I couple months back I decided to build a Tubes4Hifi SP 20 preamp as a kit, which I soon learned was way beyond my skill set. Anyway, after getting the kit assembled, I had issues with the voltage not meeting the specs and in my uninformed effort to fix it accidently fried the high voltage regulation section on both channels and fried a resistor or two on the left channel. I am probably lucky I didn't fry myself. At that point I sent the fully finished preamp back for repair since I knew it was beyond my capabilities. The amp came back with all measurements to spec but with a significant hum coming from the left channel that makes it unlistenable. I assume something happened during shipping, but I'll be damned if I can figure what that might be. The seller has recommend that I flip the tubes, change cables, plug in the preamp and amp into the same outlet and recheck all of the ground connections but nothing I do impacts the hum coming from the left channel. The seller believes it is a grounding issue which seems in line from the limited number of other folks that have had similar issues. I think I need to just suck it up and bring it somewhere local for repair to a knowledgeable tech so I don't do any more harm to the preamp which sounds wonderful, if only from one channel. Can anyone recommend where I should bring it? I have seen mixed comments about Davidson Electronics and limited comments about RocknRoll amps. I also found Stereo Repair World in Huntington. Thanks in advance.
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Davidson i believe has closed... i tried to contact a few times with zero luck. Saw an advert licraigslist with a guy advertising amp repair in patchogue a few weeks back..
Part of the reason i took the deep dive and have a pretty complete work bench.
Im confident enough to work my own stuff, and would be willing to help someone with equal or better knowledge... if you cant find any one, and as a last ditch effort pm me, may be its something we can work on...
Part of the reason i took the deep dive and have a pretty complete work bench.
Im confident enough to work my own stuff, and would be willing to help someone with equal or better knowledge... if you cant find any one, and as a last ditch effort pm me, may be its something we can work on...
Did you ever fix this issue? I was looking at the same preamp myself and wanted to know how it sounded.
A couple of years ago I upgraded an SP14 for a friend who bought it on eBay. It had some issues which I addressed, and he loves it. It's dead quiet in his system. I liked it so much I bought a stuffed board for myself and built my own case. It beat the pants off my Cary SLP98 for "speed" and transparency. I eventually sold it to a friend who envied it and built a "scratch" version with after-market regulator boards for the HV and the filaments. I use it every day and just love the sound. An extremely natural-sounding preamp. The Tubes4HiFi board is very well done, IMO, with good choices of operating points. Stock, it's very very good. With upgrades like caps and quality attenuators it's excellent. I think it's one of the great bargains in tube hifi.
I'm really curious about this new SP20 "based on the famous CAT SL1." I see people recommend the CAT SL1 and it's a fairly expensive preamp. As per the website:
This preamp is based on the CAT SL1 preamp, limited production over the past 30 years and very highly rated.
Sounds pretty promising. I've actually built their PH16 which uses 6922 tubes and I find it to be really nice, paired with a revamped Empire EDR 9 I feel it really fleshes out what's in the groove. I know a lot of people have built and swear by the SP14 but I'm curious if this is considered an upgrade on that, and if so, by how much.
This preamp is based on the CAT SL1 preamp, limited production over the past 30 years and very highly rated.
30 years ago this preamp was around $6000 and is now around $30,000. So the SP20 is not an inexpensive preamp.
It's designed for those who love to roll tubes and capacitors to fine tune the sound quality.
The SP20 uses the same circuit design, using four tubes, a 12AU7 for the input gain, followed by two 12AX7 tubes, with a 6922 tube output driver.
Sounds pretty promising. I've actually built their PH16 which uses 6922 tubes and I find it to be really nice, paired with a revamped Empire EDR 9 I feel it really fleshes out what's in the groove. I know a lot of people have built and swear by the SP14 but I'm curious if this is considered an upgrade on that, and if so, by how much.
I have not solved the hum issue but I did find a simple solution until my skills improve and I can fully diagnose this myself. I clearly have a ground loop issue. I was able to cut the hum down by 50% by tinkering with my ground connections. That moved the hum from one to both channels, but made it a lot more quiet. I fully acknowledge that for anyone with skills with diagnosing tube amps/preamps this is a horrible solution, but I did not want to mess with this any more until I have more knowledge to avoid the risk of damaging this preamp once again. The good news is that I have this preamp connected to a Parasound A21. By turning the gain down on the Parasound to 50%, it is dead quiet. And I have no issue with getting my speakers as loud as I want since the A21 is not short on power. Is this a correct or permanent solution no; Does it allow me to thoroughly enjoy this preamp, absolutely.
I don't have experience with other quality preamps so I cannot provide an audiophile point of view. I can say that to my less than audiophile ear it sounds amazing. I did do all of the upgrades. I agree with the prior comment that voices and instruments are very natural. Sound stage is wide. For reference my points of comparison are using an IOTAVX SA3 as preamp and a B1 with Korg Nutube preamp. I built the Korg only a week ago and put it into my system and really thought it sounded great. It was only when I switched back to the Tubes4Hifi preamp that I noticed how much richer and fuller the sound was (I assume this is the tubes, but again I have never heard a tube amp or preamp before this). Base also kicks in comparison. Even my wife who was reading in the room when I made the switch couldn't help but comment on the improvement.
Last comment regarding Tubes4Hifi. The company has sold a bunch of preamps and most as kits. If you search long and hard you will find that there are maybe a handful of people that have experienced a hum issue that was daunting to solve. This was my first build of an amp or preamp and it was a bit over my head. You don't get full directions like you do with other kits and my soldering skills were still a bit basic. So, the hum is more than likely a build issue as opposed to a design issue. If this is your first build, I would recommend against it. If you have built other things, can solder and have some ability to read schematics you will not be disappointed by the end product.
I don't have experience with other quality preamps so I cannot provide an audiophile point of view. I can say that to my less than audiophile ear it sounds amazing. I did do all of the upgrades. I agree with the prior comment that voices and instruments are very natural. Sound stage is wide. For reference my points of comparison are using an IOTAVX SA3 as preamp and a B1 with Korg Nutube preamp. I built the Korg only a week ago and put it into my system and really thought it sounded great. It was only when I switched back to the Tubes4Hifi preamp that I noticed how much richer and fuller the sound was (I assume this is the tubes, but again I have never heard a tube amp or preamp before this). Base also kicks in comparison. Even my wife who was reading in the room when I made the switch couldn't help but comment on the improvement.
Last comment regarding Tubes4Hifi. The company has sold a bunch of preamps and most as kits. If you search long and hard you will find that there are maybe a handful of people that have experienced a hum issue that was daunting to solve. This was my first build of an amp or preamp and it was a bit over my head. You don't get full directions like you do with other kits and my soldering skills were still a bit basic. So, the hum is more than likely a build issue as opposed to a design issue. If this is your first build, I would recommend against it. If you have built other things, can solder and have some ability to read schematics you will not be disappointed by the end product.
It possible, but in full disclosure I directly connected the grounds for the silent channel to the one with the hum, so it not surprising they both have the hum now And before anyone yells, I know this is wrong, but it let me use the preamp without any discernible hum by turning the gain down on my amp. I need more knowledge before trying to fix this again.
My hum problem
SS Preamp ---> SS amp and Tube amp (no hum with RCA jacks)
Tube Preamp ---> Tube amp (no hum), SS amp Parasound A21 and ML 532 (hum with RCA, no hum with XLR)
So I use audio transformer to convert from RCA to XLR, solve the problem.
SS Preamp ---> SS amp and Tube amp (no hum with RCA jacks)
Tube Preamp ---> Tube amp (no hum), SS amp Parasound A21 and ML 532 (hum with RCA, no hum with XLR)
So I use audio transformer to convert from RCA to XLR, solve the problem.
Any one local who has a tube tester for 6JC6A tubes???
Have 5 off ebay and believe they are NOS..
Closest to Smithtown wins 🏆 lol...
Have 5 off ebay and believe they are NOS..
Closest to Smithtown wins 🏆 lol...