best for cleans? blk or silverface

[Toxophilite]

I'm still enjoying the two Ab763 deluxes I built to use in stereo
They aren't quite loud enough for my loud rock band but for my jazz/latin caberet act they're about right
However I like to tinker
So I have a couple questions
I like to have a clean platform and use pedal in front of it, particularly for the jazzy band I like clean clean clean
I use an old rolan space echo and old gretsch's so I have plenty of character in my sound already


I've read that the silverfaced deluxes (A1172?or AB868?)with their slightly different circuits (PI)and 5U4GB have more clean volume before they begin to break up
Is this true?
Does anyone have actual experience comparing these amps?


Also is it true that the non reverb deluxes have more clean volume before starting to breakup??


Just curious and it would be an easy thing to 'Silverface' my blackfaces..likely to the horror of many!! hahaha

[P Batty]

The black and the pre-1976 non-master volume silver faced Deluxe Reverbs are pretty close, if not identical except for the rectifier tube and the PI.  It would easy enough to replace the 1MΩ resistors in the PI with 330kΩ, its worth a try. Do you have  hi-efficiency speakers in your DRs? They will make a noticeable difference in headroom at any given volume. A little more negative feedback (i.e., use 560Ω instead of the 820Ω) might help clean it up a little as well. A plug-in SS rectifier might help too. Taking the Reverb circuit out would definitely affect the headroom. You could also bias the amp a little cooler.

I've blackfaced a master volume silverface DR and ended up using a 5AR4 instead of the 5U4GB. The voltages were a little higher, but it worked good, but I wasn't going for a real clean sound. I suspect that the actual power transformer and output transformer you used would make a difference too, but I don't know all the varieties of them.

[thermion]

FWIW, one of the cleanest fenders I've played was a late 1970s pro reverb. It was ultralinear output, solid state recto, and really would not distort at all until it was painfully loud. Blackfacing this beast was a total overhaul, replaced both pt (since I wanted a tube recto) and ot (did not care for the ultralinear config) plus all the "usual" mods. It also needed chassis work and a total rewire to fix the layout.
Perhaps the only cleaner fenders would be the twin reverb/super 6 of the same era or those insane PS-series amps.
Hope this helps!

[Toxophilite]

My deluxes both have JBLs K120 in one D123 in the other, so pretty high efficiency
I need the reverb circuit ( i added it after the fact as a tag on bit of chassis) but was thinking about altering it like the silverface reverb circuit


I have an ultralinear super that I really like, but 85 lbs , whew! I use it with another little amp for stereo. These little guys were intended to replace it at small venues.


Does the different PI make a big difference ? with the 330k resistors and the .01 cap instead of .001 I guess some more bottom gets through...I like that about the super the big warm bottom end.

[Backwoods Joe]

Toxophilite, I just saw a very clean space echo in a local shop for $1500!!

[Toxophilite]

HIlarious!
It was probably the RE-201 which everyone seems to want..a couple more echo options and okay reverb
I like the RE-150 because you can run the wet and dry signals out separately into different amps...giving you a stereo reverb type effect, lovely
My original one was purchased on tour for $40 from a rockabilly guy in Sand Diego in the early 90s. he was a echoplex guy and thought the space echo was modern junk. A year or so ago i purchased one in need of basic servicing for $400 (it was missing EVERY bolt to mount the chassis in it's cabinet as well as the screws to hold down the tape cover. New tape, cleaning etc worked perfectly and I sold my old one for $550. So now I just have one again. I feed it with 8-track tape which is the proper back lubricated tape it needs.
Great machines and given a small amount of maintenance a couple times a year they are extremely reliable. Any reports to the contrary are the result of neglect/ignorance or past abuse IMHO.
$1500 is way too much though. That's like $10,000 Canadian!! That sounds like a unit waiting for sucker!!


Any ideas on how the the PI influences the amps performance?...maybe I'll just give it a shot and see if i notice anything

[HotBluePlates]

I'm still enjoying the two Ab763 deluxes I built ...
They aren't quite loud enough for my loud rock band but for my jazz/latin caberet act they're about right


...


I've read that the silverfaced deluxes... have more clean volume before they begin to break up ...

How much LOUDer do you need? Cause at the end of the day, silverface Deluxes are just another 2x 6V6 amp, just like the blackface ones. That means at the end of the day, the 6V6 output section will have the same amount of clean output power to give.


If the supply voltage is higher in the silverface Deluxe, then all other things equal, it might get a touch more output power. But you're probably talking fractions of a watt, not a serious output power difference.

... Also is it true that the non reverb deluxes have more clean volume before starting to breakup??

I added the emphasis to "volume" in the quote.


Non-Reverb Deluxes don't have as much preamp drive because they lack the reverb circuit and its make-up gain triode. So they will stay cleaner, higher on the volume pot. In other words, a non-'verb Deluxe might start distorting around 7 or 8, where a Deluxe Reverb might have audible distortion starting around 4 or 5.


But I would bet hard currency that if you use an SPL meter to measure the actual volume out of the (same) speaker, each distorts at about the same volume.


If you really need more volume into the room, you're best off moving up to a 2x 6L6 amp. If you then have a speaker that can take 40-60w, you can use a single speaker and keep the size & weight down. Bigger cab for multiple speakers is most of what will add weight for these bigger amps.


So my opinion is if you need a volume increase more than "I think that's a little louder (and still clean) than the other amp," you'll need to move up to a noticeably higher-wattage output stage.

Does the different PI make a big difference ? with the 330k resistors and the .01 cap instead of .001 I guess some more bottom gets through...

The increased coupling cap (0.001uF to 0.01uF) has some effect, because it's 10 times bigger. But the decreased grid reference resistor (1MΩ to 330kΩ) offsets the effect somewhat because it's 0.33 times the original value. All of this is probably moot, because the input impedance is on the order of 2-5 times the value of the actual grid reference resistor, due to bootstrapping. So even the 0.001uF lets plenty of bass through, because it's the effect of both the cap and the grid reference resistor (as well as other resistance in the circuit) which sets the low-frequency roll-off.


The apparent input impedance due to bootstrapping is probably best measured rather than calculated, because there is also feedback underneath the tail resistor, which will affect the result.


Personally, I think Fender made the change because they didn't have much call for 0.001uF caps, whereas they use 0.01uF caps in every amp with tremolo, and several others besides... I don't think you'll hear much difference in the low end, but you might hear a slight alteration you like/don't like. Try it & see.

[Toxophilite]

And thank you for this as well
Very thorough and informative
i was wondering how an amp without the reverb would be actually cleaner with the same power amp.I thought it might be a function of more preamp gain overdriving the power amp earlier. But that's guessing. The amp did get noticeably louder (at the same point on the volume knob) when I added the reverb circuit, but it seems to start to distort a little earlier so it's probably all relative as you say.


I'm mostly curious at this point. I think these amps will be fine with the jazz act. I rarely get my super past 3 with that band and then it's pretty &*^*&^ loud (That's usually at the end of the eve when the drummer is getting all Gene Krupa on me (I like it though))If at that point I'm pushing the deluxes' a little it'll be approriate


I will leave them as they are and try them at this outdoor beer on the pier caberet we're playing this upcoming weekend and see how they do.

[sluckey]

I don't usually think of 6V6 amps when thinking about outdoor venues.

I know you like clean sounding Fender amps, but have you considered one of the old Sunn amps? If loud and clean is the goal, you won't be disappointed. And they are really a simple design/easy build if you forgo reverb and tremolo.

[Toxophilite]

Well I just found out this morning that they're only having a vocal PA so I may be lugging my super up there anyway


I'll look into the Sunn builds and I appreciate the idea though I do use tremelo and reverb in a couple songs
THanks

[jojokeo]

i was wondering how an amp without the reverb would be actually cleaner with the same power amp.I thought it might be a function of more preamp gain overdriving the power amp earlier. But that's guessing. The amp did get noticeably louder (at the same point on the volume knob) when I added the reverb circuit, but it seems to start to distort a little earlier so it's probably all relative as you say.

As HBP explained, the "reverb" amps have an extra gain stage. It makes the signal louder/stronger at that point in the circuit compared to the non-reverb circuit and has a lower threshold for clean therefore breaks up earlier as a result. This is evident if you modify or work on the non-trem side of the deluxe reverb.
 
I haven't seen this mentioned but you could put 12AY7/5751 in your amps for cleaner action on one venue and put the 12AX's back in for the rock stuff. Maybe best of both worlds for you and the easiest too.

[Toxophilite]

Oh
I was pretty sure hot blue plates was saying that the though the amp likely would start to distort sooner on the on the volume pot, it was also louder at that point than the same position as non reverb amp, making it relative

[HotBluePlates]

Oh
I was pretty sure hot blue plates was saying that the though the amp likely would start to distort sooner on the on the volume pot, it was also louder at that point than the same position as non reverb amp ...

Almost.


Let's say you have 2 identical cars. One jumps from idle to 6500 rpm when you mash the gas pedal all the way for the floor, while the other hits 6500 rpm with the gas pedal 2/3 of the way to the floor. One "gets there faster" but both have the same engine and gearing, and resulting top speed.


So the one which hits 6500 at 2/3 pedal-mash won't go to a higher top speed than the other car. I see it as the same situation with silverface/blackface, reverb/non-reverb... If you had one of each side-by-side, the blackface or reverb model might distort at a lower volume knob setting. But if you set both amps for the same onset of distortion, they will be essentially the same volume out of the speaker, because the identical output sections mean they output identical amounts of power.


There are all sorts of games you could play to fool yourself into thinking your amp was "cleaner, louder" or "has higher headroom".

• Set the bias much cooler; now the phase inverter has to output a larger signal to drive the output tubes to clipping. Depending on other factors (power supply and OT), the amp might not output any more power.
• Add a resistor between the top of a volume pot and the coupling cap feeding the volume pot. Now you can't "turn the amp all the way up"... there's always some voltage-division at the volume pot, and the amp seems like it stays cleaner to a higher volume pot number. Really, you're just reducing signal level in the preamp.
• Go the opposite way: Don't use a 10% audio taper pot, find a 30% taper audio pot or use a linear pot. Now the amp seems to get really loud, really fast and distort on a much lower volume knob setting. Nothing about the amp's power or preamp architecture changed, but the different rate of voltage division with volume knob turn makes the amp seem "very loud and 'gainy' ".
• Tinker preamp or phase inverter loads and operating points; you might eliminate small %'s of distortion in the late-preamp stages so they stay dead-clean and the output tube's onset of distortion is the limiting factor. Overall amp output power didn't grow, but again distortion may ocur "later on the volume pot" giving you the impression your amp gained a lot of headroom (assumes nothing in the preamp is being driven to gross distortion, like feeding volts of signal into your input jack or using a master volume control).
• Use lower-gain preamp tubes; again, the output stage makes no more power than it did before, but the signal driving the phase inverter and output tubes is weaker, giving the impression of more headroom as you have to turn the volume control higher to cause the output stage to distort.

The common theme throughout is the output stage is the limiting factor on power output, volume, and "how loud at the onset of distortion." Classic non-master volume amps are designed this way (including almost all old Fender amps) so they really never give any more volume/power unless you move to a bigger output stage.


It's easy to fool yourself if your amp's performance-before-modification is your reference point. The problem is easier to see after you, say swap all tubes for lower-gain types, and then play with your drummer again. The amp distorts higher on the volume knob, but you haven't gained any additional clean volume above your drummer's playing.