Indeed G2 tweaks and bias adjustment

[leo]

Mar 23, 2010 23:32:02 GMT PinkFloyd said:

Nope, to my eyes (and ears) the parts are the real deal (what do you think Leo?) it's just that pot that looks a bit iffy to my eyes.

Mike.

I'd say they are genuine too, Its possible all these parts are not ROHS compliant, as you know most places like Farnell , RS etc sold off none ROHS compliant parts very cheap because of the stupid green regulations. The parts are good, just not lead free
This is just a guess, I do know those Dale resistors are leaded parts

[MaN227]

mike
thanks for the reply on that .... ;D whew thank goodness

@frans
got me to thinking about different color for leds lol I think I'd most like amber or orange , something that actually 'goes with' the tube glow or way off like my newest xmas lights a deep purple-ish blue, much akin to Black Lights. I can see my self enjoying it in times whilst partaking in the goodness of God's Green Earth ;D

the first thing I am going to mod lol i use that term loosely I am turning the lid 180 deg put etching in back, tired of looking at it and it distracts from its lighted beauty as well . ;D

matter of fact that piece of plexi won't be there at all once a few things are sorted. ;D neither will his wimpy lil pal on the bottom lol

[metalicblue]

Hi everyone,
I'm new to this forum but was reading about the Bravo - Indeed for a while and decided to order the G2.
Today I just received my G2 from Peter and I will let it cook for couple days till my others tubes arrive (6922 JJ-E88CC and PHILIPS NOS-6922-JAN) The ampl. arrived with the upper panel broken but Peter was so nice to offer to send me another one.
Has someone tryed rolling some 12 tubes in the ampl? They are so much cheaper than the 6 tubes? any suggestions about what I could order ( www.tubedepot.com/12at7.html).
Thanks

[MaN227]

Mar 30, 2010 6:15:55 GMT metalicblue said:

Hi everyone,
I'm new to this forum but was reading about the Bravo - Indeed for a while and decided to order the G2.
Today I just received my G2 from Peter and I will let it cook for couple days till my others tubes arrive (6922 JJ-E88CC and PHILIPS NOS-6922-JAN) The ampl. arrived with the upper panel broken but Peter was so nice to offer to send me another one.
Has someone tryed rolling some 12 tubes in the ampl? They are so much cheaper than the 6 tubes? any suggestions about what I could order ( www.tubedepot.com/12at7.html).
Thanks

welcome metalicblue hope your enjoy your stay here in the Grotto.

soz I can't help ya on the 12's as I've not heard them, but I'm sure one of the fellaz in the know will be along and share thoughts on this issue.

in the meantime, I think the stock electro harmonix 6922 is rather nice actually . not sure so i prob should keep my mouth shut but ;D it may be generally thought that the 6 series tubes are better than the 12 series.
I'm interested in the replies as well

Peace

[Deleted]

Mar 30, 2010 8:55:13 GMT MaN227 said:

Mar 30, 2010 6:15:55 GMT metalicblue said:

Hi everyone,
I'm new to this forum but was reading about the Bravo - Indeed for a while and decided to order the G2.
Today I just received my G2 from Peter and I will let it cook for couple days till my others tubes arrive (6922 JJ-E88CC and PHILIPS NOS-6922-JAN) The ampl. arrived with the upper panel broken but Peter was so nice to offer to send me another one.
Has someone tryed rolling some 12 tubes in the ampl? They are so much cheaper than the 6 tubes? any suggestions about what I could order ( www.tubedepot.com/12at7.html).
Thanks

welcome metalicblue hope your enjoy your stay here in the Grotto.

soz I can't help ya on the 12's as I've not heard them, but I'm sure one of the fellaz in the know will be along and share thoughts on this issue.

in the meantime, I think the stock electro harmonix 6922 is rather nice actually . not sure so i prob should keep my mouth shut but ;D it may be generally thought that the 6 series tubes are better than the 12 series.
I'm interested in the replies as well

Peace

Me too!
Dave.

[PinkFloyd]

The quick way to replace the IRF630 with IRF510

1: Remove the 1000uF cap. Get a pair of pliers and turn the rod that connects both heatsinks together back and forth a couple of times (this loosens the screw that secures the MOSFET to the heatsink) Remove the screw with a small "flat blade" screwdriver (easier to get in than a philips)



2: Desolder the 630 Mosfet using a desolder pump then remove it:



3: Slot in the IRF510, screw it onto the heatsink then solder it (soldering iron temp. high). All you have to do now is replace the 1000uF cap..... repeat for the other side.



Took me 15 minutes to do both MOSFETS.

[Deleted]

Mike,
A cap head allen screw replacement, instead of the Phillips to secure the heat sink, would make it a lot easier to access in the future, if need be.

[covenant]

Just a thought on the IRF510 replacement. If the G2 is intended for use with the modified HD681 cans would you think that the IRF510 should not be fitted? The HD681's have a quite
sharp upper end frequency response and I wonder if this mod would defeat the benefit of Fran's filter.

[leo]

IRF510's don't boost the high's, the IRF630 roll them off

[covenant]

Thanks Leo-hows the cat?

[leo]

Apr 6, 2010 12:14:32 GMT covenant said:

Thanks Leo-hows the cat?

Of course some may prefer the rolled off high's with the IRF630, it may be an ideal cure for a source or cans which is top end heavy.

The cats doing ok now ta.

[PinkFloyd]

Apr 6, 2010 15:00:00 GMT leo said:

Apr 6, 2010 12:14:32 GMT covenant said:

Thanks Leo-hows the cat?

Of course some may prefer the rolled off high's with the IRF630, it may be an ideal cure for a source or cans which is top end heavy.

The cats doing ok now ta.

Leo.... no need to be "polite"...... what do you REALLY think of the G2 amp?

Warts and all, your HONEST appraisal is required.

Mike.

[mitroche]

Hi all,

I have recently registered on the forum but have been reading it for a long time. Thanks a lot for the very useful information I have been able to find through the forum.

I decided to buy the G2, got it last week and find it does quite well. I am not particularly disturbed by crosstalk because it seems to appear at a louder level than the one I am usually listening. On the other hand my major objection goes to the high’s which are rolled off, as most of you noticed.

I will try to change IRF630 for IRF510 which seems to bring a radical improvement. Did someone measure frequency response with the IRF510?

As far as I remember, one of you had talked about carrying out a tube comparative for the G2. Would swapping the 6922 EH with an ECC88 (or others) make a significant improvement?

Thanks

[Deleted]

IRF630 + LM317 (stock comp) = 10kHz @ -0.5dB (20 kHz = -1.8 dB, 30kHz @ -3dB )
IRL530 (IRF 510 not measured) + LM317A (= higher grade LM317) = 30kHz @ -0.5 dB (65kHz @ -3dB)
IRL530 will improve freq range AND dynamic range (headroom), LM317's will be running a little hotter and the glowing voltage (and thus the bias voltage) will remain more stable at higher output levels.
Crosstalk and distortion will be less too with IRL530 instead of IRF510.

NOTE: If you use IRF530(N) the frequency range will be extended to about 15kHz (-0.5 dB) i.e. only slightly less roll-off then with the IRF630

(actual measurements done on Ian's modded Bravo (G1) but specs will be similar with G2 as all active components are the same)

The Qgs is mostly responsible for the highs roll-off (not the input capacitance as is stated elsewhere) because it is in sourcefollower mode.
the Qgs (gate-to-source charge) of IRF510 is 1.6 times smaller than IRL530 so freq. range with IRF510 would probably extend to 40kHz. (-0.5 dB)
You won't have the other benefits of the IRL530 over IRF510 and freq. range of IRL530 is already extended more than enough IMO.

the Qgs of IRF630 is 2.6 times higher then IRL530 and 4.3times higher then IRF510 b.t.w. for those that like figures.

[mitroche]

Thanks, Solderdude, for this very precise answer. I will opt for the IRF530 that seems to be the best solution.

[leo]

Apr 6, 2010 23:40:00 GMT PinkFloyd said:

Apr 6, 2010 15:00:00 GMT leo said:

Of course some may prefer the rolled off high's with the IRF630, it may be an ideal cure for a source or cans which is top end heavy.

The cats doing ok now ta.

Leo.... no need to be "polite"...... what do you REALLY think of the G2 amp?

Warts and all, your HONEST appraisal is required.

Mike.

Not really being polite, I understand some people might like the rolled off high's and Saccharin signature ? for me I still much prefer it after swapping the Mosfets, it still has that sugary signature to my ears but I must admit I find it fun to listen to. I don't think its THE best sound I've heard but certainly NOT the worse (by a long way)
It also looks cute

I still feel changing the Mosfet to one with lower capacitance is one of the main things everybody should try

BTW, I mainly used IRF510 because its what I had to hand, will also try the 530 at some stage

[Deleted]

My G2 runs a bit cooler now!!

View of parts for heat sink assembly.



Assembly under way using thermal paste between all mating surfaces.




630 mosfets changed in favour of 510`s







Its staggering how much heat is being displaced by this heat sink assembly, it still runs hot but at least there is almost twice the surface area to displace it. No effect on SQ at all(apart from improvement gain from the 510 mosfets) and i am happy with the way it performs and looks.

Next job new feet and pillars, more on that when i get the time, as production has started on outstanding orders for rings and end caps.

[MaN227]

well I'm not even going to say what you know I'm going to say anway lol or should that be ask? ;D

I will just say WOW too sweet heliharris

I can't wait to see the posts and such too curious what the final comes out to be like, wondering if its anything like I see in my head ;D

[Will]

Mick, that looks fantastic!

To use a phrase I saw somewhere else, it looks like something you'd use to kill a Dalek!!

Top Stuff!

[oink1]

Nice job Mick

[covenant]

My mouth dropped open when I saw those photos. Definitely Dr Who-ish. Do those coils go up and down?

[clausdk]

Mick
Looks good..
I like the way it looks like an aeroplane motor from before the Jetengine..

[Deleted]

MickLooks good..I like the way it looks like an aeroplane motor from before the Jetengine..

Same principle Claus, good enough for VW Beetles and Porsche 993`s, works well on the G2 as well.

[Deleted]

Hi Mick,
Lovely work. Can I ask a question?
Would it not be a more effective cooler if you put some holes in the bottom and/or around the bottom of the VW cylinders such that the inside of the cylinders acted as a chimney and drew cooling air in at the bottom and out at the top.
You may be then able to add a cool coloured smoke generator and make entertaining smoke patterns (or pretend you're electing another Pope ).
Just a thought - I used to be a chimney sweep in a previous life, probably ;D .
Dave.

[Deleted]

Would it not be a more effective cooler if you put some holes in the bottom and/or around the bottom of the VW cylinders such that the inside of the cylinders acted as a chimney and drew cooling air in at the bottom and out at the top.

Very good point Dave, will do just that next week, i will put 4 radial holes 2nd fin up from the bottom into the cylinder, nice one thanks.