New SE With Triode Mode KT120/150

[JamesD]

Umm Dave Dove's amp used a 6BR7 wimpy pentode as front end of the Aikido... And the 300B had Schade feedback driven from the Aikido backend - which is all wrong and less optimsed than the RH amps - except, of course it isn't as the power valve is driven by Gm in the driver stage and the Aikido provides that and the virtual earth reference point...

[Nick]

That exactly what I was saying mark..a light load required but I still think its gain is still not right for modern amplifiers..

Then maybe as the guitar world does plug in a 6072a

[IslandPink]

1. Umm Dave Dove's amp used a 6BR7 wimpy pentode as front end of the Aikido...
2. And the 300B had Schade feedback driven from the Aikido backend -

1. I do remember that pentode version you were discussing, so that was the version at Owston ?
However I do remember having a conversation about how he preferred ECC83, when he was round here another time, not sure if that was before or after Owston and the pentode version.
2. Ah, I didn't know that, thanks !

[JamesD]

It was the 6BR7 at Eggfest I'll see if I can find my notes to check when the ECC83 was in the design...

For nostalgia here is the 6BR7 original circuit showing an EF86 that Dave was going to use before buying the 6BR7 - they are compatible for this design.

DD pentode aikido 300bxls ver 2.GIF (8.4 KiB) Viewed 3811 times

[steve s]

Looks an ok way to drive a 300b in my view
But again the ef86 is a pre amplifier valve., widely used as a 1st stage in low signal/voltage amplification.
In its favour I would think twice the current in that set up compared to ecc83.

Whenever I've used an ef86 to amplifiy a decent voltage I've been disappointed by the results compared to the valves normally use.

I found the ef86 bass light, I'd guess so I would say in that circuit the mid section would be exaggerated just slightly.. complementing the 300b mids ?
Nice.. possibly impressive..
Jono's 45 amp did the same trick as I remember. Another nice amp.

I still think Steve's amp, not needing a big voltage jump with lots of current drive, it's a different ball game to the 300b
But a nice side track..

[Paul Barker]

The VA doesn’t need power the cf does that duty.

The ACF 2 Nick adapted with more power drive and dc all the way sounds great. We drove the 833 with it at Owston. It’s pretty perfect. All the amplification and drive ever required. The VA is a single valve but rare a double ecc83 replaces that part of circuit.

[Paul Barker]

All I can find is the circuit



Oops, that’s not it!

[pre65]

How about this ? ACF2 circuit.

But I can't remember where I got the details from, I think Nick gave me a link.

[Paul Barker]

Thanks Phil

[Paul Barker]

Just in case you have any errors in copying Phil, I captured this off the web

[Paul Barker]

My school Moro was winsit persewerantia

Found J Ross Macdonald article. Fig 4 is our one. https://jrossmacdonald.com/jrm/wp-conte ... llower.pdf

[Paul Barker]

This is all because someone couldn’t use ECC83 but worth considering, to my ears it sounds “bloody marvellous”! Read the article it’s what the circuit is about which without you having to comprehend to the extent you could teach it, you can at least see the reason detre is in the circuit not the “valve rolling”.

[Cressy Snr]

Am currently trying out the 6N1P:


This has a similar amplification factor to the MH4 Steve is sending me. A bit lower actually but near enough to be able to assess the possibilities.

I must say it’s very, very good. Nice bass with great mids and an extended, sweet top end. The 6N1P is running 10mA at -2V bias and 165V at its anode. Nice ‘n simple... like me.
Hilarious how it’s dwarfed by the ‘120s

[JamesD]

Always liked the 6N1P - prefer it to the ECC88 any day of the week

But MH4 should be on a different level - really interesting to see what you find...

[Cressy Snr]

Always liked the 6N1P - prefer it to the ECC88 any day of the week

Aye, IME the ECC88 can sound a bit too hi-fi for my liking, and flat too; like an overstuffed speaker cabinet.
The 6N1P is a lot more musical and nuanced; at least it is in the above amp.

But MH4 should be on a different level - really interesting to see what you find...

Yes, the new amp will be a great project with our Ant’s cabinetry and Steve’s old Brit valves.
I’m looking forward to getting stuck into it.