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6SN7 Substitute for 5670 - Request Insights

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Posted on June 20, 2024 at 10:51:58
svisner
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Joined: March 30, 2002
Contributor
  Since: March 30, 2002
 This topic has likely been covered but I would grateful for insights regarding substitution of 6SN7 for 5670 preamp tube. Anything to expect? Anything about which to be concerned? Grateful for other Inmates' thoughts and counsel.

 

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if your circuit and power supply can support the 6SN7 its possible, posted on June 20, 2024 at 13:07:03
Chip647
Audiophile

Posts: 2699
Location: The South
Joined: December 24, 2012
 But they are very different tubes with different operating points, different gain, different heater current. If this is to plug into a little headphone circuit board, plug away. If you have a more traditional "audiophile" piece of equipment I would not automatically lean into the "designer was an idiot" that did not know about the magic 6SN7 tube.

 

6sn7 has a mu of 20, 5670 has a mu of 35 so the 6sn7 will have less gain., posted on June 21, 2024 at 15:51:28
Tre'
Industry Professional

Posts: 17587
Location: So. Cal.
Joined: February 9, 2002
 Not a lot less but less.

my comments assume that the circuit was going to be redesigned for the 6sn7.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: 6SN7 Substitute for 5670 - Request Insights, posted on June 22, 2024 at 08:18:06
Palustris
Audiophile

Posts: 2436
Location: Cape Cod
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 The 5670 is a high quality modern tube released about 1955 and made by many of the best tube producers such as Tung Sol, RCA, Ericson (2C51) and Western Electric (396A). It has a different plate resistance, transconductance and amplification factor than the 6J5/6SN7; a higher performing tube with much greater transconductance and lower plate resistance.

As such, the 5670 has very different operating points, so that a 6SN7 plugged into a circuit (with an adapter) intended for a 5670, will give very unsatisfactory performance. So any competently engineered circuit using the 5670 should be very high quality. It would be a mistake to seriously degrade the performance by inserting the wrong tube.

 

I wouldn't have guessed that anyone would...., posted on June 22, 2024 at 08:47:22
Tre'
Industry Professional

Posts: 17587
Location: So. Cal.
Joined: February 9, 2002
 substitute a 6sn7 for a 5670 without redesigning the circuit first.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: I wouldn't have guessed that anyone would...., posted on June 22, 2024 at 09:15:26
Palustris
Audiophile

Posts: 2436
Location: Cape Cod
Joined: September 12, 2008
 Since there is an adaptor for it on epay, the assumption is that it will work without any redesign. Other specious assumptions are: my preamp has too much gain with a 12AX7 so I will put in a 12AU7 for less gain. It seems that Gm and Rp are not even considered relevant.

 

RE: 6SN7 Substitute for 5670 - Request Insights, posted on June 22, 2024 at 11:35:13
svisner
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Contributor
  Since: March 30, 2002
 Thanks.

 

RE: 6SN7 Substitute for 5670 - Request Insights, posted on June 22, 2024 at 11:38:23
svisner
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 Here is the reason for my curiosity.

 

That link doesn't work for me. nt, posted on June 22, 2024 at 12:31:45
Tre'
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Posts: 17587
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 .
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: I wouldn't have guessed that anyone would...., posted on June 22, 2024 at 12:38:18
Tre'
Industry Professional

Posts: 17587
Location: So. Cal.
Joined: February 9, 2002
 As you know, those are some really bad assumptions.

There are manufacturers that claim their power amps can use all the different beam power and power pentode tubes but that is nonsense.

If the amp is optimized for any one of those tubes, it will not be for the rest.

As for gain stage tubes. Pretty much the same thing. Even if you can plug a 12ua7 into a circuit designed for a 12ax7 without it blowing up it doesn't mean you should. Unless you don't care about distortion (or maybe you are looking for distortion?)

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

Depends on the circuit, posted on June 22, 2024 at 15:49:32
Triode_Kingdom
Audiophile

Posts: 10189
Location: Central Texas
Joined: September 24, 2006
 I'll go against the consensus here (which I don't disagree with in a general sense) and say that it's possible a 6SN7 could work well in a circuit originally using a 5670. It all depends on the circuit configuration and component values. The thing is, there's more than one operating point that's likely to be satisfactory for a given tube type. If that wasn't true, manufacturers wouldn't provide multiple operating points in their data sheets, and every designer who wanted to use a specific tube would be hamstrung with a very specific set of parameters. The bottom line is that no one can answer your question intelligently without knowing the circuit it's used in.

 

Well, if he's looking for distortion..., posted on June 22, 2024 at 16:02:42
1973shovel
Audiophile

Posts: 10197
Location: Greenville SC
Joined: February 25, 2007
 ...the 12AU7 is certainly the place to find it! I think back on how many times I glossed over your (as well as Eli Duttman's, among others) posts about the non-linearity of the 12AU7.

Meanwhile I was trying different coupling caps, improvements to the power supply, even different resistor types to try and coax some music out of my ST-70 with a 12AU7 circuit.

Then one day, after reading one of your posts about the clear superiority of the 6CG7 for who knows how many times, I finally paid attention. But rather than cutting board traces, and since I already had a few 6SN7s, I bought an 12Au7 socket to 6SN7 tube adapter to try in the circuit's voltage position. After so many previous disappointments I wasn't expecting much, but couldn't quite get over the level of improvement. I could finally listen to this amp for musical pleasure.

When I think of how much time, money and frustration I wasted, when the problem was the 12AU7 in the gain position all along. Ugh! What an awful tube to use for amplification.



 

RE: That link doesn't work for me. nt, posted on June 22, 2024 at 16:19:38
svisner
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Posts: 1224
Joined: March 30, 2002
Contributor
  Since: March 30, 2002
 Text from link - a reviewer of the Aiyima T8 preamp/DAC: "I got this for Schlitz and Giggles. It's not going win awards for epic sound quality. I was surprised though! I love it for 70s, 80s, and 90s music. It reminded me of what our stereo growing up sounded like in those decades. Instant nostalgia and endless fun.

"I did get the wild brain idea of using a 5670 (T8 socket) to 6ns7 tube converter. Using PSVANE UK 6NS7, added more fullness to the lower end and air to the treble."

 

Picture of Circuit Board, posted on June 22, 2024 at 16:23:54
svisner
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Posts: 1224
Joined: March 30, 2002
Contributor
  Since: March 30, 2002



Image attached.

 

Yep! nt, posted on June 22, 2024 at 16:52:04
Tre'
Industry Professional

Posts: 17587
Location: So. Cal.
Joined: February 9, 2002
 .
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Picture of Circuit Board, posted on June 22, 2024 at 21:05:15
Triode_Kingdom
Audiophile

Posts: 10189
Location: Central Texas
Joined: September 24, 2006
 Can't tell anything from that. It would require a schematic with component values and at least the plate supply voltage to make a reasonable determination.

 

Simpler problem, posted on June 27, 2024 at 11:31:44
Chip647
Audiophile

Posts: 2699
Location: The South
Joined: December 24, 2012
 A 6SN7 is a fairly large tube compared to the stock tube and coupled with an adaptor on its base it is unlikely to fit in its chassis.

On top of that, the tube is most likely just used as an output buffer/cathode follower which has very little impact on sound between tubes.

 

RE: That link doesn't work for me. nt, posted on June 28, 2024 at 08:06:42
Palustris
Audiophile

Posts: 2436
Location: Cape Cod
Joined: September 12, 2008
 Eric Barbour in Vacuum Tube Valley tested a huge array of 6SN7 tubes and compared them to several other tube types, just to put the 6SN7 in context. These tubes were listed in increasing percentage of 2H distortion. I found it interesting to see that he found the best 76, 5687, 6CG7, 12SX7, and 396 (5670) as having lower distortion than the best 6SN7.





 

It is best to read the whole article., posted on June 29, 2024 at 07:38:03
Tre'
Industry Professional

Posts: 17587
Location: So. Cal.
Joined: February 9, 2002
 .
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: It is best to read the whole article., posted on June 29, 2024 at 09:18:52
Palustris
Audiophile

Posts: 2436
Location: Cape Cod
Joined: September 12, 2008
 Sorry about the link. It is an excellent article for those interested in the 6SN7. Personally I use the EC86, EC8010, 76, 5687 and the 6F8G in my amps. I used the 5670 in Eli Duttman's "El Cheapo" inspired amp. I gave all my 6SN7s to a friend a decade or more ago, since I thought millions were made, they will never be scarce. It turns out the best ones are scarce.

 

Anyone heard from Eli Duttman on any forums lately?_nT, posted on June 29, 2024 at 19:05:10
Cleantimestream
Audiophile

Posts: 7581
Location: Kentucky
Joined: June 30, 2005
 !
The Mind has No Firewall~ U.S. Army War College.

 

RE: 6SN7 Substitute for 5670 - Request Insights, posted on July 18, 2024 at 21:47:12
svisner
Audiophile

Posts: 1224
Joined: March 30, 2002
Contributor
  Since: March 30, 2002
 Well, I did it. Hope to report.

 

RE: 6SN7 Substitute for 5670 - Request Insights, posted on July 20, 2024 at 12:52:19
svisner
Audiophile

Posts: 1224
Joined: March 30, 2002
Contributor
  Since: March 30, 2002



So far, so good. Had to find an adapter with a collar narrow enough to allow me to engage the socket below the top plate. I find the sound open and detailed using a JJ 6SN7 tube. No, I can't say certainly what difference, if any, I detect versus the stock 5670 tube. Gain is not as reduced as I feared. I think I prefer the soundstage just a bit with the new arrangement, but it could also be my imagination. However, the larger and taller tube certainly looks neat on the little Aiyima T8. I think it all sounds quite nice.

 

RE: 6SN7 Substitute for 5670 - Request Insights, posted on July 20, 2024 at 13:46:45
Mendel
Audiophile

Posts: 1224
Location: GTA
Joined: January 17, 2009
 If you like the sound with a JJ 6SN7, I think you would be thrilled with a good vintage 6SN7, say an early Sylvania (W, WGT or WGTA or VT231 or 1952 Badboy)

 

RE: 6SN7 Substitute for 5670 - Request Insights, posted on July 20, 2024 at 18:35:29
svisner
Audiophile

Posts: 1224
Joined: March 30, 2002
Contributor
  Since: March 30, 2002
 Thanks. Might try one. Listened today to an open reel prerecorded tape. Barclay-Crocker. Alfred Brenden. Beethoven Choral Fantasy and Piano Concerto No 2. Superb imaging and detail.

 

RE: Simpler problem, posted on July 26, 2024 at 06:31:32
svisner
Audiophile

Posts: 1224
Joined: March 30, 2002
Contributor
  Since: March 30, 2002
 It did fit, just.

 

RE: Anyone heard from Eli Duttman on any forums lately?_nT, posted on July 29, 2024 at 13:06:45
Tre'
Industry Professional

Posts: 17587
Location: So. Cal.
Joined: February 9, 2002



No.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

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