Firestone Audio - Bobby - Pure-Class-A, Fully Balanced Headphone Amplifier
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Hi All,
The default opamps of the FireStone Audio Bobby Class A fully balanced headphone amplifier are a quartet of OPA604s.
In this year of its 10th anniversary I wanted to see what potential is still in this decade old design by swapping the opamps with a discrete alternative by Sparkos.
I did several listening tests and would like to share my findings with Bobby owners and other readers.
My audio-chain consisted of:
As mentioned earlier Bobby's default opamps are the OPA604 which are ok but are a little veiled and lack some sparkle and detail.
In the past years, after numerous tests, I settled on Burson V5i and OPA627. The V5i giving more transparency, detail and better definition in the bass.
OPA627 was also a very nice upgrade option if you like a warmer fuller sound with subtle highs, detail and a little darker atmosphere.
When I swapped the above with the Sparkos ss3601 I was struck by the positive changes that this upgrade brought, it elevated and transformed the Bobby to a whole new level.
The sound was smooth, natural and very detailed and music was playing effortless and with great authority. Because of the pitchblack background you could hear new small details like subtle decays and get a better sence of space.
Sub-bass
The lowest frequencies are present but not as dominant as with the V5i's. For testing electronic sub bass I often use ‘Doin it Right’ by Daft Punk. With the ss3601 the lowest bass notes are presented with authority and confidence.
Bass
Bass is very punchy and clear. In Radioheads 'House of Cards' the ss3601 had better control and nicely prevented the lowest frequencies from smearing the midbase.
Mids
Male and female vocals sound natural and lifelike without any rough edges. Definition and placement of instruments is very good as can be heard in songs like ‘In Your Eyes’ from Peter Gabriel.
On ‘Man in the long black coat’ the voice of Dylan and his harmonica sound very natural. In my opinion harmonica’s are very challenging instruments to reproduce accurately. (that’s why this is also a good test-track to evaluate the subtle differences in linear power supplies, fuses and power cords)
Highs
The high frequency spectrum is well extended and airy but never sharp or piercing. In ‘I love Paris’ from Johnny Frigo this is nicely demonstrated with a high-hat that sounds very realistic and convincing, with a very nice and long decay.
in short:
The Sparkos ss3601 breathes new life in my Bobby Amplifier and really elevates it to new levels. Clarity, imaging and the richness of sound are second to none I really enjoyed rediscovering my music this way.
The default opamps of the FireStone Audio Bobby Class A fully balanced headphone amplifier are a quartet of OPA604s.
In this year of its 10th anniversary I wanted to see what potential is still in this decade old design by swapping the opamps with a discrete alternative by Sparkos.
I did several listening tests and would like to share my findings with Bobby owners and other readers.
My audio-chain consisted of:
- Qobuz (Hi-res streaming service)
- Roon (running on Synology NAS)
- HQPlayer (running on Intel Nuc12i5) for upsampling and EQ
- Raspberry Pi3 with TeraDak i2s hat running RopiEEE (NAA)
- Firestone Audio Tobby balanced 192k D/A Converter (via Glass Optical Fibre)
- VandenHull Integration Hybrid (single ended) RCA interconnect
- Firestone Audio Bobby Class A (fully balanced) Headphone amplifier
- Beyerdynamic T90 with balanced mod, tuning and custom cable by CustomCansUK2
As mentioned earlier Bobby's default opamps are the OPA604 which are ok but are a little veiled and lack some sparkle and detail.
In the past years, after numerous tests, I settled on Burson V5i and OPA627. The V5i giving more transparency, detail and better definition in the bass.
OPA627 was also a very nice upgrade option if you like a warmer fuller sound with subtle highs, detail and a little darker atmosphere.
When I swapped the above with the Sparkos ss3601 I was struck by the positive changes that this upgrade brought, it elevated and transformed the Bobby to a whole new level.
The sound was smooth, natural and very detailed and music was playing effortless and with great authority. Because of the pitchblack background you could hear new small details like subtle decays and get a better sence of space.
Sub-bass
The lowest frequencies are present but not as dominant as with the V5i's. For testing electronic sub bass I often use ‘Doin it Right’ by Daft Punk. With the ss3601 the lowest bass notes are presented with authority and confidence.
Bass
Bass is very punchy and clear. In Radioheads 'House of Cards' the ss3601 had better control and nicely prevented the lowest frequencies from smearing the midbase.
Mids
Male and female vocals sound natural and lifelike without any rough edges. Definition and placement of instruments is very good as can be heard in songs like ‘In Your Eyes’ from Peter Gabriel.
On ‘Man in the long black coat’ the voice of Dylan and his harmonica sound very natural. In my opinion harmonica’s are very challenging instruments to reproduce accurately. (that’s why this is also a good test-track to evaluate the subtle differences in linear power supplies, fuses and power cords)
Highs
The high frequency spectrum is well extended and airy but never sharp or piercing. In ‘I love Paris’ from Johnny Frigo this is nicely demonstrated with a high-hat that sounds very realistic and convincing, with a very nice and long decay.
in short:
The Sparkos ss3601 breathes new life in my Bobby Amplifier and really elevates it to new levels. Clarity, imaging and the richness of sound are second to none I really enjoyed rediscovering my music this way.
Attachments
Promenadeplatz
Its seems to me quite similar (if not a copy) of an HD53N......
