two power transformers, LV and HV and HV chokes made by cme hexacom
1638SEA Hammond 10Kohms output transformers
20V heaters and 300V driver stage hammond choke
interstage transformer 126B later connected on
6L6 plate load choke
for better sound
6JE7/EF184 siemens input
6L6GC Svetlana logoC
GM70 Ulyanov graphite plate
two CV32 Mullard MOV HV rectifiers
5C3S Svetlana 300V rectifier
mainly PIO capacitors .
1KV 90mA 30watts 30/22Khz +-1db
1638SEA Hammond 10Kohms output transformers
20V heaters and 300V driver stage hammond choke
interstage transformer 126B later connected on
6L6 plate load choke
for better sound
6JE7/EF184 siemens input
6L6GC Svetlana logoC
GM70 Ulyanov graphite plate
two CV32 Mullard MOV HV rectifiers
5C3S Svetlana 300V rectifier
mainly PIO capacitors .
1KV 90mA 30watts 30/22Khz +-1db
Attachments
actually i get 14V/8ohm so 24,5 watts class A biased a 90mA
but if i push little more bias 16V/8ohm = 32watts
but 90 mA its maximum allowed by Hammond for 1638SEA
so i keep cool. 24W5.
sorry
sound great pics are with interstage transformer coupled, but sound much better capacitor coupled , 1uF 1Kv PIO +0,1uF PIO and transformer like plate load choke for 6L6
but if i push little more bias 16V/8ohm = 32watts
but 90 mA its maximum allowed by Hammond for 1638SEA
so i keep cool. 24W5.
sorry
sound great pics are with interstage transformer coupled, but sound much better capacitor coupled , 1uF 1Kv PIO +0,1uF PIO and transformer like plate load choke for 6L6
6Ej7 input again, this wonderfull tube builded very nice but in triode mode to drive by K40 -9 PIO caps black plate mazda belvu 6l6GC, very similar to rca,with 100H 25mA choke loaded to drive the GM70 by 1Uf 1Kv mgbp pio cap.
the sound its based on choke filter and very few uF by mbgo PIO HT caps,
instead of undred of electrolitics farad to have sound beautyfull, velor creamy mid bass . and the 6L6 can be swapped to get different medium hight ,
NOS SED, Silvanya also sound very nice.
in this amp HT its 875V for 7K output transformer , the GM70 its self biased by 470ohm and ROE 470uF for 100mA
the sound its based on choke filter and very few uF by mbgo PIO HT caps,
instead of undred of electrolitics farad to have sound beautyfull, velor creamy mid bass . and the 6L6 can be swapped to get different medium hight ,
NOS SED, Silvanya also sound very nice.
in this amp HT its 875V for 7K output transformer , the GM70 its self biased by 470ohm and ROE 470uF for 100mA
UL-Style 1015 600V - Flexible - unscreened cables, spiral cables - DDA Ltd.
http://fr.rs-online.com/web/p/fil-de-cablage-electrique/8425514/
AWG16 105° rated 600V spark tested 6K Volts
the first amp get 1100-0-1100Vac
this one 900-0-900Vac and no problem anywere
thanks for the "very nice"
http://fr.rs-online.com/web/p/fil-de-cablage-electrique/8425514/
AWG16 105° rated 600V spark tested 6K Volts
the first amp get 1100-0-1100Vac
this one 900-0-900Vac and no problem anywere
thanks for the "very nice"
Last edited:
i do not wont to discuss desing philosophy ,
just load 6EJ7/EF184 G2 triode connected : Ra10Kohm/ Rk220ohm /+B 250V max
and 6L6GT: La 100H30mA/ Rk 2,7Kohm+470uF/ +B 350V/400V
GM70: TU 7Kohm/ Rg 68Kohm /Rk 2X100ohm on 470ohm 50watts+470uF100V/ +B 850V
for power supply 900-0-900Vac 2X866A +2uF 1K5V oil + 22H300mA +50uF 1KV oil+15H 300mA + 20uF 1KV oil
to built this amp you should have technical experience, lethal voltages do not forgive, so values i give its clear for skilled tech. details by email.
sorry for the bad english
just load 6EJ7/EF184 G2 triode connected : Ra10Kohm/ Rk220ohm /+B 250V max
and 6L6GT: La 100H30mA/ Rk 2,7Kohm+470uF/ +B 350V/400V
GM70: TU 7Kohm/ Rg 68Kohm /Rk 2X100ohm on 470ohm 50watts+470uF100V/ +B 850V
for power supply 900-0-900Vac 2X866A +2uF 1K5V oil + 22H300mA +50uF 1KV oil+15H 300mA + 20uF 1KV oil
to built this amp you should have technical experience, lethal voltages do not forgive, so values i give its clear for skilled tech. details by email.
sorry for the bad english
in the first GM70 SE i made the IT Hammond 126B was supposed to drive the GM70 but i was not satisfied so i connet it like plate choke,
the second amp little economic by plate choke also, but the last one i made i use a really good IT made by Sowter, and bingo this one its wonderfull, and not need the 6L6 driver only 6E6P-E with grig choke and this its my best SE amp.
the power supply also upgraded by oil capacitors and 3 choke like the first one i made,
the second amp little economic by plate choke also, but the last one i made i use a really good IT made by Sowter, and bingo this one its wonderfull, and not need the 6L6 driver only 6E6P-E with grig choke and this its my best SE amp.
the power supply also upgraded by oil capacitors and 3 choke like the first one i made,
I upgraded from a decent pair of LL1635-20mA interstage transformers in my GM70 monoblocks to custom made Monolith Magnetics amorphous core bi-filar wound ITs.
My goal was only A1 operation since the driver is a single triode connected D3A and the available current is insufficient for any significant excursion into A2 land. (I still get 20W which is obscenely loud with my very efficient Onken based system)
Reward was significantly better (flatter) LF response and a rather significant reduction in distortion (I think over 10dB, but memory is unreliable). This single change unmasked a significant amount of detail; And I was surprised.
Message is don't scrimp on the IT, it will be audible.
My goal was only A1 operation since the driver is a single triode connected D3A and the available current is insufficient for any significant excursion into A2 land. (I still get 20W which is obscenely loud with my very efficient Onken based system)
Reward was significantly better (flatter) LF response and a rather significant reduction in distortion (I think over 10dB, but memory is unreliable). This single change unmasked a significant amount of detail; And I was surprised.
Message is don't scrimp on the IT, it will be audible.
1638SEA Hammond
Attachments
My output transformers are not amorphous core, interstage, line stage and SUTs are all amorphous. I'm very happy so far.
The outputs are custom made Electra-Prints and so far I have not found a reason to change them, every "improvement" upstream has been audible.
The 10Y has between 5K and 6K rp and the 211 about 4 - 5K depending on operating point. I was going to theorize that rp was the issue, but I don't think so. Excessive plate current or circuit design?
Yes, the Monolith Magnetics stuff is very good, I'll be buying more in the future.
The outputs are custom made Electra-Prints and so far I have not found a reason to change them, every "improvement" upstream has been audible.
The 10Y has between 5K and 6K rp and the 211 about 4 - 5K depending on operating point. I was going to theorize that rp was the issue, but I don't think so. Excessive plate current or circuit design?
Yes, the Monolith Magnetics stuff is very good, I'll be buying more in the future.
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