Nicks Aikido 300b amp

richardcooper2k · Post by **richardcooper2k** » Thu Jul 05, 2007 11:34 pm

sometimes i think those are the type of differences that i find i like the best in the long haul, though i don't usually find them immeadiatly obvious. hope you've got one of those !

Darren · Post by **Darren** » Thu Jul 05, 2007 11:48 pm

Nick wrote:Well, I am currently using a 6em7 like valve as the first two stages, driving a 1:1 interstage into the 300b grid, I think thats a better sound to me. I still haven't got back to the sound I had before though, so maybe I was in a better frame of mind when listening then. Hard to say.

Interesting, I always wondered whether interstages would add their own signature.
Having tried using my PX4 output transformers as interstages to the 833s I was quite surprised how much better the resultant sound was over using cap coupling.
Most noticeable improvement was the total loss of hum, even less than the PX4 amp that was driving the 833s.
I've yet to figure out why, but if someone has any theories....?

simon · Post by **simon** » Fri Jul 06, 2007 9:10 am

Nick wrote:I am currently using a 6em7 like valve as the first two stages

Have you changed the 6N6Ps in the Aikido Nick? If so, what to?

Post by **Nick** » Fri Jul 06, 2007 9:52 am

I still have the aikido as a optional module as is the c3g, its about a 20min change

.

I am using a similar circuit to the 6EM7 one that Paul originally proposed, but using a 6GF7. The first stage is like the small triode of a 6DN7, and the second, like the large triode of a 6EM7. First stage, with unbipassed cathode resistor, directly coupled to second stage stood on about 5k of cathode resistor bipassed with a Wkz. Thats driving the AE 1:1 interstage, and then to the 300b grid.

andrew Ivimey · Post by **andrew Ivimey** » Fri Jul 06, 2007 10:43 am

That's interesting Nick, I know there is a fairly big family of these types of valves (e.g. 6EW7) and I am using 6FJ7 (decatron) in the latest push pull jobbie. I'd assumed 6FJ7 = 6DN7 but now I am wondering. I'll look up the spec. to compare and contrast.

- can't give 6EM7s away! or I'd be worried someone would snap up these marveloous little valves.

simon · Post by **simon** » Fri Jul 06, 2007 1:03 pm

Interesting Nick. Do you feel now that the Aikido isn't the best driver for the 300Bs?

Andrew, you know I'll take your 6EM7s off your hands

. Which reminds me, I should start a thread about the ECL82 spud amp.

andrew Ivimey · Post by **andrew Ivimey** » Fri Jul 06, 2007 1:13 pm

Hooray! avec plaisir Simon.

Give us your address and I'll send them to you. I was hoping, rather like that other chap (from whom I have not yet heard) that someone who doesn't do this sort of thing would have his/her imagination fired, like DTB.

Their loss eh!

Cressy Snr · Post by **Cressy Snr** » Fri Jul 06, 2007 1:27 pm

simon wrote:Which reminds me, I should start a thread about the ECL82 spud amp.

Definitely Simon

The more construction threads we get going on here the better. There seems to be a bit more of a constructive (forgive the pun) atmosphere on here than the WD forum at the moment.

Steve

simon · Post by **simon** » Fri Jul 06, 2007 2:07 pm

andrew Ivimey wrote:I was hoping, rather like that other chap (from whom I have not yet heard) that someone who doesn't do this sort of thing would have his/her imagination fired, like DTB.

Their loss eh!

Quite Andrew, which is why I was, and still am, very happy for someone else to have a go. Their loss indeed.

Steve,

Nail and head. I thought this was supposed to be a hobby for our enjoyment, not an opportunity to stick the boot in whenever the chance prevails itself. I watch the news to get my daily share of misery and confrontation. This is my escape from the real world and I'd like to keep it fun.

Besides, for real aggro my favourite football forum has all I could ever need...

Simon.

Andrew · Post by **Andrew** » Mon Jul 09, 2007 9:19 am

Nick wrote:Well, I am currently using a 6em7 like valve as the first two stages, driving a 1:1 interstage into the 300b grid, I think thats a better sound to me. I still haven't got back to the sound I had before though, so maybe I was in a better frame of mind when listening then. Hard to say.

I briefly thought about using the 6EM7 in a tx-coupled Aikido set up but then I realized the gain would be a bit low and anyway with the 6EM7 you'd DC couple it so it didn't seem such a good idea.

So I went back to designing a 6EM7 1 watter and thinking about a 5751 on the input instead of the 6072A.

cheers,

-- Andrew

Dave the bass · Post by **Dave the bass** » Tue Jul 10, 2007 2:05 pm

Andrew wrote: So I went back to designing a 6EM7 1 watter and thinking about a 5751 on the input instead of the 6072A.

cheers,

-- Andrew

Wotcha Gents,

Andrew, PM me your address and I'll post you those Sylvania NOS 5751's FOC. I posted over on 'tother forum too, thats where I saw your appeal.

TTFN

DTB

Andrew · Post by **Andrew** » Wed Jul 11, 2007 5:25 pm

Of course, an Aikido 5751's gain will be about the same as a 6EM7 Aikido but the 5751 would be self loaded rather than resistive loaded.

I think what you have, Nick, is a much better bet for the 6EM7 family.

And your not short on gain with the 6GF7 in this config, mu of 64 and 5-ish, something like that?

Given the 6GF7 first stage has enough gain have you considered trying the second triode as a cathode follower? But then there's shed loads of drive in the 6GF7 as a "grounded" cathode anyway. So, forget that.

Hmm, the more I talk through this, the more I see where Paul's coming from and what's so nice about this config. The penny drops as they say, sorry it took so long, yes, its got everything, drive, gain, uses a very linear valve, and is a fully dc/tx-coupled driver. The only downside I can see is the large-ish cathode bypass cap required, but then there's compromise in everything. Nice one all round Paul and Nick!

Nick, do you think the less forward sound is a result of further reduction in the odd harmonics in this config? If that's what you see/observe? I remember you saying the Aikido sound was less foward than the C3g and that was due to changes in the odd harmonics.

-- Andrew

Post by **Nick** » Wed Jul 11, 2007 6:22 pm

Nick, do you think the less forward sound is a result of further reduction in the odd harmonics in this config? If that's what you see/observe? I remember you saying the Aikido sound was less foward than the C3g and that was due to changes in the odd harmonics.

I don't know, I should run some more measurements. But (as I was saying to Paul last night), I th ink a lot is due to the use of the interstage, it may not measure as well, but it does convey a certain greator sense of reality. Less HiFi impressive at first hearing, but just more attractive after longer listening. Very hard to describe.

Andrew · Post by **Andrew** » Wed Jul 11, 2007 8:23 pm

I'm certainly very impressed with what my SJS interstage does.

I keep meaning to try the 6C45 again as there was something quite meaty about it, more just to compare with the Aikido than anything else as I never had them running 'side by side'.

So much to do, so little time.

-- Andrew

Post by **Nick** » Thu Jul 12, 2007 8:04 pm

Ok, I have been doing a bit of measuring.

This is 1W into 8R 1khz

Ad this is 0.1w into 8R 1kHz

I will see if I can find the equiv for the aikido and c3g driver stages

I am happy with the noise floor though.

audio-talk

Nicks Aikido 300b amp

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