Hello Jacco,
feel free to steal any design idea, it's posted here for that...
and thanks for your kind words concerning the look, I designed housed for the past 4 years, so naturally i wanted to design something smaller (and quiquier!)
as for the chassis description, it actually is quite easy, the 2 heatsinks are screwed together with 3 aluminium bars (1 bottom, and 2 upside) then all is screwed to the front pannel .
then all wiring comes from the center, the transformer is against the faceplate and the caps (psu) are screwed with their sockets to the central aluminium bars...
if you need something specific, do not hesitate!
as for the dust,
let's say that the dust can be blown away times to times with a air spray for computers...but I like it as is, looks like a star wars spaceship, I enjoy looking at all the parts , so I guess i'll do with the dust anyway...
Vince
feel free to steal any design idea, it's posted here for that...
and thanks for your kind words concerning the look, I designed housed for the past 4 years, so naturally i wanted to design something smaller (and quiquier!)
as for the chassis description, it actually is quite easy, the 2 heatsinks are screwed together with 3 aluminium bars (1 bottom, and 2 upside) then all is screwed to the front pannel .
then all wiring comes from the center, the transformer is against the faceplate and the caps (psu) are screwed with their sockets to the central aluminium bars...
if you need something specific, do not hesitate!
as for the dust,
let's say that the dust can be blown away times to times with a air spray for computers...but I like it as is, looks like a star wars spaceship, I enjoy looking at all the parts , so I guess i'll do with the dust anyway...Vince
Just for info, I just braught it at a friends who has 2 Jeff Rowland 600w monoblocks to drive his Spendor FL-10, and we plugged the citation instead to compare, althought it's only about 20 to 30watts on 8 ohm it just blown away the jeffs
it shown deep bass and sounded just great , very smooth in the medium,
we only noticed that it was much less rich in med highs , but the overhall result was just great , thanks again Nelson PASS ,
This design in the legacy projects is just incredible...
I will follow with the A30, and A40
it shown deep bass and sounded just great , very smooth in the medium,we only noticed that it was much less rich in med highs , but the overhall result was just great , thanks again Nelson PASS ,
This design in the legacy projects is just incredible...
I will follow with the A30, and A40
You will find the IRF240 and 9240 commonly available, and
I think they are a bit better.
For Source-follower applications (this one) the brand doesn't
matter much. When you get into voltage gain (common source
connection) the Harris has a better P channel process, and
the N channel devices are about the same.
I think they are a bit better.
For Source-follower applications (this one) the brand doesn't
matter much. When you get into voltage gain (common source
connection) the Harris has a better P channel process, and
the N channel devices are about the same.
Hello Alex,
sure follow the irfp 240/9240 combo instead of the 130 there is a real sonic diffrence...and they are easy to find...
also keep in mind that when you'll first start it with a regular 150mA bias it will sound fine, but youmay be tempted to rise it up, so in this matter i'll suggest to get big heatsinks since the biginning...believe that you'll be surprised by how good it will sound with about 1Amp bias (but if you do so with only the 2 devices as in the schematic, do not exceed 25 to 28V supply...)
if you run the classic +-40v then forget it with only 2 devices...
as for the heatsinks calculation , I have to admit that I do not know how to evaluate, so just look at mine about 2kg per channel
they are just ok for 50w total dissipation...
Vince
sure follow the irfp 240/9240 combo instead of the 130 there is a real sonic diffrence...and they are easy to find...
also keep in mind that when you'll first start it with a regular 150mA bias it will sound fine, but youmay be tempted to rise it up, so in this matter i'll suggest to get big heatsinks since the biginning...believe that you'll be surprised by how good it will sound with about 1Amp bias (but if you do so with only the 2 devices as in the schematic, do not exceed 25 to 28V supply...)
if you run the classic +-40v then forget it with only 2 devices...
as for the heatsinks calculation , I have to admit that I do not know how to evaluate, so just look at mine about 2kg per channel
they are just ok for 50w total dissipation...
Vince
Where did you get your stylish heatsinks? homeade? because I think they look really neat.
I am thinking about using a torodial, dual winding transformer on this, does this sound like what most people do?
Okay, this question I am trying to answer myself with my tube knowledge, but I think I may have it wrong. in [triode] tubes, the bias current is equal to the current being drawn by the plate(the anode). so in a solid state amp, the bias current is equal to the current being drawn by the collector? so this Bias pot should be just a trim pot right? no high wattage nessicary?
also, looking over the schematic, i noticed that the circle Q4 (an MPS-L01) is half-hashed, half solid. Q4 is right next to the bias pot
On the caps, should I try to go black gate on them? or will it cost too much for little return?
Finally, what are the values of C7, and R20? they are directly connected from the output to the ground
Thanks alot, you guys are really helpful
-Moose
I am thinking about using a torodial, dual winding transformer on this, does this sound like what most people do?
Okay, this question I am trying to answer myself with my tube knowledge, but I think I may have it wrong. in [triode] tubes, the bias current is equal to the current being drawn by the plate(the anode). so in a solid state amp, the bias current is equal to the current being drawn by the collector? so this Bias pot should be just a trim pot right? no high wattage nessicary?
also, looking over the schematic, i noticed that the circle Q4 (an MPS-L01) is half-hashed, half solid. Q4 is right next to the bias pot
On the caps, should I try to go black gate on them? or will it cost too much for little return?
Finally, what are the values of C7, and R20? they are directly connected from the output to the ground
Thanks alot, you guys are really helpful
-Moose
Hi Moose,
thanks for the heatsinks, got them in a pack (from an engeneer that retired...)
for the toroidal, yes most people use them, but sometimes when bias is high, some can produce noise...I also used one in my citation, and it makes a small noise when fonctionning...I don't have this problem with the "R" transformer that I put in my A30 (even with 10amps at idle, it doesn't produce any vibration...)
Vince
thanks for the heatsinks, got them in a pack (from an engeneer that retired...)
for the toroidal, yes most people use them, but sometimes when bias is high, some can produce noise...I also used one in my citation, and it makes a small noise when fonctionning...I don't have this problem with the "R" transformer that I put in my A30 (even with 10amps at idle, it doesn't produce any vibration...)
Vince
for the trimpot, you are right a low wattage is ok...but I'd suggest a good quality one, with a multiturns screw...(be carefull it has to be good quality, so it will allow you to set the bias constantly with no big steps...)be carefull, this is the one that can flash the outputs fets in one second if you don't manipulate it slowly and carefully...
as for the Black gate caps, sorry I can't help, I never tried them and don't even know if i'd hear the diffrence...but can assure you that it works great with regular caps...
Vince
as for the Black gate caps, sorry I can't help, I never tried them and don't even know if i'd hear the diffrence...but can assure you that it works great with regular caps...
Vince
Hi all. My Citation 12 developed hum in one channel, PS caps I would bet. I put a Kenwood KA 701 in it's place for now. It makes a moderately respectable noise source till I can get around to things. So I am thinking of doing the Pass MOSFET mod. Google got me here. Trying to catch up on decades of being out of the Audio and related electronics feild.
I have found a single source (under $50 total) for all the parts listed except the MPS-LO1 Motorola, they suggest MPSA43. But I was wondering if new components have come out since then that need considerations. So on a search I found this thread and the mention of "240/9240 combo instead of the 130". read some of the comments as it seems bob is building from scratch where at best I will be lucky to do the original mod using as many original parts as possible. I have way to much in other time and energy demands to go much past that. Though there is mention of some boards avail for full complementary rather than what I assume is the quasi complementary design of the original mod?
So I guess I am looking for input as to my best ROI. I am not in a position to drop a bundle or spend much time unfortunately. But I do appreciate sound. Can any one help me draw a line? If it helps, it will be fed by an HK 20/ AT 20 w/ Advent receiver as preamp and AR 91's. I mean other than 3A's, how much more budget old school can I get?
I have found a single source (under $50 total) for all the parts listed except the MPS-LO1 Motorola, they suggest MPSA43. But I was wondering if new components have come out since then that need considerations. So on a search I found this thread and the mention of "240/9240 combo instead of the 130". read some of the comments as it seems bob is building from scratch where at best I will be lucky to do the original mod using as many original parts as possible. I have way to much in other time and energy demands to go much past that. Though there is mention of some boards avail for full complementary rather than what I assume is the quasi complementary design of the original mod?
So I guess I am looking for input as to my best ROI. I am not in a position to drop a bundle or spend much time unfortunately. But I do appreciate sound. Can any one help me draw a line? If it helps, it will be fed by an HK 20/ AT 20 w/ Advent receiver as preamp and AR 91's. I mean other than 3A's, how much more budget old school can I get?
I had a pair of those back in the 80's.
They sounded great. Did you have to repair yours, in the meantime? I happened to trade mine off around 2000 or 2001.
The guy who bought them, blew them to pieces! I guess the rubber surround was getting brittle.
Nearly forgot, I have a friend who is the happy owner of the Citition 12. The psu caps were changed at some point and its still doing great service. Come to think of it, he also had some rubber suspension changed! Hum is most likely from the PSU caps.
Steen
I was afraid of this. Now I will probably get sucked into this forum. And I mean that in the nicest of ways. It's just that I do not need another diversion of my time. I love old school audio but have not had the resources, time, money, energy, ... to be too involved for many many years. Now I am at a point of being able to slowly step back in.steenoe said:
I was a Manufactuers Rep for audio products in the 70's. In fact I was a rep for AR when they intro'd the line the 91's were in. Travelled around with 9's and I think it was 90's across 6 SE states demoing and lecturing on them. and Marantz, Maxell, Kenwood, Audio Technica, Nagatronics, and many others.
steenoe said:
Bought these e-bay last year. Hooked them up to my son's LO9M's. rated at 600W RMS 2K peak into 4ohms. The 91's just sang! For over an hour, backs of the cabinet/ xovers were warm to the touch! Then a surround blew. Took them to a very well regarded local reconer and he said they had already been and not done well. The surround came loose from the cone in one spot.
Got my first Citation 11 and 12 when they first came out. I was selling HK and got a special deal. Sold them years later for more than twice. This one was one of my first "buying my youth back" e-bay purchases some years back. Along with my Silvertone 1482 guitar amp. Which needs retubing. I have a friend that has 2 of these literally sitting around.steenoe said:Nearly forgot, I have a friend who is the happy owner of the Citition 12.
Steen
to be precise I'll describe quickly the schematic from my memory:
input is made of a differential(of PNP devices BC416C in my case)
then there's a driver BC 414C(in my case) and you also got the Vbe multiplier,a bias temperature compensation part that is a BC414C(still in my case)
to finish you have a pair of IRFP 9240/240 as final drivers(only in the complementary version)
now for clear chart and refering to Nelson's complementary version, here is the combo that can be done:
MPS L51: BC 416C (PNP)
MPS L01: BC 414C(NPN)
and if you can't get them I'll suggest BC 560C/550C(sorry at 1oclock past midnight ) ican'tremember which is the npn and pnp
Cheers!
Vince
input is made of a differential(of PNP devices BC416C in my case)
then there's a driver BC 414C(in my case) and you also got the Vbe multiplier,a bias temperature compensation part that is a BC414C(still in my case)
to finish you have a pair of IRFP 9240/240 as final drivers(only in the complementary version)
now for clear chart and refering to Nelson's complementary version, here is the combo that can be done:
MPS L51: BC 416C (PNP)
MPS L01: BC 414C(NPN)
and if you can't get them I'll suggest BC 560C/550C(sorry at 1oclock past midnight ) ican'tremember which is the npn and pnp
Cheers!
Vince
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