Just got this from Ma6Jia

[david watt 0]

 

And also,I planned to get a Ha1a and use this Xiang Sheng as preamp into Ha1a.What do u guys think of this too?

 

I have the 708A- stock IEC is fixed onto the unit. When i tried to use my unit as a preamp, i notice some humming noise from one of the speakers when i crank the volume up to listening levels. I am using DIY GY107 as ICs. Maybe they have fixed this in the B-series?

 

Feedback anyone?

 

[Mackie 0]

Fang: If the enclosed picture is the amp you are referring to, buy with confidence. I've auditioned and unless I'm senile, its build and sound quality gain the same favourable accolades (mine, that is ) as Cayin HA-1A. In fact, I like the Minda's aesthetics better. The tubes used are definitely different from the 6922s in Xcans V3.

 

Ming Da MC66

Edited May 17, 2006 by Mackie

[Mackie 0]

I have the 708A- stock IEC is fixed onto the unit. When i tried to use my unit as a preamp, i notice some humming noise from one of the speakers when i crank the volume up to listening levels. I am using DIY GY107 as ICs. Maybe they have fixed this in the B-series?

 

Feedback anyone?

 

Which power amp did you connect the 708A to? Did you check the imput impedance of the power amp and output impedance of the 708A and calculate the ratio? A ratio of 10 times and more is ideal to bridge the source signal ie. from pre-amp.

 

http://www.tape.com/Bartlett_Articles/impedance.html

 

If the noise comes from one side, remove the chassis cover of the 708A and give the tubes relevant to the troubled channel a slight twiddle. It could fix the problem.

Edited May 16, 2006 by Mackie

[david watt 0]

Hey Mackie

 

I connected the pre-amp to my integrated PM7200 Marantz. How do we check the imput impedance-using the multimeters at the RCA post?

 

When i hooked them up, i adjusted by ear (can't remember where i got these from, but definitely they do not originate from me :

-Source on

-keep the pre-amp at vol zero

-adjust the pot of the Marantz to slightly higher than normal listening level

-turn the pre-amp pot until the music "sounds" louder than what i usually listen at

-turn down the pot of the Marantz to suitable listening levels.

 

I don't connect to the "amp in" but rather to the "CD in" so that i can easily switch amongst my sources. However i use "direct-in" which switches off the tone controls etc.

 

When the music is on, the hum is not very noticeable. It is only when i stop the CD w/o lowering the volume and i move close (ear about 2 feet) to the speakers that i can detect the hum. Is this natural with tubes- there is bound to be some humming?

[neutralzz 0]

When the music is on, the hum is not very noticeable. It is only when i stop the CD w/o lowering the volume and i move close (ear about 2 feet) to the speakers that i can detect the hum. Is this natural with tubes- there is bound to be some humming?

its normal with tube amps.

 

its a huge challenge actually, in eliminating hum. you could probably try to determine the frequency of the hum, i.e 50hz or 60hz.

 

special care has to be taken in shielding the transformers, proper positioning of the signal path, position of the tubes, microphonics of the tubes, etc.

 

its easy to build tube amps even via diy, but its difficult to obtain clean sound at high sensitivities.

[Mackie 0]

I connected the pre-amp to my integrated PM7200 Marantz. How do we check the imput impedance-using the multimeters at the RCA post?

 

Specifications sheet in the manual, if available.

I don't connect to the "amp in" but rather to the "CD in" so that i can easily switch amongst my sources.

 

This is the mistake! Line inputs are for low level line input from sources. However, what you are doing is connecting a pre-amp to the line-in of the Marantz, and the signal is later buffered again at the Marantz pre-amp stage. Although you get your music in the end result, but this method of connection also raises the noise floor inherent with each equipment. I believe the hum will be prevalent even if all equipment in the link is solid-state.

[Mackie 0]

Is there anywhere locally I can check these out? and any rough price range? Im in the market for a cheap amp for my home use...

 

Check with ma6jia, he was the one who brought the amp to the recent forum meet at Anything Audio. It should cost in the S$500 region. If your are looking for a cheaper and yet good alternative, consider XiangSheng 708A/B which costs below S$300. Once again, Ma6Jia is the person to talk to. Pm him.

Edited May 17, 2006 by Mackie

[Mackie 0]

As long as you are looking for Chinese headamps, Ma6Jia is the man. Period!

[david watt 0]

This is the mistake!  Line inputs are for low level line input from sources.  However, what you are doing is connecting a pre-amp to the line-in of the Marantz, and the signal is later buffered again at  the Marantz pre-amp stage.  Although you get your music in the end result, but this method of connection also raises the noise floor inherent with each equipment.  I believe the hum will be prevalent even if all equipment in the link is solid-state.

ok. i will try it out the other way of connecting

[Mackie 0]

Rule of thumb, always connect an outboard pre-amp to the [pre-in/amp-in] sockets of an integrated amp as this will bypass its pre-amp section.

[david watt 0]

Rule of thumb, always connect an outboard pre-amp to the [pre-in/amp-in] sockets of an integrated amp as this will bypass its pre-amp section.

 

I have tried the connection into the pre-in of the integrated. This only bypassed the function of the "source-selection" knob; i still need to use the integrated amp's pot to control the volume and when i crank it up to maximum with my pre-amp at zero volume (but switched on), the hum is very clear from both channels. The hum does not seem to increase as the pre-amp's pot is turned up.

 

All along, source is connected and switched on but without any CD being played.

 

 

What i have done now is to reach a compromise:

Without any music on, adjust the integrated's pot to roughly 9 o'clock when the hum is bearly audible. Play the music and adjust the nett volume using the preamp's pot.

 

 

[Mackie 0]

I just checked the specs sheet of your amp PM7200. It's doesn't allow disintegration of its pre-power stage. In fact, what is offered is a processor-in/out and not a pre-in/out, which means you can connect an outboard processor like a DD/DTS decoder or equalizer to this amp. No matter what, the amp's pre-amp stage is pertetually engaged in operation.

 

The basics remain the same, don't connect a pre-amp to an integrated amp unless it has pre-in/out facilities which essentually disintegrate its inherent pre/power amp stages.

 

In your case, you are introducing an unnecessary link to the line source of your amp via the 708A pre-amp.

Edited May 22, 2006 by Mackie

[david watt 0]

Thanks for the info. I did not know about this difference in processor/pre-amp in/out-puts. LOL

 

i did have my suspicions that the PM7200 cannot function as a true power amp when i cannot seem to defeat the tone controls when using the amp input. In this config, "direct-in" shuts off the sound totally.

 

So for my case i guess i will have to relegate the 708A to function solely as a headamp

[Mackie 0]

did have my suspicions that the PM7200 cannot function as a true power amp when i cannot seem to defeat the tone controls when using the amp input. In this config, "direct-in" shuts off the sound totally

 

I think you are bemused as tone controls is part of the pre-amp stage and hence, not a barometer if an integrated amp can be "disintegrated". Look for pre-in/pre-out jacks with a "U-shaped" connector at the back panel as this confirms the two stages can be split and thus, facilitate connection to other pre-amp or power amp.

Edited May 25, 2006 by Mackie

[edwinywh 0]

 

 

It sound very very warm.. Vocals rule!!!.. Bass got the slaming effect but somehow abit muddy.. Details not that apparant as my Headsave Classic. Maybe they are not fully burn in yet... But i can hear improvement as the time pass.. Going to sleep with my RS-1 tonight...

Hi guys! Me again. To share with u something I really enjoy now.

 

I said earlier in my post I had this amp for my Grados 80.

AFter sometime of listening,one of my 6N11 tubes spoilt,on the left side. The sound out of it it very soft.

So I changed the orignal 6N11 to Siemens E88CC tubes recommended by an uncle in a shop in Bugis.Each cost me $70.

 

I got home and replaced the old tubes.Its easy job to do btw.

 

I'm using my Mac as the source directly into the amp.My music are .wav files.

 

On its first powerup,I let it warm up for around 15mins and I played up music and up the volume.

My first impression of this sounds is.. "WOW!" The music that I listened to now with the new tubes are more detailed,crisp and a larger soundstage! I hear things that I din really noticed before.Its at least a 20% increase in quality sound.

 

I really enjoy my music more now.... =)

 

Next thing I need to do is perhaps upgrade to SR225. What do u guys think?

 

 

Btw,after changing to the new tubes and the better sound,I'm more fasinated by the different tubes in the market and how they sound now. Did a little research and found that Telefunkens sounds really GREAT too!