RAM Labs Preamp Tube Testing Results

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Adam Goldfine

  • Newbie
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RAM Labs Preamp Tube Testing Results
« on: 29 Jul 2008, 12:06 pm »

Much has been written about RAM Labs testing of tubes, but I can't find much by way of explanation of the results you obtain for preamp tubes. On the box there are 5 parameters, VN, RAM, MIC, GAIN and PV

I think it would be useful to have some sort of guide to interpreting the results and how it affects the tube's performance.

Some are obvious of course, GAIN I assume is voltage gain and MIC is microphonics. But how does the GAIN measurement affect the channel balance of the preamp. Is there one tube in each channel or one section of each tube in each channel? Do you add the sections together to get the total voltage gain for the channel, then convert it to dB to get the balance?  :icon_surprised:

For the other parameters, what units of measurement are used? For each parameter, are higher or lower numbers are more desireable?  :?

I for one would appreciate having a greater understanding of the work that goes into rating these tubes and how to interpret the results. I know you had talked about discussing your tester in some detail in a previous post. This may be a good opportunity for that as well.  :)



  • Jr. Member
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Re: RAM Labs Preamp Tube Testing Results
« Reply #1 on: 10 Aug 2008, 08:01 pm »
I don't know what the numbers mean either, but I will say that all the power tubes I have bought from Roger are extremely well matched in circuit, it  seems they are all within 5% which is incredible compared with tubes I have bought from other dealers claiming to be offering well matched tubes - I won't name names, other than Roger's tubes are the real deal.


Re: RAM Labs Preamp Tube Testing Results
« Reply #2 on: 11 Aug 2008, 02:37 pm »
Amen to that Paul. I had a some very very well matched Seimen NOS EL34's that i got from Roger for my old RMMkII and they worked fine for 11 yrs untill i sold it.



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Re: RAM Labs Preamp Tube Testing Results
« Reply #3 on: 2 Nov 2008, 12:28 pm »

I found this on the Ram Labs Web site. I think it explains the numbers a little better.

  • VN Noise voltage ouput in micro-volts over a bandwidth of 400 - 20K Hz.
  • RAM Our proprietary factor for the perceived sonic noisiness and variation.
  • MIC Microphonics, susceptability to airborne and chassis vibration.
  • GAIN AC voltage gain at 1K Hz.
  • PVT DC value at plate to show operation variations.

Link here