Indeed G2 tweaks and bias adjustment

[MaN227]

thanks for the reply above Frans. the only thing I wish is that you could dumb it down a bit for me the dummie as it makes my head spin all the technical stuff and trying to piece it all together. I had to read it 3 times.

[lecky]

I've just got a G2 a couple of days ago. Sounded better than my Bravo in which I put a 10,000uf 50v input cap and some better coupling caps too. I've got the big Nichicon cap on the G2 now and it perhaps sounds a bit better - perhaps. The crosstalk seems a bit worse than on the Bravo, and I've some IRL530s on the way which hopefully might help with that as well as extending the treble.

Anyway I'm very happy with the G2 over the Bravo. Thanks to the contributers of this thread for all the useful information.

I look forward to reading about more mods as they develop...

[Deleted]

Just tinkered with my G2, as per Mikes first post.

The IRF510s were fitted first, great result, loads more HF info coming through.

After that was the coupling and bypass caps, a discernible addition of attack.

Lastly, although I want the under-tube LED I didn't like the blue in this case, didn't think it matched the look. So I went green, the vol knob has changed too, again for preference of looks.

EDIT = For the bias, with the 6H23P valve and to my ears, 12.5v per side sounded best.

Still don't like the this with the K701 though. However, with the SL 662B it's belting out a decent, entertaining tune.

Yertiz,

[lecky]

I've fitted a pair of IRL530s on my G2 and it makes a fantastic difference opening up the treble and it does improve the crosstalk problem, but the crosstalk is still a lot more than I'd like, still audible in one channel at modest listening volume when there is no input on that channel.

I wonder if there are other measures that can be used to tackle that remaining crosstalk?

[Deleted]

there is !

Check out the Bravo / Indeed Headphone amplifiers thread page 43
No more crosstalk and no more distortion.

When using the IRL 530 or IRL510 and screwing up the bias to 14 Volts the point where the crosstalk becoms horrible will be moved considerably.
Worth a try.
There will always be crosstalk though unless you do the mods on the thread described above.

[lecky]

Thanks for the notes on the other thread - I can adequately put together what I can see, but am much less confident working from schematics. Yes, I know I ought to learn... But I think I'd be more comfortable waiting till someone hopefully posts some photos of how it goes together before giving it a go...

I've played with maximizing the voltage, and indeed it does help a little.

Thanks for sharing all your work on this, it's appreciated!

[leo]

Anybody tried a cathode bypass cap in these amps yet?

[Deleted]

I'm game but clueless!

How would you implement that? (for dummies answer please)

[leo]

May 9, 2010 16:57:56 GMT @cjarchez said:

I'm game but clueless!

How would you implement that? (for dummies answer please)

In most valve amps I've seen they have a cap across the cathode resistor for the bias, the Indeed amps uses a trimmer pot instead of a fixed resistor.
Basically try fitting a cap across each one of those trimmer pots, neg end of cap goes to pot pin which goes to ground.
Not sure of best value to try , don't think its too critical to try out, say about 220uf, more or less shouldn't matter, the voltage is under 1volt so something low as possible could be tried.because its the bias it maybe worth using low ESR and leakage types though if possible, I've seen Oscon used a lot on the cathode bypasses but I guess anything should be ok to try, somebody else also recommended this over on headfi

The bias pots may need adjusting a bit after fitting the caps so its worth checking the bias before and after

If I can find a pic of the bottom of the pcb I'll edit it to make it easier, no idea how well it'll work adding these caps yet though because I've not tried it, shouldn't do any harm though and can easily be reversed

[Deleted]

If I can find a pic of the bottom of the pcb I'll edit it to make it easier, no idea how well it'll work adding these caps yet though because I've not tried it, shouldn't do any harm though and can easily be reversed

like Mikes one?

[leo]

I've just tried it here using 470uf 10v panny FM's, I'll post a pic in a mo

Quite odd because that low level distortion I used to have with this amp seems to have gone sounds a little bright but these caps are brand new, they need some running in, the voltage measured across the caps is 500mV

Bias voltage is 16.5v both sides and voltage on output before output coupling caps is 12.5v

[leo]

I had to fit some pillars on the bottom pcb to the bottom plate because of adding the caps on the bottom

Make sure the neg end of the cap go's to the trimmer pin which goes to the ground and NOT to the pin which isn't going anywhere

This mod is very simple and easily reversible if you don't like it or think it offers no benefit
I think cap quality matters here tbh, I'm going to let the 470uf FM's run in for a while and see how it goes, an oscon should be nice here, maybe around 100uf , I just stuck in what I had knocking about

[PinkFloyd]

100uF is the general "standard" for cathode bypass caps Leo and, yes, low impedance types are excellent for this purpose. Can you get the bottom plate back on with the caps fitted or are you going to have to fit longer standoffs?

[PinkFloyd]

PS, I have a barrelload of 100uF OSCONS kicking about somewhere, I'll send you a few over if you PM me your details.

[leo]

Bottom plate wouldn't go on as is so I just added four of those pillars/spacers I scrounged off another project , their about 10mm long

For those without pillars/spacers it maybe possible to add additional nuts onto the screws for the bottom plate making more space and fit a 6.3v cap that would fit better

I still think theres less low level distortion on this one with the caps added, I'll remove the caps later just to be sure

[PinkFloyd]

Have you tried the G2 as a preamp yet Leo? I haven't but imagine it wouldn't be up to much...... I've tried the X-CAn V8P as a preamp and it's actually pretty darned good

By the way Leo, I have a spare X-CAN V2 (stock) which I am going to send to you (you can keep it) I'd like you to play about with it and see if you can extract any more out of it.... I will include one of my V2 kits..... are you up for that or too busy?

Mike.

[leo]

I've not tried the G2 as a pre-amp yet tbh Mike but can give it a go just out of interest.

Thats good of you ta regarding the V2, wouldn't mind having a play with one, I can send it back anytime too.
I'm busy during the week but normally have weekends mainly sunday's free

[Deleted]

I've popped on some 10v 100uf (of no particular quality) for cathode bypass, they were taken from a parts horse so shouldn't need any forming.

Voices, for me these are much better, possibly a little more tone in the bass area as well.

I found one extra nut plus a couple of washers for good measure did the trick for spacing the base plate.





Cheers Leo, t'was worthwhile methinks.

[Deleted]

May 9, 2010 20:03:36 GMT PinkFloyd said:

PS, I have a barrelload of 100uF OSCONS kicking about somewhere, I'll send you a few over if you PM me your details.

Have you got a couple spare i could have please Mike.


Thanks, Mick.

[leo]

Nice one cjarchez, glad it worked out ok .

We could rip the thing to bits and do a lot of mods/alterations but this defeats the object of this amp, it would be easier to just build something from fresh, its better to do simple mods everybody can try imo and easily remove if they don't like the results




(Edited, put wrong name)

[Deleted]

Nice one Mick, glad it worked out ok .

Haven`t tried them yet leo, hoping Mike will have a couple for me to install.

[leo]

Sorry Mick, it should have said cjarchez

[PinkFloyd]

May 10, 2010 13:29:38 GMT @heliharris said:

May 9, 2010 20:03:36 GMT PinkFloyd said:

PS, I have a barrelload of 100uF OSCONS kicking about somewhere, I'll send you a few over if you PM me your details.

Have you got a couple spare i could have please Mike.


Thanks, Mick.

Mick, yes.... sorry this is the first I have seen your post. Please PM me your details and I'll get a couple in the post pronto...... I have been so busy, it's hard to keep track of things PLUS I am going blind.... got an eye test next week so, hopefully, I'll be able to see again soon.

Mike.

[Deleted]

Any ideas why my iPod has broken after connecting to the RCA on my G2, worked fine when connected to 3.5 socket on front of Amp.

Its making broken noises on both channels,( tried it on a couple of Amps) but the rest of iPod seems to function normally.

And yes i had switched over the input switch to RCA.

Any recommendations for a decent iPod repair service, would be appreciated.

[clausdk]

May 12, 2010 20:01:19 GMT @heliharris said:

Any ideas why my iPod has broken after connecting to the RCA on my G2, worked fine when connected to 3.5 socket on front of Amp.

Its making broken noises on both channels,( tried it on a couple of Amps) but the rest of iPod seems to function normally.

And yes i had switched over the input switch to RCA.

Any recommendations for a decent iPod repair service, would be appreciated.

Have you tried another cable ??

My best advice would be to enjoy your Cowon