I gotta say... quite impressed with the 5751 preamp tube. My findings.

[RockStarNick]

So last night I decided to try out a NOS 5751 preamp tube. Did a little back to back comparison to a Tung Sol reissue. The amp used was the BMAN channel on an Egnater Mod50.

(***on a side note, despite to "complexity" and "tech" involved in the mod series, the Egnater stuff is very tube sensative, and really lets you hear the tonal differences and nuances from tube to tube very well...)

Compared to the Tung Sol, the 5751 had a big more presence, great crunch, great clean tones, great overall sound.

I've read that the 5751 "smoothed out" a lot of people's amp sounds. Whenever I read the word "smooth", I automatically assume "dull". Not so with the 5751. If it's possible for a tube to be bright, airy, and smooth, this is it.

I was probably the most skeptical because, at surface level, the 5751 seemed like leftover, low-gain 12AX7s that no one wanted, and some dude started some marketing hype that they're a huge secret.

Even if that IS the case, it still is a great sounding tube, either way.

I also thought it sounded pretty darn good in the PI spot as well. Compared to a particular JAN 12AX7, the AX sounds almost too "solid" sounding. Like it won't give, or crunch. The 5751 sounds full, but more detailed.

Again, YMMV.

[59Vampire]

The 5751 is a very interesting tube in my opinion. While it has alesser gain rating than a 12ax7, In some I applications, I find that it gives a warmer, if not fuller distortion like you had experienced.

[Blue Strat]

Knowing what brand of 5751 you used would be very helpful.

[RockStarNick]

Ah, sorry mike!!! almost forgot!

It was a JAN Philips 5751, I'm 99% sure...

[RussB]

If you like the JAN 5751's, wait 'till you try a GE 5-star!

[ScottR]

I use the Jan Phillips 5751 in my Bogner Shiva and my Peavey Classic 50 in the V1 position. Awesome Tube

[RussB]

I ran 3 JAN GE 5751's in my Mesa MKIII. They were toneful and quiet. :)

[Structo]

5751's have a gain of around 70mu compared to the 100mu a 12ax7 has.
So sometimes less gain is confused with better tone, and it may well be it sounds better with a little less grind.

[flythair1]

Right On Russ!!

I built a AX84 SEL (single ended PA) and it calls for two 12AX7s. It sounds good that way but with lots of early gain. I tried out all of the 12A?7 types and settled on a GE 5 Star 5751 for V1 and a GE 5 Star 6072A for V2. W O W ! !

There is a lot of diff with preamp tubes and experimenting with your own amps can be quite enlightening. Yea on the 5751!!

Scott

[SoCalSteve]

Interesting. I was just reading about the 5751 in Hunter's Guitar Amp Handbook for taming preamp distortion. I think I'll try one in V1 of my Palomino V50. Thing's got gobs of gain - AC/DC crunch at 9:00.

[stratman_el84]

+1 on the 5751!

Great-sounding tube. That's what I use as a preamp tube in my Testament MK-I amps I'm building (pic in my sig below) with two cathode-biased EL84's and a 12AX7 PI.

I struggled with the preamp design at first. I tried a standard preamp stage, but not enough oomph to push the PI after the volume & tone controls. Then I went to two triode stages in series, but no matter what I tried, it was way too much. Then a parallel-triode design, bit it still wasn't "right".

I then tried an SRPP (Shunt Regulated Push-Pull) preamp design. It was close. It would push the tone control/volume enough to drive the PI, but had too much gain.

I finally tried a 5751 in the SRPP, and voila!! :bender

I know an SRPP is usually seen in hi-fi and studio preamp applications, but the output impedance of the SRPP into the volume and tone control section combined with with the gain of the SRPP tamed with the 5751 is magic in this amp. Beautiful chimey cleans at usable volumes, smooth transition into breakup, and fat overdriven tones with great detail & articulation through the entire range.

I get those little chills every time I play through that amp! :love:

Now I've just gotta figre out how to get some more finished, as almost every time I gig with this thing there's another player asking about it and how much I want for it! :rotflmao

I won't sell this one, as I just couldn't stand now to play out without it! :p


Strat

[harryjmic]

Less gain should end up reducing the midrange push you get from the amp so it would make sense that people think the clean tones are better. In amps that already have weak mids I think 5751's are a bad idea as they pull even more mids out.

Where they make a lot of sense is in tweed amps or in my case now a Carr Vincent. The Carr has a lot of midrange and I am dabbling with 5751's to reduce the mids a bit. I need to record some clips this weekend to find out what setup I like better.

I would also think that since there is less front end push the amp might respond better to pedals because your not redlining the preamp so to speak when using a 5751. These seems valid in theory but I am not sure if it's applicable.

[jcarpenter]

Hell, try a high quality at7 like a JJ gold pin or an NOS RCA if you can find them and don't mind the price.

[rockon1]

Knowing what brand of 5751 you used would be very helpful.

+1 Saying I like 5751's is kind of like saying I like newspapers...

[Doug's Tubes]

Hell, try a high quality at7 like a JJ gold pin or an NOS RCA if you can find them and don't mind the price.

No one should waste any $$ on preamp tubes with gold pins, they have NO effect on tone one way or the other.

[Prairie Dawg]

No one should waste any $$ on preamp tubes with gold pins, they have NO effect on tone one way or the other.

they have a good effect on the fellow who's selling them, you have to admit.

[SoCalSteve]

I went ahead and ordered a JAN Philips 5751 to try out in V1.

[Jason Myers]

I used to run one in V1 of my Soldano to tame some of the gain. It also opened up the amp alot. Great sounding tubes imho.

[slartibartfast]

Psssttttt...............just between you and me ---------sylvania

[rockinlespaul]

If you like the JAN 5751's, wait 'till you try a GE 5-star!

I got a bunch of those 5 stars. I need to try them.

[vandi]

1950's GE 5 Star 5751s with the black plates, triple mica, and square getter are wonderful. I have one that Ken installed in V1 of my Komet 80 and I have yet to find another tube for V1 that sounds as beautiful. I have heard great things about the gold logo Sylvania, black plate RCA, and black plate Raytheon. 1950's 5751s with black plates and triple mica seem to have that special sauce. Too bad they are jumping in price due to the increasing demand by HiFi users.

[go7]

Interesting thread. I have been using nos 5751 for over 20 years. I agree they are a wonderful tube. I bought about 30 RCA 5 star black plates long ago. I have a standard reply for my friends who are not quite comfortable w/ a 12ax7 in v1. "Put a 5751 in V1 and call me in the morning". A few good 5751 should be in any tube enthusiast collection box. Good luck.

[Primakurtz]

I run 5751's in the PI position, leaving a 12AX7 in V1. Best of both worlds, to my ear, both for Marshally and Fendery amps. Good gain, more control over it, and a little less noise.

[mmorse]

I like the RCA Command Series 5751s. Very Mullard like in its overall tone.

[Timbre Wolf]

I like the RCA Command Series 5751s. Very Mullard like in its overall tone.
:huh

What does "Mullard like" mean? Mullard never made a 5751. More to the point: can you elaborate on what you mean by "Mullard like," and how the RCA Command 5751 (black or gray plate?) seemed similar? Just curious for details. Thanks.

- Thom

[INX]

:huh

What does "Mullard like" mean? Mullard never made a 5751. More to the point: can you elaborate on what you mean by "Mullard like," and how the RCA Command 5751 (black or gray plate?) seemed similar? Just curious for details. Thanks.

- Thom

+1. Waiting. I have two of these.

[johnhenry]

+++! If you own a brown Deluxe (or similar sounding amp), give the 5751 a try. It turns it into a different animal. Full, rich OD and great pick attack.

[Tomo]

I am very happy with my NOS GE 5751, RCA 5751... very deep full tone!

Tomo

[pennylink]

Does anyone know what the sound difference is, if any, between JAN Philips 5751 with regular print v blue or green print? I noticed they seem to be priced differently...

[Prairie Dawg]

:huh

What does "Mullard like" mean? Mullard never made a 5751. More to the point: can you elaborate on what you mean by "Mullard like," and how the RCA Command 5751 (black or gray plate?) seemed similar? Just curious for details. Thanks.

- Thom

If I had to take a SWAG on this subject (Scientific Wild A** Guess);) I'd say that tubes that are really stable have their own clean tone, but that's a byproduct of their stability. Mullards were used in a lot of test equipment that used bridge circuits, as were Telefunkens. I've got one here that's pretty much my reference preamp tube because it's very stable and quiet.

In many cases the makers of test equipment would sell you a selected tube for your VTVM or scope, but you could find one yourself. I think my RCA VTVM required a 36 hour burn in before attempting calibration.

Of course that's all a guess. Sometimes I wander off the reservation.

[Timbre Wolf]

If I had to take a SWAG on this subject (Scientific Wild A** Guess);) I'd say that tubes that are really stable have their own clean tone, but that's a byproduct of their stability. Mullards were used in a lot of test equipment that used bridge circuits, as were Telefunkens. I've got one here that's pretty much my reference preamp tube because it's very stable and quiet.

In many cases the makers of test equipment would sell you a selected tube for your VTVM or scope, but you could find one yourself. I think my RCA VTVM required a 36 hour burn in before attempting calibration.

Of course that's all a guess. Sometimes I wander off the reservation.
Pretty sophisticated SWAG, Dawg - at least for rock 'n' roll purposes. But it's plausible. Only mmorse knows what he meant by "Mullard like." I just like to find out more about people's subjective experiences, with detailed descriptions.

The word "Mullard" is a magical thing, part of our cultural dreamtime, and it makes a lot of people around here twitch with some kind of mythical ecstasy - even if it is emblazoned on a Russian tube! I'd like to suss out what it means to the collective psyche, and start by summing up individual subjective impressions.

If I had to assign a single adjective to the vast array of Mullard valves I've tried in guitar amps, I'd say smooth.

- T

[pennylink]

Does anyone know what the sound difference is, if any, between JAN Philips 5751 with regular print v blue or green print? I noticed they seem to be priced differently...
Tube afficionados, bump for this question :)

[Timbre Wolf]

Tube afficionados, bump for this question :)
Paint color is not a consistent indicator of structural, chemical, or metalurgical changes inside the tube (the real reason for character differences).

- T

[SoCalSteve]

I tried the JAN Philips 5751 in two amps V1 slots - a 5E3 clone and a Palomino V50 EL34 amp. To my ears it dulled the tone of both of them.

Maybe this is why the Philips seem to be more readily available and cheaper?

[hdahs143]

I tried the JAN Philips 5751 in two amps V1 slots - a 5E3 clone and a Palomino V50 EL34 amp. To my ears it dulled the tone of both of them.

Maybe this is why the Philips seem to be more readily available and cheaper?

I'd be interested to hear if you had the same results with different brand 5751's.

In general they do seem to smooth the top end a bit, but my smooth may be your dull.

The JAN's in particular are built to military specs, and are generally well matched between the triodes. I've got a JAN Phillips in the PI slot of my Clubman, and it's easily the best tube I've tried in that spot, both new and NOS. Of course YMMV.

I love 'em!:drool

[Dawg76]

Using an NOS JAN Phillips 5751 in V1 of a Billm-modded Blues Junior. Made this amp take an overdrive pedal much better. Sounds great.

[sidehatch]

Im loving RCA 5751's in V1 and V2 of my Carr slant 6-the clean channel.

I did not like them on the lead channel.

[Jahn]

RCA 5751 in V2 of my Pro Reverb, nice warm cleans but still clear, no mud - plus, the OD from the preamp isn't harsh at all for a blackface amp, good stuff. The same RCA 5751 also worked great in a BK Butler Tube Driver rackmount I had.

[bluesjuke]

I tried the JAN Philips 5751 in two amps V1 slots - a 5E3 clone and a Palomino V50 EL34 amp. To my ears it dulled the tone of both of them.

Maybe this is why the Philips seem to be more readily available and cheaper?


If your 5E3 had the proper tube compliment you increased the gain with the 5751.
The opposite of what the OP did.