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Old 20th June 2004, 12:53 AM   #31
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I may need a a pair to compair to my CCS miniA HP amp.
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Old 21st June 2004, 03:36 AM   #32
digi01 is offline digi01  China
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Please notice:
the R/C kit not including dual-mono main amp PCB boards,only 2 bread boards for power supply parts building.
so,the all parts kit (amp boards+R/C kit) cost is $47.2 USD.
and in psu parts,it has a couple of ELNA standard 6800u50v caps for dual mono psu building,but not 4 caps.sorry for my mistakes.

for Brian Donaldson
I am very interest in compare ZEN & alpha.in fact,I am making a minia headamp nowwaiting your test result.

-digi
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Old 21st June 2004, 07:12 AM   #33
digi01 is offline digi01  China
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for metalman
thanks for you share your circuit debug course on forums,it is cool I agree with you point,the circuit definitely performances from tweaks.P2P or PCB mounting mode,can all adjust to very good performance.

supplement some improve sound quality modification idaes:
1,match R10 and R12,obtain stability DC work point.
2,use dual mono building, separate common ground.
3,choose top grade components.such as use 100uf/35v BP cap for C3.
4,adjust amp gain setting, you can check out this thread for some detail:Battery Powered Zen Headphone Amp
5,use battery power.or improve psu voltage,my ZEN run at 35V pre channel 200ma bias.
as Pellerano mentiond,the amplifier is quite sensitive to component quality. Q1 and Q2 are critical.IR or Motorola brand IRF610 is good.2sk214 is another choice,but need testify.

btw,you setting the bias at 0.3A.what headphone are you useing?


regards
-digi
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Old 21st June 2004, 05:08 PM   #34
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Digi01,

I am using Grado Labs SR-225 headphones, which have a 32 ohm impedance. I am running 30V and 0.3A bias to optimize the amp power output into my headphones, 1.44W into 32ohms. This works out to 138dB max volume, which means that I should never hear it start clipping.

Thanks for the link on setting the gain. I may have to play around to see how different gain settings affect the sound.

Metalman
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Old 22nd June 2004, 09:57 AM   #35
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Digi01,
Have you or anyone else compared this amp to a PPA? I have a PPA right now, but am very interested in trying this one out if it is very competitive. Also, do you still have some kits left? Thanks.

--Ferdi
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Old 23rd June 2004, 02:40 AM   #36
digi01 is offline digi01  China
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Quote:
Originally posted by ftjandra
Digi01,
Have you or anyone else compared this amp to a PPA? I have a PPA right now, but am very interested in trying this one out if it is very competitive. Also, do you still have some kits left? Thanks.

--Ferdi
the sound of ZEN is very nature,especially in grado series headphone load.I like use it enjoy the vocal and jazz music,only beautiful
I have 6 kit left now,you may give me a mail order it.

-digi
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Old 14th July 2004, 06:13 AM   #37
digi01 is offline digi01  China
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Quote:
Originally posted by Brian Donaldson
I may need a a pair to compair to my CCS miniA HP amp.
Hi Brian,your e-mail host maybe have some problem.please give me a mail
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Old 15th July 2004, 12:25 AM   #38
digi01 is offline digi01  China
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Brian,I still can't send you a mail.mail delivery failed
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Old 12th September 2004, 12:15 AM   #39
Kram is offline Kram  United Kingdom
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Hello,

I have just started testing my circuit after soldering all the components to Digi01s PCB.

I was aiming for a bias current of 300mA but all i seem to be able to achieve is 192mA (0.58V/3).

Here are some measurements that i took

24.8V supply
V R18 = 1.1
V r2 = 3.5
Q3 (ZTX450) B= 12.1, C = 16.8, E = 11.6
Vbe = 0.54
Q2, G = 5.2, D = 11.6, S = 0.58
Q1, G = 16.7, D = 24.1, S = 12.1

can anyone see if anything is wrong from these values?

Also I tried to set the Id(Q1)/Id(Q2) ratio the way tortello suggests on the Headwize site but cant seem to do it correctly.

Tortello's tutorial says to measure the AC contribution across R10 and R12 whilst applying a 1kHz input.
If i connect my scope probe across R10 with the probe ground at one side of R10 and probe at the other end I dont get a proper reading. If i connect the probe between Q1 source and R10 with the probe ground at ground i get a nice sine wave.

When i connect the probe across R12 I dont get any signal no matter how much i adjust R17.

Is this normal or is there something wrong.

Thanks for any help
Mark
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Old 12th September 2004, 04:09 PM   #40
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Mark,

Lets tackle the bias issue first. Could you measure and post the voltages across R4, R16, R3 and R10. R4 and R16 will have the biggest affect on the bias current here. It may not be possible to get 300mA bias with them in the circuit. At first glance, your other numbers seem OK, but I'll check a little closer.

In my amp I had to remove them to get the bias up to 300mA, but in that case you have to add an extra capacitor in the bias circuit to maintain stability.

Start by measuring and posting those values and we'll go from there. Just so you know, I've benn pretty busy lately, so I may be a little sluggish in replying promptly.

Terry
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