK from an electronic perspective.

From a sonic perspective, I have no idea what it would do to your 'mid range warmth', 'sound stage', 'pace', 'ability to hear crystals of copper weeping', or other Hi-Fi essentials...  

 

ESchap

Misterg said:

 

This from TDPRI: "6L6WGBs are technically 26w tubes, vs 6L6GCs which are 30 watt rated. True 5881s, like the venerable Tung Sols, are 23 watt tubes. (Note: A strong feeling exists that the JAN 6L6WGBs are really 30 watt tubes. Their internals are identical to the JAN 6L6GC of the same manufacturing period.)"

6L6GC has a higher voltage and power rating than the 5881 (and the same heater current), so if you have 5881s already, the 6L6GC should work OK from an electronic perspective.

From a sonic perspective, I have no idea what it would do to your 'mid range warmth', 'sound stage', 'pace', 'ability to hear crystals of copper weeping', or other Hi-Fi essentials...  

 

The late 70's to mid 80's USA JAN 6l6WGB's are indeed the same internals as the Phillips Sylvania GC's of the same period.  Housed in a smaller bottle however.   Probably made to fit older (early 60's) military equipment that still required the small bottle size.  

They are great guitar amp valves, and I think well worth the extra over the modern Chinese / Russian / Slovak alternatives.  How they will be running uber clean in a HiFi I don't know, though I cant imagine they will be bad;  As the valve's are not run particularly hard in HiFi and they are very good quality valves, you may be able to get away with just replacing the pair rather than a quad.

horse

ESchap said:

Misterg said:

 

This from TDPRI: "6L6WGBs are technically 26w tubes, vs 6L6GCs which are 30 watt rated. True 5881s, like the venerable Tung Sols, are 23 watt tubes. (Note: A strong feeling exists that the JAN 6L6WGBs are really 30 watt tubes. Their internals are identical to the JAN 6L6GC of the same manufacturing period.)"

6L6GC has a higher voltage and power rating than the 5881 (and the same heater current), so if you have 5881s already, the 6L6GC should work OK from an electronic perspective.

From a sonic perspective, I have no idea what it would do to your 'mid range warmth', 'sound stage', 'pace', 'ability to hear crystals of copper weeping', or other Hi-Fi essentials...  

 

The late 70's to mid 80's USA JAN 6l6WGB's are indeed the same internals as the Phillips Sylvania GC's of the same period.  Housed in a smaller bottle however.   Probably made to fit older (early 60's) military equipment that still required the small bottle size.  

They are great guitar amp valves, and I think well worth the extra over the modern Chinese / Russian / Slovak alternatives.  How they will be running uber clean in a HiFi I don't know, though I cant imagine they will be bad;  As the valve's are not run particularly hard in HiFi and they are very good quality valves, you may be able to get away with just replacing the pair rather than a quad.

Thanks guys. I know it is all a bit of a gamble in terms of whether the end product sounds any good or not, but priority No1 is not blowing the new set or entire amp when I first turn it on after fitting them!

So what I'm taking away is that 6L6GC should be at least 'physically safe' if they were previously 5881s, but they're not the same thing so who knows soundwise.

Thinking I might go with these Tung Sol 5881 reissues, which seem to be the closest lower cost option I can find: http://www.hotroxuk.com/tungsol-5881-6l6.html

Misterg

Just a thought - have you tried swapping the suspect valve with its neighbour, just to prove that it's the valve that's faulty, not the amp?

Also, despite my earlier tongue-in-cheek comments, I would have thought that the sound differences between the valves in a HiFi amp would be very slight, since they're not being hammered into heavy distortion as they are in a guitar amp. (No doubt tomes have been written about the subtle differences between them, though).

horse

Misterg said:

Just a thought - have you tried swapping the suspect valve with its neighbour, just to prove that it's the valve that's faulty, not the amp?

Also, despite my earlier tongue-in-cheek comments, I would have thought that the sound differences between the valves in a HiFi amp would be very slight, since they're not being hammered into heavy distortion as they are in a guitar amp. (No doubt tomes have been written about the subtle differences between them, though).

Yes - a different valve lights up fine if I swap them ta. I'm hoping it will still sound as good with different valves - I believe the originals aren't anything special, but I can't find them for sale. I've really liked the amp up until now, I'm no audiophile but it has been a good match with my speakers. Have to say the misinformation and risk of wasting money has annoyed me.