Poor Man's Tube Gain Make Up Stage

[mitsos]

From brief looking online, seems the 6cg7 is pin compatible with the 6n1p and 6n6p russian tubes... I think I'd be in for 1-2.

But if I may make a small recommendation, could you leave a bit more breathing room for those caps? 

 

[ruffrecords]

From brief looking online, seems the 6cg7 is pin compatible with the 6n1p and 6n6p russian tubes... I think I'd be in for 1-2.

But if I may make a small recommendation, could you leave a bit more breathing room for those caps? 

Are you concerned about heat from the tube?

Cheers

Ian

 

[Joechris]

Just worried about turning one channel side upside down. Could make wireing and connections a bit confusing..?
j

 

[ruffrecords]

Just worried about turning one channel side upside down. Could make wireing and connections a bit confusing..?
j

They can both be the same way up but that means the output of one channel will be near the input of the other which could be a crosstalk issue. An alternative would be to re-route one half so it is a mirror image of the other rather than upside down. That way they would be the same way up but both outputs would still be in the middle. Do you think that would be better?

Cheers

Ian

 

[Joechris]

I still think they should be the same, not even mirrored. Looks like there will be half an inch between first out and second input, so I dont think there should be any crosstalk issues.
There is also space on the pcb to move the Pout Pin points a little futher down to make even more distance.

 

[ruffrecords]

I still think they should be the same, not even mirrored. Looks like there will be half an inch between first out and second input, so I dont think there should be any crosstalk issues.
There is also space on the pcb to move the Pout Pin points a little futher down to make even more distance.

OK, I'll make them identical but I'll also move VR2, its two associated resistors and Pin and Pout down next to VR1. I'll have to move the 220uF up to make room but that should be OK. Watch this space.

Cheers

Ian

Edit: something like this?

 

[mitsos]

Are you concerned about heat from the tube?

I was, but then I saw that the tubes are flipped the other way...  :`

carry on...

 

[Joechris]

That looks swell Ian. What about some extra holes for different brand of caps? For 4,7 uF I guess there is not many options. Is that a Wima 37.5mm you have in mind there?

 

[mitsos]

speaking of holes, how about two more mounting holes in the center and a v-score down the middle, allowing them to break apart for single channel use?

 

[michal_k]

speaking of holes, how about two more mounting holes in the center and a v-score down the middle, allowing them to break apart for single channel use?

+1 !

 

[ruffrecords]

I'll look at making provision for alternative 4.7uF caps. There might need to be some more tweaks to fit a WIMA 37.5mm as the PCB is only 38.1mm tall!!

I'll add the extra holes so the PCB can be cut in two for single channel apps but I think I will need to make it a little wider to do this. I might also move the holes in towards the centre to allow more room for the fixing bracket bend radius - which reminds me, is there any favourite standard off the shelf bracket I should design for?

Cheers

Ian

 

[michal_k]

I think you should check your local castorama or whatever you have in UK and perhaps include L-brackets with PCBs so that everybody has a nice fit.

 

[culteousness1]

What about slots instead of holes? With slots everyone could use simple L-brackets and washers from the local hardware store.

 

[ruffrecords]

I think you should check your local castorama or whatever you have in UK and perhaps include L-brackets with PCBs so that everybody has a nice fit.

Something like this?


http://www.diy.com/diy/jsp/bq/nav.jsp?action=detail&fh_secondid=9281752&fh_view_size=12&fh_start_index=12&fh_location=%2f%2fcatalog01%2fen_GB%2fcategories%3C{9372015}%2fcategories%3C{9372044}%2fcategories%3C{9372218}%2fspecificationsProductType%3dbrackets&fh_eds=%C3%9F&fh_refview=lister&isSearch=false

Cheers

Ian

 

[TubeUser]

Hi Ian;

thanks a lot for sharing this project with us and commenting it. I learnt new things from your comments, this is precious.

I have one thought; beginners or people who only want one channel could make it point to point and learn even more. I'm saying it because i found out it's faster and cheaper to make it p2p if it's only one channel. The same goes for psu; simple CRC or even regulator can be made p2p much faster and this way there is room for improvements, changes, customization, etc.
I often make line amp or even preamp completely p2p; amp/preamp on custom tagboard (costs less once you have tools, and functions better because it can be customized for particular project) and psu (HT, relays, heaters & phantom) on veroboard. It's built faster (if i don't have premade layout or pcb), more reliable, and one learns a lot about grounding, cooling, crosstalk, reading datasheets, etc.

Cheers,
Greg

 

[michal_k]

I think you should check your local castorama or whatever you have in UK and perhaps include L-brackets with PCBs so that everybody has a nice fit.

Something like this?


http://www.diy.com/diy/jsp/bq/nav.jsp?action=detail&fh_secondid=9281752&fh_view_size=12&fh_start_index=12&fh_location=%2f%2fcatalog01%2fen_GB%2fcategories%3C{9372015}%2fcategories%3C{9372044}%2fcategories%3C{9372218}%2fspecificationsProductType%3dbrackets&fh_eds=%C3%9F&fh_refview=lister&isSearch=false

Cheers

Ian

this one looks perfect.

 

[ej_whyte]

I would be in for a stereo set  

Where do A, B and C relate to with the EQ schematic?

Cheers

 

[ruffrecords]

Hi Ian;

thanks a lot for sharing this project with us and commenting it. I learnt new things from your comments, this is precious.

I have one thought; beginners or people who only want one channel could make it point to point and learn even more. I'm saying it because i found out it's faster and cheaper to make it p2p if it's only one channel. The same goes for psu; simple CRC or even regulator can be made p2p much faster and this way there is room for improvements, changes, customization, etc.

I agree 100%. If you look on this page of my web site http://www.customtubeconsoles.com/products.html and scroll to the bottom you will see a p2p prototype of a tube mic pre that uses two stages identical to the circuit I have proposed for the gain make up stage, built into a die cast box. It has a separate p2p power supply built into another die cast box and has been in constant use by a client for over a year now. The beauty of this approach is that it is easy to modify and you can quickly sort out all the grounding and power supply issues.

Once the circuit was proven I committed it to PCB and if you scroll up a bit you will see the twin channel  (mic pre) demo unit which is basically four mu followers on a PCB. If you look closely you will see there is an uncanny resemblance in the way the mu follower is laid out there and the layout I have suggested for the gain make up stage. Even so, the PSU for this was entirely p2p and it is only comparatively recently that I have developed a CRCRCRC HT PCB and also a Phantom PSU PCB (which I offered here a while back).

Scrolling further up you will see the 6 into 2 all tube mixer I am working on which takes the twin channel layout and makes it into a plug in card with attached front panel. Again, its PSU is largely p2p and the headphones amp for it will be 100% p2p.

So, yes, p2p is great and I highly recommend it.

Cheers

Ian

 

[ruffrecords]

Where do A, B and C relate to with the EQ schematic?

To ensure the overall gain is unity with the controls set flat you need a pot at the input to the gain make up amp. That is the connection to point C.

If you also want to have an EQ bypass switch you need to replace the EQ with a pad in the bypassed position; the input to that pad is point B and its output is point C.

Cheers

Ian

 

[strangeandbouncy]

Hi Ian,


  wow. followed link. Your tube mixer looks fantastic. All your philosophy rings true to me. Wish I had loads of money . . . Oh well . . .


  I really am incredibly grateful for all your time and dedication to this project. We are not really worthy . .. oh,all right then. we are . . .


      Kindest regards,


      ANdyP