Universal tube preamp PCB, ECC99/6N6P/ECC88/ECC85/6922/6DJ8 etc. MU follower or SRPP

[gary s]

A couple of questions Vunce. Did you select PRP metal film and Takman Carbon film resistors for certain positions for your build?

Also, is the tube socket pins mounting diameter about 21mm for the lands on the pcb?

 

[Koifarm]

I have three PCB's to share for just the shippingcost. If interrested send me a PM.

 

[weissi]

Hi Koifarm, I'd be happy to get them from you => PM.

 

[Koifarm]

now, the PCB”s are all spoken for.

 

[Vunce]

Koifarm,
Your pcb design is sounding very good as my AD1862 dac output stage configured for SRPP with 6n6p tubes and a linear psu.
I had high hopes for the imported little SMPS but it didn’t work out. I was getting an audible low frequency warbly tone plus higher frequency noise heard from the tweeters. I swapped out the SMPS and replaced with a regulated linear HV/LV supply and voilà!! Dead silent background and sounds very good to my ears .
Thanks again Koifarm!

 

[gary s]

Good news Vunce, what linear HV/LV supply did you use?

Also is the diameter for the tube socket pins on the PCB around 21mm, thanks.

 

[Vunce]

Good news indeed Gary .
I’ve got a few answers for ya…
Your correct, 21mm socket pin diameter. The resistors were all in my stash, no PRP’s in 120R but had Takman carbon films in that value.
The PSU board HV section is based on a Maida circuit with a few nice options and the LV section uses schottky diodes and LDO MIC29502 to enable 6.3vdc from a 6.3vac trafo winding.
This supply works nice, I purchased the pcb several years ago from a guy in the States that has since disappeared.

 

[gary s]

OK, thanks for the reply Vunce, have ordered the pcb from JLCPCB and I have about 5 different 6N6P versions to try.

I will also do a reg linear supply - have some circuits including one for the MIC29502 for the filaments.

Good to hear you are impressed.

 

[Vunce]

Solid plan Gary, looking forward to seeing your progress also.
Are you planning to use this circuit as a preamp or some other use?

 

[gary s]

Yeh, as a simple preamp Vunce, looking to see how it performs driving some Pass class A amps. Selectable gain is also a plus.

 

[bloqhed]

Good news indeed Gary .
I’ve got a few answers for ya…
Your correct, 21mm socket pin diameter. The resistors were all in my stash, no PRP’s in 120R but had Takman carbon films in that value.
The PSU board HV section is based on a Maida circuit with a few nice options and the LV section uses schottky diodes and LDO MIC29502 to enable 6.3vdc from a 6.3vac trafo winding.
This supply works nice, I purchased the pcb several years ago from a guy in the States that has since disappeared.

Was the board from hvforless on ebay? I picked up some of his MIC29502 LV filament boards, but never managed to snag his maida + LV boards before he disappeared. I did however manage to find the schematic and might whip some up.

 

[gary s]

That is good news, I would be interested.

Can you post the schematic?

 

[Vunce]

YES bloqhed!! I'd be interested in a few if you do

 

[bloqhed]

Great! I actually have the schematic all drawn up in KiCad a few weeks ago, I have the original BOM, dimensions, pictures of the board and the track layout, so it shouldn't be too hard. I'll get back at it tomorrow and report back with progress.

 

[gary s]

Good news - thanks. Not sure where you are located, but being in Australia, it would be good if you could supply the gerbers, as int postage is still very hit and miss.

 

[bloqhed]

Absolutely! Once I have something presentable tomorrow I'll get a new thread going and let you know. I figure there will be maybe some back and forth, modifications, tweaks, etc, but I plan to keep gerbers and everything available to everyone.

 

[gary s]

Thanks bloqhed, even better news. No rush though.

 

[Koifarm]

Vunce good to hear your happy with the tubestage. Can/will you please share witch SMPS was not good.

 

[Vunce]

I believe its very similar, if not the same, as the SMPS you were working with.

 

[psmith001]

Absolutely! Once I have something presentable tomorrow I'll get a new thread going and let you know. I figure there will be maybe some back and forth, modifications, tweaks, etc, but I plan to keep gerbers and everything available to everyone.

I did a version of this that I'm happy to share the KiCad project with you if it would be of any help to you. The PCB design is done, but I never had it made to test to ensure everything will work. I guess I was holding back to try and see if I could fit everything into the magical 100mm x 100mm.