Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › BLAudio LP-1 high end preamp/headphone amp
New Posts  All Forums:Forum Nav:

BLAudio LP-1 high end preamp/headphone amp - Page 2

post #16 of 21
3/19/06 at 3:19pm
Quote:
Originally Posted by class
It has some high output impedance, that is why Blaudio sugested use 300OHM headphone better.
So you're saying the reason for the recommendation to use high-impedance headphones is actually its already high output impedance (= serial resistance) which calls for a high load impedance not to affect the damping factor and consequentially the electrical frequency response too much. So by introducing additional serial resistors DrArth creates even worse preconditions -- and all this based on a misunderstanding, as it seems.
.
Reply
post #17 of 21
3/20/06 at 2:01am
Thread Starter 
Class: It has some high output impedance, that is why Blaudio sugested use 300 OHM headphone better.

JaZZ: So you're saying the reason for the recommendation to use high-impedance headphones is actually its already high output impedance (= serial resistance) which calls for a high load impedance not to affect the damping factor and consequentially the electrical frequency response too much. So by introducing additional serial resistors DrArth creates even worse preconditions -- and all this based on a misunderstanding, as it seems.

Art: Both my David Hafler DH110 high end preamp and the BLAudio high end preamp, where both have a headphone jack but are designed as preamps first, recommend using headphones of 300 ohm or greater impedance.

You can use a headphone of lesser impedance than 300 ohm, but this may require you to turn up the volume more of the preamp.

I added serial resitance to the headphone's left and right positive leads to increase the impedance of the headphones - not to increase the impedance of the preamp/headphone amp.

The Etymotic 4S (impedance of about 100 ohms) works great with the BLAudio without adding any headphone resistance.

The SA5000 and K701 work also, but the bass is emphasized and the tones are euphonic and bloated more than I prefer, and this effect is more noticeable on the K701 than on the SA5000. Now when I increase the headphone resistance by 75 ohms to these two headphones, it improves them both (but the K701 still sounds more euphonic than the SA5000 but quite good in either case - I tend to slightly prefer the SA50000 here though).

The BLAudio cures any harshness with either the Etymotic 4S or the SA5000 (where adding the Etymotic 4P to 4S converter helps the SA5000).

This may not have any relevance to any other amp - those with ER 4P to 4S converters can experiment for themselves.
Reply
post #18 of 21
3/20/06 at 2:07am
Thread Starter 
[QUOTE=class]
Quote:
Originally Posted by drarthurwells
Art: Actually I get the opposite effect.
JaZZ: You got a strange amp that contradicts every norm.

Class: I uses the LP-1 for 2 years. It is an Actually strange pre-amp. It use 2 pcs 1/4 step-up transformer (1 for 1 chanel) but use a battery-powered driver in the input.
So it is a step-up pre-amp with battery-powered driver. It has some high output impedence, that is why Blaudio sugested use 300 OHM headphone better.
I use it for my Sennheiser 600. Just could say, I like it.
It is transformer pre-amp, it sound soft and silkly, as it's name "LP". The desingner saiid in the cataloge he like the sound of LP much more than the CD.
Art: The new model (BLAudio LP-1 MK II) has 2 improvementes, one is in the input-buffer, and the other is in having 2 rechargable batteries (one used for playing and one as a back up). The LP-1 Model 2 has even better sound than the older LP1, and yes, as you said of either model, it is smooth and silky and sweet - more so than any other headphone amp.
Reply
post #19 of 21
3/20/06 at 4:29am

2 impedance matching ways

Quote:
Originally Posted by drarthurwells
Class: It has some high output impedance, that is why Blaudio sugested use 300 OHM headphone better.

JaZZ: So you're saying the reason for the recommendation to use high-impedance headphones is actually its already high output impedance (= serial resistance) which calls for a high load impedance not to affect the damping factor and consequentially the electrical frequency response too much. So by introducing additional serial resistors DrArth creates even worse preconditions -- and all this based on a misunderstanding, as it seems.

Art: You can use a headphone of lesser impedance than 300 ohm, but this may require you to turn up the volume more of the preamp.

I added serial resitance to the headphone's left and right positive leads to increase the impedance of the headphones - not to increase the impedance of the preamp/headphone amp.
The misunderstanding is the usage of 2 transformer in the LP-1 MK2. Art has correctly understood the high output(or inner) impedance. "added serial resitance" maybe worse in the damping factor, but it is not too bad in the listening effect.
As we know, LP-1 is a step-up output-transformer pre, so we could think about it's impedance matching as the same case in the tube power-amp with output transformer. In this case, the best impedance matching is that the load impedance and the inner imdeance of power-amp is equal. Usually in a transister amp, load impedance is many times of the inner impedance of amp. and the ratio be called as damping factor.
So, in the use of LP-1, we could try two impedance matching ways, one is using it as usally pre-amp and using high load impedance(power amp or a high impedance headphone), other one is using it as a power amp with output transformer and using equal impedance load.
Reply
post #20 of 21
3/20/06 at 7:28am
Quote:
Originally Posted by drarthurwells
I added serial resistance to the headphone's left and right positive leads to increase the impedance of the headphones - not to increase the impedance of the preamp/headphone amp.
This way you in fact increase the serial resistance, not the impedance of the headphone drivers. The latter would only be the case if you spool some more wire onto the voice coils, e.g. if the wire resistance is active part of the drive. Note: the amp's output impedance also primarily consists of and represents a serial resistance. Adding external resistors will just increase it.
.
Reply
post #21 of 21
11/6/07 at 6:55pm
Thread Starter 
Quote:
Originally Posted by JaZZ View Post
This way you in fact increase the serial resistance, not the impedance of the headphone drivers. The latter would only be the case if you spool some more wire onto the voice coils, e.g. if the wire resistance is active part of the drive. Note: the amp's output impedance also primarily consists of and represents a serial resistance. Adding external resistors will just increase it.
.
True, but increasing this resistance changes the ER 4P (30 ohm impedance) to a ER4S (105 ohm impedance) - effectively inscreasing headphone impedance.
Reply
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Headphone Amps (full-size)
Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › BLAudio LP-1 high end preamp/headphone amp