PRRI Tubes

**blille** · 06-01-2018, 02:01 PM

I have a PRRI with a 1x12 (CRex) incoming.

Since I also have a 5e3 I plan to use the PRRI mostly for the classic cleans. I will use it for Jazz and P&W. I plan to get a couple of tubes and wanted to get your feedback.

V1 Preamp: likely a NOS RCA 12AY7 - loved it on my 5e3 and I would like to tame the amp a bit since like I said I plan to use it mostly for cleans up to breakup. Also read great things about 5751 in this position but I have no experience.

V2 Reverb Driver: 12AU7 - I just need a bit of reverb. Any recommendations? Is NOS worth it for this position?

Would love to get your thoughts for jazz in particular. Like I said before I also have a 5e3, that should cover Blue Note repertoire.

**ThatRhythmMan** · 06-01-2018, 02:05 PM

My favorite in the V1 position is a 5751, pretty much across the board in 12ax7 amps. I still play around with the other positions and go with what the amp tells me as I swap them out.

**blille** · 06-01-2018, 02:17 PM

Originally Posted by ThatRhythmMan

My favorite in the V1 position is a 5751, pretty much across the board in 12ax7 amps. I still play around with the other positions and go with what the amp tells me as I swap them out.

Thanks! Any 5751 in particular?

**marcwhy** · 06-01-2018, 03:05 PM

I have this 7025 in my amps.

**D.G.** · 06-01-2018, 03:27 PM

Blackface amps are not nearly as tube sensitive as tweeds. I wouldn't bother with any tube changes unless you're having a problem. The stock tubes are just fine for cleans.

Here's a tip:
If using humbuckers or p90's try pluggin into input 2. It reduces the amount of gain hitting the preamp section and can warm the tone as well.

**ThatRhythmMan** · 06-01-2018, 04:39 PM

I’ve been using JAN Sylvania 5751s and I’ve been really happy with them.

While I play tweed amps, I still much prefer a 5751 in the V1 of a blackface amp. To my ear the difference is quite significant.

**Longways to Go** · 06-01-2018, 05:32 PM

+1 on the 5751. Jan Phillips is my favorite.

I'd skip the 12AU7.

**blille** · 06-01-2018, 06:36 PM

Thank you all!

From what I’m hearing I should not expect a massive change after the tube swap and if I do go for it to go for a JAN 5751 rather than 12AY7 for v1.

And from what I see there is not much feedback about v2.

**D.G.** · 06-01-2018, 08:45 PM

If you wanna tame the reverb a bit, and get more "range" on the knob, try a 12AU7 in the reverb slot.

**vinlander** · 06-01-2018, 08:53 PM

I had bought 2 GE JAN 5751 with matched triods for using as a PI tube in my former Peavey 6505+ amp (my metal years), but they were never used. The amp got sold years ago and they were still in my drawer.
Now one of them is in V1 of my PRRI and the other is waiting for a future retube

**Alder Statesman** · 06-01-2018, 11:11 PM

Originally Posted by ThatRhythmMan

I’ve been using JAN Sylvania 5751s and I’ve been really happy with them.

While I play tweed amps, I still much prefer a 5751 in the V1 of a blackface amp. To my ear the difference is quite significant.

I use a GE JAN 5751 and I really like how it smoothed out my amp. I got it from the www.TheTubeStore.com. It was made in GE's Kentucky factory in 1986.

**neatomic** · 06-01-2018, 11:23 PM

classic nos ge 5751 would be nice...

if you want to save some $$$$..with a new tube...try the jj-5751....

it'll get you close tonally, tho it'll not last near as long..a good ge could last decades!!!...(tho try to find a well spec'ed "NOS"one!!)

12ay7 works for 50's vintage tweed, but doesnt always translate to modern repro amps

cheers

**blille** · 06-02-2018, 01:38 AM

Thanks again!

I’m going to go with a GE JAN 5751 for v1 and and an RCA 12AU7 for v2 (it was quite cheap so I decided to give it a try).

I’ll report back when I get them and use them for a while.

**blille** · 06-02-2018, 03:10 PM

Originally Posted by vinlander

I had bought 2 GE JAN 5751 with matched triods for using as a PI tube in my former Peavey 6505+ amp (my metal years), but they were never used. The amp got sold years ago and they were still in my drawer.
Now one of them is in V1 of my PRRI and the other is waiting for a future retube

Is there a benefit to balanced triodes outside of PI positions?

**stevo58** · 06-03-2018, 03:16 PM

Hi. I'm new here, but have been lurking for years, whatever that is worth. I hope I don't step on any toes.

Originally Posted by blille

Is there a benefit to balanced triodes outside of PI positions?

No.

Now, the more important question is:

Originally Posted by blille

Is there a benefit to balanced triodes in PI positions?

I'll divide this into two sections, fact, and opinion based on fifteen years of amp building.

FACT:

Not in a Princeton Reverb or any other amp which uses a "cathodyne" phase inverter. This sort of phase inverter only uses one of the two triodes in the tube, so balancing them is pointless.

Other amps using a cathodyne phase inverter: all Fender tweeds EXCEPT last-generation Bassman (5F6) and Twin (5F8). These two amps use the "long-tailed pair" phase inverter, which DOES use both triodes in the tubes. Other amps using a long-tailed pair: any black or silverface Fender (Deluxe Reverb and larger); Marshall, Mesa, most other modern push-pull amps.

Does a balanced tube make a difference in an amp with a long-tailed pair phase inverter?

The tube is only one component in the phase inverter circuit which appears as a symmetrical pair. There is also a pair of 1 mOhm resistors in the tail; output coupling capacitors on the anodes, and load resistors on the anodes. For a truly balanced phase inverter, ALL of these components would have to be exactly matched, and, since component values drift with age, each component in the various pairs would have to drift exactly as much as the other component in the pair. Tolerances for these components is at best 10%; and it is unlikely that a large manufacture would go to the considerable trouble and expense of testing and matching (and rejecting) large number of components for mass-produced, machine-loaded, wave-soldered PCBs. You might get that from a boutique builder if you ask nicely and pay him for it.

But, by design, the anode resistors in the Fender variation of the long-tailed pair are mismatched - one is 82K, the other is 100K. There are specific reasons for this, but practically, many manufacturers, even large famous ones, propagate Leo's design without considering why he did it. It's a good design, after all.

So it is impossible to try to get a fully symmetrical, balanced phase inverter just by putting a balanced tube in the position (and the two triodes will also drift with age, and not be balanced anymore anyway).

Balanced triodes make sense in a stereo hif-fi amp, where both channels have to be identical as possible. These amps will typically also use components with far tighter tolerances (and far higher cost, too). In guitar amps, balanced PI triodes is a way for the tube reseller to make more money (ok, that last bit belongs in the next section).

OPINION

Very likely, if you had a truly balanced phase inverter circuit, you wouldn't like the way it sounds. A tube amp - even one played very clean, like a Fender Twin - lives from non-linearity and subtle distortion. The distortion added in the phase inverter is very important in producing the "warm" sound many love in tube amps. A perfectly balanced phase inverter would push the amp towards sterility and hi-fi reproduction. If this is what you are after, you are better off using a good solid-state power amp rather than trying to get it out of a tube amp.

In my opinion, you will get far more for your money by investing in a high-quality tube for the first position - this has far more influence over the tone than any other tube in the preamp. Like many others above, I find a good NOS 5751 (GE, Sylvania, RCA, whatever) is perfect in the first position of a blackface or silverface Fender. In tweeds, I prefer a good NOS 12AY7.

Thank you for your patience, and I hope I haven't offended anyone.

Steven

Edit: by the way, the reverb driver (12at7 in a PR) is driven VERY hard. It is worth it to buy a good NOS tube here not because of tone, but because of durability.

**blille** · 06-03-2018, 04:26 PM

Originally Posted by stevo58

Hi. I'm new here, but have been lurking for years, whatever that is worth. I hope I don't step on any toes.

No.

Now, the more important question is:

I'll divide this into two sections, fact, and opinion based on fifteen years of amp building.

FACT:

Not in a Princeton Reverb or any other amp which uses a "cathodyne" phase inverter. This sort of phase inverter only uses one of the two triodes in the tube, so balancing them is pointless.

Other amps using a cathodyne phase inverter: all Fender tweeds EXCEPT last-generation Bassman (5F6) and Twin (5F8). These two amps use the "long-tailed pair" phase inverter, which DOES use both triodes in the tubes. Other amps using a long-tailed pair: any black or silverface Fender (Deluxe Reverb and larger); Marshall, Mesa, most other modern push-pull amps.

Does a balanced tube make a difference in an amp with a long-tailed pair phase inverter?

The tube is only one component in the phase inverter circuit which appears as a symmetrical pair. There is also a pair of 1 mOhm resistors in the tail; output coupling capacitors on the anodes, and load resistors on the anodes. For a truly balanced phase inverter, ALL of these components would have to be exactly matched, and, since component values drift with age, each component in the various pairs would have to drift exactly as much as the other component in the pair. Tolerances for these components is at best 10%; and it is unlikely that a large manufacture would go to the considerable trouble and expense of testing and matching (and rejecting) large number of components for mass-produced, machine-loaded, wave-soldered PCBs. You might get that from a boutique builder if you ask nicely and pay him for it.

But, by design, the anode resistors in the Fender variation of the long-tailed pair are mismatched - one is 82K, the other is 100K. There are specific reasons for this, but practically, many manufacturers, even large famous ones, propagate Leo's design without considering why he did it. It's a good design, after all.

So it is impossible to try to get a fully symmetrical, balanced phase inverter just by putting a balanced tube in the position (and the two triodes will also drift with age, and not be balanced anymore anyway).

Balanced triodes make sense in a stereo hif-fi amp, where both channels have to be identical as possible. These amps will typically also use components with far tighter tolerances (and far higher cost, too). In guitar amps, balanced PI triodes is a way for the tube reseller to make more money (ok, that last bit belongs in the next section).

OPINION

Very likely, if you had a truly balanced phase inverter circuit, you wouldn't like the way it sounds. A tube amp - even one played very clean, like a Fender Twin - lives from non-linearity and subtle distortion. The distortion added in the phase inverter is very important in producing the "warm" sound many love in tube amps. A perfectly balanced phase inverter would push the amp towards sterility and hi-fi reproduction. If this is what you are after, you are better off using a good solid-state power amp rather than trying to get it out of a tube amp.

In my opinion, you will get far more for your money by investing in a high-quality tube for the first position - this has far more influence over the tone than any other tube in the preamp. Like many others above, I find a good NOS 5751 (GE, Sylvania, RCA, whatever) is perfect in the first position of a blackface or silverface Fender. In tweeds, I prefer a good NOS 12AY7.

Thank you for your patience, and I hope I haven't offended anyone.

Steven

This was very helpful, thanks!

**Wildcat** · 06-05-2018, 04:21 PM

Is this Limited Edition model from Sweetwater?
I just bought one if so.

Originally Posted by blille

I have a PRRI with a 1x12 (CRex) incoming.

Since I also have a 5e3 I plan to use the PRRI mostly for the classic cleans. I will use it for Jazz and P&W. I plan to get a couple of tubes and wanted to get your feedback.

V1 Preamp: likely a NOS RCA 12AY7 - loved it on my 5e3 and I would like to tame the amp a bit since like I said I plan to use it mostly for cleans up to breakup. Also read great things about 5751 in this position but I have no experience.

V2 Reverb Driver: 12AU7 - I just need a bit of reverb. Any recommendations? Is NOS worth it for this position?

Would love to get your thoughts for jazz in particular. Like I said before I also have a 5e3, that should cover Blue Note repertoire.

**blille** · 06-05-2018, 04:36 PM

Originally Posted by Wildcat

Is this Limited Edition model from Sweetwater?
I just bought one if so.

Yes it is! Congrats. Now we're amp brothers.

Hope you like it too!

**Wildcat** · 06-06-2018, 07:23 AM

Yes I do like it. The 12" speaker in the PRRI was the selling point. Plus the lacquer tweed covering.

Like you I was thinking about "stepping up" the amp. I am serious considering to send it to George Alessandro to remove the circuit board and rewire it to BF standards. Also, he offers NOS Tubes. So your thread was spot on for me. I will be using your thread as a reference point on the tubes.
Alessandro Products | Rewiring Services

Question; How do you like the Eminence CR? I am a Weber speaker guy. The CR sounds a bit "off" to me. Maybe a bit muffled? I have about 10 hours so far on it at normal playing levels. I am going to give it a chance to "break in" then decide.

Originally Posted by blille

Yes it is! Congrats. Now we're amp brothers.

Hope you like it too!

**blille** · 06-06-2018, 10:18 AM

Originally Posted by Wildcat

Yes I do like it. The 12" speaker in the PRRI was the selling point. Plus the lacquer tweed covering.

Like you I was thinking about "stepping up" the amp. I am serious considering to send it to George Alessandro to remove the circuit board and rewire it to BF standards. Also, he offers NOS Tubes. So your thread was spot on for me. I will be using your thread as a reference point on the tubes.
Alessandro Products | Rewiring Services

Question; How do you like the Eminence CR? I am a Weber speaker guy. The CR sounds a bit "off" to me. Maybe a bit muffled? I have about 10 hours so far on it at normal playing levels. I am going to give it a chance to "break in" then decide.

That's great! Having GA rewire it would obviously great. But that would be a bit too much ($$$) for me.

On the speaker I'm biased. I actually really like the CRex and Eminence. I used to have it on my 5e3 (swapped it for a Maverick to attenuate) and I know really like it. What it does to the top frequencies like you say is a bit polarizing, not for everyone.

What I might actually do is swap the transformer to an Allen T020 to tighten up the bass and increase headroom furtherike I was recommended here

Tubes for PRRI
Tubes for PRRI | Telecaster Guitar Forum

Here is an article on the transformer Billm Audio >> Upgrade Output Transformer for Blues Junior

It is supposed to be a direct swap and work well with 12" Allen Amplification - Parts Order Page

I'm waiting for the reverb tube and to play with it in a mix to see how the reverb works before considering swapping the tank for a medium decay Mod.

**stevo58** · 06-06-2018, 12:07 PM

Hi guys. If I may butt in here again.

The CR is a fine speaker, but is well-known to be ‘dark.’ That can work but depends on your guitar, amp, and expectations.

I suggest you not change everything at once.

The speaker will affect your sound more than anything else. Although Celestion, Eminence, and Weber all make fine speakers, don’t rule out others. My personal favorite current production speakers for Fender amps are Jupiter ceramics. These are made by WGS to Jupiter’s specs and they got it just right, in my opinion. The Jensen Jet Blackbird is also excellent in Fender amps, but is a bit pricey. And if you can find a D120F in good condition, perfect.

Testing speakers is expensive, so decide what sound you want and do your research.

There’s really nothing wrong with PCB construction. It’s biggest disadvantage is difficulty of repair. There is nothing per se wrong with a PCB. Like everything, there are good and not so good implementations. Fenders are ‘ok.’ Rebuilding is going to cost you an arm and a leg, and I am skeptical of the cost/benefit. Alessandro will obviously do good work.
I would settle the speaker first before rebuilding.

Steven

**Longways to Go** · 06-06-2018, 01:41 PM

I don't quite get why you would want to gut a PRRI when there are so many handwired clones out there to choose from.
Me, I'd just slow down a bit, enjoy the PRRI, and try out little changes (like tube swaps) one at a time.

**blille** · 06-08-2018, 11:52 PM

So I got my GE JAN 5751 for v1 and RCA 12AU7 for v2.

I’ve just played a bit with them and my first impressions are that v2 is a winner. Not only the amount of reverb is more manageable, it also sounds “better” I can’t point my finger at why. Maybe some more mids? Or just less treble?

The jury is still out on v1. The best way I can put it is that it sounds more “fendery” lol chimey? I do like it but I’m going to try others and see where I end up!

Thanks again.

**stevo58** · 06-09-2018, 05:44 PM

That makes sense. I can’t speak for new 5751s (I have a healthy stash of NOS I use) but there are two features of a real one which would produce that. First, it has roughly only 70% of the gain of a 12ax7. In the real world, you will see a gain of about 50 from a 12ax7, a 5751 would be correspondingly less.

Second, it is difficult to overdrive the grid of the 5751. This results in less distortion. Stevie Ray Vaughan for example loaded the preamps of his amps with 5751s to reduce preamp distortion as he wanted only power amp distortion.

steven

**neatomic** · 06-09-2018, 08:32 PM

^ exactly...as per srv/s58...a nice warm jazz tone from a loud power amplification of a clean pre amp tone...the clean pre amp tones usually take od/distortion/gain-Y pedals better as well!!

and of course work with the volume and tone controls on your guitar as well..they are there for a reason!..nuance & finesse!!!

cheers

ps- stevo58...i like how you roll...hope you stick around and contribute to more threads...it's a great forum (when its behaving nicely nicely...& that's most of the time! hah)...welcome aboard