By Walkalone@DIYAUDIO
the Telos basically same as Mimesis, except some points:
- LTP Iq is higher, same 4.3mA. The 6V zener of Mimesis instead by LM329 precision low noise 6.9V zener.
- VAS Iq a bit smaller, same 7.8mA for both sides. VAS devices are Zetex transistors, FZT957/FZT857 SOT 223 SMD.
- Individual driver (MJE340/MJE350, but they're KSC2690A/KSA1220A for Telos 5000) for each MOSFET output pair(Exicon ECX10N20/10P20). There are six pairs output per channel.
Based on this info, you can transform Mimesis to Telos.
I've tried both Telos and Mimesis.
No, Goldmund Mimesis's sounding is better.
Goldmund Telos have sound more detail, this's will become ''dirty'' with bad recordings.
The Mimesis have more sweet, smooth. Sound is the game of the balance.
Problem is the quiescent current of LTP.
Telos is 4.6mA, Mimesis 2mA.
-currents mirror of VAS must be balanced of currents. This will get the best result. Matching devices is important. Hfe is good enough.
- Try run VAS's currents as low, no more 6mA per side. High current will get the sounding tighter.
Goldmund Telos run at 3.8mA per side. If you can, you need improve the VAS diff pair, to removing Early effect, more linear by a cascode. I've chosen Hawksford cascode.
Telos sound better Mimesis, more detail.
-LTP's CCS of Telos creates approximately 4.6mA for tail current, this current will be shared by two LTP sides. Load of LTP is 1k5.
VAS use FZT857 and FZT957, they are complementary SOT223. It run quite low current than Mimesis, only 7.7mA per both side.
By Norbert
- Toshiba 2SK134/2SJ49 = Magnatec BUZ900/BUZ905, or BUZ901/BUZ906 (available at Newark, Farnell, eBay, etc.)
- MPSA93/MPSA43 = MPSA92/MPSA42 (available at Newark, Mouser, Farnell, DigiKey, eBay, etc.)
- BD250C/BD249C (available at Newark, Farnell, eBay, etc.)
- BC546B (available at Newark, Mouser, DigiKey,eBay, etc.)
- BC182B (available at Mouser, eBay, etc.)
-2N5565 = 2N5564/2N5566 (available at eBay and a bunch of other places from China online) also, the 2N5566, last I've checked, is available at Home page, you can contact Steve Lagaisse at 760-744-0700 ext. 316 to order them.
- BC556B = (available at Newark, Mouser, DigiKey, eBay, etc.)
- BC449 = MPSA06/BC546B (available at newark, Mouser, DigiKey, eBay, etc.)
1.) Replace T3 (BC546B), T4 (BC546B), T5 (BC182B), and T6 (BC182B) with MPSA42 transistors.
2.) On T6 (the now new MPSA42), short C-B instead of E-B. This can be easily accomplished without any modifications to the PCB. BC182B's leg pin out is CBE and MPSA42's leg pin out is EBC. Simply solder in the new transistor facing the same way.
3.) Bypass the 6V Zener diode with a 1u film capacitor. The capacitor can simply be soldered to the bottom of the PCB without any changes.
4.) Replace R11 (20K) resistor with a 10K resistor.
5.) Change the BIAS resistor R23 (330R) by soldering in parallel a 1K to 1K5 resistor. Goldmund's service manual gives a range here, so if you have used a 1K5 resistor and the MOSFETS are overheating, you'll have to go with the lower 1K resistor value.
This info is directly from Goldmund's service manual. After the changes, the amplifier should perform 100% correctly.
Now everyone can stop crying about the T6 transistor being improperly connected and use an A2 module where C-B is shorted instead of E-B.
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