TG1 - advice from any one who has built it...
- Thread starter mathsieve
- Start date
Help Support GroupDIY Audio Forum:
Hi
My build with Modern kit from Frank, (1N751A,BC184C,BC214)
Im use 21step switch for Hold
Now i'm try to understand how calibrate Hold
Do you have same value for AOTs on two boards?
on my board AOT1 have difference 100ohm(330 and 430ohm) it ok?
My build with Modern kit from Frank, (1N751A,BC184C,BC214)
Im use 21step switch for Hold
Now i'm try to understand how calibrate Hold
Do you have same value for AOTs on two boards?
on my board AOT1 have difference 100ohm(330 and 430ohm) it ok?
desol
Well-known member
- Joined
- Jun 20, 2005
- Messages
- 2,184
But, I'm assuming your supposed to do the actual AOT procedure...rather than just using given values. Wouldn't the values change with different component choices?
I like that you used original components. Nice. I have original HS2051's, etc as well. I'd like to acquire the transistors tho...and the odd value capacitors. I really have to get on this build...it's been sitting a long time.
I like that you used original components. Nice. I have original HS2051's, etc as well. I'd like to acquire the transistors tho...and the odd value capacitors. I really have to get on this build...it's been sitting a long time.
This is the setup procedure I came up with by reading festers instruction and studying the schematic.
Set up procedure.
1. Make sure you have +28Vdc and -28Vdc on the power supply PCB.
2. Set the +20Vdc on test point TP+20 by adding in resistors on JP1, JP2 and JP3 as required.
3. Set the -20Vdc on test point TP-20 by adding in resistors on JP4, JP5 and JP6 as required.
4. Install resistor in AOT10 so that the dc voltage on the collector of VT5 and VT6 are the same.
5. Set unity gain. Set HOLD and OUTPUT to 0 and switch the compressor side chain out by selecting THD. If you have the correct 2.5mA FS meter it should read zero, if not adjust the 100K trim pot until it does. Apply 0dBu (0.775V) 1KHz sine wave to input and measure the output on a oscilloscope or DMM. You need to adjust AOT1/AOT2 so that you get 0.775V at the output.
6. Set distortion without compression. Set HOLD to +10, OUTPUT to 0 and switch the compressor side chain out by selecting THD. If you have the correct 2.5mA FS meter it should read +10. Apply 0dBu (0.775V) 1KHz sine wave to input and measure the output on a distortion meter and select a resistance for AOT7/AOT9 that gives you the lowest distortion reading.
7. Set distortion with 20dB of compression. Set HOLD to +10, OUTPUT to 0 and switch the compressor side chain in by selecting LIMIT. If you have the correct 2.5mA FS meter it should read +10. Apply 1KHz sine wave to input and increase the voltage so that you have 20dB of gain reduction as indicated on the meter. If you have the correct 2.5mA FS meter it should read -10. Measure the output on a distortion meter and select a resistance for AOT8 that gives you the lowest distortion reading.
8. AOT3/AOT4 adjusts the compressor threshold. This is a matter of taste. I left mine standard.
9. AOT5/AOT6 adjusts the limiter threshold. This is a matter of taste. I set my unit to limit harder by changing the resistors to suit.
If you don’t have a distortion meter (like me) use the standard values. When I set my TG12413 up I did so with the bypass PCB disconnected. That way the test signal is going straight into and out of the compressor without being boosted or attenuated the OP amps or transformers.
Here are the values I used.
AOT1 620r (Unity Gain)
AOT2 not used
AOT3 47K (Compressor Threshold standard value)
AOT4 (Compressor Threshold not used)
AOT5 3K (Limiter Threshold standard value)
AOT6 510r (Limiter Threshold, make the unit limit more in limit mode)
AOT7 33K (Distortion without compression, standard value)
AOT8 68K (Distortion without compression, standard value)
AOT9 (Not Used)
AOT10 10r (DC voltage on the collector of VT5 and VT6 are the same)
I have also attached the procedure as a pdf.
Regards,
Brezo
Set up procedure.
1. Make sure you have +28Vdc and -28Vdc on the power supply PCB.
2. Set the +20Vdc on test point TP+20 by adding in resistors on JP1, JP2 and JP3 as required.
3. Set the -20Vdc on test point TP-20 by adding in resistors on JP4, JP5 and JP6 as required.
4. Install resistor in AOT10 so that the dc voltage on the collector of VT5 and VT6 are the same.
5. Set unity gain. Set HOLD and OUTPUT to 0 and switch the compressor side chain out by selecting THD. If you have the correct 2.5mA FS meter it should read zero, if not adjust the 100K trim pot until it does. Apply 0dBu (0.775V) 1KHz sine wave to input and measure the output on a oscilloscope or DMM. You need to adjust AOT1/AOT2 so that you get 0.775V at the output.
6. Set distortion without compression. Set HOLD to +10, OUTPUT to 0 and switch the compressor side chain out by selecting THD. If you have the correct 2.5mA FS meter it should read +10. Apply 0dBu (0.775V) 1KHz sine wave to input and measure the output on a distortion meter and select a resistance for AOT7/AOT9 that gives you the lowest distortion reading.
7. Set distortion with 20dB of compression. Set HOLD to +10, OUTPUT to 0 and switch the compressor side chain in by selecting LIMIT. If you have the correct 2.5mA FS meter it should read +10. Apply 1KHz sine wave to input and increase the voltage so that you have 20dB of gain reduction as indicated on the meter. If you have the correct 2.5mA FS meter it should read -10. Measure the output on a distortion meter and select a resistance for AOT8 that gives you the lowest distortion reading.
8. AOT3/AOT4 adjusts the compressor threshold. This is a matter of taste. I left mine standard.
9. AOT5/AOT6 adjusts the limiter threshold. This is a matter of taste. I set my unit to limit harder by changing the resistors to suit.
If you don’t have a distortion meter (like me) use the standard values. When I set my TG12413 up I did so with the bypass PCB disconnected. That way the test signal is going straight into and out of the compressor without being boosted or attenuated the OP amps or transformers.
Here are the values I used.
AOT1 620r (Unity Gain)
AOT2 not used
AOT3 47K (Compressor Threshold standard value)
AOT4 (Compressor Threshold not used)
AOT5 3K (Limiter Threshold standard value)
AOT6 510r (Limiter Threshold, make the unit limit more in limit mode)
AOT7 33K (Distortion without compression, standard value)
AOT8 68K (Distortion without compression, standard value)
AOT9 (Not Used)
AOT10 10r (DC voltage on the collector of VT5 and VT6 are the same)
I have also attached the procedure as a pdf.
Regards,
Brezo
Majestic12
Well-known member
SLB said:
What exactly do you mean with "resistors as required" at JP1, JP2 etc. ?
Majestic12 said:
JP1..6 are headers that can be jumped or not. Depending on how many you jump or have open, output voltage changes. So you just get 6 jumpers and put them in one by one, measuring inbetween. When it hits the desired voltage at test point, you win
Please see attached picture for better explanation. This is a simple voltage regulator circuit and by adding resistance in parallel you are controlling the base voltage of the transistor which is part of a voltage divider. Think of it as a variable voltage divider. I'm no expert but thats how I see it.
1. Start with only JP1 and JP5 link in.
2. Make sure you have +28Vdc and -28Vdc on the main power connections.
3. Measure dc voltage on -20V and +20V test points.
4. If voltage is out add another link and check voltage.
5. Repeat process until voltage is close to 20V.
Regards,
Brezo
1. Start with only JP1 and JP5 link in.
2. Make sure you have +28Vdc and -28Vdc on the main power connections.
3. Measure dc voltage on -20V and +20V test points.
4. If voltage is out add another link and check voltage.
5. Repeat process until voltage is close to 20V.
Regards,
Brezo
Attachments
dirty1_1garry
Well-known member
Hello TG's guys!
In the final process of assemble the mother board.
I bought vintage semi kit from Frank that contains BC109 and BCY71. I done a HFE measurements all of them with multimeter.
I know that some of VT's should be paired, so that was my main purpose - find a pairs. But if I know hfe of all VT's may be anyone know some secret:
at what places it could be more suitable to use VT's with less hfe and where with more hfs?!
In the final process of assemble the mother board.
I bought vintage semi kit from Frank that contains BC109 and BCY71. I done a HFE measurements all of them with multimeter.
I know that some of VT's should be paired, so that was my main purpose - find a pairs. But if I know hfe of all VT's may be anyone know some secret:
at what places it could be more suitable to use VT's with less hfe and where with more hfs?!
Attachments
dirty1_1garry
Well-known member
Anybody... anybody?
bruno2000
Well-known member
SLB said:
Nice! Thank you.
Best,
Bruno2000
dirty1_1garry
Well-known member
warpie said:
I heard about this paired VT's:
VT5 - VT6
VT13 - VT14
VT18 - VT19
From Festers build docs.
Original units were transformerless, and used HOLD control (10k lin pot).
Fester's clones can be built either with input pot or hold control.
Actually, HOLD control gives better s/n ratio, less unwanted distortion,
and closer to original units sound.
10k lin potentiometer used in EMI units, gives control range more than 40db.
To get more precision in range of +/-15 db gain,
5k log pot connected in series with 5k resistor can be good option.
To get precision steps, possible to use switch,
however, you'll need to connect 10k pot and measure its value at every step,
because control voltage depends on zener diodes used.
1n751a is very close substitute to HS2051.
Optional 100-200k /HOLD trimer can be installed on front pannel
board to adjust both channels for precision "0" at the same position
of HOLD control. It connected in parallel to HOLD and "shifts" its "center".
I jumped R115 and used a 10K lin pot and it works perfectly.
Regards,
Brezo
Original units were transformerless, and used HOLD control (10k lin pot).
Fester's clones can be built either with input pot or hold control.
Actually, HOLD control gives better s/n ratio, less unwanted distortion,
and closer to original units sound.
10k lin potentiometer used in EMI units, gives control range more than 40db.
To get more precision in range of +/-15 db gain,
5k log pot connected in series with 5k resistor can be good option.
To get precision steps, possible to use switch,
however, you'll need to connect 10k pot and measure its value at every step,
because control voltage depends on zener diodes used.
1n751a is very close substitute to HS2051.
Optional 100-200k /HOLD trimer can be installed on front pannel
board to adjust both channels for precision "0" at the same position
of HOLD control. It connected in parallel to HOLD and "shifts" its "center".
I jumped R115 and used a 10K lin pot and it works perfectly.
Regards,
Brezo
