|galaxiex||5/11/2018 9:59 PM|
|Output tube snubber kits, any experience?|
Like the title says...
Anyone have experience with these snubber kits?
Any good/worth it?
The write-up "sounds good" or is this voodoo?
|Justin Thomas||5/12/2018 3:15 AM|
|I would look it up in the RDH4. And that is considered a pretty dang reliable source. See what it says there, and see if it would make sense to apply it to a guitar amp.|
Now I'm curious...
|pdf64||5/12/2018 3:49 AM|
Most every sentence seems to have some degree of error / nonsense.
And which SF Fender models had OT protection diodes?
But however flawed the technobabble, you may like the effect of the snubbers.
|J M Fahey||5/12/2018 6:07 AM|
|Whatīs a typical EL84 PP impedance? 8k?|
IOF so, .0047uF across that will attenuate 4kHz about 6 dB.
I wouldnīt call that "transparent"
Not bad from a theoretical point of view, in practice it will be either a good thing (it kills buzz) or a bad thing (it kills sparkle).
Npt used by any classic amp, but some Forumites often have the urge to "contribute something" and post these ideas, as well as cascode stages (never ever used in Guitar amps) and similar stuff.
Pick your own poison, meaning try it and post results; experiment is real cheap-
Typical of Net level information, they did not bother to post a schematic or explain operation, just mention the Word of God with zero detail or elaboration.
|Chuck H||5/12/2018 6:20 AM|
|Well there's nothin' fancy about it except for the way it's wired (to look somehow symmetrical between the tubes?). See below.|
Other than that it's just a "conjunctive filter". Some guys hate that term, but it's the one we've come to know. You could wire it with a single 6k/5W resistor and a single 2200p cap for the exact same result. But then you wouldn't have those fancy Orange Drops and that symmetrical look that makes it seem like it's "balanced The truth is that very little consideration is given to this public offering WRT function because snubber circuits like this should take OT primary impedance into account and a scope should be employed for determining circuit values. It's just a masked face on an old circuit. But...
Before you think I'm poo pooing the whole thing, I use a snubber filter on my own el84 design. Dr. Z seems to like them for el84's also and has done quite well with them. I use a 10k resistor and a 1500pf cap with an OT primary of 8k. I don't know what Dr. Z does.
|Chuck H||5/12/2018 6:23 AM|
|Juan, it's wired with the caps in series, so it's actually .00235uF with a 6k series resistance parallel to the OT. Even still, it is NOT transparent. The more conservative snubber I use is not transparent.|
EDIT: Just looking at the components again in the image. What a silly thing that is. Sort of like making a face on your plate out of your bacon and eggs for breakfast.
|pdf64||5/12/2018 7:00 AM|
|RDH4 reference on p567 https://archive.org/stream/bitsavers.../n607/mode/2up|
The seemingly pointless symmetry of the circuit may be due to it being kinda copied from the Dominator http://wem-owners.com/wp-content/upl...nator-sch1.pdf but the OT primary CT connection omitted.
|Chuck H||5/12/2018 7:17 AM|
|Indeed! The circuit values look similar enough considering standard values. I think R.G. mentioned (more than once) that he thought snubbing to the CT was better than snubbing the whole winding.|
One other thing about the "kit" that I don't like is the use of cement resistors. Their specs indicate they aren't the best choice for high voltage applications. I went with something called a "high energy" resistor that I found at Mouser. I can't remember what it was It was rated at 11W and I chose it for it's voltage rating. And OD caps aren't designed as snubbers. Punch enough holes in the film and foil construction and the cap becomes a short (ask me how I know ) I chose to use a cap designed as a snubber with a voltage rating of something like 2kV.
|mozz||5/12/2018 7:38 AM|
|On the 18watt marshall forum, they use these "if" they have the problem of the output being fuzzy or fizzy or buzzy, however you want to describe it. It is a copy of the Watkins Dominator anyway as was said above. Solution looking for a problem?|
If you ran a freq response sweep of the output (or output and driver stage), you think any fizzy or fuzzy would show up? Maybe if using a speaker instead of a dummy load?
|Chuck H||5/12/2018 7:59 AM|
|Jazz P Bass||5/12/2018 11:23 AM|
|A good read: Tubes|
|g1||5/12/2018 1:23 PM|
|I've seen similar filters in some Garnet models, possibly Traynor also?|
|J M Fahey||5/12/2018 1:34 PM|
|Best known and most respected EL84 user?: VOX AC30|
Do they sound good? .... you bet.
Do they use snubbers? ..... are you kidding?
|Chuck H||5/12/2018 1:56 PM|
|Love it Juan. And I might take it personal if my amp wasn't designed to do things the AC30 doesn't And, to be fair, the AC30 incorporates more than one slightly goofy circuit of it's own. In principal you're spot on though. If a player can't make music of almost any genre with an AC30 then what's it going to take.|
|Steve A.||5/12/2018 2:04 PM|
|Justin Thomas||5/12/2018 4:20 PM|
|galaxiex||5/12/2018 5:34 PM|
|Thanks for the great reply's! |
Just in case anyone missed it, here's the Guitar player article.
|Chuck H||5/12/2018 8:24 PM|
|Justin Thomas||5/13/2018 2:13 AM|
|Oh, a Sovtek! (I still would rather have that Mig-100U than the '78 JMP 100W MV that had the JCM-800 front end)|
|Mick Bailey||5/13/2018 3:05 AM|
|If I had an amp for repair where someone had fitted components as per the instructions I'd want to cut it all out and build it up on tag strip. It looks like the mess you'd hang together just to see how it works before committing it to a proper build. Other than that, I'd only consider any kind of output filter if the amp actually needed it or if I was just curious to hear what something sounded like.|
The guitar world has plenty of products to fix things that aren't necessarily wrong in the first place. I went on a business seminar where one of the topics was "People are more willing to spend money on improving something they already have rather than buy new". The speaker went on to illustrate creating a perceived dissatisfaction with one aspect of a product, whilst promoting at the same time all the positive aspects. Then the closer was to sell a product or service that 'fixed' the problem.
|nickb||5/13/2018 8:43 AM|
I suggest that excessive voltage would be the more likely culprit especially if you consider the energy comping back from the speaker. Those kV rated caps seem like the smart choice for that reason.
BTW, those 8.2meg resistors are just a waste of space and money.
|Chuck H||5/13/2018 8:52 AM|
I did turn a 600V 715P into a dead short in this application. I had only considered the measured HV and not peak voltages on spikes. Looking into it I found that some Dr. Z amps were also failing their shunt filters. I took what I thought to be practical measures to avoid that problem in the future.
|Malcolm Irving||5/13/2018 10:11 AM|
|J M Fahey||5/13/2018 1:32 PM|
You donīt *really* need "protection" if you donīt visit the bad girls anyway
Meaning in technical terms: if rise time of signal driving power tubes is *squashed* (what the Cut control does, and itīs always there, even if set to nominal 0 ) then they wonīt be excited into driving OT and speaker inductive impedance hard and fast, which causes ringing.
So *maybe* AC30 does have a (sort of) conjunctive filter after all
|SoulFetish||5/14/2018 6:57 PM|
But when you hear him say it, you'd think he's just respectfully offering some technical reasons why my idea may not be the best approach.
as well as cascode stages (never ever used in Guitar amps)
|SoulFetish||5/14/2018 7:00 PM|
|Chuck H||5/14/2018 9:57 PM|
|J M Fahey||5/14/2018 11:53 PM|
The real trick there lies in making a powerful Class AB2 amplifier, "hidden in plain sight".
They can smash those grids with some 20mA on demand, any day of the week.
Grids can get as much as as 20 or 25V *positive* on them.
Al this goes well beyond any classical Cascode design, which usually delves only in relatively tame Class A1 .
So yes, the Music Man power stage is a Cascode.
But I was talking about Preamps, voltage gain stages.
No Guitar amp I know of used them, my comment/rant went to lots of DIY designs using them, most using Fets after Jack Orman got undeserved appraisal after he published as his own a Fet Cascode straight out of Siliconix (or similar oldtimer disappeared Semiconductor manufacturer) datasheet or App note.
It was published as AMZ Minibooster and caught like wildfire.
Soon after, everybody and his Brother started using it as a gain stage, thinking it equals a standard tube gain stage , which it does not, and then looping the loop a few designers started porting it back to the Tube World.
Just one example of the today common Cascode application and what they claim:
|Steve A.||5/15/2018 1:28 AM|
|J M Fahey||5/15/2018 7:00 AM|
|I guess WGS has to ship that individual speaker from their warehouse to your home, obviously using Mail or some commercial carrier, and pay full price end to end, while since GC has branches all over the place and has to supply them anyway, using their own distribution system to a nearby shop (95% of the trip) and then "a little more" to your home, way lower cost which can be absorbed even inside a narrow profit margin.|
OR, being a high volume shipper, they have an incredibly good deal with standard mail/freight carriers.
|SoulFetish||5/15/2018 9:06 AM|
|teemuk||5/16/2018 8:50 AM|
|Some guitar amps that use cascode: Vox V125 Lead, Ibanez Starfield series, Marshall 9001 preamp, to name a few. Of course they are bass amps but Aguilar’s DB750 and DB659 also employ multitude of cascode stages. They are not an extreme rarity. |
Of course the cascode is a poor choice if you actually want to capture characteristics of a single-ended triode gain stage since cascode’s going to have characteristics more similar to push-pull topologies. I think its commonly employed with FETs mainly because it minimizes struggles to match them. Not to mention it clips "softly" like tubes reputedly do (though it actually clips too soft and too symmetrically compared to generic SE common cathode circuit).
Back to real topic: I can instantly mention one “classic” tube amp with “conjunctive filter” and that is Dr Z’s Carmen Ghia. …Excuse me, (cough cough) I mean Hammond AO-35. There are some other vintage (guitar) amps where you can see the circuit used as well (though I wouldn’t consider them classics) and yes, Radiotron Handbook does explain why the circuit is used so it’s not just some snake oil.
Almost every solid-state amp will have such circuit too, as it is basically nothing but a “Zobel network” that compensates for increasing load inductance at high frequencies by adding parallel capacitance (and a current-limiting resistor). Can make marvels to overall stability and yes, by doing so also reduce the fizzyness of overdrive characteristics and crossover distortion. In some cases (such as this “snubber” –thingy) the circuit is tuned to operate at audio spectrum and plainly acts as a low-pass filter so yes, it removes even more fizzyness.
You will more likely encounter a conjuncctive filter in a tube HIFI amp than in a tube guitar amp, but yeah, most tube GUITAR amps do not even try to reach design extents of HiFi amps. They just pretty much use the simplest circuit that still works with modest reliability. But sometimes one needs to add a conjective filter to achieve that goal (e.g. Carmen Ghia).
|Pedro Vecino||5/16/2018 11:22 AM|
|Probably the most popular amp that uses it is the Pro Junior. |