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We offer the following additional screening options so you can get the most out of your tube equipment.
For detailed description of the tests, please see below.
| Option | Recommended For | Pricing |
| Low Noise Screening | HiFi Preamp
Phono Stage
Guitar amp 1st stage
Reverb driver | $4 per tube |
| Triode matching * | Phase splitter stages | $2 per tube |
Conductance
cMatched Pair** | HiFi stereo amplifier | $4 per pair |
Note:
* Triode Matching is included when Matched Pair is specified.
** This is different from power tube matching. All the screening otpions apply to small signal preamp tubes only.
Specifying Screening Options
- On some tubes, we have listed pre-screened tubes (i.e. Triode Matched, Matched Pair) to make
your ordering easier! For these tubes, simply put the pre-screened tubes in your shopping cart. Price of screening options are already
included in the prices of pre-screened tubes.
- For tubes that are not pre-screened, you can still specify these additional options. Please specify which option you want for which tube
in the comments section during checkout. We'll select the tubes (may take additional 1-2 days depending on type) and send you the order
after adjusting the total.
- On select tubes, we have Matched Pairs that are already pre-screened for Low Noise. These are listed as Premium Matched Pair.
Of course, you can request Low Noise Screening on any matched pair tubes.
Description of Screening Options
Low Noise Screening
- For high gain stages like phono or guitar amp input stages, you want tubes with low microphony and low noise. We test for excessive
noise and microphonics in our regular screening, but we offer even further Low Noise Screening at additional cost. This option is useful
for your HiFi preamps and guitar amp V1/reverb driver positions which require much quieter tubes than normal.
- Our noise testing is done on fully custom built setup utilizing spectrum analyzers and audio analyzers from companies
such as Hewlett Packard (Agilent) and Tektronix.
Triode Matching
- Tubes like 12AX7 and 12AT7 found in audio/guitar amplifier applications have two triodes (vacuum tube units) inside.
Since vacuum tubes can have large variation, even these two triodes may vary greatly from each other. Our triode matching screens for
tubes with triodes whose conductance measure within 10% of each other.
- Triode matched tubes are recommended for use in Phase inverter stage (i.e. tube that drives output tubes), or on HiFi amplifiers that share
one tube between both left and right channels (i.e. first stage of McIntosh MC225).
Conductance Matched Pair
- For HiFi application with stereo circuits, it is best to have both channels operate as close as possible for better imaging and sound stage.
To achieve this, it is best to use tubes that are matched to each other in the same position on both channels.
Our matched pair screening selects two tubes that measure within 10% of each other's conductance for this purpose.
- Please note that our Matched Pair screening already includes Triode Matching. This means if you request matched pairs of tubes like 12AX7 or 6DJ8,
all triodes in the pair will be matched automatically.
- We also offer conductance matching on 3+5 tubes (triode + pentode) such as 6GW8/ECL86 or 6BM8/ECL82 family of tubes. We match output
pentode conductances for these tubes.
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