S.I.R. 100W SuperLead Schematic pt. II

[Staalhoofd]

Me like the new amp.

And not just the price and the tone. I also like the selfbiasing gadget and the attenuator that actually keeps the tone. The fact that you switch between the two settings and switch in the FX loop, which could easily make it a great gigging amp.

I have my reservations about Marshall as well, but still think they tried hard to release a cool and original product that still is affordable. If I can get the cash I will definitely buy one.

[PuroMojo]

Me like the new amp.

And not just the price and the tone. I also like the selfbiasing gadget and the attenuator that actually keeps the tone. The fact that you switch between the two settings and switch in the FX loop, which could easily make it a great gigging amp.

I have my reservations about Marshall as well, but still think they tried hard to release a cool and original product that still is affordable. If I can get the cash I will definitely buy one.

+1 perfectly said!

[tschrama]

+1 on that... I like its looks too ..

[Roe]

this topic has really degraded. please focus on technical info

[Staalhoofd]

I guess we're all waiting for the AFD100 to come out. Once we pop the hood on that baby and draw up a schematic things will get back to basics, i.e. back to the technical info. Then we can start building our own AFD100's.

In the meantime I guess we'll just have to endure the crap.

[herbvis]

I think the afd 100 sounds good and has the vibe, but it is just generally close. I think the only advantage taht the afd100 has over us in the self biasing feature, but I dont really care about that. It is cool though. Any of us here could make our build 34/36 switchable if we wanted too, at least I would guess we could figure it out. I personally am very satisfied with my #36 clone and dont have any urge to purchase the afd100(unless I find a dirt cheap used one someday). I have been corresponding back and forth with Frank Levi a little and hopefuly he can chime in here very soon. In all our emails, he has stated that he has been very busy, but too keep in contact. I will shoot him another email and see if he has got a sec to leave some comments for us

Also, I know that Bennyx isnt the most popular guy here with some people, but his scom sample nails it. It doesnt get closer than that.

[paulster]

I know that Bennyx isnt the most popular guy here with some people, but his scom sample nails it. It doesnt get closer than that.

Perhaps if he posted some genuine technical information (since that's what this forum exists for) rather than the kind of playground taunts that effectively say "I've got something you haven't (and I'm not going to share)" then people might be a little more responsive.

Benny - if your spec is right and everyone else's is wrong then how about doing the decent thing and actually helping them to get it right? Otherwise all you are doing here is trolling.

[herbvis]

If you look at all of his hints and read inbetween the lines, there is some good info there

[jerrydyer]

exactly.. the best, closest schem has already beeen put up. The most important hint was its instability. A lot of guys think that if you dime a gain pot and it squeels then its all messed up....not true. The best tone for that higher gain thing lies right at the edge of instability.

[bennyx]

If you look at all of his hints and read inbetween the lines, there is some good info there

thanks Herb...

[D-Max]

The thread has become to a typical HC thread, not respecting other peoples opinions and bashing commercial products (is this jealousy or what?).

I pickd up a lot of got stuff here. Please keep it coming.

As the AFD100 amp has become point of discussion of this thread, here is my take on it.

1. The sample is great. very promising and want to try the amp myself when it's out. And very interested in seeing the schematic of it. Am I going to buy it? Depends on 2 factors: A. Money available B. a personal "drive test".

2. Did Santiago fail?
No, he managed to design and engineer a complete amp from scratch in half a year, making it ready for mass production. Yes, producing 2300 of these kind of amps in just a few months is mass production. No boutique amp builder can achieve this, let alone producing it in a PTP way. Marshall is no boutique amp manufacturer, probably never will.
Price? I don't care....
Once the product is out, watch out for this:



People can have their PTP versions from Malaysia, any other cloner or tech who reverse engineered it.
Tim Caswell knew he couldn't keep it a secret forever, he could only extend secrecy by using a PCB for his #39 mod which is less easy to reverse engineer than a PTP mod.

3. Did Marshall fail?
No. They set up a great marketing campaign, used 21th century media to inform the market. Other amp manufacturers are probably jealous on the exposure of Marshall's upcoming product is getting, strenghtening the brand awareness and visibility.
When there is more demand than 2300 limited edition units, perhaps it will be issued in the standard JCM cabinet. Who knows? The PCB's and components are now available.

4.What's really has got my interest is the additional functionality.

Auto bias is not new; in high-end audio this is already done for years with servo based electronics to control the bias. This can be an analog circuit with opamps.
The real fancy way is to control on output power (not bias current) and then programmable logic is the only way forward.
Been there, done that, still doing the high-end audio corksniffing, building amps with paper-in-oil power supply capacitors, multi CLC power supply filtering, high power triodes and high grade output transformers with amorph core material and silver wire on the secondaries.
And yet equipment with PCBs are not bad at all; it's just to expensive and time consuming if needed for a one-off build.
And it doesn't allow for tweaking what we all like to do.

Having designed and engineered mass produced electronics I know from own experience it is a pain in the ass to make a product that is also compliant to all the local and international standards in the world (RoHS, CE, FCC, etc).

Well, back on topic.


What really got me interested is Santiago's idea in one of the videos to work with the screen resistance to control the power.
That's definitely something else than power scaling. Power scaling brings down the voltage of the entire stage and the bias accordingly.

So here is my contribution. I have done some simulations:

1st plot pane
V(nfb) = [green] voltage at 8 Ohm OT tap (axis on left side, Volts)
V(nfb)*I(R2) = [purple] Output power -> into an 8 Ohm resistive load (axis on right side, Watts)

2nd plot pane
V(n006) = [blue] Voltage @ screengrid with respect to ground (axis on left side, volts)
I(R11) = [light blue] screen grid current e.g. current through screen resistor (axis on right side, Amperes)

3rd plot pane
(V(n003)-V(n006))*I(R11) = [red] Power dissipated by screen resistor

V(n003) is the high voltage after the choke, the supply for the screen grids. I(R11) is the
It's a 50W output stage, B+ @ 450V and Screen supply @ 438V.

Please note that all voltages and currents are AC values (peak, not eff.), so the power calculations do not result in RMS power values.

The first 3 screen shots show decreased power output by increasing the value of the screen resistors.
1. 100% output, Rscreen=1K
2. 30% output, Rscreen=10K
3. 10% output, Rscreen=22K

The last 3 screen shots show a seperate voltage applied to the screen resistors (standard value of 1K)
4. 100% output, Vscreen 438V
5. 70% output, Vscreen=350V
6. 22% output, Vscreen=200V

--------------------

1. 100% output, Rscreen=1K


2. 30% output, Rscreen=10K


3. 10% output, Rscreen=22K


--------------------

4. 100% output, Vscreen 438V


5. 70% output, Vscreen=350V


6. 22% output, Vscreen=200V


A Vscreen of 350V shows crossover distortion on the output and an asymmetrical signal what should be a sine wave.
A Vscreen of 200V shows dramatic crossover distortion and a mutilated signal.

When manipulating the screen grid, you have to mimic a resistance, so voltage and current. The voltage needs to be able to sweep from the lowest value up to the max. voltage, not a lowered voltage.

So, I am interested how they implented their power control.
Anyone have a clue?

P.S. After running the simulations I also understood why the 2203KK uses screen resistors of 2k2 Ohms... to protect the OT by lowering the output of the quartet of KT88s.

[herbvis]

I think it was mentioned that the power scaling feature is probably a post phase inverter mv with a fancy name. I posted on the afd site to see if they would confirm or deny that, so hopefully they will respond.

The main thing that bothers me about the afd100 is the more new school vs old school technology being put in it. I work for a company that makes electronic medical devices, so I know first hand that there is always a pretty decent amount of unexpected failures and other unknowns that can go wrong with new products. And that also applies to mxxxhall amps as well. I remember when the JVM came out, there were a lot of reports of out of box failures. Also, I blew up 2 vintage moderns. THe first was within an hour of owning it, i dimed the volume and boom! The second one same thing, of course I waited a few months to try that again! Anyways, just my 2 cents The only thing that really intriges me about the amp is the self biasing tube feature, That is pretty cool, But I can live without it.

[shawnee]

I know that Bennyx isnt the most popular guy here with some people, but his scom sample nails it. It doesnt get closer than that.

Perhaps if he posted some genuine technical information (since that's what this forum exists for) rather than the kind of playground taunts that effectively say "I've got something you haven't (and I'm not going to share)" then people might be a little more responsive.

Benny - if your spec is right and everyone else's is wrong then how about doing the decent thing and actually helping them to get it right? Otherwise all you are doing here is trolling.

I'm with Paul in this. Everyone is sharing info here -except him., without reading btw lines or playing a puzzle game of his guessing. By now, how long would that take even for a non-tech person (what he states he is...) to take the top off and shoot a picture? Probably 10 minutes. Still, I feel if someone would come up something he would be the first one to implement it. Find him on other Forums and read his other comments....why I have a feeling that he wants to be the "first one" and get raves and applause by others? ...How many more cheering comments does he need about "his invention" (is it?) while I admit that his amp sounds cool (like others as well here!). I am glad others behave differently here.

Back to the topic - i like the sound of the new AFD100.

[bennyx]

Benny - if your spec is right and everyone else's is wrong then how about doing the decent thing and actually helping them to get it right? Otherwise all you are doing here is trolling.

if herbvis spent some good words about me is because something good has taken

the aid there, just thinking
the 36 is much easier than it looks

and regulation of amp is the same of illusion

[ryu]

I'm not sure if this has already been posted but anyway...