agedhorse

16 hours ago, namefail said:

Cheers BlueMoon, I found that website too. interesting to hear they were formed around  2000 for some reason I thought they were older.

The company behind the product itself is an older, established firm. Indie was a brand that this company manufactured, the guitars were actually quite high quality. 

Speaking of fur and such, going back decades acousticians used to refer to sound absorption or anti-reflection as "dead cats". If you needed to reduce the reverb time, you would stick some more "dead cats" on the walls. Not a very PC way to describe it though.

What about that "fur" thing that's draped on the back of your couch (chesterfield?) That looks like it will work...

On 01/12/2020 at 13:54, abarson said:

Hey @agedhorse

You're over here too? How do you find the time?

In between plotting out CAD drawings. No more touring shows (or even local live shows) these days, so this is about as close to "the road" as it's going to get for the foreseeable future. 

Actually, if you add 6dB of bass boost, you reduce the power handling by a factor of 4 because 6dB of power increase is 4x the power and 2x the voltage. 

Yes, I am familiar with the brand and somewhat familiar with the amp. For what you paid, I think you got a heck of a deal.

You have received in depth answers to your questions on both TB and here... never mind.

15 hours ago, Woodinblack said:

Agreed it is easier to do with a signal an octave lower than the speaker was designed to handle. Maybe when TC made the RH750 and matching cab they thought that they might be used together?

As I said, all of what you are saying is true for other amps and other speakers, and I have no questions on that. The RH750 has Active power management (that it is often slagged off for) which means it will never produce more than 35V (see attached) without clipping (as it peaks), and it has (according to talk bass where it was tested - I have no other sources) a 2nd order HPF starting at 70Hz at 12dB/Octave.

It is incapable of producing a 'signal an octave lower than the speaker was designed to handle' as literally the speaker was designed to handle the output of the RH750.

Add as a caveat to that, the HPF is only in the power amp, so if you take the output from the DI or the preamp out, and put that through an amp, then yes you really can damage it.

I don't see there is much point adding anything else to this, although seeing as the TC RH amps are very common and most of the time paired with the RH cabs, I am obviously happy to see links to all the 'my amp broke my speaker' threads that must exit.

To the OP, don't put any bass into any speaker, as apparently it is far too risky as none of them can handle it.

 

tc450 stats.pdf 590.44 kB · 3 downloads

This is accurate as far as transients are concerned, but ignores the fact that as you limit the peak amplitude, this allows for an increase in average power. For example, a reduction of 3dB of transients allows for a 3dB increase in average power. The ear perceives average power as loudness. This is one reason why tube amps appear to sound louder than their power might suggest, and also one reason why compression is so useful.

With an increase in average power,  the risk to the speaker transitions from mechanical to thermal assuming there is an effective HPF involved.

5 hours ago, jjl5590 said:

Is this directed at me?

Yes.

Then why did you bother asking this question if you already knew the answer you wanted to believe? 
 

There’s a lot to learn from the answers and comments that were made my members here and on TB, it appears you have missed the essence of this information.

On 17/11/2020 at 09:40, Phil Starr said:

Bill's right, the other problem is the nature of the suspension, in an instrument speaker the suspension is likely to be progressive stopping the cone from leaving the magnetic gap. The roll surround will be designed for linearity. I've had a look at WinISD and this is the frequency response. I've assumed 9l for the cab volume the same as mine. The green plot is the Fane and the red the Farnell/Monacor.

You get a lot more deep bass out of the hi fi speaker and it's flatter in response, what isn't shown here is that below 50Hz and with just 20W input it exceeds the excursion limits by a lot and this would lead to failure of the speaker in short order without an HPF. this isn't a problem with the Fane (or the other PA/bass drivers) I'm guessing that's why they rate it at 35W

The Monacor is probably going to sound fine and will be an improvement on what you have which won't handle bass either but i don't think it will last long if you play it at any volume. £28 isn't much more than a set of strings so I'd still go for the Fane.

IF the cabinet tuning resulted in the same curve shape (translated to filter terms this would be Q and slope) than the red trace has the potential to provide better performance with both tuned to slightly under critically damped. Now the elephant in the room is what the relative sensitivities are between those two drivers (which would be the gain term of the filter equation). Is the red driver significantly lower sensitivity than the green driver by chance?

Have you looked at the comprehensive answers and information given to you over at your same thread at TB???

7 hours ago, Chienmortbb said:

Spot on again @agedhorse I think the classification Class AB is very misleading, as it almost implies that the power stages of the amp are operating in Class A at some point.

Kind of yes and no. Whenever the conduction angle of each side of the push-pull pair is greater than 180 degrees, as some low level of signal one half will be sourcing current while the other half will be sinking current throughout the full waveform, and technically that's class A. BUT, often the distortion can be worse because the handoff from the positive to negative half may not have the identical curve shape so the distortion can actually increase where these curves overlap and under this condition it's possible for class B (if the ends of the curves just meet) can have "better" (lower) distortion characteristics.

This is something that Doug Self did a lot of research on maybe 20-25 years ago. The challenge is that the bias point at 100Hz may be different than at 10kHz, therefore a happy medium must be arrived at, usually that ends up slightly over biased at low frequencies for adequate bias at higher frequencies. In practice though, this is of no consequence.

Proper class B has almost no crossover distortion, but the challenge is to keep the bias conduction angle the same across the entire audio spectrum. At higher audio frequencies, sometimes additional bias is necessary to insure no crossover distortion which leads to more than enough bias at lower audio frequencies. This is an example of why often a single bias value is not adequate, and by biasing slightly into class AB at DC (and lower audio frequencies) to be sure that the operation at higher audio frequencies is adequate for at least class B operation.

On 16/04/2012 at 03:08, Toasted said:

Any help chaps?

What exactly is the question?

3 hours ago, [email protected] said:

i had that same question. class g uses two voltage rails while class h changes the voltage in the rails. i could see class g being called two tier because of the two rails but i don't know why class h would be called that. and by the way, they are ab amps until they need the extra power. and no they don't have the distortion issues of class d. i've done homework and own class a class ab class d and class h amps. the only one i am not too happy with is the class d. i have powered pa speakers with ab for the mids and highs and class d for the bass. those sound good. 

Both class G and Class H have multiple rails (can be either 2 or 3 tiers), both operate as class B/AB until approaching the rails at which point either the lower rail hands off to the higher rail or the signal hands modulated the higher rail into the lower rail. They can in fact have terrible distortion issues if the rail handoff (called commutation) is not done well.  the terminology of class G and H are interchanged in definition depending on where in the world you are located. In the US, class H commutates the rails, class g commutates the signal tier.

Class D amps do not have the distortion issues that you claim, you may not be happy with your class d amps, but not for the reasons you state because the distortion numbers are very close between good class d and good class AB/G/H.

6 hours ago, BassmanPaul said:

You will need a separate speaker system on each amp.

This is a critical bit of information IMO. 

5 hours ago, thebassist said:

With the Acoustic Image Clarus SL and the GSS Baby Sumo, I don't really understand why any amplifier needs a fan nowadays frankly.

Perhaps I can help you understand why some designers choose to use a fan?

Neither of the amps you listed are rated for 2 ohm operation, and neither are rated for as much power (RMS) either.

When considering cooling strategies, my general goals (and others with similar philosophy) might choose to insure that their products are capable of operating at a higher duty cycle into a lower minimum impedance at higher ambient temperatures (I typically use 105 deg F) than other designers might choose to use. Also, the warranty offered often factor into the decision. The companies I have designed for over the years have offered longer than average, which predisposes me to a more conservative approach.

I do work hard to minimize fan noise, but a small amount will always be present.

If a fan bothers you enough, simply choose an amp without a fan and accept those compromises compared with the compromises of using a fan (noise)

54 minutes ago, paul_5 said:

£22 on some deoxit spray or £10 (maximum) on 2 new pots and ten minutes to solder them in...?

Assuming that no new damage is created. That's another topic, but I see folks try to do this kind of repair and damage otherwise perfectly good PCBs because they don't have the proper tools or experience to work on double sided PCBs (the norm now).

Generally, IF THE POT HAS NOT BEEN CLEANED WITH "MIRACLE CURE-ALL" CLEANER, dust is not a problem with the rotary pots. What can be a problem is microscopic insulating layers of oxides and sulfides that are angstroms thick, just thick enough to inhibit reliable contact with the fingers of the pot's wiper element.

DeOxit D-5 in particular is quite effective on this without damaging the conductive element (especially at the terminal rivets), but liberally applied will wash the lubricants from around the bushing onto the conductive track which will attract abrasive debris and grind the track and fingers into oblivion. 

Other substances can do this as well, but also damage the conductive surface, making it MUCH more vulnerable to wear. Some techs refer to such substances as "disaster in a can", because when they work on amps that have been serviced this way, they often can become disasters. A full set of pots on some amps can push the cost of repair beyond the realistic market value of the amp. 

If it's the can that comes with the small removable tube that sticks directly into the nozzle it's not to bad, but the new style with the swivel is a real pain and you have to have just the right touch. Also, NEVER spray down the shaft (no matter what you might have seen on the internet). That's a quick way to ruin a complete set of pots as it washes the bushing lube everywhere it doesn't belong.

I see units with spray residue all over the PCBs, and this attracts little conductive bits that then provide leakage paths. This is especially true on circuits with very high voltages and also very high impedances. Once this happens, the PCB must be removed and washed in an approved solvent to remove the oily residues. Then the usual production wash in a saponifier with a DI or distilled water rinse and mild temperature (like 120-130 deg F) bake dry. Pots and switches (and anything that can't be washed in production after wave soldering) must be protected. Different parts have different requirements, which is why I try to avoid this and when it happens it's costly to remedy because it takes a lot of time to do right. In my shop where I still service Genz Benz products, I know what parts are safe to wash and what aren't, but even then it adds between 30 minutes and an hour to a repair. It's one reason why I discourage DIY repairs, they are MUCH harder to correct and repair right. The other reason is that we have to examine the amp closely for any additional, hidden repairs that may jeopardize reliability in the future. Everything that goes through our shop carries a 90 day service warranty and I don't want to see any repairs back because I missed something. Generally I can keep it to one or less service re-work per year because of this policy.

Hope this helps.

On 05/11/2020 at 11:17, MOSCOWBASS said:

DeOxit 5 is available in the Uk. I have some, bit it's not cheap!

Yes, often "not cheap" goes along with very good.

A little bit goes a very long way.

Use the TINIEST amount of cleaner, less is more in this case. In the US, DeOxit D-5 is the only substance that I have tested extensively with no long term (over 20 years) issues. I do see a lot of pots for units in for service that were cleaned with a variety of "miracle cure-all sprays" that have subsequently become ruined (either from the product, or from over-application which washes incompatible lubricants into places that causes additional damage). 

I do not know if there are equivalent products across the pond, but based on what I have seen acceptable products are few and far between.

When using the FET channel, there should be a delay of about 3 - 4 seconds.

I can pretty much guarantee that it has nothing whatsoever to do with capacitors (regardless of all the bad advice on the internet). In 12 years, I have never seen a bad cap on a ShuttleMax and I handle all the factory service/support for North America.

By any chance do you have the amp set for the tube channel only, and you are waiting for the tube to warm up? That's about  the right time for this to happen.