Topic: PREROTICA... a tube preamp...

[JojoD818]

It works without smoke! 

[s2kov]

Jo,

Galing pre!!!! ito na ba yun?

It works without smoke! 

[JojoD818]

Andy,

Yes pre ito na yun, so far the phono is doing well, pero sasanayin ko muna yun ears ko sa kanya asis before applying the fourth time constant sa RIAA net.rwork.

Will give you my findings as soon as I have them, may it be successful or not.

JojoD

[s2kov]

thanks pre....

[eXg]

pero sasanayin ko muna yun ears ko sa kanya asis before applying the fourth time constant sa RIAA net.rwork.

ano na namang magic yan ... i call it magic coz i don't understand 

[JojoD818]

ano na namang magic yan ... i call it magic coz i don't understand 

Hehehe, it's no magic sir, it's just that the RIAA of this particular phono stage is upgradeable to obtain a 4th time constant for a more truthfull/accurate RIAA EQ network. It will only put the network nearer to the recommended RIAA specs. 

So far it is still what I use as preamp now.

[wanderlust]

oy.......... kaw ba ngpakagawe nyan sir s2kov?

as early as now i cn see na another successful projct na naman to sir jo! oks pa sa design.

[JojoD818]

oy.......... kaw ba ngpakagawe nyan sir s2kov?

as early as now i cn see na another successful projct na naman to sir jo! oks pa sa design.

Sir wanderlust, s2kov can build his own as you can see from his projects. He is just interested in the circuit I used so he can build his own. 

So far so good, nadinig na nga ni Hans kahapon, kaso kulang pa sa butingting. 

Thanks!

[s2kov]

Ganun ba! Eh di, pwede ko na din simulan?

Sir wanderlust, s2kov can build his own as you can see from his projects. He is just interested in the circuit I used so he can build his own. 

So far so good, nadinig na nga ni Hans kahapon, kaso kulang pa sa butingting. 

Thanks!

[JojoD818]

Ganun ba! Eh di, pwede ko na din simulan?

Ok na s2kov, pwede mo na start, pati yun 4th time constant approve na upgrade. 

Good luck sir!

[s2kov]

Thanks pre.... Did you raise the B+ to 386V? How about the resistor for the 4th constant, where did you get those values?

Ok na s2kov, pwede mo na start, pati yun 4th time constant approve na upgrade. 

Good luck sir!

[JojoD818]

Thanks pre.... Did you raise the B+ to 386V? How about the resistor for the 4th constant, where did you get those values?

Yes I did used a higher B+ for the supply.

The 4th constant resistor is made up of 909R + 56R for a total of 965 Ohms which is right on the target. I got them from my brother abroad, but Frank expressed that a 1Kohm resistor will yield excellent results also with no difference at all.

Better buy a handful, so you can match values especially for the caps in the RIAA network. Though a capacitance meter is a must for caps, a reliable DMM would be helpful on the resistors.

HTH,
JojoD 

[eXg]

I considered myself endowed with spartanic self-control  ... until this moment.   The new preamp of the JojoD is just so enticing to let it pass thru' my hands (to its rightful owner) w/o listening to it.  So here I am, writing and listening  (or better yet enjoying this new toy).  I know nothing of its circuitry so I will skip those entails.  But I am neither good at prose nor in describing the nuances of what I hear.

Linestage and Phonostage easily matches (if not excel  )   my europrean-brand integrated all tube amp.  (And am currently pairing this preamp with an SS DIY-power amp )

Anyways, my impressions don't matter to someone else's ears...  instead here's a loud and proud "cheers" to the one and only Mr GC, Mr Prerotica, Mr Magician aka JOJOD.  Buddy, thanks for sharing your talent!!!  If GE (or is it Philips ) brings light to every home, you bring HIGH to this community's audio addicts.   

 

[JojoD818]

I considered myself endowed with spartanic self-control  ... until this moment.   The new preamp of the JojoD is just so enticing to let it pass thru' my hands (to its rightful owner) w/o listening to it.  So here I am, writing and listening  (or better yet enjoying this new toy).  I know nothing of its circuitry so I will skip those entails.  But I am neither good at prose nor in describing the nuances of what I hear.

Linestage and Phonostage easily matches (if not excel  )   my europrean-brand integrated all tube amp.  (And am currently pairing this preamp with an SS DIY-power amp )

Anyways, my impressions don't matter to someone else's ears...  instead here's a loud and proud "cheers" to the one and only Mr GC, Mr Prerotica, Mr Magician aka JOJOD.  Buddy, thanks for sharing your talent!!!  If GE (or is it Philips ) brings light to every home, you bring HIGH to this community's audio addicts.   

 

I thought you wouldn't try it in your gears after I left, seems it's kinda irresistable. 

Enjoy!

[arnoldc]

maganda talaga yan, design ni Frank De Grove yan eh.

[JojoD818]

maganda talaga yan, design ni Frank De Grove yan eh.

actually hindi, it's a basic RCA phono stage with an Allen Wright mod. si Frank ang tumulong sa akin sa RIAA. dba nandun ka pa nga.

[arnoldc]

i see. sa dami ng usapan sa thread na yun, nalito na ko. so ito yung chris_phono? (stock RCA design with 12AX7)

[s2kov]

akala ko ako lng nalito sa thread na yun....

[H a n $]

Masta jojoD,

Congrats again was able to hear this preamp and galing talaga!!..

[arnoldc]

so, sinong gagawa ng fdegrove phono?  ikaw na andy? 

[s2kov]

still contemplating what circuit to use. maybe i'll try first frank's phono design if it will work and sounds good para nde na rin ko magpalit ng x'former.... kpag nde maganda result, si chris na din....

[JojoD818]

Masta jojoD,

Congrats again was able to hear this preamp and galing talaga!!..

Uy thanks! 

siopao ulit next time. 

[JojoD818]

arnoldc, s2kov,

hehehe, nakakalito talaga yun thread pero ganito na lang. yun chris and fdegrove phono are both rca basic phono preamps. yun kay chris eh re-written schematic lang pero yun kay frank used mr. allen wright's mod for the RIAA compensation.

i tried both and end up using the one from frank because of it's superior sound quality over chris's version. only problem with frank's modded circuit is medyo namimili ng caps, i thought hindi na madidinig pero I was wrong. so I ended up matching caps for the phono. fwiw, in a certain point of view, arnoldc is correct in saying it is frank's circuit since he is the one to compute the exact value for the resistor. 

o ayan malinaw na ba mga sirs? 

[JojoD818]

so, sinong gagawa ng fdegrove phono?  ikaw na andy? 

arnoldc,

remember you ask me to design a pcb version? parang masmaganda at exciting yata kung p2p na lang. sabi pa ni frank and others na magkaiba daw tunog ng pcb version at p2p, any comments?

oh, syempre mas madali pag pcb, saksak na lang parts. 

[arnoldc]

jojo, on secontot, mas mahirap parts rolling sa PCB

[Garp]

Hi JojoD, as usual nice work. Roughly based on the RCA circuit yan di ba using 12ax7? How do you get around the minimum 220K input impedance for the amp or is this a non-issue? Thanks. I have been tempted to convert the tono preamp into a phono (kahit wala akong TT) and I've collected about several circuits using only two tubes kasi.

[JojoD818]

jojo, on secontot, mas mahirap parts rolling sa PCB

exactly, and mas mahaba signal path due to re-routing. di gaya ng p2p, parang "straight to the point" 

[JojoD818]

Hi JojoD, as usual nice work. Roughly based on the RCA circuit yan di ba using 12ax7? How do you get around the minimum 220K input impedance for the amp or is this a non-issue? Thanks. I have been tempted to convert the tono preamp into a phono (kahit wala akong TT) and I've collected about several circuits using only two tubes kasi.

Thanks Garp!

Again you are really doing your homework, Indeed it has a minimum load of 220K and as I figured out from other reference materials, there are two ways to get around this. 1) is to use a 250K pot (easy  ), and 2) is to insert a cathode follower right after the last stage of the phono circuit. The minimum output impedance will then be dictated by the CF.

JojoD

[Garp]

Thanks Garp!

Again you are really doing your homework, Indeed it has a minimum load of 220K and as I figured out from other reference materials, there are two ways to get around this. 1) is to use a 250K pot (easy  ), and 2) is to insert a cathode follower right after the last stage of the phono circuit. The minimum output impedance will then be dictated by the CF.

JojoD

Thanks very much Jojo! Now I only have to research how a CF is done.

[s2kov]

RCA Phonostage with lower B+