rplace Posted October 16, 2019 Share Posted October 16, 2019 Got a new preamp to test out and all 4 tubes are 6SN7s which I have a lot of. I often read the "signal" tubes are the ones that matter the most when rolling tubes. Is that only in amps and not preamps? the manual states the following..... Quote The right tubes are for the differential voltage gain stage. The left tubes are for the cathode follower output stage. So of those two choices above, right or left, which are going to have the greatest sonic impact? 1 Quote Link to comment Share on other sites More sharing options...
cyto Posted October 16, 2019 Share Posted October 16, 2019 Without seeing a schematic that is a little difficult to answer. You may find that some tube brands will have more of an effect in one area than another. The preamp you have will benefit from having good quality tubes in either position. Some people think that a tube in a cathode follower position is not that important sonically, but it is. In general gain stage tubes are more susceptible to problems that non-gain stages, but again it is very circuit dependent. The only way to answer your question definitively is for you to experiment. I would pick one side and give it a go, then later swap the left and right to see the difference, if any. Quote Link to comment Share on other sites More sharing options...
jcmusic Posted October 20, 2019 Share Posted October 20, 2019 On 10/16/2019 at 7:00 AM, rplace said: Got a new preamp to test out and all 4 tubes are 6SN7s which I have a lot of. I often read the "signal" tubes are the ones that matter the most when rolling tubes. Is that only in amps and not preamps? the manual states the following..... So of those two choices above, right or left, which are going to have the greatest sonic impact? Would this be a Rogue 99 by chance? If so the two tubes on the right side will have the greatest influence on sound quality, let me know if it is a Rogue I can help. 1 Quote Link to comment Share on other sites More sharing options...
rplace Posted October 21, 2019 Author Share Posted October 21, 2019 On 10/20/2019 at 9:13 AM, canyonman said: Would this be a Rogue 99 by chance? If so the two tubes on the right side will have the greatest influence on sound quality, let me know if it is a Rogue I can help. No Its a Schiit Freya+ Quote Link to comment Share on other sites More sharing options...
jcmusic Posted October 22, 2019 Share Posted October 22, 2019 23 hours ago, rplace said: No Its a Schiit Freya+ Well in that case I am not sure, I have a Rogue 99 Magnum and have used many different tubes in it and the two tubes on the right side are the ones that effect sound quality the most. Quote Link to comment Share on other sites More sharing options...
jcmusic Posted October 22, 2019 Share Posted October 22, 2019 So if your new pre amp uses 6SN7 tubes you can try the 6F8G tubes with an adapter which are better than any 6SN7 tube I ever heard. Or even better and what I use in my Rogue are the 6J5GT tubes with an adapter, they are the most linear octul tubes out there. You will need a quad though, they are exactly one half of a 6SN7 tube so 4 tubes and 2 adapters. 1 Quote Link to comment Share on other sites More sharing options...
rplace Posted October 22, 2019 Author Share Posted October 22, 2019 @canyonman Interesting. I'll have to do some looking into that once I've rolled a few from my vintage stash through it. Thanks! Quote Link to comment Share on other sites More sharing options...
jcmusic Posted October 22, 2019 Share Posted October 22, 2019 8 hours ago, rplace said: @canyonman Interesting. I'll have to do some looking into that once I've rolled a few from my vintage stash through it. Thanks! Well do check it out, you will not be disappointed and you will not go back to 6SN7's!!! Oh I forgot to mention that the 6J5GT's are a lot cheaper than the 6SN7's.... 1 Quote Link to comment Share on other sites More sharing options...
Deang Posted November 3, 2019 Share Posted November 3, 2019 On 10/17/2019 at 12:43 PM, Jeffrey D. Medwin said: The input tube ( of an amp or preamp ) develops the voltage gain, and it is most critical. This is correct. Jeff wins the zip tie award, lol. Quote Link to comment Share on other sites More sharing options...
deafbykhorns Posted November 12, 2019 Share Posted November 12, 2019 Try a 26 or a 01A preamp fpr some real magic Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted November 16, 2019 Share Posted November 16, 2019 Tube rolling is interesting but, it has it's limits on fidelity. Quote Link to comment Share on other sites More sharing options...
MechEngVic Posted November 16, 2019 Share Posted November 16, 2019 1 Quote Link to comment Share on other sites More sharing options...
jcmusic Posted November 16, 2019 Share Posted November 16, 2019 6f8G's great sounding tubes... Quote Link to comment Share on other sites More sharing options...
rplace Posted November 16, 2019 Author Share Posted November 16, 2019 3 hours ago, MechEngVic said: Tell me more please. Assuming the things on the bottom are adapters? I'm listening to mine as I type with 1940s Ken-Rad and Tung Sol mouse ears Really like the ability to listen in passive mode and it not have the tubes turned on. Quote Link to comment Share on other sites More sharing options...
MechEngVic Posted November 17, 2019 Share Posted November 17, 2019 On 11/16/2019 at 4:33 AM, rplace said: Tell me more please. Assuming the things on the bottom are adapters? I'm listening to mine as I type with 1940s Ken-Rad and Tung Sol mouse ears Really like the ability to listen in passive mode and it not have the tubes turned on. I just found this image online. But I do have experience rolling tubes. You just gotta do it. Buy a few sets, you can almost always get the majority of your money back if you decide not to keep them. In my experience, the component will sound the best when mated with the tube the circuit was designed around, I usually roll different brands or NOS vs NEW. If you're getting an improvement in sound with a different tube, the original tubes may be poor quality or you might have speaker placement issues, especially if you have a subwoofer. You can't imagine the impact on high frequency and imaging subwoofer placement and phase can make. That being said, I don't discount what others have said about a different tube sounding better in that particular circuit. There are many variables. Are you not happy with the sound of the preamp? Quote Link to comment Share on other sites More sharing options...
MechEngVic Posted November 18, 2019 Share Posted November 18, 2019 3 hours ago, Jeffrey D. Medwin said: Hey, good post. Go the next step !! Measure and determine what the Ohmic value is of the plate resistor in your first stage. Write that down. Look in Michael Percy's 2-2018 catalog, and find the closest DOUBLE the value Roderstein MK8 ( 2 Watt ) German film resistor. Order four, for both channels. Have Mr. Percy match them into two pairs, NOT to the rated value, but to their respective measured values, to each other ( get 'em at 0.01% or closer). These Rs are only $1.95 each, and the matching is a dollar more. Carefully, neatly, replace the existing stock plate resistor ( of your INPUT TUBE ) with these matched doubled up MK-8s, and LISTEN to what that does for your music enjoyment. You use a modded ST-70. You will hear it. You see folks, when we hear any tube amp, we are not just hearing the tube, but the tube in conjunction with its plate resistor. The INPUT tube is the most sensitive spot in the whole amp. The end result, will probably be far better sonics, than tube rolling alone, which is playing cards with half a deck, my analogy !! Michael is superb to deal with, $25.00 minimum order, easy to fill with all HIS goodies. Can you please point out what resistor(s) you're talking about? Quote Link to comment Share on other sites More sharing options...
MechEngVic Posted November 18, 2019 Share Posted November 18, 2019 18 minutes ago, Jeffrey D. Medwin said: The input tube. Pin 6 is the tube's plate resistor connection, and the resistor is denoted as R16 on the schematic, 270K Ohms, or 270,000 Ohms. Closest double-the-value stocked MK8 would be 549K. Two in parallel, will become 274,500 Ohms computed. That is about a 1.6% difference in theoretical R values .......surely CLOSE enough IMHO. The original part was likely a 2% or 5% 1/2 Watt part, especially when we compare that part's lack of designation on the schematic to the complete designation of R21 and R20 - of the tube's triode-section / phase splitter, (Pins 1,9,8 ). The second-most significant R -treatment possibility, would be to do something to the four 47K phase splitter Rs ( R21, R22). Alas, no MK8s exist close enough to parallel, and the fabulous Mills from Percy ( MR-200, 200K ) are 2 inches long, and well beyond this amp's need, from what I see. I was thinking about how to meaningfully make up your $25.00 minimum order. I would appreciate it if you did JUST R16 and listened, and share it with others on this Forum. I am sure, for example, that ALL the Dennis Had budget-priced "Inspire" amps would be excellent candidates. You get to be the known-to-all guinea pig, as I am new here, and not fully understood. If you have additional Qs, you can always PM me. Jeff Medwin Thanks for your answer, I'm going to do it. I'll report back. 1 Quote Link to comment Share on other sites More sharing options...
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