Hello,
I’ve build a clone Blowtorch line amp. See picture of build and circuit below.
As I’m busy with the actual assembly of the PCB’s on a bottom plate from the enclosure, I was testing with different wiring layouts and wires itself (twisted solid core and microphone coax).
During this testing I noticed that one of the 2 balanced line amps generates a Hiss / white noise on the ‘+Out = OUT_P’ output. Taking the signal from ‘-Out = OUT_M‘ gives no noise. Noise sounds like: Analoge ruis - Ambient Reel to Reel Bandrecorder Hiss & Hum - YouTube
I don’t have the knowledge to tell whether a Jfet or a mosfet can generate this as a failure mode due to a static decharge for example. And before I start to remove and change parts, I would like to ask here for experience.
Which part is highest change to resolve this noise issue?
Thanks in advance
I’ve build a clone Blowtorch line amp. See picture of build and circuit below.
As I’m busy with the actual assembly of the PCB’s on a bottom plate from the enclosure, I was testing with different wiring layouts and wires itself (twisted solid core and microphone coax).
During this testing I noticed that one of the 2 balanced line amps generates a Hiss / white noise on the ‘+Out = OUT_P’ output. Taking the signal from ‘-Out = OUT_M‘ gives no noise. Noise sounds like: Analoge ruis - Ambient Reel to Reel Bandrecorder Hiss & Hum - YouTube
I don’t have the knowledge to tell whether a Jfet or a mosfet can generate this as a failure mode due to a static decharge for example. And before I start to remove and change parts, I would like to ask here for experience.
Which part is highest change to resolve this noise issue?
Thanks in advance
Attachments
Problem found when probing with the signal wire running to the power amp and trying to find origin of noise.
One Jfet inside the 2SK389BL of the noisy side of the balanced line amp was the issue.
Luckily I had another 2SK389BL with about same IDSS value. Difference in IDSS is 0.08mA.
One Jfet inside the 2SK389BL of the noisy side of the balanced line amp was the issue.
Luckily I had another 2SK389BL with about same IDSS value. Difference in IDSS is 0.08mA.
Hi. Since no one else has posted anything in this thread, I might as well do that.
Why the Blowtorch ? I know there are several threads on this pre and its been featured a lot, but what makes it special ?
Also, how do you like the MUSES ?
Why the Blowtorch ? I know there are several threads on this pre and its been featured a lot, but what makes it special ?
Also, how do you like the MUSES ?
Why I tried to clone the Blowtorch:
1. Have many 2sk389BL and 2SJ109BL on hand
2. Open loop. (Based on others with many moons more experience than me)
3. All reviews found, are very positive.
4. Designed by a legend with more experience than I will collect in the next 100years.
5. Balanced (in case I needed it). Future plan =AX252 from Zen Mod, here I need it to have sufficient gain.
6. Not a 100% copy of an existing schematic, but based on a lot of fun reading thousands of posts.
Muses 72323: I need to have fun = not coming out of my chair when willing to adjust volume. Remote control is a must for me.
1. Have many 2sk389BL and 2SJ109BL on hand
2. Open loop. (Based on others with many moons more experience than me)
3. All reviews found, are very positive.
4. Designed by a legend with more experience than I will collect in the next 100years.
5. Balanced (in case I needed it). Future plan =AX252 from Zen Mod, here I need it to have sufficient gain.
6. Not a 100% copy of an existing schematic, but based on a lot of fun reading thousands of posts.
Muses 72323: I need to have fun = not coming out of my chair when willing to adjust volume. Remote control is a must for me.
1-4. I've never heard the Blowtorch but it has a legendary status that is for sure. So good for you. I have 1-2 commercial products that I will clone and both are legendary in their own way.
5. FYI, a friend built the XA252 and experience instability issues with it which made me hold on building one for myself.
MUSES is suppose to be alright and has the convenience of being able to control remotely. I pulled up the " Muses Electronic Volume Control Build from Wisconsin" thread which is based on meldano which is the same for you, so gonna take a look at that.
Thanks for sharing 🙂
5. FYI, a friend built the XA252 and experience instability issues with it which made me hold on building one for myself.
MUSES is suppose to be alright and has the convenience of being able to control remotely. I pulled up the " Muses Electronic Volume Control Build from Wisconsin" thread which is based on meldano which is the same for you, so gonna take a look at that.
Thanks for sharing 🙂
Yes. There is if I remember correctly, a resistor that keep blowing and the cause for this is not been established. I can ask again if you want exact info.
Quote from my friend (XA252): "R24 I believe. The one between I believe Q1 and Q2."
Btw, have you A-B'd this preamp against others ?
Btw, have you A-B'd this preamp against others ?
Ok, issue why R24 is smoking is known and solved. Happy that this is the issue at your friend.
Yes, I compared with only 1 preamp, a PS audio trio preamp. Was not hard to tell which I liked more. Blowtorch has very nice low response and much more transparancy.
Yes, I compared with only 1 preamp, a PS audio trio preamp. Was not hard to tell which I liked more. Blowtorch has very nice low response and much more transparancy.
Interesting, how was it solved ?
I wonder how the Blowtorch compare to a good tube pre or some of the PASS pre, that would be an interesting comparison. I think I need to dig around a bit and get some of peoples impression.
I can always tickle your fancy for advice if I want to build your version 😀
I wonder how the Blowtorch compare to a good tube pre or some of the PASS pre, that would be an interesting comparison. I think I need to dig around a bit and get some of peoples impression.
I can always tickle your fancy for advice if I want to build your version 😀
Hi Bensen,
I have made several versions of John Curl's Blowtorch line stage (in consultation with JC). I have found that changing the 200 ohm resistors to current sources makes a significant improvement with regard to distortion. It also allows running all the devices at lower currents (I used 10mA for the input stage and 10mA for the output stage). The devices seem to be more linear at 10mA than at 40-50mA.
I have written this up in audioXpress. You can find the articles here:
https://audioxpress.com/article/aud...es-folded-cascodes-and-current-mirrors-part-1
https://audioxpress.com/article/aud...es-folded-cascodes-and-current-mirrors-part-2
https://audioxpress.com/article/aud...es-folded-cascodes-and-current-mirrors-part-3
-Morty
I have made several versions of John Curl's Blowtorch line stage (in consultation with JC). I have found that changing the 200 ohm resistors to current sources makes a significant improvement with regard to distortion. It also allows running all the devices at lower currents (I used 10mA for the input stage and 10mA for the output stage). The devices seem to be more linear at 10mA than at 40-50mA.
I have written this up in audioXpress. You can find the articles here:
https://audioxpress.com/article/aud...es-folded-cascodes-and-current-mirrors-part-1
https://audioxpress.com/article/aud...es-folded-cascodes-and-current-mirrors-part-2
https://audioxpress.com/article/aud...es-folded-cascodes-and-current-mirrors-part-3
-Morty
Well, hello Morty,
Offcourse I’m familiar with these AudioXpress articles! Thanks for the entire article, sofar your final circuit was not known for me. Just only changing the 200R resistors to a CCS is not possible. No I see how you solved this. Very nice!
Can you compare soundwise your version with the “original” (in how far the original is known)?
Thanks
Offcourse I’m familiar with these AudioXpress articles! Thanks for the entire article, sofar your final circuit was not known for me. Just only changing the 200R resistors to a CCS is not possible. No I see how you solved this. Very nice!
Can you compare soundwise your version with the “original” (in how far the original is known)?
Thanks