I have found myself using more and more SS in my valve amps. I personally have no qualms about this.
Let's talk about this though, when is it really a step too far?
I have built a couple of amps along the lines of Shoog and others using CCS in the cathodes to force balance( and also class A)
Also made several with source followers to get some A2 or AB2 ala George and quite possibly many others. Sometimes at the expense of melting a grid, doh.
Tend lately to regulate all supplies using SS. Depletion mode fets are just so useful.
So when is it a hybrid?
Cheers Matt
Let's talk about this though, when is it really a step too far?
I have built a couple of amps along the lines of Shoog and others using CCS in the cathodes to force balance( and also class A)
Also made several with source followers to get some A2 or AB2 ala George and quite possibly many others. Sometimes at the expense of melting a grid, doh.
Tend lately to regulate all supplies using SS. Depletion mode fets are just so useful.
So when is it a hybrid?
Cheers Matt
JMO, when SS active devices are in the direct signal path, it's a hybrid.
Well selected MOSFETs as source followers are quite transparent. Therefore, there is no problem. We use tubes because they do all sorts of jobs better than "sand". The idea (IMO) is to get 1st rate performance using whatever technology fills the bill.
Well selected MOSFETs as source followers are quite transparent. Therefore, there is no problem. We use tubes because they do all sorts of jobs better than "sand". The idea (IMO) is to get 1st rate performance using whatever technology fills the bill.
Everyone has their own definition. I don't care what you call any particular circuit, as long as it works good. Does a mosfet follower in the signal path make the amp a hybrid? Does a CCS plate load make the amp a hybrid? I tend not to think so, but everyone is entitled to their own definition. When I first discussed these concepts about 10 years ago the reaction was mostly negative. 10 years later they have gained acceptance.
There was a challenge about a year ago to design the best TUBE guitar amp using less than $100 worth of parts. I asked whether a mosfet CCS or follower was acceptable. The originator of the challenge, and most participants, agreed that it was, but one very vocal participant disagreed. He claimed that ANY silicon ANYWHERE destroyed the sound by sucking the tone out of it! The discussion got ugly several times requiring moderator intervention. Obviously, some will never accept silicon in a tube amp, probably because they have never taken the time to make it work.
I would say an amp is hybrid when one or more stages is made of predominately solid state components. I don't consider a tube stage with solid state assistance hybrid, but it's OK by me if someone else does.
Excellent description......and yes it sounds better.
After some thought about which one of my designs are assisted, and which are hybrid, I would call the CCS loaded mosfet buffered designs assisted.
I have been experimenting with an output stage topology that uses a tube and a mosfet (or BJT) in a "darlington" like configuration. The circuit is just like a typical tube amp, SE or P-P using an OPT. The tube handles the voltage gain while the mosfet follower boosts the current. The transfer function (plate curves) are inherited from the tube, but the vertical "current" scale is in amps. The circuit is the one on the upper left. I am using it in a common "cathode" configuration (OPT connected to "plate"). To me this IS a hybrid.
By the way I have extracted over 200 watts from a pair of EL84's and a pair of big Fuji mosfets in P-P with a power toroid for an OPT. The plate resistance of the hybrid pair is about 10 ohms. This lets you squeeze decent performance from cheap OPT's.
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When it needs to be as a marketing gimmick.
Otherwise, SS gain stage + hollow state finals, or hollow state gain stages and SS finals would be a "hybrid" Considering the latter as a possibility for making a decent sounding MOSFET amp, and it would definitely work for those SiC power JFETs, as these like lotsavolts anyway.
Otherwise, SS assisted hollow state amp looks about right.
Some of my amps are not Hybrid. They are Solid State Assisted Tube Amps. Even when solid state devices are used in power stabilizers only. It sounds better.
Hmmm.
SSATA's ?
I've done some simplistic trials with ss CCS anode load in a standard tube preamp using the 6DJ8 . Sounds OK . But it took away the transient 'bite' that the resistor load produced. On paper ( or computer screen !) the CCS stage had better specs.
It could have been a poor implementation but that would mean that one needs to be very careful with mixing types.
It could have been a poor implementation but that would mean that one needs to be very careful with mixing types.
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Personally, I consider any amp that uses both SS and tubes anywhere in the circuit, to be a hybrid.
The question was "when is it a step too far?" - not sure I understand the question, but if you are implying that there's a limit beyond which something is bad then I don't see any such limit related to the use of both SS and tube components.
The question was "when is it a step too far?" - not sure I understand the question, but if you are implying that there's a limit beyond which something is bad then I don't see any such limit related to the use of both SS and tube components.
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Bigun; most usually Hybrid is an amp that combines distortions of tubes loaded on non-linear symmetric emitter followers that add also cross-over distortions. Such a nasty combination that had been called "The combination of the best of 2 worlds". After it become standard for "hybrid" name I hesitate to call my amps "Hybrid".
Yes, the "Bite" can be eaten by either R-C in coupling to it's grid, or R-C in cathode, or both.
Just to clarify that, there was no input coupling cap to the grid and no bypass cap on the cathode. Only the coupling cap from anode to the next stage which was a ss power amp ! I didn't investigate this extensively .........too many other things to get done !
Strictly speaking that would include diodes in the power supply.
The Tubelab TSE used a CCS load on the driver and a mosfet buffer to drive the grid of a DHT. The excellent transient dynamics are the amps strong point.
There are several effects in silicon devices that must be carefully balanced to avoid audible artifacts. All silicon devices exhibit VVC (voltage variable capacitance) effects. This is due to the depletion region in the reverse biased C-B junction changing width with applied voltage. It can also be caused by the modulation of the channel width or depth in MOS devices.
Hanging a capacitor that changes value with applied signal voltage across the plate load resistor can blunt the transient attacks. Devices need to be carefully chosen for constant capacitance across the intended voltage range. This generally rules out BJT's.
Interestingly enough, the same effect is present in a vacuum tube due to modulation of the space charge cloud width by the grid bias (and signal) voltage. The effect is measurable but the Q is very low due to poor conductivity in the cloud.
These VVC effects are being blamed for PIM (phase intermodulation Distortion) by the anti - silicon crowd. PIM is very difficult to measure unless it is extremely bad....bad enough to show up on a scope as jitter.
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Yes, for some people, 'hybrid' got a bad name already. But then for some people any SS is bad, and for some PP is bad, and for some low power SE is no good. Can't please all the people all the time it seems.
Yes it would, although I recognize it's not common usage to call an amplifier with silicon diodes a hybrid it is for me still a hybrid - and when you read all the banter about how tube rectifiers affect the sound of an amplifier it's clear that at least for those people, SS rectifiers would make it a hybrid.
It's all semantics - naturally - but for me the point is crossed when significant amplification or signal processing duties are handled by both SS and tubes.
Rectifiers ans CCS loads, IMO, are not really making things "hybrid" (except in the true and real meaning of that term), and there's even a fine line if follower's or other practically transparent stages should fit the bill. But that's only my opinion and this is largely a semantical issue with highly subjective answers.
But I agree, it's good marketing for those who find it appealing.
Rectifiers ans CCS loads, IMO, are not really making things "hybrid" (except in the true and real meaning of that term), and there's even a fine line if follower's or other practically transparent stages should fit the bill. But that's only my opinion and this is largely a semantical issue with highly subjective answers.
But I agree, it's good marketing for those who find it appealing.
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Well, I'm hybridizing little by little. First one to go was the tube rectifier. Sounds just as good or better with silicon diodes. I recently built a purist power supply (tube rectifier plus choke plus poly caps) and it was not good enough for hifi (lack of punch) but excellent for a guitar amp. Just keep an open mind and try different things and then choose the parts that give you the best results for the application at hand. Some people reject things without even trying them, well not some, a lot of people do that. Then there are the crazy folks, of the nazi variety, these will not attempt to reason their dislikes.
I would like to know more about transistors - to design regulators and such. Alas, I only know about tubes so for me tubes are the only choice - can't design an hybrid amp even if my life depended on it. I have mosfets and plenty of transistors laying around. I just need to learn to design an output stage. Dammit. It's like having money that I can't spend - a little frustrating.
I would like to know more about transistors - to design regulators and such. Alas, I only know about tubes so for me tubes are the only choice - can't design an hybrid amp even if my life depended on it. I have mosfets and plenty of transistors laying around. I just need to learn to design an output stage. Dammit. It's like having money that I can't spend - a little frustrating.
Now what if my amp is hated by some who hate SE, by some who hate tubes, and by some who hate SS devices?
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