Kuartlotron Error Correcting Super Buffer

[jls001]

Saikat: it's looking good. Caps look to be in proper polarity.

Make the flat faces of the transistors Q1 and Q3 touch each other for thermal equilibrium between the two transistors. Ditto for Q2-Q4.

Calibrate the +15/0/-15V DC supplies of the OPS for +10/0/-10V by using the trim pots. Measure and calibrate the voltage +/-10V on the OPS output terminal first without connecting DC supply to buffer board, then followed by measurement on buffer board (under load). If there is voltage drop, calibrate the trim pots again to get +/-10V.

Do follow the adjustment methods mentioned for setting the buffer trim pots by measuring Vbe and Veb of the relevant transistors. Please turn back a few pages on this thread on detailed instructions I had posted.

After you're happy with the voltage on the Test Point which must be exactly half of the input DC voltage (5V), check for DC offsets on the left and right output RCA terminals. Adjust as needed to obtain the least DC offset.

If in doubt, do post.

I would also strongly suggest that you follow the wiring method I had mentioned for signal inputs and outputs, duly isolating left and right return wires right from input to output. Also, I would recommend you to use shielded balanced interconnect wire for internal wiring and follow the shield grounding at "source" ends.

Edit: see posts 168 and 175 for detailed instructions. Thanks.

 

[saikatbiswas82]

Saikat: it's looking good. Caps look to be in proper polarity.

Make the flat faces of the transistors Q1 and Q3 touch each other for thermal equilibrium between the two transistors. Ditto for Q2-Q4.

Calibrate the +15/0/-15V DC supplies of the OPS for +10/0/-10V by using the trim pots. Measure and calibrate the voltage +/-10V on the OPS output terminal first without connecting DC supply to buffer board, then followed by measurement on buffer board (under load). If there is voltage drop, calibrate the trim pots again to get +/-10V.

Do follow the adjustment methods mentioned for setting the buffer trim pots by measuring Vbe and Veb of the relevant transistors. Please turn back a few pages on this thread on detailed instructions I had posted.

After you're happy with the voltage on the Test Point which must be exactly half of the input DC voltage (5V), check for DC offsets on the left and right output RCA terminals. Adjust as needed to obtain the least DC offset.

If in doubt, do post.

I would also strongly suggest that you follow the wiring method I had mentioned for signal inputs and outputs, duly isolating left and right return wires right from input to output. Also, I would recommend you to use shielded balanced interconnect wire for internal wiring and follow the shield grounding at "source" ends.

Thanks a lot @jls001 for your valuable feedback. I will resolder the transistors.

I will go through the whole thread again for your wiring suggestions.

A lot of questions will be coming your way after I receive the trafo.

Wish me luck [emoji4]

 

[jls001]

Please follow grounding schemes too. It will make your buffer more silent, and they're good electrical practices.

 

[saikatbiswas82]

Please follow grounding schemes too. It will make your buffer more silent, and they're good electrical practices.

I will definitely try grounding.

 

[arunlouie]

Now many waiting for comments from manniraj or others who have listened to both DCB1 and Kuartlotron.

 

[manniraj]

Now many waiting for comments from manniraj or others who have listened to both DCB1 and Kuartlotron.

I think you meant BA3 and Kuartlotron which I am yet to hear. Not finding time.

 

[arunlouie]

I think you meant BA3 and Kuartlotron which I am yet to hear. Not finding time.

No I meant DCB1 only, just gone past in this thread and saw you comments. So now will wait for BA3 .

 

[arunlouie]

Last week got the kit from Sachin along with PSU kit. Thank you Sachin and ofcourse Omishra!!

Which one to choose for the transformer, R-core or a toroidal?


One more thing, the PSU is designed to handle multiple pre-amps. Is it OK to house two pre-amps in the same cabinet ( I am looking for a tube based addon in the future). What in mind as of now is to use same PSU with 2 preamps where as power, Inputs and outputs for pre-amps is control by flick of switches.

Anyone tried this before?

 

[jls001]

Depends on how much load the tube add-on will draw. Do you know how much current it is expected to draw? If you know it, then omishra should be able to help us calculate if the OPS will be able to drive both.

BTW, the OPS has two sets of adjustable voltages - one is good for upto dual +/-15V and the other is good for single upto +24/0V.

 

[jls001]

Update: After using the K buffer for many months, I replaced the internal wiring from 20 gauge Teflon shielded solid core to my favourite Helusound AES DMX balanced cable. I managed to over heat the source selector switch, destroying it in the process. Soldering to the pins of such plastic bodied source selector switches (or even plastic bodied DPDT switches) needs extra care not to overheat any pin which can bend the pin internally, jamming the internal mechanism and rendering it useless. Luckily I had bought spares.

 

[arunlouie]

Joshua,
As exactly you said first I have the decide on the power requirement but I have not decided on any specific Tube design yet.

May be someone will come with another DIY gem like B1, DCB1 and this Kuartlotron. Following the fellow masters (members) here is always easy than following the exhaustive diyaudio threads.

 

[jmascreen]

Om/Joshua & others, a quick question. My CA C500 control Amplifer in output stage it says Unity Gain Low Noise output buffer and on Input stage its given as Unity Gain buffer with no components. what are they and is it serving the same purpose as K unity gain?

 

[jls001]

Justin, I'm not too clear about your doubt, but in general a buffer acts as an impedance matching mechanism between a source and the load. If present at the output stage, it's basically to present a very low output impedance to the next stage. If present in the input stage, it must present a very high impedance to the source. The thumb rule is: a device must have low output impedance and the device that connects to it must have high input impedance for transfer of maximum power.

See explanation here:

Why is high input impedance good? - Electrical Engineering Stack Exchange

In our case, we've added a pot between source and K buffer for volume control. Additionally, some of us have made source selection mechanism to be able to connect multiple sources. Effectively it becomes like a preamp, but without the gain (pot only attenuates the incoming signal).

 

[saikatbiswas82]

Last week got the kit from Sachin along with PSU kit. Thank you Sachin and ofcourse Omishra!!

Which one to choose for the transformer, R-core or a toroidal?


One more thing, the PSU is designed to handle multiple pre-amps. Is it OK to house two pre-amps in the same cabinet ( I am looking for a tube based addon in the future). What in mind as of now is to use same PSU with 2 preamps where as power, Inputs and outputs for pre-amps is control by flick of switches.

Anyone tried this before?

@arunlouie...I guess you are following the same way I am going. I am also building a tube buffer and planning to place both k-buffer and the tube buffer in same cabinet with a source selector switch.

I purchased a 30va r core trafo which I think should be fine for powering both the buffers. However keeping some headroom is always advisable.

 

[saheb11123]

What are the taps of the traffo? 15-0-15 ? and its 1amp?

 

[saikatbiswas82]

What are the taps of the traffo? 15-0-15 ? and its 1amp?

12-0-12v 1.25amp

 

[sadik]

Hi Friends,

I have received the PCB's (PSU & Buffer) from Sachin long Back, Thank you Sachin for same as well as OMishra & Quad for designing such a wonderful layout. From Today i have started to build this Buffer.

I am using M.S Plates 1mm thk for Top Cover and Bottom (Black Powder Coated), all Four Walls will be of MDF, Black Colored with Grain texture (as on Speaker Enclosures). Front and Back Panels will be Black Acrylic with Laser Engraved Text and my LOGO (ASB Audio) just thought to give it a logo. A stands for First letter of my Elder Daughter "Arzoo", S stands for my Younger Daughter "Saara" & B for the surname "Bhatkar"

Some Pics of Panel (Front & Back) made for the Enclosure.

There is one mistake. Instead of 220 Volts i wrote 200 V, but that will be fine for me after all i will be using this Buffer. but yes for next time i will cross check the matter 2 times before printing it.

Hope You all will like my Work...

Sadik Bhatkar

 

[arunlouie]

@arunlouie...I guess you are following the same way I am going. I am also building a tube buffer and planning to place both k-buffer and the tube buffer in same cabinet with a source selector switch.

I purchased a 30va r core trafo which I think should be fine for powering both the buffers. However keeping some headroom is always advisable.

Yes exactly. Do you have any tube pre-amp in mind already??

 

[saikatbiswas82]

Yes exactly. Do you have any tube pre-amp in mind already??

I am planning to build Musical Fidelity X10-D clone. Have you shortlisted anything yet?

 

[arunlouie]

I am planning to build Musical Fidelity X10-D clone. Have you shortlisted anything yet?

Just looking into Grounded Grid Pre Amplifier.