Generally speaking, there are far too many questions regarding components that are not listed in the BOM and on changing the amp parameters.
The Wolverine team has thoroughly tested the amp with the components listed in the BOM and build guide.
In short we do not know if the components that people have chosen (or got for free) will work as per the amp design.
Also if you want to run the amp outside the specified parameters eg at higher rail voltages into low impedances that exceed the SOA of the transistors you are ignoring all the effort that has gone into the design of this amp and you are on your own.
A gentle reminder that this is the build thread to assist people in building their amps. Questions on changing the specifications etc should go into the design thread.
The Wolverine team has thoroughly tested the amp with the components listed in the BOM and build guide.
In short we do not know if the components that people have chosen (or got for free) will work as per the amp design.
Also if you want to run the amp outside the specified parameters eg at higher rail voltages into low impedances that exceed the SOA of the transistors you are ignoring all the effort that has gone into the design of this amp and you are on your own.
A gentle reminder that this is the build thread to assist people in building their amps. Questions on changing the specifications etc should go into the design thread.
There are ksa1220A/ksc2690A. I used these in various designs with PS of +/-57V. These have lower Ic (1.2A, max 2.5A) than Toshibas and Sankens but have the best SOA (0.1ADC at 100V) and are the fastest (155MHz and 175MHz). Possibly one could use these here as well at lower PS voltages (and output power).
I wondered why such a high voltage was specified for these two mica caps and why 630VDC for 100pF polypropylene C0?
Janusz, its obvious that one doesn't need very high voltage caps in those positions. When we created the BOM most of the parts that we wanted were not in stock. We needed to update the BOM on a daily basis as stock would disappear hourly.
I’ve actually uses KSA1220 and KSC2690 on multiple occasions to replace faster drivers like 2SC1913 and 2SA913 and it works quite well. The very first time I did it was to a Marantz 2330b which has +/- 67v rails and two pair of outputs per channel. Been running perfectly for years. Luckily I have many, but the A1220 was EOL’d awhile back and not sure I’d go that route running 3-4 pair of outputs on 71 that will run 4 ohm loads. But if you can get them ans run on the lower rails I’m sure it’ll work.
Dan
A1220 is no where to found besides form suspicious dealers... Through hole is a fast dying breed.
KSA1381E/KSC3503D are set to EOL 5.jan 2025 if anyone needs to buy them within a decent timeframe🙂
KSA1381E/KSC3503D are set to EOL 5.jan 2025 if anyone needs to buy them within a decent timeframe🙂
I know, it sucks. Luckily I have a couple hundred pair of the 1220/2690 left. I use TTA/TTC004b where possible now and save them. I’m also saving my KSA1381/KSC3503 now that they’re EOL, have about 240 pairs. I have 700 pair of 2SA1209S and 2SC2911S which works in most instances as the 1381/3503, plus they have higher gain which is nice. Oh well, I have resorted to using SMD on adapters boards for through hole. Works well enough. Not to get the thread off topic.
Dan
Hi Dan,
That reminds me of a Marantz 3650 phono PCB.
Any reason you replaced all the transistors?
That reminds me of a Marantz 3650 phono PCB.
Any reason you replaced all the transistors?
Lol, well wouldn’t you know it, it is a 3650 phono board. Nice guess lol.
A friend of mine picked up this preamp about a week ago and he was told that a tech did some restoration work on it, so he wanted me to look through it for him. The work done was questionable, and the quality of components was not great so I just went through and did a restoration for him. But for some reason, they decided to remove every 2SC2240BL and 2SA970BL and replaced them with KSC1815 and KSA1015. Going from a low noise high gain transistor to a low gain. Not sure what they were thinking. Honestly, I should’ve just put in some KSC1845s and KSA992s, but I wanted to use something a little closer to the originals so I put in 2SC2713BL and 2SA1163BL. Though I was kind of sad to see that these parts don’t have all that high of gain, at least not as high as I had thought they would be. The 2713BL were averaging 450, some hitting 500. The KSC1845 I have measure 400-450. Going SMD I should have used FJV1845, I have E grade and get 500-600 from them. Oh well. I also have some 2SC3324BL (really wish I would have grabbed its complement), but they measured about the same as the 2SC2713BL, mostly in the 450 range. I thought the 2240 was in the 600ish range.
Dan
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Since we are talking low noise high gain transistors, I wanted to ask a question about the ones used in this design.
First off I want to state that the designers of the amp know more than me, I mean light years ahead of knowledge. For this amplifier I will be using some Onsemi BC550C and BC560C. I always thought these to be low noise, high gain transistors, though I didn’t know how the noise spec matched to the 1845/992 or 2240/970 pairs. Well after some reading and asking questions myself it would seem that many don’t consider the BC transistors to be low noise. This is due to their high base resistance or Rbb and are even considered to be high noise by some. Some even reporting audible noise floor increase when using them.
Obviously, the amplifier performs very well, but I was just curious why these transistors were selected for the design versus say something like the 1845/992 or even Zetex parts which are supposed to be fantastic. Not at all criticizing, just trying to learn/understand the thought process.
Thank you,
Dan
First off I want to state that the designers of the amp know more than me, I mean light years ahead of knowledge. For this amplifier I will be using some Onsemi BC550C and BC560C. I always thought these to be low noise, high gain transistors, though I didn’t know how the noise spec matched to the 1845/992 or 2240/970 pairs. Well after some reading and asking questions myself it would seem that many don’t consider the BC transistors to be low noise. This is due to their high base resistance or Rbb and are even considered to be high noise by some. Some even reporting audible noise floor increase when using them.
Obviously, the amplifier performs very well, but I was just curious why these transistors were selected for the design versus say something like the 1845/992 or even Zetex parts which are supposed to be fantastic. Not at all criticizing, just trying to learn/understand the thought process.
Thank you,
Dan
Hi Dan,
lol!
I was trained at Marantz (Superscope), and did warranty on these. I own a 3650 and SC-9 (same phono board). It is one of the best sounding and quiet phono preamps I have heard. I did a lot of study on these because we had some burning out. I was told about changing grounds and HF instability by the USA service department. I followed their directions and of course they were barking up the wrong tree entirely.
Clue, the SC-9 (later) is identical, but has vents in the shield for the phono. I traced the issue back to loss of output bias, the temperature sensing diodes (varistors) are located on the PCB away from the heat sinks. I use thermal epoxy and attached them to the heat sinks, problem solved. You could just position them through the fins, but movement may cause them to short.
The transistors used were among the lowest noise at the time, with consistent characteristics in production quantities. They were my favorite parts to use. Often you'll see certain part numbers singled out as "the best". But this is a Japanese design using very high quality Japanese parts known for consistency. The other critical part is, availability for production at that point in time. Also, if an engineer is comfortable with certain parts, they will use them.
Low noise. This is far more important in the first amplification stage, not so much in following stages. So could you install a "better part". Yup, but will it buy you anything at all? Probably not, certainly nothing that matters. Also consider surface noise off the LP or 45. This far outweighs what most normal phono stages have for basic noise level. This phono stage is far better than what is needed. It also has wonderful overload ability (supplies are over +/- 27 VDC). It has very low output impedance and cann drive almost anything. Remember, the tape output jacks are directly connected to the sources, also a phono preamp in almost every preamp out there. Carver buffered some.
My personal take? Install the original parts unless they were overheated. Matching complimentary beta helps distortion figures some. Look at power supply noise, it can be improved these days with minor changes. We are splitting hairs now, the design as manufactured performs extremely well. So do the following stages. Please don't mess with it.
The one biggest problem with these preamps (and the 2385, 2500, 2600) are intermittent switches. I hate them! These particular switches may not respond well to cleaning, try not to clean the slide controls.
- Chris
lol!
I was trained at Marantz (Superscope), and did warranty on these. I own a 3650 and SC-9 (same phono board). It is one of the best sounding and quiet phono preamps I have heard. I did a lot of study on these because we had some burning out. I was told about changing grounds and HF instability by the USA service department. I followed their directions and of course they were barking up the wrong tree entirely.
Clue, the SC-9 (later) is identical, but has vents in the shield for the phono. I traced the issue back to loss of output bias, the temperature sensing diodes (varistors) are located on the PCB away from the heat sinks. I use thermal epoxy and attached them to the heat sinks, problem solved. You could just position them through the fins, but movement may cause them to short.
The transistors used were among the lowest noise at the time, with consistent characteristics in production quantities. They were my favorite parts to use. Often you'll see certain part numbers singled out as "the best". But this is a Japanese design using very high quality Japanese parts known for consistency. The other critical part is, availability for production at that point in time. Also, if an engineer is comfortable with certain parts, they will use them.
Low noise. This is far more important in the first amplification stage, not so much in following stages. So could you install a "better part". Yup, but will it buy you anything at all? Probably not, certainly nothing that matters. Also consider surface noise off the LP or 45. This far outweighs what most normal phono stages have for basic noise level. This phono stage is far better than what is needed. It also has wonderful overload ability (supplies are over +/- 27 VDC). It has very low output impedance and cann drive almost anything. Remember, the tape output jacks are directly connected to the sources, also a phono preamp in almost every preamp out there. Carver buffered some.
My personal take? Install the original parts unless they were overheated. Matching complimentary beta helps distortion figures some. Look at power supply noise, it can be improved these days with minor changes. We are splitting hairs now, the design as manufactured performs extremely well. So do the following stages. Please don't mess with it.
The one biggest problem with these preamps (and the 2385, 2500, 2600) are intermittent switches. I hate them! These particular switches may not respond well to cleaning, try not to clean the slide controls.
- Chris
Hey Chris, thank you for all of that info. Would be cool to be old enough to have worked on these gear back when it was being released. The entire post was regarding the 3650 correct?
You say don’t mess with it, you do know that I wasn’t messing with it correct? Someone that had their hands on it before me took out the 2240BL and 970BLs, which I agree with you were definitely some of the best available, and swapped them with low gain KSC1815 and KSA1015. So I was trying to revert it back to factory, but unfortunately I don’t have any 2SC2240 or 2SA970. So I went with something as similar as I could find, which is the surface mount version of those transistors. I wouldn’t even imagine messing with it, I know this is a very nice preamp.
And yes, these are some of the worst switches I’ve ever experienced in my life. I was tracing a channel throughout the preamp, trying to figure out where the heck I was losing it, I would get it back and then it would disappear, the entire time it was a switch.
Dan
Hi Dan,
Yes, I was talking about this phono PCB and the 3650/SC-9. We are OT for this thread though. I can answer any further questions via PM.
No, I got that you didn't mess it up. I just would recommend you install the original transistors if they are available. If not, you did fine. Don't try and buy the originals unless you know for certain the parts are old stock.
Those switches ... arrrrgh! First try using LPS Micro-X (04516), if that doesn't work, then Wurth Contact OL. It works on sulphides, they are different cleaners. Both are zero residue. Don't use anything that leaves any kind of residue when cleaning switches. For pots, the smallest amount possible in to the centre. It is the slip ring that gets noisy, not the resistive element. All cleaners attack the protective greases and lubricants, so minimal chemicals.
What were they thinking when they went with those switches??? This is just before Philips got their ugly claws on Marantz, it is possible there was influence already. Normal Marantz design and parts were far better than this.
Yes, I was talking about this phono PCB and the 3650/SC-9. We are OT for this thread though. I can answer any further questions via PM.
No, I got that you didn't mess it up. I just would recommend you install the original transistors if they are available. If not, you did fine. Don't try and buy the originals unless you know for certain the parts are old stock.
Those switches ... arrrrgh! First try using LPS Micro-X (04516), if that doesn't work, then Wurth Contact OL. It works on sulphides, they are different cleaners. Both are zero residue. Don't use anything that leaves any kind of residue when cleaning switches. For pots, the smallest amount possible in to the centre. It is the slip ring that gets noisy, not the resistive element. All cleaners attack the protective greases and lubricants, so minimal chemicals.
What were they thinking when they went with those switches??? This is just before Philips got their ugly claws on Marantz, it is possible there was influence already. Normal Marantz design and parts were far better than this.
I agree, a bit off topic, I’ll shoot you a PM, but thanks for answering the questions and good memory!
Dan
Dan
I'm going cross-eyed building my Mouser order, but I do have a question about drivers. I'm doing 4 pair with approximately 71 V rails. I want to minimize drilling the diyaudio 5U heatsinks. I'm looking at Toshiba 2SC5200N (S1, E, S) and 2SA1943N (S1, E, S) which are in a TO-3P-3 package. The base numbers are listed in the BOM on sheet 2. I confused by the (S1, E, S) designation added to the base part number, and also by the -3 added to the TO-3P package designation. Am I ok using these?
Thanks,
John
Thanks,
John
Oops, I see these drivers listed as alternatives in the BOM. Sorry for the bother, but I would be interested to learn what those additional letters mean to the part number and the transistor package....
John
John
Yes, of course...the output transistors. I'm using MJE15032G/MJE15933G as drivers.
Thanks,
John
Thanks,
John
Question regarding transformers: Slowly putting together my 4th group buy boards and looking at my options for transformers, it doesn't seem I have many. I bought a 4U chassis from modushop without really thinking about the logistics but I can get two 75mmx150mm torroid covers in there with some clearance so I'm looking for something that will fit in there. I was looking for two 600VA torroids with dual 50v secondaries but all I could find is AnTek AN-6450, which is too tall, ATO, which fits but don't want to pay that much if I can avoid it, or AliEspress but that just feels wrong. Avel Lindberg Y236858 is the right size but its 625VA/50vx2, would that be an issue? I saw the note regarding using transformers larger thanwhat's listed in the BOM and figured I should ask you guys first.