GET*SET*GO my first foray into valves

If they glow, this is the place to be
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offanonone
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#1 GET*SET*GO my first foray into valves

Post by offanonone »

I built this December 2009, and have been very very happy with my first real amp.

Butttttttttttttt

The original valves are Ruski 6C4C and 3 out of 4 have become noisy over time. The nosiest pops and puffff's over the music, and the quietest is only heard between tracks from the comfy chair.

I have been in discussions with Andrew I, and have some NOS 6B4G's on the way as replacements.

He also prompted me to check the voltages, and I found that the HT was over 15% lower than the original build tests.

Swapped the rectifier (6AX5GT) and now they are above the target, but within 5%.

So finally (thank ch***t, I can hear you yell!)

The questions for the experienced.

The mains transformer is I think rated at 230v input, my mains is 239 - 241v. This is putting 335v into the rectifier (10v over the target). Will this have quickened the deterioration of the rectifier? is it worth trying to knock down the mains a bit?

I have had a root through the bits box, and have found a packet of ferrite tubes (about 12mm long, 5mm dia with a 2mm hole. Would these be ok to fit on the heater and grid valve wires? Is it worth doing?


Link to the build instruction in pdf http://www.diytube.com/getsetgo/getsetgo_manual.pdf

I have a few photies of the upturned beastie on the bench and a pdf with all the test voltages if anyone is interested, but will probably need some guidance on posting em.

Cheers,

John
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Nick
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#2

Post by Nick »

The extra voltage will make little or no difference. But maybe worth checking the heater voltages are in the right area (watch when measuring the rectifier heater as they heater will be at B+ voltage).
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#3

Post by Mike H »

Valves wear out unfortunately, especially power and rectifier ones. The popping etc. noises is caused by air getting in, or, compounds inside giving off gas so it's gone "gassy".

There may be an advantage replacing R3 - R4 with ferrite beads yes, also for o/p grids.
 
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#4

Post by offanonone »

Thanks for the replys,

A couple of photies on the bench

Image

Image

PDF of test voltages attached below.

Mike, would the ferrite tubes be ok on a piece of uninsulated wire in place of R3 & R4, or better to ferret out some ferrite beads (I wombeled some out of a piece of junk, just need to remenber where i stashed them)

John
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Paul Barker
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Post by Paul Barker »

Those RCA Red Base used to be collectable. I paid a relative fortune for a pair. But today they haven't kept their popularity.
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Post by andrew Ivimey »

red base red body, there is an equivalent of the 6SN7 with a red base which is ridiculously expensive too but some one I trust tried them and said they were a poor substitute for classic and still relatively cheap 6SN7s so pooh to them.

imho the 5693 red bodied version of the 6SJ7 is brilliantly better but then its a pentode driver for 300B and we hates them don't we preciousssssss
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Post by Mike H »

Yeah spawn of Satan .. get the stake and faggots ..Image

:lol:

Ferrite tubes should be OK, only one way to find out! I've used beads on bare wires without any probs
 
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Paul Barker
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Post by Paul Barker »

JackOfAll wrote:
andrew Ivimey wrote:red base red body, there is an equivalent of the 6SN7 with a red base which is ridiculously expensive too but some one I trust tried them and said they were a poor substitute for classic and still relatively cheap 6SN7s so pooh to them.
Don't currently have any kit that uses 6SN7's, but I've still got a good stash of tubes. I never really got the hype surrounding the red base 5692's. The RCA red base wasn't a great sounding tube IMHO, but I like the CBS (Hytron) brown base 5692's. In a back-to-back the RCA came-off sounding very recessed, like the music was gripped in a vice rather than allowed to breathe. And they don't like being run hard either. ISTR, that they were sold as a special quality, long life (10000 hour) tube. Not that I ever kept any of the RCA red bases in my gear for that long, but I remember several people commenting that the only way to get the advertised life out of them was to run them low current. Forget about 250V/8mA if you want 10000 hours use.
Yes I have the red base of both sn7 and sl7 versions.

But as the 76 sounds leagues better than any 6sn7 it's a pointless excercise tube rolling 6sn7's, just build with valves that sound good instead.

the only reason the 6sn7 became popular was because of it's plentiful supply it's modern base and it's reasonable performance. OEM's have to use such valves to guarantee future supplies.

Quircky guys who make one offs can go prior to the octal era and first tube they come across which will do the job shedloads better is the 76. go further back and you get even better results. The more modern you go the more in the direction of OEM's needs you go and the further from great sound. Unless by chance you happen to trip up over a 6em7 or some other modern miracle which defies the rule.
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#11

Post by offanonone »

Mike H wrote: Ferrite tubes should be OK, only one way to find out! I've used beads on bare wires without any probs
Cheers Mike,

I will remove the board at the weekend and do the tweeks.

I have 2 Os-con SA 220uf 10v (got for the WDPhono3 but never fitted), probably put these into the 6SL7 cathode bypass positions C3 & C4.

The red base 6SL7 was part of the original deal from the seller on another forum (pcb, mains trans, opt ,6C4C's, 2 x 6AX5GT, and the Red un)
Is it any better than a standard one, I don't know, but have a new valve to compare with now.

John
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#12

Post by Paul Barker »

JackOfAll wrote:
Paul Barker wrote: But as the 76 sounds leagues better than any 6sn7 it's a pointless excercise tube rolling 6sn7's, just build with valves that sound good instead.
Am I allowed to disagree with you? Just a little?

I take your point. But there are great sounding 6SN7's and I wouldn't describe tube rolling 6SN7's as being a pointless exercise. (Well, maybe, if you only have Sovtek and late production Philips ECG to play with. ;))
Yes Clive you are allowed to disagree if the application you used 6sn7's in is better suited to them than the 76. Me I would change the application.
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