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Bugera all tube head

#62
seamonkey said:
All tube path designs are all the same design, same circuit. There's only so much you can do with the same old tubes. There is no intellectual property left. There's nothing tricky. It's all published in books. It's just sourcing parts and creating manufacturing methods to put them together. B* has got this down. Their guitar amps have a big following.

This might in fact be a copy down to the clipping diodes of an SVT. If there's no IP left, what's it matter. Same amp but cheaper.
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Guess I didn't make my point all that clearly probably due to wording it strangely, but what I meant about tube designs being tricky, is that if you build it poorly, it probably won't work well, and will inevitably fail. Overall I see the main difference between an Ampeg original and a B* clone coming down to three basic things:

(1) Component quality. To cut costs B* will be using cheaper components whenever possible. Ampeg might not break the bank on components either, but B* will go cheap all the way.

(2) Build quality. Cheap, fast soldering equates to shoddy connections that over time, will fail. I'd be willing to bet most of the B* amps that die on gigs are a result of poorly soldered connections that fall apart during transit.

(3) Quality control. Less thorough QC equals more problems cropping up during the lifetime of the product. When you factor in the cheap components which probably had very little QC to begin with in the factories they were built in, add to that generally shoddy constuction, and THEN factor in some crap QC at the B* factory, it begins to make sense why these amps have such a consistent reputation for dying when you need them most, typically after very little use.

B* also is able to cut costs due to the relative lack of R&D that goes into designing their products (since most are copied designs). That and not having to market as extensively as Ampeg, and all of the above build-related expenses more or less explains why they can offer the "same" product for much less money. But as they say, and as my past experience with this company has definitely confirmed... you get what you pay for.
 
#63
seamonkey said:
All tube path designs are all the same design, same circuit. There's only so much you can do with the same old tubes. There is no intellectual property left. There's nothing tricky. It's all published in books. It's just sourcing parts and creating manufacturing methods to put them together. B* has got this down. Their guitar amps have a big following.

This might in fact be a copy down to the clipping diodes of an SVT. If there's no IP left, what's it matter. Same amp but cheaper.
Click to expand...
right. and that's exactly why all tube amps sound exactly alike.

:rolleyes:
 
#64
SpamBot said:
I saw this and thought, "***?", but looked up the schematic and lo and behold, two diodes just before the inverter stage. Why on earth are those there?
Click to expand...

I haven't seen the schematic but they could be used as a sort of limiter or they could be there to add distortion when hit with a large enough signal to get them to conduct. Are they across the signal path or ???
 
#65
ishouldbeking said:
Guess I didn't make my point all that clearly probably due to wording it strangely, but what I meant about tube designs being tricky, is that if you build it poorly, it probably won't work well, and will inevitably fail. Overall I see the main difference between an Ampeg original and a B* clone coming down to three basic things:

(1) Component quality. To cut costs B* will be using cheaper components whenever possible. Ampeg might not break the bank on components either, but B* will go cheap all the way.
Click to expand...

You are just guessing here. I would guess that B* is a large scale manufacturer and has first pick at the high quailty parts. Every tube sellers talks about how the measure and only keep and sell the top 10% of the tubes or parts they get. First in line gets the best parts. B* being larger than LOUD is probably getting first pick.

ishouldbeking said:
(2) Build quality. Cheap, fast soldering equates to shoddy connections that over time, will fail. I'd be willing to bet most of the B* amps that die on gigs are a result of poorly soldered connections that fall apart during transit.
Click to expand...

Again - speculation on your part. B* invests a big in automation - check the videos on Behringer city.

ishouldbeking said:
(3) Quality control. Less thorough QC equals more problems cropping up during the lifetime of the product. When you factor in the cheap components which probably had very little QC to begin with in the factories they were built in, add to that generally shoddy constuction, and THEN factor in some crap QC at the B* factory, it begins to make sense why these amps have such a consistent reputation for dying when you need them most, typically after very little use.
Click to expand...

Again speculation your opinions - you can have them, I do, And I see they do have QC. Check the videos. They actually play through every amp before it leaves the plant. I've taken B* stuff apart and say for the price they use the same components gear selling 2 to 3x as much uses.

ishouldbeking said:
B* also is able to cut costs due to the relative lack of R&D that goes into designing their products (since most are copied designs). That and not having to market as extensively as Ampeg, and all of the above build-related expenses more or less explains why they can offer the "same" product for much less money. But as they say, and as my past experience with this company has definitely confirmed... you get what you pay for.
Click to expand...

Ha - no - check their offerings they had 50 new products of their own design at NAMM. Try to copy one and they will sue your *ss off.

Sure they copied SVT for this Bugera. But who cares about some 60's technology. These guys comparing car engines here - look at car engines in the 60's - not of lot of IP that has anything to do with today's car engines.

B* looked inside a SVT and figure out a way to make them just as good but cheaper. You'll see - they will be big sellers. And they'll be just as reliable as you could expect from any tube amp. They will be a big seller in this niche market.
 
#68
ishouldbeking said:
I'd agree with you in theory, though Bugera/B*hringer aren't known for making products with "kinks in the beginning". They have a consistently horrible track record from start to finish, with the exception of a handful of products that randomly seem to work.
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That's pretty much how I feel too, however, living outside of the US it is very difficult to find fairly priced, let alone affordable all-tube amps (fingers crossed on the Peavey Classic 400 and the Mesa 400+ until I can get a spare $1K!).

We can expect to pay double or more if we buy locally or else DIY it from the US and get gouged on the shipping, import duty and mods (where voltages differ). Simply put, there are no bargains (that said, the world of micro amps and Class Ds, Genz Benz and the rest with their multi-voltage inputs etc do allow us to stick it to local gangsters on one level).

As a result, I bought a Peavey VB-2 and am more than happy with it, however, it is hard to resist the temptation for more tube-y power and that's why clones (and even rip-offs) are so passionately welcomed by myself and others. Issues of legacy aside, on paper at least, the new generation of generic tube amps do look attractive.

Now we only have to wait and see if they hold up.
 
#69
SpamBot said:
I saw this and thought, "***?", but looked up the schematic and lo and behold, two diodes just before the inverter stage. Why on earth are those there?
Click to expand...

Someone could easily add a switch to switch the diodes in and out.

Then do a double blind test to see how the affect the sound.

Silicon diodes break over .7v (1.4v PP) a cranked preamp can easily do this. Diodes in this configuration add "soft clipping"
 
#71
B-string said:
Looks like a DC block to prevent DC leakage from a master amp while slaving two or more units. Any DC leakage from a weak coupling cap would cause severe problems to the slaved amp.
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Perhaps, but I'm guessing that it functions as a limiter. Note that this is Joe Piazza's drawing of the original SVT power amp configuration (with 6550s), not the SVT-CL. One should check an original SVT schematic as I've found errors in Joe's redrawn schematics before.
 
#72
BillyB_from_LZ said:
Perhaps, but I'm guessing that it functions as a limiter. Note that this is Joe Piazza's drawing of the original SVT power amp configuration (with 6550s), not the SVT-CL. One should check an original SVT schematic as I've found errors in Joe's redrawn schematics before.
Click to expand...

I second the motion about the diodes functioning as a limiter, but by the time they kick in, the power amp is already clipping.
 
#73
as stated above, i think that they're for protection in the slave amp circuit. here's a scan that i made of one of mine ( early 6550 version). the 6146 schematic also has them.

SVT-poweramp_scan.jpg
 
#74
I see them in my copy of a Rev.B '69 schematic. I have little doubt they will provide some limiter function. The input to the power amp was/is bundled with multiple DC supplies and you notice no decoupling cap from the molex on the power amp (or "power amp" jack) to the first grid? This is where my thinking was.

Thanks JohnK haven't even seen my scanner since moving? ;)
 
#76
The diodes are at 0 volts DC, and there's quite a bit of local feedback in the first stage, the second stage is the phase splitter, and the third section is a cathode follower driving the grids (no voltage gain) with some bias coordination.

I do not think there's enough gain for the output stage to be driven into clipping before the diodes begin to conduct, their conduction slope (compression/limiting/distortion) along with the natural clipping of the output stage when pushed harder, will most likely result in a good part of the overdriven sound of this amp.

Sometimes there's more to a circuit than meets the eye, and in this case I think I know WHY they are there and WHY they improve things for the intended market, but since I didn't design the amp, it would be pure speculation on my part. The guys who originally designed the SVT platform are REALLY sharp guys and the one that I know is absolutely qualified to make whatever design decisions he want to... and they have earned (and continue to earn) this respect.
 
#80
B-string said:
Agedhorse, that sounds like: "Sit down, shutup and hold on"? ;)
Click to expand...

Nope, and certainly not in any insulting or condecending way. It's just an interesting circuit with some clever (especially for it's time) twists that are not all that obvious. This is especially true with the biasing and what looks (on the surface anyway) to be some kind of bias compensation going on.

I have not analyzed this circuit, just providing some off the cuff comments based on what it looks like to me.
 

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