Rai168
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Posts posted by Rai168
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Thank you very much Myles for your patience and answer. I will pass on the hello - take care and again Thank you.
Rai
Originally posted by myles111:
Rai168...Originally posted by Rai168:Hi Myles - sorry about hte confusing last post but it was comprised of 3 emails I had written. Anyhow - long story short, I got the RFT's and I'm pretty excited to hear em. Heard a lot of great things from other VHT owners who use them. Anyhow my 1 question is this -
On the VHT's (after speaking w Mike) I learned that 2 pre amp tubes by the power tubes in the back (Most of the tone chain is in front) are actually the phase inverter section. There are 2 tubes that do the Inverting. How would the theory of matched tubes in the PI section relate to this? One is a 12ax7 and the other a 12aT7? Would both tubes, both triode's for each tube - have to match w/in themselves?
Thanks Myles and sorry for the earlier confusion.
Best wishes -
Rai
Each of the tubes in the phase inverter section should be matched. In stereo amp applications, there are also often 2 phase inverters/drivers.
Say hello to Mike from me if he is the Mike that used to be at Rivera.
Regards,
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Hi Myles - sorry about hte confusing last post but it was comprised of 3 emails I had written. Anyhow - long story short, I got the RFT's and I'm pretty excited to hear em. Heard a lot of great things from other VHT owners who use them. Anyhow my 1 question is this -
On the VHT's (after speaking w Mike) I learned that 2 pre amp tubes by the power tubes in the back (Most of the tone chain is in front) are actually the phase inverter section. There are 2 tubes that do the Inverting. How would the theory of matched tubes in the PI section relate to this? One is a 12ax7 and the other a 12aT7? Would both tubes, both triode's for each tube - have to match w/in themselves?
Thanks Myles and sorry for the earlier confusion.
Best wishes -
Rai
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Hi Myles - thank you for answering all my questions - here goes - it's from a 3 part email so I apologize for the length -
Hi Myles,
>
>An Updated question for you - which tube psotion is
>the phase inverter? In a previous email you stated -
>
>... the most important aspect of your phase inverter
>tube is making sure the two sides match within 0.2 mA.
>Then also be sure your output set is closely matched
>
>I have a chance to buy a matched pair of RFT ECC83's.
>I'm planning on using it in the V1 position and
>possibly the phase inverter position. My set up would
>be V1 RFT v2 Phillips 12ax7 (If I'm correct the V4 is
>the phase inverter - not sure though) v3 Phillips and
>v4 RFT
>
>Again in my power amp Section I have 2 preamp tubes to
>help w clipping. Right now it goes v1 Phillips 12ax7
>WA and Sovtek 12At7. Would replacing the Sovtek 12At7
>in the pwoer amp section w a 12ax7 cause me to lose
>clarity but more gain? Just curious - I'm working on
>getting a Phillips, or GE 12at7 for that position.
>
>Finally is it important for all the preamp tubes to
>match or mainly the phase inverter tube? Thanks again
>Myles - Hope all is well...
>
>Rai
>
P.S. Would these be good to replace the 12AT7 (not
>sure if an ECC82 is the same as a 12AT7) Here are the
>specs - Would I be better w a 12at7 or 12ax7 for the
>P.I.? How would thee be for the 12At7 in the power amp
>section?
>
>I have 2 pieces of used ECC-82 tubes.
>Made by RFT(Germany).
>Packing:OEM.
>
>15-20 years ago the electron tubes have become
>needless because of modernization
>of a Microwave Laboratory of Technological Institute
>of Budapest.
>
>The tubes have been checked by a calibrated Hickok
>539B tube tester.
>By the operating manual of the tester the typical
>value
>of the MC(Mutual Conductance) of the ECC-82 tube
>is:1950
>This is taken as 100%.
>(Given for each tube System 1 and System 2 [in
>Micromhos]).
>On each tube I placed a little white sticker with the
>measurement results.
>
>MUTUAL CONDUCTANCE TEST: here we can get exact
>numerical value in micromhos.
>The condition of TUT (Tube Under Test) can be
>expressed in percent.
>For example:in case of ECC-82 the listed typical
>value of mutual conductance is 1950 micromhos.
>If the TUT has 2300, the percental condition is
>(2300/1950)x100%=118%.
>
>Result of the mutual conductance test, as follows:
>
>-Nr.001.tube
>triode No.1.=2700/1950x100=(139%),
>triode No.2.=2800/1950x100=(144%).
>
>-Nr.002.tube
>triode No.1.=1800/1950x100=(92%),
>triode No.2.=1900/1950x100=(97%).
>
>
>Thanks Myles...
>
>Rai
>
Well I got my eye on a matchedpair of RFT 12ax7's
>(aside from the ones I sent you specs on) He states
>they are matched to each other but the triodeas are w
>in close spec - here is what he replied.
>
>The pairs are closely matched to within 0.50 db, where
>you will not get
>any skweing of the sound image.
>
>
>Is that close enough? Again they are 12ax7's so I'm
>not sure if that would be decent for the PI position.
>$26 for both so I think I may go for it if you say
>they are decent. I'll probably put them in the front
>section as opposed to the PI if they aren;t close
>enough for the PI.
>
>I talked to Mike at VHT - he broke down what each
>position does in my amp and about the PI section
>
>V-1 Intial stage - important - first gain stage but he
>said V2 and V3 are more of the tone changers as far as
>distortion characteristics - seems a lil weird but
>I'll buy it. v4 is the last gain stage - I guess the
>clean channel goes from v-1 and bypasses 2 and 3 and
>goes to v4 - I'm assuming I'd want a cleaner tube
>there if I want my clean to shine. Anything you could
>recommend for a Fender type direction clean?
>
>As for the PI section get this - the 2 preamp tubes by
>the pwoer section he says are for the PI. 1 12ax7 and
>1 12at7. Right now I have a phillips 12ax7was back
>there w the stock sovtek 12at7. How would i go about
>matching the PI section here? Would I jsut get 2
>matched Inverter tubes (both sides of the triode)?
>
>Thanks for all your patience -you seem to be the one w
>the msot knowledge so I hope I am not bothering you
>too badly...
>
>thank you -
>
>Rai
Feel free to ask Myles
in Guitar Forum
Posted
Hi Myles. I am running GE6550A's in my VHT Ultralead. I know these are a high output tube. What's a good bias to run it at? I think my tech may have them a lil cold...I was originally running the Sovtek KT88's and he had to turn the bias down for the GE6550A's. Just looking for a recommendation as I play hi-gain stuff. Thanks -
Rai
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