Iridium Amp1, is it equivalent to a Marshall 8080 valve stat?

[PelliX]

Hi. Valvestate is a technology that uses a solid state power amp, but wired in a way it provides high impedance at the speaker jack, so it interacts with the speaker in a similar way as valve power amps do. The 8080 uses a 12AX7 / ECC83 driving the tone stack, but this is not what "valvestate" means. Just is an hybrid amp, with a valvestate tipe of power amp.

That's contradictary; the Valvestates (and I like them for what they are, no bashing here) simply have a part valve preamp, or a single valve preamp stage, rather. The output is just a plain transistor pair, so they do *not* interact with the speaker like a valve amp at all. The balance between the output valves, OT and speaker are what makes a valve output stage so "different" together with the way it can saturate.

Nano tube is quite different from a 12AX7 from what I understand.

Technology wise, yes. The results is intended to be similar and the saturation of that gain stage *could* on - paper work - similarly. I've tried a Nu-tube VOX amp, but wasn't impressed. I can't pinpoint that being down to the Nu-tube bit itself, though. I'm not convinced, but I'd say give that technology some time and it might just turn into something cool.

It is a an obsolete nonsense marketing term. Full stop.

Wrong, it was what Marshall called their amps with 'hybrid' preamps. VOX had another name for it that I forget right now, various others did the same thing.

The 12AX7 in those amps can be practically interchanged for another TL072 which will do the task of buffering the signal for the eq.

Depends on the circuit. I could hear the valve operating when pushed in my 8080. Obviously, if you're driving the transistors around that gain stage so hard they're clicking and fizzing it's not much good, but there was a sweet spot on my Valvestate that actually "did what it was supposed to do". Drive a TL072 to its limit and... yuck.

Plain marketing nonsense and rigorous wasting of 12AX7 tubes and therefore a waste of precious earthly resources.

Why, you could snag the valve and ditch the rest of the amp...

And there it is the same usage, your guitar signal hits couple of ic's that cascade into each other
and for extra "sizzle" they use diodes that clip the signal.

I never understood the desire for diode clipping *in the amp*, either. I still smirk at the JCM900 for that, though people swear by 'em. Maybe I'm not a good enough player to make it work for me.

Most distortion comes from solidstate devices,
not the valve in there, they just use it as an eq buffer, which can be done simply with another
ic.

Why would anyone use a valve as a buffer for the EQ in there? I mean, a "barely functional" gain stage would make more sense. Buffering is best done with an IC as you outline...

I dont know, because havent looked inside one
and never will because im not interested in this.

Ah, gotcha.

 

[Tatzmann]

Depends on the circuit. I could hear the valve operating when pushed in my 8080. Obviously, if you're driving the transistors around that gain stage so hard they're clicking and fizzing it's not much good, but there was a sweet spot on my Valvestate that actually "did what it was supposed to.

What was it that you heard when "the valve operated" or "did what it was supposed to do"?

Please tell me, i'm all ears. Maybe i can hear it too if you tell whats there to hear.

And if you happen to remember this one magical
setting, do you care to share it with me, i have an 8100 i would like to try it on.

 

[PelliX]

What was it that you heard when "the valve operated" or "did what it was supposed to do"?

In a nutshell, a decent crunch. I don't like solid state crunch.

Please tell me, i'm all ears. Maybe i can hear it too if you tell whats there to hear.

See above. Like the 'edge of breakup'. Probably driving the IC's to the point just before they start to ruin it all, but getting enough signal into the valve to make it do its job.

And if you happen to remember this one magical
setting, do you care to share it with me, i have an 8100 i would like to try it on.

Sorry, it's been years and I was on an old 8080, not an 8100. I believe the 8100 also only engages the valve on one of the two channels, correct?

 

[Tatzmann]

Thanks for the answers, i'm satisfied and don't
need any more details, says enough.

 

[PelliX]

Thanks for the answers, i'm satisfied and don't
need any more details, says enough.

Excellent.

I think your linebreak thing came back, though.

 

[Tatzmann]

Its not solidified yet, but i try hard not to prematurely hit the enter button every few
words. Is it a form of digital retardation?
Maybe i can ask my doctor for some of the good stuff?

(Didnt hit enter once for linebreaks in this post, yay!)

 

[saxon68]

I like Euge allot, very cool guy, we both had encounters with Michael Monroe band in the past and I am sort of in touch with Andy McCoy's band members now, all these nordic rockers are down to earth great artists...,

the Marshall Euge has lucked out with is a 1984 alike the one John Syke's had which he called the Bad Boy, I believe its from the same line in Sweden, they have a unique issue which is to the owner's benefit, two volume settings, with that out of the way and statements by Euge in his videos about using the BluGuitar only to avoid possible breakdowns and costs as its close to a stock JCM800 2003 sort of the way Mercuriall SPARK is but of course amp1 serves live purposes.

In the video I posted Euge says that the silver Amp1 modded by Thomas which is not public sounded even closer to the John Syke's 1984 Bad Boy batch, that high end sizzle giving it a rare growl,, well he also states that he has already finished working with Thomas to release an even closer replica of the bad boy 2203 in the next upcoming Amp1 model., but Thomas wants $2k so what's in it for those who already own a silver or Iridium can they buy this mod update to get a decent Marshall 2203 tone?

You don’t have to spend 2K to get “a decent Marshall tone”, it’s already in the iridium and Mercury. If you consider Euge’s “Bad Boy” amp to be the example of “decent Marshall sound”, well I dunno what to tell you. I’m pretty sure that if you’re over there, you can likely get one of those Swedish models for around that same cost.

He’s got 2 of them but only uses the one. This tells me that there are production or accidental after construction factors that make this one amp special.

Anyhow I’m not trying to be all fanboy, I just know what works for me. For “real” amps, I’m fine with the iridium, the SC20H (with the legendary tones hot mod 2 or Lynch mod) or Peavey VTM60, all with 4x12 cabs, and at full band volume. Loud, 2 guitar and banging drummer volume.

 

[Tatzmann]

As i did a little digging the company did some
statements about Amp1, because they got many requests about signalflow.

Instead of showing schematics they come forward with saying things like:

-the signalflow? is all analog
-the nanotube sits in the powersection and with its complementary analog circuit its not discernable
from "conventional" valvepowersections.

(Maybe someone who owns this product can test it against a 100w Superlead, to prove or disprove this statement)

Other points they say are about reverb, boost, 2nd master etc.

They show a blockdiagram which isnt revealing
anything but a crude signalflow, without showing
any parts, partnumbers etc.

If the preamp is all analog as they state ("analog signalflow")then it is stacking opamp into opamp and possibly diodes for extra clipping (boost?), and/or jfet input, mosfets is another possibility i guess.

You can read this on here, but its written in foreign and really doesnt say anything profundly anyways.

 

[tschrama]

The first Valvestate series did have a special poweramp that mixes voltage a current feedback to achieve a high output impedance. Both discrete and power opamps versions were made. This current feedback indeed achieves a speaker interaction that provides for a bass resonance and slightly scoped EQ typical for tube power amps.

 

[Tatzmann]

Might be a similar "complementary analog circuit" in this unit. A big old outputtransformer would look kind of funky ontop of it.

 

[Tatzmann]

The first Valvestate series did have a special poweramp that mixes voltage a current feedback to achieve a high output impedance. Both discrete and power opamps versions were made. This current feedback indeed achieves a speaker interaction that provides for a bass resonance and slightly scoped EQ typical for tube power amps.

But that doesn't have anything to do with
12AX7 driver for the eq in the 8100/8080?

Can you please elaborate on this a little?





useful link
http://www.valvewizard.co.uk/accf.html

 

[tschrama]

Sure, I love analyzing schematics:

Preamp:
True, the current feedback in the valvestate poweramps doesn't have anything to do with the 12AX7 driver for the eq in the 8100/8080. Just like the 12AX7 driver of the tonestack in a 2203 doesn't have anything to do with its poweramp feedback arangement.

I think the 8080/8100 is the highest regarded valvestate model, based on what I read on the net. It starts with an opamp tubescreamer stage with gain and tone preset to 12 oclcock (26dB gain). Nothing original there. Then another opamp gain stage (gain 40dB max at OD2 for a total of 66dB). The C31 , 47pF, is a key element. Some other similar preamp design (other valvestates, pedals and the JCM900 HGDR) have 100pF and that is too much pre-clipping high-end attenuation to get that marshall sound.

After the 2nd opamp gain stage there are clipping diodes limmitng the voltage swing to about - and + 1.8Volt. 66dB gain to 1.8Volt clipping is a tiny bit shy for my liking. 60dB into 0.6Volt (a single diode) is usually the maximum I ever need. This is equivalent to 70dB into 1.8Volt.

Then a tube gain stage folowwed by a source folower. There is feedback from the source-folower to the input grid of the gain stage (R95 220K into R68 22K) for a total gain of 20dB. IIRC the tube is fed from 150Volts (?) . No idea why the designers used this feedback arangement. It is a significant deviation from the traditional marshall tube preamps (plexi's, jcm800 2203 etc ) and does sound different from a 2203.

Another slighth diviation is the treble bleed capacitor C11. It ensures trble is attenuated even with the mid-pot maxed. No big deal, but I like to get rid of it, to ensure the tonestack to behave as I am used to.

But since input to the tube is limited to 1.8Vp, and the tube gain is set to 20dB , the tube can never really clip. The 8280 and JMP-1 midi preamp dont have this feedback can the tube can get overdriven. I have/had both the 8280 and jmp-1, the 8280 is definitly not as good sounding as the 8080/8100 or jmp-1.

After the timestack, the signal is attenuated (-21dB) for linear amplification by the next opamp; this one drives a mid-notch filter. I dont like tte notch filtering.

The cool thing is, you can mod the jcm900 HGDR into a JMP-1 or 8080/8100 preamp and it then sounds great!


Power amp:
The PA was really original for me. It starts with an inverting opamp stage. It has a local feedback loop, 34dB, about 105Hz high passed (!) and drives a symmetric cascode transistor pair (TR5 and 6) to shift the current drive to the higher voltage rails of the PA. The drains of the cascode-pair drive a symmetric pair a common-base transistors (TR 4 and 7) for extra voltage gain. The voltage developed at the drains drives the output Darlington transistors TR8 and 10 via a Vbe multiplier (Tr 9) to bias the output transistors.

The higher voltage PA part has a local feedback loop via R81 and R100 for a gain of about 12dB. It is DC coupled (!).

Global feedback is a mix of voltage feedback and current feedback from the output to the non-inverting input of the opamp. Current feedback comes from the current sense resistor R120 (0R33), then goes via R60 (470R) to be mixed with voltage feedback from R61 (33K). A second voltage Feedback path via R62 and R59 provide some extra low-frequency feedback but with added phase shift. I am not sure if this is an attempt to mimic the low-frequency phase shift of a output transformer, or if this is just a method to limit the gain at DC, to minimize DC-offset. I am guessing the first: an attempt to mimic the LF behavior of an output transformer.

The PA has a output impedance is about 14 Ohm at 1kHz. In a typical guitar cabinet rated for 8 Ohm, this amplifier voltage output will exhibit a 6dB resonance at about 80Hz, relative to a valley between 200-2kHz, and a gradual rise of about 6dB at 10kHz.

I have never seen such a power amp before or since... maybe all the brains were spent to the PA and what ever was left, was in charge of the preamp...



PS
The excelent website of Rod Elliot has an article about mixed mode feedback: https://www.sound-au.com/articles/current-drive.htm . That website is a true jewel of the net. A must read for anyone who like audio electronics.

 

[Tatzmann]

Thank you very much!

 

[yafal]

That's contradictary; the Valvestates (and I like them for what they are, no bashing here) simply have a part valve preamp, or a single valve preamp stage, rather. The output is just a plain transistor pair, so they do *not* interact with the speaker like a valve amp at all. The balance between the output valves, OT and speaker are what makes a valve output stage so "different" together with the way it can saturate.

Well, you have a point there, regarding the saturation of a valve power amp vs. a valvestate, which do not saturate well. BUT, A/B ing both without amp saturation, the valvestate sound and react pretty similar to the valve one, because the type of negative current feedback they used in the design. Of course, if saturated, they don't.
Best regards.

 

[paul-e-mann]

This is why I want a BluGuitar Amp1

 

[paul-e-mann]

 

[PelliX]

Well, you have a point there, regarding the saturation of a valve power amp vs. a valvestate, which do not saturate well. BUT, A/B ing both without amp saturation, the valvestate sound and react pretty similar to the valve one, because the type of negative current feedback they used in the design. Of course, if saturated, they don't.
Best regards.

I honestly never really noticed much of the output stage of my Valvestate. If I wouldn't know better, I'd have assumed it was pretty much any old run-of-the-mill transistor output stage, very linear, no surprises. I'd also be inclined to say my DSL is pretty much the same - wherever you put the volume, it's about the same - if you take the Presence and Resonance controls out of the equation, that is.

 

[PelliX]

This is why I want a BluGuitar Amp1

I wanna know how he gets the exact same stereo spread from both devices, while the JCM is very much mono...

 

[paul-e-mann]

I wanna know how he gets the exact same stereo spread from both devices, while the JCM is very much mono...

This guy does really good recording, I'm sure he records in stereo.

 

[PelliX]

This guy does really good recording, I'm sure he records in stereo.

Sure, it sounds great, but for comparison's sake, I'd keep it simpler.