- Thread Starter
- #61
Only 26 pairs left at the $999 price.
Excellent results!Results from products unit:
THD Ratio vs Measured Level
View attachment 46513
THD Level vs Frequency @ 10W
View attachment 46514
64k FFT of 10W 1kHz Output:
View attachment 46516
Ivars,Hello,
this is my first post in ASR, but I was following Amir’s work for some three or four years.
First , many many thanks for those science based measurement things. Second, excuse me for my primitive language, English is my third only language.
After graduating , I spent 7 years in specialised digital/analog academic research in local Technical University in 80’s. Therefore (I hope) I basically understand measurements and technology.
Some months ago, after Amir’s review, I purchased DAC Topping D50s, and that was a good purchase. After that I started to look for new Amp, and decided to test new technologies , the BOSC amp. My idea is to replace McIntosh MC275 MK4 tube amp in my home office. But this is not an easy task , that Amp is real classic piece, one of the best tube Amps for close to 60 years. I simply get tired to replace dysfunctional tubes, and wish to stay more green with less electricity consumption.
And I had suspicion, that maybe small Damping factor of MC275 (about 14) is some problem for my beloved acoustics (Triangle Magellan Concerto with sensitivity 93db, but with wide region with only 2 ohm resistance). What I liked from short specification of that BOSC project, is greater switching frequency (close to 1 mhz) and bigger Damping factor (more than 500), also smaller gain (for today output level 4-7V balanced , no need for gain 26, even 10 is enough).
So I preordered pair from Orchard Audio plus asked for individual measurements for extra 50 USD.
Couple days ago I received DHL package. Everything was in good shape, and I started installing in system. My system is bit unusual : my house is in forest area, and i have lot of short dropouts. Therefore my Home office is supplied with 5KVA Metasystem Megaline online UPS (with THD less than 1%). There are computers connected directly to that, but Audio system is connected through
heavily customized McIntosh isolation transformer (MPC1500). The essence is: Balanced power supply output plus 3-pole LP filter. And good grounding contour outside. That Balanced PS (2x115V, EU 230V) had profoundly impact on PS noise, especially limiting PC SMPS noise.
So MC275 was out, BOSC in.
There was no need to listen much.
Bass region was better controlled, perceptually even louder in lowest region.
Midrange I think the same, HF maybe better may be not. I am 62 , so what HF…
Hiss was close to hearing limit with ear directly in tweeter, remember speaker sensitivity 93db!
Resume, I don’t need to consume more electricity, take care to purchase extra tubes and with weaker bass. New BOSC amps stay in my system, I’m very satisfied with build and performance quality.
Anybody need MC275?…
Second compare I did with ReVox Exception E450 integral amp. Here hiss was for magnitude more
, but with better LF control than MC275. Somehow less clarity in HF. BOSC wins even more.
Some minor things. There is no delay to connect speakers when switching on, so we can hear some minor thump/clik. And when I connected from Bosc output to Velodyne Subwooffer Processor SMS-1 Power input (Parallel to speakers) input dividing resistor literally vaporised with characteristic smell. So after that I connected SMS-1 through linear input… Obviously switching on need some delay relays to speakers.
Some data about Triangle, MC275 and BOSC in pdf.
Overall, new elements and new technology clearly win.
View attachment 47496View attachment 47497
Thank You Leo for excellent Amp!
Ivars M.
To France it will be about $65 to $75 for shipping.could you send these amps to France? What would be the shipping costs?
Looking forward to it.I just finished approving the page proofs for the AudioXpress review. So that should hit the mails and the aether in the next couple of weeks.
I agree, and I believe that especially as a reviewer he should have been more open-minded about what the inline version of the amp tries to achieve. At the end of the review he does mention the more traditional layout.I also think that review now does you a disservice since it spends a lot of time moaning about the inputs being on the front when you also sell a more traditional option that would have suited him.
There is a plot of this in the Orchard Audio website. There is no phase shift till 30kHz.I do have another question, which is: they are mentioned to have "no bass phase shift", but is there any phase shift in the audio band at all? (Sorry if I missed it in an earlier posting of graphs, but I don't recall seeing any phase vs freq graph). It would be nice to see a graph showing the freq range it is phase accurate for.