Assuming equal quality of manufacturing and amplification factor, can anyone hear the difference between an octal and a 9 pin preamp tube?
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Octal or 9 Pin Preamp Tubes
- Thread starter KenD
- Start date
Is not this is just the different connector? Not clear about the question. I would say the tube itself can make some tonal difference, but not the connector.
Are you asking a difference between 2C52 and 12ax7?
I think this is a woodlistener debate. I would stick with 9-pin type tubes as they are easier to find.
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Well, to be more precise take the example of Sylvania Gold Brand 5751 (9 pin) and 6SL7WGT (octal). Both were manufactured in the same plant, using the same enhanced materials and manufactured to US military specs.
One would expect that the different size and shape of the interior components of the two tubes would have some effect on the tonality they impart. Or not? My question is simply does/has anyone heard any difference in similar circuits. Direct A/B comparison is difficult or impossible because I don't know of any amp that has interchangeable 9 pin and octal preamp tubes.
I ask this because I am trying to decide between two very similar amps, both using the same output tubes but one set up for 12AX7 and the other for 6SL7GT preamp tubes: Frenzel Mini-Bassman and Retro Deluxe Plus 5A3.
https://www.frenzeltubeamps.com/mini-bassman
@Passinwind has rolled 6SL7 and also has designed preamps that use this tube. Perhaps he can provide some useful guidance.
@juledude works with 6SL7 as well.
My two cents:
I can hear a difference between 12AX7 variants; so I would definitely expect a difference between 12AX7 variants and 6SL7 variants. A 12AX7 combination I frequently like in bass amps is a current production Mullard ECC83 in V1 and a JJ ECC803S everywhere else. You might think this combination sucks!
Tone is subjective. The best thing you can do is demo both amps and use your own ears.
It is highly unlikely that anyone has compared side by side. One would have to modify their amp to be able to switch tubes with different connectors. That is too much of an effort for something that is irrelevant. Effect of preamp tube on the tone of an amp is rather minor hence my reference to "woodlisteners".
Comparing two different amps on tone and speculating that the tone difference attributed to the preamp tube is comparing apple and oranges, then attributing difference in taste to the color of the seeds inside the fruit.
I would say watch/read some reviews on line, play through in persone if possible and pick based on what you like more, not the tubes type.
That said, you can post this in Amplifiers section. This is where you can get opinions on the specific amplifiers. This section of forum is about pickups and in-bass electronics, not really the actual amplifier rigs.
Comparing two different amps on tone and speculating that the tone difference attributed to the preamp tube is comparing apple and oranges, then attributing difference in taste to the color of the seeds inside the fruit.
I would say watch/read some reviews on line, play through in persone if possible and pick based on what you like more, not the tubes type.
That said, you can post this in Amplifiers section. This is where you can get opinions on the specific amplifiers. This section of forum is about pickups and in-bass electronics, not really the actual amplifier rigs.
I too can hear a tonal difference between different 12A*7 variants and different makers of same; I am most familiar with them. However, my current main amp is running 6SL7 into KT66 and to my ears that amp has a much larger and more open sound than what I remember from various 12A** amps I have played.
I suppose I am just looking for assurance that I'm not fooling myself about a difference that doesn't exist. Does it matter? If I think there is an agreeable difference then there IS one for my purposes (non gigging, non recording).
PS: I can't demo them because they are custom built to order.
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Check out the various models of Little Walter steel guitar amps. Phil makes octal and 12AX7 preamp amps models, 6L6 and 6V6 output tubes. The Little Walter 89 (100 watts, 12Ax7 and 4- 6L6 tubes) makes a very good bass amp for smaller gigs such as jazz, standards etc., especially for upright. Obviously a bass cabinet is necessary. I use one or two Bergantino 12” caninets
Passinwind
I know nothing.
- Dec 3, 2003
- 23,077
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- Designer/Toaster Tech @ Passinwind Electronics
When I'm designing tube widgets I tend to look at the operational curves used to derive the load line, not how many pins are in the base.
Interesting - but it doesn't answer the question of whether they produce any difference in tonality.When I'm designing tube widgets I tend to look at the operational curves used to derive the load line, not how many pins are in the base.
Passinwind
I know nothing.
- Dec 3, 2003
- 23,077
- 46,033
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
All things are never equal, so it just depends. But I can confidently say that most people have preferred my 6SL7 based preamps to any others I've built for bass guitar applications.
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I have a custom guitar amp that can use all the common 12A_7 and 6S_7 choices. I haven't tried the 9 pins in it cause I'm just perfectly happy with how it sounds now. I probably have some sort of vintage option in there, if I know me...
So I could test it through a bass cab, I suppose. Now that I think about it, it could be a nice amp for recording bass. 2x6V6 in a single ended parallel circuit and dual tube rectifiers is pretty touch responsive with a super intact transient. Low end won't kick you but it could be cool...
So I could test it through a bass cab, I suppose. Now that I think about it, it could be a nice amp for recording bass. 2x6V6 in a single ended parallel circuit and dual tube rectifiers is pretty touch responsive with a super intact transient. Low end won't kick you but it could be cool...
The responses received here and this quote kind of confirm what I think my ears hear:
"While all the Vintage American Series 8 amps have the dynamic response that octal tubes are known for this amp [Little Walter 44] goes way beyond... There is some magic in mating a pair of octal preamp tubes to 4 6V6 power tubes." - Phil Bradbury, Little Walter Amplifiers
Thank you for the feedback
"While all the Vintage American Series 8 amps have the dynamic response that octal tubes are known for this amp [Little Walter 44] goes way beyond... There is some magic in mating a pair of octal preamp tubes to 4 6V6 power tubes." - Phil Bradbury, Little Walter Amplifiers
Thank you for the feedback
Octal preamps definitely have a sound. They're one of the main reasons guitarists seek out old Gibson, Supro, Valco, etc. amps. There are also modern builders like Vintage 47 making octal amps. I use the Vintage 47 VG-185 for my jazz guitars. If you're into players like Charlie Christian, Django Reinhardt (late period), or Junior Barnard a cooking octal preamp is a big part of their sound.
I've never heard of bassists paying much attention to them though.
I've never heard of bassists paying much attention to them though.
In order to do a true a/b comparison, you’d need a circuit built with both kinds of sockets, so you could eliminate most of the variables. Of course, in doing that, you’d add some parasitic capacitance, which would likely swamp any small differences in the tubes. One of those things where we’ll never know for certain, but any differences are likely vanishingly small.
Classic guitarist answer. They were used only in the most recorded and famous bass amp of all time the Ampeg B-15 which is still to this day the studio standard.
Well yes obviously. However there is really no market for octal tube based preamps, either as a standalone unit or paired with a tube power amp, in the bass world. Even in the guitar world it's a niche within a niche. Most of the posts in this very thread illustrate how little bassists pay attention to, or care, about it. And the B15 is hardly the industry standard at this point.
Not sure why you're trying to throw shade at me with the guitarist comment but you do you, champ. Just trying to offer some perspective/help to OP.
Which guitar amps are you interested in? Most amps on the market using octal tubes are geared towards replicating tones of the 30's & 40's so they tend to be rather low wattage ~12-15w and break up very early. I primarily play six string basses. I've never plugged a bass into the Vintage 47 amp but I imagine it would sound great up to the point of edge of breakup and a little beyond depending on your goals. I'd love to see someone release an octal bass preamp pedal or rack unit, maybe it already exists in the form of a B15 clone.
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Jul Monique is highly regarded by many TB members. Monique runs two 6SL7GTs, one 12AU7, and a 6CA4/EZ81 rectifier.
You can buy Monique as a stand alone pre or integrated with a 700W class D power module. AFAIK Jule does not package Monique with a tube output section, but I am sure it would drive a tube power amp just fine.
I believe Jule used to make some low powered (all-tube) guitar amps. AFAIK his webpage currently appears to offer solely bass gear.
