SE 300B Integrated Amp: Help choose circuit design

[xenithon]

Hi All,

I am having a 300B SE integrated amp built, and the builder an myself were originally planning on using an Aikido circuit. I came across much reservation though due to the limite gain (as the Aikido was designed as a preamp) so we have explored other options. We discussed these in length this morning and have narrowed the choices down to the list below. I'd appreciate any feedback or recommendations on which to opt for.

1. 12AV7/12BH7A
- 12AV7 input tube, wired in parallel
- 12BH7A driver tube (not 100% certain how to wire this; could parallel both to yield a little extra gain, but at what cost?)

2. 12AV7/EL34
- 12AV7 input tube, wired either in parallel, as a mu follower, or SRPP
- EL34 driver tube, wired as a triode strapped pentode

3. Pentode Aikido (pentode aikido driver for 300b)
- we are not sure which tubes would be used here
- would a pentode (e.g., EL84) be used as input and a triode (12BH7A/ECC99) as driver tube?
- or visa versa: triode as input, pentode as driver (like option 2 but Aikido)?

If possible, please try limit suggestions/comments to the above three (to keep my indecisive nature in check)

With regards,
X

PS. I did have a thread earlier regarding OPT choice, but that decision has been taken so thought it better to start a new thread for this.

[xenithon]

Sorry, I almost forgot the one other option (amp builder just reminded me of it):

4. 12AV7/12BH7A (based on this design)
- 12AV7 as voltage amplifier
- 12BH7A in SRPP as driver

Cheers,
X

[xenithon]

Hi all,

Following some more discussion with various people, I have narrowed it down the following combinations

1. 12AV7/12BH7/300B
- both 12AV7 and 12BH7 would be wired in parallel
- I could also at some stage experiment with SRPP
Question: which one should be wired in SRPP - the 12AV7 input tube or the 12BH7 driver?
2. 12AV7/EL34/300B
- the EL34 would be wired as a triode strapped pentode
- I have seen this implemented in various ways such as here (which seems to use the full 12AT7) and here (which seems to only use 1/2 the 12AT7)
Questions:
- which of the above schematics would be better?
- can I use the 12AV7 in place of the 12AU7?
- would I require a CCS or can this be implemented without one?

Cheers,
X

[mhconley]

X -

Have you received any input on this thread? Have you built either of the two amps in option 2? I am considering building the first using the full 12AT7 and am looking for feedback on the schematic you linked...

Thanks,

Martin

[Tetrode]

Try a 2 stage amp with just the EL84 driving the 300B.

[nicoch58]

there are tre nice design of thorsten , two stage with pendode , lady D+
417a
310a we can use the svetlana copy
G3m

I think I will try g3m or 310a

[alexg]

Originally Posted by Tetrode

Try a 2 stage amp with just the EL84 driving the 300B.

Anybody done this?

[Bas Horneman]

Try a 2 stage amp with just the EL84 driving the 300B.

I have. I liked it. (EL84 in pentode). But you might not. That is the problem. It is best to build a few well known/well received 300B amps and listen to them in your system.

A little something about Herb Reichert's "Flesh and Blood":

Apparently if you want to build the "Flesh and Blood" you must build it exactly as specified. Not my own experience but something I got told by someone who has tinkered with a lot of 300B designs.

[Bas Horneman]

3. Pentode Aikido (pentode aikido driver for 300b)

I never tried that one. But since I used the 6N6P I've become curious. But I have many other things higher on the priority list at the moment.

[rock4016]

Originally Posted by xenithon

Hi All,

I am having a 300B SE integrated amp built, and the builder an myself were originally planning on using an Aikido circuit. I came across much reservation though due to the limite gain (as the Aikido was designed as a preamp) so we have explored other options. We discussed these in length this morning and have narrowed the choices down to the list below. I'd appreciate any feedback or recommendations on which to opt for.

The Aikido does have enough gain to drive the 300B. Options would include 6SL7/6SN7 or 12AX7/6CG7 and some others.