2chanell PCL86-PP "tube buster" for guitar

davorin · 28th November 2009, 07:19 AM

Small 2-channell amplifier with 4xPCL86 tubes (2x14W) for build in full solid-state guitar amp (HOHNER Force-CD400sc). Also replaced original speakers with 2 CELESTION-super8 speakers.

davorin · 28th November 2009, 07:33 AM

Sound is now very closed to "all tubes" amplifiers, although pre-amp, reverb and chorus are solid-state (ships). With small modifications can use ECL86 (6GW8) tubes, but PCL86 are much cheaper!

Geek · 28th November 2009, 07:45 AM

There's another nice one

Do you get enough gain with just the PI being the input stage?

Cheers!

davorin · 28th November 2009, 08:25 AM

Yes, I have enough gain (NO overall feedback!). There is 2 original (stereo?) pre-amp outputs at back side of chassis. The third pre-amp mono output I created with 2 resistors 47kOhms from both channels. For full power(14W/4%THD) amps need ~1,5Veff.

jjman · 29th November 2009, 10:43 PM

Does having 100k (pot) across the input, and therefore the guitar's pickups, load down the signal too much at that point? I guess active PUs wouldn't care.

Geek · 30th November 2009, 01:21 AM

Quote:

Originally Posted by jjman

Does having 100k (pot) across the input, and therefore the guitar's pickups, load down the signal too much at that point? I guess active PUs wouldn't care.

It would chop the treble on high output overwound passives, but if your pickups are silly bright already, it can even things out some.

(bassists will load their pickups as low as 4.7K and boost the gain to get a "Hofner" tone for instance)

Cheers!

davorin · 30th November 2009, 04:21 AM

Output impedance from basic pre-amp (Höhner) is ~10Kohms (Uout is ~2Veff). Potentiometer 2x100Kohm is something like master volume, but it is here only to set correct level to output amplifiers. Value of 2x250Kohm give me more gain and bass, but I do not need them.

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28th November 2009, 07:45 AM	#3
Geek diyAudio Member Join Date: Sep 2004	There's another nice one Do you get enough gain with just the PI being the input stage? Cheers!

28th November 2009, 08:25 AM	#4
davorin diyAudio Member Join Date: Aug 2005 Location: Zadar, Croatia	Yes, I have enough gain (NO overall feedback!). There is 2 original (stereo?) pre-amp outputs at back side of chassis. The third pre-amp mono output I created with 2 resistors 47kOhms from both channels. For full power(14W/4%THD) amps need ~1,5Veff.

29th November 2009, 10:43 PM	#5
jjman diyAudio Member Join Date: Jan 2009	Does having 100k (pot) across the input, and therefore the guitar's pickups, load down the signal too much at that point? I guess active PUs wouldn't care.

30th November 2009, 04:21 AM	#7
davorin diyAudio Member Join Date: Aug 2005 Location: Zadar, Croatia	Output impedance from basic pre-amp (Höhner) is ~10Kohms (Uout is ~2Veff). Potentiometer 2x100Kohm is something like master volume, but it is here only to set correct level to output amplifiers. Value of 2x250Kohm give me more gain and bass, but I do not need them.

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