Goodizzy
Active member
Good afternoon,
I hope everyone is having a pleasant weekend. I have been looking over this pair of circuits as I have a pair of Klangfilm 5K primary OTs for SE use.
I intend to create a stereo version of the Mullard 3-3, but with a shared HT supply from a single PT and rectifier. (I know this will introduce crosstalk but the purpose of the amp isn't for recording and I have all these parts onhand). This is to be used at home, in the library, to power bookshelf speakers at low-medium volume.
I understand the BBC used two copycat circuits of the Mullard 3-3 as shown in the asscociated TI for loudspeakers from the BBC Engineering site. (http://www.bbceng.info/ti/eqpt/AM8_2.pdf)
They have the two circuits labeled Figs. 57 and 57A. Both appear different than the original 3-3 circuit without tone controls.
The instruction differentiates between 57 and 57A as DC-coupled and AC-coupled, respectively. Both circuits also employ RF-rejection networks, as outlined in the TI. The 57 comprising the earlier serials and the 57A, the latter.
As I understand it from the TI regarding loudspeakers, these amps were used in the programme chain as reproduction units in offices, listening rooms and lesser positions in the studio not critical to recording /reproduction fidelity. According to the TI the programme chain is as follows:
Programme input -> Equaliser LS1A/1 -> LS volume control -> AM8/2 amp -> LS
The equaliser in the chain is designed to filter and better match the Goodmans 8" full-ranger drivers employed as loudspeakers. The EQ employs a 1:3.16 transformer prior to the filter.
I guess what I'm failing to understand is why the difference in versions as far as coupling to the output stage is concerned. Is there an advantage between the two versions? Why the switch to AC-coupling in the later serials?
Does the circuit, (at least on paper) with the RF rejection networks, perform better than the original 3-3 circuit? Any other comments on the circuits and their implementation?
I hope everyone is having a pleasant weekend. I have been looking over this pair of circuits as I have a pair of Klangfilm 5K primary OTs for SE use.
I intend to create a stereo version of the Mullard 3-3, but with a shared HT supply from a single PT and rectifier. (I know this will introduce crosstalk but the purpose of the amp isn't for recording and I have all these parts onhand). This is to be used at home, in the library, to power bookshelf speakers at low-medium volume.
I understand the BBC used two copycat circuits of the Mullard 3-3 as shown in the asscociated TI for loudspeakers from the BBC Engineering site. (http://www.bbceng.info/ti/eqpt/AM8_2.pdf)
They have the two circuits labeled Figs. 57 and 57A. Both appear different than the original 3-3 circuit without tone controls.
The instruction differentiates between 57 and 57A as DC-coupled and AC-coupled, respectively. Both circuits also employ RF-rejection networks, as outlined in the TI. The 57 comprising the earlier serials and the 57A, the latter.
As I understand it from the TI regarding loudspeakers, these amps were used in the programme chain as reproduction units in offices, listening rooms and lesser positions in the studio not critical to recording /reproduction fidelity. According to the TI the programme chain is as follows:
Programme input -> Equaliser LS1A/1 -> LS volume control -> AM8/2 amp -> LS
The equaliser in the chain is designed to filter and better match the Goodmans 8" full-ranger drivers employed as loudspeakers. The EQ employs a 1:3.16 transformer prior to the filter.
I guess what I'm failing to understand is why the difference in versions as far as coupling to the output stage is concerned. Is there an advantage between the two versions? Why the switch to AC-coupling in the later serials?
Does the circuit, (at least on paper) with the RF rejection networks, perform better than the original 3-3 circuit? Any other comments on the circuits and their implementation?