This is my first post on this forum, so I firstly would like to say thanks to out landlords and to the people willing to share their wisdom here.
I designed a pcb for the original Thorsten Loesch's Gainclone circuit with ExpressPCB and I'd like to share it with everybody interested. I'm not an electronics engineer so I don't know how bad my design is
. Any advice or suggestion is very very welcome.
The inspiration for my pcb comes from another post on diyaudio showing a mono power amplifier without volume control, built around a cheap Hammond (?) aluminium enclosure. The pcb doesn't need to be bolted to the enclosure, since the LM 3875, the input and the output connectors should keep it in place.
A few details:
- the .1" traces should be thick enough to allow 4 Amps;
- the placement of the input and output pads is provisional and it should be updated, depending on the choice of connectors available;
- I privileged the placement of the feedback resistor (R3) and of the 1uF decoupling cap (C5) over the placement of the reservoir capacitors (C3/C4), that are a bit far from the chip;
- I assume the resistors are BC 0.6W (like the ones sold by Digikey) except for R5, that should be a 3W (bigger) resistor; Eventually, on the pcb there's place to lay 4-5 BC resistors
in parallel;
- R3 is soldered between the "legs" of the LM3875;
- the 1uF capacitor (C5) could not fit the little space available on the pcb; in this case a smaller (.1uF ?) cap should be used;
- the reservoir caps are Panasonic FA/FC 2200uF, 50V;
- the "-G+" yellow box is a Weidmuller 3 poles connector (code 176050);
- R1 is a Bourns cermet trimmer;
- There is a naive attempt to star ground the circuit.
The Panasonic caps, the Weidmuller comnnector and the Bourns trimmer are sold by Digikey in Usa and by RS-components in Europe.
Thanks very much for your comments. I'll post the ExpressPCB and postscript files as soon as I'll have a decent version of this pcb. If anyone is interested in the current version of these files, please let me know.
Ciao,
Massimo
I designed a pcb for the original Thorsten Loesch's Gainclone circuit with ExpressPCB and I'd like to share it with everybody interested. I'm not an electronics engineer so I don't know how bad my design is
. Any advice or suggestion is very very welcome.The inspiration for my pcb comes from another post on diyaudio showing a mono power amplifier without volume control, built around a cheap Hammond (?) aluminium enclosure. The pcb doesn't need to be bolted to the enclosure, since the LM 3875, the input and the output connectors should keep it in place.
A few details:
- the .1" traces should be thick enough to allow 4 Amps;
- the placement of the input and output pads is provisional and it should be updated, depending on the choice of connectors available;
- I privileged the placement of the feedback resistor (R3) and of the 1uF decoupling cap (C5) over the placement of the reservoir capacitors (C3/C4), that are a bit far from the chip;
- I assume the resistors are BC 0.6W (like the ones sold by Digikey) except for R5, that should be a 3W (bigger) resistor; Eventually, on the pcb there's place to lay 4-5 BC resistors
in parallel;
- R3 is soldered between the "legs" of the LM3875;
- the 1uF capacitor (C5) could not fit the little space available on the pcb; in this case a smaller (.1uF ?) cap should be used;
- the reservoir caps are Panasonic FA/FC 2200uF, 50V;
- the "-G+" yellow box is a Weidmuller 3 poles connector (code 176050);
- R1 is a Bourns cermet trimmer;
- There is a naive attempt to star ground the circuit
.The Panasonic caps, the Weidmuller comnnector and the Bourns trimmer are sold by Digikey in Usa and by RS-components in Europe.
Thanks very much for your comments. I'll post the ExpressPCB and postscript files as soon as I'll have a decent version of this pcb. If anyone is interested in the current version of these files, please let me know.
Ciao,
Massimo
Attachments
PerAnders,
Thanks very much for your positive comments. I'm very happy to hear than I can start my project with some confidence...
Thanks a lot!
Erik (and the others who requested the pcb files),
I'm sorry I cannot help very much with the Tube-GC pcb. Nevertheless, you may find the pcb source files as an attachment; you (or someone else) could maybe spend some time on them to add the tube buffer...
You may freely download the program for modifying the pcb here:
www.expresspcb.com
The program is a pleasure to use and very easy to learn.
For the press-and-peelers, you may find enclosed a Postscript and Pdf version of the pcb as well.
Any comment and feedback is very welcome.
Ciao and happy gaincloning,
Massimo
Thanks very much for your positive comments. I'm very happy to hear than I can start my project with some confidence...
Thanks a lot!
Erik (and the others who requested the pcb files),
I'm sorry I cannot help very much with the Tube-GC pcb. Nevertheless, you may find the pcb source files as an attachment; you (or someone else) could maybe spend some time on them to add the tube buffer...
You may freely download the program for modifying the pcb here:
www.expresspcb.com
The program is a pleasure to use and very easy to learn.
For the press-and-peelers, you may find enclosed a Postscript and Pdf version of the pcb as well.
Any comment and feedback is very welcome.
Ciao and happy gaincloning,
Massimo
Since I'm a new user, my messages get quarantined and appear only after a few hours. Please note I'm not complaining about the diyaudio policy... 
Moreover, my attachment got lost in the hyperspace. It was certainly my fault. Hope you may find this one.
PerAnders
Stupid question: would you like to use the fourth pole to improve the contact of the two ground lines from the rectifiers or to connect the speaker ground?
Speaker: my initial idea for the pcb was to solder or to bolt some kind of speaker connector (e.g. Neutrik Speakon) more or less directly to the pcb. Using binding posts and accepting some asymmetry on the rear panel, the speaker gound could be made very short.
Ciao and thanks once again,
Massimo
Moreover, my attachment got lost in the hyperspace. It was certainly my fault. Hope you may find this one.PerAnders
Stupid question: would you like to use the fourth pole to improve the contact of the two ground lines from the rectifiers or to connect the speaker ground?
Speaker: my initial idea for the pcb was to solder or to bolt some kind of speaker connector (e.g. Neutrik Speakon) more or less directly to the pcb. Using binding posts and accepting some asymmetry on the rear panel, the speaker gound could be made very short.
Ciao and thanks once again,
Massimo
Hi Massimo,
I haven't had a chance to go over it and check every detail as I have a visitor at present. However, it is very neat and compact, you have kept connections as short as possible and I can't see any reason why it should not work well.
And it's a good idea to leave space for any of the 'extra' components that may be needed later.
One size fits all?
Hi everybody and thanks for your attention. Following many discussions by email and in another thread about coupling caps (thanks very much, gentlemen!), I updated the Gainclone pcb. The new pcb is a bit taller than the old one (2.8x1.5 instead of 2.8x1.4) and should fit various decent-sounding components, as described below. Hope that Gainclone tweakers might
find this pcb useful.
R1
It can be a Bourns 3296W series trimmer (RS, Digikey), a potentiometer (wired someway to the pcb) or a simple resistor (like R2, see below) if you want to build a power amp. In the latter case you will have to solder a wire bridge between In and C1 (i.e. the big yellow line on the pcb).
R2-R3-R4
Beyschlag/BC MBB0207 .6W resistors (Digikey). Since the resistor pads are .4 (10,16mm) far apart, the pcb should also fit Welwyn RC55 (RS, Farnell) and Vishay-Dale RN55, but not the RN60.
R5
Caddock MP915 0.2R (RS) or any other resistor with lead spacing not greater than 12 mm (i.e. an ordinary resistor with an inductor wound on it). Suggestions are very welcome.
C1
Every capacitor with maximum size 31,5x18mm and
- 15, 20 or 22.5 mm lead spacing with 0.8mm lead diameter, or
- 27.5 mm lead spacing with 1mm lead diameter.
See attached Excel file CAPS_allowed.xls for a list of capacitors.
C2
Many capacitors with 5, 7.5 or 10mm lead spacing.
C3-C4
Panasonic FA and FC from 1000 to 2200uF (RS and Digikey have all, Farnell has some).
C5
Epcos MKT B32560J1105K 1uF 100V (7.5mm lead sp.) polyethylene stacked cap, recommended by Thorsten Loesch. RS product code: 191-3452, Farnell product code: 545-934.
This nicely priced cap (about .6 Euro) should be available from Newark or somewhere else in the Americas.
Power supply connector
Weidmuller 1760500000. RS product code 408-7887; Digikey product code 1760500000-ND.
Input and Output pads
Placement is still provisional and depending on the actual connectors and enclosure.
Disclaimer
This pcb is fully UNtested; please check (at least on a paper print) if your components fit before using the pcb. This implementation could be prone to oscillation, noise or other problems. I'll post further information as soon as I'll implement the amp.
Ciao,
Massimo
Hi everybody and thanks for your attention. Following many discussions by email and in another thread about coupling caps (thanks very much, gentlemen!), I updated the Gainclone pcb. The new pcb is a bit taller than the old one (2.8x1.5 instead of 2.8x1.4) and should fit various decent-sounding components, as described below. Hope that Gainclone tweakers might
find this pcb useful.
R1
It can be a Bourns 3296W series trimmer (RS, Digikey), a potentiometer (wired someway to the pcb) or a simple resistor (like R2, see below) if you want to build a power amp. In the latter case you will have to solder a wire bridge between In and C1 (i.e. the big yellow line on the pcb).
R2-R3-R4
Beyschlag/BC MBB0207 .6W resistors (Digikey). Since the resistor pads are .4 (10,16mm) far apart, the pcb should also fit Welwyn RC55 (RS, Farnell) and Vishay-Dale RN55, but not the RN60.
R5
Caddock MP915 0.2R (RS) or any other resistor with lead spacing not greater than 12 mm (i.e. an ordinary resistor with an inductor wound on it). Suggestions are very welcome.
C1
Every capacitor with maximum size 31,5x18mm and
- 15, 20 or 22.5 mm lead spacing with 0.8mm lead diameter, or
- 27.5 mm lead spacing with 1mm lead diameter.
See attached Excel file CAPS_allowed.xls for a list of capacitors.
C2
Many capacitors with 5, 7.5 or 10mm lead spacing.
C3-C4
Panasonic FA and FC from 1000 to 2200uF (RS and Digikey have all, Farnell has some).
C5
Epcos MKT B32560J1105K 1uF 100V (7.5mm lead sp.) polyethylene stacked cap, recommended by Thorsten Loesch. RS product code: 191-3452, Farnell product code: 545-934.
This nicely priced cap (about .6 Euro) should be available from Newark or somewhere else in the Americas.
Power supply connector
Weidmuller 1760500000. RS product code 408-7887; Digikey product code 1760500000-ND.
Input and Output pads
Placement is still provisional and depending on the actual connectors and enclosure.
Disclaimer
This pcb is fully UNtested; please check (at least on a paper print) if your components fit before using the pcb. This implementation could be prone to oscillation, noise or other problems. I'll post further information as soon as I'll implement the amp.
Ciao,
Massimo
Gain/Zin spreadsheet
Hi everybody!
Trying to understand the relationship between resistor values, gain and input impedance, i wrote this spreadsheet. I'd like to say thanks to Joe Rasmussen for the relevant information shared on diyaudio. Humblest apologies if I misunderstood his writings and/or the spreadsheet contains some nasty (or evident
) mistake...
Btw, is there anybody trying to use this pcb? In case I'd be very happy to know and to drink together a "virtual beer"!
Ciao,
Massimo
Hi everybody!
Trying to understand the relationship between resistor values, gain and input impedance, i wrote this spreadsheet. I'd like to say thanks to Joe Rasmussen for the relevant information shared on diyaudio. Humblest apologies if I misunderstood his writings and/or the spreadsheet contains some nasty (or evident
) mistake... Btw, is there anybody trying to use this pcb? In case I'd be very happy to know and to drink together a "virtual beer"!
Ciao,
Massimo
RS/Farnell part list
Hi everybody!
On the weekend I compiled a part list (electronics only) for my Gainclone. I intentionally concentrated on RS and Farnell mostly because they stock all the needed electronics parts, so there should not need to purchase parts from 2-3 resellers. In addition, they both sell Panasonic, Siemens/Epcos and Welwyn parts, so, according to various diyaudio fellows, the resulting circuit should sound decently. Please note that prices are based on the italian catalog and could slightly differ in other countries (they should probably be better ).
Among the general-purpose resellers, another interesting brand is www.distrelec.com; they carry Beyschlag MB0207 resistors (.07 Eur each in multiples of 10, code 714000 and following) and cheap toroidal transformers, but - maybe - wouldn't sell them all over the Europe (maybe not...).
I apologize with the american readers for not being of help at all.
Ciao,
Massimo
Hi everybody!
On the weekend I compiled a part list (electronics only) for my Gainclone. I intentionally concentrated on RS and Farnell mostly because they stock all the needed electronics parts, so there should not need to purchase parts from 2-3 resellers. In addition, they both sell Panasonic, Siemens/Epcos and Welwyn parts, so, according to various diyaudio fellows, the resulting circuit should sound decently. Please note that prices are based on the italian catalog and could slightly differ in other countries (they should probably be better
).Among the general-purpose resellers, another interesting brand is www.distrelec.com; they carry Beyschlag MB0207 resistors (.07 Eur each in multiples of 10, code 714000 and following) and cheap toroidal transformers, but - maybe - wouldn't sell them all over the Europe (maybe not...).
I apologize with the american readers for not being of help at all.
Ciao,
Massimo
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