[BUILD] GIX-51X tube preamp

[gemini86]

Sorry about the bom errors, guys. Bruce, do you have a good part number for the rotary switch? The part i put on the bom is not the one i used, since i accidentally ordered a solder lug version (it was mbb though).

 

[bruce0]

I was looking for stock in MBB/Shorting, and I think I am going to order a Lorlin CK1054 from mouser.  It has a 38mm long flatted shaft so I guess I need to cut it and I am hoping that my knobs will fit, I haven't checked where the flat is.  They also have a MBB 6mm round shaft I think. 

 

[gemini86]

I do know that some of mousers part descriptions are off when it comes to lorlin. Check the part numbers against the data sheet. I kindof like the alpha switches better.

 

[bruce0]

I had another project with a MBB switch, so I opened up one of the switches, and the way they make them BBM is they have little "risers" between the contacts.

This is the BBM

This is the MBB version, no bumps, the contact rides down and makes before breaking.

If I only had a little chisel... To remove the bumps. So I hammered on an old worn out soldering iron point, and clipped the end.

At about 600 degrees F the plastic is very soft, but not liquid.  Cooler may be better.  God only knows what fumes I breathed when doing this, I was careful to leave no little pieces in there.  And I didn't know what type of grease was in there (speak up if you do) so I use a little de-oxit.

It doesn't look pretty, and it took 20 minutes for one switch (after making the tool, which needs to be sharp and narrow, if I had a narrow chisel it would be better, they would pop off clean and pretty).

The switch works like a MBB now, and when changing the gain the changes are better.  Still not super clean.  Stop 4 is always a pop because of the electrical architecture  ( I wonder if a high value drain or leak resistor somewhere would fix that) it pops the first time you turn past it.  Anyway after that test I am sure that MBB would be better, and I ordered the MBB parts from mouser, I can always change the switch shafts and use the ones I have.

If you do pop one of these apart, keep the shaft pulled tight into the front section or you might lose the little ball and spring, which is small, and can be hard to get back in.  You will almost always dislodge the contact spring which is loose.  There is no problem with that but you will wonder where to put it back so I thought this picture would help, you put it back right next to the number like this.

 

[gemini86]

breathe it in, fellas. This is what diy smells like. (burning plastic)

 

[irfrench]

Right,

So I'm getting ready to test this beauty out. 8)

For my own purposes, and for anyone else wanting to do so, can you recommend a test measurement procedure?

Can I simply plug in the unit without valves/tubes installed and measure the voltages to the relevant pins or do I need a dummy load of some kind?

Thanks,
Ian

 

[gemini86]

I would have tubes in. They tough a nails and can take a lot of abuse if something isn't right. They're the best kind of dummy load.

 

[okgb]

a.f.a.[we]k.  what / where is the most accurate up to date mouser bom ?
is it post one or Bruce's  ? tia
ouch my mouser order is going to be big ..................

 

[jandoste]

Hey guys,
I can't find RV16AF-41-15R1-A50K on mouser... do you have any other ref n°?
Thanks

 

[bruce0]

Check your BOM and don't buy 105-2454 which is BBM you need to choose a MBB gain switch, otherwise the most recent BOM I posted is partial mouser version 7 which has that BBM switch (incorrectly)..  As far as the pot is concerned I got it at  mamouth electronics.http://www.mammothelectronics.com/RV16AF-41-15R1-A-p/210-100-a.htm i think it is just log with longish pins for vertical mounting

 

[irfrench]

jandoste,

I'm just about to test my first one (valves arrived today).

I had the same with my mouser BOM, so for the Pot I just used a 'normal' A50K pot with solder lugs and used spare wire (trimmed resistor legs) instead of the specified long pins.

Ian

 

[tonycamp]

Hey fellas,

I'm going to be ordering stuff monday, Please pardon me if i missed it, but is there one solid and correct BOM available? or maybe a shopping cart? If not, when i'm done my orders, and finished my builds, i will post every piece in my BOMS, and try to make a single(or a few) shopping cart out of them. The least i can do after Rodney and Bruce did so much work on this!

thanx
guys

 

[jandoste]

Hey guys,
thanks for the update!
so Tonycamp please share your BOM with us
Cheers

 

[irfrench]

Evening.

A quick note to say it fired up OK!

It sat there for 15mins with no flames or smoke so it's not dangerous at least.

I do have a slight issue with LF thumping, flicking the HPF to 50/120hz helps get rid of it.  I had not included the RodneyCap(TM) on the hv board, is that needed in conjunction with Bruce0s mods?

Thanks
Ian

 

[jandoste]

I found this one... what do you think that can I go with this Alpha ?
http://fr.mouser.com/ProductDetail/Bourns/51AAA-B28-D18L/?qs=sGAEpiMZZMtC25l1F4XBU7rZyhV5cpJRbFi75AXK5JU%3d

Thanks

 

[gemini86]

hey guys!

thanks for hanging in there...

The BOM will be edited as soon as I find a suitable switch. Mouser doesn't seem to have a MBB(shorting) switch with round shaft AND pcb pins. Everything is D shaft. So if you're using regular set screw type knobs, tD shaft will work fine, not so sure about collet knobs, though... anyone have experience with that?

Mouser MBB(shorting) with D shaft: 10WA344
Mouser MBB(shorting) with roudn shaft (this has solder tabs, so you'll need to snip them off to use on the pcb) 105-13571

Both are lorlin. Alpha witches are also good as an alternative.

Ian, the "rodney" cap is required to stabilize the low frequency oscillation. The other added filtering components noted by bruce are for filtering out any residual high frequency noise.

 

[irfrench]

;D ;D ;D ;D ;D ;D ;D ;D

AWESOME.  This thing sounds GREAT! 

Thanks so much to Gemini86 for the adaptation and for sharing it, and to Bruce0 for the additional work/share on the PSU mods.


In case anyone was wondering what the LF thumping sounds like - I've uploaded a before and after Cap sample:

https://soundcloud.com/minoian/gix-thump


Thanks again - this is ace!

Ian.

 

[mulletchuck]

anyone have a complete mouser cart for this thing?    Gemini, are you gonna do another run of PCBs and metalwork?

 

[gemini86]

If i get enough interest for 25 pieces, I'll order more brackets and face plates. I still have plenty of pcb kits. I had (incorrectly, maybe) assumed that most people would want to diy the face plates.

 

[tonycamp]

;D ;D ;D ;D ;D ;D ;D ;D

AWESOME.  This thing sounds GREAT! 

Thanks so much to Gemini86 for the adaptation and for sharing it, and to Bruce0 for the additional work/share on the PSU mods.


In case anyone was wondering what the LF thumping sounds like - I've uploaded a before and after Cap sample:

https://soundcloud.com/minoian/gix-thump


Thanks again - this is ace!

Ian.

cool news, how bout some samples hitting it hard with a kick drum or bass guitar?