Indeed G2 tweaks and bias adjustment

[lynxo323]

quick question. sorry if I missed it in previous threads.

how does the circuit work to get the 6V to the heater?

looking at the schematic, it seems to be coming off the LM317.
that only drops 1.5V. so is the heater's current also going through the LM317?

since I no longer have a on/off switch, I should just tie the relay power back to the 24V and go back to a longer delay time to avoid thumps(?)

thanks!

[Deleted]

Sorry for not seeing your other questions.

> Is 6V rating for cathode caps suffice?
YES

>can I get away with using this heatsink for the LM317?
Yes, much better the original one, temp will be lower with this one.

>can I stick with stock heatsinks for IRL510?
Yes.

> how does the circuit work to get the 6V to the heater?
> looking at the schematic, it seems to be coming off the LM317.
> that only drops 1.5V. so is the heater's current also going through the LM317?

Yes the heater current + the current through both fat resistors flows through the MOSFET and the LM317's of both channels where they combine.
This, the combining part of these 2 currents, and a too low voltage drop over the LM317's brings about the crosstalk distortion.

The heater current is determined by the LM317's bias resistors.
heater current = current LM317(L channel) + current LM317 (right channel) - current through both 68Ohm resistors (so 34 Ohm)
LM317 current you can calculate by 1.25V/Rbias.

> since I no longer have a on/off switch, I should just tie the relay power back to the 24V and go back to a longer delay time to avoid thumps(?)
I would replace it with a new switch to get the relay circuit going again.
If you don't mind the on/off pop you must leave the relay circuit un-powered, otherwise there will be no sound.

[lynxo323]

Hi,

I got this 6dj8 hpa pcb off ebay. circuit looks very similiar to the G2.

from your experience should I try the stock circuit/stock values
or use the pcb for another G2?

I'm not even sure what the K310 fet is, cannot locate it in mouser.

thank you.

[lynxo323]

Yes the heater current + the current through both fat resistors flows through the MOSFET and the LM317's of both channels where they combine.
This, the combining part of these 2 currents, and a too low voltage drop over the LM317's brings about the crosstalk distortion.

The heater current is determined by the LM317's bias resistors.
heater current = current LM317(L channel) + current LM317 (right channel) - current through both 68Ohm resistors (so 34 Ohm)
LM317 current you can calculate by 1.25V/Rbias.

ahh, makes sense now. I thought the LM317 CCS was only for the IRL.

I've thought about trying your switching circuit for the heater but I cannot locate the traco part here in the US. mouser and digikey are my main sources.


thx!

[Deleted]

I have 2 switching regs left (around 8 Euro I believe) ordered some extra.
Hope to receive them within 2 days..

The amp above is very similar.
The anode CCS is made with a FET instead of a transistor.
The output resistor = 10 Ohms instead of 30 (G2) or 47 (older versions) or 68 (Rabbit's and yours)
They 'solved' the crosstalk by putting a large cap over the filament (this could be left out).
It also has an input coupling cap could be left out too.
The input resistance is also a lot higher.
Lower ohmic inputs are less prone for picking up stray noises.

If you ordered a bare PCB check if the pinning of an IRL510, 520 or 530 is similar to the pinning on the PCB then use that one.

[lynxo323]

If you ordered a bare PCB check if the pinning of an IRL510, 520 or 530 is similar to the pinning on the PCB then use that one.

will do, I plan to use the IRL510 since I bought an extra pair :-)

do I need to change any resistor values when dropping in the IRL510 onto this pcb?

thank you.

[Deleted]

Don't need to change resistors.
If you don't want the LED, just leave it, the resistor and cap out.

[lynxo323]

Don't need to change resistors.
If you don't want the LED, just leave it, the resistor and cap out.

please clarify. remove R106,C104, D1?

how would I know what voltage drop is needed for D1?
I'm assuming R105/R106 and D1 also sets LM317 bias(?)

thx

[Deleted]

Sorry I was a bit hasty on that one.

If you don't want the LED: remove R106,C104, D1

Only R105//R106 set the bias (15//13=6.96 Ohms) with 1.25V reference voltage of the LM317 this gives you a current of 180mA per channel so both channels will give a glowing current of 358mA. the tube is specified for 365 mA and is close enough !
If you are going to use a 300mA tube use 15 and 18 Ohm for R105 and R106 (2*153mA = 306mA) or a single resistor of 8.2Ohms (305 mA)

In this schematic the LED doesn't play an important job like in the other amps where it is part of the CCS for the anode current.
Here it is just a tiny extra load (2 mA) parallel to heaters.
I recommend fitting a 470uF cap over the 100 Ohm cathode resistor.

[Deleted]

Jul 28, 2010 20:29:34 GMT lynxo323 said:

Hi Solderdude,

can I get away with using this heatsink for the LM317?

www.aavidthermalloy.com/cgi-bin/stdisp.pl?Pnum=581202b02500g

can I stick with stock heatsinks for IRL510?

I understand it will get very hot. I would like to avoid mounting
parts off board. I understand parts will not last as long, which is fine.

Thanks

Hi, lynxo323

I am very much interested to know about your experience, and/or problems in mounting the LM317s to the TO-220 heatsinks. On the drawings I noticed that while the width and the distance of the LM317 mounting hole and the bottom of the TO-220 is OK, the total height of the heatsink is 50.8mm. Did you have to cut or drill the upper plastic plate, or did you just leave it out all together?

Any information about the above will be most appreciated.

All the Best!
imagemaker

[Deleted]

You can also 'lengthen' the studs and make the top plate higher.
When you leave the plate off there is always a risk of things falling on the PCB (headphone plugs for instance) and ruining your day.

The TSR-1-2465 will arrive around wednesday as will some parts (Wima) for the veil lifter.

[Deleted]

Aug 5, 2010 20:29:43 GMT @solderdude said:

You can also 'lengthen' the studs and make the top plate higher.
When you leave the plate off there is always a risk of things falling on the PCB (headphone plugs for instance) and ruining your day.

The TSR-1-2465 will arrive around wednesday as will some parts (Wima) for the veil lifter.

Thanks, soderdude!

I will order a bunch of 55mm or so studs to raise the plate higher! Why didn't I think of that? I look forward to receiving the items you mention. Do you think you will have an extra TSR-1-2465, for a total of two? I would also like to modify my other Indeed amp (the 6922EH one) for reduced crosstalk. PM me when you can.

All the Best!
imagemaker

[Deleted]

I ordered 3 TSR and have one left in stock but this one has been soldered once (still good though) so have 4 in total in a few days.

[cure]

hello

i just purchased the bravo v2 tube amplifier (which has yet to arrive.)
being a total noob in the tube world, i wanted to ask you guys one quick question:

it says that the compatible tubes for the bravo v2 are 6N10/ECC82, does this mean these are
the only viable tube replacements for the bravo? will it take any 12AU7? say siemens, GE, mullard, telefunken? i mean, tubes will fit into the bravo v2 as long as it's 12AU7?
i've seen alot of 12AU7 being sold on the net, too many variants. i don't have an idea which one would fit the bravo v2.
there's the 12AU7/6189, 12AU7/ECC82, 5814A, E80CC / 6085 (12AU7 compatible), etc....

and what do you mean by 'matched pairs'?

i was thinking of buying tubes so when the bravo arrives, i'll be able to do some tube rolling and test which one suits me best.

again, sorry for these ignoramus questions.

3hrdasfzq2xof8nrgi5a

[lynxo323]

Aug 5, 2010 20:16:53 GMT @solderdude said:

Sorry I was a bit hasty on that one.

If you don't want the LED: remove R106,C104, D1

Only R105//R106 set the bias (15//13=6.96 Ohms) with 1.25V reference voltage of the LM317 this gives you a current of 180mA per channel so both channels will give a glowing current of 358mA. the tube is specified for 365 mA and is close enough !
If you are going to use a 300mA tube use 15 and 18 Ohm for R105 and R106 (2*153mA = 306mA) or a single resistor of 8.2Ohms (305 mA)

In this schematic the LED doesn't play an important job like in the other amps where it is part of the CCS for the anode current.
Here it is just a tiny extra load (2 mA) parallel to heaters.
I recommend fitting a 470uF cap over the 100 Ohm cathode resistor.

Thanks! I will skip the LED.

[lynxo323]

Aug 5, 2010 20:23:51 GMT Imagemaker18 said:

Jul 28, 2010 20:29:34 GMT lynxo323 said:

Hi Solderdude,

can I get away with using this heatsink for the LM317?

www.aavidthermalloy.com/cgi-bin/stdisp.pl?Pnum=581202b02500g

can I stick with stock heatsinks for IRL510?

I understand it will get very hot. I would like to avoid mounting
parts off board. I understand parts will not last as long, which is fine.

Thanks

Hi, lynxo323

I am very much interested to know about your experience, and/or problems in mounting the LM317s to the TO-220 heatsinks. On the drawings I noticed that while the width and the distance of the LM317 mounting hole and the bottom of the TO-220 is OK, the total height of the heatsink is 50.8mm. Did you have to cut or drill the upper plastic plate, or did you just leave it out all together?

Any information about the above will be most appreciated.

All the Best!
imagemaker

Hi,

I decided to use 4 of these:

www.aavidthermalloy.com/cgi-bin/stdisp.pl?Pnum=531202b02500g

previous one would not work. I did not want to mount heatsinks off board so the 531202b02500G works for my purpose.

I pulled the 4 stock heat sinks and replaced them with the new ones. problem is the mounting pins have a larger diameter
so had to drill slight bigger holes. other issue is nothing to solder
to so used epoxy to hold down the heat sinks.

I put the IRL510 in place of the IRF510. for the LM317's,
I mounted them to the rear heatsinks and ran wires to the bottom
of the pcb.

so each LM317/IRL has it's own heatsink. I used 2" standoffs
to raise the top plate.

not the best solution but works for me :-)

[geetarman49]

greetz solderdude,

i would like to take 2 of those tsr if they are stil available --- paypal ok? probably only need 1, but i've been experiencing some clumsiness lately. btw, many thnx to u & the crew for all the work in improving this bargain basement gem .

imagemaker: where are u ordering the higher studs from? & do u have a link or reference/model # for the correct size/threading? i plan to raise the 'ceiling' for fitting taller caps and xtend the 'basement' for fitting 50K Noble pot.

my g2 is fitted with the eh6922 & i can't help but concur with some remarks previously made about it sounding 'rubbery'. my collection of 6dj8 are off to be cryo'd so in the meantime i have just a tele pcc88 and cv5358 to experiment with. are the '12' series of tubes worthwhile? better, worse, or just different? i don't need any more gain... way more than enough for my ultrasones and grado ... but i think i just bought a k701 & i have no idea if that's going to fit into the mix or not. comments, conclusions or just bashin' all welcomed here

<why can't i add smilies?>
don

[Deleted]

Aug 5, 2010 20:57:22 GMT @solderdude said:

I ordered 3 TSR and have one left in stock but this one has been soldered once (still good though) so have 4 in total in a few days.

Hi again, solderdude

Thanks for letting me know about the TSRs. I will be happy with two of these, and since the one that has been soldered, but still OK, I wouldn't mind if you include it in the lot.

All the Best!
imagemaker

[Deleted]

Hi again, lynxo323

Thanks for the information! I have ordered 10 of these heat sinks for the LM317s on the 5 amps that I have modified - one Indeed G2, one Indeed 6922EH, and three Bravos.

All the Best!
imagemaker

[Deleted]

Aug 5, 2010 22:53:49 GMT geetarman49 said:

greetz solderdude,

imagemaker: where are u ordering the higher studs from? & do u have a link or reference/model # for the correct size/threading? i plan to raise the 'ceiling' for fitting taller caps and xtend the 'basement' for fitting 50K Noble pot.

my g2 is fitted with the eh6922 & i can't help but concur with some remarks previously made about it sounding 'rubbery'. my collection of 6dj8 are off to be cryo'd so in the meantime i have just a tele pcc88 and cv5358 to experiment with. are the '12' series of tubes worthwhile? better, worse, or just different? i don't need any more gain... way more than enough for my ultrasones and grado ... but i think i just bought a k701 & i have no idea if that's going to fit into the mix or not. comments, conclusions or just bashin' all welcomed here

<why can't i add smilies?>
don

Hello, Don

I tried to find 55mm studs to replace the 30mm stock ones, but to no avail, so I settled for additional 30mm studs, which I can screw on the stock ones, thus raise the top plate up to a total of 60mm. Here is the link:

www.mouser.com/Search/ProductDetail.aspx?R=R30-3003002virtualkey57420000virtualkey855-R30-3003002

I hope this helps.

And, yes. I too agree about the 6922EH. I have a couple of them sitting around, and never liked them.

In the 5 amps that I have modified (2 Indeeds and 3 Bravos) I use both ECC82 and ECC88 Telefunkens -- they simply sound best to my ears, and I have about 30 pretty good tubes sitting around for rolling purposes, however none of the others measure up to the Telefunkens. A couple of Siemens tubes that I have come close. IMHO the old German craftsmanship is unmistakable here.

Best Regards,
imagemaker

[lynxo323]

Aug 6, 2010 0:56:01 GMT Imagemaker18 said:

Hi again, lynxo323

Thanks for the information! I have ordered 10 of these heat sinks for the LM317s on the 5 amps that I have modified - one Indeed G2, one Indeed 6922EH, and three Bravos.

All the Best!
imagemaker

not the best pics but you can see how they are mounted.

if you have the proper hand tools, you might try pulling
the heatsink mounting pins out and tapping them with a 6-32, I think 4-40 is too small. that way you can bolt it down vs. glue.

there room for most of the pins for a large hole on the pcb except the one on the right, it has pcb traces very close to the mounting hole so becareful with that one.

best wishes.

[geetarman49]

Aug 6, 2010 1:19:57 GMT Imagemaker18 said:

I tried to find 55mm studs to replace the 30mm stock ones, but to no avail, so I settled for additional 30mm studs, which I can screw on the stock ones, thus raise the top plate up to a total of 60mm. Here is the link:

www.mouser.com/Search/ProductDetail.aspx?R=R30-3003002virtualkey57420000virtualkey855-R30-3003002

I hope this helps.

And, yes. I too agree about the 6922EH. I have a couple of them sitting around, and never liked them.

In the 5 amps that I have modified (2 Indeeds and 3 Bravos) I use both ECC82 and ECC88 Telefunkens -- they simply sound best to my ears, and I have about 30 pretty good tubes sitting around for rolling purposes, however none of the others measure up to the Telefunkens. A couple of Siemens tubes that I have come close. IMHO the old German craftsmanship is unmistakable here.

Best Regards,
imagemaker

Thnx for the link, imagemaker. i'm hoping to get lucky on some 12au7/12ax7s and compare them against pcc88 (which i found to be my favorite on the bravo, but haven't had a chance to set it up on the g2). surprisingly, over the past few days i now get the sensation of diminished bass on my g2 ... with ultrasone hfi780 and eh6922 tube javascript:add("%20:("). my indeed should be well broken in by now (> 100 hr).

btw, did u incorporate linear psu for any of your indeed mods? if u did, was it a worthwhile upgrade considering its cost and performance relative to the stock psu. indeed (pun intended) by the time one factors in the cost of all these upgrades/mods i wonder whether or not it might simply be better to acquire a neco or a fournier?

don

[Deleted]

Aug 6, 2010 7:46:51 GMT geetarman49 said:

Aug 6, 2010 1:19:57 GMT Imagemaker18 said:

I tried to find 55mm studs to replace the 30mm stock ones, but to no avail, so I settled for additional 30mm studs, which I can screw on the stock ones, thus raise the top plate up to a total of 60mm. Here is the link:

www.mouser.com/Search/ProductDetail.aspx?R=R30-3003002virtualkey57420000virtualkey855-R30-3003002

I hope this helps.

And, yes. I too agree about the 6922EH. I have a couple of them sitting around, and never liked them.

In the 5 amps that I have modified (2 Indeeds and 3 Bravos) I use both ECC82 and ECC88 Telefunkens -- they simply sound best to my ears, and I have about 30 pretty good tubes sitting around for rolling purposes, however none of the others measure up to the Telefunkens. A couple of Siemens tubes that I have come close. IMHO the old German craftsmanship is unmistakable here.

Best Regards,
imagemaker

Thnx for the link, imagemaker. i'm hoping to get lucky on some 12au7/12ax7s and compare them against pcc88 (which i found to be my favorite on the bravo, but haven't had a chance to set it up on the g2). surprisingly, over the past few days i now get the sensation of diminished bass on my g2 ... with ultrasone hfi780 and eh6922 tube javascript:add("%20:("). my indeed should be well broken in by now (> 100 hr).

btw, did u incorporate linear psu for any of your indeed mods? if u did, was it a worthwhile upgrade considering its cost and performance relative to the stock psu. indeed (pun intended) by the time one factors in the cost of all these upgrades/mods i wonder whether or not it might simply be better to acquire a neco or a fournier?

don

Hi again, Don

Since I am using 10000uF power caps in paralel with 160uF 300V Flash Caps (the latter suggested by solderdude for greater transient response), the AC adapters that came with the amps proved inadequate because of the lower impedance caused by the huge caps, and the amps would periodically cut out , especially the G2, which uses double the amount of current that the others do. I solved this with two 24V6A DC regulated switching power supplies from a Hong Kong seller on eBay (they are indeed very good -- extremely quiet). Since I never use more than one amp at a time, they do fine for the 5 HP tube amps that I have.

And, I agree -- if one adds up all the costs of parts for upgrades on the Bravos and Indeeds, it can amount to some money that can be used to purchase some highly reputed ready-made amp, but to me, modding these cheap amps is worthwhile for the fun of tinkering, and being able to achieve the SQ of the higher end more expensive ready-made units.

And, this forum is a great fountain of information, a source of knowledge from which I am learning a lot, especially from people like Solderdude, Mike (Pink Floyd), and others like them, who are willing to freely, and generously share their expertise!

I can not express opinion on Neco or Fournier, for I am not familiar with them.

All the Best!
imagemaker

[geetarman49]

imagemaker: many thnx <grrr... i keep trying to add these smilies but opera is not playing>

don

[lynxo323]

Is there a huge difference in sound quality when swapping out tubes?

I just swapped out the stock 6N23 for a Jan Sylvania 6DJ8 and I really cannot hear the difference. both were biased at 13.5V after an hour.

this is with most of the mods done and the IRL510's.