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Old 17th April 2021, 06:32 PM   #2971
woody is offline woody
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For those of us not needing every last watt this design is capable of might not the voltage gain stage from the new Sony Vfet amp be a nice option. DIY Sony VFET pt 1
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Old 17th April 2021, 06:50 PM   #2972
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by RogerCl View Post
Two loudspeakers are currently in the planning stage:

- 4-way open baffle as a replica of the LX521 by Linkwitz.
- 2-way tweeter horn with bass in BR cabinet or CB activ equalised.

The music signal comes via audio PC and 8-channel audio interface. The speakers are actively separated via Acourate software.

Both speakers will be placed in the same room and driven by the same amplifiers.

The 18sound compression driver in the tweeter horn delivers 110dB and here I see the MoFo with its low noise as the solution. Best sound is added. The tweeters of the LX521 should also get their signal from the MoFo.

I want to supply the tweeter with the MoFo, which, if I understand this correctly, passes on the volume from the preamplifier 1:1.

I would like to solve all other frequency ranges via TPA3255 (class D) which amplifies the signal with a certain gain factor.

I will save different setups (crossover frequency, time delay and level) separately for both speakers in the Acourate setup.

Is it possible to synchronise this combination of MoFo and TPA3255 so that the volume change is synchronised for both types of amplifier?
Good choice for Class D amp. The standard issue TPA3255 has 22dB gain. The ones with PFFB have 16dB gain. The MoFo has 0dB gain. You will need some sort of preamp for MoFo with similar gain as the TPA3255. If using a DSP as XO to control all of this, changing a master volume will affect all in unison. However, a DSP will not be able to drive the MoFo to levels high enough to match your mids and woofers.

Assuming you want to be able to hit the typical 11w max power from a MoFo into 8ohms, you need sqrt(11v x 8ohms)=9.4vrms or 24Vpp. Any opamp based preamp with +/-15v rails and circa 22dB gain should be able to do this. Use that in between the DSP output and the MoFo.

The TPA3255 can also use a preamp as most sources have a hard time reaching clip with a 22dB gain. Also, the TPA3255 likes to see balanced input. So ideally you want a 6dB gain balanced output preamp to reach typical 28dB needed for most sources to hit max. In that case, the preamp for MoFo should be 28dB or so. Within the DSP you can make +/-6dB adjustments to dial in the relative balance of the woofer/mid/tweeter.

It goes without saying that to do this right you need a calibrated microphone and software like REW.
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Old 28th April 2021, 07:56 AM   #2973
audiodesignguide3 is offline audiodesignguide3
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After the good result obtain with EF180 instead of 6072A in Power Follower I am using now a new driver for the Inpol / Mofo using the 6Z51P.


The 6Z51P is near to the D3a and it is tested on the article of Bartola about russian pentode.


I will update you on result.




Attached Images
File Type: jpg E180F_driver_sch.jpg (130.6 KB, 1007 views)
File Type: jpg E180F_driver_pcb.jpg (280.1 KB, 980 views)

Last edited by audiodesignguide3; 28th April 2021 at 08:09 AM.
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Old 30th April 2021, 05:35 PM   #2974
audiodesignguide3 is offline audiodesignguide3
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Quote:
Originally Posted by audiodesignguide3 View Post
The 6Z51P is near to the D3a and it is tested on the article of Bartola about russian pentode.

The sound is very good with the 6Z51P but remember to change the pins on socket because are different from D3a and EF180


I have use 290V, 4x39K 2W on anode and 100ohm on cathode with 470uF



I can share pcb files and the complete components list
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Old 7th May 2021, 05:31 AM   #2975
audiodesignguide3 is offline audiodesignguide3
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Quote:
Originally Posted by audiodesignguide3 View Post
I can share pcb files and the complete components list

Here the pcb, some little modifications are necessary to use the 6Z51P instead of D3a / E180F
Attached Images
File Type: jpg mod_6Z51P.jpg (146.3 KB, 812 views)
Attached Files
File Type: zip ver11a_2021-03-18.zip (115.9 KB, 25 views)
File Type: zip Inpol_ver10.zip (115.0 KB, 14 views)
File Type: zip MBR40250A.zip (10.5 KB, 14 views)

Last edited by audiodesignguide3; 7th May 2021 at 05:35 AM.
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Old 7th June 2021, 09:51 AM   #2976
audiodesignguide3 is offline audiodesignguide3
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In my case the 6Z51P have too much voltage gain so I have used the 6Z9P-E (same pcb without mods)


about 40W 1.5% thd and 148Khz at -3dB
Attached Images
File Type: jpg 6Z9P_8K25ohm_100ohm_06Vin_17Vout_8ohm_thd.jpg (96.5 KB, 588 views)

Last edited by audiodesignguide3; 7th June 2021 at 09:56 AM.
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Old 7th June 2021, 03:00 PM   #2977
mindutis is offline mindutis  Sweden
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Would be awesome if you could share the component values also.
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Old 7th June 2021, 05:20 PM   #2978
audiodesignguide3 is offline audiodesignguide3
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Quote:
Originally Posted by mindutis View Post
Would be awesome if you could share the component values also.



Current amplifier stage



R1,R2,R4,R5 1800ohm 1/4W 1%
R3 10Kohm 2W
R6,R7 220K 1/4W 1%
R9,R11 0.22ohm 5W Mills RMA5

C1 4700uF 16V Nichicon model UKA1C472MHD
U$1 0.68uF 400V Clarity Cap CMR or other audio grade MKP

R8 10Kohm multi turn

Q1,Q2 IRFP240PBF (it would be desirable to make a selection based on current)

D1,D2 zener 15V 1W
D3 zener 10V 1W
F1 fuse 10A FAST with fuse holder Mouser 534-4628

Cout min. 10000uF 50V Nichicon KG Mouser

Isolators Bergquist SP400-0.007-00-104 RS RS541-0856



Voltage amplifier



R1,R2,R18,R19 22Kohm 1/2W 1%
R3,R4,R20,R21 2200ohm 1/4W 1%
R5,R6,R8,R9,
R10,R26,R22,R23 39Kohm 2W
R7,R24 100ohm 1/4W 1%
R37,R39 47ohm 1/4W 1%
R11,R34 4700ohm 1/4W 1%
R12,R30 2 x 100Kohm 1/4W 1% to have 200K
R13,R28 4700ohm 1/4W 1%
R14,R29 150Kohm 3W
R17,R33 3.3ohm 2W
R25,R35 0ohm
R15,R16,R31,R32 220ohm 1/4W 1%

C1.C3 220uF 6.3V
C2,C4 33uF 400V
C5,C6 100uF 400V
CY1-CY8 10nF 440VAC

D1,D2,D3,D4,D6,D7,D8,D9 UF5406
D5,D10 zener 10V 1W

U$3,U$6 IRF840
U$11,U$7 33uF 400V Solen MKP


KK1,KK4 Extruded Style Heatsink for TO-220 Mouser: 532-513102B25

Isolator Bergquist SP400-0.007-00-54 RS 169-2177

Isolatos TO-220 nylon platstic Insulator hole size M3





or see on my web page

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Old 18th June 2021, 07:13 AM   #2979
peppennino is offline peppennino  Italy
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Hi All,
As there's another similar project based on Mr. MR's MoFo:
LuFo Amp - 39w SE Class A from 28v Rail

I thought that I could ask a local transformer buider FIAT (link) to make a price for 30 pairs or more inductors with mounting frame having those features:

70mH, 5Adc and max 0,7 Ohm Rdc

It would cost 50€/pair (25€ each inductor) + shipping.
We can start a GB if interested
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Old 18th June 2021, 07:35 AM   #2980
audiodesignguide3 is offline audiodesignguide3
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Quote:
Originally Posted by peppennino View Post
Hi All,
As there's another similar project based on Mr. MR's MoFo:
LuFo Amp - 39w SE Class A from 28v Rail

I thought that I could ask a local transformer buider FIAT (link) to make a price for 30 pairs or more inductors with mounting frame having those features:

70mH, 5Adc and max 0,7 Ohm Rdc

It would cost 50€/pair (25€ each inductor) + shipping.
We can start a GB if interested
Is there a simulated data about Zout because cascode will increse this value.
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