Dx hybrid amplifier will be produced soon

[Bigun]

I do have a hybrid in mind for the TGM labs, but it is a different topology and progress will be some months away. I don't think DX will mind at all to see progress with your schematic !

The dc offset will drift as the tube warms / ages so a servo might well be the better approach.

Perhaps in your schematic you can place caps across R4 and R7. The idea being to adjust their ratio so that you can null out the B+ noise across the gate-source of the FET ?

Yes, I remember my 3A5 thread. Rod's idea is an old one, from a chap called Taylor, although it was used to make a Follower. But I also remember that it turns the load-line for the triode vertical and this is not how triodes are usually operated so I am quite curious about the 'sound'.

 

[still4given]

I am listening, right now:

Beach Boys - song talk about the 205 engine

https://www.youtube.com/watch?v=BcyGcmJTAdA

regards,

Carlos

Hey Carlos, you inspired me to look on youtube.

Now you have to picture a group of aspiring Rock Stars, huddling in my small bedroom around my RCA console stereo as I put on my new Lee Michaels album. The organ solo kicks in and I crank it to 10! I'm getting goose bumps thinking about it.

If you don't have a tube amp to play it through, don't crank it to 10.😱 SS distortion just won't do. 😎

https://www.youtube.com/watch?v=Nq-ZmjUYEqs

Blessings, Terry

 

[destroyer X]

Nice!.... very nice.

Thank you Terry.

regards,

Carlos

 

[padamiecki]

Well, I am now understanding that a DX Corp. amplifier is expected to meet some stiff requirements:

low measured distortion, no triple outputs but only double EF (tubes like to drive light loads which favours triple outputs), good PSRR of course, good stability and gain matching between channels, high damping factor for bass response and no pesky dc-offset issues.

All this favours use of global negative feedback and dc-coupling throughout. In short, the familiar DX topology. It doesn't appear suited to a hybrid.

Carlos suggested why put tubes into DX topology, use for LTP and VAS. Well this ain't easy since tubes come in only one flavour, n-type.

I thought I would post an idea of how to do this.

I use tubes for LTP and VAS. connect the output of the LTP to the VAS using a technique invented by a man called Taylor, it's known for use in the Taylor Follower. It requires a pnp device.

I'll attach what I came up with. First the schematic, then the Spice file (change .txt to .asc before running it).

Hi Bigun
what is the way of controlling the offset, R9?
tube as input device and vas too = no memory distortion😉

 

[Bigun]

Usual way with LTP - adjust tail current (I2).

 

[padamiecki]

Hi
in last Broskie's blog I found this idea for hybrid amp, just wanted to share: http://www.tubecad.com/2014/08/15/FET-Triode-MOSFET Hybrid Amplifier Large.png

 

[Bigun]

Looks like a hybrid of the Lender VAS.

 

[MiiB]

The hybrids i have built, all seem to suffer from a weak base, i contribute that to the capacitor-coupling of the OPS section, normally i don't mind capacitors in the signal-path, but normally i try to place them in a voltage driven section.

 

[Bigun]

With a large enough capacitor this shouldn't be an issue but I suspect other factors are important for good bass. I have heard the tightest most powerful bass from amplifiers that have high feedback factors. I'm not convinced this is because of damping factor, I suspect it's because the higher feedback is compensating for weakness in the OPS - or maybe these are one and the same.

 

[gaetan8888]

Hello

Any updates or listening tests of the DX hybrid amp ?

Thank

Bye

Gaetan

 

[Bigun]

I'm afraid progress has been rather slooooooooooooooooooooooooooooooooooooow