I'll send Mr.Tibbs a couple more photos soon. The chasis is actually a NAC92. I bought it off EBay last year. But hardly used it because I prefered, by far my super regged Bur Brown op amp line stage. Here again super reg next to the op amps worked wonders versus no super regs. Hence when I saw Ced Taylors Air Guitar. I bit the bullet and canabalised the NAC92. Its a bit like Hot Rodding a Ford Anglia and ending up with a Ford Focus GTI. The Digital input switching is nearly original and works as was. The Balance control, well it doesnt anymore. But I like the knob so I kept it. The Tracos are not very visible on this shot . I dont like input sockets, but I may one day try some balanced ones I guess. I use MAPLIN Shark screened Audio Cable. Cheap but very good. The resistors are RN 60's from Mouser USA. The Capacitors. Elfa, I rang and was kindly told to use there website to order. Which I did no problem. The parts got lost somewhere in Germany. But I mailed Elfa and they offered to resend the order if I checked with the Post Office first. Luckily they turned up the next day anyway. So Elfa I can recommend. The biggest problem (I thought) was getting the Mundorf M-Cap. I tried several places. The supplier I used was German, www.lautsprechershop.de. Good website and quick delivery. The PCB I made myself. Hope some or any of this may help you guys.
Air guitar Pre
- Thread starter sandford
- Start date
chiily
PFM Special Builder
hacker said:Linux is my OS of choice, it's great to see a PCB designer for itI've used QUCS (http://qucs.sourceforge.net) in the past, but it's more of a cicuit designer/simulation that a pcb design tool.
I've got it compiled and up and running.. looks good and easy to use, thanks
Wow, this just passed me by. Great for linux, cheers.
Great pics of the pre-amp too.
Count me in for a couple of boards please.
chrisallan
Go on - bodge it!
I realised that bivalve had posted this early on in this discussion. Is this of any use to someone who can push this on a bit further:
Chris
Thanks for getting the schematic up.
R3/C3 is a RC filter designed to remove the signal modulations on the power rail caused by other parts of the circuit. The mod may be due to LesW but Mr Tibbs recently described it as beneficial on his 102, so I and others subsequently tried it on gain stages and buffers on 321 PCBs and 42s, 62 etc. It has a very nice effect, cleaning up music considerably.
The initially suggested RC values were simply to add a 1K resistor and a 47uF cap. This gives a turnover frequency of 3.4Hz which is good, as an RC filter has rolled off to 0.1% of its in band level by 5 times the turnover frequency. So by 5 times 3.4Hz or 17Hz all the signal modulation has been reduced to 0.1% of its unfiltered value. We have got good attenuation from the bottom of the audio band on up.
Ced's RC filter of 226K/0.1uF gives a turnover frequency of 7Hz which means a bit more LF crap will get through, however the R2 100K/ 0.1uF is also an RC filter on the input signal at the junction of R2 and R4. Its turnover frequency is 16Hz.
The power rail looks like ground to the signal. Well below 16Hz the signal sees 326K to ground (in parallel with the bottom 330K resistor) Well above 16Hz the signal sees only 100K to ground. The parallel impedances with the 330K bottom resistor are respectively 165K and 75K and the ratio is 2.2 times, which means 2.2 times the current will be drawn. I don't think the signal voltage will be reduced by this ratio because of the much lower impedance path to ground through the following 470R or 10K resistor and the Q1 base emitter resistance. However this transition at the bottom of the audio range (5x16Hz=80Hz) makes me uneasy. I think the circuit should be drafted with a R2 much nearer the total 330K resistance for this arm. This will require a bigger cap value. Ced chose a polypropylene film and foil for C3 (and C4) but perhaps this can be relaxed to a mere polypropylene film cap or a Polyester cap to get a larger value with a manageable size and cost. Certainly I got good results with a Silmic. Ced has already recommended to potential redrafters of this circuit that they simply draft for the biggest cap, and run tracks from the terminals to within 5mm say of joining, so that a range of caps can be used.
The above is what I referred to in my ground currents post on Linnik's Christmas Present Thread.
Comments welcome.
David
Thanks for getting the schematic up.
R3/C3 is a RC filter designed to remove the signal modulations on the power rail caused by other parts of the circuit. The mod may be due to LesW but Mr Tibbs recently described it as beneficial on his 102, so I and others subsequently tried it on gain stages and buffers on 321 PCBs and 42s, 62 etc. It has a very nice effect, cleaning up music considerably.
The initially suggested RC values were simply to add a 1K resistor and a 47uF cap. This gives a turnover frequency of 3.4Hz which is good, as an RC filter has rolled off to 0.1% of its in band level by 5 times the turnover frequency. So by 5 times 3.4Hz or 17Hz all the signal modulation has been reduced to 0.1% of its unfiltered value. We have got good attenuation from the bottom of the audio band on up.
Ced's RC filter of 226K/0.1uF gives a turnover frequency of 7Hz which means a bit more LF crap will get through, however the R2 100K/ 0.1uF is also an RC filter on the input signal at the junction of R2 and R4. Its turnover frequency is 16Hz.
The power rail looks like ground to the signal. Well below 16Hz the signal sees 326K to ground (in parallel with the bottom 330K resistor) Well above 16Hz the signal sees only 100K to ground. The parallel impedances with the 330K bottom resistor are respectively 165K and 75K and the ratio is 2.2 times, which means 2.2 times the current will be drawn. I don't think the signal voltage will be reduced by this ratio because of the much lower impedance path to ground through the following 470R or 10K resistor and the Q1 base emitter resistance. However this transition at the bottom of the audio range (5x16Hz=80Hz) makes me uneasy. I think the circuit should be drafted with a R2 much nearer the total 330K resistance for this arm. This will require a bigger cap value. Ced chose a polypropylene film and foil for C3 (and C4) but perhaps this can be relaxed to a mere polypropylene film cap or a Polyester cap to get a larger value with a manageable size and cost. Certainly I got good results with a Silmic. Ced has already recommended to potential redrafters of this circuit that they simply draft for the biggest cap, and run tracks from the terminals to within 5mm say of joining, so that a range of caps can be used.
The above is what I referred to in my ground currents post on Linnik's Christmas Present Thread.
Comments welcome.
David
martin clark
pinko bodger
Peperoni, that looks great; I like the attenuator thingummy.
Now how does it sound...?
Now how does it sound...?
Anderzander
Grateful Bodger
Fantastic pictures!
Any pictures focusing on the cards? Are they standard gain cards?
Any pictures focusing on the cards? Are they standard gain cards?
Superregs those cards arent they ?
mr Tibbs suprisingly i think MAPLIN! omg do those phono sockets
http://www.maplin.co.uk/module.aspx?TabID=1&criteria=phonosocket&ModuleNo=1011&doy=28m1
or if you are into 'special' ones ....
http://cgi.ebay.co.uk/2-RCA-SCKTS-G...oryZ3280QQssPageNameZWD1VQQrdZ1QQcmdZViewItem
mr Tibbs suprisingly i think MAPLIN! omg do those phono sockets
http://www.maplin.co.uk/module.aspx?TabID=1&criteria=phonosocket&ModuleNo=1011&doy=28m1
or if you are into 'special' ones ....
http://cgi.ebay.co.uk/2-RCA-SCKTS-G...oryZ3280QQssPageNameZWD1VQQrdZ1QQcmdZViewItem
This site contains affiliate links for which pink fish media may be compensated.
Hi
Well spotted trancera, yes they are Andy's super regs. They are supplied from two of Les's APX PSU's running at 30V with the super regs set at 24.7V. The stepped attenuator is the cheap one from Hong Kong I think. The selector is a DACT 5 way switch. You are also correcton the sockets, they are Maplin standard Phono Sockets which seem to work suprisingly well.
How does it sound - bloody good - when I get the parts and put it into the real case with a phono stage and remote control I will take it round for a toe to toe with my brothers 52 / supercap. I can say that it soundly whips an ATC SCA2 which will appear on E-Bay soon.
Any one near to Bristol is invited to come and have a listen, I also have one spare etched board if anyone is interested.
More listening now.
Cheers
Nick
Well spotted trancera, yes they are Andy's super regs. They are supplied from two of Les's APX PSU's running at 30V with the super regs set at 24.7V. The stepped attenuator is the cheap one from Hong Kong I think. The selector is a DACT 5 way switch. You are also correcton the sockets, they are Maplin standard Phono Sockets which seem to work suprisingly well.
How does it sound - bloody good - when I get the parts and put it into the real case with a phono stage and remote control I will take it round for a toe to toe with my brothers 52 / supercap. I can say that it soundly whips an ATC SCA2 which will appear on E-Bay soon.
Any one near to Bristol is invited to come and have a listen, I also have one spare etched board if anyone is interested.
More listening now.
Cheers
Nick
Anderzander
Grateful Bodger
I'd like the board Nick .....
It's a real inspiration seeing yours together.
.....It's a real inspiration seeing yours together.
jonnoshore
physicist, engineer and healer
I'm interested in that board too, but Anderzander's was first...
Which leads me on to ask... What happened to the group buy of the board professionally made?
I am extremely keen still and I am sure others are.
Is the latest design known yet there was mention of a further improvements although rereading it CED suggests no TA boards..
Which leads me on to ask... What happened to the group buy of the board professionally made?
I am extremely keen still and I am sure others are.
Is the latest design known yet there was mention of a further improvements although rereading it CED suggests no TA boards..
Hi Anderzander
No problem to send the board. But just to stress the board is the non time aligned version and there is no provision for the switch on relay. I never switch my stuff off and thought it was unnessasary for me.
If that is OK I can send the board and a list of parts and who they came from to you. PM me to arrange.
Nick
No problem to send the board. But just to stress the board is the non time aligned version and there is no provision for the switch on relay. I never switch my stuff off and thought it was unnessasary for me.
If that is OK I can send the board and a list of parts and who they came from to you. PM me to arrange.
Nick
jonnoshore
physicist, engineer and healer
Ok all,
I spent ~ an hour this morning trawling the thread to get
( names - no. of boards - useful info for pcb/design in thread # ) information below.
This can be used to start a group buy sticky thread it will just need people to confirm to whoever sorts out the order not in the thread I assume by PM... Info is pretty self explanatory:
I counted 35 posts of 'I'll have one/two' etc... + 10 names who may be interested... so potentially we could have 40-50 boards needed. I am sure if more people knew what a AG pre was there may be even more wanting boards.
****
All the people who have expressed an
interest for a AG board(s):
Sandford/Matt - 1 - info on #26/27
Bivalve/David - 1
Linnik/Oz - 3 - info #71
TimH - 1 - Info #90
JimmyB - 2 - with pcb contacts
Mike Hanson - 1+
IanAG - 2
Hacker - 1
John.luckins - 2
cromodora - 1
rdg - 2
S-Man/Dave - 2
Chiily - 1
peperoni - 2
Agisthos - 2
new naim boy/Aidan - 1
Chrisallen - 1 - quotes? #75/76
Anderzander - 1 - pcb contact #64
VTA/Adam - 2
RichardH - 1
Jonnoshore/John/Me - 2
Muzzer - 1
Markt - 2
35
Other people who posted on this thread
and may be interested?
Paul Ranson
Lilolee - Lee
Paul L
Martin Clark
peranders
Jeff D
Trancera
Mr Tibbs
almichie
Andy W?
***
I spent ~ an hour this morning trawling the thread to get
( names - no. of boards - useful info for pcb/design in thread # ) information below.
This can be used to start a group buy sticky thread it will just need people to confirm to whoever sorts out the order not in the thread I assume by PM... Info is pretty self explanatory:
I counted 35 posts of 'I'll have one/two' etc... + 10 names who may be interested... so potentially we could have 40-50 boards needed. I am sure if more people knew what a AG pre was there may be even more wanting boards.
****
All the people who have expressed an
interest for a AG board(s):
Sandford/Matt - 1 - info on #26/27
Bivalve/David - 1
Linnik/Oz - 3 - info #71
TimH - 1 - Info #90
JimmyB - 2 - with pcb contacts
Mike Hanson - 1+
IanAG - 2
Hacker - 1
John.luckins - 2
cromodora - 1
rdg - 2
S-Man/Dave - 2
Chiily - 1
peperoni - 2
Agisthos - 2
new naim boy/Aidan - 1
Chrisallen - 1 - quotes? #75/76
Anderzander - 1 - pcb contact #64
VTA/Adam - 2
RichardH - 1
Jonnoshore/John/Me - 2
Muzzer - 1
Markt - 2
35
Other people who posted on this thread
and may be interested?
Paul Ranson
Lilolee - Lee
Paul L
Martin Clark
peranders
Jeff D
Trancera
Mr Tibbs
almichie
Andy W?
***