Hi everybody!
So after a few days of listening, I've made some modifications on the amp, firstly I changed R13 again for a 54.9K witch gives me a 2.1A Bias. I also unsoldered the terminal posts for input and output signals and soldered the wires directly.
I put two 10R ntc on the mains for a softstart (no more fuse blowing 😉 ) and twisted the wire for preventing inductance and tidying it all.
I also found some 11V DC on the fan controller board to feed the main switch led.
Photos to come.
I ain't soldered the XLR input yet.
Questions:
- Now, seems it's important to get a 50% AC current gain, I understand that it's supposed to be tweaked by a resistor, but I must firstly know how to measure the AC current gain and what res to alter.
- How can I measure the output power of my amp?
- How to measure input and output impedance of the amp or/and a source (say a phono preamp or a CD player)
- I have to build a source selector, however I have to connect both balanced (via XLR) and unbalanced sources. I already have this selector board
Input Selector Kit 4CH (4-to-1 Way Stereo)_Input Selector_Accessories Kit_Analog Metric - DIY Audio Kit
It can support 4 rca or 3 rca plus 1 XLR.
I want to put a pot on this selector output (50k alps pot or 50K dale stepped pot I have at my disposal).
How should I wire the three rca and the xlr on this board? more precisely, is it possible to route the rca input through the balanced output (inputting rca and outputting through XLR outputs)?
And if it's possible, how am I supposed to wire the xlr signal to the pot (3 pin per channel vs 2 for rca)
-Also, as the volume of my turntable through my Dynavox tpr-2 tube riaa preamp is somewhat low (have to push volume at max on the tpr-2 to get something punchy), shall I consider a preamp buffer inside my "selector box", something like the Pass B1? What benefit shall I expect from it?
I know that's quite a lot of questions but I'm still new to hifi and eager to gain more knowledge from you
So after a few days of listening, I've made some modifications on the amp, firstly I changed R13 again for a 54.9K witch gives me a 2.1A Bias. I also unsoldered the terminal posts for input and output signals and soldered the wires directly.
I put two 10R ntc on the mains for a softstart (no more fuse blowing 😉 ) and twisted the wire for preventing inductance and tidying it all.
I also found some 11V DC on the fan controller board to feed the main switch led.
Photos to come.
I ain't soldered the XLR input yet.
Questions:
- Now, seems it's important to get a 50% AC current gain, I understand that it's supposed to be tweaked by a resistor, but I must firstly know how to measure the AC current gain and what res to alter.
- How can I measure the output power of my amp?
- How to measure input and output impedance of the amp or/and a source (say a phono preamp or a CD player)
- I have to build a source selector, however I have to connect both balanced (via XLR) and unbalanced sources. I already have this selector board
Input Selector Kit 4CH (4-to-1 Way Stereo)_Input Selector_Accessories Kit_Analog Metric - DIY Audio Kit
It can support 4 rca or 3 rca plus 1 XLR.
I want to put a pot on this selector output (50k alps pot or 50K dale stepped pot I have at my disposal).
How should I wire the three rca and the xlr on this board? more precisely, is it possible to route the rca input through the balanced output (inputting rca and outputting through XLR outputs)?
And if it's possible, how am I supposed to wire the xlr signal to the pot (3 pin per channel vs 2 for rca)
-Also, as the volume of my turntable through my Dynavox tpr-2 tube riaa preamp is somewhat low (have to push volume at max on the tpr-2 to get something punchy), shall I consider a preamp buffer inside my "selector box", something like the Pass B1? What benefit shall I expect from it?
I know that's quite a lot of questions but I'm still new to hifi and eager to gain more knowledge from you
It sounds like you need a bit more gain in the phono chain. You can either modify your phono preamp circuit to give more gain or put something like an Aleph P after your source selector. The Aleph P will also accept balanced and single ended inputs as well as do single ended to balanced output conversion for you.
A B-1 is a single ended buffer and will not give you gain or handle balanced operation. Read the Bride of Son of Zen article and the Aleph P 1.7 thread to help you understand single ended to balanced and balanced to single ended conversion.
A B-1 is a single ended buffer and will not give you gain or handle balanced operation. Read the Bride of Son of Zen article and the Aleph P 1.7 thread to help you understand single ended to balanced and balanced to single ended conversion.
R13 (the one you have been adjusting) is actually the AC gain, although it has a direct correlation with Bias. Set the bias to whatever you think sounds best, or whatever gives 55C heatsinks and 65C Pin 2 of the mosfets
Borrow a big load resistor, signal generator and oscilloscope. Feed the amp a 1Khz sine wave until it clips, back off until the sinewave is smooth and then measure the peak-to-peak voltage.
V Pk-Pk*.3535(^2)/load = RMS power
For example, if your amp can swing 50V into an 8ohm resistor:
50*.3535= 17.675
17.675(^2) = 312.4
312.4/8 = 39.05W
No, you need gain if your Phono is too low. So you have 2 choices - increase the gain of your phono amp or make a preamp with gain. The B1, as Bob mentions, has no gain.
If you can increase the phono gain, the B1 is great. Make the DCB1.
Thanks for your answers 🙂
Do you think the Bosoz would work too? In fact, I can find cheap PCBs for it in france.
Do you think the Bosoz would work too? In fact, I can find cheap PCBs for it in france.
If you find one of the BOSOZ variants that feeds the differential from a CCS (constant current source/sink) it will perform better as an unbalanced to balanced converter. Without the CCS the inverting signal is a bit lower level. See the article.
There are developments out there that came darned close to being an Aleph P, including CCS, cascoded diffential and are X'd.
There are developments out there that came darned close to being an Aleph P, including CCS, cascoded diffential and are X'd.
yes do it😀
i have both a aleph p and a bosoz both are real good.
the difference imho is not so big that the aleph p is way more much better.
But a little bit😀
So bosoz would be a good choice.
...and if you take the bosoz take a look at the service manual from the AP1.7
the mute/delay circut for on/off and the power supply (have to adapt to +/-V) maybe also works for Bosoz.
I will test it if my bosoz gets a permanent home🙄
i have both a aleph p and a bosoz both are real good.
the difference imho is not so big that the aleph p is way more much better.
But a little bit😀
So bosoz would be a good choice.
...and if you take the bosoz take a look at the service manual from the AP1.7
the mute/delay circut for on/off and the power supply (have to adapt to +/-V) maybe also works for Bosoz.
I will test it if my bosoz gets a permanent home🙄
Is there someone with a gerber file of a good bosoz pcb, or anything that should be used by a pcb maker?
Ok, but I can't find the bosoz and it's psu gerber files Nelson claim's to be on Passlabs.com.
Is there someone still having them somewhere?
Is there someone still having them somewhere?
Not Found
The requested URL /pdf/art_bosoz.pdf‎ was not found on this server.
ouch! 🙂
EDIT:
It's seems like it's the pdf of the article, I already have it, Ithought about a specific drawing, made for pcb maker, but perhaps it will be enough for him.
Thank you 😉
The requested URL /pdf/art_bosoz.pdf‎ was not found on this server.
ouch! 🙂
EDIT:
It's seems like it's the pdf of the article, I already have it, Ithought about a specific drawing, made for pcb maker, but perhaps it will be enough for him.
Thank you 😉
Last edited:
dunno for Gerbers , but article is here : https://www.passdiy.com/project/preamplifiers/balanced-zen-line-stage
I have a set of Kari's CCS/Cascoded/X-D boards that I'm not using if you want them.
I built a set and they sound great using Kari's PSU boards (also available if wanted). I ended up going a different direction with my system. Since the input differential is cascoded at 10V you could use a set of jfets if you set the CCS appropriately...
I have a BOM, and the schematic is here: http://www.diyaudio.com/forums/pass-labs/53396-heatsinks-bosoz-27.html
I built a set and they sound great using Kari's PSU boards (also available if wanted). I ended up going a different direction with my system. Since the input differential is cascoded at 10V you could use a set of jfets if you set the CCS appropriately...
I have a BOM, and the schematic is here: http://www.diyaudio.com/forums/pass-labs/53396-heatsinks-bosoz-27.html
Hey I have those boards too (now where did I put them?).
If you end up using Kari's board, make sure you check for the silk screen
error on the power supply diodes...
Dennis
If you end up using Kari's board, make sure you check for the silk screen
error on the power supply diodes...
Dennis
Thanks BobEllis,
I'm really interested by the boards (preamp and psu) If you agree to sell them to me 😉
I don't really understand all you said about cascode and CCS thingies, I have to read some of Nelson's articles.
Yup, the polarity was wrong on some of them.
http://www.diyaudio.com/forums/pass-labs/53396-heatsinks-bosoz-52.html#post705743
Cheers,
Dennis
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