Santiago Alvarez (electronics engineer, JVM, YJM, AFD...)

headcrash said:
Thanks Santiago, for the insight!

For me it wasn't boring at all, since this answered my questions :)
I'm an electrical engineer as well, and we are about similar age, I guess (was born in 1975). So we've kind of witnessed the "history of development" of rather complex tube amps also from a rather technical point of view.

For my 6-months diploma internship I worked at Stamer Musikanlagen, back in 1998/99.
Stamer was and - to my knowledge - still is the manufacturing company for, or behind the brands Hughes & Kettner, HK Audio, among a few others.
They already must've been quite ahead in the mid-90s, for a still rather young company then. AFAIR, they used soldering and population automation, when I was there. Which of course is a consequence of the quantities of units you want to manufacture profitably, in a given period of time.
Also I vaguely remember a copper cladded EMC testing lab...

However, in the mid 90s suddenly we had 3 or 4 channel switchers, like the Diezel VH-4, ENGL Savage 120, or, well, Hughes& Kettner Triamp Mk I, (just to name a few). Apart from "simply" getting such an amp to work and sound good, all other fields you mentioned above, must already have been quite challenging, even back then.

For me as a hobbyist amp builder, who doesn't sell his amps or services, it's all about getting an amp to work and sound good, and that I or others won't get hurt, when it is connected to power.
I can barely estimate how much time and effort has to be put in a product to meet as many worldwide standards as possible.
I wonder how smaller companies like, for example Diezel do this, they're only 4 folks (!). In the end, it must be - like you said - "just" learning by doing (and allowing to fail, which is another meaning of "learning" :grin).
Click to expand...
back in the day it was much easier to comply with safety and EMC as the requirements were much easier to pass, if they actually existed at all. For example, what importance had the 2.4GHz area in 1989, or what importance had the power used by AC adaptors when nobody used them, etc. One also has to wonder how dangerous it could be if there were no requirements at all haha.

H&K were quite innovative back in the 90s although somehow they never really 'made it' to the top and remained as a good brand, somehow popular in Europe but not much more I think.

Smaller companies probably start like you or I would do, making a handful of amps here and there that you sell to your circle, then you invest the money you make and increasing your sales and testing, etc. or you are lucky and someone invests in your business. Tube amps are relatively easy to comply with safety (usually some heat issues here and there and a couple of minor safety problems, EMC is quite easy as normally there is not much computer work in there nor switched mode supplies or other 'noisy' circuits)
 
Hi Santiago,

Please to be able to ask you a questions

I have a Marshall JVM205c which i bought in 2008 and have always loved the tones i get from it.

I know the 2 Series OD Channel is based on OD2 rather than OD1 from the 4 channel versions, and has the scooped mids centred around 500hz rather than the traditional 650hz

From a pure experimental/educational point of view, short of modding it which i am not really interested in at this stage, what EQ'ing could i do (Parametric or Graphic) to get quite close to OD1 with the 650hz centred mids. I know it won't sound exact but i'd imagine you can get relatively close.

Apologies if the answer is quite obvious, i'm definitely not an expert when it comes to this stuff.

Thanks in advance !
 
MetalShredder94 said:
Hi Santiago,

Please to be able to ask you a questions

I have a Marshall JVM205c which i bought in 2008 and have always loved the tones i get from it.

I know the 2 Series OD Channel is based on OD2 rather than OD1 from the 4 channel versions, and has the scooped mids centred around 500hz rather than the traditional 650hz

From a pure experimental/educational point of view, short of modding it which i am not really interested in at this stage, what EQ'ing could i do (Parametric or Graphic) to get quite close to OD1 with the 650hz centred mids. I know it won't sound exact but i'd imagine you can get relatively close.

Apologies if the answer is quite obvious, i'm definitely not an expert when it comes to this stuff.

Thanks in advance !
Click to expand...
Hi, the difference in the tone controls is actually very small, you'd need to apply a correction as per this curve:
Screenshot 2023-01-15 124845.png

what you won't be able to correct without modifying the amplifier is the 'pre-overdrive' bass, as that's defined by the components around the gain control. OD2 has less bass to make it tighter.
 
Santiago, during the redesign of the 2555x and design of 2525, did you ever dabble at the influence of LEDs and/or diodes on the sound as far as the tolerances, or even LED size (3mm or 5mm) is concerned?

Reason I ask is, last week I played the "real things" of two of my clones (Jubilee and SLO).
I found both the 2555x and 2525H, they had at that store, were quite trebly and scratchy compared to my clone. Of course I didn't have it with me to do an A/B comparison, but it was rather obvious to me.
Some years ago I somewhere read, that especially with LEDs, tolerances can be a thing. If so, I could imagine with the LEDs contributing to the character of the distortion by a certain degree, a certain deviation here may change the character for the better or worse.
Also AFAIK, the old models (and my clone) use 5mm LEDs, and the reissues use 3mm.
 
yeah, we did our due dilignecy and A/B all the time the prototypes with the Jubilee that they had in the museum. Both amplifiers sounded and measured the same when set appropiately, with this I mean not with the controls at exactly the same positions but taking into account that old pots for example had much broader tolerances. People having them on the road also fedback that they took out the original jubilees and replaced them with the reissue.
In general, all reissues tend to sound brighter due to 'better' components and age.
I also would not say that the LEDs are 100% to blame as we experiemented a bit and I don't remember them being like day and night at all. They are in series with more diodes and filtered with a 47k/1n RC (3.4kHz or so) so much of the harshness is removed there and then everything filtered by the tone controls (which are very effective in the jubilee).
Probably the age of the speakers has much more to say against the brightness than the LEDs
 
Thanks Santiago!
I was mainly referring to my clone I built in 2017, compared to the two - most likely - newer specimens in that store.
The trebly-er sound of the two new ones could be dialed out by the treble pot, and may also be due to pot tolerances adding up.
Also my PCB layout is different, of course, that may also play its part.

But what I could not quite dial out was that scratchyness or harshness of the distortion. This led (pun...?) me to think about the LED's influence.
Do you know whether the amps leave the factory rather cold biased or more in the "normal" area?
This may contribute to some harshness. But on the other hand, the Mini Jubilee is cathode biased, so there won't be any wiggle room...
 
Santiago, another few questions came to my mind the other day, and I hope this hasn't been asked and answered too often in other places...

When starting the AFD 100 project, it seemed to be clear that nobody knew, where the original amp is, if it still existed a.s.o.
There may already have been quite some internet gossip around the circuit, maybe also some schematics floating around.
Also Frank Levi and Tim Caswell may have been talked about (...just can't keep in my mind, who did what, and which amp is/was #36 and which #39, but that's another story...).
Apart from listening and examining the master tapes, did you try to contact Frank and/or Tim? Or maybe some folks that have been working for SIR back then? Did you study the schematics, that may have been floating around when you started the project?

As far as listening to the master tapes goes: was it 100% known, what cabs and mics were used, which speakers were in them, where the mics were placed and so on? How would you and Slash "translate" the sound you heard from the prototypes to that already mike'd sound from the master tapes?

By the way, why has afd100.com been taken down?
 
headcrash said:
Santiago, another few questions came to my mind the other day, and I hope this hasn't been asked and answered too often in other places...

When starting the AFD 100 project, it seemed to be clear that nobody knew, where the original amp is, if it still existed a.s.o.
There may already have been quite some internet gossip around the circuit, maybe also some schematics floating around.
Also Frank Levi and Tim Caswell may have been talked about (...just can't keep in my mind, who did what, and which amp is/was #36 and which #39, but that's another story...).
Apart from listening and examining the master tapes, did you try to contact Frank and/or Tim? Or maybe some folks that have been working for SIR back then? Did you study the schematics, that may have been floating around when you started the project?

As far as listening to the master tapes goes: was it 100% known, what cabs and mics were used, which speakers were in them, where the mics were placed and so on? How would you and Slash "translate" the sound you heard from the prototypes to that already mike'd sound from the master tapes?

By the way, why has afd100.com been taken down?
Click to expand...
The AFD amp saga in the internet goes back to when the internet news started and there were those amplifier groups. I remember very well reading about it back in the late 90s. It was quite clear that the amp was a 2203 (or a 1959T modified to a 2203) with an extra gain stage that should be pretty much a duplicate of the existing gain stage so on that side it was clear where to start. I didn't need to study much from zero as I was familiar but of course we did our refresh, it would be stupid no to.

There were internal talks about letting third parties collaborate but the problem was that once the project was made public, a few people approached the company asking pretty much for money, for credits and so on (not talking about Frank nor Tim here). There were also all the potential legal implications between record companies, Marshall, Slash's side and so on so it was decided to keep it as closed as possible. Public development but closed to third parties.

Nobody really knew what cabinet, mic, etc. were used... The general consensus was that they were probably greenbacks just because V30s would be too new back then and one would assume that when they got the amp it came with some sort of Greenback inside but the development was done with V30s by Slash's request. Anyway, nobody discarded that they were some other speakers in there. Mics... nothing was certain but most likely the usual SM57 and then some sort of AKG421 and/or some ribbon. That's what I remember from Eric Valentine when talking about all this.

No idea about afd100.com at all, I didn't even know that it was even online in the past years?
 
Thanks again for the insight!

Apart from Greenbacks in the late 70s and early 80s there were already several higher power speakers (other than GB's) in Marshall 4x12 cabs, that could have found their way onto the record. But who knows... :idk:grin

As far as afd100.com goes: I think it has been down a few years already, but many of the movie clips, if not all can be found on YT, on Marshall's YT channel.

While I was watching some of these, I wondered, wether anyone has ever seen Slashs eyes :rofl
 
headcrash said:
Thanks again for the insight!

Apart from Greenbacks in the late 70s and early 80s there were already several higher power speakers (other than GB's) in Marshall 4x12 cabs, that could have found their way onto the record. But who knows... :idk:grin

As far as afd100.com goes: I think it has been down a few years already, but many of the movie clips, if not all can be found on YT, on Marshall's YT channel.

While I was watching some of these, I wondered, wether anyone has ever seen Slashs eyes :rofl
Click to expand...
sure, it was all guess-work. What it was clear is that we were going to use V30 speakers.
I have seen Slash's eyes hahaha
 
Hi Santiago!

I recall reading your comments on the JVM forum back in 2007 or 2008. I was 20 years old and trying to save as much as possible to buy my first tube amp. So I got a brand new 2008 JVM410H + 1960A (75's) at guitar center back in the day.

I still have it and it is all stock. Even the original tubes are original ones which are no longer made, right?

I have some questions for the master mind:

What was the speaker used during the design process of the JVM series? Do you have any particular speaker that you think the amp shines through or best suited?

Why does the combo versión has 2 speaker types? What is the story behind? Why those?

Clean channel is really good and not seen previously in any other model. How did you come up with that? I like clean red for leads.

Things have changed eversince the JVM was release. Nowadays, pedal industry and pedal platform amps have been very popular. What do you expect for the JVM in the future? Will it be a classic amp? Will it be discontinued? Is this a matter of fashions? Do you forsee any upgrade to the current models?

Thank you so much for your contribution to music.

Pablo González Kettenhofen.
 
Pablo González Kettenhofe said:
Hi Santiago!

I recall reading your comments on the JVM forum back in 2007 or 2008. I was 20 years old and trying to save as much as possible to buy my first tube amp. So I got a brand new 2008 JVM410H + 1960A (75's) at guitar center back in the day.

I still have it and it is all stock. Even the original tubes are original ones which are no longer made, right?

I have some questions for the master mind:

What was the speaker used during the design process of the JVM series? Do you have any particular speaker that you think the amp shines through or best suited?

Why does the combo versión has 2 speaker types? What is the story behind? Why those?

Clean channel is really good and not seen previously in any other model. How did you come up with that? I like clean red for leads.

Things have changed eversince the JVM was release. Nowadays, pedal industry and pedal platform amps have been very popular. What do you expect for the JVM in the future? Will it be a classic amp? Will it be discontinued? Is this a matter of fashions? Do you forsee any upgrade to the current models?

Thank you so much for your contribution to music.

Pablo González Kettenhofen.
Click to expand...
Hey Pablo, congrats on the amp and thank you for the compliments :)

The original tubes where the Svetlanas with the =C= logo, yep, no longer made anymore. Quite good ones.

Speaker... I mainly used a 4x12 with G12T-75 in it. It was the 'standard' Marshall cab so it made sense to voice the amp with it. I did of course try the amp with the other options (V30 and Greenbacks) but the main one was the 1960 with G12T-75, I actually think the G12T-75 is a very good match for that amp, some people don't like them but it would probably be my choice. People like Satriani also ended selecting the G12T-75 for the original JVMs and also for his signature later on.

The combo story is quite simple. The TSL 2x12 combo had those speakers inside, we tried and we kept them. No other reason. What I don't know is why they had those speakers in the TSL to begin with although I guess it was to tailor a little it the sound of the open back.

The clean channel is my take on a Fender circuit, a bit tighter than the Fender if you overdrive it and with an EL34 power amp. The 30th Anniversary had a similar circuit although I always found it a bit 'dry', perhaps too clean, so I added more harmonics to the one in the JVM. Clean Red was the result of experimenting with the circuit, there were some extra tubes not being used and I think it can sound quite vintage if dialed properly. Many people don't experiment much with it, just crank the gain full in Red mode and expect a 5150 or something :D. To me it shines with the gain rather low, then using the tone controls to shape the distortion.

Well... somehow I believe the JVM will become a classic. It's been in production continuously since the end of 2006, 16 years, without any significant changes apart from some fuses and stuff but with the original 'tone'. I don't think any other Marshall tube amp can say the same. Amps like the 2203 had been discontinued and reissued but never that long in production.

Once they discontinue it, it'll be a classic for sure, if the reissue, modify / "improve" it, move it to production is Asia or bin it is something that time will tell.
 
santiall said:
Hey Pablo, congrats on the amp and thank you for the compliments :)

The original tubes where the Svetlanas with the =C= logo, yep, no longer made anymore. Quite good ones.

Speaker... I mainly used a 4x12 with G12T-75 in it. It was the 'standard' Marshall cab so it made sense to voice the amp with it. I did of course try the amp with the other options (V30 and Greenbacks) but the main one was the 1960 with G12T-75, I actually think the G12T-75 is a very good match for that amp, some people don't like them but it would probably be my choice. People like Satriani also ended selecting the G12T-75 for the original JVMs and also for his signature later on.

The combo story is quite simple. The TSL 2x12 combo had those speakers inside, we tried and we kept them. No other reason. What I don't know is why they had those speakers in the TSL to begin with although I guess it was to tailor a little it the sound of the open back.

The clean channel is my take on a Fender circuit, a bit tighter than the Fender if you overdrive it and with an EL34 power amp. The 30th Anniversary had a similar circuit although I always found it a bit 'dry', perhaps too clean, so I added more harmonics to the one in the JVM. Clean Red was the result of experimenting with the circuit, there were some extra tubes not being used and I think it can sound quite vintage if dialed properly. Many people don't experiment much with it, just crank the gain full in Red mode and expect a 5150 or something :D. To me it shines with the gain rather low, then using the tone controls to shape the distortion.

Well... somehow I believe the JVM will become a classic. It's been in production continuously since the end of 2006, 16 years, without any significant changes apart from some fuses and stuff but with the original 'tone'. I don't think any other Marshall tube amp can say the same. Amps like the 2203 had been discontinued and reissued but never that long in production.

Once they discontinue it, it'll be a classic for sure, if the reissue, modify / "improve" it, move it to production is Asia or bin it is something that time will tell.
Click to expand...
Hi Santiago,

Thank you so much for your reply. Very much appreciated and highly detailed.

It is really an honor to conect with you, the master mind behind a of a modern classic amp.

I wish for you all the best.


Pablo González Kettenhofen.
 
at the end both controls are in series so you won't be driving the power amp higher if the MV is higher for example. The power amp "sees" whatever signal you put into its input and delivers power based on that. If this amp had a post phase inverter volume you could drive harder the phase splitter with a higher channel volume but it is not the case with the JVM and any amp with pre-PA master.

I know many people out there think that they are driving the power amp mpre having the MV high but sorry, that's just not the case in the JVM or in any amp with similar design (pretty much all the multi-channel amps out there).

Regarding noise, I'd suggest to have the channel volumes as high as you can, then set the overal listenning volume with the MV. The tone difference will be suble if you choose to have lower CV and higher MV. The general rule for maximizing noise performance in any circuit is to have as much gain as early as possible, this is the reason why you should have as much signal as you can into your audio interface and so on.

The way it was designed was to set the Clean Green to whatever gain/tone you like and then set the rest ov CV to match. They should be around noon.

The Satriani version has some frequency shaping around the channel volumes so the amp gets darker the lower the channel volume is. The standard one is pretty much flat, the frequency variations are subtle when using different volume settings
 
santiall said:
at the end both controls are in series so you won't be driving the power amp higher if the MV is higher for example. The power amp "sees" whatever signal you put into its input and delivers power based on that. If this amp had a post phase inverter volume you could drive harder the phase splitter with a higher channel volume but it is not the case with the JVM and any amp with pre-PA master.

I know many people out there think that they are driving the power amp mpre having the MV high but sorry, that's just not the case in the JVM or in any amp with similar design (pretty much all the multi-channel amps out there).

Regarding noise, I'd suggest to have the channel volumes as high as you can, then set the overal listenning volume with the MV. The tone difference will be suble if you choose to have lower CV and higher MV. The general rule for maximizing noise performance in any circuit is to have as much gain as early as possible, this is the reason why you should have as much signal as you can into your audio interface and so on.

The way it was designed was to set the Clean Green to whatever gain/tone you like and then set the rest ov CV to match. They should be around noon.

The Satriani version has some frequency shaping around the channel volumes so the amp gets darker the lower the channel volume is. The standard one is pretty much flat, the frequency variations are subtle when using different volume settings
Click to expand...
This is very helpful information. Thank you so much for the detailed answer, Santiago!
 
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