Review and Measurements of Accuphase E-270 Amplifier

[restorer-john]

Is the headphone amp on this an add on op-amp chip on the preamp, or is it taken off the power amp?

It apparently has a separate amplifier for cans. Probably a low impedance gain/buffer stage parallel to the pre-amp out.

This is a good idea with an integrated amplifier as the power stage residual noise would otherwise be audible in sensitive headphones. Also, typical vintage implementations use medium value (220-2kohm+) resistors (4) to safely drop the massive voltages (and consequent power) of a power amplifier stage. Trouble is, those resistors create a very high source impedance with subsequent changes to the FR of the connected cans.

The old Sony VFET amps had great headphone amps that were part of the amplifier circuitry.

The Sony VFET series, TA-3650, 4650, 5650 and 8650 all implement headphones as I outlined above. Here is the 8650's connection and they are all essentially identical.

 

[DDF]

I don’t know if Amir has tested any Bryston products. The certainly give a good impression on soundquality were I’ve heard them. If I am not mistanken they have a 20 Year Warranty which should indicate no reliability issues.

Listening to a 30 year old Bryston 2B LP Pro right now. Still sounds great. Bryston sent me free power supply caps after mine got weary @ ~ 20 yrs old. Amazing customer service, eh? Its back in the system after my 1.5 yr old Nuprime IDA-8 died.

 

[restorer-john]

Bryston sent me free power supply caps after mine got weary @ ~ 20 yrs old.

That's great customer service. Nice to know they care for their customers.

 

[DonH56]

So did I. 50Hz in Australia.

I sooo wanted to make some crack about things being a little slower Down Under but decided to refrain... )

I made a couple or three amplifiers using VFETs, Siliconix I think? Worked "ok" as Amir would say.

Bryston has been on my short list forever. I just missed picking up a nine year old 14B-SST2 offered on another forum -- too busy working and shoveling snow and missed it. Oh well, saved me a few bucks, and wouldn't fit where my current amp lives anyway.

 

[Blumlein 88]

I made my own ribbon headphones once. Used a Mosfet amp stage directly connected to strips of ribbon running along between some strong bar magnets. Think over-sized ribbon microphones. Mosfet amps because unlike bipolar transistors they wouldn't instantly fry themselves when connected across a bit of aluminum foil. (I had attached some mylar kitchen wrap to some kitchen foil). I was amazed how good they were. Not being aware of expensive audio gear I abandoned the project. Who wanted fragile headphones no matter the sound if you need 60 wpc to play them?

I could have been a pioneer ahead of the times.

But yes, the old receivers and integrateds just connected the output stage thru some 220 ohm or similar resistors to the phones.

 

[restorer-john]

I sooo wanted to make some crack about things being a little slower Down Under but decided to refrain... )

That would be quite appropriate in this case. I should have seen it. Our rectifier spikes sit nicely on graticule lines here.

-- too busy working and shoveling snow and missed it.

And here I am, hiding inside in the air-conditioning because it 35 degrees (95F) outside. The world is a funny place eh?

 

[DDF]

That's great customer service. Nice to know they care for their customers.

We used them at work and their support was always A+. I still have an original first gen 2B from (guessing) 40 yrs ago and it still works just fine. These things are tanks!

 

[restorer-john]

I could have been a pioneer ahead of the times.

A Pioneer. A-Head of the times.

Here's your brand "Way Ahead"
First product "Blue Ribbon" (Blue Riband) (taken from the title for the highest speed crossing of the Atlantic by passenger ships) Ribbons are fast.

Your low cost sub brand for the kids can be "Streets Ahead". Specializing in hip grafitti covered headphones sporting bluetooth and heaps of bass.

Sell them all to Apple for a few billion $ down the track.

 

[DDF]

Bryston has been on my short list forever. I just missed picking up a nine year old 14B-SST2 offered on another forum

At the risk of raspberries, I think the SST2 design is where Bryston really hit their stride with open and awesome sounding amps.

 

[Jaimo]

I have 8 ohm load but have not had time to connect it up. I also worry about length of testing when I start to include another load.

Hi Amir, what load do you use for testing. Any LRC details?

 

[Jaimo]

At the risk of raspberries, I think the SST2 design is where Bryston really hit their stride with open and awesome sounding amps.

I had a 4B-ST for many years before switching to tube power amps. Without suggesting that my tube amps measure better, I suspect that there are issues with Brystons that cursory bench measurements don't pick up. I 'd be most interested to see how a 4b-st or sst measure on Amir's Test bench.

 

[amirm]

Hi Amir, what load do you use for testing. Any LRC details?

It is the classic ebay special type loads:

For 4 ohm I have two of the 2 om versions in parallel. I will characterize it when I get a chance.

 

[Jaimo]

It is the classic ebay special type loads:

For 4 ohm I have two of the 2 om versions in parallel. I will characterize it when I get a chance.

I have used pretty much the same loads with the knowledge that this does not approximate a true (bad) speaker load. It's worth opening a new thread to discuss what a good standard load should look like. Here's a reference for starters...Prosound Training link

 

[andreasmaaan]

No one listens at just 1 watt

Really? 1 watt is about 86dB/1m on an average speaker. Add a second speaker, increase the listening distance to a typical 2-4m, and account for room reflections, and I dare say 1W RMS is about as close to average listening levels (if not in fact louder) as you’re likely to get...

 

[amirm]

Really? 1 watt is about 86dB/1m on an average speaker. Add a second speaker, increase the listening distance to a typical 2-4m, and account for room reflections, and I dare say 1W RMS is about as close to average listening levels (if not in fact louder) as you’re likely to get...

You are talking to someone who doesn't trust speaker sensitivity as much as he can throw it. I can also make amplifiers with tens of watts easily distort. 1 Watt is OK if you have super efficient speakers and don't listen to bass.

 

[andreasmaaan]

You are talking to someone who doesn't trust speaker sensitivity as much as he can throw it. I can also make amplifiers with tens of watts easily distort. 1 Watt is OK if you have super efficient speakers and don't listen to bass.

The 86dB figure is based on stereophile’s long-term measured average. Manufacturers usually spec at closer to 90dB IME.

Also, I’m not proposing 1W as a peak power requirement! I’m saying most of us are probably listening at the equivalent of about 1W RMS most of the time.

 

[HammerSandwich]

Note that Stereophile's average represents sensitivity at 2.8Vrms, not 1W. I'd bet the same for a lot of the "90dB" speakers out there as well.

Anyone else wish that dBW had won this fight?

 

[amirm]

The 86dB figure is based on stereophile’s long-term measured average. Manufacturers usually spec at closer to 90dB IME.

Happy to quote stereophile:

That is 20 watts. Not 1 watt.

Also, I’m not proposing 1W as a peak power requirement! I’m saying most of us are probably listening at the equivalent of about 1W RMS most of the time.

This has been often said but it is not correct. The trend in modern speakers is small enclosures which reduces efficiency. You need lots and lots of power.

 

[andreasmaaan]

Happy to quote stereophile:

View attachment 21712

That is 20 watts. Not 1 watt.


This has been often said but it is not correct. The trend in modern speakers is small enclosures which reduces efficiency. You need lots and lots of power.

I think we're just at cross-purposes here. I wasn't trying to suggest that we don't need more than one watt. I was suggesting that 1W is about as much power as we're using most of the time.

Anyway, carry on

 

[DDF]

Here's a reference for starters...Prosound Training link

OK for emulating a driver; taking the next step to a speaker system emulation:
https://www.stereophile.com/reference/60