I have this preamp that I did not hook up until yesterday.
Little Bear P3 Vacuum Tube Preamplifier Class A Audio HiFi Stereo Pre-amp DIY_US | eBay
I have the Logitech Squeezebox Touch that set to 100% volume so it is bit-perfect. However, I cannot turn the volume on the preamp more than 9 o'clock. Way too loud (I have 6 ohm 91db speakers connected currently).
My question is if there are any tech specs I should be looking when picking a preamp for this amp?
Little Bear P3 Vacuum Tube Preamplifier Class A Audio HiFi Stereo Pre-amp DIY_US | eBay
I have the Logitech Squeezebox Touch that set to 100% volume so it is bit-perfect. However, I cannot turn the volume on the preamp more than 9 o'clock. Way too loud (I have 6 ohm 91db speakers connected currently).
My question is if there are any tech specs I should be looking when picking a preamp for this amp?
You don't need a different preamp. You can modify the board for a lower gain or use a voltage divider/damping attenuator. Or you could change the potentiometer of the preamp for a wider usable range.
Indeed.
I had not thought to fluctuation.
So, a few calculations (they won't to be uber perfects):
48V/1. 414=34Vac (max nominal secondary)
34V/1.1=31Vac (max nominal secondary with a good margin - net fluctuation).
So i think I have to look for a 30V / 400VA trafo.
But now it not seems to be a good deal for me.
What do you think about the meanwell 48V 600W?
It's at 120€.
A soft start is needed even with an smps?
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What speakers are you planning to use with it? If you are going to use 8-ohm speakers, even a 200VA transformer may be sufficient. If you are going to use 4-ohm speakers, 350-400VA. Despite the 2x400W in the title, this is more like a 2x90W into 8-ohm or 2x175W into 4-ohm amplifier for all practical purposes, and that is assuming you have a solid 48V regulated supply voltage.
600W 48V Meanwell is a good supply, but it is extremely overpriced IMHO. Furthermore, you don't really need that kind of power unless you will be using your amp to drive PA speakers at 100% volume continuously. (Even with 3-ohm speakers, the output spec for the Sure amp is 2x234W at 1%THD).
A more modest 400W 48V SMPS should work fine. There are plenty of them for sale on eBay for less than $30 including shipping:
AC110/220V to DC 48V 8.3A 400W Voltage Transformer Switch Power Supply Converter | eBay
You may even be able to find one in your local electronic parts store, or a store that sells CNC Machine parts and supplies.
600W 48V Meanwell is a good supply, but it is extremely overpriced IMHO. Furthermore, you don't really need that kind of power unless you will be using your amp to drive PA speakers at 100% volume continuously. (Even with 3-ohm speakers, the output spec for the Sure amp is 2x234W at 1%THD).
A more modest 400W 48V SMPS should work fine. There are plenty of them for sale on eBay for less than $30 including shipping:
AC110/220V to DC 48V 8.3A 400W Voltage Transformer Switch Power Supply Converter | eBay
You may even be able to find one in your local electronic parts store, or a store that sells CNC Machine parts and supplies.
Thenks.
Now i saw a good quality 30V 500 VA trafo is at 70€.
What do you think is the better choice, smps or linear?
Cost is not an issue at those prices for me.
That's right, higher voltage and lower current is much cheaper with a transformator.
The Meanwell SMPS are very good. There are cheaper ones but I don't know that much models/brands. There are a lot of recommendations for the Meanwell PS, I think you can't do anything wrong there.
No, that's not necessary. The huge currents only happen with linear PSs because of the non-magnetized core of the transformer. Ofcourse it will have some peak at the start because of the capacitors but nowhere near the values of a conventional power supply.
I would prefer a SMPS for the Class-D amplifier board - makes the chassis a lot lighter. (BTW, I use AA-AB32313 with a 400W 48V SMPS and with 6-ohm speakers.)
With the linear PSU solution, you have to add the cost of rectifier components to the cost of the transformer as well.
Well, it depends. Usually, a SMPS is the better choice because it has a more stable voltage but doesn't handle peaks as well as a linear PS. If you use the amp for high power subs, you should add high capacity low ESR capacitors.
That's right but you don't need low ESR capacitors. On the other hand, you need a soft-start circuit with a such powerful transformator. That isn't expensive but you have to think about it.
Generally, SMPS are much lighter, smaller, usually cheaper and are mostly more flexible regarding the input voltage. Linear PS are much more forgiving regarding overload and 'live' longer (40+ years if not heavily abused compared to 10 to 20 years at SMPSs).
I have the board up and running now. Initial impression is good and a step up compared to the Pioneer vsx-d912 (Earl Geddes old reference amp) when driving a pair of Stage Accompany m4744.
I have a new pre amp in use with the Sure amp, later I'll try the pioneer as pre amp to confirm that it's not just the new pre amp that is better then the pioneers pre.
What pre amp and speakers are you all using together with the Sure amp?
And what case/box/enclosure are you going to put the amp board in?
I have put mine temporarily into a Tupperware box, not pretty.
I have a new pre amp in use with the Sure amp, later I'll try the pioneer as pre amp to confirm that it's not just the new pre amp that is better then the pioneers pre.
What pre amp and speakers are you all using together with the Sure amp?
And what case/box/enclosure are you going to put the amp board in?
I have put mine temporarily into a Tupperware box, not pretty.
OK, have been using a YJ IRS2092 for a while now, and thought I'd try this amp with a Connex SMPS 300R 48v turned down to 46v and using the Sure volume control. I had one one weirdness with the volume control but other than that, all good. It seemed to go haywire??
Overall impressions is better than IRS2092. Better bass and mids and equal trebs. Got an Alps to try but have not got there yet. BTW mine is a home theater setup with Acoutech floorstanders. Great speakers though. My favorite amp to date
Overall impressions is better than IRS2092. Better bass and mids and equal trebs. Got an Alps to try but have not got there yet. BTW mine is a home theater setup with Acoutech floorstanders. Great speakers though. My favorite amp to date
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Good to know that the sure volume pot is ok, except for the time it went haywire.
I might try a sure pot aswell.
After listening to the amp for a few days now the fan is starting to get on my nerve. It is turning on every 10-15 min or so and when listening at night time at low volume setting it is really disturbing, the fan is really quite loud.
It dousnt seem to get very warm but the fan still start to spinn. Any idé if it is safe to use the amp sans fan?
I might try a sure pot aswell.
After listening to the amp for a few days now the fan is starting to get on my nerve. It is turning on every 10-15 min or so and when listening at night time at low volume setting it is really disturbing, the fan is really quite loud.
It dousnt seem to get very warm but the fan still start to spinn. Any idé if it is safe to use the amp sans fan?
I have used a Pioneer Spec 1, Kenwood Basic C2, Yamaha C2, Amber Model 17. The Amber and the Yamaha have been my favorites, and I would keep using the Yamaha but it needs a small repair. The Amber is so close to the Yamaha but lacks the same level of bass punch that yamaha is so good at. The Amber preamplifiers are little known gems.
My sources are a Sony ES changer and a Kyocera PL 601 TT with a NOS Micro Acoustics 3002 cartridge. I listen through JBL L65s.
The SA 4744 speakers I use is an 8 Ohm load and 93 db/w, 12" woofer and big ribbon mid/tweeter.
Don't know at what voltage I listen when at low levels but I would describe it as somewhere between whispering and normal talking levels.
The fan goes on every 10 to 15 min wether I listen at high levels or low.
I don't like listening to headphones that is why I listen at such a low level and it is strictly at night I listen at low levels.
And I am quite sure I'm not pushing the amp to much during day time either, I rarely listen at concert levels.
The pre in use at the moment is a Embla pre 1 a very minimalistic Norwegian built pre with one entrance for source and just a remote for volume, no volume knob on the pre it self.
I will compare it against the pioneer vas d912s pre stage and also against a Rotel rc-995.
But the comparison will have to wait until I have put the Sure amp into a proper box and I need to do something to solve the fan noise,
By the way that Pioneer spec 1 is a lovely looking unit!
My source at the moment is chrome cast, Hifimediy 9018 ESS dac and music from Tidal.
Don't know at what voltage I listen when at low levels but I would describe it as somewhere between whispering and normal talking levels.
The fan goes on every 10 to 15 min wether I listen at high levels or low.
I don't like listening to headphones that is why I listen at such a low level and it is strictly at night I listen at low levels.
And I am quite sure I'm not pushing the amp to much during day time either, I rarely listen at concert levels.
The pre in use at the moment is a Embla pre 1 a very minimalistic Norwegian built pre with one entrance for source and just a remote for volume, no volume knob on the pre it self.
I will compare it against the pioneer vas d912s pre stage and also against a Rotel rc-995.
But the comparison will have to wait until I have put the Sure amp into a proper box and I need to do something to solve the fan noise,
By the way that Pioneer spec 1 is a lovely looking unit!
My source at the moment is chrome cast, Hifimediy 9018 ESS dac and music from Tidal.
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I was referring to the Power Supply voltage your running at. Some people say that it sounds better a little under max voltage of 50v, so I run mine at 46v. I'm wondering if that is making the difference? Maybe the preamps are causing overheating?? dunno... just looking for answers.
Maybe you could email Sure and see if it's a defective thermistor. ?? Where it's at and if it could be replaced. I think their off vacation now
When I get back home in a few days, I'll open my case and check mine out and let you know what it does.
If you look at the manual it's a NTC at lower center just above the caps on the bottom of the picture. probably hooked to the heatsink just below the fan next to the fan plug. With everything off, make sure the fan plug is seated correctly.
http://www.parts-express.com/pedocs...32313-2x400w-audio-amplifier-board-manual.pdf
When I get back home in a few days, I'll open my case and check mine out and let you know what it does.
If you look at the manual it's a NTC at lower center just above the caps on the bottom of the picture. probably hooked to the heatsink just below the fan next to the fan plug. With everything off, make sure the fan plug is seated correctly.
http://www.parts-express.com/pedocs...32313-2x400w-audio-amplifier-board-manual.pdf
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Mine the fan works all the time. It is the chip amp st326 that sends the command. I wrote 5-6 times, sure asked me to send a video. I sent the video 2 times and got no response. This is how the company works. My other amp Sure TAS5613 makes a ploc on a channel when I close it. They also asked me to make a video and film the measurements.
They answer that it is not possible, that the devices are tested before being sent.
They answer that it is not possible, that the devices are tested before being sent.