New Tube Day (NOS JAN Philips 5751)

[wakjob]

V1 drives everything. A 5751 is similar to a 12AX7 but in V1 it will lower the gain stage. You won’t get much more headroom because it’s too similar. You need a 12AT7 before you will really notice a noticeable difference in headroom. But overall ratio of preamp to power amp dirt is lower.

Changing the phase inverter tube type will change the percentage of how much preamp signal is passed to the output stage. So it has a more dramatic effect in taming an amp. You get less power tube section distortion at higher preamp gain, so that gain is more useful. Usually on a 5150 anything past 7 just gets muddy and feeds back. This allows usable gain to 10. And it’s less distorted on the power tube side so it’s more articulate sounding (like a German amp?). A 5751 there lowers how hard the power tube section is hit by 10-30% and a 12AT7 by 20-40% (based on contrasted brands gain factors) IIRC.

Yeah, I have piles of tubes of every kind...CP & NOS.
Got some nice old Mullard X2f's el34's I've been saving for a future build.

My memory is fuzzy on the 5150/6505 schematic,
I though people were looking to lower the amount of gain JUST for the the drive channel and not to globally affect the amps sensitivity.

I do remember about ten years ago many 5150 owners
were hunting down old Black Plate 5751's for either v2 or v3.
Again, strictly to have an effect on the drive channel...soley.

 

[JesperX]

Most of my experimentation has been around V1 through V3. I've only ever replaced the PI as a means of keeping a fresh tube in play. Are there any tubes you can recommend to help get a more compressed feel out of a Mesa Rectifier?

What's in there now? I was just rolling everything I have through my new 5150 III 50w - various 12AX7s and JJ 5751s. Interestingly enough I liked my old Mesa Russian 2's best, which are Electro-Harmonix 12AX7s. It kept the amp tight without driving the power section into farting out.

In general, lower gain tubes will have a more dynamic feel and higher gain tubes will have a stiffer, more compressed feel... up to a point. If you hit it too hard, the power section will start to fart out and then things get weird. I had that happen when I accidentally ordered a Sovtek LPS with the high gain option. It was measuring 110/115 and man it sounded awful in my 6505+ PI slot.

So you want something with higher gain to get more compression there, but it depends on what's in there now. The most standard answer though would be a Sovtek LPS. People will swear up and down about the matched triodes thing, but I'm not buying it. I've shot out 8 different tubes in the PI slot and only one or two were matched. The only differences I'm hearing correlate with gain differences.

 

[KailM]

I think I found a permanent home for this tube now — V4 of my 5150 III 50-watt head. That’s the first tube dedicated to the green and blue channels, other than V1.

I have to admit, I’ve never enjoyed the blue channel near as much as the red channel, which is the opposite of what most people say. With this tube in V4 though, the blue channel definitely has more complexity and harmonics in the midrange. It sounds more like a classic Marshall, in other words, and that’s A-okay in my book. The cleans are a little cleaner too, not that they really needed it. It now sounds like I have three very distinct channels, whereas before, the blue channel just sounded like a neutered red channel.

 

[KailM]

I use the JJ 5751 in several of my high gain amp PI slots and it's glorious. I paid for Tubedepot to test them to ensure low microphonics and low noise and I still think they were only $20 each?

Unlike KailM above, I really like the 12AT7 in the PI slot of my 5150 212 combo. It actually sounds more like my KSR Ares than a 5150 right now. Chugs for days!

5150s (and variants) just really love JJs. Other tubes sound better in my other amps, but I always come back to JJs with these amps.

Bottom line... if you have a 6505 you need to change out the stock tubes if it still has them. Peavey uses (or used) garbage ones stock (I haven't seen what they are currently shipping with).

Thanks to this post, I tried my JAN Philips 12at7 in the phase inverter slot of my 6505 today. You’re not kidding— the chugs are unreal!

 

[USMarine75]

Thanks to this post, I tried my JAN Philips 12at7 in the phase inverter slot of my 6505 today. You’re not kidding— the chugs are unreal!

J/K!

I had an ABY rig with my 5150 and KSR Ares and honestly people thought the 5150 was the KSR! You can still turn it up and get the typical brash throaty 5150 tone, but turn that gain to 5 or 6 and it is glorious articulate chuggs for the Architects type stuff.

 

[mnemonic]

J/K!

I had an ABY rig with my 5150 and KSR Ares and honestly people thought the 5150 was the KSR! You can still turn it up and get the typical brash throaty 5150 tone, but turn that gain to 5 or 6 and it is glorious articulate chuggs for the Architects type stuff.

Was there any volume loss with the 12at7 PI? I’ve been tempted to try one in my recto but I never got around to buying one. Not sure what to expect, I think I saw online a couple people saying they liked it in the Recto, but that’s it.

 

[USMarine75]

Was there any volume loss with the 12at7 PI? I’ve been tempted to try one in my recto but I never got around to buying one. Not sure what to expect, I think I saw online a couple people saying they liked it in the Recto, but that’s it.

Not that I remember... and it shouldn't be, because the power stage does 98% of the amplification in modern channel switching amps. But I did feel the amp needed a little bit more volume to push the speakers the way I wanted, because it was a more open and less compressed tone (much like a Marshall head and 412 if that makes sense?). But it was much more touch sensitive. Usually on these types of amps picking hard/light doesn't change much, but this "mod" made it much more noticeable, almost to the point where you might use a light compression in front if you wanted the levels more even.

 

[KailM]

it was a more open and less compressed tone (much like a Marshall head and 412 if that makes sense?). But it was much more touch sensitive. Usually on these types of amps picking hard/light doesn't change much, but this "mod" made it much more noticeable, almost to the point where you might use a light compression in front if you wanted the levels more even.

That's what I noticed as well. More dynamics than before, and a little looser response, but the low-end "blooms" a little harder (it sounds absolutely massive, in fact). I had a 5751 there before, which was already headed in that direction, and certainly sounded and "felt" better than a 12ax7. In my 6505 at least, it became a little more "Recto" like, but still has midrange grind for days, and it gets more intense the harder you pick. I'm loving it!

 

[KailM]

Was there any volume loss with the 12at7 PI? I’ve been tempted to try one in my recto but I never got around to buying one. Not sure what to expect, I think I saw online a couple people saying they liked it in the Recto, but that’s it.

It's worth a try. FWIW, the JJ 12AT7s are cheap, and sound great. And at least a few years ago when I bought my JAN Philips 12AT7, it wasn't nearly as expensive as the NOS 5751s and 12AX7s. I wanna say I paid no more than about $25 shipped. Compared to the JJ I have, the Philips is just a smidge brighter and clearer. Not a big difference though.

 

[USMarine75]

Not cutting enough, turn it up until it does! lol

You mean because the goalposts are increasingly submerged in tidal waters?

That's what I noticed as well. More dynamics than before, and a little looser response, but the low-end "blooms" a little harder (it sounds absolutely massive, in fact). I had a 5751 there before, which was already headed in that direction, and certainly sounded and "felt" better than a 12ax7. In my 6505 at least, it became a little more "Recto" like, but still has midrange grind for days, and it gets more intense the harder you pick. I'm loving it!

It's worth a try. FWIW, the JJ 12AT7s are cheap, and sound great. And at least a few years ago when I bought my JAN Philips 12AT7, it wasn't nearly as expensive as the NOS 5751s and 12AX7s. I wanna say I paid no more than about $25 shipped. Compared to the JJ I have, the Philips is just a smidge brighter and clearer. Not a big difference though.

Yeah the 12AT7 will be much more noticeable in the PI slot too. Like I said gain factor is close between 5751 and 12AX7, as they are really similar in most metrics. The 12AT7 is more different (lower in all metrics). So with variable gain factors between different brands and types of 12AX7 (JJ 12AX7 have like 90+ vs the Sovtek 12AX7W that have like 70 IIRC?) vs the 12AT7 which have 60 gain factor that is where you will really see a difference! And for the price it is definitely worth trying to see if you like better than the 5751 or 12AX7 in the PI. I'd be interested in how a Recto or a Framus Cobra would take the 12AT7.

 

[tedtan]

What's in there now?

It's currently a Road King 2 with a stock JJ ECC83S. Where I am really finding it too dynamic is on channel 2 Brit mode, which is a Marshall voicing. Unfortunately, I can't crank it, so the power amp isn't able to contribute much compression.

I'd be interested in how a Recto or a Framus Cobra would take the 12AT7.

If I experiment with the PI in my Road King, I might try this. If so, I'll post the results.

 

[vick1000]

A 12AT7 in the PI can actually push the power section more than a common 12AX7, this is because the PI gain value is not as large a factor in most designs, but the current supplied by the tube is. A 12AT7 produces ten times the current of a common 12AX7, and about 3 times the transductance. Which essentially means you are getting more output from everything before the PI with a 12AT7.

Another tube to try in the PI, is the JJ ECC803.

 

[Mike]

I love and hate tube rolling because I autistically A/B every possible combo of tubes I have available at a given time, but I have found that some slightly unorthodox combinations tend to be my favorite. It's been a while since I did my 6505+, but I'll look later and see what setup I have in there. Not to toot my own horn, but everyone should try it, it's that good.

 

[JesperX]

I love and hate tube rolling because I autistically A/B every possible combo of tubes I have available at a given time, but I have found that some slightly unorthodox combinations tend to be my favorite. It's been a while since I did my 6505+, but I'll look later and see what setup I have in there. Not to toot my own horn, but everyone should try it, it's that good.

You're not alone. I do the same thing to the point where I'm sick of it, but I can't not try every combination.

Strangely I really liked a bunch of Mesa branded electro-harmonix 12AX7s that I've been holding on to for 16 years. Pissed me off because I bought 4 JJ 5751s and only ended up using one of them to tame the gain a bit.

 

[Mike]

Okay so here's my 6505+ tubes of choice

V1 - Ruby 12AX7AC5 HG+ lots of mids, clarity and attack. Full, but even body, tight and super low noise. Great for arguably the most important tube spot that affects tone, feel, input gain, etc.
V2 - Ruby 12AX7AC5 HG+. Because it just sounded good stacking with another on the lead channel. Just chunky grindy balls.
V3 - Ruby 12AX7AC7 HG+. Because it just sounds good. Not really an effect on the tone stack, but it doesn't add or take away anything from the sound or loop engageing/disengaging and it's super quiet, so I put it there
V4 - The infamous phase inverter, now one might ask, but Mike, everyone knows this is supposed to be the Sovtek 12AX7LPS. It's balanced and just tried and true for that slot in all high gain amps. NO! Fuck that tube. If your 6505 sounds like ass it's that tubes fault. Biggest lie sold to people. Get it out of your 6505 and put a JJ ECC83S HG+ (Ruby) in there. Not shilling but I'm pretty sure Valvequeen is the only one who carries these magical tubes. Once I took the LPS out and put the JJ in the whole amp just came to life. Everything sounded more full, upfront, and just cohesive. Do it.
V5 - Ruby 7025 SS "Silver Special". It's the icing on top of the red channel cake. Adds a touch more brightness and cut without adding a ton more gain.
V6 - JJ ECC83S HG+ (Ruby). I just like the way it paired best with V1 to make my Rhythm channel have plenty of gain and act as primarily another strictly high gain channel to give me a second tone set to compliment the lead channel. Also if you're a bedroom player, it'll give you amazing high gain tones at low volumes out of the green channel. The downside is when you play on clean, you'll have to roll back the gain somewhere in your setup to clean things up.