Anyone else tried an opamp as a driver?

[Miniwatt]

L.S.

Since I found out my SE EL84 amp could be driven by my preamp I got rid of the driver AND the coupling capacitor. There's no way back..
I read an article by Satoru Kobayashi who designed a tube amp using a OPA 445 PA as driver and phase splitter. Even though it's blasphemy in the tube section I'm really intrigued by this idea. Especially because there's no need for a coupling capacitor! Such amps are quite rare and I've never heard one, has anyone of you?

[aardvarkash10]

nope - but I like the idea...

[analog_sa]

Originally Posted by Miniwatt

Even though it's blasphemy in the tube section

Just ask a moderator to move it to solid state and all will be forgiven.

[Miniwatt]

Originally Posted by analog_sa

Just ask a moderator to move it to solid state and all will be forgiven.

I did a search and the tube section seems the most appropriate

[ErikdeBest]

Electra print has two schematics (and the needed iron) for a class A2 amplifier (PP and SE).

Electra-Print.com Push-Pull A2 6A3/300B

A couple of months/years ago there was some discussion around the LME49811 and LME49830 IC's: opamps that can be fed from +100V/-100V and therefore produce about 60V RMS supplying some mA of current. Never seen a tube amplifier with one of these though.

http://www.national.com/ds/LM/LME49811.pdf
LME49830 - Mono High Fidelity 200 Volt MOSFET Power Amplifier Input Stage with Mute

Erik

[Globulator]

Originally Posted by Miniwatt

L.S.

Since I found out my SE EL84 amp could be driven by my preamp I got rid of the driver AND the coupling capacitor. There's no way back..
I read an article by Satoru Kobayashi who designed a tube amp using a OPA 445 PA as driver and phase splitter. Even though it's blasphemy in the tube section I'm really intrigued by this idea. Especially because there's no need for a coupling capacitor! Such amps are quite rare and I've never heard one, has anyone of you?

Haven't tried this as I prefer integrated amps, especially when the whole amp has only three stages to start with .
Then you avoid a whole bunch of stuff and cables, boxes etc!

[tubelab.com]

Electra print has two schematics (and the needed iron) for a class A2 amplifier (PP and SE).

Jack at Electra Print told me that using a mosfet to drive a DHT into A2 was a stupid idea. I did it anyway and it works great. Now he is pushing the idea of using a chip amp through a custom Electra Print transformer to drive DHT's. I haven't tried it yet, but there was at least one thread here where someone did it without an EP transformer.

A couple of months/years ago there was some discussion around the LME49811 and LME49830 IC's: opamps that can be fed from +100V/-100V and therefore produce about 60V RMS supplying some mA of current. Never seen a tube amplifier with one of these though.

I have seen a magazine article somewhere (Glass Audio / Audio Xpress?) that used one of these chips to drive power tubes (KT88's maybe). It was at least a year ago.

I haven't tried an opamp driver yet, but I have made opamp/tube CCS's. I also used opamps and a microcontroller for auto bias circuits, and a dsPIC chip to create a class H tube amp.

As far as I'm concerned, if it uses mostly tubes in the signal path, it is a tube amp. Sometimes some silicon in supporting roles just makes sense.

[807tubenut]

Originally Posted by tubelab.com

Jack at Electra Print told me that using a mosfet to drive a DHT into A2 was a stupid idea.

Funny how that works...right?

[tubelab.com]

Funny how that works...right?

Especially when you have something to sell.

I respect Jack. He is a talkative person with strong opinions. He told me that PowerDrive was a stupid idea, but had no problems selling me the OPT's for the first prototype of what is now the Tubelab SE. That is still the best sounding amp that I have, all 2 WPC of it.

I called back to find out about OPT's for my 845SE, but they were far beyond my price range. We discussed PowerDrive again and it was still stupid despite the fact that it works and sounds great. I found some cheap OPT's on Ebay and built that one too. It is also a great sounding amp that makes 40 WPC, but dumps almost 500 watts of heat into the room so I don't use it much.

[807tubenut]

To true!