The humble 12AX7 vs the lesser used 5751?

[Dood]

Ok, so it's a long and informative article by a chap called 'Joe S'. The main point of interest to me is that he goes out on a limb to say that for the Hifi gear he is using - he finds that the 5751 preamplifier valve is generally speaking a superior valve in terms of sound quality than a like for like (price -wise I guess) 12AX7. The 7025 isn't mentioned in the discussion - I suspect this is because the 7025 was meant to be a ruggedised and higher quality version of the 'standard' 12AX7 - then a..errr.. 'ruggedised and higher quality version' 12AX7 was brought in to manufacture.Thus making the differences less important. Anyway, I digress..

Here's the link : [url="http://www.audioasylum.com/audio/faq/joes-tubes.html#12AX7"]http://www.audioasylum.com/audio/faq/joes-tubes.html#12AX7[/url]

What I'd like to put out for discussion is whether or not those of you who enjoy a bit of tube rolling have anything to add as an opinion or advice. - I realise that this is an opinion of one guy, but do others share the same thoughts? I've not really seen much of a mention of the 5751 when it comes to bass gear to be honest - and it's gain isn't that much below a 12AX7. IIRC 12AX7 = 100, 5751 =70 and the 12AU7 is about 30? So would it be a worthy valve to roll with?

Anyway, read, digest, discuss!

[bigjohn]

All depends on yer gear doesn't it really?

And how much gain you want / need.

If you need less gain that's available from your gear and you're looking to tighten up your tone, or want to emphasise your mids, I'd swap em out and see how it goes.


I'm pretty sure (from memory and a quick a google) that JCM800s use ECC83s and they're gain monsters.

My SVT-IIP has 2 12AX7s in and hardly distorts even at extremities.

So I can't see either of these amps becoming better / more usable with a swap.

[Ancient Mariner]

The gain of a preamp is a function of both the gain that a given valve is capable of and also the actual preamp design. i.e. not every 12AX7 in every preamp will produce a gain of 100, and it may be as little as 30 or 40 or even less, depending.

OTOH different valves, even of the same type, sound different, let alone when you start swapping out different designs. I like the sound of 'lower gain' valves (12AT7s particularly) in preamps designed for 12AX7s - the tone can often be sweeter or more detailed, and with more headroom. Since bass doesn't generally rely on preamp overdrive for it's core tone then I'd suggest there's a lot to be gained by trying different valves, including the 5751.

Edited February 9, 2011 by Ancient Mariner

[voxpop]

[quote name='Ancient Mariner' post='1121328' date='Feb 9 2011, 01:21 PM']The gain of a preamp is a function of both the gain that a given valve is capable of and also the actual preamp design. i.e. not every 12AX7 in every preamp will produce a gain of 100, and it may be as little as 30 or 40 or even less, depending.

OTOH different valves, even of the same type, sound different, let alone when you start swapping out different designs. I like the sound of 'lower gain' valves (12AT7s particularly) in preamps designed for 12AX7s - the tone can often be sweeter or more detailed, and with more headroom. Since bass doesn't generally rely on preamp overdrive for it's core tone then I'd suggest there's a lot to be gained by trying different valves, including the 5751.[/quote]


I have had the same "the tone can often be sweeter or more detailed, and with more headroom" from the 5751. I liked the so much I have put them in my Rogue 88 power amp for hifi use.

I have ECC83's in the VOX V125b as I like the slight overdrive they can give with the volume knob on full. I tried 5751 and ECC81 but this cleaned the sound to much.

Edited February 9, 2011 by voxpop

[bigjohn]

[quote name='Ancient Mariner' post='1121328' date='Feb 9 2011, 01:21 PM']The gain of a preamp is a function of both the gain that a given valve is capable of and also the actual preamp design. i.e. not every 12AX7 in every preamp will produce a gain of 100, and it may be as little as 30 or 40 or even less, depending.

OTOH different valves, even of the same type, sound different, let alone when you start swapping out different designs. I like the sound of 'lower gain' valves (12AT7s particularly) in preamps designed for 12AX7s - the tone can often be sweeter or more detailed, and with more headroom. Since bass doesn't generally rely on preamp overdrive for it's core tone then I'd suggest there's a lot to be gained by trying different valves, including the 5751.[/quote]


Yeah - agree with the principle.

Just think that in the two examples I gave, that there wouldn't be much to gain (if you'll excuse the pun). The JCM needs low gain valves in the preamp - it's unruly enough. The SVT, although not reliant on overdrive for it's core tone, does start to break up if you push it... a feature which could be lost with a lower gain valve. That's not to say I wouldn't like to try some 5751s in my SVT for curiosity. Nor am I saying that with other amps - there wouldn't be a more logical benefit.

[Dood]

I'm encouraged by the replies so far! Thank you guys, keep them coming.

You have picked out a point that I purposely left out of the discussion in order to see where the responses went without influencing you! - overdrive/distortion. Nope, I don't want to use the valve to provide distortion.

Both preamp designs that I fancy rolling valves with are the "Fender/Alembic" design with the passive tone stack. Infact, I've been setting the controls to the typical 2-10-2 setting for 'flat-ish' response and using the EQ on my bass to boost and cut where needed. - It'd be just as well to have a bypass switch on the preamp for the tone stack! But I have to say I REALLY love my Hartke LH1000. The more I use it, the less I faff around with effects and EQ! - So I thought it'd be fun to see what effect different valves had on such a clean and simple design. Whilst searching the net for information I'd found the above article but nothing really to support the chap's opinions (so far, until now!)

One notable valve 'character' that I'd love to find out more about is the 'upward compression' or parallel compression effect. In simple terms, quiet sounds - i.e. light playing appears to be a lot louder through my preamp in ratio to loud sounds than if I bypass the preamp and plug directly in to the head's power amplifier. I also found this with my other valve preamp - the effect being even more pronounced when I took a DI feed post valve pre passive EQ. I like it - I like it alot! It's like compression - well - I it IS compression, but there is very little limiting of loud sounds, hence the 'upward/parallel' description. I feel this is what people refer to when they describe valve pre amplifiers as bringing out detail in music - because they are amplifying quieter passages in music much more and in a pleasing way Vs the more linear gain of a device such as a transistor/Op Amp.

So descriptions of a sweet tone and bring out detail in music certainly is what I am interested in - it'd be interesting to hear which valves have a more pronounced character to them that I describe above.

[voxpop]

One notable valve 'character' that I'd love to find out more about is the 'upward compression' or parallel compression effect. In simple terms, quiet sounds - i.e. light playing appears to be a lot louder through my preamp in ratio to loud sounds than if I bypass the preamp and plug directly in to the head's power amplifier. I also found this with my other valve preamp - the effect being even more pronounced when I took a DI feed post valve pre passive EQ. I like it - I like it alot! It's like compression - well - I it IS compression, but there is very little limiting of loud sounds, hence the 'upward/parallel' description. I feel this is what people refer to when they describe valve pre amplifiers as bringing out detail in music - because they are amplifying quieter passages in music much more and in a pleasing way Vs the more linear gain of a device such as a transistor/Op Amp.

This is why I started to use valves for bass playing.
I love the way they compress the sound giving a "bloom" or warmth to the bass, it sounds very natural to my ears. I no longer use a compressor pedal with valve amps........no need to with this natural conpression effect.

[obbm]

When I had a BBE BMAX-T pre-amp I changed to a 5751 in order to try and reduce the gain problems that I was having with active basses. Eventually the factory brought out a mod but I kept the 5751 as it sounded so much better than the supplied 12AX7. I then acquired an Alembic F1X and very swiftly swapped out the origninal valve for a 5751, and that was how it stayed through many gigs until I sold it. It was very deep and smooth.

I also tried a pair of 5751s in an Orange Terror Bass but it didn't make so much difference, so I kept the valves and sold the amp. One day I'll try them in the AD200B and see what happens. They are currently installed in Electro Harmonix English Muffn which has a revoiced EQ. Although the 5751s have more gain than the stock 12AY7s I think it sounds better.

I have some future valve projects and the 5751s will definitely figure in those.

[Dood]

Hey Dave! I was looking forward to having you chime in as I recalled that you had been fettling with the BBE and tried some different valves too - I've gotten my eye on maybe a few different pre valves just to play with and see how I get on. Interestingly, I think the article made some good points in conjunction with some other online resources that is pushing me towards certain types - mainly NOS.

@Voxpop funny you should say that! - I've been a huge fan of the TC Electronic Nova Dynamics compressor that give me the option of 'upward/parallel' compression - but everytime I have used the LH, the TC wasn't needed. One less box to carry, Dood is a happy man! - I guess I may still use it for boosting the volume of tap style stuff.

[geoffbyrne]

I've been suggesting on here for a while that if you're interested in valves you take time to look around here:

[url="http://www.guitaramplifierblueprinting.com/index2.html"]http://www.guitaramplifierblueprinting.com/index2.html[/url]

Myles Rose is an expert and can be freely contacted via the 'Feel Free to Ask Myles' thread here:

[url="http://forums.musicplayer.com/ubbthreads.php/forums/19/1/Guitar_Player_Forum"]http://forums.musicplayer.com/ubbthreads.p...ar_Player_Forum[/url]

Although most of this is aimed at guitars, it sits equally well with bass.

Now I'm no expert, but many who know say that the finest 'tone-producer' of all is the 5751. Having tried it against various other valves of the 12**7 type, I think I agree.

May I say that there are many so-called 5751s which are actually rebadged 12AX7s which have come up short of specs and are not real 5751s at all. There is a difference in plate configuration. I managed to get a pair od JAN Phillips 5751s recently and they sing beautifully - I have one in the V1 position of my guitar valve amp and I had the other in my Shuttle 6 up until I decided to put it up for sale. Both amps sound great.

Another important point often ignored in threads like this is the importance of a matched Phase Invertor.

This tube switches the signal from - to + & back again to go therough the power amp. It uses both sides of the valve. If each side has a different value the sound coming from the amp will sound rough, but if both sides are matched - or pretty damn near - then you'll get a nice smooth tone.

I have a matched ECC82 in mine - I bought a set of 4.

I also have, lurking in the drawer, an old Mallory ECC83 and a 4004A (military spec ECC83 made by Mallory) and yes, you *can* tell the difference when you put them up against the Russian & Chinese stuff around at the moment. They are much smoother & fuller. Although many will tell you the ECC83 & the 12AX7 are identical, Myles will tell you the European ECC83 has a mids-hump absent in US or Japanese 12AX7s, hence the 'British Sound' of ECC83s as opposed to the 'American Sound' of 12AX7s.

Swapping valves can be a lot of fun.

G.

Edited February 9, 2011 by geoffbyrne

[the_brow]

I use 5751s in all my amps except the GT200. The GT200 is low gain enough that the 12ax7 does not get all muddy and fizzy when you turn up the gain or push it with a pedal. However in any other 12ax7 amp I always swap in a 5751. I like the more clear tone, better mids and when pushed they add some grind wiouth the 12ax7 slopiness and harsh distortion. I have yet to find an amp where this swap did not yeild positive results. Even in the GT200 it sounded better but it just got too hard to get and OD out of the amp without overpowering the entire band

[Dood]

I'm liking where this thread is going! Thank you Geoff for the links, I've loaded them up now and will have a good read! I'd like to get my grubby little mits on a Sylvania Black Plate Gold Brand 5751 that one seems to stir the loins of the audiophile doesn't it! - I think that's the probable equivalent to Mullard/Telefunken ECC83/12AX7 nirvana!

[alexclaber]

When I had an SWR Grand Prix I replaced the 12AX7 with a NOS 5751. Here's what I said about it "I replaced the original tube with a NOS triple mica 5751. Less hyped highs, tighter lows, more transparent. Less gain though (as with all 5751s) so may not be suitable if your bass has a low output."

voxpop, have you ever tried a Class A discrete component preamp like an Avalon U5? That has a remarkable way of bringing out every last detail from your bass yet sounds even cleaner and smoother than the valve preamps I've tried.

[Mr. Foxen]

[quote name='geoffbyrne' post='1121585' date='Feb 9 2011, 05:15 PM']Another important point often ignored in threads like this is the importance of a matched Phase Invertor.

This tube switches the signal from - to + & back again to go therough the power amp. It uses both sides of the valve. If each side has a different value the sound coming from the amp will sound rough, but if both sides are matched - or pretty damn near - then you'll get a nice smooth tone.[/quote]

On the Peavey Windsor heads there is a knob that unbalances the phase inverter for that sort of distortion, so it might be desirable in some circumstances.

[Dood]

[quote name='geoffbyrne' post='1121585' date='Feb 9 2011, 05:15 PM']I've been suggesting on here for a while that if you're interested in valves you take time to look around here:

{snipped...}

G.[/quote]

Just realised that I have read a good few of Myles' blog posts before about valves! The internet in it's enormity can be so small sometimes!!

[geoffbyrne]

[quote name='Mr. Foxen' post='1121643' date='Feb 9 2011, 05:59 PM']On the Peavey Windsor heads there is a knob that unbalances the phase inverter for that sort of distortion, so it might be desirable in some circumstances.[/quote]


Ooooooooh! Didn't know that..... you learn something every day..........

G.

[voxpop]

[quote name='alexclaber' post='1121638' date='Feb 9 2011, 05:52 PM']When I had an SWR Grand Prix I replaced the 12AX7 with a NOS 5751. Here's what I said about it "I replaced the original tube with a NOS triple mica 5751. Less hyped highs, tighter lows, more transparent. Less gain though (as with all 5751s) so may not be suitable if your bass has a low output."

voxpop, have you ever tried a Class A discrete component preamp like an Avalon U5? That has a remarkable way of bringing out every last detail from your bass yet sounds even cleaner and smoother than the valve preamps I've tried.[/quote]


Hi Alex,
The u5 is on my list of things to try......does anyone have a u5 for sale?

[Dood]

[quote name='geoffbyrne' post='1121676' date='Feb 9 2011, 06:29 PM']Ooooooooh! Didn't know that..... you learn something every day..........

G.[/quote]


I've sent a message to chat with Myles Rose. He replied straight away and offered to field any questions, which I thought was a really kind gesture. Nice one Myles! He also suggested having a chat with Derek over at Watford valves too. I'm quite looking forward to learning a bit more about this we 5751 beasty and to see if it encapsulates the characteristics I am looking for. - Or see if I actually need a higher gain valve with say, a later break up to make use of that 'upward compressing' effect. We shall see!

[Soliloquy]

A friend of mine has an Alembic F1-X preamp. I remember spending a few hours with him one day experimenting with different valves. There was a noticeable difference between them. I just spoke to him and he thinks he settled on a Telefunken valve (great name !), He's going to take the top off and have a look see what sort.

I wonder if changing the valve in my Shuttle 6 would make it less aggressive sounding.

[umph]

[quote name='Mr. Foxen' post='1121643' date='Feb 9 2011, 05:59 PM']On the Peavey Windsor heads there is a knob that unbalances the phase inverter for that sort of distortion, so it might be desirable in some circumstances.[/quote]
most phase splitters compensate for the natural imbalance of the triodes.

Personally i go for JAN 83's in all my designs more is more and more is more better

[Owen]

There are so many options and I have so little clue. Is Watford valves the place to go? I fancy trying a 5751 in my Demeter.

Edited February 10, 2011 by owen

[nick]

[quote name='Soliloquy' post='1122461' date='Feb 10 2011, 11:48 AM']A friend of mine has an Alembic F1-X preamp. I remember spending a few hours with him one day experimenting with different valves. There was a noticeable difference between them. I just spoke to him and he thinks he settled on a Telefunken valve (great name !), He's going to take the top off and have a look see what sort.[/quote]

Telefunken ECC803S(?)
I've got a pair of Harma (cryo'd) made Telefunken ECC803S clones in my V-Type preamp. Love the tone, almost bell-like.

Edited February 10, 2011 by nick

[Dood]

Yeah, i'm a big fan of the Harma Diamond STR - They are a premium selected and tested JJ made ECC803S clone as you rightly say. Brilliant tone - I may end up with another, just fancied trying something a little different. Would love to find me a nice Tesla Short Plate E83CC!

[Dood]

[quote name='owen' post='1123397' date='Feb 10 2011, 11:25 PM']There are so many options and I have so little clue. Is Watford valves the place to go? I fancy trying a 5751 in my Demeter.[/quote]


Yes, one of the many - but Derek has always been helpful to me, so he's been my first port of call for new valves.

[umph]

[quote name='nick' post='1123409' date='Feb 10 2011, 11:36 PM']Telefunken ECC803S(?)
I've got a pair of Harma (cryo'd) made Telefunken ECC803S clones in my V-Type preamp. Love the tone, almost bell-like.[/quote]

you sure they're 803's? they have a different pin out. Great valves non the less though, worth a small fortune if you have some of the originals!