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-   -   I am planing to build my first Gainclone and require your assistance... (http://www.diyaudio.com/forums/chip-amps/119467-i-am-planing-build-my-first-gainclone-require-your-assistance.html)

Tripmaster 15th March 2008 09:58 AM

I am planing to build my first Gainclone and require your assistance...
 
I am hoping some of you may be able to help. I am new to Gainclones and electronics.

Does any one know if I can buy the Chipamp.com or Audiosector.com PCBs in the UK? It would be easier to follow one of these kits.

I am really keen to make my own PCBs if someone has a simple yet reliable PCB design I could use.

I have purchased some copper boards and intend using the photo glossy paper method.

Which size toroidal transformer will give me the greatest flexibility with future upgrades? I have seen some at http://www.airlinktransformers.com/...ransformers.asp

Which amp configuration will best suit my these speakers?

B&W DM601 S2
Crossover is at 4 kHz, efficiency is rated at 88dB/1W/1m, Impedance is said to be 8 Ohms nominal, 4.3 Ohms minimum
Response 70Hz-20kHz +/- 3dB on axis
Harmonic distortion below 1% 88-20.000 Hz at 90dB SPL at 1m.
Power handling is said to be 25-100W continuous of unclipped programme into 8 Ohms nominal

I really appreciate your help.

andyburlow 15th March 2008 02:49 PM

I have just purchased the chipamp.coms kits from the website - took about a week to arrive to my Cheltenham address from the US.

Yomanze 15th March 2008 03:43 PM

Hi for Toroids in the UK, Try http://www.avellindberg.co.uk/y23_range.htm

Much nicer than Airlink, the 330VA models would be nice for a Gainclone and offer the flexibility to go stereo or dual mono with way more than enough power for your purposes.

My recently ordered Aleph boards from BrianGT got here within a couple of weeks. Both of them are good to deal with and you'll get your kit pretty rapidly. At those prices and the sheer quality of the boards, it's worthwhile to pick something up!

Really like the look of this too: http://dogbreath.de/Chipamps/GainCar...nCardCopy.html

psymo 15th March 2008 07:25 PM

I ordered an LM3875 dual mono premium kit from Audiosector and it arrived in less than a week!

I used this transformer from Airlink, all worked first time and sounds very good.

Regards

Pete

Tripmaster 17th March 2008 03:47 PM

Thanks for the responses so far...

I have ordered the dual mono kit from Chipamp.com today.

How much of a benefit would two toroidal transformers (one for each channel) be compared to just one for both?

What size should I go for if I plan to use two?

Thanks

Tripmaster

Tripmaster 19th March 2008 08:38 AM

Anybody?

Puffin 19th March 2008 09:00 AM

The decision to use one or two tranny's will depend on many things :-

1. What speakers wil you be using 4 or 8 ohm.
2. How sensitive are they
3. How much volume will you need.

If you use one tranny and you are not intending to run it at headbanging levels all night you shoudl be able to use a 300va twin 25v secondary's. Alternatively buy two and run it as dual mono.

Tripmaster 19th March 2008 02:17 PM

Thanks Puffin for your reply

My speakers are B&W DM601 88dB/1M. I have ordered the Chipamp dual mono kit. I wonít be playing my music that loud but would like to have plenty of power in reserve.

AndrewT 20th March 2008 12:13 PM

Hi Trip,
running your B&W speakers from a chipamp is asking a bit much. But it will work.
Let's look at absolute maximum volume on a peak transient.
88db/W/m using a 60W amplifier will generate an SPL of 105.8db/m
At the seating position for a pair of these speakers set 2.5m away, the SPL will be about 100db.

Now reduce the power input to obtain an average listening SPL of 20db below maximum peak and you get a maximum average listening level of 80db at your seat. This is about 5 to 10db above a normal conversation level. I suspect there will be many occasions when you want a higher average level than that.
The result of raising the volume level will be more frequent and more severe clipping of the transients. This makes the sound seemed strained and seem loud even though it is not actually loud. Your brains interprets the clipping distortion as loud.

However, your B&Ws have a very variable impedance and I suggest you design your amp to drive 4ohm speakers resulting in a maximum of 60W into 4ohms (or less if you follow my advice in previous postings).
This will give you about 30W into 8ohm and reduce your average SPL at the listening position from 80db to a maximum of 77db.
Is that good enough for your type of listening. This in part explains why B&W suggest an amp power range of 25W to 100W. This range suits different listener aspirations.

My conclusion to this rambling is that chipamps are suited to high efficiency speakers. Start @ 92db/W/m and maybe even aim for 97db/W/m. Even better if the loading is easy to moderate rather than severe, implying a full range horn loaded driver rather than a complex crossover.

Tripmaster 20th March 2008 02:37 PM

Hi AndrewT

Thanks for that comprehensive reply. Itís not really what I wanted to hear!

Could I improve the performance by mounting 2x3886 chips per channel?

If so how would I achieve this with the dual mono chipamp kit?

Do you have any other suggestions?

Trip


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