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Hybrid amps...the best of all worlds?


Al Krow
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Cheers WoT. The R-400 is a hybrid right? In which case you're completely on topic! :)

But there must be some hot competition out there in terms of:
- pure valve amps
- other hybrids (what else is great out there?)
- excellent pre-amps when combined with a solid state to get us 90%+ of the way there, without needing a fork lift...and also without breaking the bank: EBS F mentioned a Kemper, but I've checked and they seem, by themselves, to be the cost of a great rig!

So I'm definitely looking forward to hearing further from the my fellow BCs on their thoughts...

Edited by Dad3353
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Cheers WoT. The R-400 is a hybrid right? In which case you're completely on topic! :)

But there must be some hot competition out there in terms of:
- pure valve amps
- other hybrids (what else is great out there?)
- excellent pre-amps when combined with a solid state to get us 90%+ of the way there, without needing a fork lift...and also without breaking the bank: EBS F mentioned a Kemper, but I've checked and they seem, by themselves, to be the cost of a great rig!

So I'm definitely looking forward to hearing further from the my fellow BCs on their thoughts...



The real answer here is that there is no "best".. We all want different things from our amps, and they're only part of the chain from fingers to speakers to room... Edited by Dad3353
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The walkabout has a 12ax7 in the gain stage and another one destined to drive the mosfets. Please do not expect I can give you detailed engineering data or explanations, but according to the Mesa people and the knowkedge available on other boards about the WA (mega thread on talkbass), it seems that the m-pulse technology was conceived this way to fill the behavioral gap between full tube and hybrid. I can testify they built something special with that proprietary circuit.



There are schematics available on the internet, nothing that special in there, it's a hybrid of tubes and cheap op amps in the preamp with a pretty standard solid state power amp.

Not saying it's not a nice amp (I've played one and enjoyed it) but there's no proprietary magic in there imo, it's just one of the better (albeit overpriced in the UK) traditional hybrid amps. Edited by Dad3353
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There are schematics available on the internet, nothing that special in there, it's a hybrid of tubes and cheap op amps in the preamp with a pretty standard solid state power amp.

Not saying it's not a nice amp (I've played one and enjoyed it) but there's no proprietary magic in there imo, it's just one of the better (albeit overpriced in the UK) traditional hybrid amps.

I think you may have hit the nail firmly on the head there. I have been working on an Ashdown MiBass 220


And it is a nicely designed pre-amp that is let down by using cheap opamps. The extra cost of decent ones is quite low, it would put the cost up by about £1.50. (TL072 if anyone is interested).

I suspected that the opamps used in the Mesa are no better. Edited by Dad3353
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My point was that many people attribute the "valve sound" to the power section. You may want to talk to passinwind about valve pre's (call them tubes though) his PW6 design was a full valve pre although all his recent designs (and the ones he uses ) are SS.



I guess I'm suggesting that there are varieties of pleasing and recognisably "valvey" colouration that come from particular preamp topologies (in addition to the effects observed from the power amp) that could make them well worth using even without a valve power amp. The preamp I put into the Dynacord is a simple 6sl7 circuit based on the front end of an Ampeg B15n, and when pushed a little it produces a kind of distortion that barely even sounds dirty, but has a flattering thickening/sweetening effect along with some compression. It's a sound I'm particularly enjoying, and quite different to what I hear from Fender-ish valve preamps. And since I can directly compare it with a clean solid state preamp into the same power amp, I can be fairly sure that that colour is coming from the preamp in this case. Edited by Dad3353
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6v6....never tought there is some magic in the Walkabout, but please consider that a certain circuit do sound a certain way because of the design as a whole, regardless of the single components. The vast majority of amps in the common commercial range if price are built with quite common quality components, but the design and interaction of the parts is what determines how it sounds.

Just t clarify once and for all, the WA was an example, I'm sure there are other awesome hybrids, like that handbox for example.

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I guess I'm suggesting that there are varieties of pleasing and recognisably "valvey" colouration that come from particular preamp topologies (in addition to the effects observed from the power amp) that could make them well worth using even without a valve power amp. The preamp I put into the Dynacord is a simple 6sl7 circuit based on the front end of an Ampeg B15n, and when pushed a little it produces a kind of distortion that barely even sounds dirty, but has a flattering thickening/sweetening effect along with some compression. It's a sound I'm particularly enjoying, and quite different to what I hear from Fender-ish valve preamps. And since I can directly compare it with a clean solid state preamp into the same power amp, I can be fairly sure that that colour is coming from the preamp in this case.

It is great that you can A/B them. What don't you like about the Fender Pre-amps? Or rather what is different? I plan to put a Class D amp in my HH alongside the Bipolar Class A/B power amp. I will have a have a switch (or two) so that I can change from one to the other. Sorry to go off topic.

Edited by Dad3353
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There are schematics available on the internet, nothing that special in there, it's a hybrid of tubes and cheap op amps in the preamp with a pretty standard solid state power amp.

Not saying it's not a nice amp (I've played one and enjoyed it) but there's no proprietary magic in there imo, it's just one of the better (albeit overpriced in the UK) traditional hybrid amps.



Maybe not magic, but the pre of the WA (and even more so the R-400 IMO) is fairly unique 'cos they're not starved plate. They're rich, dynamic and clear.

Edited by Dad3353
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It is great that you can A/B them. What don't you like about the Fender Pre-amps? Or rather what is different? I plan to put a Class D amp in my HH alongside the Bipolar Class A/B power amp. I will have a have a switch (or two) so that I can change from one to the other. Sorry to go off topic.



I like Fender type preamps too, they just have a different character going on from what I hear with a B15-esque 6sl7 preamp. Subjectively, my 6sl7 preamp has a nice thick, flattering quality (though not muddy) and isn't so edgy when pushed. I don't know if that's down to the difference between 12ax7 and 6sl7 valves, the Fender vs the James tone stack or whether it's the different approach to biasing - without taking the time to experiment, it could be any or all of those factors. It's a character that I liked immediately and don't hear in a lot of modern bass amps, though admittedly I haven't tried a lot outside of the mainstream stuff that you see everywhere. I do wonder whether some of the small-maker preamps and hybrid amps that get such enthusiastic reviews here and on Talkbass might also be going for that kind of sound. Edited by Dad3353
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FWIW, the R-400 has a Baxandall tone stack. It's unbelievably simple, but it works so well.



I need to mute your posts I think because I want an R400 more and more each time you say something about them! Edited by Dad3353
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Maybe not magic, but the pre of the WA (and even more so the R-400 IMO) is fairly unique 'cos they're not starved plate. They're rich, dynamic and clear.



Just curious: what is your tuning threshold (voltage and bias current) for considering a design to be "starved plate?" Edited by Dad3353
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Just curious: what is your tuning threshold (voltage and bias current) for considering a design to be "starved plate?"



I have no idea - I didn't build the amp. I have no reason to doubt the word of the chap who built it, though. 🙂 Edited by Dad3353
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I have no idea - I didn't build the amp. I have no reason to doubt the word of the chap who built it, though. 🙂



Then please ask him to elaborate here, and name names. I can think of dozens of tube bass preamp sections that use what I consider a perfectly adequate tuning for clean and clear, FWIW. Yel_wink.gif&key=3ab94d731b01d5c0e9221566d53c60d29307d50110116d217becbce9ad875649 Edited by Dad3353
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Then please ask him to elaborate here, and name names. I can think of dozens of tube bass preamp sections that use what I consider a perfectly adequate tuning for clean and clear, FWIW. Yel_wink.gif&key=3ab94d731b01d5c0e9221566d53c60d29307d50110116d217becbce9ad875649



He's not named anything - it's my own understanding that most tube pre's are starved plate. Is that not right?

As far as I know The Walkabout, MPULSE 600, Warwick Tubepath and the R400 are full voltage, and from memory I like the way they break up compared to, say, the SS Ampegs and Class D's I've owned previously.

I'm genuinely happy to be edumacated otherwise, though...? Edited by Dad3353
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Hey WoT if you are in contact with Leszek could you find out whether there is any possibility of combining a R-400 with his custom 412 cab and price up? If he can, I suspect he will have a serious rival to the Mesa WA Scout and I, for one, would be very interested indeed in taking one off his hands.

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He's not named anything - it's my own understanding that most tube pre's are starved plate. Is that not right?

As far as I know The Walkabout, MPULSE 600, Warwick Tubepath and the R400 are full voltage, and from memory I like the way they break up compared to, say, the SS Ampegs and Class D's I've owned previously.



I'm not under that impression at all, but am also eager to learn. So then let's start by defining "full voltage", please. That changes quite drastically by tube type, hence my request for specifics. I've seen very few genuine starved plate designs, but I have access to hundreds of schematics and a willingness to do some research on at least a few pieces if you can suggest some. Edited by Dad3353
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I'm not under that impression at all, but am also eager to learn. So then let's start by defining "full voltage", please. That changes quite drastically by tube type, hence my request for specifics. I've seen very few genuine starved plate designs, but I have access to hundreds of schematics and a willingness to do some research on at least a few pieces if you can suggest some.



I think that's probably a question for the chap who built the amp...? Edited by Dad3353
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Hey WoT if you are in contact with Leszek could you find out whether there is any possibility of combining a R-400 with his custom 412 cab and price up? If he can, I suspect he will have a serious rival to the Mesa WA Scout and I, for one, would be very interested indeed in taking one off his hands.



Yep, it sounds like a great combo (pun half-intended), Just drop him a mail at [email protected] - he's very helpful.

(Just to clear up any confusion from other posts - I'm not a representative of the company. I'm just a happy customer..!) Edited by Dad3353
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