Jhofland designed a nifty little diamond buffer that I got to try out for the past week. It works superbly and can drive 32ohm headphones with ease. It perfectly mates with a BTSB or a HyperSET hybrid tube buffer as the voltage gain stage. Jhofland had graciously allowed me to use his design and make it available as a preassembled ready to run run (RTR) board.
More info on HyperSET here:
https://www.diyaudio.com/community/threads/btsb-with-tube-buffer-hyperset-gb.396848/
Diamond buffer schematic:
PCBA render:
Prototype under testing:
I’ll let Jhofland provide the particulars of the circuit but I do know it is Class AB and uses an LED to set the current sources. It’s an all BJT design and can take +/-12v to +/-20v (tested). Probably can go higher even.
More info on HyperSET here:
https://www.diyaudio.com/community/threads/btsb-with-tube-buffer-hyperset-gb.396848/
Diamond buffer schematic:
PCBA render:
Prototype under testing:
I’ll let Jhofland provide the particulars of the circuit but I do know it is Class AB and uses an LED to set the current sources. It’s an all BJT design and can take +/-12v to +/-20v (tested). Probably can go higher even.
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HyperSET is a basically a BTSB with a SET tube buffer in between. There is provision for external relay select to enable tube buffer or a pass through all solid state mode. Usual selectable gains 0/6/14/20dB. Simultaneous single ended and balanced output. Plus built in open collector logic for controlling enable/standby on a connected amp to allow graceful startup and shutdown. There is a built in SSR relay shunt to prevent turn on and off pops. Also there is an included helper board for an optional external pot to turn this into a full blown preamp. More info here:
https://www.diyaudio.com/community/threads/btsb-with-tube-buffer-hyperset-gb.396848/
Fully assembled, tested and RTR and comes with matched NOS Russian 6N1P tubes. You can use your own E88CC or 6DJ8 tubes if you like to tube roll but the 6N1P’s sound great and are super robust. Just add 12v 2A PSU, connect audio in and out and toggle SPDT switch for remote enable/standby. Pricing is $325 and includes full set of (12 Molex KK) connectors for all inputs/outputs.
https://www.etsy.com/listing/147415...51499&click_sum=25f8d549&ref=shop_home_recs_3
There is a BTSB Lite panel mount that provides XLR and RCA inputs with relay auto select (balanced input priority). That board is a perfect mate for the HyperSET. And of course, the Diamond buffer used with the HyperSET makes for an awesome headphone amp or if you need to drive low impedance line loads.
https://www.etsy.com/listing/123869...0844&click_sum=92daf381&ref=shop_home_recs_13
https://www.diyaudio.com/community/threads/btsb-with-tube-buffer-hyperset-gb.396848/
Fully assembled, tested and RTR and comes with matched NOS Russian 6N1P tubes. You can use your own E88CC or 6DJ8 tubes if you like to tube roll but the 6N1P’s sound great and are super robust. Just add 12v 2A PSU, connect audio in and out and toggle SPDT switch for remote enable/standby. Pricing is $325 and includes full set of (12 Molex KK) connectors for all inputs/outputs.
https://www.etsy.com/listing/147415...51499&click_sum=25f8d549&ref=shop_home_recs_3
There is a BTSB Lite panel mount that provides XLR and RCA inputs with relay auto select (balanced input priority). That board is a perfect mate for the HyperSET. And of course, the Diamond buffer used with the HyperSET makes for an awesome headphone amp or if you need to drive low impedance line loads.
https://www.etsy.com/listing/123869...0844&click_sum=92daf381&ref=shop_home_recs_13
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I am thinking these diamond buffers are so small, a pair of them might work well in an Altoids tin headphone amp called the “Pocket Diamond Buffer” (PDB) amp. We will add an opamp (probably OPA1642) to provide 12dB gain and put the buffer in the feedback loop and the DC offset would be nil. Running on +/-9v rails from two 9v batteries.
Sort of like this:
Sort of like this:
I finally had some time for some LTSpice doodling. I increased quiescent current in outputs to 43mA and in input stage to 7mA (from 1mA). Here is new schematic. Dissipation in the outputs is combined 760mW so probably will need thermal pad to chassis floor or small extruded heatsink.
As a preamp driving 5.65Vpp into 5kohms, it excels providing 0.000034% THD and harmonic profile that is second order dominant:
For 1W into 32ohms, that’s 5.65Vpp and THD is 0.11% but harmonic profile is still monotonically descending:
It’s able to drive 1.0Vpp into 32ohm load (4mW) (headphones) at 0.0007% THD
On 94dB/mW headphones this is 100dB. More than loud enough for most listening.
I think this is looking pretty good now.
As a preamp driving 5.65Vpp into 5kohms, it excels providing 0.000034% THD and harmonic profile that is second order dominant:
For 1W into 32ohms, that’s 5.65Vpp and THD is 0.11% but harmonic profile is still monotonically descending:
It’s able to drive 1.0Vpp into 32ohm load (4mW) (headphones) at 0.0007% THD
On 94dB/mW headphones this is 100dB. More than loud enough for most listening.
I think this is looking pretty good now.
I have ordered the small mono line level preamp Diamond Buffers (Class AB) for the shop plus some pre-production samples of the Pocket Diamond Buffer headphone amp (Class A for use with +/-9v battery power supplies). Will test them out once they arrive. Here is a placement check render:
The production assembled Diamond Buffer has boards have arrived. They look great. I need to test one to make sure it all works like the pre-production boards that I received.
I will offer these Ready to Run (RTR) fully assembled boards for sale in my shop for $59/pair. Just need to connect to power source and provide input and output and you are good to go. They were designed for +/-15v power supplies but can work from +/-12 to +/-20v (tested). You can either solder flying lead wires directly or use 2 and 4 pin JST headers and connectors.
I will offer these Ready to Run (RTR) fully assembled boards for sale in my shop for $59/pair. Just need to connect to power source and provide input and output and you are good to go. They were designed for +/-15v power supplies but can work from +/-12 to +/-20v (tested). You can either solder flying lead wires directly or use 2 and 4 pin JST headers and connectors.
In the spirit of the holiday season, I will be giving these fully assembled diamond buffers away for free (1 pair per member, while supplies last and you need to pay for shipping per my Etsy shop). You can sign up here:
https://www.diyaudio.com/community/threads/jhoflands-diamond-buffer-gb.401244/
https://www.diyaudio.com/community/threads/jhoflands-diamond-buffer-gb.401244/
The Desktop Diamond Buffer works! I didn’t have any TTA004/TTC004 or BD140/BD139 on hand so I used NOS Toshiba 2SC4793/2SA1837 (arguably, the finest audio BJTs ever made), but they are BCE vs ECB so I mounted them underneath the board with some tall stand-off legs. I am using a cheap DCDC converter to make +/-12v (unregulated and poorly filtered) so there is some residual PSU noise. But it confirms the circuit is operating properly. Bias current at 12v and with the Toshibas is only 22mA vs the nominal 40mA we had I designed for. I have placed an order for the missing parts including the proper 0deg RK09 Alps pot.
Here is the setup driving HE400i (32ohm) planar magnetics.
Closeup of the board with TH parts installed. Lots of room for boutique film caps on the input. The opamp has a lot of clearance for those who like to swap out. Ideally, OPA1642 would be superior here but assembly house only had NE5532 in stock.
Heatsinks are barely warm with each heatsink dissipating only about 500mW at idle.
Here is the setup driving HE400i (32ohm) planar magnetics.
Closeup of the board with TH parts installed. Lots of room for boutique film caps on the input. The opamp has a lot of clearance for those who like to swap out. Ideally, OPA1642 would be superior here but assembly house only had NE5532 in stock.
Heatsinks are barely warm with each heatsink dissipating only about 500mW at idle.
For those who missed the Xmas Diamond Buffer giveaway, you can buy them from my shop for $39/pair.
I just tested them today and it checks out great. Bias current is about 14mA in the output stage and the DC offset is only a few mV. They have the correct green LED installed this time and upgraded FZT853/953 output BJTs.
You can get them in my shop here:
https://xrkaudio.etsy.com/listing/1619024473
I just tested them today and it checks out great. Bias current is about 14mA in the output stage and the DC offset is only a few mV. They have the correct green LED installed this time and upgraded FZT853/953 output BJTs.
You can get them in my shop here:
https://xrkaudio.etsy.com/listing/1619024473
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I have had requests from several members wishing to convert the postage stamp Diamond Buffer to a headphone amp. I do want to caution you that the DC bias current setpoints are not ideal for this, even if you change the emitter resistors on the outputs to something smaller.
Here are the mods needed if you want to transform these boards to headphone amp duty. Keep in mind that this will require heatsinking of the boards or the output transistors. They will get quite hot.
Note that on the Pocket Diamond Buffer and Desktop Diamond Buffer HPA’s, the output stage has an extra RC snubber across the base drives, and the LED bias is set at R7 with a 10k resistor to GND. In the small postage stamp line level Diamond Buffer, the LED bias is set by the top rail and not GND so R7 should be 22k. This configuration in practice seems to have about 40mA of bias current so if running +/-15v rails, you will have about 1.2W total dissipation. A small aluminum heatsink like that used on GPU coolers with some silicone thermal spacer and a clamp can work. Also effective but not pretty is to use RTV silicone to bond the heatsink directly on top of the outputs and emitter resistor. If heatsinking from bottom side, take care to insulate the connector pin protrusions.
All the resistors in red need to be swapped out and you can keep the ones in blue. So 9 parts. They are easy to change if you are handy with SMT and hot air rework station.
Here are the mods needed if you want to transform these boards to headphone amp duty. Keep in mind that this will require heatsinking of the boards or the output transistors. They will get quite hot.
Note that on the Pocket Diamond Buffer and Desktop Diamond Buffer HPA’s, the output stage has an extra RC snubber across the base drives, and the LED bias is set at R7 with a 10k resistor to GND. In the small postage stamp line level Diamond Buffer, the LED bias is set by the top rail and not GND so R7 should be 22k. This configuration in practice seems to have about 40mA of bias current so if running +/-15v rails, you will have about 1.2W total dissipation. A small aluminum heatsink like that used on GPU coolers with some silicone thermal spacer and a clamp can work. Also effective but not pretty is to use RTV silicone to bond the heatsink directly on top of the outputs and emitter resistor. If heatsinking from bottom side, take care to insulate the connector pin protrusions.
All the resistors in red need to be swapped out and you can keep the ones in blue. So 9 parts. They are easy to change if you are handy with SMT and hot air rework station.
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