[Sarchi]

Quote:

Originally Posted by fran /img/forum/go_quote.gif Just waiting for the dreaded hum to raise its head though....

I've been testing the Aikido on 90dB monitors and my 96dB coaxials, there is no hum - nothing. I have a very faint buzz that I've pinned on the magnet wire signal leads, when I tap them the buzz gets slightly amplified. So I'm pretty sure replacing these with shielded wire will yield dead silence.

Congrats on the build! And thanks again Fran for spotting my B+.

 

[Zigis]

BTW, it drained my 1.3ah sla's in 2-3 hours.

Most of current "eat" heaters. Try to conect heaters to PS, unregulated or even AC, and B+ to your SLA.

Ather option - in tubecad is few 24V PS schematics specialy for this Aikido.

Zigis.

 

[Sarchi]

I think I'll just watch ebay for a decent looking linear regulated psu.
Maybe something like this?

http://www.alliedelec.com/Search/Pro...D9580545FE17F#

 

[fran]

I don't know how long the bay link will last but heres the one I bought:

http://cgi.ebay.ie/ws/eBayISAPI.dll?...MEWN:IT&ih=007

Works perfectly, and output voltage is adjustable - this is very handy so that you can adjust the load voltage when you have everything hooked up. I also use a 7805 regulator to step down the voltage for the relay board in mine. This one thing does it all.

BTW, I'm hooked upto 240V but when I measured the current draw I get about .3A or thereabouts. If my memory is right, that means .6A at 110V

Fran

Fran

 

[Sarchi]

OK...I won this one;
http://cgi.ebay.com/ws/eBayISAPI.dll...m=120165141793

It's linear, whatever that means. I'll give it a shot. I could always stick with the batteries, but want to make sure my psu is half decent. I paid $100 for the four Valvo ECC86's, so I'd like them to last a while.

 

[dBel84]

Hey Sarchi, a little jealous of those Valvo's

. Nah , I have Bugle Boys which I am very happy with. But I did get to thinking about possible options for your line stage. Have you considered adding a headphone jack as lordearl had mentioned previously?

Quote:

Originally Posted by lordearl /img/forum/go_quote.gif I don't know if you saw it, but Broskie did post a schematic for a 6GM8 headphone amp here: http://www.tubecad.com/2006/06/blog0067.htm It uses the BUF634 to drive headphones and apparently runs on the same power supply as the original design.

The BUF634 option uses feedback on the buffer and thus is not optimal to enable a simple DPDT switch on the output between amp and headphone out but AMB's JISBOS would do nicely here.

Only problem here is that you are already going to be pushing that power supply you just bought ( 4 heaters @ 330mA = 1.32A ! ) , also it needs a dual supply so that may just complicate things more than you need or want. Just a thought really, I always seem to try and complicate builds and end up not using half of the "versatility" I so desperately needed

..dB

edit : I should have scrolled down the page on Tubecad - JB has outlined a discrete version and its implementation. The JISBOS would merely be easier as an ad on with the pcb's that are being prepared (dual supply ? vs single ??)

 

[Sarchi]

Quote:

Originally Posted by dBel84 /img/forum/go_quote.gif Only problem here is that you are already going to be pushing that power supply you just bought ( 4 heaters @ 330mA = 1.32A ! ) ,

Ummm. So I misread the current demands for the circuit?

"..although we do need much voltage, the heaters add a heavy current burden on the power supply. The heater string requires 330mA and the four tubes require a total of 8mA, for a grand total of 338mA or (rounding up) 350mA. So, 0.35A against 24V equals 8.4W of dissipation."


I think "total" means all four tubes, no? If it were drawing 1.32A my sla batteries wouldn't have lasted more than 60 minutes. But they were good for a few hrs.

 

[dBel84]

series series, must remember series

, 6.3V 330mA heater requirements , if parallel - 6.3V 1.32A, however in series, you are spot on. ~24V @330mA.

and that leaves plenty of headroom to add JB's discrete buffer

..dB

 

[fran]

Usually there are a number of solder tags on the transformer - you jumper some of these and apply AC at others depending on your local AC mains voltage. Often they also have 4 output terminals. you'll have DC+24V, DC- and then S1 and S2 - these are a sensing circuit ie if you absolutely needed exactly 24V at the other end of a long run of cable, you could use these to "self adjust" the voltage at the PSU to give you 24V at the other end.

As I said above, I'm using about .3A in total

Fran

 

[Sarchi]

Quote:

Originally Posted by dBel84 /img/forum/go_quote.gif series series, must remember series , 6.3V 330mA heater requirements , if parallel - 6.3V 1.32A, however in series, you are spot on. ~24V @330mA. and that leaves plenty of headroom to add JB's discrete buffer ..dB

Ok...whew. At least I got one thing right.

As for 'phones, I have to admit I'm not much of a headphile yet. I joined HF when I was looking for a portable setup, and that's as far as I've gotten so far.

 

[fran]

Well I got mine hooked up this evening - wow I'm thrilled with it, very good sound!

the obligatory pics:






I was using that case/relay board/stepped pot as a passive pre upto now and sound was bloody good. But its better now. My only issue is that I get a pop as I turn the attenuator but I should be able to sort that one out fairly handy.

Fran

 

[Sarchi]

Wow, fran...that's impressive.

 

[Sarchi]

hey fran....
I was hoping to get some further impressions on the Aikido from you, you're using it as a headphone amp right? I'm now thinking about converting mine to headphone duty.

My questions are:

- did you do it just as per Broskie's blog0067 post with the BUF634's? what heatsinks did you use? anything special for the extra caps/resistors?
- can you post a close-up pic of your layout, showing the IC's? (I'm a wee bit nervous, I've never worked with these beasts before)
- how well does it drive your AKG's? I'm pretty set on getting a pair of K701's for my first real high-end cans.

Thanks a lot,
Noam

 

[lordearl]

Heya Sarchi - I'm in the process of collecting parts for the BUF634 & using it with my AKG 701s...let me know how you go!

 

[Sarchi]

Will do lordearl.

So...as I'm planning out this Aikido HA retrofit, I have a general question: would there be audible improvment going to neutrik/xlr connectors for my 'phones? I realize this will still be unbalanced, just wondering what the common wisdom on this might be. The idea appeals to me; but I'm not sure that it's worth the loss of versatility.