Converting PCB to HW Point to Point Boards

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Re: Converting PCB to HW Point to Point Boards

Post by Larsongs » Thu Sep 22, 2022 9:39 pm

I agree.. I can play a good Show with my 65 DRRI.. But, I feel like I play a better Show with my 65 PRRI, Twin or my Vox AC15 with Alnico Blue…. I’m investigating how to bring my DRRI up to their equivalent level.

I’ll start with Speaker & Tubes as suggested.. I’ll try to get a Speaker & Tubes that sound as close as possible to what we’re used in the best sounding BF or SF Amps.. Like those in my friends who have the original spec vintage (not modded) SF & BF Deluxe Reverbs mid 60’s & Early 70’s….

As for P2P HW Board…. I can’t fault the PCB’s. But, If the PCB in my 65 DRRI should ever fail I’ll check the cost of both…

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Re: Converting PCB to HW Point to Point Boards

Post by øøøøøøø » Fri Sep 23, 2022 6:14 am

Sometimes the thing that sounds better to us is the thing we believe to sound better.

That being the case, if a turret or eyelet board makes someone feel better about their amp, by all means they should do it.

The player is part of the “loop,” so anything that impacts the player’s state of mind can also impact the sound.

If they believe it will sound better, it may well make them sound better, which will improve the overall result.

But it’s a lot more affordable for the player to simply gain confidence in their own ability to get good sound regardless of tiny details about the gear

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Re: Converting PCB to HW Point to Point Boards

Post by Larry Mal » Fri Sep 23, 2022 6:36 am

So, what do we make of these claims?

Here is the first one:

One of Fender's most classic amplifiers remains a favorite to this day and the Princeton Reverb Reissue is perhaps the most successful of the reissue series. Our mods take the PRRI back to the glory days of the blackface era and adds a couple of the most famous mods done to this amp over time. There is an unused power node in the Princeton that many think Fender did on purpose so it would not compete directly with its big brother Deluxe Reverb. The phase inverter in your Princeton Reverb Reissue shares it's power supply with the preamp tubes. This dulls the sound fed into the power tubes and doesn't fully allow the amp to shine it's perfect tonal light to the world. The good news is Fender left the appropriate power rail for that phase inverter in the design even though it goes unused!

And if you prefer to see what is being discussed you can do that here.
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Re: Converting PCB to HW Point to Point Boards

Post by øøøøøøø » Fri Sep 23, 2022 7:40 am

Meh.

More on this later, but the short version:

Regardless of what Fender did (and what an internet person speculates about their motives), a lot of players (self included) don’t feel there’s anything wrong with the sound of the Princeton Reverb.

We’re not designing control room monitoring systems here--these are guitar amps. "Better” isn’t always better

In any case, the “FeNDer iNtENTioNalLy SaBOtAgeD the PrINceTon” conspiracy theory doesn’t seem especially likely to me.

More likely that a prototype did give the PI its own power supply node, but on test they decided it sounded (or measured!) better being fed by a lower voltage potential.

OR they already had that particular multi section cap can in use in other products, so might as well get some more hum reduction (in the form of an extra filter pole) “for free” (or for the cost of one resistor, if being pedantic) instead of leaving the extra section unused (or inventorying a similar, but slightly different part at lower quantity)

Both of my suggested explanations could be true at the same time, incidentally

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Re: Converting PCB to HW Point to Point Boards

Post by Larsongs » Fri Sep 23, 2022 7:52 am

I suppose the argument will always be, Sound is Subjective… I don’t know if I agree with that… I’m sure many will disagree.. I suppose we can agree to disagree on that..

I do lots of Recording & Control Room Sound is extremely important to me.. Actually it’s everything…

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Re: Converting PCB to HW Point to Point Boards

Post by øøøøøøø » Fri Sep 23, 2022 9:02 am

Larry Mal wrote:
Fri Sep 23, 2022 6:36 am
So, what do we make of these claims?

...This dulls the sound fed into the power tubes and doesn't fully allow the amp to shine it's perfect tonal light to the world...
Killing time in an airport, so to go through this in greater detail, here's an AA1164 Princeton Reverb schematic:

Image

This isn't the cleanest copy (more-legible version here), but what the YouTuber is referring to is the "triangle" section of the multi-cap can at the junction between two 18k, 1W resistors (drawn directly below the lower 6V6 on the schematic)

The way a guitar amp power supply works is this: alternating current is stepped up by a transformer, then "rectified" into pulsing DC. What the rectifier does is to take the mathematical absolute value of the (nominal) sine wave input power, which creates a series of positive voltage pulses happening 100 or 120 times per second (depending on your power grid).

Since all of the pulses are positive, this creates a heavy positive DC bias, but since it's pulsating there's still a serious "alternating current" component with a fundamental frequency of 100/120.

In order to remove this AC component ("buzz") we literally filter it out with something like a gigantic tone control (low-pass filter). Only we set this "tone control" to have a corner frequency way below 20Hz (so as to filter out any 100/120Hz buzz and its harmonics).

Low-pass filters consist of a resistor in series and a capacitor to ground. You can lower the corner frequency of the filter by increasing the resistor (at the expense of voltage) or increasing the capacitor (at the expense of size and... well... expense!)

Each section of resistor-capacitor is called a "pole," and a single-pole filter attenuates at the rate of 6dB/octave. If the -3dB corner frequency were set to 20Hz, the filter would be attenuating only about ~16dB at 100Hz... not nearly good enough.

We can improve this two ways--lowering the corner frequency (each halving of frequency, or octave, gets us another 6dB) or we can add more filter poles.

A two-pole (or "second order") filter attenuates at 12dB/octave, and there things start to get much more advantageous. We can keep adding poles until the slope becomes almost as steep as a brick wall... with each pole we rapidly progress toward a state where the hum becomes so attenuated as to become practically-insignificant, even when amplified many times.

The typical "guitar amp way" is to take the output tube plate supply from the first filter pole. Here, the voltage will be highest (needed for this big 6V6s!), and a little extra hum isn't a big deal for two reasons: Number one, it's at the last stage of amplification, so it won't get re-amplified. Two, the push-pull nature of the class AB output stage will cancel out most of this hum (due to an inherent property of balanced stages called CMRR, or "common-mode rejection ratio"). The particulars of that are beyond our already-bloated scope.

Anyway, each additional filter pole can be called a "node," and these nodes are often (but not always!) used to feed each successive stage with progressively lower voltage (and progressively lower-noise!) until reaching the critical input stage... where low noise is paramount, and extremely-high voltage isn't needed (or helpful).

What the YouTuber observes is that the AA1164 has one "node" that's not being used to supply any tube at all, and concludes (erroneously, in my view) that this represents some kind of missed opportunity. Here's why I think that's wrong:
  • The unused node is specified on the schematic to supply 320VDC, which is far more than is necessary for a cathodyne phase inverter to perform well
  • 320VDC is above the rated maximum on the 12AX7's datasheet, so is technically "disallowed." This doesn't mean a 12AX7 won't survive when given an out-of-bounds voltage (the old ones wouldn't even blink), but Fender were warrantying amps, and might have been cognizant of pushing the reliability envelope too far for no good reason
Could Fender have used a three-section can and a higher series resistance instead? Yes, but as mentioned above--it's likely that Fender used this four-section can cap in several products, and took the opportunity to take the advantage of an additional filter pole (which will give more attenuation at 100/120Hz than an increased series resistance would've).

It's not like adding filter poles that do not serve as supply nodes was exactly rare. A Neumann U67's power supply has a four-pole filter feeding a single supply node; many tube microphones (which need extremely quiet supplies for obvious reasons) are similar.

One thing worth acknowledging: Guitar amps operate almost entirely within the realm of the subjective, so literally any change someone can contrive to make to a successful design will "improve" it in the eyes of someone.

But language like "shine its perfect tonal light into the world" contains nothing objective.

If someone shows scope traces that say "this distorts earlier" or "this distorts later" or "this distorts differently," you can choose whether that attribute seems appealing to you or not--but I'd recommend never taking anyone's word that this-or-that mod is an "improvement" unless you've heard it (and ideally lived with it) yourself.

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Re: Converting PCB to HW Point to Point Boards

Post by Larry Mal » Fri Sep 23, 2022 9:20 am

Thanks, Brad, that's very good information there and I'll take a while to parse it. I don't have the knowledge to evaluate the Youtube person's claims, nor the people selling the upgrade kit. So I appreciate your stepping in.
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Re: Converting PCB to HW Point to Point Boards

Post by Larsongs » Fri Sep 23, 2022 8:43 pm

Larry Mal wrote:
Fri Sep 23, 2022 9:20 am
Thanks, Brad, that's very good information there and I'll take a while to parse it. I don't have the knowledge to evaluate the Youtube person's claims, nor the people selling the upgrade kit. So I appreciate your stepping in.
+1

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Re: Converting PCB to HW Point to Point Boards

Post by fuzzjunkie » Sun Sep 25, 2022 7:35 am

Larsongs wrote:
Mon Sep 19, 2022 9:33 pm
Unicorn Warrior wrote:
Mon Sep 19, 2022 3:43 pm
I would like to do this same thing, but with a Vox AC-10.
I have an AC-10 that I’d like to do too.. I’m curious how much a finished board costs?
Brad talked me OUT of doing this to my Korg AC-30 when I asked about the process 9-10 years ago.

I had a vintage ‘64 at one point in time (which needed almost constant service) and wanted the ‘93 to be easier to fix if it broke down. I also wanted it for aesthetic reasons and a transformer upgrade because the internet convinced me that a Mercury transformer was necessary.

Brad said it was not worth the bother unless I wanted to learn how to build amps.

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Re: Converting PCB to HW Point to Point Boards

Post by øøøøøøø » Sun Sep 25, 2022 7:59 am

...but like most other things on the internet, it's just an opinion.

One that's subject to change as I continue to become better-informed.

When I was 25 I thought it was so very important that an amp use PTP or turret/eyelet board construction. I've obviously swung pretty far the other way, and you never know when I might find some reason to swing back again.

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Re: Converting PCB to HW Point to Point Boards

Post by Mondaysoutar » Tue Oct 11, 2022 10:23 am

Just happened upon this thread happily there, exactly the question I’ve been asking myself, well almost.

I’ve been looking to get a DRRI, found one that’s been converted to handwired for a pretty good price. I’m far far away from an amp expert, but asked an amp tech/builder I know and he’s said for maintaining it’s much better, but resale value might be shite.. I won’t be looking to resell anyway, but generally would yous say I’m better going for this handwired version, or just patch that and go for a PCB/normal one? I’d also emailed Barry from Vyse amps, he’s said he could build me a DR clone, again handwired and that, but just the vibrato channel which is fine by me as I only ever use that channel anyway. The Vyse is slightly cheaper, so unsure what to do. Any thoughts anyone?

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Re: Converting PCB to HW Point to Point Boards

Post by øøøøøøø » Tue Oct 11, 2022 12:22 pm

I think any of those options sound fine, assuming the custom build is good and assuming the conversion has been done well.

Stock DRRI might have the best resale value but otherwise I bet any of the above could perform well

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Re: Converting PCB to HW Point to Point Boards

Post by 46346 » Thu Oct 13, 2022 2:41 am

Larsongs wrote:
Wed Sep 21, 2022 3:10 pm
I have thought about selling my 65 DRRI which has never thrilled me & my 100 Watt Pro Tube Twin which is heavy, really loud & I seldom play anymore.. Although the Twin does sound great when I do play it..

One of my friends has a recent ‘68 Deluxe Reverb which I do like a lot.. Maybe get one of those..
this probably the easiest solution, but i'd go about it like this:

call up some SoCal shops and find who has '68 DR Custom, '65 DRRI, etc. and if your lucky, any vintage DR's.
go give them a spin. if you get the sense that one is better, see if it's returnable over a couple days, buy it bring it home and compare.

same thing with Reverb, Craigslist - if you see a SoCal listing, ask if you can come over for a demo, and bring your amp to compare.
i try to not to waste a seller's time, tho - i can usually tell right away if it's not the right amp.

i'm a real bargain hunter for gear... so i find that if a year passes and i'm not so happy with the gear, i can usually sell it for at least what i paid.

but sometimes i'm just as happy to pay a premium for something that is truly inspiring.

once you're convinced you've landed a happier sound, go ahead and sell your DRRI !
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Re: Converting PCB to HW Point to Point Boards

Post by Larsongs » Fri Oct 14, 2022 2:56 pm

46346,

I have thought & inquired here about doing upgrades to 65 DRRI.. After thinking about it I’m not going to… The only thing I might do is take Tubes, I already have in my collection, & try them out to see if there’s a noticeable improvement..

I’ve played some vintage BF 60’s Deluxe Reverbs that a Collector friend of mine has.. They are like new & sound beautiful.. He has no interest in selling.

I’ve played several in Music stores before Covid that were wrecks.. Prices are crazy right now & finding any in original condition is rare.. Finding one in excellent or mint condition is also rare. If you do the prices are even crazier.. I will keep looking though..

I do want to go play a new 68 Deluxe Reverb.. I like what I’ve read & the YouTubes that I’ve watched.. They have some great features & seem very versatile. They seem to cover traditional & modern Sounds quite well.. It could a solution..

One of the Boutiques that have been mentioned might also be a consideration but so hard to tell without playing.. I certainly won’t commit to buy without trying.. So? I don’t know…

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Re: Converting PCB to HW Point to Point Boards

Post by andy_tchp » Fri Oct 14, 2022 4:27 pm

Larsongs wrote:
Fri Oct 14, 2022 2:56 pm
I do want to go play a new 68 Deluxe Reverb.. I like what I’ve read & the YouTubes that I’ve watched.. They have some great features & seem very versatile. They seem to cover traditional & modern Sounds quite well.. It could a solution..

One of the Boutiques that have been mentioned might also be a consideration but so hard to tell without playing.. I certainly won’t commit to buy without trying.. So? I don’t know…
Definitely try before you buy, and don't put any stock in Youtube demos. I really didn't love the '68 Custom' reissues I tried out for an hour or so when I was looking (ended up with a handmade replica of a Princeton Reverb from Lucas Miles in Melbourne - for around the same price). They didn't sound as good as the '65' types (PRRI/DRRI).

Jack of all trades and master of none IMHO. One of them had major cabinet rattles too. :mellow:
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