Air guitar Pre
- Thread starter sandford
- Start date
S-Man
StrivingON
Sandford, I am interested in a couple of boards.
Questions:
Does one board contain 2 channels?
Does each channel include the layout for the time aligned buffer and the output/gain stage (volume pot is wired off board between these 2 circuits)?
Single or double sided pcb?
I assume there are no power supply components, except decoupling caps, on the pcb.
Cost appears to be about £10 per board + P and P.
Thanks,
Dave
Questions:
Does one board contain 2 channels?
Does each channel include the layout for the time aligned buffer and the output/gain stage (volume pot is wired off board between these 2 circuits)?
Single or double sided pcb?
I assume there are no power supply components, except decoupling caps, on the pcb.
Cost appears to be about £10 per board + P and P.
Thanks,
Dave
S-Man
In responce to your questions
Two Channels: Yes
TA Buffer: Only the mother board with TA curcuit Air guitar dose not
Single sided PCB: yes
Price as stated before depends on quantity but will confirm once order is placed.
Have alook at the www.acoustica.org.uk the artwork is there under naim pre mods bible.
Matt
In responce to your questions
Two Channels: Yes
TA Buffer: Only the mother board with TA curcuit Air guitar dose not
Single sided PCB: yes
Price as stated before depends on quantity but will confirm once order is placed.
Have alook at the www.acoustica.org.uk the artwork is there under naim pre mods bible.
Matt
Paul R
pfm Member
I have this for the ZTXs,
.MODEL ZTX384C NPN(IS=1.8E-14 ISE=5.0E-14 NF=.9955 NE=1.46 BF=325 BR=35.5 IKF=.14 IKR=.03 ISC=1.72E-13 NC=1.27 NR=1.005 RB=.56 RE=.6 RC=.25 VAF=80 VAR=12.5 CJE=13E-12 CJC=4E-12 VJC=.54 MJC=.33 TF=.64E-9 TR=50.72E-9 mfg=Zetex)
.MODEL ZTX214 PNP(IS=1.149E-14 ISE=5E-14 NF=.9872 NE=1.4 BF=330 BR=13 IKF=.1 IKR=.012 ISC=1.43E-14 NC=1.1 NR=.996 RB=.2 RE=.4 RC=.95 VAR=8.15 VAF=84.56 CJE=16E-12 TF=.493E-9 CJC=10.5E-12 TR=73.55E-9 MJC=.415 VJC=.565 mfg=Zetex)
but I don't know where they came from. Or whether they're any good...
Paul
Paul R
pfm Member
Sandford,
I favour the AGP too. But the layout commits one to some expensive, hard-to-get and perhaps over specified caps in particular, and a couple of spots could do with re alignment. so I have gone quiet for the moment.
It would be no big deal to add some pads for alternative caps and straighten things out, but beyond me at the moment.
I think it is a great board. Apart from star earthing and star +ve distribution, outout and input signals are separated and the feedback current can return to the transistors generating it without interfering with other parts of the circuit.
I havn't looked at the buffer-gain board design at all. Looking at the buffer schematic I see no frequency shaping going on. I am using only the gain boards in my Preamp and it was an improvement in clarity when I bypassed the buffer boards. I think the buffer board is protection against a source with poor current drive, but phono boards and CD players are quite capable of driving the volume control/gain board.
I also see the AGP with a daughter board for the front end as making a good NA323 upgrade. The feedback cap could be accomodated in a redraft, or mounted on top of the feedback resistor, using PCB pins.
Power to you
David
I favour the AGP too. But the layout commits one to some expensive, hard-to-get and perhaps over specified caps in particular, and a couple of spots could do with re alignment. so I have gone quiet for the moment.
It would be no big deal to add some pads for alternative caps and straighten things out, but beyond me at the moment.
I think it is a great board. Apart from star earthing and star +ve distribution, outout and input signals are separated and the feedback current can return to the transistors generating it without interfering with other parts of the circuit.
I havn't looked at the buffer-gain board design at all. Looking at the buffer schematic I see no frequency shaping going on. I am using only the gain boards in my Preamp and it was an improvement in clarity when I bypassed the buffer boards. I think the buffer board is protection against a source with poor current drive, but phono boards and CD players are quite capable of driving the volume control/gain board.
I also see the AGP with a daughter board for the front end as making a good NA323 upgrade. The feedback cap could be accomodated in a redraft, or mounted on top of the feedback resistor, using PCB pins.
Power to you
David
C
ced
Guest
Hello gents,
had a quick gander back over PF in spare moment so thought i'd jump in with some observations. Pleased you're all taking this in the spirit of diy and piddling with the designs. Impressed with the pro board orders too. In response, no, no cad artwork. Did it all in illustrator as I etched diy boards.
Sadly am in Australia and working way too hard so can't afford time to get involved much though would like to.
OK some points. I'd try the air pre if I were you first for several reasons. Its simpler and cheaper to build, and I belive it to be a better pre. Note: The external psu is integral to the design , its really a pre system, and utilises the Mr tibbs grounding mod which is a musical biggy. In context the board layout gives you in the region of half to a third of the gains of the mr tibbs mod. If you see one of the other threads recently, there are no time aligned buffers as the gains of using seperate psu channels for each gain stage only outweigh the gains using time align board by a long way when I tried it. Otherwise you have 2 psu channels powering 2 gain and 2 time align boards and I belive there is considerable grunge fed back by the superregs- whatever. also you only have 2 coupling caps in the signal path and SMRs are do-able in this context. As many have noticed 4 smrs in the signal path is somewhat 'intense'. Saying that please redesign for different sized coupling caps- all you need to do is extend the tracks to within about 3 mm of each other and then the end user can drill for his own desired coupling caps.
The mother board was designed to mount 6 superregs UNDER the board on the base of a 32.5 chassis. It was measured so that there is just enough space to fit the superregs in if you mount the pass transistor and prereg of the superegs flat and heatsink to the chassis and use something like 10mm standoff for the mother board. Can't remember exact figures but that was the design idea as my pre was an exploding mess of wires and caps what with 6 superregs and big caps and all. Anyway then I went further and took the guitar-iste route so really posted the mother board as a way station idea. spent bloody hours making sure it would fit in the case of a 32.5 though. If you redesign, please bear this in mind.
I did actually update the air guitar-iste notes and stuff but never got round to sending them to martin what with moving etc. Martin if you want to update, I can send you the revised files.
As per martins advice, I would avoid designing dins, pots etc to be board mounted. Great if youre a manufacturer but severely limits the diyer in the long run. You WILL want to start fiddling with differen pots cabling etc, as we all know.
To be honest, you can do the whole air guitariste mods lot without using a new pcb. Probably daft to suggest but why not buy the parts, mod your pre and then if you like it, do the pcb and get that final little extra. Actually naah.
But I can confirm layout does have a significant and very nice (purely musical) effect on sound.
More on input caps; Really DO fiddle with these to your taste. They are a total swine to get right and I totally recommend mixing and matching. Even the standard SMR-ed up air-g may be a bit revealing of high freqencies if you haven't got a maxed out Martin Clark acoustica cd3.5 at least. Get it right and its magic though.
Oh, one teccy thing: you'll have to check the diodes on the output relay. Also, if you use the lm317 reg to feed the relay instead of tapping a superreg, check the current draw is sufficient to get the lm317 working. may need to put something like a 2K resistor from output to ground to ensure a nice 10-12 ma minimum load current. Personally I just tap a superreg output- never heard no difference myself.
Anyway, I left my system with my dear old mum as shes quite into classical and none of my mates are responisble enough. I belive she had rather a big grin when I left her rocking away infront of the speakers.
cheers
C
had a quick gander back over PF in spare moment so thought i'd jump in with some observations. Pleased you're all taking this in the spirit of diy and piddling with the designs. Impressed with the pro board orders too. In response, no, no cad artwork. Did it all in illustrator as I etched diy boards.
Sadly am in Australia and working way too hard so can't afford time to get involved much though would like to.
OK some points. I'd try the air pre if I were you first for several reasons. Its simpler and cheaper to build, and I belive it to be a better pre. Note: The external psu is integral to the design , its really a pre system, and utilises the Mr tibbs grounding mod which is a musical biggy. In context the board layout gives you in the region of half to a third of the gains of the mr tibbs mod. If you see one of the other threads recently, there are no time aligned buffers as the gains of using seperate psu channels for each gain stage only outweigh the gains using time align board by a long way when I tried it. Otherwise you have 2 psu channels powering 2 gain and 2 time align boards and I belive there is considerable grunge fed back by the superregs- whatever. also you only have 2 coupling caps in the signal path and SMRs are do-able in this context. As many have noticed 4 smrs in the signal path is somewhat 'intense'. Saying that please redesign for different sized coupling caps- all you need to do is extend the tracks to within about 3 mm of each other and then the end user can drill for his own desired coupling caps.
The mother board was designed to mount 6 superregs UNDER the board on the base of a 32.5 chassis. It was measured so that there is just enough space to fit the superregs in if you mount the pass transistor and prereg of the superegs flat and heatsink to the chassis and use something like 10mm standoff for the mother board. Can't remember exact figures but that was the design idea as my pre was an exploding mess of wires and caps what with 6 superregs and big caps and all. Anyway then I went further and took the guitar-iste route so really posted the mother board as a way station idea. spent bloody hours making sure it would fit in the case of a 32.5 though. If you redesign, please bear this in mind.
I did actually update the air guitar-iste notes and stuff but never got round to sending them to martin what with moving etc. Martin if you want to update, I can send you the revised files.
As per martins advice, I would avoid designing dins, pots etc to be board mounted. Great if youre a manufacturer but severely limits the diyer in the long run. You WILL want to start fiddling with differen pots cabling etc, as we all know.
To be honest, you can do the whole air guitariste mods lot without using a new pcb. Probably daft to suggest but why not buy the parts, mod your pre and then if you like it, do the pcb and get that final little extra. Actually naah.
But I can confirm layout does have a significant and very nice (purely musical) effect on sound.
More on input caps; Really DO fiddle with these to your taste. They are a total swine to get right and I totally recommend mixing and matching. Even the standard SMR-ed up air-g may be a bit revealing of high freqencies if you haven't got a maxed out Martin Clark acoustica cd3.5 at least. Get it right and its magic though.
Oh, one teccy thing: you'll have to check the diodes on the output relay. Also, if you use the lm317 reg to feed the relay instead of tapping a superreg, check the current draw is sufficient to get the lm317 working. may need to put something like a 2K resistor from output to ground to ensure a nice 10-12 ma minimum load current. Personally I just tap a superreg output- never heard no difference myself.
Anyway, I left my system with my dear old mum as shes quite into classical and none of my mates are responisble enough. I belive she had rather a big grin when I left her rocking away infront of the speakers.
cheers
C
martin clark
pinko bodger
Great to hear from you Ced, yes please to the update when time allows.
martinclark AT stridetreglown DOT co DOT uk
new naim boy
pfm Member
I've only just read this thread and wondered if these pcb's have been ordered. If so can I order one also?
Aidan
Aidan