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Which tubes have the greatest sonic impact?

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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.....

 

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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?

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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.

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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?

I'd say, the "right" tubes, ........which develop the gain. 

 

A cathode follower stage has no gain, it acts a low impedance " driver" - to drive the interconnect cables, and next component down the line.  Yes, a cathode follower is certainly sensitive to tube choices, however,  if the first stage is "off", it's not going to correct and " make up" lost music information, that is never fed to it !!

 

The input tube ( of an amp or preamp ) develops the voltage gain, and it is most critical.  The input stage also amplifies the lowest level circuitry that that component ever "sees", which is the audio signal coming in.

 

Upgrading an input tube's plate resistor is also a easy and very nice thing to do - for added performance.   Tube rollers need to do that as the next very positive step !!!  Its a slam-dunk avenue of improvement.    I can advise how and what to do.  You are hearing not just the tube, but also, it's plate resistor. 

 

Jeff Medwin

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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.

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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+

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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.

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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.

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@canyonman Interesting. I'll have to do some looking into that once I've rolled a few from my vintage stash through it. Thanks!

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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....

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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.

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Tube rolling is interesting but, it has it's limits on fidelity.

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3 hours ago, MechEngVic said:

9743148.jpg.1fbfdff7b731be79b625d4828f63dca9.jpg

 

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.

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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?

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2 hours ago, MechEngVic said:

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?

 

 

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.

 

Please report back to all.   Doubled up / very tightly matched MK8s are unbeatable, price VS resultant audio performance, from what I experience.   Tell us ALL what you hear !!   No substitutions on R s, only use MK8s please !! 

 

 

Jeff Medwin

 

MK8.thumb.JPG.90ca3ec4bf47aab23e304d59c71c4fe0.JPG

 

 

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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?

ST70-II.thumb.jpg.6b7219c5c395f0410725f530d6459d34.jpg

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1 hour ago, MechEngVic said:

Can you please point out what resistor(s) you're talking about?

ST70-II.thumb.jpg.6b7219c5c395f0410725f530d6459d34.jpg

 

 

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. 

 

This is so much better, than just " tube rolling " alone.   Tube rolling alone, is like adding using a lovely Rolls Royce, along with a FIAT 500.   Lets have ourselves a Rolls and a Ferrari !   If you have additional Qs, you can always PM me. 

 

Jeff Medwin

 

 

 

1477833760_MR-20011-17-19.thumb.JPG.5be988735ea54fe0debd54f196bc852d.JPG

 

 

 

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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

 

 

2116271714_MILLSRs-Percy2019.thumb.JPG.a6da5b012bccd7e214ed8067038af8ca.JPG

Thanks for your answer, I'm going to do it. I'll report back.

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