Minimum space between 6V6 tube in Push-Pull Amp - diyAudio
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Old 11th January 2011, 06:07 PM   #1
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Default Minimum space between 6V6 tube in Push-Pull Amp

Hi everone and good day to all.

I am in the process of putting together a 2 channel amp with 6V6's in push pull. My chassis top side space is limited and the 4 6V6's will need to be close to each other. What is the minimum space I should have between tubes?

thanks

Bruce
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Old 11th January 2011, 06:13 PM   #2
DF96 is offline DF96  England
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I would suggest one tube diameter as the minimum spacing, unless you have very good cooling arrangements.
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Old 11th January 2011, 07:30 PM   #3
Cassiel is offline Cassiel  Libya
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Click the image to open in full size.



One screw to tighten two tube sockets, I'd would say that's the minimum. No tube rolling with coke bottle 6V6's - keep that in mind.
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Old 12th January 2011, 10:57 AM   #4
JLH is offline JLH  United States
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I keep at least 2 inches between tubes. Remember they have to have room in order to cool themselves. Having tubes too close can cause hot spots due to radiating heat.
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Old 12th January 2011, 11:01 AM   #5
DF96 is offline DF96  England
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I think the OP was asking about the minimum he should have, not the minimum possible. The amp shown in post #3 is likely to lead to overheating and short valve life unless the 6V6 are run with rather cool bias.
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Old 12th January 2011, 11:12 AM   #6
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Agree with earlier posts, one tube diameter is ok for smaller tubes up to, say, 10-15W Pa, high power tubes will usually require bigger spacing.

Edit:
The pic in post #3 says it all, i would never buy an amplifier where the constructor placed the tubes like this, this is clearly a sign to look for.

According to smallsignal tubes like the 12AX7, IMHO you can place them rather tight, as in 1/2 tube with or so.
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Last edited by Mr. Triatic; 12th January 2011 at 11:30 AM.
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Old 12th January 2011, 06:38 PM   #7
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look at a Quad II, or any number of commercial highly regarded amps. Tight is fine imo as long as their is reasonable air movement possible. The valve doesn't operate unless its hot remember - warm is good. I'm not aware of any tube that melted from the outside in...
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Old 12th January 2011, 08:34 PM   #8
Cassiel is offline Cassiel  Libya
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Quote:
Originally Posted by JLH View Post
Having tubes too close can cause hot spots due to radiating heat.
Hot spots? They're everywhere, just don't touch them.
I'd always choose good looks over longer tube life. Speaking of tube life, the glass won't crack so what else could go wrong? Melted parts? IMO 2 inches is too much for four 6V6s, doesn't look good to me - kinda like gapped teeth.

Mine is a DIY amp so I do what I want and I don't want a big chassis. 6V6's are cheap, who cares if they "could" last 6 months longer with a "proper" placement. I don't so less than an inch here.
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Old 12th January 2011, 08:53 PM   #9
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Morgen Jones recommends 1 1/2 times the tube diameter for spacing to keep one tube from heating the others
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Old 12th January 2011, 09:12 PM   #10
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has anyone measured it? I mean, actually measured surface temps and then calculated the amount of radiated heat and figured out what the % difference is with regard to proximity? I have just done a quick search and, apart from stuff on VH output raiio and research tubes, I can't find any emperical data or advice on the subject.

This implies its not a significant issue...
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