Not sure how your amp is configured. 2 6CA7s per channel? or is it a quad per
channel?? If you can bias individual tubes, matching not so important. If the
bias is per channel and each channel only takes 2 tubes, I'd put the 28 & 31 on
one channel and the 58 & 62 on the other and wouldn't worry. If each channel
takes a quad and bias is per channel (or it's auto bias)...that seems little riskier to
have these 4 all on one channel. It's been recommended to me (own auto bias
mono blocks) to have values within 10% of one another. Might be helpful to
have a little more detail on how your amp is set up. Looking at your title
question...2 matched pairs as you have described certainly don't make a matched
quad.
channel?? If you can bias individual tubes, matching not so important. If the
bias is per channel and each channel only takes 2 tubes, I'd put the 28 & 31 on
one channel and the 58 & 62 on the other and wouldn't worry. If each channel
takes a quad and bias is per channel (or it's auto bias)...that seems little riskier to
have these 4 all on one channel. It's been recommended to me (own auto bias
mono blocks) to have values within 10% of one another. Might be helpful to
have a little more detail on how your amp is set up. Looking at your title
question...2 matched pairs as you have described certainly don't make a matched
quad.