Q17 - an audiophile approach to perfect sound

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#1,245
#1,247
bloqhed said:
Thanks Tibi, I plan to order soon. I notice that KSC1845FTA and BS250P are on backorder with long lead times, are there alternate parts?
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I have updated documentation on GitHub. Here is a copy/paste:

Selecting alternative parts
With current component shortage, it may happen that some parts listed in BOM to be unavailable, here are few alternative recommendations:
R16 - use a metal film resistor
C7 - use a good polypropylene made by Mundorf, Epcos, Vishay, CDC,
U1 - following opamps can be used and will offer different sonic signatures: LME49710, LME49990, OPA604, OPA134, NE5534. Do not use TL071, TL081, LM301, LM741.
Q2 and Q3 - use transistors with Vce >= 65V & hFE>=100 : 2N5401 / 2N5550
Q7 and Q12 - other transistors that may be used are: KSC1845, 2N4401, BC546 / BC547 / BC548 / BC549 / BC550 - use the one with A termination for Q7 and C termination for Q12.
C1 - this must be silver-mica or at least polystyrene.
Q1- KSA992, 2N4403, BC556C, BC557C, BC558C, BC559C, and BC560C
C10 - silver-mica or ceramic NP0
R26, R27, R28 - these must be non-inductive resistors. MILLS make some good ones.
C17 - in this order: polystyrene, teflon, foil polypropilene, metalised polypropylene.
Q5 and Q6 - following pair replacements may be used with excellent performance: FQP3P50/FQP4N80; FQP4P40/FQP5N60
Q15,Q16,Q17,Q18 - following pairs can be used with modest performance IRFP9240/IRFP240; 2SJ201/2SK1530; 2SJ118/2SK413; 2SJ119/2SK414.

Instead BS250 you may use ZVP3306A

When you use any replacement, please take care on part pinout.


Regards,
Tibi
 
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#1,249
tvicol said:
Hi Ed,

It will perform better ? For sure, Yes.
It will sound better ? Maybe, because depends on your source, your cabling, your room etc.
Adding more output devices will decrease amplifier output impedance and therefore increase amplifier capability to deliver more current in a low impedance.
Adding more output devices will make amplifier "more powerful" at lower impedances and increase his capability to drive complex audiophile speakers , including ESL.
For example at same +/-50V and 1KHz, an amplifier (here I do not talk about Q17) may have:
1. With one pair
- 100W in 8ohm
- 120W in 4 ohm
- 120W in 2 ohm

2. With two pairs
- 100W in 8ohm
- 180W in 4ohm
- 300W in 2 ohm

Having an amplifier with very low output impedance make sense even you have small bookshelf speakers.
Q17 achieve this by using high transconductance mosfets. One pair already drive a wide range of speakers very well. Two pairs is for audiophiles who look for the best at given price.


Regards,
Tibi
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Tibi,
What is the maximum power that can be obtained from this amplifier, in a bridge connection at a supply voltage of +-50 volts (speakers of 4 ohms)? Of course, in this case, two pairs of output transistors are used.
 
#1,250
Hey there, i am planning on building my first amp and this seems to be a nice project. I have heard once the original and was quite impressed, so i can't wait to listen this little beast !
Approximately, How much would it cost for the total project, psu/main board and an enclosure ?
Also, i cannot find the link for the mouser psu project buying list !
 
#1,257
The best way is to order transformer directly at manufacturer.
For my projects I order at https://petra-toroid.ro/?lang=en they ship worldwide.
How to order:
  • go to https://petra-toroid.ro/contact/?lang=en use form or email
  • mention that you want to order one or two 300VA trafo
  • primary 115Vac or 230Vac, depending on the mains voltage in your region
  • 2 separate 36Vac secondaries
  • optional magnetic shielding
  • mention that application will be for audio


If your mains are 220-240Vac, you may order a trafo here https://www.audiophonics.fr/en/toroidal-transformers/toroidal-transformer-300va-2x38v-p-5548.html

Regards,
Tibi
 
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#1,260
Yes, you need to multiple the order with the number of boards. On mouser page see top right corner. For 12+1 multichannel you need 13. 😎
Screenshot 2022-05-27 at 08.09.44.png


For other documents check your mail.

Regards,
Tibi
 
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