Hi,
I had a couple of spare opa 627's, and also a spare pioneer pd-s 801, I haven't really used this machine cause I already have a modified pd-s model. In any case I thought I'd just replace the opamps in the 801 with the op627's. Trouble is I'm getting a massive dc offset of 1200-1400 mv per channel. Either the opamps are blown or perhaps something else is amiss (checked orientation of opamps, 'dot' is to pin one). The player worked fine with the 5532's in place. Normally the 627's have a low dc offset, which means that the problem lies elsewhere. Whilst I was working on the machine, I did not spot any dc coupling caps, I think it may have a dc servo instead, it must have had some kind of dc protection for the 5532's. Any ideas?
Thanks
Raja
I had a couple of spare opa 627's, and also a spare pioneer pd-s 801, I haven't really used this machine cause I already have a modified pd-s model. In any case I thought I'd just replace the opamps in the 801 with the op627's. Trouble is I'm getting a massive dc offset of 1200-1400 mv per channel. Either the opamps are blown or perhaps something else is amiss (checked orientation of opamps, 'dot' is to pin one). The player worked fine with the 5532's in place. Normally the 627's have a low dc offset, which means that the problem lies elsewhere. Whilst I was working on the machine, I did not spot any dc coupling caps, I think it may have a dc servo instead, it must have had some kind of dc protection for the 5532's. Any ideas?
Thanks
Raja
1) NE5532 have high input bias current, this results in DC voltage offset across input resistors, was not there a dc compensation for NE5532, this would make troubles with OPA627.
2) Do you have a chance to measure oscillations, if not, try to approach an AM/FM radio near to the circuit and listen if there are any whistles.
2) Do you have a chance to measure oscillations, if not, try to approach an AM/FM radio near to the circuit and listen if there are any whistles.
Hi Remco,
What cd player are you going to use?
You'll have to find out what kind of dac chip it has (current output, voltage output, differential output etc), then use either cd enhancer I, II or III or even sacd enhancer.
I used the cd enhancer II with a pioneer pd-s 703,
I wound my own 4v-4v supply and also around 7v-7v (this is regulated with 317t down to 2.78v)for the heaters of the tubes.
The 4v-4v supply is for the az1 rectifier, this is a lovely tube but it's now hard to get in some places, also the sockets aren't easy to get, I guess it gives it's own mix of sound as it's a dh rectifier....
I picked up a few 120v isolation tranformers very cheap form maplins (only around £5 each) as they've now stopped stocking these so they are reduced, I used one of these for the B+ rail.
Maplins also sell a very cheap but useable 10h choke for around £7.
So my B+ has 2 * 47 ohm res- 4.7uf cap -0.1 uf cap-choke-0.1uf cap-4.7uf cap- 680 ohm resistence-4.7uf cap-40uf cap-4.7uf cap-0.1 uf cap. All polypropylene......
If I were you I'd get someone to wind the tranny for me
100-0-100 @ 100ma
4v-4v @ around 2a
around say 8v-8v @ 0.5 - 1a
Sound is fantastic, better than any cd player I've ever heard. I also removed the 1800 pf silvered mica roll off caps, gave more detail, but the indescribable tube sound remains, kills opamps stone dead (IMHO)....
Thanks
Raja
What cd player are you going to use?
You'll have to find out what kind of dac chip it has (current output, voltage output, differential output etc), then use either cd enhancer I, II or III or even sacd enhancer.
I used the cd enhancer II with a pioneer pd-s 703,
I wound my own 4v-4v supply and also around 7v-7v (this is regulated with 317t down to 2.78v)for the heaters of the tubes.
The 4v-4v supply is for the az1 rectifier, this is a lovely tube but it's now hard to get in some places, also the sockets aren't easy to get, I guess it gives it's own mix of sound as it's a dh rectifier....
I picked up a few 120v isolation tranformers very cheap form maplins (only around £5 each) as they've now stopped stocking these so they are reduced, I used one of these for the B+ rail.
Maplins also sell a very cheap but useable 10h choke for around £7.
So my B+ has 2 * 47 ohm res- 4.7uf cap -0.1 uf cap-choke-0.1uf cap-4.7uf cap- 680 ohm resistence-4.7uf cap-40uf cap-4.7uf cap-0.1 uf cap. All polypropylene......
If I were you I'd get someone to wind the tranny for me
100-0-100 @ 100ma
4v-4v @ around 2a
around say 8v-8v @ 0.5 - 1a
Sound is fantastic, better than any cd player I've ever heard. I also removed the 1800 pf silvered mica roll off caps, gave more detail, but the indescribable tube sound remains, kills opamps stone dead (IMHO)....
Thanks
Raja
Hi Raj1,
I'm going also to use an pioneer.
But then the DV-747a wich is an SACD-DVD player.
I've tweaked it also a little bit.
Put lead-bitumen inside it, changed the output caps, removed mute-transistors, more supply capacitance, different decoupling caps, etc. (all worthwile)
This tweak is more effort to take but will be worth it, I hope.
The DAC inside is an CS-4392 with differentail output.
For me the SACD-enhancer will be better because of the less token space.
I'd like to use four or maybe six (sub+center)outputs, wich will take a lot of space when using tubes.
The sacd-enhancer seems a very simple schematic, but still got questions about it, since I don't want to ruine my player.
I see in the scheme that there is no gnd, what happens to the gnd? It is probably connected by the minus of the C-inch connector. (is it?)
The power supply bears me also with questions.
Just use an regular power supply with regulated supply rails?
Anything special to add?
Thank you.
regards,
Remco Blankesteijn.
I'm going also to use an pioneer.
But then the DV-747a wich is an SACD-DVD player.
I've tweaked it also a little bit.
Put lead-bitumen inside it, changed the output caps, removed mute-transistors, more supply capacitance, different decoupling caps, etc. (all worthwile)
This tweak is more effort to take but will be worth it, I hope.
The DAC inside is an CS-4392 with differentail output.
For me the SACD-enhancer will be better because of the less token space.
I'd like to use four or maybe six (sub+center)outputs, wich will take a lot of space when using tubes.
The sacd-enhancer seems a very simple schematic, but still got questions about it, since I don't want to ruine my player.
I see in the scheme that there is no gnd, what happens to the gnd? It is probably connected by the minus of the C-inch connector. (is it?)
The power supply bears me also with questions.
Just use an regular power supply with regulated supply rails?
Anything special to add?
Thank you.
regards,
Remco Blankesteijn.
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