DIY: Pass F5 turbo v2 initiated

[captrajesh]

Gain of this amp is slightly less and no problem with CDP and tuner. But CNC phono was struggled. Even 100% volume could neither saturate speakers nor made us uncomfortable.

You may like to add SSP in the chain with some high quality Opamps like OPA627.

After reading Om's post I wanted to suggested to use SSP but Sachin beat me to it. And yes, Op amp makes a lot of difference. I was not very impressed with the SSP with the Op amp that came with the original kit but the other day, I heard the SSP of Murali_n (which has 49990) mated to my Class D Power amp and the combo sounded wonderful. When the same Class D was mated to the B1, the SQ was pretty ordinary.

 

[sann]

Thanks Santy. yes, it is running fairly cool in a room with no fan and closed windows.

 

[omishra]

CNC gain is as good as or higher than other Phonostages only Rod Elliot P06 has little more gain than CNC.You may like to add SSP in the chain with some high quality Opamps like OPA627.

Sachin, I agree that CNC has sufficient gain. But F5t needs 1.5 times more input that normal. That's my guess. Because with other amps at 9'O position CDP is more than average for me and for CNC its 10'O position. With F5t it was 10 and 12+ positions.
So adding extra SSP at the output of CNC will do. Have extra PCB?

 

[omishra]

Om and Sann
Congratulations for building a solid F5. :clapping:

Is the amp running fairly cool on continuous operation?
I am wondering if a 4 ohm load will make it hotter.
I tested a pair of 4 ohm speakers on my integrated, the heat was not significantly higher, may be 10% more.

Santy, thanks. Yes we backtracked from the position where 10sec hand test was about to be failed. Its in mode where you can keep your hand for >10sec time. I kept it on since morning 6:30AM till 11:30AM in top lid closed in place and it was stable with bias current 0.55A/device (270mV across source resistors) and output DC offset 5-6mV. This was with windows closed and no ceiling fan. Ventilation makes it cooler.

 

[cmsajith]

Sachin, I agree that CNC has sufficient gain. But F5t needs 1.5 times more input that normal. That's my guess. Because with other amps at 9'O position CDP is more than average for me and for CNC its 10'O position. With F5t it was 10 and 12+ positions.
So adding extra SSP at the output of CNC will do. Have extra PCB?

Any idea what is the i/p sensitivity and gain of the F5T?

 

[sachu888]

Have extra PCB?

Yes I have few.This time I will complete mine,promise

Regards,
Sachin

 

[omishra]

Any idea what is the i/p sensitivity and gain of the F5T?

Cmsajith, F 5 has gain of 15dB while F5 turbo has gain of 22 dB. How much it translates to max input for max voltage swing I don't know.

 

[sachu888]

Cmsajith, F 5 has gain of 15dB while F5 turbo has gain of 22 dB. How much it translates to max input for max voltage swing I don't know.

duplicate post
Regards,
Sachin

 

[sann]

I wanted to listen to a lot of vinyls today, however I am still listening to FM which I had put on when I came back home, that too dedicatedly since last couple of hours, F5t is sounding that good.
Switched between class A/B and class A amp a couple of times to understand the traits of them, and the following comes to my mind if I think of them:
Class A is like a military parade whereas class A/B is like a procession.
Regards, sann

 

[anilva]

Santy, thanks. Yes we backtracked from the position where 10sec hand test was about to be failed. Its in mode where you can keep your hand for >10sec time. I kept it on since morning 6:30AM till 11:30AM in top lid closed in place and it was stable with bias current 0.55A/device (270mV across source resistors) and output DC offset 5-6mV. This was with windows closed and no ceiling fan. Ventilation makes it cooler.

Om, while the build is beautifully done, what this means is that the heatsink is not sufficient for running the F5t V2 at it's intended full bias. You are running lower bias at 270mV as compared to near 400mV bias that this design is intended for. This means transition from Class A to Class AB happens earlier than it's original intended point.

In my case, the V2 runs at full bias of 390mV but in a similar cabinet with similar heatsinks V3 is not running beyond 200mV and I am running a special fan design on top of the heatsinks to make it at 400mV.

Kudos for a fantastic build.

Cheers.

 

[captrajesh]

Class A is like a military parade whereas class A/B is like a procession.

I really like your description.:clapping:

 

[omishra]

Class A is like a military parade whereas class A/B is like a procession.

LOL

Om, while the build is beautifully done, what this means is that the heatsink is not sufficient for running the F5t V2 at it's intended full bias. You are running lower bias at 270mV as compared to near 400mV bias that this design is intended for. This means transition from Class A to Class AB happens earlier than it's original intended point.

In my case, the V2 runs at full bias of 390mV but in a similar cabinet with similar heatsinks V3 is not running beyond 200mV and I am running a special fan design on top of the heatsinks to make it at 400mV.

Kudos for a fantastic build.

Cheers.

Anil, thanks. Yes these heatsinks have max limit of 300mV for ventilated place. I backtracked for safety purpose and looking ahead for summer days. Still after 1-2 weeks I will look into it again. Letting that silpad to settle. I think in place of 6", if we take 8" piece of same heatsink then it should do complete bias. Still 33W per rail/ch is limit for moving into class AB.

 

[pdhanwada]

Hello

After long wait I start soldering on the pcb boards.

I made a mistake of soldering 47.5 R in 47.5K resistor place. I manage to pull out the 47.5R resistor from the board but now the hole is sealed with the solder.

Suggest me good solder sucker which I can use to pull the solder out.

Thanks
Pandu

 

[pdhanwada]

Few ideas I have thought of

Because of the hole size I guess we are limited in options.

1. Using a solder sucker.

2. Melting it from one side and pushing the new resistor from the other side. I am not sure if this works.

3. Braids may not work because it is a 3mm board.

4. Drill bits are proposed on the net but I am sure it may not work here because of the size of the hole.

Thanks
Pandu

 

[anilva]

Few ideas I have thought of

Because of the hole size I guess we are limited in options.

1. Using a solder sucker.

2. Melting it from one side and pushing the new resistor from the other side. I am not sure if this works.

3. Braids may not work because it is a 3mm board.

4. Drill bits are proposed on the net but I am sure it may not work here because of the size of the hole.

Thanks
Pandu

Heat with soldering iron and blow strongly into the hole from the other side to open the hole.

 

[pdhanwada]

I went to a mobile repairing shop near my house and got the solder removed from the holes.

He used solder wick to pull out the solder.

 

[kroyin]

I was talking to Bhaskar and he is having the same issue with Phono not putting out enough voltage to drive the F5T loud enough (guess his spks will be 85-87 dB efficient) .

So you vinyl lovers with average efficiency spks should look at a discreet preamp with gainlike the BOZ or the Juma preamp for F5.

Just an idea

 

[omishra]

I was talking to Bhaskar and he is having the same issue with Phono not putting out enough voltage to drive the F5T loud enough (guess his spks will be 85-87 dB efficient) .

So you vinyl lovers with average efficiency spks should look at a discreet preamp with gainlike the BOZ or the Juma preamp for F5.

Just an idea

Pearl2 is already in process . I should come after my F5t. now just looking at PCB and parts availability.

 

[bhaskarcan]

Hi all,

With lots of spoon-feeding from FM Kroyin & Om finally completed my F5T V2 built & managed to run it successfully. The cabinet & heat-sink is same as Kroyin, so obviously the look is also same. Presently running at 300mV Bias / ~3mv offset. Heatsink is reasonably cool, no problem touching at all. Here are some pics. Will arrange the wire mess B4 final box-up.

Sound wise I must say that the clarity is never heard B4. Gain/Bass was weak initially due to CNC output problem as mentioned by OM previously. So added SSP and now bass is good enough as per my liking(kindly remember that my ears are used to the very bass heavy sound of Sansui AU-719, which will take little time to wear off). Slowly it's opening up nicely(almost 20 hrs running time till now). What is worth mentioning that at a medium to low volume the reproduction is excellent. Let's hope it gets better & better as time passes.

Finally thanks again to all forum members who made this GB/built a great success with obvious special mention of Om, Sachin & Krishnendu(Kroyin).

Best regards,

Bhaskar

 

[pdhanwada]

After long gap closing on completion.

Boards populated.

Need to do wiring.

How important is to clean the excess flux after the soldering is done. Is it ok to leave it on the board. What is the negative side of it functionally.

Thanks