JAZZ2250 said:I also tried his veriosn with resistors of lower values (two 47k and two 4.7k) which gives lower input impedance. I thought 220k was a little bit high. The result is... very satisfying.
Yes: the 220k after the input is too much. The maximum amplification of my amp is now too low, so I will lower that one too.
The sound:
Much better, definitely. I hear details now which I have never heard before. Strangely, I have more HF output now. Well, I guess oscilation is something you really want to stay at least a couple of blocks away from.
Niels.
Just Built Kuei's version of the inverted...
in one channel of my gainclone. I just used Radio Shack resistors that I had on hand but the hum that bothered me with Thorsten's version is completely gone.
I will write a short review when I have some more time to compare the two.
The only issue I have is that Kuei's version does not reach the sound levels of the other channel. I am using two 47K and two 4.7K resistors.
If I lowered the values even further, lets say two 22K and two 2.2K resistors's, could I get higher sound level's while maintaining stability?
Thanks for all of the information. This little project has turned into a great learning experience.
in one channel of my gainclone. I just used Radio Shack resistors that I had on hand but the hum that bothered me with Thorsten's version is completely gone.
I will write a short review when I have some more time to compare the two.
The only issue I have is that Kuei's version does not reach the sound levels of the other channel. I am using two 47K and two 4.7K resistors.
If I lowered the values even further, lets say two 22K and two 2.2K resistors's, could I get higher sound level's while maintaining stability?
Thanks for all of the information. This little project has turned into a great learning experience.
Re: Just Built Kuei's version of the inverted...
Hi,
Guys, guys. NEVER build slavishly a "gurus" schematic (not even my ones - neither the original inverted gainclone nor the amended one - yes KYW = Thorsten).
The "new" schematic is UNITY GAIN. It means it has NO GAIN. If you want the usual 26db gain of the Gaincard and/or inverted gainclone you need to keep the NFB resistor 220k and the input resistor 10k.
The only change to the original "inverting gainclone" is the added 22k resistor on the inverting input and the removal of the RC combo on the non-inverting input and it's replacement by a 18k resistor.
If the full original "inverted gainclone" the input potentiomenter (if a linear one is used and the source has low impedance) will pretty much make sure the Amp remains stable. It cannot be removed without risking instability, if unconnected the amp is potentially instable. Adding the 22k resistor ensures unconditional stability even with input open.
Sayonara
Hi,
Guys, guys. NEVER build slavishly a "gurus" schematic (not even my ones - neither the original inverted gainclone nor the amended one - yes KYW = Thorsten).
The "new" schematic is UNITY GAIN. It means it has NO GAIN. If you want the usual 26db gain of the Gaincard and/or inverted gainclone you need to keep the NFB resistor 220k and the input resistor 10k.
The only change to the original "inverting gainclone" is the added 22k resistor on the inverting input and the removal of the RC combo on the non-inverting input and it's replacement by a 18k resistor.
If the full original "inverted gainclone" the input potentiomenter (if a linear one is used and the source has low impedance) will pretty much make sure the Amp remains stable. It cannot be removed without risking instability, if unconnected the amp is potentially instable. Adding the 22k resistor ensures unconditional stability even with input open.
Sayonara
Hi, guys. I started this thread wanting to find some way that I could make a gainclone with unity gain. The main purpose of the unity gain is to use the gainclone solely as a power amp without any voltage amplification (and hopefully without colorization, if any). A high quality (well... there is no doubt about the sound quality of gainclone but...) tube amp or soundcard in a PC will be hooked up to this gainclone. So, the low volume level of this guy is already expected. If any of you want a higher volume level, please increase the feedback resistor value as is in Thorsten's schematics.
Good luck.
Good luck.
Hi,
Sorry? This seems not to make sense. The 18k resistor is on the positive input, there is no connection to "feedback".
To repeat, my suggested adjustments to the original "inverted gainclone" are as follows:
On the positive (non inverting) input remove the 220k and 0.1uF and replace it with a 18k Resistor (approximate - tune this resistor to minimise offset).
On the inverting input connect a 22k Resistor to ground.
The input coupling Cap MAY be removed, but I would likely leave it.
BTW, it matters VERY MUCH where the 18k and 22k are connected. Both need to be referenced to the Input ground, not the Amplifier starground IMHO. Failing to do may lead to increased offset or noise.
Sayonara
Sorry? This seems not to make sense. The 18k resistor is on the positive input, there is no connection to "feedback".
To repeat, my suggested adjustments to the original "inverted gainclone" are as follows:
On the positive (non inverting) input remove the 220k and 0.1uF and replace it with a 18k Resistor (approximate - tune this resistor to minimise offset).
On the inverting input connect a 22k Resistor to ground.
The input coupling Cap MAY be removed, but I would likely leave it.
BTW, it matters VERY MUCH where the 18k and 22k are connected. Both need to be referenced to the Input ground, not the Amplifier starground IMHO. Failing to do may lead to increased offset or noise.
Sayonara
Kuei Yang Wang said:
Ok. I thought only the 22 k to ground was the only change. Now I've changed the 220 K to 22 K and offset is good again.
Removing it seems to double the offset. Now with them I have 8 mV on one channel and 5 on the other.
Mmm. Tough subject. As you might see*, I have a star at the amp section. At that point, both input ground and power supply ground meet, so I'm not quite sure how to interpret your saying.
Well, at least now I have enough gain to run AutoQ (since I have the digital add-on).
Thanks, and, in advance.
Niels.
*Behringer 8024 underneath
unity gain Gainclone completed
Thanks, Kuei Yang Wang. I finally completed unity gain Gainclone. Without the input coupling cap, the offset voltage is only a few mVs. I think the input cap is not really necessary. Attached is a closeup of the chip. Now, it's up and playing. BTW, all the grounds are connected at a star ground, and it seems to be okay. Next project will be to find a simple tube preamp to match this amp. Any recommendation?
Jazz2250
Thanks, Kuei Yang Wang. I finally completed unity gain Gainclone. Without the input coupling cap, the offset voltage is only a few mVs. I think the input cap is not really necessary. Attached is a closeup of the chip. Now, it's up and playing. BTW, all the grounds are connected at a star ground, and it seems to be okay. Next project will be to find a simple tube preamp to match this amp. Any recommendation?
Jazz2250
Attachments
Re: No gain, No Pain...
Kuei/Jazz2250:
Wonderful project. I am implementing in a TDA 2030 immediately. One question:
What is the rationale behind selection: How can I calculate resistor values on my own?
I am interested in using 56K resistors, along with suitable grounding resistors for the opamp inputs. According to my crude calculations, the values are coming to 5.6K and 4.7K (ratio of 1:1.2, of 22K and 18K).
What are the implications of using two 5.6K (i.e, equal value for + and - inputs) resistors instead, as you have done? Do you not get any DC offset at output?
JAZZ2250 said:
JAZZ2250 said:I also tried his veriosn with resistors of lower values (two 47k and two 4.7k) which gives lower input impedance. I thought 220k was a little bit high. The result is... very satisfying.
Kuei/Jazz2250:
Wonderful project. I am implementing in a TDA 2030 immediately. One question:
What is the rationale behind selection: How can I calculate resistor values on my own?
I am interested in using 56K resistors, along with suitable grounding resistors for the opamp inputs. According to my crude calculations, the values are coming to 5.6K and 4.7K (ratio of 1:1.2, of 22K and 18K).
What are the implications of using two 5.6K (i.e, equal value for + and - inputs) resistors instead, as you have done? Do you not get any DC offset at output?